Acute Toxicity Testing of Pink Salmon (Oncorhynchus gorbuscha) with the Tire Rubber-Derived Chemical 6PPD-Quinone

N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone (6PPD-quinone) is a widespread contaminant of emerging concern resulting from oxidation of 6PPD, which is an antidegradant substance added to tires. The recent identification of 6PPD-quinone as the cause of acute mortality in coho salmon has quickly motivated studies on 6PPD-quinone toxicity to other species. Subsequent findings have shown that 6PPD-quinone toxicity is highly species specific. Closely related species can differ widely in response to 6PPD-quinone from extremely sensitive to tolerant. Hence toxicity testing is currently the only way to establish whether a species exhibits 6PPD-quinone toxicity. We investigated the acute toxicity of 6PPD-quinone in pink salmon alevins (sac fry). This species has is the only Pacific salmon that so far has not been tested for 6PPD-quinone sensitivity. Fish were exposed in static water in eight treatments with initial concentrations ranging from 0.1 to 12.8 μg/L. Fish were observed for 48 h, and changes in concentrations of 6PPD-quinone were monitored throughout the experiment. No mortalities or substantial changes in behavior were recorded. Environ Toxicol Chem 2024;00:1-7. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Comparison of the performance of SWAT and hybrid M5P tree models in rainfall-runoff simulation

Stream flow forecasting is a crucial aspect of hydrology and water resource management. This study explores stream flow forecasting using two distinct models: the Soil and Water Assessment Tool (SWAT) and a hybrid M5P model tree. The research specifically targets the daily stream flow predictions at the MH Halli gauge stations, located along the Hemvati River in Karnataka, India. A 14-year dataset spanning from 2003 to 2017 is divided into two subsets for model calibration and validation. The SWAT model's performance is evaluated by comparing its predictions to observed stream flow data. Residual time series values resulting from this comparison are then resolved using the M5P model tree. The findings reveal that the hybrid M5P tree model surpasses the SWAT model in terms of various evaluation metrics, including root-mean-square error, coefficient of determination (R2), Nash-Sutcliffe efficiency, and degree of agreement (d) for the MH Halli stations. In conclusion, this study shows the effectiveness of the hybrid M5P tree model in stream flow forecasting. The research contributes valuable insights into improved water resource management and underscores the importance of selecting appropriate models based on their performance and suitability for specific hydrological forecasting tasks.

Fate and Transport of Mercury through Waterflows in a Tropical Rainforest

Knowledge gaps of mercury (Hg) biogeochemical processes in the tropical rainforest limit our understanding of the global Hg mass budget. In this study, we applied Hg stable isotope tracing techniques to quantitatively understand the Hg fate and transport during the waterflows in a tropical rainforest including open-field precipitation, throughfall, and runoff. Hg concentrations in throughfall are 1.5-2 times of the levels in open-field rainfall. However, Hg deposition contributed by throughfall and open-field rainfall is comparable due to the water interception by vegetative biomasses. Runoff from the forest shows nearly one order of magnitude lower Hg concentration than those in throughfall. In contrast to the positive Δ199Hg and Δ200Hg signatures in open-field rainfall, throughfall water exhibits nearly zero signals of Δ199Hg and Δ200Hg, while runoff shows negative Δ199Hg and Δ200Hg signals. Using a binary mixing model, Hg in throughfall and runoff is primarily derived from atmospheric Hg0 inputs, with average contributions of 65 ± 18 and 91 ± 6%, respectively. The combination of flux and isotopic modeling suggests that two-thirds of atmospheric Hg2+ input is intercepted by vegetative biomass, with the remaining atmospheric Hg2+ input captured by the forest floor. Overall, these findings shed light on simulation of Hg cycle in tropical forests.

Responses of runoff and sediment yield to slope length and gravel content of Lou soil engineering accumulation slope in Guanzhong region, Northwest China

With the economic development, a large number of engineering accumulation bodies with Lou soil as the main soil type were produced in Guanzhong area, Northwest China. We examined the characteristics of runoff and sediment yield of Lou soil accumulation bodies with earth (gravel content 0%) and earth-rock (gravel content 30%) under different rainfall intensities (1.0, 1.5, 2.0, 2.5 mm·min-1) and different slope lengths (3, 5, 6.5, 12 m) by the simulating rainfall method. The results showed that runoff rate was relatively stable when rainfall intensity was 1.0-1.5 mm·min-1, while runoff rate fluctuated obviously when rainfall intensity was 2.0-2.5 mm·min-1. The average runoff rate varied significantly across different rainfall intensities on the same slopes, and the difference of average runoff rate of the two slopes was significantly increased with rainfall intensity. Under the same rainfall intensity, the difference in runoff rate between the slope lengths of the earth-rock slope was more obvious than that of the earth slope. When the slope length was 3-6.5 m, flow velocity increased rapidly at first and then increased slowly or tended to be stable. When the slope length was 12 m, flow velocity increased significantly. In general, with the increases of rainfall intensity, inhibition effect of gravel on the average flow velocity was enhanced. When rainfall intensity was 2.5 mm·min-1, the maximum reduction in the average flow velocity of earth-rock slope was 61.5% lower than that of earth slope. When rainfall intensity was less than 2.0 mm·min-1, sediment yield rate showed a trend of gradual decline or stable change, while that under the other rainfall intensities showed a trend of rapid decline and then fluctuated sharply. The greater the rainfall intensity, the more obvious the fluctuation. There was a significant positive correlation between the average sediment yield rate and runoff parameters, with the runoff rate showing the best fitting effect. Among the factors, slope length had the highest contribution to runoff velocity and rainfall erosion, which was 51.8% and 35.5%, respectively. This study can provide scientific basis for soil and water erosion control of engineering accumulation in Lou soil areas.

Atmospheric Nitrogen Pollution Control Benefits the Coastal Environment

Nitrogen is an essential nutrient and a major limiting element for the ocean ecosystem. Since the preindustrial era, substantial amounts of nitrogen from terrestrial sources have entered the ocean via rivers, groundwater, and atmospheric deposition. China serves as a key hub in the global nitrogen cycle, but the pathways, sources, and potential mitigation strategies for land-ocean nitrogen transport are unclear. By combining the CHANS, WRF-Chem, and WNF models, we estimated that 8 million tonnes (Tg) of nitrogen was transferred into the ocean in 2017 in China, with atmospheric deposition contributing 1/3. About half variation of the offshore chlorophyll concentration was explained by atmospheric deposition. The Bohai Sea was the hot spot of nitrogen input, estimated at 214 kg N ha-1, while other areas were around 25-51 kg N ha-1. The largest contributors are agricultural systems (4 Tg, 55%), followed by domestic sewage (2 Tg, 21%). Abatement measures could reduce nitrogen export to the ocean by 43%, and mitigating ammonia and nitrogen oxide emissions accounts for 33% of this reduction, highlighting the importance of addressing air pollution in resolving ocean pollution. The cost-benefit analysis suggests the priority of nitrogen reduction in cropland and transport systems for the ocean environment.

Risk mitigation measures for pesticide runoff: How effective are they?

BACKGROUND

One of the most important sources of pesticide pollution of surface waters is runoff and erosion from agricultural fields after rainfall. This study analyses the efficacy of different risk mitigation measures to reduce pesticide runoff and erosion inputs into surface waters from arable land excluding rice fields.

RESULTS

Three groups of risk mitigation measures were quantitatively analyzed: vegetative filter strips, micro-dams in row crops and soil conservation measures. Their effectiveness was evaluated based on a meta-analysis of available experimental data using statistical methods such as classification and regression trees, and exploratory data analysis. Results confirmed the effectiveness of vegetative filter strips and micro-dams. Contrary to common assumption, the width of vegetative filter strips alone is not sufficient to predict their effectiveness. The effectiveness of soil conservation measures (especially mulch-tillage) varied widely. This was in part due to the heterogeneity of the available experimental data, probably resulting from the inconsistent implementation and the inadequate definitions of these measures.

CONCLUSION

Both vegetative filter strips and micro-dams are effective and suitable, and can therefore be recommended for quantitative assessment of environmental pesticide exposure in surface waters. However, the processes of infiltration and sedimentation in vegetative filter strips should be simulated with a mechanistic model like Vegetative Filter Strip Modeling System, VFSMOD. The reduction effect of micro-dams can be modelled by reducing the runoff curve number, e.g., in the pesticide root zone model, PRZM. Soil conservation measures are in principle promising, but further well-documented data are needed to determine under which conditions they are effective. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Investigation of 6PPD-Quinone in Rubberized Asphalt Concrete Mixtures

N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD)-quinone (6PPD-Q), a transformation byproduct of 6PPD used in tires as an antiozonant and antioxidant, was recently discovered as the chemical primarily responsible for the acute lethal toxicity of urban storm runoff to coho salmon. The asphalt concrete (AC) surface layer is the primary medium to contact 6PPD-Q immediately upon its release from tires, and the addition of recycled tire rubber (RTR) to the asphalt binder and mixture is a widely accepted practice in asphalt production. Therefore, it is urgent to understand the fate of 6PPD-Q at the asphalt concrete surface layer-water interface. This study analyzed the sorption and desorption of 6PPD-Q by compacted and crushed loose (loose particles, ∼5 mm) rubberized asphalt mixtures and their mobilization from compacted asphalt mixtures during simulated rainfall events. It should be noted that the crushed loose asphalt mixtures demonstrated the physicochemical properties of the asphalt materials, while the compacted asphalt mixtures represent in-service AC layers. Sorption of 6PPD-Q by crushed loose and compacted asphalt mixtures reached equilibrium within 12 days, with a sorption coefficient of 151.57-257.51 L/kg for compacted asphalt mixtures. Within 12 days, desorption of 6PPD-Q from crushed loose and compacted rubberized asphalt mixtures (20 g particles/L) to the double deionized (DDI) water and synthetic stormwater was 0.01-0.09 and 0.025-0.05 μg/L, respectively. Through the rainfall simulation experiments, 0.0015-0.0049 μg/L 6PPD-Q was detected in the runoff water, much lower than the lethal concentration (LC50) of 6PPD-Q of 0.095 μg/L and 308.67 μg/L for coho salmon and zebrafish larvae. Our results indicate that, while the release of 6PPD-Q from compacted rubberized asphalt mixtures is minor, the mixtures can serve as sorbents for tire-derived 6PPD-Q and retain this emerging contaminant.

Role of Phosphorus Type and Biodegradable Polymer on Phosphorus Fate and Efficacy in a Plant-Soil System

Phosphorus (P) is critical for crop production but has a high nutrient use inefficiency. Tomato was grown in soil amended with five P-sources, used as-is, or embedded within a biodegradable polymer, polyhydroxyalkanoate (PHA). Correlation analysis identified treatments that maintain plant growth, improve bioavailable soil P, and reduce P loss. Three performance classes were identified: (i) micro- and nanohydroxyapatite, which did not increase bioavailable P, plant P-uptake, or change P in runoff/leaching compared to controls; (ii) monocalcium phosphate (MCP), dicalcium phosphate (DCP), calcium pyrophosphate nanoparticles (CAP), and PHA-MCP that increased P-uptake and/or bioavailable P but also increased P loss in runoff/leaching; and (iii) PHA-DCP and PHA-CAP, where increased bioavailable P and plant P-uptake were achieved with minimal P loss in runoff/leaching. In addition to identifying treatments that maintain plant growth, increase bioavailable P, and minimize nutrient loss, correlation plots also revealed that (i) bioavailable P was a good indicator of plant P-uptake; (ii) leached P could be predicted from water solubility; and (iii) P loss through runoff versus leaching showed similar trends. This study highlights that biopolymers can promote plant P-uptake and improve bioavailable soil P, with implications for mitigating the negative environmental impacts of P loss from agricultural systems.

Porous fiber materials can alleviate the risk of farmland drought and flooding disasters and prompt crop growth

Floods and droughts on farmland seriously damage agricultural production. Porous fiber materials (PFM) made from mineral rocks have high porosity, permeability, and water retention and are utilized widely in green roofs and agricultural production. Therefore, studying the impact of PFM on the improvement of farmland is of great importance for soil and water conservation. We set 64 extreme rainfalls to analyze the impact of PFM on soil water content (SWC), runoff, nutrient loss, microorganism, and plant growth. The results showed that PFM can effectively reduce runoff and improve soil water distribution, and enhance the soil water holding capacity. Furthermore, PFM reduced the loss of nitrogen and phosphorus by 18.3% to 97% in the runoff, and the soil erosion of summer corn was more strongly influenced by lower vegetation cover, compared with winter wheat. Finally, when PFM was buried in the soil, the wheat yield increased by -6.7%-20.4%, but the corn yield in some PFM groups decreased by 5.1% to 42.5% under short-duration irrigation conditions. Our study emphasizes that the effectiveness of PFM depends mainly on the following: First, PFM with high porosity can increase soil water holding capacity and timely replenish the water lost from the surrounding soil. Second, PFM with high permeability can increase infiltration during rainfall and decrease runoff and nutrient loss, reducing the risk of farmland flooding and pollution. Finally, PFM consists of gold ions and alkali metal oxides, which can stabilize agglomerates and improve soil enzyme activity, thereby increasing the relative abundance of some microbial strains and promoting crop growth. However, when the rainfall amount was low or PFM volume was large, PFM could not store water sufficiently during rainfall, which seriously reduced the maximum saturated moisture content and water absorption performance. Meanwhile, the PFM could not release water in time and replenish the soil water deficit, which increased drought risk. In conclusion, the appropriate volume of PFM and irrigation system may enhance soil water storage capacity, minimize agricultural pollution, and promote crop production.

Long-term impacts of conservation pasture management in manuresheds on system-level microbiome and antibiotic resistance genes

Animal manure improves soil fertility and organic carbon, but long-term deposition may contribute to antibiotic resistance genes (ARGs) entering the soil-water environment. Additionally, long-term impacts of applying animal manure to soil on the soil-water microbiome, a crucial factor in soil health and fertility, are not well understood. The aim of this study is to assess: (1) impacts of long-term conservation practices on the distribution of ARGs and microbial dynamics in soil, and runoff; and (2) associations between bacterial taxa, heavy metals, soil health indicators, and ARGs in manures, soils, and surface runoff in a study following 15 years of continuous management. This management strategy consists of two conventional and three conservation systems, all receiving annual poultry litter. High throughput sequencing of the 16S ribosomal RNA was carried out on samples of cattle manure, poultry litter, soil, and runoff collected from each manureshed. In addition, four representative ARGs (intl1, sul1, ermB, and blactx-m-32) were quantified from manures, soil, and runoff using quantitative PCR. Results revealed that conventional practice increased soil ARGs, and microbial diversity compared to conservation systems. Further, ARGs were strongly correlated with each other in cattle manure and soil, but not in runoff. After 15-years of conservation practices, relationships existed between heavy metals and ARGs. In the soil, Cu, Fe and Mn were positively linked to intl1, sul1, and ermB, but trends varied in runoff. These findings were further supported by network analyses that indicated complex co-occurrence patterns between bacteria taxa, ARGs, and physicochemical parameters. Overall, this study provides system-level linkages of microbial communities, ARGs, and physicochemical conditions based on long-term conservation practices at the soil-water-animal nexus.

[Runoff Simulation and Its Response to Extreme Precipitation in the Yangtze River Basin]

Studies on runoff are crucial for the scientific allocation, utilization, and development of water resources and can provide an important basis for the prevention and control of flood and drought disaster, as well as water environmental pollution management. Affected by global warming, the frequency and intensity of extreme climate events, particularly extreme precipitation, have significantly changed in recent years, which can directly or indirectly impact runoff changes. In this study, we used the SWAT model to simulate the spatiotemporal variations in runoff in the Yangtze River Basin from 1965 to 2019 and analyzed the response of runoff to precipitation under extreme conditions. The results showed that the changes in total runoff in the Yangtze River Basin were not significantly different from 1965 to 2019. The total runoff and the mid-lower runoff in the basin experienced four stages of "dry-wet-dry-wet." Simulations revealed that under the 50-year extreme precipitation event, the increase in daily average runoff was 6200%, 21%, and 15% for the typical sub-basins of the upper, middle, and lower reaches of the Yangtze River, respectively. Additionally, the increase in monthly and annual average runoff was 355%, 5%, and 1.3% and 78%, 1%, and 0.24%, for upper, middle, and lower reaches of the Yangtze River, respectively. Moreover, under the 100-year extreme precipitation, the average daily runoff increasing rates were 8000%, 25%, and 17% for upper, middle, and lower reaches of the Yangtze River, respectively, compared to the monthly increase of 437%, 7%, and 1.5% and annual increase of 96%, 1.2%, and 0.28%, respectively. Our findings may improve the understanding of hydrological responses to climate change and provide valuable inferences to decision-makers and water managers for better allocation and management of water resources.

[Estimation of Cropland Nitrogen Runoff Loss Loads in the Yangtze River Basin Based on the Machine Learning Approaches]

A quantitative understanding of cropland nitrogen (N) runoff loss is critical for developing efficient N pollution control strategies. Using correlation analysis, a structural equation model, variance decomposition, and machine learning methods, this study identified the primary influencing factors of total N (TN) runoff loss from uplands (n=570) and paddy (n=434) fields in the Yangtze River Basin (YRB) and then developed a machine learning-based prediction model to quantify cropland N runoff loss load. The results indicated that runoff depth, soil N content, and fertilizer addition rate were the major influencing factors of TN runoff loss from uplands, whereas TN runoff loss rate from paddy fields was mainly regulated by runoff depth and fertilizer addition rate. Among the four used machine learning methods, the prediction models based on the random forest algorithm presented the highest accuracy (R²=0.65-0.94) for predicting upland and paddy field TN runoff loss rates. The random forest algorithm based model estimated a total cropland TN loss load in the YRB of 0.47 Tg·a^-1 (upland:0.25 Tg·a^-1; paddy field:0.22 Tg·a^-1) in 2013, with 58% of TN runoff loss load derived from the midstream and downstream regions. The models predicted that TN runoff loss loads from croplands in YRB would decrease by 2.4%-9.3% for five scenarios, with higher TN load reductions occurring from scenarios with decreased runoff amounts. To mitigate cropland N nonpoint source pollution in YRB, it is essential to integrate efficient water, fertilizer, and soil nutrient managements as well as to consider the midstream and downstream regions as the high priority area. The machine learning-based modeling method developed in this study overcame the difficulty of identifying the functional relationships between cropland TN loss rate and multiple influencing factors in developing relevant prediction models, providing a reliable method for estimating regional and watershed cropland TN loss load.

Biocrusts intensify water redistribution and improve water availability to dryland vegetation: insights from a spatially-explicit ecohydrological model

Biocrusts are ecosystem engineers in drylands and structure the landscape through their ecohydrological effects. They regulate soil infiltration and evaporation but also surface water redistribution, providing important resources for vascular vegetation. Spatially-explicit ecohydrological models are useful tools to explore such ecohydrological mechanisms, but biocrusts have rarely been included in them. We contribute to closing this gap and assess how biocrusts shape spatio-temporal water fluxes and availability in a dryland landscape and how landscape hydrology is affected by climate-change induced shifts in the biocrust community. We extended the spatially-explicit, process-based ecohydrological dryland model EcoHyD by a biocrust layer which modifies water in- and outputs from the soil and affects surface runoff. The model was parameterized for a dryland hillslope in South-East Spain using field and literature data. We assessed the effect of biocrusts on landscape-scale soil moisture distribution, plant-available water and the hydrological processes behind it. To quantify the biocrust effects, we ran the model with and without biocrusts for a wet and dry year. Finally, we compared the effect of incipient and well-developed cyanobacteria- and lichen biocrusts on surface hydrology to evaluate possible paths forward if biocrust communities change due to climate change. Our model reproduced the runoff source-sink patterns typical of the landscape. The spatial differentiation of soil moisture in deeper layers matched the observed distribution of vascular vegetation. Biocrusts in the model led to higher water availability overall and in vegetated areas of the landscape and that this positive effect in part also held for a dry year. Compared to bare soil and incipient biocrusts, well-developed biocrusts protected the soil from evaporation thus preserving soil moisture despite lower infiltration while at the same time redistributing water toward downhill vegetation. Biocrust cover is vital for water redistribution and plant-available water but potential changes of biocrust composition and cover can reduce their ability of being a water source and sustaining dryland vegetation. The process-based model used in this study is a promising tool to further quantify and assess long-term scenarios of climate change and how it affects ecohydrological feedbacks that shape and stabilize dryland landscapes.

South American Dry Chaco rangelands: Positive effects of cattle trampling and transit on ecohydrological functioning

Livestock production in drylands requires consideration of the ecological applications of ecohydrological redistribution of water. Intensive cattle trampling and the associated increase of surface runoff are common concerns for rangeland productivity and sustainability. Here, we highlight a regional livestock production system in which cattle trails and trampling surrounding an artificial impoundment are purposely managed to enhance redistribution and availability of water for cattle drinking. Based on literature synthesis and field measurements, we first describe cattle production systems and surface water redistribution in the Dry Chaco rangelands of South America, and then develop a conceptual framework to synthesize the ecohydrological impacts of livestock production on these ecosystems. Critical to this framework is the pioshere-a degraded overgrazed and overtrampled area where vegetation has difficulties growing, usually close to the water points. The Dry Chaco rangelands have three key distinctive characteristics associated with the flat sedimentary environment lacking fresh groundwater and the very extensive ranching conditions: (1) cattle drinking water is provided by artificial impoundments filled by runoff, (2) heavy trampling around the impoundment and its adjacent areas generates a piosphere that favors runoff toward the impoundment, and (3) the impoundment, piosphere, and extensive forage areas are hydrologically connected with a network of cattle trails. We propose an ecohydrological framework where cattle transit and trampling alter the natural water circulation of these ecosystems, affecting small fractions of the landscape through increased runoff (compaction in piosphere and trails), surface connectivity (convergence of trails to piosphere to impoundment), and ponding (compaction of the impoundment floor) that operate together making water harvesting and storage possible. These effects have likely generated a positive water feedback on the expansion of livestock in the region with a relatively low impact on forage production. We highlight the role of livestock transit as a geomorphological agent capable of reshaping the hydrology of flat sedimentary rangelands in ways that can be managed positively for sustainable ranching systems. We suggest that the Dry Chaco offers an alternative paradigm for rangelands in which cattle trampling may contribute to sustainable seminatural production systems with implications for other dry and flat rangelands of the world.

Are sustainable drainage systems (SuDS) effective at retaining dissolved trace elements?

Sustainable drainage systems (SuDS) are increasingly deployed to mitigate against increased trace element contaminant loads associated with urban and road runoff. However, there is a lack of research on their capabilities in removing these trace elements, particularly from the dissolved phase. Water samples were taken, following various rainfall events, from three different SuDS in Devon; one wetland pond adjacent to a busy dual carriageway, a new SuDS serving a housing estate and an established SuDS draining a mixed housing/light industrial area. A total of 15 elements were studied over the course of six rain events including the first flush of runoff. Removal rates varied within and between rain events as well as between types of SuDS. Although there was a general (modest) removal of dissolved elements within any given SuDS, this was not the case for all of the elements studied. Highest observed element concentrations entering the SuDS occurred at the onset of a rain event (first flush), the intensity of which, was related to the antecedent dry period. During high flows associated with intense rainfall, the SuDS could also act as a source of trace elements associated with fine particulates (e.g. lead) owing to resuspension of fine particulate material. Mature ponds with an abundance of macrophytes help retain solids and particulate metals, however poor maintenance leading to successional growth of shrubs and trees, reduces the efficiency of metal removal. This study highlighted the importance of long-term management planning to be included within any SuDs scheme.

Calculating the Environmental Impacts of Low-Impact Development Using Long-Term Hydrologic Impact Assessment: A Review of Model Applications

Low-impact development (LID) is a planning and design strategy that addresses water quality and quantity while providing co-benefits in the urban and suburban landscape. The Long-Term Hydrologic Impact Assessment (L-THIA) model estimates runoff and pollutant loadings using simple inputs of land use, soil type, and climatic data for the watershed-scale analysis of average annual runoff based on curve number analysis. Using Scopus, Web of Science, and Google Scholar, we screened 303 articles that included the search term "L-THIA", identifying 47 where L-THIA was used as the primary research method. After review, articles were categorized on the basis of the primary purpose of the use of L-THIA, including site screening, future scenarios and long-term impacts, site planning and design, economic impacts, model verification and calibration, and broader applications including policy development or flood mitigation. A growing body of research documents the use of L-THIA models across landscapes in applications such as the simulations of pollutant loadings for land use change scenarios and the evaluation of designs and cost-effectiveness. While the existing literature demonstrates that L-THIA models are a useful tool, future directions should include more innovative applications such as intentional community engagement and a focus on equity, climate change impacts, and the return on investment and performance of LID practices to address gaps in knowledge.

Epilithic biofilms, POCIS, and water samples as complementary sources of information for a more comprehensive view of aquatic contamination by pesticides and pharmaceuticals in southern Brazil

Spatial-temporal monitoring of the presence of pesticides and pharmaceuticals in water requires rigor in the choice of matrix to be analyzed. The use of matrices, isolated or combined, may better represent the real state of contamination. In this sense, the present work contrasted the effectiveness of using epilithic biofilms with active water sampling and with a passive sampler-POCIS. A watershed representative of South American agriculture was monitored. Nine sites with different rural anthropic pressures (natural forest, intensive use of pesticides, and animal waste), and urban areas without sewage treatment, were monitored. Water and epilithic biofilms were collected during periods of intensive pesticide and animal waste application. After the harvest of the spring/summer crop, a period of low agrochemical input, the presence of pesticides and pharmaceuticals was monitored using the POCIS and epilithic biofilms. The spot water sampling leads to underestimation of the level of contamination of water resources as it does not allow discrimination of different anthropic pressures in rural areas. The use of endogenous epilithic biofilms as a matrix for the analysis of pesticides and pharmaceuticals is a viable and highly recommended alternative to diagnose the health of water sources, especially if associated with the use of POCIS.

Survival, mobilization, and transport of Escherichia coli from sheep faeces

AIMS

This study looked at the survival, mobilization, and transport of Escherichia coli from sheep faeces over an extended period, which was then repeated for all four seasons.

METHODS AND RESULTS

Rain simulation was used to measure E. coli mobilization directly from faecal pats and subsequent transport across a soil surface. The rain simulation experiments were conducted over the same 90-day period and for the four seasons as per the survival experiments conducted to determine E. coli survival in faecal pats. The survival experiments demonstrated up to three orders of magnitude increase of E. coli in sheep faeces. Peak E. coli concentrations in the faeces were observed on Day 2 through to Day 30, with no significant effect of seasons or weather patterns. The E. coli concentrations in the runoff followed the survival pattern of E. coli concentrations in the faeces.

CONCLUSIONS

There was a statistically significant relationship between the E. coli concentrations in the faeces and the runoff.

SIGNIFICANCE AND IMPACT OF STUDY

The data generated on the relationship between Escherichia coli concentrations in the faeces and in the runoff can support the development of runoff risk models for sheep grazing pastureland to support catchment modelling, land use decisions, and public health.

Untapped policy avenues to protect coral reef ecosystems

Coral reefs are experiencing severe decline, and urgent action is required at local and global scales to curb ecosystem loss. Establishing new regulations to protect corals, however, can be time consuming and costly, and it is therefore necessary to leverage existing legal instruments, such as policies originally designed to address terrestrial rather than marine activities, to prevent coral reef degradation. Focusing on the United States, but drawing on successful examples worldwide, we present actionable pathways to increase coral protections under legislation that was originally designed to advance clean freshwater, safe drinking water, and emergency management. We identify specific legal policies and procedures (e.g., industrial permit limits, nonpoint source management incentives, and floodplain restoration programs) that can curb coral reef pollution and can be extended to other countries with similar regulations in place. Coral reef practitioners should consider a broad array of currently underused, actionable, and intersecting environmental policies that can be applied to mitigate coral stress.

Per- and Poly-Fluoroalkyl Substances in Runoff and Leaching from AFFF-Contaminated Soils: a Rainfall Simulation Study

The mobilization and transport of per- and poly-fluoroalkyl substances (PFASs) via surface runoff (runoff) from aqueous film-forming foam (AFFF)-contaminated soils during rainfall, flooding, or irrigation has not been thoroughly evaluated, and the effectiveness of carbonaceous sorbents in limiting PFASs in runoff is similarly unquantified. Here, laboratory-scale rainfall simulations evaluate PFAS losses in runoff and in leaching to groundwater (leachate) from AFFF-contaminated soils varying in texture, PFAS composition and concentration, and remediation treatment. Leaching dominated PFAS losses in soils with a concentration of ∑PFAS = 0.2-2 mg/kg. However, with higher soil PFAS concentrations (∑PFAS = 31 mg/kg), leachate volumes were negligible and runoff dominated losses. The concentration and variety of PFASs were far greater in leachates regardless of the initial concentrations in soil. Losses of PFASs were dependent on the C-chain length for leachates and more on the initial concentration in soil for runoff. Suspended materials did not meaningfully contribute to runoff losses. While concentrations of most PFASs declined significantly after the first rainfall event, desorption and transport in both runoff and leachates persisted over several rainfall events. Finally, results showed that sorption to AC mostly occurred during, not prior to, rainfall events and that 1% w/w AC substantially reduced losses in runoff and leachates from all soils.

Acute Toxicity Testing of the Tire Rubber-Derived Chemical 6PPD-quinone on Atlantic Salmon (Salmo salar) and Brown Trout (Salmo trutta)

Recent identification of 6PPD-quinone as the chemical causing acute toxicity in coho salmon has led to substantial concern regarding the toxicity of this contaminant for other aquatic species. Environmental occurrence of 6PPD-quinone is probably high, because it is an oxidation product of a common tire rubber additive. Research on 6PPD-quinone toxicity in fish has revealed a rather unusual pattern, with closely related species exhibiting responses ranging from extreme sensitivity to no effect. Of 11 previously studied fish species, 6PPD-quinone was toxic to four. The species-specific toxicity of 6PPD-quinone complicates urgently needed environmental risk assessment. We investigated the acute toxicity of 6PPD-quinone in Atlantic salmon and brown trout alevins (sac fry). These species have previously not been tested for sensitivity to 6PPD-quinone. The fish were exposed in static conditions in eight treatments with initial concentrations ranging from 0.095 to 12.16 µg/L. Fish were observed for 48 h, and changes in concentrations of 6PPD-quinone were monitored throughout the experiment. No mortalities or substantial changes in behavior were recorded in either Atlantic salmon or brown trout. This provides an important first step in assessing effects of 6PPD-quinone on these economically and culturally highly important species. Environ Toxicol Chem 2022;41:3041-3045. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

[Effects of gravel content on runoff and sediment yield on Lou soil engineering accumulation slopes under simulated rainfall conditions.]

To investigate the effects of gravel content on runoff and sediment yield on Lou soil accumulation slopes, we conducted indoor simulation rainfall experiments and examined the characteristics of runoff and sediment yield on accumulation slopes with five gravel contents (10%, 20%, 30%, 40%, 50%) under four rainfall intensities (1.0, 1.5, 2.0, 2.5 mm·min^-1), with a no gravels slope as control. The average runoff rate under different test conditions ranged from 2.18 to 13.07 L·min^-1. The average runoff rate was the maximum under the gravel content of 10% (or 20%) and the minimum under the 50% gravel content. The average flow velocity ranged from 0.06 to 0.22 m·s^-1. The variation of flow velocity was complex. The smaller the gravel content, the larger the range of variation and the coefficient of variation. The average flow velocity reached the maximum when the gravel content was 10%. The presence of gravel effectively inhibited the sediment yield, and the sediment reduction benefit reached 84.2%. The rainfall intensity had more influence on the average sediment yield rate than gravel content. Results of partial correlation analysis showed that gravel content was significantly negatively correlated with the ave-rage runoff rate, the average flow velocity, and the average sediment yield rate. The relationships between the ave-rage sediment yield and the average runoff rate, the average flow velocity, and their interaction were all extremely significant linear functions, with the strongest relationship between the average sediment yield and the average runoff rate. This study could provide references for the control of soil erosion and the establishment of erosion models for engineering accumulations in Lou soil areas.

Distinguishing Direct Human-Driven Effects on the Global Terrestrial Water Cycle

Population growth is increasing the pressure on water resource availability. For useful assessment and planning for societal water availability impacts, it is imperative to disentangle the direct influences of human activities in the landscape from external climate-driven influences on water flows and their variation and change. In this study we used the water balance model, a gridded global hydrological model, to quantify and distinguish human-driven change components, modified by interventions such as dams, reservoirs, and water withdrawals for irrigation, industry, and households, from climate-driven change components on four key water balance variables in the terrestrial hydrological system (evapotranspiration, runoff, soil moisture, storage change). We also analyzed emergent effect patterns in and across different parts of the world, facilitating exploration of spatial variability and regional patterns on multiple spatial scales, from pixel to global, including previously uninvestigated parts of the world. Our results show that human activities drive changes in all hydrological variables, with different magnitudes and directions depending on geographical location. The differences between model scenarios with and without human activities were largest in regions with the highest population densities. In such regions, which also have relatively large numbers of dams for irrigation, water largely tends to be removed from storage and go to feed increased runoff and evapotranspiration fluxes. Our analysis considers a more complete set of hydrological variables than previous studies and can guide further research and management planning for future hydrological and water availability trends, including in relatively data-poor parts of the world.

[Characteristics of runoff and infiltration processes on slope with intergrown biocrusts and herbs]

Biocrusts and herbs coexist in arid and semi-arid areas, playing an important role in soil and water conservation. However, the combined effects of biocrusts and herbs on process and mechanism of runoff and infiltration on slope are still unclear. In this study, simulated rainfall experiments with four treatments, including bare soil, biocrusts, Stipa bungeana and S. bungeana+biocrusts, were designed to investigate runoff, infiltration process and hydrodynamic characteristics of herbs and biocrusts on slope. The results showed that the runoff under the two treatments with biocrusts was stable. The total runoff of four treatments was in the following order: biocrusts > S. bungeana+biocrusts > bare soil > S. bungeana, indicating that biocrusts could inhibit soil infiltration and S. bungeana could promote soil infiltration. At soil depths of 16 cm and 24 cm, the cumulative infiltration of biocrusts treatment was significantly less than that of S. bungeana+biocrusts treatment, suggesting that with the increases of soil depth, S. bungeana reduced the negative effect of biocrusts on soil infiltration. The Froude number was greater than 1 under bare soil and less than 1 under other treatments, which was subcritical flow. Compared with the runoff kinetic energy of the bare soil treatment, the treatments of biocrusts, S. bungeana, and S. bungeana+biocrusts were reduced by 83.3%, 59.5%, and 88.1%, respectively. The variations of hydrodynamic parameters indicated that the role of biocrusts is greater than S. bungeana in regulating runoff.

Removal of stormwater dissolved organic nitrogen through biotransformation using activated carbon

Conventional bioretention systems are not effectively designed to remove stormwater dissolved organic nitrogen (DON). Biotransformation study on five organic nitrogenous compounds with different values for adsorption on coal activated carbon (AC) and bioavailability revealed that adsorption is a greater controlling factor for ammonification than bioavailability. This study also showed three apparent benefits: enhancement of the ammonification rate, ammonification of the bio-recalcitrant organic nitrogenous compounds, for example, pyrrole, and bio-regeneration of the adsorbent (coal AC). Low temperature (4°C) did not impact ammonification of leucine at a velocity of 34 cm/h, but negatively affected it at 61 cm/h. It was also observed that bed media height > 30 cm would not appreciably increase ammonification. Under intermittent wetting/draining conditions, the DON removal efficiency was more than 90%, indicating that DON was successfully removed through concurrent adsorption/ammonification, although generated ammonium in the effluent must be properly addressed. PRACTITIONER POINTS: Coal activated carbon appears a better material for DON ammonification compared with charcoal and quartz sand. A temperature as low as 4°C may not adversely impact DON ammonification at a velocity of 34 cm/h or less. A bed media depth of 30 cm is considered as adequate to promote DON ammonification. A larger depth may not be expected to improve ammonification. Ammonification of the bio-recalcitrant organic nitrogenous compounds, for example, pyrrole, and bio-regeneration of the adsorbent, for example, coal activated carbon, may be achieved.

Influences of Shifted Vegetation Phenology on Runoff Across a Hydroclimatic Gradient

Climate warming has changed vegetation phenology, and the phenology-associated impacts on terrestrial water fluxes remain largely unquantified. The impacts are linked to plant adjustments and responses to climate change and can be different in different hydroclimatic regions. Based on remote sensing data and observed river runoff of hydrological station from six river basins across a hydroclimatic gradient from northeast to southwest in China, the relative contributions of the vegetation (including spring and autumn phenology, growing season length (GSL), and gross primary productivity) and climatic factors affecting the river runoffs over 1982-2015 were investigated by applying gray relational analysis (GRA). We found that the average GSLs in humid regions (190-241 days) were longer than that in semi-humid regions (186-192 days), and the average GSLs were consistently extended by 4.8-13.9 days in 1982-2015 period in six river basins. The extensions were mainly linked to the delayed autumn phenology in the humid regions and to advanced spring phenology in the semi-humid regions. Across all river basins, the GRA results showed that precipitation (r = 0.74) and soil moisture (r = 0.73) determine the river runoffs, and the vegetation factors (VFs) especially the vegetation phenology also affected the river runoffs (spring phenology: r = 0.66; GSL: r = 0.61; autumn phenology: r = 0.59), even larger than the contribution from temperature (r = 0.57), but its relative importance is climatic region-dependent. Interestingly, the spring phenology is the main VF in the humid region for runoffs reduction, while both spring and autumn growth phenology are the main VFs in the semi-humid region, because large autumn phenology delay and less water supply capacity in spring amplify the effect of advanced spring phenology. This article reveals diverse linkages between climatic and VFs, and runoff in different hydroclimatic regions, and provides insights that vegetation phenology influences the ecohydrology process largely depending on the local hydroclimatic conditions, which improve our understanding of terrestrial hydrological responses to climate change.

Spatial distribution and temporal variation of polycyclic aromatic hydrocarbons in runoff and surface water

This study aims to investigate the spatial distribution of and temporal variation in the phase distribution, emission sources, and ecological risk of polycyclic aromatic hydrocarbons (PAHs) in runoff and in surface water mixed with runoff discharge. The samples were collected at semi-rural, residential, and industrial sites in Ulsan, South Korea, from April to October 2016. The industrial site had the highest PAH concentrations in the runoff and surface water due to the higher PAH levels found in the surrounding environmental media. The PAH phase distributions were relatively similar between the sampling sites, with dissolved PAHs (2- to 4-ring species) dominant. In July, the PAHs in the surface water were more commonly found in the dissolved phase due to the higher water temperature and dissolved organic carbon concentration. The emission sources for the PAHs were identified using principal component analysis (PCA), a dimension reduction technique, and the k-nearest neighbor (KNN) classifier, a supervised learning algorithm. It was determined that the PAHs in the runoff and surface water were likely to share similar petrogenic and pyrolysis sources for most of the sampling periods. The ecological risk of the surface water was 1.5-4.5 times lower after being mixed with runoff water, mainly due to dilution effects. The ecological risk for surface water was highest in July because of the higher PAH concentrations. This study contributes to the understanding of PAHs in runoff and in surface water affected by runoff discharge.

[Impacts of human activity on Bayin River runoff as revealed by tree rings in Qaidam Basin, China]

Evaluating the impacts of human activity on river runoff has important implications for regional water resource management. Here, we used seven tree-ring width chronologies to establish a regional mean tree-ring width chronology from the northern mountain of Delingha, Qaidam Basin. We conducted the correlation, moving correlation and regression analysis of regional mean tree-ring width chronology with runoff data from Bayin River gauge station. Then, we stimulated the June runoff of Bayin River from 1956 to 2002. The results showed that the highest correlation coefficient was found for June runoff (r=0.63, P<0.01), and their moving correlation coefficient decreased after 1986. Based on the stable relationship between tree-ring width chronology and the June runoff during 1956-1986, we built the reconstruction function, which was explained 50.8% of observed runoff. The stimulated runoff during 1987 to 2002 was significantly higher than the observed runoff (3.01 m³·s^-1, P<0.001). These results indicated that human activity from the upper river had significant impacts on Bayin River runoff. Human activity should be considered as an important factor to protect security of sustainable water resource utilization for future water resource development and utilization in Bayin River region.

Freeze tolerance influenced forest cover and hydrology during the Pennsylvanian

The distribution of forest cover alters Earth surface mass and energy exchange and is controlled by physiology, which determines plant environmental limits. Ancient plant physiology, therefore, likely affected vegetation-climate feedbacks. We combine climate modeling and ecosystem-process modeling to simulate arboreal vegetation in the late Paleozoic ice age. Using GENESIS V3 global climate model simulations, varying pCO₂, pO₂, and ice extent for the Pennsylvanian, and fossil-derived leaf C:N, maximum stomatal conductance, and specific conductivity for several major Carboniferous plant groups, we simulated global ecosystem processes at a 2° resolution with Paleo-BGC. Based on leaf water constraints, Pangaea could have supported widespread arboreal plant growth and forest cover. However, these models do not account for the impacts of freezing on plants. According to our interpretation, freezing would have affected plants in 59% of unglaciated land during peak glacial periods and 73% during interglacials, when more high-latitude land was unglaciated. Comparing forest cover, minimum temperatures, and paleo-locations of Pennsylvanian-aged plant fossils from the Paleobiology Database supports restriction of forest extent due to freezing. Many genera were limited to unglaciated land where temperatures remained above -4 °C. Freeze-intolerance of Pennsylvanian arboreal vegetation had the potential to alter surface runoff, silicate weathering, CO₂ levels, and climate forcing. As a bounding case, we assume total plant mortality at -4 °C and estimate that contracting forest cover increased net global surface runoff by up to 6.1%. Repeated freezing likely influenced freeze- and drought-tolerance evolution in lineages like the coniferophytes, which became increasingly dominant in the Permian and early Mesozoic.

Modeling Terrestrial Dissolved Organic Carbon Loading to Western Arctic Rivers

The mobilization and land-to-ocean transfer of dissolved organic carbon (DOC) in Arctic watersheds is intricately linked with the region's climate and water cycle, and furthermore at risk of changes from climate warming and associated impacts. This study quantifies model-simulated estimates of runoff, surface and active layer leachate DOC concentrations and loadings to western Arctic rivers, specifically for basins that drain into coastal waters between and including the Yukon and Mackenzie Rivers. Model validation leverages data from other field measurements, synthesis studies, and modeling efforts. The simulations effectively quantify DOC leaching in surface and subsurface runoff and broadly capture the seasonal cycle in DOC concentration and mass loadings reported from other studies that use river-based measurements. A marked east-west gradient in simulated spring and summer DOC concentrations of 24 drainage basins on the North Slope of Alaska is captured by the modeling, consistent with independent data derived from river sampling. Simulated loadings for the Mackenzie and Yukon show reasonable agreement with estimates of DOC export for annual totals and four of the six seasonal comparisons. Nearly equivalent loading occurs to rivers which drain north to the Beaufort Sea and west to the Bering and Chukchi Seas. The modeling framework provides a basis for understanding carbon export to coastal waters and for assessing impacts of hydrological cycle intensification and permafrost thaw with ongoing warming in the Arctic.

Responses of Runoff and Soil Loss on Slopes to Land Use Management and Rainfall Characteristics in Northern China

Soil conservation measures are widely used to control soil erosion and sediment loss; however, their proper usage relies on a deep understanding of the responses of runoff and sediment loss to land management and rainfall characteristics. In the present study, a long-term (2014–2020) monitored dataset derived from ten runoff plots in the upstream catchment of the Miyun Reservoir in Beijing, China, was used to study runoff and sediment loss responses to land use management and rainfall characteristics. The study results show that plots with no soil conservation measures had the highest runoff depth of 75 mm and suffered the highest sediment loss, at a rate of 3200 t km⁻² yr⁻¹. The terraced and vegetated plots generated lower runoff depths, with soil loss rates less than 213.0 t km⁻² yr⁻¹. With the exception of the contour tillage plots on steep slopes, the vegetation and engineering measures can efficiently reduce runoff and sediment loss, with both runoff and sediment reduction efficiencies higher than 76%. Statistical analyses indicate that, on the plots of bare soil and cultivation without soil conservation measures, runoff and sediment loss were mainly affected by the maximum 30 min rainfall intensity. However, on the plots with soil conservation measures, they were mainly determined by rainfall amount and duration. The sediment loss rate can be well fitted with the runoff depth using a power function. Based on the analyses, water-saving soil conservation measures are recommended for the study area. In addition, the size of terraces should be reconsidered on gentle slopes, and the coverage of forest, shrubs, and grass on slopes should be reduced, thus allowing for more surface runoff generation to ensure drinking water safety. In general, for the study area, soil conservation measures are required on the bare soil and cultivated slopes.

Manure derived nutrients alter microbial community composition and increase the presence of potential pathogens in freshwater sediment

AIM

To determine the impact of an acute, pulse disturbance of nutrients from manure on freshwater sediment microbiomes in an experimental system.

METHODS AND RESULTS

A controlled freshwater mesocosm experiment was designed to compare the effect of disturbance from nutrients derived from sterile manure (SM), disturbance from equivalent concentrations of laboratory-derived nutrients, and a nondisturbed control on freshwater sediment microbial community composition and function using 16S rRNA amplicon sequencing. Sediment microbiomes impacted by nutrients from SM showed no sign of compositional recovery after 28 days but those impacted by laboratory-derived chemicals lead to a new steady-state (p < 0.05). Carbon and nitrate sources within disturbed mesocosms were the primary drivers of altered microbial community composition. Additionally, multiple potential pathogens (based on exact sequence matching at the species level) were enriched in mesocosms treated with SM.

CONCLUSIONS

Nutrient disturbance from SM, in the absence of the manure microbial community, alters the microbiome of sediments without recovery after 28 days and enriches potential pathogens.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results suggest manure land application practices should be re-evaluated to account for impact of nutrient disturbance on environmental microbiomes in addition to the impact of the manure microbial community.

Seasonal Dynamics Are the Major Driver of Microbial Diversity and Composition in Intensive Freshwater Aquaculture

Aquaculture facilities such as fishponds are one of the most anthropogenically impacted freshwater ecosystems. The high fish biomass reared in aquaculture is associated with an intensive input into the water of fish-feed and fish excrements. This nutrients load may affect the microbial community in the water, which in turn can impact the fish health. To determine to what extent aquaculture practices and natural seasonal cycles affect the microbial populations, we characterized the microbiome of an inter-connected aquaculture system at monthly resolution, over 3 years. The system comprised two fishponds, where fish are grown, and an operational water reservoir in which fish are not actively stocked. Clear natural seasonal cycles of temperature and inorganic nutrients concentration, as well as recurring cyanobacterial blooms during summer, were observed in both the fishponds and the reservoir. The structure of the aquatic bacterial communities in the system, characterized using 16S rRNA sequencing, was explained primarily by the natural seasonality, whereas aquaculture-related parameters had only a minor explanatory power. However, the cyanobacterial blooms were characterized by different cyanobacterial clades dominating at each fishpond, possibly in response to distinct nitrogen and phosphate ratios. In turn, nutrient ratios may have been affected by the magnitude of fish feed input. Taken together, our results show that, even in strongly anthropogenically impacted aquatic ecosystems, the structure of bacterial communities is mainly driven by the natural seasonality, with more subtle effects of aquaculture-related factors.

Catchment Runoff in Industrial Areas Exports Legacy Pollutant Zinc from the Topsoil Rather than Geogenic Zn

In highly industrialized, densely populated parts of Central Europe, mobilization of legacy Zn pollution from forest ecosystems may negatively affect the quality of water resources. To test this hypothesis, we determined the ⁶⁶Zn/⁶⁴Zn isotope ratios of 15 Zn reservoirs and fluxes in an acidified, spruce die-back affected mountain-slope catchment in northern Czech Republic. The δ⁶⁶Zn values of precipitation, organic horizon, and runoff were statistically indistinguishable. In contrast, δ⁶⁶Zn values of bedrock orthogneiss and mineral soil were significantly different from δ⁶⁶Zn values of runoff. The magnitude of within-site Zn isotope fractionations appeared to be relatively small. Despite the large potential source of Zn in bedrock, runoff exported mostly young pollutant Zn that had been temporarily stored in the organic horizon. This conclusion was corroborated by comparing Zn input-output mass balances in the polluted northern catchment and in a relatively unpolluted catchment situated 250 km to the south. Seven-times higher Zn export via runoff at the northern site was controlled by a combination of 10-times higher atmospheric Zn input and five-times higher DOC leaching, compared to the southern site. In industrial areas, atmospherically deposited Zn is leached from headwater catchments in a direct analogy to leaching of highly toxic pollutant Pb.

[Effects of Different Land Use Practices on Nitrogen Loss from Runoff During Rainfall Events]

To understand the effect of nitrogen from runoff during rainfall events for different land uses, sub-catchments A and B in the small Shipanqiu watershed in Zhong County, Chongqing-which were managed using different land use practices-were taken as research objects. Runoff flow and nitrogen levels at the outlet of the catchment were monitored. Sub-catchment A is an agroforestry-water complex and sub-catchment B is the site of traditional agriculture. EMC was used to evaluate the average concentration of runoff nitrogen during rainfall events, and the effect of this runoff nitrogen on the small watershed with different land use systems was analyzed. The results showed that the TN concentration in catchment B (1.37-15.17 mg·L^-1) > catchment A (0.84-9.28 mg·L^-1); the ratio of the first peak to the second peak in catchment A was 62%, which was far less than the 97% in catchment B; the average DN/TN values were 69% and 75% in catchments A and B, respectively; and the average NN/DN values were 67% and 80% in catchments A and B, respectively. The different land use practices have significant impacts on nitrogen loss. Compared with the catchment where traditional agricultural practices were followed, the agroforestry-water complex catchment effectively reduced the loss of nitrogen and decreased the first TN peak value and DN/TN and NN/DN values. This study provides a scientific basis for the prevention and control of non-point source pollution in small watersheds in the area of the Three Gorges Reservoir.

Activated carbon column adsorption of compounds that mimic urban stormwater dissolved organic nitrogen

Nutrients mobilized by stormwater can exacerbate eutrophication in receiving waters. While bioretention systems are increasingly employed to improve stormwater quality, they do not normally incorporate design attributes for removal of dissolved organic nitrogen (DON). Thus, the current study concentrated on continuous column adsorption of stormwater DON using a media mixture of coal activated carbon and quartz sand. Adsorption of eight model organic nitrogenous compounds was studied and only pyrrole showed an appreciable adsorption performance; other organic nitrogen compounds were weakly adsorbed. The breakthrough depth for pyrrole was 88 m (equivalent to 4.4 m simulated rainfall depth), at a superficial velocity of 61 cm/hr and influent DON concentration of 1 mg N/L. Subsequent experiments revealed that adsorption of pyrrole was minimally affected by superficial velocity, such that its DON removal efficiency was greater than 91% for all tested superficial velocities (7-489 cm/hr). Accordingly, adsorption processes may be employed for removing stormwater DON fractions behaving similarly to pyrrole; data suggest DON removal initially at greater than 95%, gradually falling to 30% through 25 years of service. PRACTITIONER POINTS: Adsorption of eight different organic nitrogenous compounds onto coal-based activated carbon was investigated. Amino acids and an amino sugar were weakly adsorbed onto the activated carbon. Pyrrole, a moderately hydrophobic heterocyclic organic nitrogen compound was effectively adsorbed. A 30-cm depth was considered as adequate for removal of pyrrole and compounds that would similarly adsorb. Evidence of biological ammonification was present in all studies except for pyrrole.

Urban stormwater characterization, control, and treatment

This review summarizes over 280 studies published in 2019 related to the characterization, control, and management of urban stormwater runoff. A summary of quantity and quality concerns is provided in the first section of the review, serving as the foundation for the following sections which focus on the control and treatment of stormwater runoff. Finally, the impact of stormwater control devices at the watershed scale is discussed. Each section provides a self-contained overview of the 2019 literature, common themes, and future work. Several themes emerged from the 2019 literature including exploration of substrate amendments for improved water quality effluent from stormwater controls, the continued study of the role of vegetation in green infrastructure practices, and a call to action for the development of new models which generate reliable, computationally efficient results under the physical, chemical, biological, and social complexity of stormwater management. PRACTITIONER POINTS: Over 280 studies were published in 2019 related to the characterization, control, and treatment of urban stormwater. Studies on bioretention and general stormwater characteristics represented the two most common subtopics in 2019. Trends in 2019 included novel substrate amendments, studies on the role of vegetation, and advancements in computational models.

Tsallis Entropy for Assessing Spatial Uncertainty Associated with Mean Annual Runoff of Quaternary Catchments of the Middle Vaal Basin in South Africa

This study assesses mainly the uncertainty of the mean annual runoff (MAR) for quaternary catchments (QCs) considered as metastable nonextensive systems (from Tsalllis entropy) in the Middle Vaal catchment. The study is applied to the surface water resources (WR) of the South Africa 1990 (WR90), 2005 (WR2005) and 2012 (WR2012) data sets. The q-information index (from the Tsalllis entropy) is used here as a deviation indicator for the spatial evolution of uncertainty for the different QCs, using the Shannon entropy as a baseline. It enables the determination of a (virtual) convergence point, zone of positive and negative uncertainty deviation, zone of null deviation and chaotic zone for each data set. Such a determination is not possible on the basis of the Shannon entropy alone as a measure for the MAR uncertainty of QCs, i.e., when they are viewed as extensive systems. Finally, the spatial distributions for the zones of the q-uncertainty deviation (gain or loss in information) of the MAR are derived and lead to iso q-uncertainty deviation maps.

[Effect of Optimized Fertilization and Biochar Application on Phosphorus Loss in Purple Soil Sloping Farmland]

Phosphorus is an essential nutrient for crop growth, but the input of excess phosphorus is a significant cause of eutrophication. This study explored the relationship between fertilization methods and phosphorus loss in actual production, providing a theoretical basis for scientific fertilization and rational reduction of fertilizer application. In the experiment, a wild-type OD flow plot was used to monitor the occurrence of multiple rainfall runoff and sediment yield in purple soil sloping farmland in 2017-2018. Four different schemes of non-fertilizer treatment, conventional fertilization treatment, optimized fertilization treatment, and reduced fertilization combined with biochar were studied. The effects of soil flow, surface runoff, and sediment phosphorus loss on purple soil sloping farmland were analyzed. The results showed that:①The total yield of each treatment was optimized (20737.23 L) > conventional (18513.17 L) > CK (18134.58 L) > biochar (13594.85 L), and the total sediment yield of each treatment was CK (1998 kg·hm^-2) > biochar (1884 kg·hm^-2) > optimized (1681 kg·hm^-2) > conventional (910 kg·hm^-2). The middle stream of soil is the main type of runoff in the rainy season, accounting for 60.14%-87.34% of the total output flow. The total amount of sediment produced by each treatment was not significantly different from that of the conventional treatment (P>0.05). ②The flux of total phosphorus loss in each treatment was characterized by sediment > surface runoff > soil middle flow. Phosphorus lost through the middle stream of soil is the least, accounting for only 2.63%-12.91% of the flux of total phosphorus loss, while the flux of sediment loss of phosphorus can reach 63.74%-78.74%, and thus is the main output route of soil phosphorus loss. ③The application of biochar can effectively reduce the abortion flow in the soil of purple soil sloping land, and the loss flux of orthophosphate in the middle stream, which are 49.94% and 56.45% lower than the conventional treatment, respectively. However, the interception effect on surface runoff is not good, and there is no significant influence on the flux loss of particulate phosphorus. At the same time, the flux of total phosphorus in surface runoff and sediment is significantly increased by 73.28% and 123.53%, respectively, compared with conventional treatment (P<0.05). Therefore, to control the loss of phosphorus in purple soil sloping farmland in southwest China, we should focus on reducing the occurrence of soil sediment loss. Bio-carbon should be further optimized in the practical application of agricultural production with the phosphorus fertilizer input ratio.

Infrapopliteal Anatomic Severity and Delayed Wound Healing in Patients With Chronic Limb-Threatening Ischemia in the Era of the Global Limb Anatomic Staging System

Purpose: To investigate the prognostic impact of infrapopliteal (IP) artery anatomic severity according to the Global Limb Anatomic Staging System (GLASS) on delayed wound healing in patients with chronic limb-threatening ischemia (CLTI). Materials and Methods: This study retrospectively analyzed 639 limbs with tissue loss in 484 CLTI patients (mean age 74±10 years; 300 men) presenting IP lesions treated with endovascular therapy between April 2010 and December 2015. Two-thirds of patients had diabetes (323, 67%) and over half were on hemodialysis (255, 53%). More than a third of the limbs (251, 39%) were classified as clinical stage 4 according to the Wound, Ischemia, and foot Infection (WIfI) system. IP anatomic severity was classified based on preprocedural angiography according to the GLASS. Severity of arterial calcification was assessed using high-intensity fluoroscopy and classified into 3 groups: none (grade 0), unilateral (grade 1), and bilateral (grade 2). Poor below-the-ankle (BTA) runoff was defined as the lack of a pedal arch with 0 to 1-vessel runoff within the dorsal pedis artery and the lateral and medial plantar arteries. The outcome measure was 1-year wound healing. The association of anatomic characteristics with delayed wound healing was evaluated using Cox proportional hazards regression analysis. Outcomes are presented as the adjusted hazard ratio (HR) with 95% confidence interval (CI). Results: During a mean follow-up of 22±19 months, the 1-year cumulative wound healing rate was estimated to be 59.0% (95% CI 54.5% to 63.5%). Multivariable analysis demonstrated independent associations between delayed wound healing and IP calcification grade (HR 1.24, 95% CI 1.02 to 1.50, p=0.027) and poor BTA runoff (HR 1.39, 95% CI 1.04 to 1.85, p=0.025) but not the GLASS IP grade (HR 0.92, 95% CI 0.82 to 1.14, p=0.21). Conclusion: The current study revealed that IP arterial calcification and poor BTA runoff were significantly associated with delayed wound healing, whereas the GLASS was not predictive of wound healing.

Nonwoven flax fibres geotextiles effects on solute heavy metals transport in porous media

Filtration tests were carried out in laboratory columns filled with crushed sand with and without flax geotextiles to study the transfer and retention of soluble heavy metals. Divalent cations of copper, zinc and lead were simultaneously and continuously injected in filtration columns. Results show that, when geotextiles discs are present the retention of metals in sand is favoured and retention profiles are modified. In addition, and unlike synthetic geotextiles, flax fibres geotextiles contribute to the retention of a significant fraction of the cationic metal pollutants in their own structure. The overall metals retention efficiency of the filter is improved. Competition between cationic metals for adsorption on retention sites occurs in the column in the order Pb > Cu > Zn. Most of the lead is retained in the inlet of the column while copper and even more zinc migrate deeper in the column.

Projected changes in flooding: a continental U.S. perspective

Our study focuses on the projected changes in annual and seasonal maximum daily runoff (used as a proxy for flooding) across the continental United States based on outputs from eight global climate models (GCMs) from the Sixth Coupled Model Intercomparison Project (CMIP6). Analyses performed at the regional scale indicate that the GCMs are generally able to reproduce the observed changes in runoff extremes, especially at the seasonal scale, with no single model that outperforms the others across the different seasons and regions. Overall, annual maximum daily runoff is projected to increase during the 21st century, especially in large areas of the southeastern United States and Pacific Northwest, and to decrease in the Rocky Mountains and the northern Great Plains. The largest changes in extremes are projected to be in winter and spring, with a more muted signal for summer and fall.

Analysis of Runoff Trends and Drivers in the Haihe River Basin, China

During the past decades, runoff has been highly influenced by climate change and human activities in Haihe River basin, and it is important to analyze the runoff trends and the drivers of its change to guide water resources management. The Mann–Kendall method and Pettitt test were conducted to analyze the hydrological and climate trends. Data from six sub-basins were used, including runoff at six representative hydrological stations and precipitation and air temperature at 49 meteorological stations. We used multiple-regression analysis and policy review to explore the influence of climate change and human activities on the runoff change at six sub-basins. According to the results, annual runoff showed a significant downward trend at six hydrological stations (p < 0.05), and the most probable change points at all stations showed up during the period from the late 1970s to the early 1980s. Moreover, the middle and late 1990s could be another probable abrupt change point at Luan River and Chaobai River. The declining trend of the annual mean precipitation at the six sub-basins was insignificant (p > 0.05), and there were no significant abrupt change points except the Zhang River area (p < 0.05). Compared with the precipitation trend, the annual mean air temperature exhibited a significant increasing trend at all stations, and the period from the late 1980s to the early 1990s might be the most probable abrupt change points at all four sub-basins. The trend analysis and the abrupt change point analysis suggest that mean air temperature is the main climate factor that will lead to the decline in the runoff time-series, while the insignificant downward trend of the precipitation might accelerate the downward trend of the runoff data. Through elevant policy measures, including land-use reform and the construction of the Three-North (north, northeast, and northwest China) Shelter Forest, China started to implement a family-contract responsibility system and initiated the first stage of construction of the Three-North Shelter Forest Program in 1978. The land-use reform policies greatly stimulated the peasants’ initiative for land management and significantly changed the land use pattern and water use quantity in the Haihe River basin in a short time. Besides, the precipitation decreased and the air temperature rose, so an abrupt change in runoff occurred from the late 1970s to the early 1980s. The abrupt change in the runoff in the middle and late 1990s highly tallied with the construction time of the Three-North Shelter Forest Program. After near 20 years of construction of the Three-North Shelter Forest Program, the forest area increased, the forest quality had been improved, and the vegetation coverage on the underlying surface had been changed significantly, so the construction of the Three-North Shelter Forest Program was an important cause of runoff change in the middle and late 1990s. Also, change in precipitation and air temperature enlarged the effect of change in the runoff.

Suitability of Mycorrhiza-Defective Rice and Its Progenitor for Studies on the Control of Nitrogen Loss in Paddy Fields via Arbuscular Mycorrhiza

Employing mycorrhiza-defective mutants and their progenitors does not require inoculation or elimination of the resident microbial community in the experimental study of mycorrhizal soil ecology. We aimed to examine the suitability of mycorrhiza-defective rice (non-mycorrhizal, Oryza sativa L., cv. Nipponbare) and its progenitor (mycorrhizal) to evaluate nitrogen (N) loss control from paddy fields via arbuscular mycorrhizal (AM) fungi. We grew the two rice lines in soils with the full community of AM fungi and investigated root AM colonization. In the absence of AM fungi, we estimated rice N content, soil N concentration and microbial community on the basis of phospholipid fatty acids; we also quantified N loss via NH3 volatilization, N2O emission, runoff and leaching. In the presence of AM fungi, we did not find any evidence of AM colonization for non-mycorrhizal rice while mycorrhizal rice was colonized and percentage of root colonization was 17-24%. In the absence of AM fungi, the two rice lines had similar N content, soil N concentration and microbial community. Importantly, there was no significant difference in N loss via all the four pathways between mycorrhizal and non-mycorrhizal systems. This mycorrhizal/non-mycorrhizal rice pair is suitable for further research on the role of AM fungi in the control of soil N loss in paddy fields.

Effects of Slope Ecological Restoration on Runoff and Its Response to Climate Change

Slope ecological restoration and climate change are important factors affecting the hydrological processes of the Huangshui River Basin in Qinghai province, China. How to quantitatively identify the impact of slope ecological restoration on runoff and whether slope ecological restoration can mitigate the impact of future climate change on runoff are both very important. In this paper, the Huangshui River above the center of Minhe county was taken as the research area, and the Pinus tabulaeformis and shrubs were taken as the main forest land types of slope ecological restoration. First, based on the law of forest land variation, the construction scales of slope ecological restoration in different periods were identified. The influence of slope ecological restoration on runoff was then quantitatively evaluated by using a distributed hydrological model. Second, the future climate scenarios of five general circulation models (GCMs) under three representative concentration pathways (RCPs) (i.e., RCP2.6, RCP4.5, and RCP8.5) from 2021 to 2050 were selected and modified by model integration. Combined with the slope ecological restoration scenarios, the influence of slope ecological restoration on runoff under future climate scenarios was explored. The results showed that the effect of slope ecological restoration was significant. Compared with 1980, the area of slope ecological restoration increased by 24% in 2017. Under the present climate conditions (1960–2017), different periods of slope ecological restoration have an effect on the process of runoff in the wet season (June, July, August, and September) and dry season (January, February, March, and December), which eliminates the maximum, replenishes the minimum, and reduces the variability of runoff processes in the watershed. Under the future climate scenario (2021–50), slope ecological restoration will reduce runoff. On the other hand, climate change will increase runoff, and the combination of the two effects will have a certain offsetting effect. On the whole, comparing the influence of slope ecological restoration on the runoff process with that of climate change in different seasons, due to the main influence of slope ecological restoration, the runoff decreased by about 55% in the temperate season (April, May, October, and November), and increased by about 50% in the dry season or wet season due to the main influence of future climate scenarios.

Urban stormwater characterization, control, and treatment

This review summarizes over 250 studies published in 2018 related to the characterization, control, and management of urban stormwater runoff. The review covers three broad themes: (a) quantity and quality characterization of stormwater, (b) control and treatment of stormwater runoff, and (c) implementation and assessment of watershed-scale green stormwater infrastructure (GSI). Each section provides an overview of the 2018 literature, common themes, and future work. Several themes emerged from the 2018 literature including exploration of contaminants of emerging concern within stormwater systems, characterization and incorporation of vegetation-driven dynamics in stormwater control measures, and the need for interdisciplinary perspectives on the implementation and assessment of GSI. PRACTITIONER POINTS: Over 250 studies were published in 2018 related to the characterization, control, and treatment of stormwater. Studies cover general stormwater characteristics, control and treatment systems, and watershed-scale assessments. Trends in 2018 include treatment trains, vegetation dynamics, and interdisciplinary perspectives.

Seasonal disconnect between streamflow and retention shapes riverine nitrogen export in the Willamette River Basin, Oregon

Watershed nutrient balance studies traditionally focus on annual fluxes. In areas with strongly seasonal, Mediterranean-type climate regimes, riverine nutrient export may be greater during wet seasons when hydrologic forcing overwhelms or bypasses retention mechanisms. By combining data on riverine export with spatially detailed nutrient inputs, we examine how nitrogen (N) supply, retention, and streamflow shape annual and seasonal riverine N export in Oregon's Willamette River Basin (WRB). The WRB has pronounced dry summers and wet winters, and the distribution of farmland, cities and forests create significant spatial variations in N inputs. Local data on N inputs were coupled with streamflow and chemistry to calculate fractional N export for 22 WRB sub-watersheds in the mid-2000s. For the entire WRB, 78% of the N inputs came from agricultural activities, mainly as synthetic fertilizer (69%); the next largest inputs were deposition (10%), alder fixation (5%) and point sources (5%). Crop-specific estimates of fertilizer agreed with county fertilizer sales rates at the high end of extension recommendations. Fractional riverine N export (annual riverine N export / net watershed N input) averaged 38% of net inputs in WRB tributaries, greater than other regions of North America. Fall and winter together accounted for 60-90% of the riverine N export across all watersheds. Summer export was small but was greatest in the watersheds that receive seasonal snowmelt. Large wet season losses, when biotic sinks are less active, result in a relatively high proportion of N inputs exported in this region with a Mediterranean climate and high runoff.

Integration of SWAT and HSPF for Simulation of Sediment Sources in Legacy Sediment-Impacted Agricultural Watersheds

A total maximum daily load for the Chesapeake Bay requires reduction in pollutant load from sources within the Bay watersheds. The Conestoga River watershed has been identified as a major source of sediment load to the Bay. Upland loads of sediment from agriculture are a concern; however, a large proportion of the sediment load in the Conestoga River has been linked to scour of legacy sediment associated with historic millpond sites. Clarifying this distinction and identifying specific segments associated with upland vs. channel sources has important implications for future management. In order to address this important question, we combined the strengths of two widely accepted watershed management models - Soil and Water Assessment Tool (SWAT) for upland agricultural processes, and Hydrologic Simulation Program FORTRAN (HSPF) for instream fate and transport - to create a novel linked modeling system to predict sediment loading from critical sources in the watershed including upland and channel sources, and to aid in targeted implementation of management practices. The model indicates approximately 66% of the total sediment load is derived from instream sources, in agreement with other studies in the region and can be used to support identification of these channel source segments vs. upland source segments, further improving targeted management. The innovated linked SWAT-HSPF model implemented in this study is useful for other watersheds where both upland agriculture and instream processes are important sources of sediment load.

Organic amendment additions to rangelands: A meta-analysis of multiple ecosystem outcomes

Interest in land application of organic amendments-such as biosolids, composts, and manures-is growing due to their potential to increase soil carbon and help mitigate climate change, as well as to support soil health and regenerative agriculture. While organic amendments are predominantly applied to croplands, their application is increasingly proposed on relatively arid rangelands that do not typically receive fertilizers or other inputs, creating unique concerns for outcomes such as native plant diversity and water quality. To maximize environmental benefits and minimize potential harms, we must understand how soil, water, and plant communities respond to particular amendments and site conditions. We conducted a global meta-analysis of 92 studies in which organic amendments had been added to arid, semiarid, or Mediterranean rangelands. We found that organic amendments, on average, provide some environmental benefits (increased soil carbon, soil water holding capacity, aboveground net primary productivity, and plant tissue nitrogen; decreased runoff quantity), as well as some environmental harms (increased concentrations of soil lead, runoff nitrate, and runoff phosphorus; increased soil CO₂ emissions). Published data were inadequate to fully assess impacts to native plant communities. In our models, adding higher amounts of amendment benefitted four outcomes and harmed two outcomes, whereas adding amendments with higher nitrogen concentrations benefitted two outcomes and harmed four outcomes. This suggests that trade-offs among outcomes are inevitable; however, applying low-N amendments was consistent with both maximizing benefits and minimizing harms. Short study time frames (median 1-2 years), limited geographic scope, and, for some outcomes, few published studies limit longer-term inferences from these models. Nevertheless, they provide a starting point to develop site-specific amendment application strategies aimed toward realizing the potential of this practice to contribute to climate change mitigation while minimizing negative impacts on other environmental goals.

[Dynamics and Runoff Losses of Nitrogen in Paddy Field Surface Water Under Combined Application of Biochar and Slow/Controlled-Release Fertilizer]

Field experiments were conducted to investigate the effects of four fertilization treatments, that is, controlled-release fertilizer (CRF), biochar combined with controlled-release fertilizer (BC+ CRF), biochar combined with stabilized fertilizer (BC+ SF), and biochar combined with controlled-release fertilizer and stabilized fertilizer (BC+ CRF+ SF), on the dynamics of the pH and nitrogen mass concentration and runoff losses of nitrogen in paddy field surface water in the Taihu Lake Basin. The results show that the average pH of the surface water decreases by 3.16%-4.48% for BC+ CRF+ SF and is in the range of 5.64-8.15. The average total nitrogen (TN) mass concentration of surface water ranges from 19.05 to 25.23 mg·L^-1. A significant decrease of 4.75%-6.58% in the TN mass concentration of surface water was observed for BC+ CRF+ SF. The average ammonium (NH₄⁺-N) and nitrate (NO₃^--N) mass concentration of the surface water vary from 0.01-17.26 mg·L^-1 and from 0.24-3.11 mg·L^-1, respectively. Inorganic nitrogen is dominated by NH₄⁺-N in surface water. Compared with individual CRF, other treatments significantly reduce the NH₄⁺-N mass concentration of surface water by 35.89%-48.78% and the NO₃^--N mass concentration of surface water by 20.54%-37.01%. The BC+ SF combination shows a significant reduction in the NH₄⁺-N and NO₃^--N mass concentration of the surface water, which greatly lowers the risk of inorganic nitrogen loss via runoff. The runoff losses of TN, NH₄⁺-N, and NO₃^--N are in the range of 16.24-18.09, 1.76-2.22 and 0.76-1.38 kg·hm^-2, respectively. Compared with the individual CRF, the runoff loss of TN, NH₄⁺-N, and NO₃^--N of other treatments is reduced. The BC+ CRF+ SF combination shows a significant reduction in the runoff losses of nitrogen, which greatly lowers the risk of nitrogen nonpoint source pollution from paddy fields.