Evaluation of management practices on agricultural nonpoint source pollution discharges into the rivers under climate change effects

Response of hydrology and nutrient losses to different extreme rainfall conditions in a coastal watershed influenced by orchards

Global warming is altering the frequency of extreme rainfall events and introducing uncertainties for non-point source pollution (NPSP). This research centers on orchard-influenced planting areas (OIPA) in the Wulong River Watershed of Shandong Province, China, which are known for their heightened nitrogen (N) and phosphorus (P) pollution. Leveraging meteorological data from both historical (1989-2018) and projected future periods (2041-2100), this research identified five extreme rainfall indices (ERI): R10 (moderate rain), R20 (heavy rain), R50 (rainstorm), R95p (Daily rainfall between the 95th and 99th percentile of the rainfall), and R99p (>99th percentile). Utilizing an advanced watershed hydrological model, SWAT-CO2, this study carried out a comparison between ERI and average conditions and evaluated the effects of ERI on the hydrology and nutrient losses in this coastal watershed. The findings revealed that the growth multiples of precipitation in the OIPA for five ERI varied between 16 and 59 times for the historical period and 14 to 65 times for future climate scenarios compared to the average conditions. The most pronounced increases in surface runoff and total phosphorus (TP) loss were observed with R50, R95p, and R99p, showing growth multiples as high as 352 and 330 times, and total nitrogen (TN) growth multiples varied between 4.6 and 30.3 times. The contribution rates of R50 and R99p for surface runoff and TP loss in the OIPA during all periods exceeded 55%, however, TN exhibited the opposite trend, primarily due to the dominated NO3-N leaching in the sandy soil. This research revealed how the OIPA reacts to different ERI and pinpointed essential elements influencing water and nutrient losses.

Anthropogenic stressors and the marine environment: From sources and impacts to solutions and mitigation

Human-released contaminants are often poorly understood wholistically in marine ecosystems. This review examines the sources, pathways, impacts on marine animals, and mitigation strategies of five pollutants (plastics, per- and polyfluoroalkyl substances, bisphenol compounds, ethynylestradiol, and petroleum hydrocarbons). Both abiotic and biotic mechanisms contribute to all five contaminants' movement. These pollutants cause short- and long-term effects on many biological processes genetically, molecularly, neurologically, physiologically, reproductively, and developmentally. We explore the extension of adverse outcome pathways to ecosystem effects by considering known inter-generational and trophic relations resulting in large-scale direct and indirect impacts. In doing so, we develop an understanding of their roles as environmental stressors in marine environments for targeted mitigation and future work. Ecosystems are interconnected and so international collaboration, standards, measures preceding mass production, and citizen involvement are required to protect and conserve marine life.

Unveiling the resistance of native weed communities: insights for managing invasive weed species in disturbed environments

Weed communities influence the dynamics of ecosystems, particularly in disturbed environments where anthropogenic activities often result in higher pollution. Understanding the dynamics existing between native weed communities and invasive species in disturbed environments is crucial for effective management and normal ecosystem functioning. Recognising the potential resistance of native weed communities to invasion in disturbed environments can help identify suitable native plants for restoration operations. This review aims to investigate the adaptations exhibited by native and non-native weeds that may affect invasions within disturbed environments. Factors such as ecological characteristics, altered soil conditions, and adaptations of native weed communities that potentially confer a competitive advantage relative to non-native or invasive weeds in disturbed environments are analysed. Moreover, the roles of biotic interactions such as competition, mutualistic relationships, and allelopathy in shaping the invasion resistance of native weed communities are described. Emphasis is given to the consideration of the resistance of native weeds as a key factor in invasion dynamics that provides insights for conservation and restoration efforts in disturbed environments. Additionally, this review underscores the need for further research to unravel the underlying mechanisms and to devise targeted management strategies. These strategies aim to promote the resistance of native weed communities and mitigate the negative effects of invasive weed species in disturbed environments. By delving deeper into these insights, we can gain an understanding of the ecological dynamics within disturbed ecosystems and develop valuable insights for the management of invasive species, and to restore long-term ecosystem sustainability.

Assessing spatiotemporal risks of nonpoint source pollution via soil erosion: a coastal case in the Yellow River Delta, China

Nonpoint source pollution (NPSP) has always been the dominant threat to regional waters. Based on empirical models of the revised universal soil loss equation and the phosphorus index, an NPSP risk assessment model denoted as SL-NPSRI was developed. The surface soil pollutant loss was estimated by simulating the rain-runoff topographic process, and the influence of path attenuation was quantified. A case study in the Yellow River Delta and corresponding field surveys of soil pollutants and water quality showed that the established model can be applied to evaluate the spatial heterogeneity of NPSP. NPSP usually occurs during high-intensity rainfall periods and in larger estuaries. Summer rainfall increased pollutant transport into the sea from late July to mid-August and caused estuarine dilution. Higher NPSP risks often correspond to coastal areas with lower vegetation coverage, higher soil erodibility, and higher soil pollutant concentrations. Agricultural NPSP originating from cropland significantly increase the pollutant fluxes. Therefore, area-specific land use management and vegetation coverage improvement, and temporal-specific strategies can be explored for NPSP control during source-transport hydrological processes. This research provides a novel insight for coastal NPSP simulations by comprehensively analyzing the soil erosion process and its associated pollutant loss effects, which can be useful for targeted spatiotemporal solutions.

Physicochemical and mineral properties of suspended sediments of the Tigris and Euphrates rivers in the Mesopotamian Plain

Most of the suspended river load from the Tigris and Euphrates rivers is deposited in the Mesopotamian Plain in Iraq. This suspended river load comprises sediments consisting of minerals and organic particles generated from weathering, erosion, transport, and sedimentation. Therefore, it is crucial to analyze, either quantitative or qualitatively, the types of minerals in the sediment particles transported by the suspended river load, in addition to the potential value they may add to the agricultural lands irrigated by the Tigris and Euphrates rivers. Herein, samples of suspended sediments were collected from both rivers for physical, chemical, and mineral assessments. The results revealed the predominance of silt particles, followed by clay, and then sand. The presence of clay particles increased while that of silt and sand decreased with further travel into the rivers. The pH values ranged from 7.39 to 7.70 and the electrical conductivity ranged from 1.39 to 2.16 ds m-1. The values of the total and active calcium carbonate minerals were 352.87-336.12 and 172.64-194.56 g kg-1 for the Tigris and Euphrates rivers, respectively. The mineral analysis identified the presence of non-clay minerals at a rate of 83 %, including calcite, quartz, albite, dolomite, and gypsum. Clay minerals, including chlorite, illite, montmorillonite, palygorskite, vermiculite, and kaolinite, were found at a rate of 17 %. Both rivers exhibited distributions of clay and non-clay minerals that vary as they move along the rivers.

Occurrence of rare earth elements in water, sediment, and freshwater fish of diverse trophic levels and feeding ecology: Insights from the Po river (northwest Italy)

To date, the occurrence of rare earth elements (REEs) in freshwater ecosystems has garnered limited attention in the scientific literature. Furthermore, a dearth of data exists regarding their potential bioaccumulation in freshwater fish. To fill this knowledge gap, we studied REEs concentrations in water, sediment, and fish specimens collected along the Po River (northwest Italy) and calculated biota-sediment accumulation (BSAF) and bioconcentration (BCF) factors, while taking into account fish feeding behavior and trophic level effects on the overall content of total REEs (ƩREEs). The fish communities were composed of native and non-native species. Remarkably low concentrations of REEs (<0.0003 mg/L) were detected in the water samples, indicating REEs insolubility. In contrast, sediment samples were found to be a good sink for REEs, with a higher mean ƩREEs recorded for the samples from the Moncalieri station (70.93 mg/kg). Notably, no significant differences in ƩREEs concentration were observed in the muscle tissue of fish samples from the three stations. The highest mean ƩREEs was recorded in the samples from the Murazzi station (0.027 mg/kg). The BSAF was very low, consistently below the unit, indicating an absence of bioaccumulation in fish muscle from sediment. In contrast, the BCF was high for several REEs, mainly for Sc and Y. While feeding ecology did not appear to affect REEs accumulation in muscle, there was a significant negative relationship between the trophic level and ΣREEs, indicating a trophic dilution of REEs from predator (Silurus glanis) to planktivorous (Alburnus arborella) fish. This study provides baseline concentrations, trophic transfers, and patterns of REEs in a river system. Further studies are needed to understand the transfer of REEs to other biotic components of lotic ecosystems.

Mapping and assessment of river water quality under varying hydro-climatic and pollution scenarios by integrating QUAL2K, GEFC, and GIS

Water quality modelling has proved to be effective method for managing river water quality. But the most effective and comprehensive approach involving integration of river water quality simulation and pollution visualization with the objective of pollution reduction and maintenance of environmental flow strategies has gained less attention. Thus, the objective of this study was to employ an integrated approach for mapping and analysing river water quality under various hydro-climatic and pollution scenarios. Specifically, this approach involved the integration of a river water quality simulation model, QUAL2K, Global Environmental Flow Calculator (GEFC), and Geographical Information System (GIS) to develop water quality index (WQI) based map charts of water quality. The calibrated QUAL2K model was utilized to simulate WQI parameters including water temperature, pH, electrical conductivity, dissolved oxygen (DO), biological oxygen demand (BOD), nitrates (NO3), ammonia (NH4), and alkalinity. To analyse the WQI, the Weighted Arithmetic-Water Quality Index (WA-WQI) method was employed for various individual and combined pollution scenarios, environmental flow (Eflow), and climate change scenarios. The developed integrated approach was applied to the Bhadravati segment of Bhadra River, India. The findings revealed that the prevailing WQI status of the study stretch ranged from poor to unsuitable for drinking purposes. This deterioration can be attributed to the impact of both industrial and municipal effluents. By maintaining the effective Environmental Management Class (EMC) flow rates (class C flowrate of EMC (40.32 m3/s)) in conjunction with appropriate Pollution Reduction (PR) level (10% PR) at headwater and incoming drains, the stream self-purification capacity was enhanced resulting in the Bhadravati River stretch water quality transitioning to favourable water quality condition.

Agricultural nonpoint source pollutant loads into water bodies in a typical basin in the middle reach of the Yangtze River

Phosphorus and nitrogen pollution from agricultural nonpoint sources heavily burden the water environment, and a scientific calculating system is needed to calculate the pollutant loads under the water pollution treatment. This study established a system to calculate the coefficients of agricultural nonpoint source pollutants into water bodies in the subregion in Poyang Lake basin in the middle reach of the Yangtze River combining with multiple driving factors. Validation results showed that the errors of the typical unit were 30.58% for total phosphorus (TP), 13.43% for total nitrogen (TN) and 33.93% for ammonia nitrogen (NH3-N), respectively. The errors of the subregion were 26.92% for TP, 31.83% for TN and 29.15% for NH3-N, respectively. Besides, there were higher TP and TN loads in the east area of subregion in both units and county scales, which indicated the heavy phosphorus and nitrogen burden on water environment. In contrast, higher NH3-N loads occurred in the north area of subregion. The establishment of coefficient system for agricultural pollutants into water bodies and the pollutant loads calculation would provide enlightenment for water pollution treatment and agricultural nonpoint source pollution controlling.

Sampling frequency optimization of the water quality monitoring network in São Paulo State (Brazil) towards adaptive monitoring in a developing country

Water quality monitoring networks (WQMNs) that capture both the temporal and spatial dimensions are essential to provide reliable data for assessing water quality trends in surface waters, as well as for supporting initiatives to control anthropogenic activities. Meeting these monitoring goals as efficiently as possible is crucial, especially in developing countries where the financial resources are limited and the water quality degradation is accelerating. Here, we asked if sampling frequency could be reduced while maintaining the same degree of information as with bimonthly sampling in the São Paulo State (Brazil) WQMN. For this purpose, we considered data from 2004 to 2018 for 56 monitoring sites distributed into four out of 22 of the state's water resources management units (UGRHIs, "Unidades de Gerenciamento de Recursos Hídricos"). We ran statistical tests for identifying data redundancy among two-month periods in the dry and wet seasons, followed by objective criteria to develop a sampling frequency recommendation. Our results showed that the reduction would be feasible in three UGRHIs, with the number of annual samplings ranging from two to four (instead of the original six). In both seasons, dissolved oxygen and Escherichia coli required more frequent sampling than the other analyzed parameters to adequately capture variability. The recommendation was compatible with flexible monitoring strategies observed in well-structured WQMNs worldwide, since the suggested sampling frequencies were not the same for all UGRHIs. Our approach can contribute to establishing a methodology to reevaluate WQMNs, potentially resulting in less costly and more adaptive strategies in São Paulo State and other developing areas with similar challenges.

Panorama of biogenic nano-fertilizers: A road to sustainable agriculture

The ever-increasing demand for food from the growing population has augmented the consumption of fertilizers in global agricultural practices. However, the excessive usage of chemical fertilizers with poor efficacy is drastically deteriorating ecosystem health through the degradation of soil fertility by diminishing soil microflora, environment contamination, and human health by inducing chemical remnants to the food chain. These challenges have been addressed by the integration of nanotechnological and biotechnological approaches resulting in nano-enabled biogenic fertilizers (NBF), which have revolutionized agriculture sector and food production. This review critically details the state-of-the-art NBF production, types, and mechanism involved in cultivating crop productivity/quality with insights into genetic, physiological, morphological, microbiological, and physiochemical attributes. Besides, it explores the associated challenges and future routes to promote the adoption of NBF for intelligent and sustainable agriculture. Furthermore, diverse applications of nanotechnology in precision agriculture including plant biosensors and its impact on agribusiness and environmental management are discussed.

Effects of nano metal oxide particles on denitrifying phosphorus removal system: Potential stress mechanism and recovery strategy

The accumulation of nano metal oxide particles (NMOPs) in municipal sewage treatment systems harms the microbial community and its metabolism in activated sludge system, resulting in the degradation of its pollutants removal performance. In this work, the stress effect of NMOPs on the denitrifying phosphorus removal system was systematically investigated in terms of pollutants removal performance, key enzyme activities, microbial community diversity and abundances, and intracellular metabolites. Among the ZnO NPs, TiO₂ NPs, CeO₂ NPs, and CuO NPs, the ZnO NPs showed the most significant impacts with the chemical oxygen demand, total phosphorus, and nitrate nitrogen removal ratio decreased from above 90 % to 66.50 %, 49.13 %, and 57.11 %, respectively. The addition of surfactants and chelating agents could relieve the toxic effect of NMOPs on the denitrifying phosphorus removal system, and the chelating agents were more effective than surfactants in performance recovery. After adding ethylene diamine tetra acetic acid, the removal ratio of chemical oxygen demand, total phosphorus, and nitrate nitrogen under ZnO NPs stress was restored to 87.31 %, 88.79 %, and 90.35 %, respectively. The study provides valuable knowledge to better understand the impacts and stress mechanism of NMOPs on activated sludge systems and provides a solution to recover the nutrients removal performance of denitrifying phosphorus removal system under NMOPs stress.

Applying water environment capacity to assess the non-point source pollution risks in watersheds

Comprehension of the spatial and temporal characteristics of non-point source (NPS) pollution risk in watersheds is essential for NPS pollution research and scientific management. Although the concept of water functional zones (WFZ) has been considered in the NPS pollution risk assessment process. However, no comprehensive study of the NPS pollution risk has been conducted to effectively protect water quality in watersheds with different water environment capacity. Therefore, this study proposes a new NPS pollution risk assessment method that integrates water functional zoning, receiving water body environmental capacity, and space-time distribution of pollution load for quantifying the impact of pollution discharge from sub-catchment on nearby water body quality. Based on the NPS nutrient loss process modeled by the Soil and Water Assessment Tool (SWAT), this method was used to assess the NPS pollution risk in the Le 'an River Watershed at annual and monthly scales. The results showed that the NPS pollution risk is characterized by seasonal and spatial variability and is influenced clearly by the water environment capacity. High NPS pollution loads are not necessarily high pollution risks. Conversely, a low NPS nutrient pollution load does not represent a low regional risk sensitivity. In addition, NPS risk assessment based on the water environment capacity could also distinguish the differences in risk levels that were masked by similar NPS pollutant loss and the same water function zoning to achieve accurate control of NPS pollution management in watersheds.

The impact of marine pollution on the probability of business failure: A case study of the Mar Menor lagoon

The impact of coastal water quality and its interaction with business results is still an unexplored field. This study uses a probit model and estimates marginal effects to investigate the impact of chlorophyll a concentration in the Mar Menor (Spain) coastal waters on the probability of business failure of firms located in this area. This coastal area has been in a critical ecological condition since 1980 when intensive irrigation agriculture expanded to the surroundings of this salted lagoon. Therefore, identifying the most damaging productive activities is crucial to convince companies and policymakers to overcome this situation. The most remarkable findings of our study are the following. First, we find opposing geographical impacts on the probability of business failure for companies located on the Mar Menor coast: A location effect showing a decreasing probability of business failure for companies located near the Mar Menor and a pollution effect indicating an increased probability of failure due to proximity to water pollution. Second, we further identify the economic sectors in which the pollution effect outweighs the location effect. We find that most of the examined productive activities seem to be negatively affected by the pollution effect, overcoming the positive effect of being located near the Mar Menor. Third, marine eutrophication increases the probability of business failure for some economic activities but not for others. Concretely, agricultural and transport activities benefit from being near the coast despite the quality of the water. These firms' probability of failure decreases when they are located near the sea), whereas a 1 mg/m³ increase of chlorophyll a raises the probability of business failure for accommodation services (8.4%), minor trade (9.5%), financial and real estate services (11%), and industrial and building activities (14.4%). This paper highlights the need to design effective environmental regulations to preserve the area of Mar Menor, considering the specific productive characteristics of the different agents. We highlight the sectors requiring additional incentives to implement pro-environmental strategies and reduce their contribution to environmental pollution. The main insights from this analysis are applicable to other coastal areas around the world that suffer from marine eutrophication due to human activities.

Using fluorescence index (FI) of dissolved organic matter (DOM) to identify non-point source pollution: The difference in FI between soil extracts and wastewater reveals the principle

Traceability and quantification of agricultural non-point source pollution are of great significance to water pollution management in watersheds. In this study, fluorescence components and indices of dissolved organic matter (DOM) in the river, wastewater and soil extracts from different land use types were analyzed to screen indicators that can identify non-point source pollution in 15 independent small watersheds located at the southern Qinling piedmont (China). The results showed that DOM fluorescence components in soil extracts among different land uses didn't have significant differences. The values of humification index (HIX) did not vary obviously between soil extracts and wastewater, with the mean values ranging from 3.4 to 3.9. However, the average value of fluorescence index (FI) of effluent wastewater was about 2.1 and did not change significantly through treatment. The FI values of soil extracts were generally between 1.5 and 1.7. The FI values in most river waters were just between the FI values of wastewater and soil extracts. This phenomenon indicated that FI could be used as an indicator to distinguish point source and non-point source pollution. Besides, the correlation analysis showed a significant positive relationship between the non-point source pollution calculated by FI and δ¹⁵N. The relationship was different in January and July, but further confirmed the reliability of using FI to quantify non-point source pollution. This study demonstrated the feasibility of using FI to identify non-point source pollution. When combined with handheld fluorescence spectrometers and unmanned aerial vehicle-mounted fluorescence spectrometers, this method may be adopted more widely.

Individual and combined impacts of urbanization and climate change on catchment runoff in Southeast Queensland, Australia

Assessing the impacts of climate change and land-use change is of critical importance, particularly for urbanized catchments. In this study, a novel framework was used to examine and quantify these impacts on the runoff in six catchments in Southeast Queensland, Australia. For each catchment, temporal variations in impervious areas were derived from six satellite images using a sub-pixel classification technique and incorporated into the SIMHYD hydrological model. This model was satisfactorily calibrated and validated with daily runoff observations (0.63 ≤ Nash-Sutcliffe efficiency coefficient ≤ 0.94, percent bias ≤ ±18 %) and was used to produce baseline runoff for 1986-2005 in these six catchments. The projected population increase was used to predict future imperviousness based on the linear relationship between the two. The projected rainfall and evapotranspiration were derived from the ensemble means of the eight general circulation models. Catchment runoff was projected under two climate change scenarios (RCP4.5 and 8.5), three urbanization scenarios (low, medium, and high), and six combined scenarios for two future periods (2026-2045 and 2046-2065). Comparing with the baseline, it was found that (1) climate change alone would lead to a -3.8 % to -17.6 % reduction in runoff among the six catchments, for all scenarios and both future periods; (2) a 11.8 % to 78 % increase in runoff was projected under the three urbanization scenarios, and (3) a decrease in runoff due to climate change would moderate the increase in runoff caused by urbanization. For example, the combined effect would be a 54 % increase in runoff, with a -17.2 % decrease due to climate change and 78 % increase due to urbanization. Overall, runoff in the six catchments may be significantly affected by urban expansion. From this study, decision makers could gain a better understanding of the relative importance of the effects of climate and land-use change, which can be applied when developing future long-term water management plans at the catchment scale.

Riparian areas as a conservation priority under climate change

Identifying climatic refugia is important for long-term conservation planning under climate change. Riparian areas have the potential to provide climatic refugia for wildlife, but literature remains limited, especially for plants. This study was conducted with the purpose of identifying climatic refugia of plant biodiversity in the portion of the Mekong River Basin located in Xishuangbanna, China. We first predicted the current and future (2050s and 2070s) potential distribution of 50 threatened woody species in Xishuangbanna by using an ensemble of small models, then stacked the predictions for individual species to derive spatial biodiversity patterns within each 10 × 10 km grid cell. We then identified the top 17 % of the areas for spatial biodiversity patterns as biodiversity hotspots, with climatic refugia defined as areas that remained as biodiversity hotspots over time. Stepwise regression and linear correlation were applied to analyze the environmental correlations with spatial biodiversity patterns and the relationships between climatic refugia and river distribution, respectively. Our results showed potential upward and northward shifts in threatened woody species, with range contractions and expansions predicted. The spatial biodiversity patterns shift from southeast to northwest, and were influenced by temperature, precipitation, and elevation heterogeneity. Climatic refugia under climate change were related closely to river distribution in Xishuangbanna, with riparian areas identified that could provide climatic refugia. These refugial zones are recommended as priority conservation areas for mitigating the impacts of climate change on biodiversity. Our study confirmed that riparian areas could act as climatic refugia for plants and emphasizes the conservation prioritization of riparian areas within river basins for protecting biodiversity under climate change.

Priority planting area planning for cash crops under heavy metal pollution and climate change: A case study of Ligusticum chuanxiong Hort

INTRODUCTION

Soil pollution by heavy metals and climate change pose substantial threats to the habitat suitability of cash crops. Discussing the suitability of cash crops in this context is necessary for the conservation and management of species. We developed a comprehensive evaluation system that is universally applicable to all plants stressed by heavy metal pollution.

METHODS

The MaxEnt model was used to simulate the spatial distribution of Ligusticum chuanxiong Hort within the study area (Sichuan, Shaanxi, and Chongqing) based on current and future climate conditions (RCP2.6, RCP4.5, RCP6.0, and RCP8.5 scenarios). We established the current Cd pollution status in the study area using kriging interpolation and kernel density. Additionally, the three scenarios were used in prediction models to simulate future Cd pollution conditions based on current Cd pollution data. The current and future priority planting areas for L. chuanxiong were determined by overlay analysis, and two levels of results were obtained.

RESULTS

The results revealed that the current first- and secondary-priority planting areas for L. chuanxiong were 2.06 ×10³ km² and 1.64 ×10⁴ km², respectively. Of these areas, the seven primary and twelve secondary counties for current L. chuanxiong cultivation should be given higher priority; these areas include Meishan, Qionglai, Pujiang, and other regions. Furthermore, all the priority zones based on the current and future scenarios were mainly concentrated on the Chengdu Plain, southeastern Sichuan and northern Chongqing. Future planning results indicated that Renshou, Pingwu, Meishan, Qionglai, Pengshan, and other regions are very important for L. chuanxiong planting, and a pessimistic scenario will negatively impact this potential planting. The spatial dynamics of priority areas in 2050 and 2070 clearly fluctuated under different prediction scenarios and were mainly distributed in northern Sichuan and western Chongqing.

DISCUSSION

Given these results, taking reasonable measures to replan and manage these areas is necessary. This study provides. not only a useful reference for the protection and cultivation of L. chuanxiong, but also a framework for analyzing other cash crops.

Spatial-temporal characteristics of corrected total phosphorus pollution loads from agricultural non-point sources in Tuojiang River watershed, Sichuan Province of southwestern China

Traditional method of estimating pollution loads may neglect the internal spatial heterogeneity of socio-economic driving factors, which can result in overestimate and underestimate of pollution loads. In this study, the corrected approach to estimating total phosphorus (TP) pollution load was proposed to explore its future variation to develop effective phosphorus pollution control strategies for water environment management. As the first-class tributary of the Yangtze River, the TP out of limits in the Tuojiang River is serious. Thus, based on the presently related basic datasets related to TP pollution load estimation, we firstly adopted the GM (1,1) model to predict their varied trends from 2021 to 2025. We then used the pollution emission coefficient method to calculate the TP pollution load. Moreover, considering the temporal and spatial heterogeneity of the pollutant generation coefficient, we further introduced population and GDP factors to further modify the pollutant generation coefficient to correct TP pollution load. Finally, we employed the exploratory spatial data analysis (ESDA) method to explore spatial distribution characteristics and spatial autocorrelation of TP pollution load from diverse pollution sources in 2025. The results showed that the total TP pollution load from diverse pollution sources will increase from 12,194.92 t in 2021 to 12,461.26 t in 2025, an increase of 2.18%. More concretely, the TP pollution load from rural domestic sewage, rural domestic waste and livestock, and poultry pollution sources will separately decrease by 94.24 t, 77.9 t, and 86.52 t. However, the TP pollution load from agricultural runoff and agricultural solid wastes pollution sources will increase by 74.52 t and 451.49 t, respectively. The contribution of TP pollution load from diverse pollution sources to total TP pollution load will be as follows: livestock and poultry (63.49%) > agricultural solid wastes (16.72%) > agricultural runoff (12.26%) > rural domestic sewage (4.12%) > rural domestic waste (3.41%). The difference in the spatial distribution of TP pollution load from diverse pollution sources in 2025 will be prominent. TP pollution from rural domestic sewage and rural domestic waste pollution sources is more serious in the Xindu and Longquanyi districts, and that from agricultural runoff and agricultural solid wastes pollution sources is more prominent in the midstream and downstream. TP pollution load from livestock and poultry pollution source is higher in the Renshou, Anyue, Rongxian, Luxian counties, and Jiangyang district. Additionally, TP pollution load from rural domestic sewage, rural domestic waste, agricultural runoff, and agricultural solid wastes pollution sources in 2025 will show a clear spatial correlation, but the spatial correlation of TP pollution load from livestock and poultry pollution source will be weak. The study is effective to eliminate the influence of temporal and spatial variation of pollutants generates coefficients on TP pollution load estimation. The method can reflect the actual condition of pollution loads in watersheds more objectively, which can be applied to estimate other pollution loads of similar watersheds with intensive socio-economic activities. The findings in this study can provide a critical reference for the stakeholders to balance water environment conservation and socio-economic development.

Estimation of sulfur fate and contribution to VSC emissions from lakes during algae decay

Algae decay is an important process influencing environmental variables and emissions of volatile sulfur compounds (VSCs) in eutrophic lakes. However, effects of algae decay on VSC emissions from eutrophic lakes as well as fate of algae-derived sulfur remain poorly understood. In this study, simulated algae-sediment systems were used to explore the flow and distribution of sulfur during algae decay. VSCs including hydrogen sulfide (H₂S), methanethiol (CH₃SH), carbon disulfide (CS₂) and dimethyl sulfide ((CH₃)₂S) were detected during algae decay, which increased with algae biomass and eutrophic levels in lakes. During algae decay, the highest H₂S, CH₃SH and (CH₃)₂S emission rates of 10.45, 21.82 and 43.26 μg d^-1 occurred in the first 1-2 days, respectively, while the highest CS₂ emission rates were observed between days 8 and 11. The maximum emissions of H₂S and CS₂ from algae decay were estimated at 0.51 and 0.35 mg m^-2 d^-1 in Lake Taihu, accounting for 1.57% and 0.69% of the total H₂S and CS₂ emissions of in situ, respectively. Algae decay could significantly increase the contents of total sulfur and total carbon in sediments by 2.90%-21.11% and 4.23%-45.05%, respectively. The VSC emissions during algae decay could be predicted using the multiple regression models with the contents of total carbon, total nitrogen and sulfur-containing compounds in sediments. Partial least squares path modelling demonstrated that algae decay had a low direct effect on VSC emissions with a strength of 0.06, while it had a significant influence on environmental variables with a strength of 0.63, which could affect VSC emissions with a strength of 0.85, indicating VSC emissions from eutrophic lakes were affected by the environmental variables rather than the direct influence of algae decay. These findings illustrated the mechanisms of VSC emissions during algae decay and provided insights into VSC control and mitigation for eutrophic lakes.

Environmental Impact Assessment for Animal Waste, Organic and Synthetic Fertilizers

The use of fertilizers is of the utmost importance for food security on a global scale. However, fertilizer production and overuse may yield environmental issues. In this research, Life Cycle Assessment (LCA) was used to estimate eighteen environmental impact categories for six different fertilizer products: three synthetic (ammonium nitrate; calcium ammonium nitrate; and urea ammonium nitrate) and three organic (cattle manure; compost; and a mixture of compost and synthetic fertilizer). The processes for fertilizer production were obtained from the Agribalyse database. The system boundaries were from cradle to factory gate (or farm gate in the case of animal waste), and the impact indicators were calculated per kg of nitrogen (N). The data showed that the organo-mineral fertilizer (a mix of compost and synthetic fertilizer) had the highest environmental impact according to the results for most of the impact categories. The median values for this product regarding water consumption, fossil resource use and global warming potential were 322.5 L, 3.82 kg oil equivalent and 13.70 kg CO2 equivalent, respectively, per kg of N. The respective values for cattle manure, for which the lowest environmental impact was observed, were 0.23 L of water, 0.002 kg oil-eq and 3.29 kg of CO2-eq, respectively, per kg of N. Further research should focus on the determination of the impact from other stages of the life cycle (e.g., transportation and application to the field) which were not included in this work. This research could support the selection of N fertilizer in sustainable food production.