Impact of green infrastructure on the mitigation of road-deposited sediment induced stormwater pollution

Probabilistic assessment of failure of infiltration structures under model and parametric uncertainty

We focus on the quantification of the probability of failure (PF) of an infiltration structure, of the kind that is typically employed for the implementation of low impact development strategies in urban settings. Our approach embeds various sources of uncertainty. These include (a) the mathematical models rendering key hydrological traits of the system and the ensuing model parametrization as well as (b) design variables related to the drainage structure. As such, we leverage on a rigorous multi-model Global Sensitivity Analysis framework. We consider a collection of commonly used alternative models to represent our knowledge about the conceptualization of the system functioning. Each model is characterized by a set of uncertain parameters. As an original aspect, the sensitivity metrics we consider are related to a single- and a multi-model context. The former provides information about the relative importance that model parameters conditional to the choice of a given model can have on PF. The latter yields the importance that the selection of a given model has on PF and enables one to consider at the same time all of the alternative models analyzed. We demonstrate our approach through an exemplary application focused on the preliminary design phase of infiltration structures serving a region in the northern part of Italy. Results stemming from a multi-model context suggest that the contribution arising from the adoption of a given model is key to the quantification of the degree of importance associated with each uncertain parameter.

Automated, High-Throughput Analysis of Tire-Derived p-Phenylenediamine Quinones (PPDQs) in Water by Online Membrane Sampling Coupled to MS/MS

The tire-derived contaminant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6-PPDQ) was recently identified as a potent toxin to coho salmon (Oncorhynchus kisutch). Studies investigating 6-PPDQ have employed solid-phase extraction (SPE) or liquid-liquid extraction (LLE) with liquid chromatography-mass spectrometry (LC-MS), providing excellent sensitivity and selectivity. However, cleanup and pre-enrichment steps (SPE/LLE) followed by chromatographic separation can be time- and cost-intensive, limiting sample throughput. The ubiquitous distribution of 6-PPDQ necessitates numerous measurements to identify hotspots for targeted mitigation. We recently developed condensed phase membrane introduction mass spectrometry (CP-MIMS) for rapid 6-PPDQ analysis (2.5 min/sample), with a simple workflow and low limit of detection (8 ng/L). Here, we describe improved quantitation using isotopically labeled internal standards and inclusion of a suite of PPDQ analogues. A low-cost autosampler and data processing software were developed from a three-dimensional (3D) printer and Matlab to fully realize the high-throughput capabilities of CP-MIMS. Cross-validation with a commercial LC-MS method for 10 surface waters provides excellent agreement (slope: 1.01; R2 = 0.992). We employ this analytical approach to probe fundamental questions regarding sample stability and sorption of 6-PPDQ under lab-controlled conditions. Further, the results for 192 surface water samples provide the first spatiotemporal characterization of PPDQs on Vancouver Island and the lower mainland of British Columbia.

Regional heterogeneity and driving factors of road runoff pollution from urban areas in China

Due to the multiple influences of natural and anthropogenic factors, stormwater runoff from urban roads generally presents heterogeneous pollution among cities. The identification of regional heterogeneity and related driving factors of road runoff pollution is of significance for the optimal management of road runoff pollution according to the local circumstances. In this study, the regional heterogeneity of urban road runoff pollution from fourteen representative cities in China is analyzed for four typical pollutants including total suspended solids (TSS), chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP). The results show wide variations in TSS, COD, TN and TP pollution among cities, with the average event mean concentrations ranging from 77.0 to 1347.9, 31.4 to 488.1, 0.81 to 8.46, 0.139 to 1.930 mg/L, respectively. One-way ANOVA analyses demonstrate significant differences in road runoff pollution among cities. The TSS pollution is significantly heavier for northern and northwestern inland cities than that for eastern and southern cities. Pearson correlation analysis and Stepwise linear regression analysis are performed to identify and rank the influence of climate, population, economy, industry structure, traffic and environmental quality. Direct relationships of road runoff pollution are detected with PM_2.5, PM₁₀, secondary industry, tertiary industry, annual rainfall, and urban green coverage, among which PM₁₀ and urban green coverage are the most important and common factors exerting positive and negative influences on road runoff pollution, respectively. Based on the findings of this work, improvement of atmospheric particulate pollution and increase in urban greenness are recommended measures to manage the road runoff pollution. Furthermore, the traffic-related emissions accompanying the upgrading of industry structure should be effectively controlled to attenuate the TSS and COD pollution in road runoff.

Insight into the pollution characteristics of road and roof runoff in Changsha, China

Non-point source pollution from rainwater runoff presents a serious challenge for urban water management in many cities undergoing urbanization and experiencing climate change. To alleviate water resource conflicts in Changsha, China, this study comprehensively evaluated the pollution characteristics and first flush effect (FFE) of runoff from asphalt roads and colored steel plate roofs under seven rainfall events in April-May 2022. The runoff was collected and purified using bioretention ponds. The results showed that the peak runoff pollutant concentrations occurred within the first 20 min of runoff generation and then decreased to relatively stable levels, with maximum total suspended solids (TSS) concentration and chemical oxygen demand (COD_Cr) reaching 873.5 and 207.32 mg/L, respectively, for road runoff and 162 and 73.31 mg/L for roof runoff, respectively. The main pollutants were TSS and COD_Cr, followed by ammonia nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃^--N), total phosphorus (TP), and nitrite nitrogen (NO₂^--N). Concentrations of pollutants and FFE for roof runoff were lower than those for road runoff. Road runoff had a more obvious FFE for TP and NH₄⁺-N, whereas the roof runoff showed the presence of TP and NO₃^--N. An important implication is that treating the first 30% of surface runoff from rainfall events with long antecedent dry days or high rainfall amounts is necessary to improve water quality before discharge or utilization. The study also found that road and roof runoff, after treatment with bioretention ponds, exhibit good water quality, thus, allowing their use as reclaimed water or for miscellaneous purposes in urban areas. Overall, this study provides useful information for designing management measures to mitigate runoff pollution and reuse in Changsha.

Occurrence and source of PAHs in Miankaleh International Wetland in Iran

We examined the occurrence and sources of 16 priority PAHs in the water and sediment samples of the Miankaleh Wetland (Coastal Biosphere Reserve), famous for harbouring huge flocks of migrating birds. The water and sediment samples collected from various locations were visualized and processed using a self-organizing map, positive matrix factorization and GIS. All the sediment samples, and >90% of the water samples, showed some degree of PAHs contamination. Higher PAH levels occur near the Chopoghi Channel, powerplants, sewage outfalls, and near fishing operations. Compared with previous study in this area, the PAHs concentration in the sediments of aquatic ecosystem of Miankaleh Wetland is increasing. The levels of PAH contamination seem too low to account for the mass deaths of migratory birds, and botulinus contamination seems the likely cause. Fugacity calculations show that the sediments act as a sink for PAHs. According to PMF and SOM analyses, three origins of PAHs were recognized: (i) fossil fuel and vehicular emissions with high-molecular weight PAHs (4-5 ring); (ii) municipal and industrial sewages characterized by low-molecular weight PAHs (2-3 ring) typical of petrogenic sources; and (iii) port activity characterized by prevalence of petrogenic influence and petroleum-related activities (combustion PAHs and low-molecular weight PAHs) consistent with port activity. This wetland needs serious attention because of continuous input of pollutants. The results and the methods used in this study may assist in improving coastal wetlands management.

The control efficiency and mechanism of heavy metals by permeable pavement system in runoff based on enhanced infiltration materials

As one of the commonly used stormwater management measures, permeable pavement system (PPS) played a prominent role in controlling runoff pollution and alleviating urban waterlogging. In this study, new enhanced infiltration materials (construction waste brick, coal gangue, activated carbon, multi-walled carbon nanotube, multi-layer graphene) were applied in PPS and the control efficiency and mechanism of typical heavy metals (HMs, Mn²⁺, Pb²⁺, Zn²⁺, Cu²⁺, Cd²⁺, Ni²⁺) was investigated in runoff. Furthermore, the influences of different rainfall intensities and antecedent dry periods on HMs removal by PPS were evaluated. The results showed that all PPS with enhanced infiltration materials have little leaching effect on HMs (＜3 μg/L). All the selected enhanced infiltration materials meet the requirements of PPS. The concentration of HMs in the effluent of PPS dropped sharply first, followed rebounded and then maintained at a stable range. Activated carbon PPS (AC), Multi-walled carbon nanotube PPS (MCN), and Multi-layer graphene PPS (MG) could significantly improve the control effect of PPS on nearly all selected HMs. The average removal rates of AC, MCN and MG for six HMs were 75.48%-99.35%, 81.30%-97.59%, and 73.03%-99.33%, respectively. Compared with Traditional PPS (TR), the effluent concentrations of HMs in construction waste brick PPS (CW) and coal gangue PPS (CG) were relatively higher and unstable. AC, CN and MG could adapt to different rainfall conditions and the maximum removal rates of most HMs exceed to 99%. With antecedent dry periods increased, the control effect of HMs was significantly improved. The influences of the antecedent drying period on HMs removal followed as: CW＞CG＞TR＞MG＞CN＞AC. This study provided novel methods to eliminating HMs in runoff and provides implications for the design of PPS.

Optimisation of urban-rural nature-based solutions for integrated catchment water management

Nature-based solutions (NBS) have co-benefits for water availability, water quality, and flood management. However, searching for optimal integrated urban-rural NBS planning to maximise co-benefits at a catchment scale is still limited by fragmented evaluation. This study develops an integrated urban-rural NBS planning optimisation framework based on the CatchWat-SD model, which is developed to simulate a multi-catchment integrated water cycle in the Norfolk region, UK. Three rural (runoff attenuation features, regenerative farming, floodplain) and two urban (urban green space, constructed wastewater wetlands) NBS interventions are integrated into the model at a range of implementation scales. A many-objective optimisation problem with seven water management objectives to account for flow, quality and cost indicators is formulated, and the NSGAII algorithm is adopted to search for optimal NBS portfolios. Results show that rural NBS have more significant impacts across the catchment, which increase with the scale of implementation. Integrated urban-rural NBS planning can improve water availability, water quality, and flood management simultaneously, though trade-offs exist between different objectives. Runoff attenuation features and floodplains provide the greatest benefits for water availability. Regenerative farming is most effective for water quality and flood management, though it decreases water availability by up to 15% because it retains more water in the soil. Phosphorus levels are best reduced by expansion of urban green space to decrease loading on combined sewer systems, though this trades off against water availability, flood, nitrogen and suspended solids. The proposed framework enables spatial prioritisation of NBS, which may ultimately guide multi-stakeholder decision-making, bridging the urban-rural divide in catchment water management.

Leaching risks of antibiotic resistance genes in urban underlying surface sediments during the simulated stormwater runoff and its controls

Recently, increasing attention has been paid to antibiotic resistance genes (ARGs) in urban stormwater runoff. However, no available literature could be found on ARGs leaching from urban underlying surface sediments during stormwater runoff. In this study, surface sediments from commercial public squares around Nanjing (China) was selected for the investigation of target ARGs leaching kinetics, showing that absolute abundances of target ARGs desorption reached at the equilibrium during leaching time of 120-240min with all of the desorption efficiencies about 30%, indicating that there would be low proportion of leaching ARGs in the total ARGs migrating with runoff during rainfall events. Five target ARGs leaching including intI1 (clinic), strA, strB, tetM and tetX can be better described by the pseudo-second-order equation, while qacEdelta1 leaching can be better described by the pseudo-first-order equation, and the leaching for both sul1 and sul2 can be well described by the pseudo-first-order and pseudo-second-order equations. The effects of environmental factors including S/L ratios, pH values and water temperatures indicated that leaching efficiencies of target ARGs enhanced significantly with the increase of S/L ratios and water temperatures, but decreased with the increase of pH values. The transmission experiments after the simulated solar irradiation and heat implied that both large solar UV irradiation (30W/m²) and high temperature (40℃) were conducive to conjugation and transformation frequencies of ARGs. Furthermore, both high Cao and medium PAM levels could be effective for blocking ARGs transmission in the leachate from underlying surface sediments.

Global trade drives transboundary transfer of the health impacts of polycyclic aromatic hydrocarbon emissions

International trade leads to a redistribution of pollutant emissions related to the production of goods and services and subsequently affects their severe health impacts. Here, we present a framework of emissions inventories, input-output model, numerical atmospheric chemistry model, and estimates of the global burden of disease. Specifically, we assess emissions and health impacts of polycyclic aromatic hydrocarbons (PAH), a carcinogenic byproduct of production activities, and consider income, production, final sale, and consumption stages of the global supply chain between 2012 and 2015. We find that in 2015, global anthropogenic PAH emissions were 304 Gg (95% CI: 213~421 Gg) and estimated related lifetime lung cancer deaths were 6.9 × 10⁴ (95% CI: 1.8 × 10⁴~1.5 × 10⁵ deaths). The role of trade in driving the PAH-related health risks was greater than that in driving the emissions. Our findings indicate that international cooperation is needed to optimise the global supply chains and mitigate PAH emissions and health impacts.

Decision-Making Framework for GI Layout Considering Site Suitability and Weighted Multi-Function Effectiveness: A Case Study in Beijing Sub-Center

The effectiveness of runoff control infrastructure depends on infrastructure arrangement and the severity of the problem in the study area. Green infrastructure (GI) has been widely demonstrated as a practical approach to runoff reduction and ecological improvement. However, decision-makers usually consider the cost-efficacy of the GI layout scheme as a primary factor, leading to less consideration of GI’s environmental and ecological functions. Thus, a multifunctional decision-making framework for evaluating the suitability of GI infrastructure was established. First, the study area was described by regional pollution load intensity, slope, available space, and constructible area. Then, to assess the multifunctional performance of GI, a hierarchical evaluation framework comprising three objectives, seven indices, and sixteen sub-indices was established. Weights were assigned to different indices according to stakeholders’ preferences, including government managers, researchers, and residents. The proposed framework can be extended to other cities to detect GI preference.

Adaptive pressure-driven multi-criteria spatial decision-making for a targeted placement of green and grey runoff control infrastructures

Traditional runoff control measures ignore the spatial imbalance of regional pressures, thereby failing to achieve a site-specific placement for green and grey infrastructure simultaneously. A multi-criterion decision-making framework for runoff control infrastructure spatial planning was therefore developed in this study. The pressure-state-response framework was applied to creatively match the pressure induced adjustment demands with the infrastructure effectiveness. The pressures were quantified from the perspective of environment, economy, and ecology on a grid scale. States were considered as the relative priority of regional pressure adjustment demand in multiple perspectives. Responses were presented as state-targeted green and grey infrastructure placement. Multi-perspective effectiveness of different green and grey infrastructure was simultaneously evaluated at an effective scale of controlling 1 m³/s runoff for comparison. Methods such as data mining, hydrological model simulation, and remote sensing inversion were combined to quantify the regional pressures. The capital investment and ecological impact of infrastructures were quantified from a life cycle perspective. A case study was carried out in Wuhan, China. The study area was clustered by gridded pressure into three regions. In region Ⅰ, ecological and environmental pressure were of higher weight. In region Ⅱ, the environmental pressure was dominant. In region Ⅲ, the ecological pressure took precedence over the environmental and economic constraints. The area ratios of the region Ⅰ, Ⅱ, and Ⅲ were 43%, 36%, and 21% respectively. The result indicated a synergy and spatial heterogeneity of multi-perspective pressures, and further demonstrating that expert experience tends to fail to weigh the multi-function of green and grey infrastructures for coping with the pressures. Results also stated that green infrastructures were more acceptable in areas that aspire to achieve simultaneous runoff control and ecological improvement. The decision-making framework developed in this study can maximize the overall performance by providing targeted infrastructure placement solutions.

Spatial distribution and source apportionment of polycyclic aromatic hydrocarbons in typical oasis soil of north-western China and the bacterial community response

Oases environments in oases to be sensitive to anthropogenic activity because of ecological fragility. Polycyclic aromatic hydrocarbon (PAH) pollution resulting from anthropogenic activity leads to ecological degradation in oases. To examine the impact of anthropogenic activity on the oasis ecological environment, the present study focused on the spatial distribution and source apportionment of soil PAHs and bacterial community responses in typical oases in Xinjiang, China. The results showed that the soil PAH level were higher in the city centres of Urumqi (9-6340 μg kg^-1), Aksu (8-957 μg kg^-1) and Korla (8-1103 μg kg^-1) and lower in the centres of Hotan city (11-268 μg kg^-1) and Qira county (7-163 μg kg^-1). Source apportionment suggested that gasoline emissions, diesel emissions, vehicle emissions, coal combustion, coke processing and biomass burning were the sources of soil PAHs. The integrated lifetime cancer risks of soil PAH exceeding the guideline safety values (10^-6) recommended by United States Environmental Protection Agency. The ingestion and dermal exposure pathways caused the greatest health risk (contribution ≤82%). Additionally, in the soil with low PAH concentrations, the richness and evenness of the soil bacterial community were great, and the molecular ecological network (MEN) structure was complex. Among populations, Proteobacteria and Actinobacteria (relative abundance ≥17%) are the main dominant species in the bacterial communities and the keystone species in the MEN.

Effects of low impact development on the stormwater runoff and pollution control

The frequent urbanization and extreme rainfall events have posed the threat to the urban environment. The implementation of low impact development (LID) practices with great potential for control urban flood and overflow pollution is not comprehensively understood yet due to the influence of complex factors (i.e., hydrological pattern, installation location, and vertical parameter setting). In this study, the hydraulic and water quality model were used to analyze the hydrological and pollution reduction of outfall and storage under different hydrological patterns, vertical parameter setting, and green infrastructure installation locations, which can determine the best implementation of the scheme for overflow pollution control. The results showed that nine parameters of the vertical layer regarding the four parameters impacted the peak value and load of suspended solids (SS). The combination scheme of the LID practices was further proposed based on the selection and analysis of the single LID practice. Besides, considering the installation location, the downstream installed location was a better choice. The horizontal connection of overflow runoff and pollution could be reduced by up to 9.75% and 36.46%, respectively. In addition, the horizontal connection can effectively reduce the peak value of inflow and pollutants at the time of assessing storage tank impact, which reach the maximum of 14.08% and 29.25%, respectively. The pollutants distribution became uniform and showed better resilience against rainfall intensity, which is beneficial to the management of stormwater. Our findings can provide guidance for Sponge City construction and effectively alleviate the combined sewer overflow.

Global Trends and Drivers in Consumption- and Income-Based Emissions of Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are a class of the most hazardous substances. As unavoidable byproducts of petrogenic and pyrogenic processes, their emissions are dominantly linked to various economic sectors. In international trade, not only final consumption but also primary input can transfer the emissions among regions. Therefore, a long-term impact assessment of the international trade on PAH global emissions based on the final consumption and primary input could significantly benefit worldwide PAH mitigation strategies. This study investigated the changes in consumption- and income-based PAH emissions and interregional flows of worldwide regions, using the latest available data from 1999 to 2014. Results show that in 2014, 16.8 and 10.1% of global PAH emissions were transferred by consumption and primary input through international trade. Meanwhile, the production-, consumption-, and income-based emissions in most regions were decreasing. Furthermore, from the consumption-based perspective, sub-Saharan Africa surpassed China and became the largest net exporter of consumption-based emissions. From the income-based perspective, the net income-based outflows of India and the rest of Asia increased significantly, indicating the income-based emission leakage in emerging markets. From the socioeconomic perspective, emission intensity dominated the global decline in PAH emissions. As the two main factors driving the increase in emissions, the primary input structure (41%) had a larger effect than the final demand level (28%) from 1999 to 2014. Therefore, global cooperation, through the mitigation strategies of reducing emission factors and improving international trade patterns, is posited as an efficient strategy to reduce PAH pollution and related health risks.

A Direct Mass Spectrometry Method for the Rapid Analysis of Ubiquitous Tire-Derived Toxin N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine Quinone (6-PPDQ)

The oxidative transformation product of a common tire preservative, identified as N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6-PPDQ), has recently been found to contribute to "urban runoff mortality syndrome" in Coho salmon at nanogram per liter levels. Given the number of fish-bearing streams with multiple stormwater inputs, large-scale campaigns to identify 6-PPDQ sources and evaluate mitigation strategies will require sensitive, high-throughput analytical methods. We report the development and optimization of a direct sampling tandem mass spectrometry method for semiquantitative 6-PPDQ determinations using a thin polydimethylsiloxane membrane immersion probe. The method requires no sample cleanup steps or chromatographic separations, even in complex, heterogeneous samples. Quantitation is achieved by the method of standard additions, with a detection limit of 8 ng/L and a duty cycle of 15 min/sample. High-throughput screening provides semiquantitative concentrations with similar sensitivity and a full analytical duty cycle of 2.5 min/sample. Preliminary data and performance metrics are reported for 6-PPDQ present in representative environmental and stormwater samples. The method is readily adapted for real-time process monitoring, demonstrated by following the dissolution of 6-PPDQ from tire fragments and subsequent removal in response to added sorbents.

Transport process and source contribution of nitrogen in stormwater runoff from urban catchments

Nitrogen in urban stormwater has been widely studied, and effective management of nitrogen pollution is critical for improving urban stormwater and receiving water quality. This requires an in-depth understanding of the transport process and source contribution to both dissolved and particulate nitrogen in stormwater from urban catchments. In this study, 123 stormwater runoff samples were collected from an urban catchment during different rainfall events. Dissolved and particulate nitrogen concentrations in roof runoff, road runoff, and sewer flow were analyzed. The concentration of dissolved nitrogen was higher in roof runoff than in road runoff and sewer flow. However, the concentration of particulate nitrogen was lower in roof runoff than in road runoff and sewer flow. Isotopic analysis and Bayesian mixing models showed that road runoff was the largest source contributor of both nitrate and particulate organic nitrogen (PON) in sewer flow discharged from the study catchment. In addition, road runoff contributed the majority of PON associated with coarse particles (>105 μm), whereas PON associated with fine particles (<105 μm) was primarily washed-off of sewer sediments. The results provided several suggestions for the management of nitrogen pollution in urban catchments. This study could help to fully understand the transport and sources of nitrogen pollution in urban stormwater and provide recommendations to the government for implementing appropriate stormwater management strategies to minimize stormwater pollution.

Optimizing Green-Gray Infrastructure for Non-Point Source Pollution Control under Future Uncertainties

Non-Point Source Pollution (NPS) caused by polluted and untreated stormwater runoff discharging into water bodies has become a serious threat to the ecological environment. Green infrastructure and gray infrastructure are considered to be the main stormwater management measures, and the issue of their cost-effectiveness is a widespread concern for decision makers. Multi-objective optimization is one of the most reliable and commonly used approaches in solving cost-effectiveness issues. However, many studies optimized green and gray infrastructure under an invariant condition, and the additional benefits of green infrastructure were neglected. In this study, a simulation-optimization framework was developed by integrated Stormwater Management Model (SWMM) and Non-dominated Sorting Genetic Algorithm (NSGA-II) to optimize green and gray infrastructure for NPS control under future scenarios, and a realistic area of Sponge City in Nanchang, China, was used as a typical case. Different levels of additional benefits of green infrastructure were estimated in the optimizing process. The results demonstrated that green-gray infrastructure can produce a co-benefit if the green infrastructure have appropriate Value of Additional Benefits (VAB), otherwise, gray infrastructure will be a more cost-effectiveness measure. Moreover, gray infrastructure is more sensitive than green infrastructure and green-gray infrastructure under future scenarios. The findings of the study could help decision makers to develop suitable planning for NPS control based on investment cost and water quality objectives.