•Urban runoff is a major MP transport route from land to aquatic environments.•MP concentrations in urban runoff were quantitatively assessed.•Aging, transport, flux and fate of MPs in urban runoff ...are largely ignored.•Controlling MP pollution need source prevention and stormwater management.
Public concerns on microplastic (MP) pollution and its prevalence in urban runoff have grown exponentially. Huge amounts of MPs are transported from urban environments via surface runoff to different environment compartments, including rivers, lakes, reservoirs, estuaries, and oceans. The global concentrations of MPs in urban runoff range from 0 to 8580 particles/L. Understanding the sources, abundance, composition and characteristics of MPs in urban runoff on a global scale is a critical challenge because of the existence of multiple sources and spatiotemporal heterogeneity. Additionally, dynamic processes in the mobilization, aging, fragmentation, transport, and retention of MPs in urban runoff have been largely overlooked. Furthermore, the MP flux through urban runoff into rivers, lakes and even oceans is largely unknown, which is very important for better understanding the fate and transport of MPs in urban environments. Here, we provide a critical review of the global occurrence, transport, retention process, and sinks of MPs in urban runoff. Relevant policies, regulations and measures are put forward. Future global investigations and mitigation efforts will require us to address this issue cautiously, cooperating globally, nationally and regionally, and acting locally.
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Green infrastructure (GI) strategies, including green roofs, have become a common, decentralized, nature-based strategy for reducing urban runoff and restoring ecosystem services to the urban ...environment. In this study, we examined the water quality of incident rainfall and runoff from a green roof installed on top of the Jacob K. Javits Convention Center in New York City. Since the 2014 installation of this green roof, one of the largest in North America, a colony of nesting herring gulls grew to approximately 100 nesting pairs in 2018 and 150 nesting pairs in 2019. Water quality monitoring took place between September 2018 and October 2019. Except for phosphorus on some occasions, we found concentrations of nitrate, nitrite, chlorine, sulfate to be below federal drinking water standards. Levels of the fecal indicator bacteria (FIB), total coliform, E. coli, and Enterococcus, were consistently higher in runoff samples than rainwater, ranging from 150 to over 20,000 CFU/100 mL for E. coli and 100 to over 140,000 CFU/100 mL for total coliform. Quantitative polymerase chain reaction (qPCR) methods were used to search for potential opportunistic pathogens, including Legionella spp., Mycobacterium spp., Campylobacter spp., and Salmonella spp. Discovery of the presence of Catellicoccus marimammalium, a gull-associated marker in runoff water indicates that herring gulls are the likely source of contamination. Due to habitat loss, herring gulls, and other Larus gull species are increasingly nesting on urban roofs, both green (such as at the Javits Center) and conventional (such as on Rikers and Governors Islands). Habitat creation is one of the target ecosystem services desired from GI systems. Although the discharge from the green roof of the Javits Center is directed to the city's sewer system, this study demonstrates the need to treat runoff from green roofs with nesting gull populations if its intended use involves reuse or human contact.
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•Javits Center green roof runoff met tested chemical US EPA drinking water standards.•High fecal contamination exceeded regulatory limits for various water uses.•Gull presence contributed to fecal contamination on the green roof.•Runoff from gull-populated green roofs may require treatment before use.
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•The first study on the abundance of MPs in stormwater runoff in a semiarid region.•The major quantities of MPs were in rain events with higher precipitation.•PE and PS accounted for ...the largest proportion of MPs.•Stormwater runoff is a major contributor of MPs to water bodies.
Land-based sources are considered the most important source of microplastic pollution to marine environment. Stormwater runoff has been identified as one of the main pollutant contributors to water bodies. Seven sites were sampled to identify and quantify microplastics in stormwater runoff in Tijuana, Mexico. The median microplastic abundance found in the samples was between 66 and 191 particles L−1, the highest abundance being recorded in an industrial land use site. The estimated annual total microplastic loads were between 8 × 105 and 3 × 106 particles ha−1. The most abundant microplastic shape and identified polymer type were fibers and polyethylene, respectively. The highest microplastic abundances were observed in events with higher rainfall. The results have shown that stormwater runoff is an important source of microplastic to water bodies.
As a key parameter in the adsorption process, removal rate is not available under most operating conditions due to the time and cost of experimental testing. To address this issue, evaluation of the ...efficiency of NHsub.4 sup.+ removal from stormwater by coal-based granular activated carbon (CB-GAC), a novel approach, the response surface methodology (RSM), back-propagation artificial neural network (BP-ANN) coupled with genetic algorithm (GA), has been applied in this research. The sorption process was modeled based on Box-Behnben design (BBD) RSM method for independent variables: Contact time, initial concentration, temperature, and pH; suggesting a quadratic polynomial model with p-value < 0.001, Rsup.2 = 0.9762. The BP-ANN with a structure of 4-8-1 gave the best performance. Compared with the BBD-RSM model, the BP-ANN model indicated better prediction of the response with Rsup.2 = 0.9959. The weights derived from BP-ANN was further analyzed by Garson equation, and the results showed that the order of the variables’ effectiveness is as follow: Contact time (31.23%) > pH (24.68%) > temperature (22.93%) > initial concentration (21.16%). The process parameters were optimized via RSM optimization tools and GA. The results of validation experiments showed that the optimization results of GA-ANN are more accurate than BBD-RSM, with contact time = 899.41 min, initial concentration = 17.35 mg/L, temperature = 15 °C, pH = 6.98, NHsub.4 sup.+ removal rate = 63.74%, and relative error = 0.87%. Furthermore, the CB-GAC has been characterized by Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET). The isotherm and kinetic studies of the adsorption process illustrated that adsorption of NHsub.4 sup.+ onto CB-GAC corresponded Langmuir isotherm and pseudo-second-order kinetic models. The calculated maximum adsorption capacity was 0.2821 mg/g.
Bioretention is a popular stormwater management strategy that is often utilized in urban environments to combat water quality and hydrological impacts of stormwater. This goal is achieved by ...selective designing of a system, which consists of suitable vegetation at the top planted on an engineered media with drainage system and possible underdrain at the bottom. Bibliometric analysis on bioretention studies indicates that most of the original research contributions are derived from a few countries and selected research groups. Hence, most of the bioretention systems installed in diverse geographical locations are based on guidelines from climatically different countries, which often lead to operational failures. The current review critically analyzes recent research findings from the bioretention literature, provides the authors’ perspectives on the current state of knowledge, highlights the key knowledge gaps in bioretention research, and points out future research directions to make further advances in the field. Specifically, the role and desired features of bioretention components, the importance of fundamental investigations in laboratory, field-based studies and modeling efforts, the real-time process control of bioretention cells, bioretention system design considerations, and life cycle assessment of full-scale bioretention systems are discussed. The importance of local conditions in guiding bioretention designs in difference climates is emphasized. At the end of the review, current technical challenges are identified and recommendations to overcome them are provided. This comprehensive review not only offers fundamental insights into bioretention technology, but also provides novel ideas to combat issues related to urban runoff and achieve sustainable stormwater management.
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•Bioretention is used to combat water quality and hydrological impacts of stormwater.•The role of bioretention components such as vegetation and media should be assessed.•Long-term research studies are relatively limited in the bioretention field.•Models aid in simulating the hydrologic and runoff quality aspects of bioretention.
Low Impact Development Best Management Practices (LID-BMPs) have in recent years received much recognition as cost-effective measures for mitigating urban runoff impacts. In the present paper, a ...procedure for LID-BMPs planning and analysis using a comprehensive decision support tool was proposed. A case study was conducted to the planning of an LID-BMPs implementation effort at a college campus in Foshan, Guangdong Province, China. By examining information obtained, potential LID-BMPs were first selected. SUSTAIN was then used to analyze four runoff control scenarios, namely: pre-development scenario; basic scenario (existing campus development plan without BMP control); Scenario 1 (least-cost BMPs implementation); and, Scenario 2 (maximized BMPs performance). A sensitivity analysis was also performed to assess the impact of the hydrologic and water quality parameters. The optimal solution for each of the two LID-BMPs scenarios was obtained by using the non-dominated sorting genetic algorithm-II (NSGA-II). Finally, the cost-effectiveness of the LID-BMPs implementation scenarios was examined by determining the incremental cost for a unit improvement of control.
•A methodology for LID-BMPs planning using a comprehensive decision support tool was proposed.•A case study was conducted for the LID-BMPs planning at a college campus.•A sensitivity analysis was performed to assess the impact of the hydrologic and water quality parameters.•The optimal solution for LID-BMPs scenarios was obtained by using NSGA-II option.
Urban development has led to an increase in urban runoff, accompanied with a decrease in water quality during rain events. One of the major causes of the decrease in water quality is the presence of ...trace organic contaminants in urban runoff. However, little is known about the sources of organic contaminants in urban runoff, especially related to land-use and temporal trends in those associated land uses. The objective of this study was to assess the occurrence and concentration trends of organic contaminants for a high-density residential site and commercial strip site in Madison, WI. Flow-weighted samples of urban stormwater runoff, collected with an auto-sampler, were composited and analyzed, producing mean organic contaminants concentrations for each storm event. The contaminants, which include pesticides, flame retardants, polycyclic aromatic hydrocarbons, corrosion inhibitors, among others, were extracted and analyzed by gas chromatography coupled with mass spectrometry or liquid chromatography coupled with tandem mass spectrometry. There were 30 organic contaminants that had greater than 50% detections in at least one of the sites, and those organic contaminants did provide information on similarities and differences of organic contaminants in urban runoff derived from different land uses. The sum of the total measured pesticides showed no significant difference between sites; this was likely due to the considerable green space and associated pesticide use in both sites. However, there were higher total concentrations of organophosphate flame retardants and corrosion inhibitors in the residential site. The reason for this is unknown and will require follow-up studies; however, several hypotheses are presented. Conversely, there were higher total concentrations of polycyclic aromatic hydrocarbons in the commercial site; this is most likely due to higher vehicle traffic in the commercial site. These data show that land-use may be important in determining the composition and concentrations of trace organic contaminants in urban stormwater runoff.
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•Focus is trace organics in the less-studied dissolved (bioavailable) phase of stormwater.•Wastewater associated compounds often detected in runoff at both sites.•Temporal trends for agricultural-use pesticides in stormwater related to application.•Detections suggest leaching of organic compounds from treated outdoor sources.•Heavier traffic trends with higher concentrations of PAHs, but not other compounds.
This is the first study to investigate the role that urban land use plays in the levels of trace organic chemicals in urban stormwater in the U.S.
Urban and highway surfaces discharge polluted runoff during storm events. To mitigate environmental risks, stormwater retention ponds are commonly constructed to treat the runoff water. This study is ...the first to quantify the retention of microplastics in the sediments of such ponds. It applied state-of-art FTIR-methods to analyse the composition, size, shape, and mass of microplastics in the range 10–2000 μm. Seven ponds serving four land uses were investigated, and the results are related to catchment characteristics, sediment organic matter content, and hydraulic loading. We have not found a correlation between the microplastics abundance, polymer composition, size distribution and the land use in the catchment, as well as the sediment organic matter content. Both the highest (127,986 items kg−1; 28,732 μg kg−1) and the lowest (1511 items kg−1; 115 μg kg−1) accumulation of microplastics were found in the sediments of ponds serving industrial areas. There was, however, a correlation to the hydraulic loading of the ponds, where the sediments of the highest-loaded ponds held the most microplastics. This study shows that sediments in stormwater retention ponds can trap some of the microplastics and prevent them from being transported downstream. These systems need to be considered when assessing the fate of microplastics from urban and highway areas.
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•A first assessment of microplastics in the sediments of stormwater retention ponds.•Ponds experiencing a higher hydraulic load accumulated more microplastics.•Most identified microplastics were in the size range 10–250 μm.•Polypropylene was the dominating polymer, in terms of both particle number and mass.
The study demonstrated that stormwater retention pond is able to trap microplastics from urban and highway runoff in sediments, and the retention is correlated to the hydraulic loading of the pond.
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•Find an optimal solution for LIDs’ design under climate scenarios.•Satisfaction of watershed management goals subjected to climate change impacts.•18% runoff volume reduction by ...allocating 0.23% of the area to implement LIDs.•The unique solution meets the goals for all considered climate scenarios at once.
Urban drainage systems are generally designed based on the analysis of historical hydrologic variables, especially rainfall. Hydrologic analysis, however, has been shown to be affected by climate change. In response to the modified pattern of rainfall, stormwater management practices, such as Low Impact Developments (LIDs), need to be applied to successfully respond to the possible future climatic conditions, while meeting the performance criteria based on the current state of the watershed. In this study, a simulation-optimization framework is proposed to find the optimal design of LIDs (type, location, and area) under climate change. Storm Water Management Model (SWMM) is utilized to simulate the rainfall-runoff process. This model is linked with a single-objective optimization routine formulated by Genetic Algorithm (GA) that minimizes runoff volume and the costs associated with the LIDs’ design. To investigate how climate change might affect the future watershed runoff, rainfall projections by several General Circulation Models (GCMs) are used. Change factor methodology is applied to downscale GCMs’ outputs. The framework is applied to the Velenjak watershed, located in the northeastern Tehran, Iran. Results show that the optimization algorithm provides optimal solutions for LIDs’ design under different extreme climate scenarios by allocating an average of 0.23% of the watershed area (20% of the maximum potential area considered for LIDs’ implementation), which results in a runoff volume reduction of up to 18%. The results also indicate that the optimal design of LIDs based on the current condition satisfies the watershed management goals and expectations in a future subjected to climate change impacts. Moreover, the results signify that the formulated multi-event optimization algorithm provides a unique solution meeting the objective functions for all considered climate scenarios at once.
In cities, urbanization tends to replace open soils that were naturally used for water storage with impermeable roofs and roads. These impervious surfaces have led to the development of urban heat ...island effects and to the occurrence of urban flooding during high intensity rainfalls. This phenomenon can be alleviated through the use of water-retaining (WR) pavements to hold rainwater for the subsequent evaporative cooling. These WR pavements are typically constructed as a porous pavement with water-holding media, which occupy the cavity of the matrix and decrease the amount of stored water for evaporation cooling. In this paper, a novel WR paver block is utilized to enhance the water storage capacity of the pavement system by retaining the water in the paver block without the need of water-holding layers. The new block retains the water in the block’s matrix by sealing the bottom and sides of the block with impervious media. The albedo, temperature, and WR capacities of this new paver block were measured and compared with conventional dense and pervious pavement options. It is found that even though the albedo of a new paver block is 0.10–0.15 lower than a conventional or pervious block, the new block can be 2–10 °C cooler. For 6 cm-thick paver blocks, the WR paver block can retain about 9.5 L/m2 water, which can be removed during a hot sunny day through evaporation. Pavements made of interlocking WR paver blocks can be used as a strategy to mitigate urban heat island and reduce urban runoff simultaneously.
•A new water-retaining (WR) paver block for capturing rainwater and cooling pavement was developed.•Evaporation dries the WR blocks within 2 days.•Evaporation keeps the paver block cooler about 2–10 °C on hot summer days.•Pavements made of interlocking WR blocks limits urban island effect and urban flooding.
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