Review of the impact of stormwater and leaching from pavements on the environment

Nitrate pollution in urban runoff: A comprehensive risk assessment for human and ecological health

Nitrate pollution in urban runoff poses significant environmental and public health risks, with its impact varying across different land use types. This study investigates nitrate concentrations in runoff from residential, commercial, industrial, and traffic zones in Tehran, Iran, using Event Mean Concentration (EMC) analysis and Monte Carlo simulations to assess both ecological and human health risks. The results indicate that industrial and traffic zones exhibit the highest nitrate concentrations, reaching 58.13 mg/L, significantly exceeding regulatory thresholds. Ecological risk assessments highlight the potential for aquatic system degradation, while health risk evaluations reveal hazard index (HI) values surpassing the safe limit (HI > 4), particularly in industrial and high-traffic areas. These findings underscore the need for targeted mitigation strategies, including the implementation of green infrastructure and stricter pollution control measures, to improve urban water quality and reduce associated risks.

Fate of microplastics in soil-water systems: View from free radicals driven by global climate change

Microplastics are ubiquitously distributed and persistently present in soil-water systems, posing potential ecological and health risks worldwide. Free radicals are highly reactive in soil-water systems, particularly at soil-water-air interface. The dynamic changes of free radicals sensitive to environmental conditions may greatly impact the fate of microplastics. However, the pathways, reaction kinetics, or transformation products of microplastic degradation by free radicals in soil-water systems remains unclear. Climate change alters the physical and chemical environment of soil-water systems and this transformation can directly affect the degradation of microplastics, or indirectly influence it by altering the generation and species of free radicals. Here, we summarized and analyzed the impact of fluctuations in free radicals (such as superoxide radicals, hydrogen peroxide, peroxyl radicals, and hydroxyl radicals) in soil-water systems on the degradation of microplastics and their derivants. We also discussed how changes in free radicals driven by climate change affect the fate of microplastics. By integrating aspects such as climate change, free radical chemistry, and microplastic pollution, this work delineates the critical issues of microplastic pollution exacerbated by environmental condition changes. In response to the existing challenges and deficiencies in current research, feasible countermeasures are proposed. This work offers valuable insights for future research on predicting and controlling ecotoxicity and health risks caused by microplastics associated with global climate change.

Bioremediation of Heavy Metal-Contaminated Solution and Aged Refuse by Microbially Induced Calcium Carbonate Precipitation: Further Insights into Sporosarcina pasteurii

Recently, the ability of microbial-induced calcium carbonate precipitation (MICP) to remediate heavy metals has been widely explored. Sporosarcina pasteurii was selected to remediate heavy metal-contaminated solution and aged refuse, exploring the feasibility of Sporosarcina pasteurii bioremediation of heavy metals and analyzing the changes in heavy metal forms before and after bioremediation, as well as the mechanism of remediation. The results showed that Sporosarcina pasteurii achieved remediation rates of 95%, 84%, 97%, and 98% for Cd, Pb, Zn, and Cr (III) in contaminated solution, respectively. It also achieved remediation rates of 74%, 84%, and 62% for exchangeable Cd, Pb, and Zn in aged refuse, respectively. The content of exchangeable Cr (III) before bioremediation was almost zero. The content of heavy metals with exchangeable form and carbonate-bounded form in aged refuse decreased after bioremediation, while the content of heavy metals with iron-manganese oxide binding form and residual form increased. Simultaneously, the presence of Fe and Al components in aged refuse, as well as the precipitation of calcium carbonate produced during the MICP process, jointly promotes the transformation of heavy metals into more stable forms.

Parking and Public Health

PURPOSE OF REVIEW

Parking is a ubiquitous feature of the built environment, but its implications for public health are under-examined. This narrative review synthesizes literature to describe pathways through which parking may affect population health.

RECENT FINDINGS

We begin by contextualizing the issue, outlining key terminology, the sheer scale of land dedicated to parking, and the historical factors that led to this dominant land use. Next, we delineate four pathways linking parking with public health: 1) Promoting driving and car dependency, affecting air pollution, greenhouse-gas emissions, physical activity, traffic-related injuries and fatalities, and accessibility; 2) Creating impervious surfaces, with consequences for urban heat, flooding, water pollution, and green space; 3) Affecting housing affordability and associated health outcomes of this social determinant; and 4) Design, construction, and maintenance, the health impacts of which include on-street parking's positive and negative impacts on safety for all roadway users, air-quality effects of parking's construction and maintenance, and the potential for green parking lots to mitigate some health consequences of impervious surfaces. While evidence supports each pathway, additional empirical research is needed to evaluate impacts of parking on public-health outcomes. As a dominant feature of the built environment with many health implications, parking warrants attention by public-health research and practice.

From the highway to receiving water bodies: identification and simultaneous quantification of small microplastics (< 100 µm) in highway stormwater runoff

Highway stormwater (HSW) runoff is among the environment's most important sources of microplastics. This study aimed to characterize via vibrational spectroscopy and quantify SMPs (small microplastics < 100 µm) in HSW runoff from a trafficked highway entering a facility equipped with a filtration system and in those flowing out to the receiving water body near agricultural activities. Samples of the inlet runoff (from the highway) and outlet runoff (the discharge into the environment) were collected in different periods to investigate potential seasonal and spatial differences. The sampling, methodology, and analysis were thoroughly carried out to quantify and simultaneously identify SMPs via Micro-FTIR to obtain a specific novel dataset to assess the environmental quality of highway pollution. A significant difference between inlet and outlet samples was reported; the highest abundance in inlet samples was 39813 ± 277 SMPs L.1 (SW10 IN; average length of 77 µm), while the highest one in outlet samples was 15173 ± 171 SMPs L-1 (SW10 OUT; SMPs' average length of 63 µm). Polyamide 6 (PA 6) and High-Density Polyethylene (HDPE) were predominant. Our results show that these HSW treatment plants, designed for managing regulated pollutants, can intercept SMPs, improving the quality of HSW runoff discharged into the environment.

Leaching behavior of metals from asphalt mixtures modified with crumb rubber from scrap tires

There are concerns about the potential toxicity of bitumen and recycled materials such as reclaimed asphalt pavements from end-of-life roads and crumb rubber from scrap tires used in asphalt mixtures because they contain metals that may be released into the groundwater. This study investigated the potential metal leaching of laboratory-prepared asphalt mixtures modified with polymer coated rubber (PCR) with wet and dry technology, devulcanized rubber (DVR), compared to an unmodified control mixture and a blend modified with a synthetic polymer (SBS). The objectives were to i) quantify concentrations of metals released, ii) calculate the flux rate, the cumulative mass release, and the assessment ratio for each metal, iii) verify if the metals exceeded the EPA drinking water limit, and, finally, iv) assess the source of metals release. Zinc had the highest concentration among all metals and was present in eluates from all mixtures. The cumulative zinc concentration from DVR mixture was 41% and 34% higher than the control and SBS mixtures, respectively. For PCR wet, the cumulative zinc concentration was 9% higher than the control blend and 1% lower than the SBS mix. The assessment ratio indicated that all metal concentrations would not exceed the drinking water limit, except for zinc, for which further evaluations were required. The main source of zinc may derive from aggregates. This work showed that crumb rubber might not be the only source of metal leaching, and its use in asphalt pavements does not cause a metal leaching higher than other materials.

Green engineered mulch for phosphorus and metal removal from stormwater runoff in bioretention systems

Phosphorus and metals in stormwater runoff are major causes of water quality degradation. Bioretention systems are increasingly implemented to improve stormwater quality and to better manage stormwater quantity. Many studies have focused on modifying the composition of the soil bed to improve pollutant removal. However, the pollutant removal performance of bioretention systems can diminish over time, such as when clogging of the media occurs. Sediment accumulation on the soil surface may inhibit infiltration into the soil bed, thus limiting pollutant removal. Soil replacement may be eventually required as pollutants accumulate in the soil. In this study, a green retrofit material, called green engineered mulch (GEM), was generated by coating regular wood mulch with aluminum-based water treatment residuals (WTR) via a simple and low-energy process (patent pending). The GEM was developed to serve as a green retrofit for bioretention systems to enhance the removal of phosphorus and metals from stormwater runoff. The GEM was placed in a rain garden in Secaucus, NJ, USA for 15 months, during which 12 storm events (ranging from 6.0 mm to 89.6 mm) were monitored. Runoff and infiltrate samples were analyzed for dissolved and total concentrations of phosphorus and metals, along with other key water quality parameters. The GEM significantly reduced (p < 0.05) the total concentrations of phosphorus and metals in stormwater infiltrate compared to the inlet, unlike the regular mulch. Minimal or no contact with the GEM resulted in no significant pollutant removal from surface runoff. No significant pollutant export from the GEM was observed. The spent GEM can be disposed of as non-hazardous waste in municipal landfills. This study demonstrates that the GEM is a safe and effective retrofit. Moreover, the GEM is a simple and economical retrofit solution that can be used in place of regular mulch in bioretention systems.

Emerging polycyclic aromatic hydrocarbon (PAH) and trace metal leachability from reclaimed asphalt pavement (RAP)

The environmental risks associated with the storage, reuse, and disposal of unencapsulated reclaimed asphalt pavement (RAP) has been previously examined, but because of a lack of standardized column testing protocols and recent interest on emerging constituents with higher toxicity, questions surrounding leaching risks from RAP continue. To address these concerns, RAP from six, discrete stockpiles in Florida was collected and leach tested following the most up-to-date, standard column leaching protocol - United States Environmental Protection Agency (US EPA) Leaching Environmental Assessment Framework (LEAF) Method 1314. Sixteen EPA priority polycyclic aromatic hydrocarbons (PAHs), 23 emerging PAHs, identified through relevance in literature, and heavy metals were investigated. Column testing showed minimal leaching of PAHs; only eight compounds, three priority PAHs and five emerging PAHs, were released at quantifiable concentrations, and where applicable, were below US EPA Regional Screening Levels (RSL). Though emerging PAHs were identified more frequently, in most cases, priority compounds dominated contributions to overall PAH concentration and benzo(a)pyrene (BaP) equivalent toxicity. Except for arsenic, molybdenum, and vanadium in two samples, metals were found below limits of detection (LOD) or below risk thresholds. Arsenic and molybdenum concentrations diminished over time with increased exposure to liquid, but elevated vanadium concentrations persisted in one sample. Further batch testing linked vanadium to the aggregate component of the sample, unlikely to be encountered in typical RAP sources. As demonstrated by generally low constituent mobility observed during testing, the leaching risks associated with the beneficial reuse of RAP are limited, and under typical reuse conditions, factors of dilution and attenuation would likely reduce leached concentrations below relevant risk-based thresholds at a point of compliance. When considering emerging PAHs with higher toxicities, analyses indicated minimal impact to overall leachate toxicity, further suggesting that with proper management, this heavily recycled waste stream is unlikely to pose leaching risk.