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Due to the rapid expansion of cities, the impermeable area has increased. This exacerbated the accumulation of pollutants in road particles and made the road sediment one of the most widely distributed pollution carriers in the urban area. Urban-rural fringe is the frontier of urban expansion and the most dynamic area in the urban region, but less knowledge was available on the pollution status of the region. In this study, the occurrence, release behavior, and environmental risk of polycyclic aromatic hydrocarbons (PAHs) accumulated in road sediment in urban-rural fringe were systematically studied and compared with five other urban functional areas (i.e., commercial area, industrial park, residential area, traffic area, and leisure area) in Beijing, china. The concentration of ∑16PAHs in the road sediment followed in the order of petrol station (2.223 mg/kg)>crossroad (1.506 mg/kg)>main road (0.949 mg/kg)>university gate (0.841 mg/kg)>bus station (0.839 mg/kg). The PAHs concentration in the road sediment with different land use followed in the order of traffic area (3.030 mg/kg)>urban-rural fringe (1.338 mg/kg)>commercial area (0.946 mg/kg)>residential area (0.866 mg/kg)>industrial park (0.673 mg/kg)>leisure area (0.316 mg/kg). The cancer risk in the urban-rural fringe was second only to the traffic area. PAHs with low ring numbers were easier to release into the water, as indicated by that 20–95% nap could be released from the road sediment to runoff. In contrast, high-ring PAHs were more likely to accumulate in the particulate matter as <18.3% of PHE, FLA, and PYR (corresponding to 0.002–0.010 mg/kg) could be released into the water phase, which means that the removal of road sediment plays an important role in reducing pollution. Overall, this study reveals that pollution in the urban-rural fringe cannot be ignored and provides scientific data to support pollution control and risk assessment, especially for urban-rural areas. [ABSTRACT FROM AUTHOR]

Stormwater runoff samples were collected from five different land use sites (gas station, city road, campus, park, and residential) in a precipitation event on May 22nd, 2017, from a small suburban area (5 km × 2 km) of the city of Beijing, China. There were 72 types of semi-volatile organic compounds (SVOCs) found in these runoff samples, including 33 types of monocyclic aromatic hydrocarbons (MAHs), 22 types of polycyclic aromatic hydrocarbons (PAHs), 6 types of phthalate esters (PAEs), 9 types of pesticides and 2 types of polychlorinated biphenyls (PCBs). Especially, 26 types of SVOCs (7 MAHs, 9 PAHs, 5 PAEs, and 5 pesticides) were detected in all water samples. SVOCs concentrations were higher in the samples from gas station and city road, and lower in runoff from campus, park and residential sites. The change in the ratio of anthracene to anthracene plus phenanthrene (ANT/(ANT + PHE)) in this study, reflected the importance of PAH source and land use. Di-2-ethylhexyl phthalate (DEHP) and di-n-butyl phthalate, are two of the phthalate esters 100% detected in the runoff samples. The city road runoff DEHP concentrations recorded the highest values (> 6000 ng/L), however, were still less than those wastewater DEHP pollutants measured in developed countries (e.g. UK, Canada, Finland, etc.). One-way ANOVA analysis in this study, showed that land use could significantly influence 23 SVOCs in the runoff samples, whereas the runoff SVOCs in different precipitation period showed no statistical changes in the five sites, and presented a general temporal trends "high (beginning)—low (middle period)—little raising (ending)". The findings in this study could be used in municipal management of wastewater collection and treatment. [ABSTRACT FROM AUTHOR]

Purpose: Intensive urbanization decreases the self-regulation of urban ecosystems, leading to accumulation of persistent pollutants such as trace metals and metalloids in urban environments. Road-deposited sediments (RDS) are important carriers of trace metals and metalloid contaminants that could contribute to urban runoff pollution. This study aims to investigate the concentration and speciation systemically and assess the risks of trace metals and metalloids from RDS comprehensively. Materials and methods: Road-deposited sediments (RDS) were analyzed for As, Cd, Cr, Cu, Mn, Pb, and Zn, in terms of total concentrations, speciation, release, and risks at 23 sites across six land types (the rural-urban fringe, commercial, residential, industrial, traffic, and the natural areas) in Daxing District of Beijing, China, in April 2018. Risk factors evaluating different aspects included contamination levels and ecological risk, Igeo, and RI; source of metal (natural or anthropogenic), EF; bioavailability, RAC. Six particle sizes vs. metal concentrations were also analyzed for trace metals and metalloids from rural-urban fringe samples. Results and discussion: Obvious variations were found for the concentrations of Cr, As, and Cd in rural-urban area, especially for Cr. Industrial sites exhibited highest average values for all trace metals and metalloids except for As and Cu. Cr, Cd, and Pb in particular posed more risk. Traffic area showed signs of contamination for Cu, Pb, and Zn. Commercial and residential areas presented low ecological risk. However, there were signs of As and Cu contaminations in both areas, and of Pb in the residential area as well. No research sites were contaminated by Mn, despite the high concentration values. Although high contamination levels of Cr were found in many sites, the risk level of Cr was low. Generally, RDS with smaller particle size (< 80, 80–150, and 150–300 μm) possessed higher concentrations of trace metals and metalloids compared to larger size (300–500 and 500–1000 μm). Conclusion: The study showed that metals of high concentration do not always pose high risk. More attention should be paid to the systematical risk assessment of trace metals and metalloids than the concentration. [ABSTRACT FROM AUTHOR]

To identify the distribution of heavy metals in sewer sediments and assess their potential harmfulness to the environment and human health, the occurrence of Pb, Zn, Cu, and Cd in the sewer sediment of six functional areas and two streets in an inner-city suburb of Beijing, China, was investigated by using a sequential extraction procedure. Results show that the concentrations of Cu, Zn, Cd, and Pb vary between 50 and 175, between 80 and 180, between 0.75 and 2.5, and between 20 and 110 mg/kg, respectively, and Fe-Mn oxide fraction is significant for all metals in sampling areas. Pollution assessment shows that 1–2% of Cu at Chegongzhuang Street and 1–3% of Zn at Fuwai Street in the exchangeable fractions are of low risk. 10–25% of Cd at six functional areas indicates medium risk. 40–60% of Pb at Fuwai Street existing in the exchangeable fractions is of high to very high risk. The sum of these metals associated with exchangeable, carbonate bound, and Fe-Mn oxide fractions is quite high; however, these three fractions represent the proportion of heavy metals that can be remobilized by changes in environmental conditions. [ABSTRACT FROM AUTHOR]