Variability of Metal(loid) Contamination in Road Dust from an Urban Park and a Traffic Intersection Between Two Rainfall Events and Its Implications
Metal(loid) pollutants in road dust (road-deposited sediment) show obvious seasonal characteristics under the influence of sources. However, the short-term (days to weeks) variations of metal contamination in road dust in different functional areas with antecedent dry days (ADDs) and their relationships with the source factors were poorly understood, which reduced the comparability of researches and effectiveness of pollution remediation. Herein, temporal characteristics of As, Ba, Ca, Cd, Cr, Cu, Pb and Zn contamination in road dust were studied in two distinct functional areas in Nanjing, i.e. an urban park (Xuanwu, XW) and a stop light-controlled traffic intersection (Baima, BM), following a continuous 23-day sampling between two rainfall events. Mean concentrations of each metal at BM and XW were.6–29.5 and.3–10.8 times higher than those in the background soil, respectively. The enrichment factor (EF) was used to compensate for grain-size effect. EFs of metals were between.3 and 50.3, showing minor to extremely high contamination and different temporal trends. Combined with the EFs and positive matrix factorization (PMF) results, dry atmospheric deposition of industrial and construction sources was the main cause for comparable contamination levels of As, Ca, Cd and Zn between BM and XW and those stable temporal trends. Due to the traffic contribution, contamination levels of Cu, Ba, Pb and Cr at BM were higher (p < .05) than at XW. Different from the stable contamination levels at XW, contamination levels of Cu, Ba, Pb and Cr decreased at BM with the ADDs due to the dilution of traffic particles by less metal enriched atmospheric deposition. These results shed light on the quite different variations of metal contamination in road dust from different functional areas with ADDs under the influence sources, and have instructive significance on road dust sampling, metal contamination remediation and comparison between studies.
