Multi-isotope signatures (Cu, Zn, Pb) of different particle sizes in road-deposited sediments: a case study from industrial area

Abstract

Road-deposited sediments (RDS) are major sources of heavy metal contamination in urban areas and adversely affect surrounding environments and human health. Multi-isotope combinations (Cu, Zn, and Pb), which serve as environmental tracers, enable the identification and management of metal contaminants in RDS. Here, we present Cu, Zn, and Pb isotopic data for the first time in size-fractionated RDS samples collected from industrial areas to describe the relationship between the RDS and total suspended solids (TSS) in runoff, and to explore the feasibility of using multi-isotopes to identify sources of metal contamination. RDS in the industrial study areas had high concentrations of Cu, Zn, and Pb, and their delta Cu-65(AE647), delta Zn-66(IRMM3702), and Pb-206/Pb-207 values ranged from - 0.33 to + 0.73 parts per thousand, - 0.36 to + 0.01 parts per thousand, and 1.1418 to 1.1616, respectively. The variation in delta Cu-65(AE647) (delta Cu-65(max-min)) was larger than that of delta Zn-66(IRMM3702) (i.e., delta Zn-66(max-min)), and the isotope values of Zn and Pb (Pb-206/Pb-207) tended to increase with the concentrations of these elements. Meanwhile, the fine RDS particles (< 63 mu m) had similar Cu, Zn, and Pb isotopic compositions to those of TSS. Hierarchical cluster analyses revealed that the < 63 mu m RDS fractions were associated with the TSS. Our results also showed that a combination of Pb and either Cu or Zn could be used to distinguish between RDS and non-exhaust emissions (e.g., brake pads, tires, etc.). Multi-isotope approaches utilizing Cu, Zn, and Pb and more robust isotopic data on individual sources of metal contamination could be useful for identifying pollution sources and understanding their environmental impacts.