Chemical speciation, pollution and ecological risk of toxic metals in readily washed off road dust in a megacity (Nanjing), China

Enfeng Liu; Xiaoyu Wang; Huiji Liu; Mengyao Liang; Yuxin Zhu; Zijun Li

doi:10.1016/j.ecoenv.2019.02.019

Chemical speciation, pollution and ecological risk of toxic metals in readily washed off road dust in a megacity (Nanjing), China

Ecotoxicol Environ Saf. 2019 May 30:173:381-392. doi: 10.1016/j.ecoenv.2019.02.019. Epub 2019 Feb 20.

Authors

Enfeng Liu¹, Xiaoyu Wang², Huiji Liu³, Mengyao Liang², Yuxin Zhu⁴, Zijun Li⁵

Affiliations

¹ College of Geography and Environment, Shandong Normal University, Ji'nan, PR China; State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, PR China. Electronic address: liuenfeng@sdnu.edu.cn.
² College of Geography and Environment, Shandong Normal University, Ji'nan, PR China.
³ State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, PR China; University of Chinese Academy of Sciences, Beijing, PR China.
⁴ State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, PR China.
⁵ College of Geography and Environment, Shandong Normal University, Ji'nan, PR China. Electronic address: lizj@sdjzu.edu.cn.

PMID: 30784802
DOI: 10.1016/j.ecoenv.2019.02.019

Abstract

Pollution of potentially toxic metals (PTMs) in road dust (RD) is becoming an important threat to the urban environmental quality and human health. The chemical speciation of PTMs is an important index charactering the risks, which may also closely relate to the pollution level and source but it was poorly understood. In this study, the chemical speciation of Cd, Cr, Cu, Ni, Pb and Zn in the RD of a megacity (Nanjing), China was determined following an optimized BCR (proposed by the European Community Bureau of Reference) sequential extraction procedure to assess their pollution and potential eco-risk and to explore the variations of metal chemical speciation with the pollution levels and sources. Total concentrations of the PTMs in the RD were enriched 1.4- to 123-fold relative to the subsoil with median contamination factors (CF) of 6.7 (Pb), 6.0 (Cu), 5.5 (Cd), 4.0 (Zn), 2.0 (Cr) and 1.9 (Ni). Pollution of the PTMs should be mainly from industrial and traffic emissions and showed high CF values in the northern industrial zone. Whereas, the chemical percentages of each metal showed relatively narrow spatial variations and were not statistically correlated with the pollution levels (p = 0.05). Comparing of similar studies indicates that no regular patterns existed in chemical percentages for each metal in RD polluted by the traffic and/or both the industrial and traffic sources. In the RD of Nanjing, Pb was mostly associated with reducible phase, Cd and Zn were mainly present in acid-soluble phase, Cu was mostly concentrated in oxidizable phase, while Cr and Ni were predominantly present in residual phase. As the typical pollutants, anthropogenic Cd, Cu, Pb and Zn were mostly associated with the potential mobile phases but also with the residual phase in the RD of Nanjing, causing 1.4- to 3.0-fold increase in the mobility. Combining the assessments from eco-risk index, risk assessment code and sediment quality guidelines with the pollution levels and chemical speciation, we deduced that Cd, Cu, Pb and Zn may pose certain eco-risk upon transport into the aquatic system and soil, and Cd should be primarily concerned.

Keywords: Chemical speciation; Ecological risk; Pb isotope; Pollution; Potentially toxic metals; Road dust.

MeSH terms

China
Cities
Dust / analysis*
Environmental Monitoring
Environmental Pollution / analysis*
Metals, Heavy / analysis*
Risk Assessment

Substances

Dust
Metals, Heavy