Risk Assessment of Heavy Metals in Street Dust Particles to a Stream Network

Abstract

Runoff with contaminated urban soil has an environmental risk to the aquatic environment. An assessment of heavy metals in street dust particles from a small town and their risks to the township stream network were conducted at Yangtze River delta. This assessment is based on measurement of heavy metal contents in dust particles with different particle sizes, river sediments, and suspended solids of urban runoff. The ranges of heavy metal content were 0.8–4.3, 16–380, 69–240, 9.3–350, 9.6–863 and 67–1170 mg/kg dry street dust, for Cr, Cu, Ni, Pb and Zn, respectively. Approximately 63%-71% of heavy metals were associated with particles less than 250 μ m; this particle size accounted for 40% of the total mass of street dusts. Of the five land use areas, the industrial areas had the highest heavy metal level. The smaller particle size fraction has a higher heavy metal content, low density, high mobility in runoff, and thus is a higher risk to the stream network. The topographical and hydrological features of the landscape also influence the transport of the contaminated street dusts to the aquatic environment.

Keywords:

• Size distribution
• land use
• pollutant load

Acknowledgments

This research was supported by the Key Project of Zhejiang Province (2006C13057) and the Key Project of the Knowledge Innovation Programme of CAS (KZCX1-YW-06-02). The authors are grateful to Jiaxing Academy of Agriculture Sciences and the Bureau of Water Resources of Jiaxing City for their field assistance.

Notes

*C, I, NR, OR and R represent: commercial, industrial, new residential, old residential streets and main traffic roads

The underlined data are above the SEL values. SS1 and SS2 represent the metal contents in suspended solids in two rain events

*B.R: before rain event; D.R: during rain event

*C: conduit flow; S: surface flow