Heavy Metal Contamination Of Road Dust In Lanzhou, China

Abstract

Road dusts were collected from the streets of the city of Lanzhou, the capital and largest city of Gansu Province in Northwest China. The potential health hazard posed by contaminated road dusts may be considerable for certain sensitive populations. Specifically young children who, while exploring their environment by mouthing and touching, may inadvertently ingest polluted soils and dusts through hand-to-mouth-activity, and through mouthing contaminated objects. Lanzhou, once ranked as one of the 10 most polluted cities in the world, clearly has, in all likelihood many locales with elevated levels of pollutants in various environmental media (e.g., air, water, soil and dust). In this study, we focus on these environmental media (road dusts), from Lanzhou with the objective of characterizing and quantifying the types of heavy metal contaminants in the medium. To characterize the metal particle constituents of the Lanzhou road dusts we used a combination of Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDS). Road dust samples were collected by brush sampling and bagging from 71 different locations in Lanzhou. Here we present analysis of 9 of these road dust samples. Heavy metals were identified at the individual particle level in the road dusts in various combinations. Many of these metals are recognized as being highly toxic and pose a potential health threat once ingested. The major heavy metals identified were: Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Sn, Pb, and W. The combination of specific elements at the individual particle level, and the morphology of the particles made it possible to attribute the particles to unique contributing sources