Assessment of Heavy Metals Contamination in Near-Surface Dust

As a result of the continuous urbanization and industrialization in China over the last few decades, heavy metals have been continuously emitted into urban environments and now pose serious threats to human health. In the present study, an extensive urban near-surface dust survey was conducted in Changchun, China, to evaluate the current status of heavy metal contamination in urban dust and to identify the potential sources. A total of 232 samples were collected and the levels of Cu, Pb, Zn, Cd, Hg, As, Cr, and the major elements were then determined. The results indicated that the urban dusts were enriched with metals, particularly Cu, Cd, Zn, Pb, and Hg. Principal component analysis (PCA) was employed to identify sources of heavy metals, and the results revealed distinctly different associations among the trace metals and the major elements in the urban dusts. The concentrations of Cr and As appeared to be controlled by natural factors. Cu and Pb were mainly from vehicle emissions. Zn primarily come from traffic sources, especially vehicle tires. Additionally, Hg primarily originated from coal combustion, while Cd was mainly associated with industrial sources. A revised pollution index for each metal and a Nemerow integrated pollution index (NIPI) of the seven metals were attributed to each sampling site to assess the degree of metal contamination. The results showed that the pollution indexes (PI) of each metal are not especially high. However, a significant degree of metal pollution exists in some urban dusts in Changchun, particularly for Cu, Cd, Zn, and As. The mean value of the Nemerow integrated pollution index (NIPI) of the seven metals also indicated that urban dusts in Changchun city were classified as having moderate levels of pollution. However, it should be noted that about 11% of all samples had a NIPI value above 3, suggesting a high level of contamination by metals. These findings indicate that more attention should be paid to metal pollution of the urban dusts in Changchun in the future.