Trace metals in soil, dust, and tree leaves of the urban environment, Guangzhou, China

Metals have been constantly introduced to urban environments via various point and non-point sources of pollution, and have contaminated different urban compartments (sample types). However, most research projects have focused on a single environmental compartment to characterize urban metal contamination. In the present study, an integrated sampling program that includes surface soils, different size fractions of soil and road dust (<50 μm, 50–100 μm, 100–250 μm, and 250–1000 μm), tree leaves, and grasses, was conducted in a typical urban area of Guangzhou, China. The aim of the study was to investigate the interrelationships among the metal pollutants in these samples. The concentrations of trace metals varied greatly among different sample types, and their distribution was generally in the following order: road dust > soil dust ≥ surface soils ≈ top soils > grasses ≥ tree leaves. As for the relationships among the trace metals, different combinations were seen among the sample types, indicating different loadings of trace metals in the sampling medium. Significant correlations of metal concentrations were found between tree leaves and the smallest (<50 μm) fraction of road dust, and between soil dust (50–100 μm) and surface soils, suggesting that trace metals in these samples may influence each other.