Risk assessment of heavy metals in finer than 63-mu m dust particles from various functional areas in Xi'an, China

Heavy metals Pb, Cr, Zn, Cu, Co, Mn, and Ni in the dust particles finer than 63 mu m from four functional areas of Xi'an, i.e., residential area, educational area, park area, and traffic area, were measured using X-ray fluorescence spectrometry. The risks of these heavy metals to urban ecosystem and human health were evaluated by the potential ecological risk index and human exposure model, respectively. Compared with Shaanxi soil, the finer dust particles have elevated metal concentrations, except for Co, Mn, and Ni. All analyzed heavy metals have different variation characteristics in four functional areas. The ecological risks of Cr, Zn, Cu, Co, Mn, and Ni in the samples were at lower levels, while the presence of Pb was high. The overall ecological risks of heavy metals measured in the samples were moderate level, which were mainly caused by Pb and Cu. Health risk assessment shows that ingestion was the main exposure route of all analyzed heavy metals in the dust particles finer than 63 mu m to children and adults. The non-cancer risks of the heavy metals to children and adults were within the safe range, and the cancer risks of Cr, Co, and Ni were also within the currently acceptable range.