Pollution characteristics, sources and health risk of metals in urban dust from different functional areas in Nanjing, China.

Urban dust is an important medium of potential toxic metal (PTM) pollution that affects human health and the urban ecosystems. A total of 374 fugitive dust samples were collected in Nanjing, a fast-developing city in southern China, including six sub-types of dust (residential district, commercial district, industrial district, traffic district, cultural and educational district, green land). Chemical analysis of eighteen metal elements by inductively coupled plasma mass spectrometry was carried out to establish the sub-type sources profiles of fine particles for fugitive dust. The results show that these metals (Cu, Zn, Se, Sr, Mo, Cd, Sb, and Pb) are mainly from anthropogenic sources and present a high degree of pollution; Mn, As, and Ba are moderately affected by human activities and present a significant degree of pollution; Ni, Co, Cr, Tl, V, Be, and Ti mainly originate from natural sources and present significant, moderate and minimal degrees of pollution. For the dust types from different functional areas, the differences of enrichment factor (EF) values were relatively small. Metals were highly concentrated in dust from residential, cultural and educational district, which had high density population and would pose higher health risk. In all types of dust, the metals rich in crust (Ti, Mn, Ba, Sr) and the metals (Cu, Zn, Pb) closely connected with city activities were the main components. Factor analysis revealed that there were six main sources of metals in dust collected from Nanjing: industrial activity, building decoration, soil dust, metal smelting, traffic emissions, and brake abrasion. Generally, noncarcinogenic and carcinogenic health risks of metals found in dust are rarely found for children and adults based on health risk assessments. However, the noncarcinogenic risk of Pb in commercial districts for children should be noted because its hazard quotient was higher than the safety threshold level. For the accumulative health risk of eighteen metals, the noncarcinogenic risk values of dust from six functional areas for children were all over the threshold (1.0), whereas below 1.0 for adults. The difference between children and adults was relatively obvious. All accumulative risk values of carcinogenic metals did not exceed the carcinogenic risk threshold of 1 × 10, which suggested that no risk prevention measures were needed.