Chemical source profiles of urban fugitive dust PM_2.5 samples from 21 cities across China

Urban fugitive (road and construction) dust PM_2.5 samples were collected in 21 cities of seven regions in China. Seven water-soluble ions, eight sub-fractions of carbonaceous components, and 19 elements were determined to investigate the chemical profiles of urban fugitive dust. Among the analyzed chemical compositions and on regional average, the elemental compositions showed the highest proportion (12.5–28.9% in road dust (RD) and 13.1–38.0% in construction dust (CD)), followed by water-soluble ions (5.1–19.0% in RD and 4.2–16.4% in CD) and carbonaceous fractions (5.4–9.6% in RD and 4.9–9.3% in CD). Chemical compositions measured in CD were all slightly lower than those in RD although statistically insignificant (p > 0.05). Soil dust, which was estimated from Fe concentration, was proved to be the biggest contributor to urban fugitive dust PM_2.5 mass. While, it showed a higher contribution in Northern China (71.5%) than in Southern China (52.1%). Higher enrichment factors were found for elemental S, Zn and Pb in RD than CD, reflecting stronger anthropogenic sources (i.e. vehicle exhaust) in RD. Low NO₃ ⁻/SO₄ ²⁻ and high SO₄ ²⁻/K⁺ ratios both indicated that fugitive dust was strongly influenced by stationary sources (e.g. coal combustion), and this influence was especially strong in Northern China. Coefficients of divergence proved that dust profiles within the same region were more similar than across regions, reflecting that urban fugitive dust was influenced more by local sources than long-range transport.