Yali Lei

Chemical profiles of urban fugitive dust PM2.5 samples in Northern Chinese cities

Urban fugitive dust PM2.5 samples were collected in 11 selected cities in North China, and 9 ions (SO4(2-), NO3(-), Cl(-), F(-), Na(+), NH4(+), K(+), Mg(2+), and Ca(2+)) and 22 elements (Si, Al, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Br, Rb, Sr, Sn, Sb, Ba, and Pb) were determined to investigate chemical profiles of PM2.5. The coefficient of divergence (CD) was used to compare the similarities of the chemical profiles for fugitive dust among three regions in North China, and the results showed that their composition are quite similar. Total water soluble ions occupied 9.3% and 10.0% on average of road dust and construction dust, respectively, indicating that most of the materials in urban fugitive dust samples were insoluble. Ca(2+) was the most abundant cation and SO4(2-) dominated in anions. Soil dust loading was calculated to occupy 70.8% and 83.6% in road dust and construction dust, respectively. Ca, Si, Fe, and Al were the most abundant elements in all the samples, and Ca was absolutely the most abundant specie among the 22 detected elements in construction dust samples. Chemical species ratios were used to highlight the characteristics of urban fugitive dust by comparing with other types of aerosols. High Ca/Al ratio was a good marker to distinguish urban fugitive dust from Asian dust and Chinese loess. In addition, low K(+)/K and NO3(-)/SO4(2-), and high Zn/Al and Pb/Al ratios were good indicators to separate urban fugitive dust from desert dust, Chinese loess, or urban PM2.5 samples.

Chemical source profiles of urban fugitive dust PM2.5 samples from 21 cities across China

Urban fugitive (road and construction) dust PM2.5 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 PM2.5 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-/SO42- and high SO42-/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.