Chemical profiles of urban fugitive dust PM_2.5 samples in Northern Chinese cities

Urban fugitive dust PM_2.5 samples were collected in 11 selected cities in North China, and 9 ions (SO₄²⁻, NO₃⁻, Cl⁻, F⁻, Na⁺, NH₄⁺, K⁺, Mg²⁺, and Ca²⁺) 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 PM_2.5. 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. Ca²⁺ was the most abundant cation and SO₄²⁻ 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⁻/SO₄²⁻, and high Zn/Al and Pb/Al ratios were good indicators to separate urban fugitive dust from desert dust, Chinese loess, or urban PM_2.5 samples.