Spatial Distribution and Source of Inorganic Elements in PM_2.5 During a Typical Winter Haze Episode in Guilin, China

Guilin, a famous tourist city, is located in northeast Guangxi Province of Southwest China. However, recently, abnormal haze events occurred frequently in the winter. To characterize inorganic elements in PM_2.5 and associated sources during a winter haze episode, 30 samples were collected from 6 sites in Guilin from December 16 to 20, 2016, and 24 inorganic elements were measured using an inductively coupled plasma mass spectrometer. The results showed that the sum of 24 inorganic elements varied from 5.47 ± 0.45 to 9.26 ± 0.73 μg m^-3, and accounting for 6.81% ± 13.35% to 8.63% ± 15.05% of PM_2.5 at all sites. Among them, crustal elements, including K, Ca, Na, Mg, Al, Fe, and Ti contributed approximately 82% ± 6%-90% ± 3%. Cluster results combined the coefficient of divergence and hierarchical cluster for inorganic elements and the sites showed that YS designated as the background site had obvious spatial heterogeneity, specially, mass concentration, and I_geo (index of geoaccumulation) values of Ni, Cr, Mo, and Ba were higher than those at the other five sites, which indicating that PM_2.5 in Guilin was significantly affected by interregional transport. The results of source apportionment showed that Al, Ti, B, Fe, Ca, Mg, and Cr were derived from road and building dust, whereas Sb, As, and Hg originated from coal combustion, Co and V from vehicle emission (such as diesel and gasoline combustion), and other metals (Zn, Pb, Mn, Ba, Cu, Ni, Se, Cd, Mo, Tl, K, and Na) from coal combustion and industrial processes.