Source of atmospheric heavy metals in winter in Foshan, China

Long-term trends of chemical characteristics and sources of fine particle in Foshan City, Pearl River Delta: 2008–2014

“…Low levels of PM 2.5 were observed during days when a high speed wind was associated with winds from remote North China, which typically occurred in winter. The highest levels of PM 2.5 were observed in haze days when air masses came from northeast of the PRD (Tan et al, 2014b). However, it is noteworthy that the concentration of PM 2.5 decreased from 2008 to 2011, rebounded in 2012-2013, and decreased sharply in 2014.…”

“…Air pollution in Foshan exhibits a relatively small degree of spatial variation and a larger seasonal variation. During summer, fresh oceanic air masses and frequent removal of pollutants by rainfall result in significant reductions in air pollution; while in winter, air masses transported to Foshan from the PRD and inland regions will enhance the locally-derived air pollution (Tan et al, 2014a(Tan et al, , 2014b. Therefore, the overall concentrations of air pollutants are significantly higher in winter than in summer (Fig.…”

“…Foshan is one of the most populated areas in the Pearl River Delta region in south China and one of the largest manufacturing bases in the world (Tan et al, 2014b). The terrain of Foshan is generally flat, and is surrounded by mountains from three directions; thus stagnant air conditions are frequent over the area and polluted air is not readily dispersed.…”

“…B). From downtown (CC) to the rural site (GH), the local dominant emission sources in Foshan (Tan et al, 2014b) there was a small decrease in the case of secondary aerosol, such as sulfate and nitrate; a moderate decrease for primary aerosol such as chloride; and a large decrease for both primary and secondary aerosol. The largest contrast between urban and rural concentrations is for chloride, which is mainly from primary sources and its concentrations are the highest when the sampling site is close to the emission source.…”

“…where j and k are the two sampling sites, p is the number of investigated components, and x ij and x ik are the average mass concentrations of chemical component i at sites j and k (Shen et al, 2011;Tan et al, 2014b). A value close zero indicates that the two sites have very similar levels of pollutants.…”