Measurements of gaseous elemental mercury (GEM), other air pollutants, including SO2, NOx, O3, PM2:5, and CO, and meteorological conditions were carried out at Chongming Island in East China from 1 March 2014 to 31 December 2016. During the sampling period, GEM concentrations significantly decreased from 2.68 ± 1.07 ng m-3 in 2014 (March to December) to 1.60 ± 0.56 ng m-3 in 2016 (March to December). Monthly mean GEM concentration showed a significant decrease, at a rate of -0:60 ± 0:08 ng m-3 yr-1 (R2 D 0:64, p < 0.01 significance level). Combining the analysis of the potential source contribution function (PSCF), principle component analysis (PCA), and the emission inventory, we found that the Yangtze River Delta (YRD) region was the dominant source region of GEM in Chongming Island and the main source industries included coal-fired power plants, coal-fired industrial boilers, and cement clinker production. We further quantified the effect of emission change on the air Hg concentration variations at Chongming Island through a coupled method of trajectory clusters and air Hg concentrations. It was found that the reduction of domestic emissions was the main driver of GEM decline in Chongming Island, accounting for 70 % of the total decline. The results indicated that air pollution control policies targeting SO2, NOx, and particulate matter reductions had significant co-benefits on GEM.

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