Measurements of gaseous elemental Hg (GEM), other air pollutants including SO₂, NO_x, O₃, PM_2.5, CO, and meteorological conditions were carried out at Chongming Island in East China from March 1 in 2014 to December 31 in 2016. During the sampling period, GEM concentrations significantly decreased from 2.68&amp;thinsp;&amp;plusmn;&amp;thinsp;1.07&amp;thinsp;ng&amp;thinsp;m^&amp;minus;3 in 2014 to 1.60&amp;thinsp;&amp;plusmn;&amp;thinsp;0.56&amp;thinsp;ng&amp;thinsp;m^&amp;minus;3 in 2016. Monthly mean GEM concentrations showed a significant decrease with a rate of &amp;minus;0.60&amp;thinsp;ng&amp;thinsp;m^&amp;minus;3&amp;thinsp;yr^&amp;minus;1 (R²&amp;thinsp;=&amp;thinsp;0.6389, p&amp;thinsp;<&amp;thinsp;0.01 significance level). Combining the analysis of potential source contribution function (PSCF), principle component analysis (PCA), and emission inventory, we found that Yangtze River Delta (YRD) region was the dominant source region of atmospheric mercury 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 find that the reduction of domestic emissions was the main driver of GEM decline in Chongming Island, accounting for 66&amp;thinsp;% of the total decline. The results indicated that air pollution control policies targeting SO₂, NO_x and particulate matter reductions had significant co-benefits on atmospheric mercury.