University of Michigan Air Quality Laboratory, 1415 Washington Heights, SPH 1, Ann Arbor, MI 48109-2029 USA.
Sci Total Environ. 2013 Mar 15;448:84-95. doi: 10.1016/j.scitotenv.2012.08.076. Epub 2012 Sep 23.
Quantifying the local and regional impacts of speciated mercury (Hg) emissions from major urban and industrial areas is critical for understanding Hg transport and cycling in the environment. The Chicago/Gary urban area is one location where Hg emissions from industrial sources are significant and the regional transport of emissions may contribute to elevated ambient Hg concentrations at downwind locations. From July to November 2007, we collected semi-continuous measurements of gaseous elemental Hg (Hg(0)), fine particulate bound Hg (Hgp), and divalent reactive gaseous Hg (RGM) in Chicago, IL and Holland, MI to characterize the impact of Chicago/Gary source emissions on Hg concentrations in southwest Michigan and to improve our overall understanding of speciated Hg transport and deposition. The mean (and median) concentrations of Hg(0), Hgp, and RGM in Chicago were 2.5ng/m(3) (1.9ng/m(3)), 9pg/m(3) (5pg/m(3)), and 17pg/m(3) (6pg/m(3)), respectively. In Holland the mean (and median) concentrations were 1.3ng/m(3) (1.3ng/m(3)), 6pg/m(3) (6pg/m(3)), and 8pg/m(3) (2pg/m(3)), respectively. Cluster analysis of 24-hour HYSPLIT back-trajectories associated with the semi-continuous Hg measurements indicated that southwest transport from Chicago/Gary to Holland occurred during approximately 27% of the study. In Holland, under this transport regime, we observed a five-fold increase in RGM relative to the median concentration of the other transport clusters. We applied the HYSPLIT dispersion model to two case study periods to further quantify the impact of Chicago/Gary sources on southeast Michigan and investigate the role of direct transport and dispersion of speciated Hg emissions. Results suggested that more than 50% of the maximum RGM concentrations observed in Holland during the selected periods could be attributed to direct transport of primary RGM emissions from Chicago/Gary. The remaining RGM fractions are believed to be associated with Hg(0) oxidation during transport over Lake Michigan.
量化主要城市和工业地区特定形态汞（Hg）排放的局地和区域影响，对于了解 Hg 在环境中的迁移和循环至关重要。芝加哥/盖瑞（Chicago/Gary）城区是一个工业源 Hg 排放显著的地点，排放的区域传输可能导致下风处环境 Hg 浓度升高。2007 年 7 月至 11 月，我们在芝加哥（Illinois）和荷兰（Michigan）连续采集气态元素态 Hg（Hg(0)）、细颗粒结合态 Hg（Hgp）和二价反应气态 Hg（RGM）的半连续测量值，以表征芝加哥/盖瑞源排放对密歇根州西南部 Hg 浓度的影响，并提高我们对 Hg 形态传输和沉积的整体认识。芝加哥 Hg(0)、Hgp 和 RGM 的平均值（中位数）分别为 2.5ng/m(3)（1.9ng/m(3)）、9pg/m(3)（5pg/m(3)）和 17pg/m(3)（6pg/m(3)），在荷兰分别为 1.3ng/m(3)（1.3ng/m(3)）、6pg/m(3)（6pg/m(3)）和 8pg/m(3)（2pg/m(3)）。与半连续 Hg 测量值相关的 24 小时 HYSPLIT 后向轨迹聚类分析表明，大约 27%的研究期间，Hg 从芝加哥/盖瑞向荷兰的西南方向传输。在荷兰，在这种传输模式下，我们观察到 RGM 相对于其他传输群集的中位数浓度增加了五倍。我们应用 HYSPLIT 扩散模型对两个案例研究时段进行了进一步分析，以量化芝加哥/盖瑞源对密歇根州东南部的影响，并研究特定形态 Hg 排放的直接传输和扩散的作用。结果表明，在所选择的时间段内，荷兰观察到的最大 RGM 浓度的 50%以上可能归因于来自芝加哥/盖瑞的初级 RGM 排放的直接传输。其余的 RGM 分数被认为与在经过密歇根湖的传输过程中 Hg(0)的氧化有关。
