Sather Mark E, Mukerjee Shaibal, Smith Luther, Mathew Johnson, Jackson Clarence, Flournoy Michael
Air Monitoring & Grants Section, U.S. Environmental Protection Agency (EPA) Region 6, 1201 Elm Street, Dallas, Texas 75270.
Center for Environmental Measurement and Modeling, U.S. EPA (E205-03), Research Triangle Park, North Carolina 27711.
Atmos Pollut Res. 2021;12(1):148-158. doi: 10.1016/j.apr.2020.08.030.
Gaseous oxidized mercury (GOM) dry deposition measurements using surrogate surface passive samplers were collected at six sites in the Four Corners area, U.S.A., for the two-year period August, 2017-August, 2019, after the implementation of large power plant mercury emission reductions across the U.S.A. Two-year baseline GOM dry deposition measurements at the same six sites in the Four Corners area, taken before the implementation of U.S.A. power plant mercury control regulations, were conducted earlier from August, 2009-August, 2011. The GOM dry deposition rate estimate decreased at the Four Corners area high elevation remote mountain site of Molas Pass, Colorado (3249 m asl) from 0.4 ng/mh for August, 2009-August, 2011 to 0.3 ng/mh for August, 2017-August, 2019. In contrast, GOM dry deposition rate estimates for the remaining five sites increased for August, 2017-August, 2019, ranging from 0.8-1.3 ng/mh, up from the August, 2009-August, 2011 range of 0.6-1.0 ng/mh. Comparisons of median GOM dry deposition values showed a statistically significant decrease of 17 ng/m at the Molas Pass site between August, 2009-August, 2011 and August, 2017-August, 2019, and a statistically significant increase of 66 ng/m and 64 ng/m, respectively, at the Mesa Verde National Park and Farmington Substation sites between August, 2009-August, 2011 and August, 2017-August, 2019. For the four years of GOM dry deposition data collected in the Four Corners area annual GOM dry deposition levels ranged from 2237 ng/myr (at the Molas Pass high elevation remote mountain site) to 11542 ng/myr (at the Mesa Verde National Park site), and the estimates were generally higher in magnitude in the spring and summer compared to the fall and winter. In light of the unexpected increases in GOM dry deposition rates at the non-remote sites, it is suggested that large regional wildfires and local anthropogenic mercury emission sources from cities and oil/gas production areas are possible notable contributors to the GOM dry deposition measurements collected in the Four Corners area.
在美国实施大型发电厂汞减排措施后，于2017年8月至2019年8月的两年期间，使用替代表面被动采样器在美国四角地区的六个地点收集了气态氧化汞（GOM）干沉降测量数据。在美国发电厂汞控制法规实施之前，于2009年8月至2011年早些时候在四角地区相同的六个地点进行了为期两年的GOM干沉降基线测量。科罗拉多州莫拉斯山口（海拔3249米）的四角地区高海拔偏远山区站点的GOM干沉降速率估计值从2009年8月至2011年8月的0.4纳克/平方米·小时降至2017年8月至2019年8月的0.3纳克/平方米·小时。相比之下，2017年8月至2019年8月其余五个站点的GOM干沉降速率估计值有所增加，范围从0.8 - 1.3纳克/平方米·小时，高于2009年8月至2011年8月的0.6 - 1.0纳克/平方米·小时。GOM干沉降中位数的比较显示，莫拉斯山口站点在2009年8月至2011年8月和2017年8月至2019年8月之间有统计学显著下降，降幅为17纳克/平方米，而梅萨维德国家公园和法明顿变电站站点在2009年8月至2011年8月和2017年8月至2019年8月之间分别有统计学显著增加，增幅分别为66纳克/平方米和64纳克/平方米。在四角地区收集的四年GOM干沉降数据中，年度GOM干沉降水平范围从莫拉斯山口高海拔偏远山区站点的2237纳克/平方米·年到梅萨维德国家公园站点的11542纳克/平方米·年，并且春季和夏季的估计值总体上高于秋季和冬季。鉴于非偏远站点的GOM干沉降速率意外增加，建议大型区域野火以及城市和石油/天然气生产区的本地人为汞排放源可能是四角地区收集的GOM干沉降测量数据的重要贡献者。
