Nie Xiaoling, Wu Chen, Zhang Houyong, Li Yanbin, Li Tao, Wang Yan
School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China.
Jinhua Municipal Water Conservancy Bureau of Zhejiang Province, Jinhua 321000, China.
Ecotoxicol Environ Saf. 2023 Feb;251:114529. doi: 10.1016/j.ecoenv.2023.114529. Epub 2023 Jan 12.
Understanding the speciation and related influence factors of Hg in wet deposition is important to predict the fate and transport of mercury in the atmosphere. In this study, event-based samples of rainwater were collected for one year in Jinan, a northern city in eastern China. The volume-weighted mean concentration of total mercury (THg) in rainwater was 34.8 ng L, comparable to levels in some inland cities in China and were significantly higher than those in North America, Korea and Japan. Most of the Hg in rainwater was associated with particulates, accounted for 15.2-92.9% of THg with a mean of 66.9%, which might be attributed to the scavenging effects of high particulate-bound mercury concentrations in ambient air in urban Jinan. Dissolved mercury (DHg) accounted for 33.1% of THg, in which Hg(OH), HgClOH, HgCl and Hg(NH) are the dominant species based on the chemical equilibrium modeling simulations. THg concentrations in rainwater decreased as the rainfall amount increased owing to the dilution effect and 5 mm rainfall might be a threshold for the full wash-out capability of atmospheric Hg. For a continuous rain event, the proportion of DHg in THg could increase from 7.1% to 84.8% with the rainfall processing, especially for the species of HgClOH and HgCl under the influence of rainwater pH. Positive matrix factorization (PMF) analysis suggested that the major sources of Hg in rainwater were combustion emissions, marine sources, industrial emissions, as well as complexation process, which contributed to 51.4%, 24.7%, 12.2%, and 11.7% of the THg, respectively. For the specific species, the main sources varied with different Hg species, in which combustion emissions contributed one third to one half of each species sum to particulate mercury (PHg), HgClOH, HgCl, HgBrOH and HgBrCl followed by marine sources and industrial emissions. Cluster analysis of backward trajectories revealed that polluted air masses, transported from southeast Shandong, Anhui and Jiangsu Provinces, as well as Beijing-Tianjin-Hebei region, contributed to high Hg concentration in rainwater in Jinan.
了解湿沉降中汞的形态及相关影响因素对于预测汞在大气中的迁移转化至关重要。本研究在中国东部北方城市济南采集了为期一年的基于降雨事件的雨水样本。雨水中总汞（THg）的体积加权平均浓度为34.8 ng/L，与中国一些内陆城市的水平相当，且显著高于北美、韩国和日本的水平。雨水中的大部分汞与颗粒物相关，占THg的15.2% - 92.9%，平均为66.9%，这可能归因于济南市区环境空气中高浓度颗粒态汞的清除作用。溶解态汞（DHg）占THg的33.1%，基于化学平衡模拟，其中Hg(OH)、HgClOH、HgCl和Hg(NH)为主要形态。由于稀释作用，雨水中THg浓度随降雨量增加而降低，5毫米降雨量可能是大气汞完全洗脱能力的阈值。对于连续降雨事件，随着降雨过程的推进，DHg在THg中的比例可从7.1%增加到84.8%，特别是在雨水pH值影响下的HgClOH和HgCl形态。正定矩阵因子分解（PMF）分析表明，雨水中汞的主要来源是燃烧排放、海洋源、工业排放以及络合过程，分别占THg的51.4%、24.7%、12.2%和11.7%。对于特定形态，主要来源因汞形态不同而有所变化，其中燃烧排放对颗粒态汞（PHg）、HgClOH、HgCl、HgBrOH和HgBrCl各形态总量的贡献为三分之一到二分之一，其次是海洋源和工业排放。后向轨迹聚类分析表明，从山东东南部、安徽和江苏省以及京津冀地区传输来的污染气团导致了济南雨水中高汞浓度。
