上海崇明地区大气分形态汞污染特征

2014年3月~2015年2月对上海崇明东滩湿地公园的气态零价汞(GEM)、活性气态汞(RGM)和颗粒态汞(PBM)分别进行了为期1a的连续监测.GEM、RGM和PBM的年平均浓度分别为(2.75±1.13)ng·m~(-3)、(13.39±15.95)pg·m~(-3)和(21.89±40.42)pg·m~(-3),明显高于对应北半球背景值浓度.GEM浓度在夏季最高(3.65 ng·m~(-3)),受自然源排放影响较大,秋冬季较低,受人为源排放影响较大;RGM浓度在春季最高,冬季最低,主要受风速风向的影响;PBM浓度在秋冬季节明显高于其他季节,受秋冬季节较多的细颗粒物重污染过程的影响.GEM和PBM浓度均夜间较高,白天较低,主要受空气气团混合作用影响.RGM浓度在下午较高,主要是由于GEM在下午的光氧化作用加强,利于RGM的生成.GEM和PBM浓度在偏西风向上浓度较高,受上海、江苏等地人为源排放影响较大.RGM浓度在东南风向上浓度明显高于其他方向,这是因为RGM主要来源为人为排放,其浓度受风速影响较大,东南风向上平均风速较小,持续的弱风及停滞的空气不利于RGM的扩散.

Characteristics of Speciated Atmospheric Mercury in Chongming Island, Shanghai

Continuous monitoring of gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and particulate mercury (PBM) was conducted in the Dongtan wetland park in Chongming Island, Shanghai from March 2014 to February 2015. The average concentrations of GEM, RGM, and PBM were (2.75±1.13) ng·m^-3, (13.39±15.95) pg·m^-3, and (21.89±40.42) pg·m^-3, respectively, higher than the background concentrations of Northern Hemisphere. The atmospheric mercury showed obvious seasonal variations, with the highest seasonal average GEM concentration in summer (3.65 ng·m^-3), which was mainly influenced by natural sources, while lower GEM concentrations appeared in autumn and winter influenced mainly by anthropogenic sources. The concentration of RGM was highest in spring and lowest in winter, mainly influenced by the wind direction, while PBM showed higher concentrations in autumn and winter, when heavy fine particulate pollution episodes occurred frequently. The concentrations of GEM and PBM were generally elevated in nighttime and lower in daytime caused by the mixing condition of the air masses. Most of the high RGM concentration values occurred in the afternoon of all seasons due to the higher atmospheric oxidation. The concentrations of GEM and PBM were higher in the west wind due to the emission from anthropogenic sources in Shanghai, Jiangsu, etc. The RGM concentration in southeast wind was obviously higher than those in other wind directions. The RGM was mainly from the anthropogenic sources, and the smaller wind in the southeast direction was against the dispersion of RGM.