上海市夏季湿沉降汞的时空分布规律及其影响因素

为研究上海市夏季湿沉降汞的时空分布特征,按月采集了2008年夏季(6～8月)5个采样点的大气湿沉降样品,经过王水+BrC1水浴消解、SnCl2还原后,用原子荧光测汞仪测试了样品中的总汞、溶解态汞和颗粒态汞浓度并对结果加以分析。结果表明,上海市夏季各采样点湿沉降中总汞、溶解态汞和颗粒态汞的平均浓度变化范围大,分别为0.13～0.39μg/L、0.04～0.22μg/L、0.09～0.18μg/L,总体上各形态汞的浓度都较高。湿沉降总汞的浓度在时间上表现为6月份较低而7、8月份较高的特征,在空间上是浦东最高,普陀其次,宝山最低;颗粒态汞占总汞的比例大,并且在不同降水类型中所占总汞的比例不同,在梅雨期锋面雨中所占比例较少而在对流雨中所占比例较大;总汞的沉降量与降水量成明显的正相关关系。大气湿沉降中各形态汞的浓度受控因素较多,其中在重要排放源和市中心下风向地区汞的浓度偏高,这需要在节能减排上下功夫,从源头治理汞的污染。

Spatio-temporal Distribution Law of Mercury in Wet Deposition and Its Influencing Factors in Summer of Shanghai

Spatio-temporal distribution law of mercury in wet deposition in summer,Shanghai was studied.Concentrations of Hg were measured by atomic fluorescence just after being waterbath digested by HCl+HNO3+BrCl and reduced by SnCl2 in precipitation collected from 5 sites in Shanghai from June to August,2008.Average concentration of total Hg ranged from 0.13 to 0.39μg/L,dissolved Hg from 0.04 to 0.22μg/L and particulate Hg from 0.09 to 0.18μg/L.Results indicated that concentrations of all species of Hg in Shanghai were higher than other areas,with temporal distribution of concentrations of Hg in June higher than in July and August.In spatial distribution,concentration of Hg in Pudong Site was the highest,and followed by Putuo and Baoshan.Particulate Hg does not take a high proportion in total Hg,and varies in different types of wet deposition.The proportion was higher in convection rain compared with in front rain in season of plum rain.Conspicuous positive relationship can be seen between total Hg deposition and volume of rainfall.Energy saving and emission cutting should contribute great to the reduction of emission of Hg due to important emission source and wind direction.