北京市大气气态汞变化特征

采用Tekran 2537X大气汞分析仪在线测量北京市城区大气中气态元素汞(GEM,简称大气汞) 浓度,研究大气汞浓度随不同气象条件的变化特征。通过分析2016年10月—2017年9月大气汞监测数据发现,该监测点全年大气汞浓度为0.48～16.25 ng/m³,均值为(3.41±1.79)ng/m³。春季、夏季、秋季和冬季大气汞浓度均值依次为2.93 、2.95、4.27、3.37 ng/m³,其中,秋季大气汞浓度明显高于其他季节 。秋季大气汞浓度显著偏高可能由不利的大气扩散条件导致。大气汞夜间浓度显著高于白天浓度。同时,将大气汞与SO₂、CO及PM_2.5进行相关性分析,发现大气汞浓度变化趋势与SO₂、CO和PM_2.5呈显著正相关。结合风向和风速进行污染来源分析,得到该点位大气汞在西南和东北方向上受人为排放源影响较大。污染源类型分析表明,冬季大气汞与CO同源性强,主要来自本地供暖用煤。

Variation Characteristics of Atmospheric Mercury in Ambient Air of Beijing

Tekran 2537X ambient mercury analyzer was used to measure gaseous elemental mercury content online in ambient air of Beijing, to investigate the characteristics of ambient mercury content changing with meteorological conditions. By analyzing atmospheric mercury monitoring data in the period from Oct. 2016 to Sept. 2017, it is found that mercury content ranged from 0.48 to 16.52 ng/m³, the mathematical average value was (3.41±1.79)ng/m³. The average values in spring, summer, autumn and winter were 2.93,2.95,4.27 and 3.37 ng/m³, respectively. Atmospheric mercury content in autumn was evidently higher than that of other three seasons, higher ambient mercury content was relevant with the poor air diffusion condition in autumn. Atmospheric mercury concentration at night was significantly higher than the mercury concentration during the day. At the same time, it displayed a significant positive correlation between atmospheric mercury concentration and SO-2, CO, PM-2.5. Combining the wind direction and wind speed to analyze the source of the pollution, atmospheric mercury at this site was greatly affected by anthropogenic sources in the southwest and northeast directions. Source type analysis indicated that atmospheric mercury in winter had a homological source with CO,which fitted well with coal combustion for heating supply.