华东高山背景点大气气态汞含量与传输特征

利用高时间分辨率自动测汞仪（Tekran 2537B）于2017年6月~2018年5月对武夷山气态元素汞（GEM）进行了连续1a的观测.结果表明,武夷山GEM年均浓度为（1.70±0.43）ng/m³,稍高于北半球背景值,表明武夷山受到一定程度的大气汞污染.GEM浓度表现为冬季>秋季>春季>夏季,季风和风速是影响武夷山GEM季节变化的主要因素.武夷山四季GEM表现为不同的日变化特征,早上8：00之后,春秋季GEM继续呈现下降趋势,其他季节则呈现先升后降再上升,并在晚上不同时刻出现峰值.GEM值白天低于晚上,这与风速和汞的长距离迁移有关.后向轨迹和浓度权重轨迹分析结果表明,偏西风背景下污染气团经江西向武夷山输送是大气汞迁移的主要路径,而江西和福建中北部为武夷山大气汞污染的潜在源区.△GEM/△CO值表明武夷山GEM汞污染主要来源于人为工业排放,生物质燃烧贡献较弱.

Level and transport characteristic of gaseous elemental mercury at a background mountain site of East China

Gaseous elemental mercury (GEM) was monitored continuously at Wuyi Mountain using the high-resolution automatic atmospheric mercury vapor analyzer (Tekran 2537B) from June 2017 to May 2018. The annual mean concentration of GEM was (1.70±0.43)ng/m³, slightly higher than background level in the northern hemisphere, suggesting that the atmosphere of the Wuyi Mountain was polluted to some extent. The GEM varied in different seasons, with the highest concentration observed in winter, followed by fall, spring, and summer. The monsoon and wind speed contributed mostly to the seasonal variation. Different diurnal variation characteristics of GEM were found in four seasons. In spring and autumn, GEM continued to decrease after 8:00am, however, in other seasons, GEM showed "increase-decrease-increase" and peaked at different times in nighttime. The GEM in the daytime were generally higher than those in the nighttime, which may related to the wind speed and long distance transport of mercury. Backward trajectory and concentration-weighted trajectory indicated that polluted air masses to the Wuyi Mountain via Jiangxi province under westerly wind was the main path of atmospheric mercury migration. In addition, Jiangxi province and north-central Fujian province were the potential source areas of GEM at the Wuyi Mountain. The values of △GEM/△CO suggested that mercury pollution at the Wuyi Mountain was mainly affected by anthropogenic mercury emissions, while biomass burning did little contribution.