中国地区大气汞的数值模拟研究

结合中国地区的汞排放,利用引入大气汞化学反应机制和干沉降模型的区域大气环境模式系统(Regional Atmospheric Environment Model System,Reg AEMS),对中国地区大气汞化物浓度和干沉降通量的时空分布特征进行模拟研究。研究结果表明,中国地区年均气态零价汞Hg0、氧化汞Hg O、氢氧化汞Hg(OH)2、氯化汞Hg Cl2和颗粒态汞HgP的沉降量分布类似。除西部、西北部地区Hg0的浓度较低外(0.5 ng·m-3),其他地区均高于全球背景浓度。各类汞化物浓度的季节变化明显,8月最低,2、3月最高。一次汞源区附近汞浓度随高度递减,在离源较远的地区,高层汞浓度较高。气态零价汞的干沉降速度的季节变化最明显,其干沉降通量在夏季最高。模拟区域中气态零价汞、氧化汞和颗粒态汞的年干沉降量分别为163.9、7.43和32.2 t。

Numerical Study on Atmospheric Mercury over China

Atmospheric mercury chemistry and dry deposition were incorporated into Regional Atmospheric Environment Model (RegAEMS) given on mercury emission inventory, the spatiotemporal variations of atmospheric mercury and its total deposition flux were investigated. Results from RegAEMS indicated that high annual mean Hg⁰, HgO, Hg(OH)₂, HgCl², and Hg^p loadings appeared in the regions with large mercury emissions, in most regions over China exceeded its global background level of 1.0 ng?m^-3 except those in West and Northwest China. There were significant seasonal variations for surface loadings of these five kinds of mercury, and they were the highest in February and March while are the lowest in August. Profiles of annual mean mercury loading in different sites over the regions indicate that there were high concentrations of primary mercury (Hg⁰ and Hg^p) in low levels for the sites near the sources. In remote sites, the loading peaks of these kinds of mercury appeared in higher levels. Due to the strongest removing rates of Hg⁰, its dry deposition flux was much larger in summer. Simulated total deposited Hg⁰, HgO, and Hg^p over the region were 163.9, 7.43, and 32.2 t in 2004.