|Alternative Title||Speciation and gas-particle partitioning of mercury in Beijing urban atmosphere|
|Thesis Advisor||张晓山 ; 王章玮|
|Place of Conferral||北京|
|Keyword||大气汞 气粒分配 城市 大气污染 源解析 湿 沉降 atmospheric Mercury, Gas-particle Partitioning, Urban Air Pollution, Sources Analysis, Wet Deposition|
汞作为一种具有持久性和全球性的有毒重金属 正受到全球人们的广泛关注。大气中的汞依据其操作上的定义主要分为气态单质汞 GEM 颗粒态汞 PBM和活性气态汞 RGM 。 PBM和 RGM统称为活性汞 RM 。在活性汞中也有一部分汞是以高毒性的甲基汞 MeHg 形态存在。每种形态的汞都具有独特的物理和化学特征 进而导致它们在大气中具有不同的迁移和转化过程。我国已经明确将汞列为重点管控的污染物之一 但是目前 对我国大气汞污染特征以及其迁移转化的认识还非常有限 有必要通过相关研究全面、科学地揭示大气汞的变化特征、 转化过程和 来源。
As a persistent and global pervasive toxic metal mercury has drawn worldwide attention. In the atmosphere, mercury is operationally defined as three operational forms: gaseous elemental mercury (GEM), particulate bound mercury (PBM), and reactive gaseous mercury (RGM). The sum of PBM and RGM is reactive mercury (RM). Some of the RM is in the form of highly toxic methylmercury (MeHg). Each form of mercury has unique physical and chemical characteristics, which lead to different migration and transformation processes in the atmosphere. Mercury has been clearly listed as one of the key pollutants under control in China. However, at present, the understanding of atmospheric mercury pollution characteristics and its migration and transformation in China ia still limited. It is necessary to comprehensively and scientifically reveal the variation characteristics, sources and transformation mechanism of atmospheric mercury through relevant research.
Through improving the analytical method of MeHg in water, we obtained the concentration of MeHg in atmospheric fine particles, which was 0.21 ± 0.17 pg m−3, and MeHg was highly enriched in atmospheric fine particles. The seasonal mean concentrations of MeHg decreased in order: summer > autumn> spring > winter. In addition, with the increase of PM2.5 concentrations, MeHg volume concentrations elevated, whereas, the mass compositions of MeHg in PM2.5 were significantly decreased. MeHg had a high enrichment rate on atmospheric fine particles during clean days, when there was formation of MeHg and then enriched on atmospheric fine particles. With the increase of pollution, the enrichment of MeHg on atmospheric fine particles gradually decreased. Moreover, EPA PMF 5.0 receptor model was applied to apportion the sources of MeHg in atmospheric fine particles. The results show that DMeHg decomposition and MeHg surface volatilization had the largest contributions (47.8%), combustion emission contributed 18.7%, dust contributed 16.4% to MeHg, and heterogeneous reaction had relatively low contributions (13.2%).
|张欢. 北京城市大气中汞的形态及气粒分配[D]. 北京. 中国科学院生态环境研究中心,2019.|
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