土壤-大气界面汞交换的同位素组成和分馏过程

Mercury (Hg) released from soil is an important source of atmospheric Hg in China and worldwide. Knowledge with respect to the contribution of Hg released from soil to the atmospheric Hg is an important step to establish global and regional Hg biogeochemical cycling model, and also contribute significantly to the political measures aimed at reducing and/or eliminating regional and global Hg pollutions. During the last decade, significant advances have been achieved in Hg stable isotope techniques and applications, which explore a new dimension of information on identifying the sources of Hg and tracking the transformation and transport pathways of Hg in the environments. Knowledge on isotopic compositions of Hg released from soil to the atmosphere is crucial for tracing sources of Hg in the atmosphere and establishment of global Hg isotope model. This study is aimed to investigate the isotopic compositions and fractionation of Hg exchanged between soil and atmosphere via environment controlling experiments and field measurements. For the laboratory experiments, the effects of environmental variables including sunlight irritation, temperature, soil humidity, soil humus, and soil Hg species on the isotopic compositions, fractionation and potential mechanism of Hg during the exchange between soil and atmosphere interface will be comprehensive investigated. In field experiments, we will select many typical areas of China to study the isotopic compositions of Hg exchanged between soil and atmosphere interface. This will help to establish the fingerprint database of isotopic compositions of Hg released from soil.

土壤汞释放是我国和全球大气汞的一个重要来源。正确认识土壤汞排放对大气汞的贡献是建立全球和区域汞地球化学循环模型的一个关键环节，也是开展汞污染防治必须考虑到的一个部分。汞同位素技术已经成为当前环境中汞污染源示踪和迁移转化过程研究的一个新兴研究手段。建立土壤-大气界面汞交换的同位素组成指纹数据库是利用汞同位素技术开展大气汞污染源识别和全球汞同位素模型建立的一个先决条件。本研究拟通过实验室条件控制实验和野外观测研究我国土壤/大气汞交换通量同位素组成特征和分馏过程。通过实验室条件控制实验，研究环境条件（光照，温度、土壤湿度、有机质和土壤汞形态）对土壤-大气汞交换通量过程中汞同位素分馏影响，探讨汞同位素分馏机制和内在地球化学原理。野外观测将选取我国重点和典型区域，对不同土地利用和污染类型土壤-大气汞交换通量的同位素组成进行详细研究，最终为我国土壤汞释放的汞同位素组成指纹数据库的的建立提供科学依据。

本篇报告总结了该项目（41473025）在执行过程中开展的主要工作和取得的初步研究成果。包括我们在贵州万山汞矿区、贵州省背景区和广东省背景区以及在实验室开展土壤/大气汞交换的同位素组成和分馏研究工作。通过我们的系统研究，掌握了不同污染类型土壤、不同土地利用类型土壤/大气汞交换的同位素组成和分馏过程。发现土壤/大气汞交换的同位素组成变化非常显著，且主要受到土壤汞形态、土地利用类型和环境条件（光照、土壤温度、和土壤湿度）的影响。研究成果揭示了土壤/大气汞交换的同位素组成和影响因素，为全球汞同位素循环理论体系的建立提供了重要的基础数据和理论支持。