污染场地地下水中汞污染反应运移模拟

汞（Hg）是人们持续关注的全球环境污染物之一，其对地下水的污染严重威胁着与地下水相关的生态环境系统.汞在地下水系统中的物理与地球化学反应过程的准确刻画是研究汞迁移转化规律的重点和难点.基于某工业场地汞污染数据，首先采用PHREEQC研究地下水中无机二价汞的存在形态，然后利用PHT3D程序建立汞污染物反应性溶质运移二维剖面模型.该模型考虑了汞污染物在地下水系统中的对流、弥散过程及地球化学反应过程（包括水相络合作用、表面络合吸附作用及受动力学控制的氧化还原作用）.结果表明，无机二价汞的存在形态以HgCl₂和Hg（OH）Cl占主导地位，氧化还原作用是影响地下水中汞污染反应性运移的主要控制因素；另一方面，水合氧化铁HFO对汞迁移的阻滞影响较小，而溶解性有机质对汞较强的络合作用不能忽视.本文研究成果可为预测与评估特定污染场地地下水汞污染的变化趋势及制定相应的修复策略提供科学依据.

Reactive transport modeling of mercury species in the groundwater of a contaminated site

Mercury (Hg), as a common contaminant over the world, poses a significant threat to groundwater-based ecosystems. It is essential to describe the physical and geochemical processes of mercury species for the fate and transport of mercury in the aquifer. In this study, the speciation of divalent Hg(II) in the aquifer was firstly analyzed with the PHREEQC model at a contaminated industrial legacy site. Then, the reactive transport modeling based PHT3D code was constructed to simulate the transformation and transport of mercury species in the two-dimensional vertical profile. The model elucidates the physical (i.e., advection and dispersion) and geochemical processes (i.e., aqueous speciation and complexation, sorption onto HFO by surface complexation and kinetically-controlled redox processes) of mercury species in the aquifer. The results show that inorganic divalent Hg(II) (HgCl₂ and Hg(OH)Cl) predominates among all the species in the aquifer. The numerical simulation shows that redox reaction controls the fate and transport of the mercury plume. On the contrary, it is not obvious that the transport of mercury is inhibited by the sorption to HFO, while the effect of dissolved organic matter (DOM) on the transport of the mercury plume cannot be ignored. The study would help to enhance the prediction and evaluation of the transport of mercury species at specific sites, and provide the meaningful insights for the development of remediation measures.