Johs Alexander, Eller Virginia A, Mehlhorn Tonia L, Brooks Scott C, Harper David P, Mayes Melanie A, Pierce Eric M, Peterson Mark J
Environmental Sciences Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37830, USA.
Environmental Sciences Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37830, USA.
Sci Total Environ. 2019 Nov 10;690:410-416. doi: 10.1016/j.scitotenv.2019.07.001. Epub 2019 Jul 3.
Mercury (Hg) contamination of soils and sediments impacts numerous environments worldwide and constitutes a challenging remediation problem. In this study, we evaluate the impact of dissolved organic matter (DOM) on the effectiveness of eight sorbent materials considered for Hg remediation in soils and sediments. The materials include both engineered and unmodified materials based on carbon, clays, mesoporous silica and a copper alloy. Initially, we investigated the kinetics of Hg(II) complexation with DOM for a series of Hg:DOM ratios. Steady-state Hg-DOM complexation occurred within 48 to 120 h, taking longer time at higher Hg:DOC (dissolved organic carbon) molar ratios. In subsequent equilibrium experiments, Hg(II) was equilibrated with DOM at a defined Hg:DOC molar ratio (2.4 · 10) for 170 h and used in batch experiments to determine the effect of DOM on Hg partition coefficients and sorption isotherms by comparing Hg(II) and Hg-DOM. Hg sorption capacities of all sorbents were severely limited in the presence of DOM as a competing ligand. Thiol-SAMMS®, SediMite™ and pine biochar were most effective in reducing Hg concentrations. While pine biochar and lignin-derived carbon processed at high temperatures released negligible amounts of anions into solution, leaching of sulfate and chloride was observed for most engineered sorbent materials. Sulfate may stimulate microbial communities harboring sulfate reducing bacteria, which are considered one of the primary drivers of microbial mercury methylation in the environment. The results highlight potential challenges arising from the application of sorbents for Hg remediation in the field.
土壤和沉积物中的汞（Hg）污染影响着全球众多环境，构成了一个具有挑战性的修复问题。在本研究中，我们评估了溶解有机物（DOM）对八种用于土壤和沉积物汞修复的吸附剂材料有效性的影响。这些材料包括基于碳、粘土、介孔二氧化硅和铜合金的工程材料和未改性材料。最初，我们研究了一系列汞与DOM比例下汞（II）与DOM络合的动力学。在48至120小时内发生了稳态汞 - DOM络合，在较高汞：溶解有机碳（DOC）摩尔比下需要更长时间。在随后的平衡实验中，汞（II）在定义的汞：DOC摩尔比（2.4·10）下与DOM平衡170小时，并用于批量实验，通过比较汞（II）和汞 - DOM来确定DOM对汞分配系数和吸附等温线的影响。作为竞争配体，DOM的存在严重限制了所有吸附剂的汞吸附能力。硫醇 - SAMMS®、SediMite™和松木生物炭在降低汞浓度方面最有效。虽然高温处理的松木生物炭和木质素衍生碳向溶液中释放的阴离子量可忽略不计，但大多数工程吸附剂材料都观察到了硫酸盐和氯化物的浸出。硫酸盐可能刺激含有硫酸盐还原细菌的微生物群落，而这些细菌被认为是环境中微生物汞甲基化的主要驱动因素之一。结果突出了在现场应用吸附剂进行汞修复所产生的潜在挑战。
