Pierce Caroline E, Furman Olha S, Nicholas Sarah L, Wasik Jill Coleman, Gionfriddo Caitlin M, Wymore Ann M, Sebestyen Stephen D, Kolka Randall K, Mitchell Carl P J, Griffiths Natalie A, Elias Dwayne A, Nater Edward A, Toner Brandy M
Department of Soil, Water, and Climate, University of Minnesota, St. Paul, Minnesota 55108, United States.
Plant and Earth Science Department, University of Wisconsin River Falls, River Falls, Wisconsin 54022, United States.
Environ Sci Technol. 2022 Jan 18;56(2):1433-1444. doi: 10.1021/acs.est.1c04662. Epub 2022 Jan 3.
We examined the composition and spatial correlation of sulfur and mercury pools in peatland soil profiles by measuring sulfur speciation by 1s X-ray absorption near-edge structure spectrocopy and mercury concentrations by cold vapor atomic fluorescence spectroscopy. Also investigated were the methylation/demethylation rate constants and the presence of AB genes with depth. Methylmercury (MeHg) concentration and organic disulfide were spatially correlated and had a significant positive correlation ( < 0.05). This finding is consistent with these species being products of dissimilatory sulfate reduction. Conversely, a significant negative correlation between organic monosulfides and MeHg was observed, which is consistent with a reduction in Hg(II) bioavailability via complexation reactions. Finally, a significant positive correlation between ester sulfate and instantaneous methylation rate constants was observed, which is consistent with ester sulfate being a substrate for mercury methylation via dissimilatory sulfate reduction. Our findings point to the importance of organic sulfur species in mercury methylation processes, as substrates and products, as well as potential inhibitors of Hg(II) bioavailability. For a peatland system with sub-μmol L porewater concentrations of sulfate and hydrogen sulfide, our findings indicate that the solid-phase sulfur pools, which have a much larger sulfur concentration range, may be accessible to microbial activity or exchanging with the porewater.
我们通过1s X射线吸收近边结构光谱法测量硫形态以及冷蒸气原子荧光光谱法测量汞浓度，研究了泥炭地土壤剖面中硫和汞库的组成及空间相关性。同时还研究了甲基化/去甲基化速率常数以及AB基因随深度的存在情况。甲基汞（MeHg）浓度与有机二硫化物在空间上相关，且具有显著正相关（<0.05）。这一发现与这些物质是异化硫酸盐还原产物一致。相反，观察到有机单硫化物与MeHg之间存在显著负相关，这与通过络合反应降低Hg(II)生物有效性一致。最后，观察到硫酸酯与瞬时甲基化速率常数之间存在显著正相关，这与硫酸酯作为异化硫酸盐还原汞甲基化的底物一致。我们的研究结果表明有机硫物种在汞甲基化过程中作为底物、产物以及Hg(II)生物有效性的潜在抑制剂的重要性。对于孔隙水中硫酸盐和硫化氢浓度为亚微摩尔/升的泥炭地系统，我们的研究结果表明，具有大得多的硫浓度范围的固相硫库可能可被微生物活动利用或与孔隙水交换。
