U.S. Environmental Protection Agency, Office of Research and Development, National Risk Management Research Laboratory, 26 W. Martin Luther King Drive, Cincinnati, OH 45268, USA.
Environ Res. 2013 Aug;125:41-51. doi: 10.1016/j.envres.2013.03.010. Epub 2013 Jun 2.
The function and longevity of traditional, passive, isolation caps can be augmented through the use of more chemically active capping materials which have higher sorptive capacities, ideally rendering metals non-bioavailable. In the case of Hg, active caps also mitigate the rate and extent of methylation. This research examined low cost, readily available, capping materials for their ability to sequester Hg and MeHg. Furthermore, selected capping materials were evaluated to inhibit the methylation of Hg in an incubation study as well as the capacity of a selected capping material to inhibit translocation of Hg and MeHg with respect to ebullition-facilitated contaminant transport in a column study. Results indicated that bauxite had a better capacity for mercury sorption than the other test materials. However, bauxite as well as soil capping materials did not decrease methylation to a significant extent. Materials with larger surface areas, higher organic matter and acid volatile sulfide (AVS) content displayed a larger partitioning coefficient. In the incubation experiments, the presence of a carbon source (lactate), electron acceptor (sulfate) and the appropriate strains of SRB provided the necessary conditions for Hg methylation to occur. The column study showed effectiveness in sequestering Hg and MeHg and retarding transport to the overlying water column; however, disturbances to the soil capping material resulting from gas ebullition negated its effectiveness.
传统的、被动的、隔离的盖帽的功能和寿命可以通过使用具有更高吸附能力的更具化学活性的盖帽材料来增强，理想情况下使金属变得不可生物利用。对于汞，活性盖帽还可以减缓甲基化的速度和程度。本研究考察了低成本、易得的盖帽材料，以评估它们螯合汞和甲基汞的能力。此外，还评估了选定的盖帽材料，以抑制在孵育研究中汞的甲基化以及选定的盖帽材料抑制汞和甲基汞迁移的能力，以了解在柱研究中沸腾促进的污染物迁移。结果表明，矾土对汞的吸附能力优于其他测试材料。然而，矾土和土壤盖帽材料并没有显著降低甲基化程度。表面积较大、有机质和可挥发酸硫（AVS）含量较高的材料显示出较大的分配系数。在孵育实验中，存在碳源（乳酸盐）、电子受体（硫酸盐）和合适的硫酸盐还原菌（SRB）菌株为汞甲基化的发生提供了必要的条件。柱研究表明，它能有效地螯合汞和甲基汞，并阻止其向覆盖水层的迁移；然而，由于气体沸腾对土壤盖帽材料的干扰，其有效性被否定了。
