沉积物和土壤孔隙水中甲基汞的一种新型平衡被动采样装置的研制

在这项研究中，我们探索了利用疏水性有机化学品（HOCs）开发的策略对甲基汞（MeHg）进行平衡被动采样的概念。被动取样应允许基于平衡分配到取样器中的基础上预测沉积物孔隙水（MeHgCL）中MeHg的化学不稳定部分的浓度，而无需模拟通过取样器材料的扩散速率。我们的目标是确定具有模拟甲基汞在动物和沉积物中分配的潜力的取样器材料，并在适合于原位取样器的时间框架内提供可逆吸附。测试的候选材料包括一系列嵌有合适的甲基汞吸收剂的聚合物。最有潜力的是琼脂糖包埋的活性炭（AC）、琼脂糖包埋的巯基自组装膜（SMS）和半胱氨酸功能化聚对苯二甲酸乙二醇酯（PET），对MeHgOH和MeHg与溶解有机物（Suwannee河腐殖酸）的络合作用，测井采样器的水分配系数（Kpw）为2.8～5。沉积物中采样器的平衡时间约为1～2周。琼脂糖包埋AC对MeHg积累机制的研究表明，样品受MeHg与AC颗粒相互作用的动力学影响，而不受凝胶扩散的限制。AC显示Hg和MeHg的相对快速解吸，表明该吸附剂能够进行可逆的平衡测量。在沉积物:水的微观结构中，用等温线校准的被动取样器测得的孔隙水浓度与直接测得的浓度在2倍（未经修正的沉积物）或4倍（经修正的AC沉积物）内一致。这项工作为甲基汞的被动采样提供了一种潜在的新途径。

Development of a novel equilibrium passive sampling device for methylmercury in sediment and soil porewaters

In this study we explore the concept of equilibrium passive sampling for methylmercury (MeHg) using the strategy developed for hydrophobic organic chemicals (HOCs). Passive sampling should allow prediction of the concentration of the chemically labile fraction of MeHg in sediment porewaters (MeHgCL) based on equilibrium partitioning into the sampler, without modeling diffusion rates through the sampler material. Our goals were to identify sampler materials with the potential to mimic MeHg partitioning into animals and sediments and provide reversible sorption in a time frame appropriate for in situ samplers. Candidate materials tested included a range of polymers embedded with suitable sorbents for MeHg. The most promising were activated carbon (AC) embedded in agarose, thiol-SAMMS (self-assembled monolayers on mesoporous supports) embedded in agarose, and cysteine-functionalized polyethylene terephthalate (PET), which yielded log sampler-water partition coefficients (Kpw) of 2.8 to 5 for MeHgOH and MeHg complexed with dissolved organic matter (Suwannee River Humic Acid). Sampler equilibration time in sediments was approximately 1 to 2 weeks. Investigation of the MeHg accumulation mechanism by AC embedded in agarose suggested sampling was kinetically influenced by MeHg interactions with AC particles and not limited by diffusion through the gel for this material. AC exhibited relatively rapid desorption of Hg and MeHg, indicating that this sorbent is capable of reversible, equilibrium measurements. In sediment:water microcosms, porewater concentrations made with isotherm-calibrated passive samplers agreed within a factor of two (unamended sediment) or four (AC-amended sediment) with directly measured concentrations. This work demonstrates a potential new approach to passive sampling of MeHg.