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首页> 外文OA文献 >A Gel Probe Equilibrium Sampler for Measuring Arsenic Porewater Profiles and Sorption Gradients in Sediments: I. Laboratory Development
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A Gel Probe Equilibrium Sampler for Measuring Arsenic Porewater Profiles and Sorption Gradients in Sediments: I. Laboratory Development

机译：用于测量沉积物中砷孔隙水特征和吸附梯度的凝胶探针平衡采样器：I。实验室开发

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A gel probe equilibrium sampler has been developed to study arsenic (As) geochemistry and sorption behavior in sediment porewater. The gels consist of a hydrated polyacrylamide polymer, which has a 92% water content. Two types of gels were used in this study. Undoped (clear) gels were used to measure concentrations of As and other elements in sediment porewater. The polyacrylamide gel was also doped with hydrous ferric oxide (HFO), an amorphous iron (Fe) oxyhydroxide. When deployed in the field, HFO-doped gels introduce a fresh sorbent into the subsurface thus allowing assessment of in situ sorption. In this study, clear and HFO-doped gels were tested under laboratory conditions to constrain the gel behavior prior to field deployment. Both types of gels were allowed to equilibrate with solutions of varying composition and re-equilibrated in acid for analysis. Clear gels accurately measured solution concentrations (±1%), and As was completely recovered from HFO-doped gels (±4%). Arsenic speciation was determined in clear gels through chromatographic separation of the re-equilibrated solution. For comparison to speciation in solution, mixtures of As(III) and As(V) adsorbed on HFO embedded in gel were measured in situ using X-ray absorption spectroscopy (XAS). Sorption densities for As(III) and As(V) on HFO embedded in gel were obtained from sorption isotherms at pH 7.1. When As and phosphate were simultaneously equilibrated (in up to 50-fold excess of As) with HFO-doped gels, phosphate inhibited As sorption by up to 85% and had a stronger inhibitory effect on As(V) than As(III). Natural organic matter (>200 ppm) decreased As adsorption by up to 50%, and had similar effects on As(V) and As(III). The laboratory results provide a basis for interpreting results obtained by deploying the gel probe in the field and elucidating the mechanisms controlling As partitioning between solid and dissolved phases in the environment.
机译：已开发出一种凝胶探针平衡取样器，以研究沉积物孔隙水中的砷（As）地球化学和吸附行为。该凝胶由水含量为92％的水合聚丙烯酰胺聚合物组成。在这项研究中使用了两种类型的凝胶。未掺杂（透明）凝胶用于测量沉积物孔隙水中砷和其他元素的浓度。聚丙烯酰胺凝胶还掺杂有水合氧化铁（HFO），无定形铁（Fe）羟基氧化物。当在野外部署时，掺有HFO的凝胶将新鲜的吸附剂引入地下，从而可以评估原位吸附。在这项研究中，在实验室条件下对透明和HFO掺杂的凝胶进行了测试，以在现场部署之前限制凝胶的行为。两种类型的凝胶均允许使用组成不同的溶液进行平衡，并在酸中重新平衡以进行分析。透明的凝胶准确地测量了溶液浓度（±1％），并且从掺杂HFO的凝胶中完全回收了As（±4％）。通过对重新平衡的溶液进行色谱分离，可在透明凝胶中确定砷的形态。为了与溶液中的形态进行比较，使用X射线吸收光谱法（XAS）原位测量了嵌入凝胶中的HFO吸附的As（III）和As（V）的混合物。从pH 7.1的吸附等温线获得凝胶中嵌入的HFO中As（III）和As（V）的吸附密度。当用HFO掺杂的凝胶同时平衡砷和磷酸盐时（最多吸收50倍过量的砷），磷酸盐抑制砷的吸附最多达到85％，并且对砷（Ⅴ）的抑制作用比砷（Ⅲ）强。天然有机物（> 200 ppm）最多可将As吸附量降低50％，并且对As（V）和As（III）具有相似的作用。实验室结果为解释通过在现场部署凝胶探针并阐明控制环境中固相和溶解相之间的As分配的机理提供了依据。

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