ENHANCED POLLUTANT DESORPTION KINETICS BY BACTERIAL EXTRACELLULAR POLYMERS

污染物的命运和行为往往取决于耦合的 化学和生物介导的反应。疏水有机 污染物和有毒的过渡金属被强烈地吸附到土壤中 出现在超级基金网站上。 吸附反应与 污染物扩散受阻。通过小孔似乎控制 生物种群（包括土著） 土壤微生物）暴露。这些反应可以增强 污染物释放动力学既可以加剧暴露， 有意用于加强含水层清理程序。 细菌 聚合物天然存在于土壤溶液中， binding.properties，适用于过渡金属和疏水有机 污染物。迄今为止的项目研究表明， 聚合物将用于增强多孔介质中的金属解吸和流动性， 媒体和相关研究同样表明， 聚合物将起到增强疏水性物质的吸附和流动性的作用， 多孔介质中的有机污染物因此，细菌聚合物可能 提高有毒过渡金属和有机物的生物利用度 土壤中的污染物建议继续进行这项研究， 量化放射性标记的过渡金属的解吸动力学 （109 Cd）和多核芳烃（PAH），14 C.菲， 在存在和不存在选定的细胞外聚合物的情况下，包括 有几种是由本土土壤细菌的分离物产生的。研究 将使用一种新的动力学模型， 释放速率，以反映结合位点类型的多样性， 这些孔径共同作用以控制污染物释放。 使用荧光抗体（Fab）染色的技术和 显微放射自显影（MARG），在本NIEHS的前几个阶段开发- 赞助的研究，将被用来查看分布 放射性标记的有机化合物、聚合物和细菌细胞 微尺度，并将提供更好的理解聚合物介导的 污染物释放机制。MARG方法也将进行调整， 在评估吸附金属和多环芳烃对土壤的生物利用度时， 通过产生细胞外基质粘附在土壤表面的细菌 聚合物该项目的结果将产生关于微观的基本信息， 和宏观尺度的影响，胞外聚合物对 污染物的生物利用度。在多孔介质中。一系列实验 从污染物的宏观行为考虑尺度 在吸附剂材料的悬浮液或柱中的吸附剂， 显微镜下测量细菌细胞的大小， 微生境实验规模的这一范围将有助于 建立和验证与环境有关的模型， 采用机理描述的反应和运输的孔隙 来预测宏观行为。

The fate and behavior of pollutants is often dictated by the coupling of chemical and biologically-mediated reactions. Both hydrophobic organic pollutants and toxic transition metals are strongly sorbed to soil surfaces at Superfund sites. Sorption reactions together with the hindered diffusion of pollutants. through small pores appear to control the concentrations to which biological populations (including indigenous soil microorganisms) are exposed. Reactions which act to enhance pollutant release kinetics can both exacerbate exposure and can be deliberately employed to enhance aquifer clean-up procedures. Bacterial polymers naturally occur in soil solution and have documented binding.properties for both transition metals and hydrophobic organic contaminants. Project research to date has demonstrated that bacterial polymers will act to enhance metal desorption and mobility in porous media, and related research has similarly shown that the bacterial polymers will act to enhanced sorption and mobility of hydrophobic organic pollutants in porous media. Therefore, bacterial polymers may enhance the bioavailability of both toxic transition metals and organic contaminants in soil. The proposed continuation of this research will quantify the desorption kinetics of a radio-labeled transition metal (109Cd) and a polynuclear aromatic hydrocarbon (PAH), 14C.phenanthrene, in the presence and absence of selected extracellular polymers, including several produced by isolates of indigenous soil bacteria. The research will use a novel kinetic model that employs a statistical distribution of release rates to reflect the multiplicity of binding site types and pore sizes that collectively act to control contaminant release. Techniques using fluorescent antibody (Fab) staining and microautoradiography (MARG), developed during prior phases of this NIEHS- sponsored research, will be employed to view the distribution of radiolabeled organic compounds, polymers, and bacterial cells at the microscale and will provide an improved understanding of polymer-mediated contaminant release mechanisms. MARG methods will also be adapted for use in assessing the bioavailability of sorbed metals and PAH to soil bacteria that adhere to soil surfaces through production of extracellular polymers. The project results will yield basic information on the micro- and macro-scale influence of extracellular polymers on the bioavailability of contaminants. in porous media. A range of experimental scales will be considered from the macroscopic behavior of pollutant sorbates in suspensions or columns of sorbent material to direct microscopic measurements at the scale of bacterial cells in their microhabitats. This range in experimental scale will facilitate construction and verification of environmentally relevant models that employ mechanistic descriptions of reaction and transport at the pore scale to make predictions of macroscopic behavior.