ENHANCED POLLUTANT DESORPTION KINETICS BY BACTERIAL EXTRACELLULAR POLYMERS

污染物的命运和行为通常由以下因素共同决定 化学和生物介导的反应。两种疏水有机物质 污染物和有毒过渡金属强烈吸附在土壤上。 超级基金网站的表面。与吸附反应一起的 阻碍了污染物的扩散。通过细小的毛孔似乎可以控制 生物种群(包括土著种群)的密度 土壤微生物)暴露。增强的反应 污染物释放动力学既会加剧暴露，也可能 故意用来加强含水层清理程序。细菌 聚合物自然存在于土壤溶液中，并已有文献记载 结合过渡金属和疏水有机的性质 污染物。到目前为止的项目研究已经证明，细菌 聚合物将增强金属在多孔介质中的解吸和流动性 媒体和相关研究同样表明，细菌 聚合物将增强疏水分子的吸附和迁移性 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污染物的生物利用率 土壤中的污染物。拟议的继续这项研究将 放射性标记过渡金属的脱附动力学研究 (109Cd)和一种多核芳烃(PAH)，14C.菲， 在存在和不存在选定的胞外聚合物的情况下，包括 有几种是由本土土壤细菌分离产生的。这项研究 将使用一种新的动力学模型，该模型采用统计分布 释放速率以反映结合位点类型的多样性 控制污染物释放的共同作用的孔径大小。 使用荧光抗体(Fab)染色和 在本NIEHS的前几个阶段开发的显微放射自显影(MARG)- 赞助的研究，将被用来查看分布的 放射性标记的有机化合物、聚合物和细菌细胞 并将有助于更好地理解聚合物介导的 污染物释放机制。MARG方法也将被改编用于 评估吸附金属和多环芳烃对土壤的生物有效性 通过产生胞外物质而附着在土壤表面的细菌 聚合物。项目成果将提供有关微环境的基本信息。 以及胞外聚合物对生物多样性的宏观影响 污染物的生物有效性。在多孔介质中。一系列实验性的 尺度将从污染物的宏观行为考虑 悬浮液或吸附材料柱中的吸着剂 细菌细胞尺度的显微测量 微生境。这一实验范围将有助于 与环境有关的模型的构建和验证 对孔道内的反应和传输采用机械描述 对宏观行为进行预测的尺度。

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.