Collaborative Research: Redox Processes in the Sedimentary Porewaters of Prairie Pothole Lakes: Implications for the Attenuation of Pesticides

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。草原壶穴湖（PPL）是中西部上游冰碛物的重要水文特征。 这些湖泊中的一些已经开发出独特的水化学，包括极高（10？s到100？s的毫摩尔）水平的硫酸盐。 这些沃茨中的硫酸盐在沉积物中发生还原，产生还原硫物质，既可作为亲核试剂又可作为还原剂。 在硫酸盐贫乏的湖泊中，Fe（II）和溶解性有机物（DOM）也可能成为重要的还原剂，但这将受到DOM组成的影响。迄今为止，对PPL沉积物中天然存在的还原剂的地球化学性质一无所知。 鉴于其独特的水化学，我们假设还原和非还原反应都能够非生物转化某些大量使用的农用化学品在草原坑洞沉积物。 这可能发生的程度将由存在的反应性化学物质的存在和量决定。 这些物质包括溶解的还原硫物质（二硫化物和多硫化物），以及在较小程度上缺乏高水平还原硫的坑洞中的Fe（II）和溶解有机物的组合。 我们将进行为期一年的？飞行员？在北达科他州的棉白杨湖进行研究，以了解更多关于这些系统中硫物种、Fe（II）和DOM的丰度和还原潜力。 将收集沉积物和水样，以筛选该地区常用的农药。 将在缺氧条件下仔细收集孔隙水，以量化重要还原剂的浓度，并确定其转化两种常用除草剂氟乐灵和甲草胺的能力。我们还将进行电化学研究，以评估使用伏安法的各种还原剂的形态。该试点项目的最终目标是向广大科学界证明，这些独特的水生生态系统有可能自然衰减农药。 它将为我们提供有价值的背景信息，关于沉积物孔隙水中存在的活性化学物种的类型和数量及其转化农药的潜力。 一旦掌握了这些信息，我们将能够在更大的水文背景下研究这些湖泊的作用。

AbstractThis award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Prairie pothole lakes (PPL) are important hydrologic features in the glacial till of the Upper Midwest. A number of these lakes have developed unique water chemistries, including extremely high (10?s to 100?s of millimolar) levels of sulfate. Sulfate in these waters undergoes reduction in the sediments to produce reduced sulfur species that can act as both nucleophiles and reductants. In sulfate poor lakes, Fe(II) and dissolved organic matter (DOM) may also become important reductants, but this will be influenced by DOM composition. To date nothing is known about the biogeochemistry of naturally occurring reductants in PPL sediments. Given their unique water chemistry we hypothesize that both reductive and non-reductive reactions are able to abiotically transform certain heavily used agrochemicals in prairie pothole sediments. The extent to which this can occur will be determined by the presence and amount of reactive chemical species present. These species include dissolved reduced sulfur species (bisulfide and polysulfides) and to a lesser extent a combination of Fe(II) and dissolved organic matter in potholes that lack high levels of reduced sulfur. We will conduct a one year ?pilot? study in the Cottonwood Lakes of North Dakota to learn more about the abundance and reductive potential of sulfur species, Fe(II), and DOM in these systems. Sediments and water samples will be collected to screen for pesticides commonly used in the region. Porewaters will be carefully collected under anoxic conditions to quantify the concentration of the important reductants, and determine their ability to transform two commonly used herbicides trifluralin and alachlor. We will also conduct electrochemical studies to assess the speciation of the various reductants using voltammetry. The ultimate goal of this pilot-project is to demonstrate to the scientific community at large the promise that these unique aquatic ecosystems have to naturally attenuate pesticides. It will provide us with valuable background information regarding the type and amount of reactive chemical species present in sediment porewaters and their potential to transform pesticides. Once armed with this information we will be able to examine the role of these lakes within a larger hydrologic context.