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。草原坑坑湖是中西部上冰期重要的水文地貌。其中一些湖泊已经形成了独特的水化学，包括极高的硫酸盐水平(10？S到100？S毫摩尔)。这些水域中的硫酸盐在沉积物中经历还原，产生还原的硫物种，既可以作为亲核剂，也可以作为还原剂。在贫硫酸盐湖泊中，Fe(II)和溶解有机质(DOM)也可能成为重要的还原剂，但这会受到DOM组成的影响。到目前为止，人们对PPL沉积物中自然产生的还原剂的生物地球化学一无所知。鉴于它们独特的水化学，我们假设还原和非还原反应都能够非生物地转化草原坑洼沉积物中某些大量使用的农用化学品。这可能发生的程度将取决于存在的活性化学物种的存在和数量。这些物种包括溶解的还原硫物种(二硫化物和多硫化物)，在较小程度上是Fe(II)和缺乏高还原硫水平的坑洞中的溶解有机物的组合。我们将进行为期一年的试点？在北达科他州的红杉湖进行研究，以更多地了解这些系统中硫物种、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杀虫剂。将在缺氧条件下仔细收集水，以量化重要还原剂的浓度，并确定它们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，用伏安法评估各种还原剂的形态。这一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必须自然地削弱杀虫剂。它将为我们提供关于沉积物孔隙水中活性化学物种的类型和数量及其转化农药的潜力的有价值的背景信息。一旦掌握了这些信息，我们就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.