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

摘要本奖项由2009年美国复苏与再投资法案（公法111-5）资助。草原坑湖是美国中西部北部冰原地区重要的水文特征。其中一些湖泊形成了独特的水化学成分，包括极高的(10？50到100？S（毫摩尔）硫酸盐水平。这些水域中的硫酸盐在沉积物中发生还原，产生可作为亲核试剂和还原剂的还原硫物质。在缺乏硫酸盐的湖泊中，Fe（II）和溶解有机物（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，人们对PPL沉积物中自然发生的还原剂的生物地球化学一无所知。鉴于其独特的水化学性质，我们假设还原和非还原反应都能够非生物地转化草原坑穴沉积物中某些大量使用的农用化学品。这种情况发生的程度将取决于反应性化学物质的存在和数量。这些物种包括溶解的还原硫物种（二硫化物和多硫化物），以及较小程度上的铁（II）和缺乏高水平还原硫的坑穴中溶解有机物的组合。我们将进行为期一年的试点。在北达科他州的棉杨湖进行研究，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，并确定它们转化两种常用除草剂三氟灵和甲草胺的能力。我们还将进行电化学研究，利用伏安法评估各种还原剂的形态。这个试点项目的最终目标是向整个科学界展示这些独特的水生生态系统具有自然减毒的潜力。它将为我们提供有关沉积物孔隙水中存在的活性化学物质的类型和数量及其转化农药的潜力的宝贵背景信息。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.