Collaborative Research: The missing anthropogenic N - assessing denitrification at the watershed scale

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。世界各地的湖泊，河口和沿海海洋沃茨由于过度富集氮（N）等植物营养素而退化，导致藻类大量繁殖，并最终耗尽溶解氧。 农业径流、污水排放和空气污染增加了氮向水生生态系统的输出。 对这些氮源的研究发现，河流输出的氮少于人类活动增加到河流中的氮量。 没有进入河流的氮要么以土壤或植物材料的形式储存在流域内，要么通过微生物的反硝化过程转化为氮气体并流失到大气中。 更好地了解氮在生态系统中的命运将有助于管理氮污染，但氮储存和反硝化作用从来没有在整个流域内得到充分的测量。在以前研究的基础上，该项目将采用新方法评估农业流域的脱氮作用。 反硝化作用消耗硝酸盐，从富氮流域输出的N的主要形式，并产生二氮（N2）和一氧化二氮（N2 O）气体。 该项目将测量N2和N2 O气体在地下水和土壤中的积累情况，以及硝酸盐同位素组成的变化，这是反硝化作用的标志。 这项研究将确定流域内的反硝化作用假设有很高的利率，主要是在潮湿的地区，如流缓冲区和湿地的位置。NSF资助的项目将与美国农业部资助的项目合作，通过提供关于具有高反硝化潜力的地区的信息来帮助农民选择更好的农业实践，以捕获农田损失的N。了解农业N的命运将有助于改善Choptank河流域和其他流域的管理。研究工作还将包括当地高中，本科和研究生的参与。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Lakes, estuaries, and coastal marine waters throughout the world have been degraded by over-enrichment with plant nutrients such as nitrogen (N) that cause algal blooms, and eventually deplete dissolved oxygen. Nitrogen exports to aquatic ecosystems have been increased by agricultural runoff, sewage discharges, and air pollution. Studies of these nitrogen sources have found less N exported by rivers than is expected from the amount of N added to the the rivers by human activities. The N that does not enter rivers is either stored within the watersheds as soil or plant materials or converted to N gases by the microbial process of denitrification and lost to the atmosphere. A better understanding of the fate of N in ecosystems would help manage N pollution, but N storage and denitrification have never been adequately measured within an entire watershed. Building on previous research, this project will apply new methods to assess denitrification in agricultural watersheds. Denitrification consumes nitrate, the main form of N exported from N-enriched watersheds, and produces dinitrogen (N2) and nitrous oxide (N2O) gases. The project will measure accumulations of N2 and N2O gases in groundwater and soils, and changes in the isotopic composition of nitrate that are indicative of denitrification. The study will identify locations within watersheds where denitrification is hypothesized to have high rates, primarily in damp areas such as stream buffers and wetlands. The NSF-funded project will collaborate with a USDA-funded project in assisting farmers to select better agricultural practices by supplying information on areas with high denitrification potential for capturing N lost from croplands. Knowing the fate of agricultural N will help improve the management of the Choptank River watershed and other basins. The research efforts will also include participation of local high school, undergraduate, and graduate students.