Role of Microbial Sulfur Oxidation in Nitrogen Removal by Wetlands and Streams

微生物硫氧化在湿地和溪流脱氮中的作用(S.K.哈密尔顿)进入溪流的过量氮(N)，通常来自农业或城市地区的硝酸盐，造成水质问题，日益引起人们的关注。地表水和地下水在景观中的流动经常经过湿地和源头溪流，在这些地方通常可以观察到硝酸盐的去除。进一步的清除可能发生在下游蓄水池和泛滥平原。这里提出的这项研究的灵感来自于之前的研究，这些研究表明，密歇根州淡水沉积物中硝酸盐的去除与硫酸盐的产生是一致的。初步研究表明，这是一个生物过程，细菌利用硝酸盐作为氧化剂来代替氧气，通过硫磺(S)氧化。正在调查的总体假设是，与S氧化有关的硝酸盐还原是许多淡水沉积物中的一个重要过程。这样的沉积物在S并不异常高，它和硝酸盐一样有自然来源，但也是一种无处不在的污染物。S氧化剂减少硝酸盐的重要性将在密歇根州西南部的不同湿地、溪流、河流水库和泛滥平原以及作为Lotic Intersite N实验(LINX)研究地点的几个美国地点的源头溪流中进行调查。湿地和溪流对氮的去除在农业景观中特别重要，因为河流向沿海水域输出氮会造成缺氧区(例如墨西哥湾)和有害的藻类水华。湿地和溪流恢复的氮素管理应考虑微生物S和氮素转化之间的可能联系，这关系到氮去除速率的控制和被去除的氮素的最终去向。研究生培训是这项研究的组成部分，其结果将有助于推广和教学活动。

Abstract0516076 Role of microbial sulfur oxidation in nitrogen removal by wetlands and streams (S.K. Hamilton)Excessive nitrogen (N) entering streams, often originating as nitrate from agricultural or urban areas, creates problems with water-quality and is a growing concern. Surface and groundwater flow through landscapes often passes through wetlands and headwater streams, where nitrate removal is typically observed. Further removal may occur in downstream impoundments and floodplains. The research proposed here was inspired by previous studies that showed that nitrate removal from freshwater sediments in Michigan coincided with sulfate production. Pilot research indicates that this is a biological process that could occur via sulfur (S) oxidation by bacteria that utilize nitrate as an oxidant in place of oxygen. The overarching hypothesis under investigation is that nitrate reduction linked to S oxidation is an important process in many freshwater sediments. Such sediments are not unusually high in S, which like nitrate has natural sources, but also is a ubiquitous pollutant. The importance of nitrate reduction by S oxidizers will be investigated across diverse wetlands, streams, and riverine reservoirs and floodplains in southwestern Michigan, and in headwater streams at several U.S. locations that are study sites for the Lotic Intersite N Experiment (LINX). The removal of N by wetlands and streams is of particular interest in agricultural landscapes because N export by rivers to coastal waters has been implicated in creating hypoxic zones (e.g., the Gulf of Mexico) and harmful algal blooms. Wetland and stream restoration for the purpose of N management should consider the possible linkage between microbial S and N transformations, which bears on the controls of N removal rates and the eventual fate of the N that is removed. Graduate student training is integral to this research, and the results will contribute to outreach and teaching activities.