N2O as a sensitive indicator of denitrification in groundwaters

该提案旨在确定使用N2 O作为受硝酸盐（NO3-）污染的地下水含水层中反硝化作用的敏感指标。NO3-是加拿大地下水中最普遍的污染物，主要是由于通过施用合成肥料和动物粪便向农业土地大量添加氮（N）。在过去的30年里，农业用地的氮素投入急剧增加，预计这一趋势将继续下去。化粪池系统也是地下水含水层NO3-的主要来源。加拿大饮用水中NO3-的限值为10 mg N/L，加拿大水生生物指南中NO3-的限值为2.9 mg N/L。NO3-浓度超过限值会威胁人类健康和水生生物。地下水是河流的基流，地下水NO3-污染直接影响地表水资源质量和生态系统健康。为了准确地评估和预测地下水中NO3-的命运，需要关于影响地下水浓度的过程的详细信息。地下水中最重要的NO3-去除过程之一是反硝化，将NO3-还原为无害的氮气（N2）。因此，了解地下水中反硝化作用的潜力及其速率，是制定有效的地下氮源氮管理策略的核心组成部分。一氧化二氮（N2 O）是由NO3-反硝化生成N2的副产物。溶解N2 O的常规分析可以在以下浓度下进行：

This proposal aims to determine the use of N2O as a sensitive indicator of denitrification in groundwater aquifers that are contaminated with nitrate (NO3-). NO3- is the most widespread contaminant of groundwater in Canada, largely due to the extensive addition of nitrogen (N) to agricultural lands through the application of synthetic fertilizers and animal wastes. N inputs to agricultural lands have increased dramatically within the last 30 years and this trend is expected to continue. Septic systems are also a major source of NO3- to groundwater aquifers. The drinking water limit for NO3- in Canada is 10 mg N/L and the Canadian aquatic life guideline for NO3- is 2.9 mg N/L. NO3- concentrations in excess of the limits threaten human health and aquatic life. Groundwater provides the baseflow to streams and rivers, thus NO3- contamination of groundwater directly affects the quality of surface water resources and the ecosystem health. In order to accurately assess and predict the fate of NO3- in groundwaters, detailed information is require on the processes that affect is concentration in the sub-surface. One of the most important NO3- removal processes in groundwater is denitrification, which reduces NO3- to harmless nitrogen gas (N2). Understanding the potential for denitrification in groundwater, and its rate, are thus central components in the development of effective N management strategies for sources of N to the sub-surface. Nitrous oxide (N2O) is produced as a bi-product of the denitrification of NO3- to N2. Routine analysis of dissolved N2O can be done at concentrations that are