N2O as a sensitive indicator of denitrification in groundwaters

N2O 作为地下水反硝化的敏感指标

• 批准号: 357056-2007
• 负责人: Robertson, William
• 金额: $ 5.25万
• 依托单位: University of Waterloo
• 依托单位国家: 加拿大
• 项目类别: Strategic Projects Supplemental Competition
• 财政年份: 2007
• 资助国家: 加拿大
• 起止时间: 2007-01-01 至 2008-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=365994
• 关键词: N2O; sensitive; indicator; denitrification; groundwaters

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 are10,000 times lower than for typical nitrate analysis. Therefore, the detection of denitrification in groundwater by the accumulation of excess N2O is far more sensitive than analysing for the disappearance of NO3-. The use of N2O to assess denitrification activity in groundwater systems has not been previously explored. Results of this proposal will have implications for groundwater management, especially in designing wellhead protections schemes. It is expected that this research will produce a new method for the identification of denitrification activity in aquifers where analysis of NO3- concentrations would otherwise be inconclusive.

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。为了准确评估和预测地下水中NO3-的命运，需要有关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，了解地下水反硝化的潜力及其速率是针对地下氮源制定有效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。溶解的N2 O的常规分析可以在比典型的硝酸盐分析低10,000倍的浓度下进行。因此，通过过量N2 O的积累来检测地下水中的反硝化作用远比分析NO3-的消失更敏感。使用N2 O来评估地下水系统中的反硝化活性以前没有进行过探索。该建议的结果将对地下水管理产生影响，特别是在设计井口保护计划方面。预计这项研究将产生一种新的方法，用于识别含水层中的反硝化活性，否则NO3-浓度的分析将是不确定的。