Regulation of reactive nitrogen transport and transformation in contaminated environments

污染环境中活性氮运输和转化的调控

• 批准号: RGPIN-2015-03920
• 负责人: Kellman, Lisa
• 金额: $ 1.6万
• 依托单位: St. Francis Xavier University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=655257
• 关键词: Regulation; reactive; nitrogen; transport; transformation

Agricultural activities have led to a rapid growth in the release of a number of chemically, radiatively, and biologically reactive nitrogen (N) species within terrestrial watersheds. These reactive N compounds play important roles in the deterioration of water quality through leaching losses from soil surfaces of aqueous inorganic N species, including ammonium (NH4+) and nitrate (NO3-), and through changes to the climate system via increased emissions of nitrous oxide (N2O), a powerful and long-lived greenhouse gas and stratospheric ozone depleting compound. Nitrous oxide is a product of the transformation of both NH4+ and NO3- in watersheds, so watershed zones that facilitate improved water quality through losses of these species may show enhanced emissions of this gas. These N transformations and exchanges are closely regulated by redox conditions and temperature when inorganic N is abundant. ***Emissions of N2O in agricultural watersheds arising from leached N are seldom quantified in field studies, which tend to focus upon the point of immediate impact (i.e., soil surfaces). However, a significant proportion of reactive N released to soils through anthropogenic land use activities is leached into linked aquatic systems, where it is subsequently removed or transformed. Nitrogen transformation processes that generate N2O can be differentiated by their unique isotopic fingerprints (i.e., d15N and d18O). As stable isotopes provide the only means by which N2O can be apportioned to sources and/or transformation processes in the field, they are likely to factor in as crucial monitoring tools over the next decade, particularly in light of recent advances in the development of field portable and high-sensitivity N2O isotopic analyzers. ***The objective of the proposed research program is to quantify rates and characterize isotopic patterns of reactive N transformations that lead to N2O emissions from leached N in temperate zone agriculturally dominated watersheds experiencing elevated N loading. This will be accomplished by: selecting field sites that provide model systems for characterizing leached N loading conditions associated with agricultural activities; investigating the transport, transformation, and isotopic signals of aqueous inorganic N compounds that are precursors to N2O at these sites; studying the rates and isotopic signatures associated with N2O released under varying redox states, thermal conditions, and N loading levels at these sites; placing N2O release in the context of overall global warming potentials for the watershed points of study through concurrent analysis of carbon-based greenhouse gases; and identifying the utility of the observed chemical patterns for use as longer-term N2O emission monitoring and mitigation tools.**

农业活动导致陆地流域内许多化学、辐射和生物活性氮 (N) 物质的释放迅速增加。 这些活性氮化合物通过土壤表面水性无机氮（包括铵 (NH4+) 和硝酸盐 (NO3-)）的淋滤损失，以及一氧化二氮排放增加而改变气候系统，在水质恶化中发挥着重要作用。 (N2O)，一种强大且长寿命的温室气体和平流层臭氧消耗化合物。一氧化二氮是流域中 NH4+ 和 NO3- 转化的产物，因此通过这些物种的损失促进水质改善的流域区域可能会显示出这种气体排放量的增加。当无机氮丰富时，这些氮的转化和交换受到氧化还原条件和温度的密切调节。 ***农业流域中因氮淋滤而产生的 N2O 排放很少在实地研究中进行量化，这些研究往往侧重于直接影响点（即土壤表面）。 然而，通过人为土地利用活动释放到土壤中的活性氮的很大一部分被浸入相关的水生系统中，随后被去除或转化。产生 N2O 的氮转化过程可以通过其独特的同位素指纹（即 d15N 和 d18O）来区分。 由于稳定同位素提供了将 N2O 分配到现场来源和/或转化过程的唯一方法，因此它们很可能成为未来十年的关键监测工具，特别是考虑到现场开发的最新进展便携式高灵敏度 N2O 同位素分析仪。 ***拟议研究计划的目标是量化活性氮转化的速率并表征其同位素模式，这些转化导致温带农业为主的流域中经历氮负荷升高的淋滤氮产生一氧化二氮排放。 这将通过以下方式实现： 选择提供模型系统的现场地点，以表征与农业活动相关的淋滤氮负荷条件；研究水性无机氮化合物的传输、转化和同位素信号，这些无机氮化合物是这些位点 N2O 的前体；研究这些地点在不同氧化还原状态、热条件和氮负载水平下释放的 N2O 的速率和同位素特征；通过同时分析碳基温室气体，将 N2O 释放置于研究分水岭的总体全球变暖潜力的背景下；并确定观察到的化学模式作为长期 N2O 排放监测和缓解工具的效用。**