The chemistry, sources and sinks of atmospheric reactive nitrogen

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There is growing recognition of the looming environmental crisis related to the planetary distribution of reactive nitrogen, and its impacts on environmental issues such as air quality, acid deposition, climate change, agricultural production, and biodiversity. Human activity has dramatically accelerated the rates of nitrogen fixation, leading to tripling of the emission rates of NOx and NH3 since 1860, with a projection of a further doubling by 2050 . Experts propose that the industrial rate of nitrogen fixation should be decreased by a factor of four , but the ability to meet, and rationale for, this ambitious target requires a better understanding of the variables governing the source strength of reactive nitrogen, and the cascade of impacts following emission. This research program focuses on the acquisition and interpretation of observations of atmospheric reactive nitrogen compounds, through three complementary activities: i) development of analytical techniques for field measurements, ii) collection of ambient atmospheric data, and iii) analysis of observations with a focus on process-level understanding. Our overall objective is to more fully develop the description of the sources, sinks and chemical transformations of reactive nitrogen in the atmosphere by targeting specific constituents and/or processes that are currently poorly understood. In this proposal, we describe plans to use a spectrometer on a mobile lab to identify and quantify important point and mobile sources of ammonia in southwestern Ontario. Another study will be designed to identify the variables governing the bidirectional exchange for area sources of ammonia, which are needed for air quality model development. We will expand on our analytical abilities to measure novel reactive nitrogen constituents, and interpret observations to understand the role they play in fine particle formation and heterogeneous chemistry. The role of the snowpack in acting as a source, sink, or medium for chemical transformations will also be explored during a winter season field campaign.