Abstract
Human influenced atmospheric reactive nitrogen (RN) is impacting ecosystems in Rocky Mountain National Park (ROMO). Due to ROMO’s protected status as a Class 1 area, these changes are concerning, and improving our understanding of the contributions of different types of RN and their sources is important for reducing impacts in ROMO. In July–August 2014 the most comprehensive measurements (to date) of RN were made in ROMO during the Front Range Air Pollution and Photochemistry Éxperiment (FRAPPÉ). Measurements included peroxyacetyl nitrate (PAN), C1–C5 alkyl nitrates, and high-time resolution NOx, NOy, and ammonia. A limited set of measurements was extended through October. Co-located measurements of a suite of volatile organic compounds provide information on source types impacting ROMO. Specifically, we use ethane as a tracer of oil and gas operations and tetrachloroethylene (C2Cl4) as an urban tracer to investigate their relationship with RN species and transport patterns. Results of this analysis suggest elevated RN concentrations are associated with emissions from oil and gas operations, which are frequently co-located with agricultural production and livestock feeding areas in the region, and from urban areas. There also are periods where RN at ROMO is impacted by long-range transport. We present an atmospheric RN budget and a nitrogen deposition budget with dry and wet components. Total deposition for the period (7/1–9/30) was estimated at 1.58 kg N/ha, with 87% from wet deposition during this period of above average precipitation. Ammonium wet deposition was the dominant contributor to total nitrogen deposition followed by nitrate wet deposition and total dry deposition. Ammonia was estimated to be the largest contributor to dry deposition followed by nitric acid and PAN (other species included alkyl nitrates, ammonium and nitrate). All three species are challenging to measure routinely, especially at high time resolution.
Highlights
The nitrogen cycle has been altered by increasing production of reactive nitrogen (RN) for food production and energy (Galloway et al, 2008)
We describe measurements made during Front Range Air Pollution and Photochemistry Éxperiment (FRAPPÉ) from a ground site collocated with routine monitoring measurements at the Rocky Mountain National Park Longs Peak (ROMO-LP) field site
The pollution rose for peroxyacetyl nitrate (PAN) is shown as an example (Fig. 3) of the higher concentrations of RN species associated with upslope flow
Summary
The nitrogen cycle has been altered by increasing production of reactive nitrogen (RN) for food production and energy (Galloway et al, 2008). Emissions to the atmosphere can increase ozone and particle formation as well as contribute to elevated nitrogen deposition to land surfaces and water bodies. Elevated nitrogen deposition can alter ecosystems and the services they provide in many regions (Goulding et al, 1998; Fenn et al, 2003; Burns, 2004; Bell et al, 2017) as many ecosystems are nitrogen limited (LeBauer & Treseder, 2008). Over the past several decades, researchers in Europe, the United States, and China have focused on better understanding the interactions and changes in ecosystems that occur as a result of excess RN deposition using long-term networks. Work in the United States has focused primarily on wet nitrogen deposition measurements made by the National Atmospheric Deposition Program (NADP) (Lehmann, Bowersox & Larson, 2005). In China there has not been a long-term national deposition monitoring program; there has been an effort to implement long-term standardized nitrogen deposition measurements (Liu et al, 2011)
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