Nitrogen Deposition: Measurement Techniques and Field Studies AT 621 Special Lecture November 26, 2012 Ashley Evanoski-Cole

Atmospheric Nitrogen Pathways May increase with climate change (Civerolo, 2007) Eutrophication Decrease biodiversity Acidification - Cation exchange in soils - Lakes/streams acidification http://nadp.sws.uiuc.edu/lib/brochures/nitrogen.pdf

Pathways for Ammonia (NH3) NH3 Sources 1. Livestock 2. Ammonification of Humus 3. Emission from Soils 4. Fertilizer 5. Industrial Emissions Chemical Processing NH3(g) → NH3(aq) NH3(aq) + H+ ↔ NH4+(aq) Particle Formation NH4+(aq) + NO3-(aq) ↔ NH4NO3(aq) Dry or Wet Deposition Transport τ ~ 10 days Dry Deposition

Pathways for NOx NOx Sources 1. Fossil fuel combustion 2. Biomass Burning 3. Soils 4. Lightning Chemical Processing (day) NO2(g) + OH → HNO3(g) HNO3 dry and wet deposition Chemical Processing (night) NO2 + NO3 ↔ N2O5 N2O5(g) H2O(aq) → HNO3(aq) Ozone Formation Transport (lifetime highly variable)

Wet Deposition Particles and gases that deposit to the surface via rain, snow or fog In cloud nucleation Particle / gas scavenging How is it measured? Analyze species in precipitation samples Explain precip bucket (and dry dep bucket)

Dry Deposition Gases and particles that directly transfer to the surface by diffusion (gases and small particles) or gravitational settling (larger particles) How is it measured? Directly: Measure the vertical flux of species of interest or measuring amount of species collected on a surface, such as on a filter Indirectly: Flux measurements are derived from measurements of mean concentration or vertical gradients of mean concentrations (this method requires more assumptions) Direct methods include measuring deposition on surrogate surfaces (filter) or natural surfaces such as leaf-washing, snow analysis, a “chamber,” eddy correlation using vertical winds, also eddy accumulation (one filter or chamber right side up, one upside down, to measure both the flux up and flux down to get the next flux of a species) CASTNet site at Penn State University

NADP Monitoring Network National Atmospheric Deposition Program Started measurements in 1978 measuring only weekly precipitation data in the National Trends Network (NTN). Now monitoring sites for daily precipitation, mercury in precipitation (wet deposition), atmospheric mercury (dry deposition), and ammonia Weekly precipitation monitoring sites (NTN)

CASTNet Monitoring Network Clean Air Status and Trends Network Established in 1991 to measure acid deposition Measure ambient concentrations and dry deposition of SO2, HNO3, (gases) and SO42-, NH4+, NO3-, (particles) Use indirect method by measuring concentration and estimated deposition velocities

H+ Mention acid sensitive areas (NE) because of low acid neutralizing capacity

NO3-

NH3 http://nadp.sws.uiuc.edu/ntn/annualmapsbyyear.aspx

Percent Change in N deposition Ammonia Lehmann et al., 2005

(Ammonium and nitrate) Inorganic Nitrogen (Ammonium and nitrate)

ROMANS Field Campaigns Rocky Mountain Atmospheric Nitrogen and Sulfur (RoMANS) study Multi-year study between 2006-2010 Collaboration between CSU, CIRA, NPS, many other groups Main Objectives were to: Measure N and S deposition Characterize meteorological conditions associated with high N and S concentrations Identify source regions and emissions within Colorado and out of state transport

Measurements Gas and Particle Chemistry Precipitation Chemistry 24 hr gaseous species: NH3, HNO3, SO2 24 hr Particle Chemistry: Na+, NH4+, K+, Mg2+, Ca2+, Cl-, NO3-, SO42- 15 min. Particle Chemistry: same as above Weekly PM2.5 water soluble organic nitrogen Precipitation Chemistry ions above and organic nitrogen In RMNP - meteorological measurements from the National Park Service Air Resources Division In GTNP – we operated three different met. stations [slide from K. Benedict]

Concentrations Across Colorado Seasonal trends Large differences between sites for gas phase species Concentrations are more similar of aerosol species – often concentrations at RMNP are similar to those on the plains f(T, RH) NH3(g) + HNO3 (g) ⟺ NH4NO3 (p) [slide from K. Benedict]

Winds and Concentrations Spring Fall [slide from K. Benedict]

Critical load describes the point at which a natural system is impacted by air pollution. They can be used to assess ecosystem health, guide resource management decisions, and evaluate the effectiveness of emissions reduction strategies. http://nadp.sws.uiuc.edu/lib/brochures/criticalloads.pdf http://www.nature.nps.gov/air/Studies/criticalloads/criticalLoadExplain.cfm

Nitrogen Deposition & Critical Load All Pathways Annual Deposition: 3.46 kg N·ha-1 Set Critical Load 2008-2009 Critical Load Comparison Dry NH3 and Wet ON 1.5 1.97 1.37 (Wet deposition of NH4+ + NO3-) Are dry deposition of NH3 and wet deposition of ON important in other areas? [slide modified from K. Benedict]

Results and Potential Future Research Results of RMNP study were used to form a nitrogen deposition reduction plan for the state of Colorado In Future Studies: Determine importance of each contribution to dry and wet deposition in other sites Grand Teton NP (agricultural emissions to the east) Theodore Roosevelt NP in North Dakota (oil and gas drilling emissions)