From Ammonia to PM 2.5 Brent Auvermann Texas Cooperative Extension Texas Agricultural Experiment Station Amarillo, TX

Acknowledgments Spyros Pandis, atmospheric chemist, CMU Rich Scheffe, USEPA-OAQPS N. Andy Cole and Rick Todd, USDA-ARS David Parker, agricultural engineer, TAMU Saqib Mukhtar, agricultural engineer, TAMU

Forms of Atmospheric Nitrogen N2N2 NH 3 N2ON2ONO NO x

NH 3 – What’s the Big Deal? Superfund/EPCRA – Federal litigation on broad CAFO front –Multiple species –Multiple states –Do the math NH 3 + (SO 4, NO 3 or Cl) >> PM 2.5 NH 3 + PM >> synergistic effect on animal pulmonary health >> effect on human health?

Open-Lot Systems Beef feedyards –Animal spacing ft 2 /hd –Excreted N 90% of N consumed in feed (Bierman et al., 1996) Open-lot dairies –Animal spacing ft 2 /hd –Excreted N 70% of N consumed in feed (Van Horn et al., 1996)

Fate of Excreted N in Open-Lot Systems Collected in solid manure –Spread –Stored (stockpiles, mounds, other) –Composted and spread Remains on corral surface –Stable if it remains dry –Runs off into holding pond Volatilized as NH 3 (g) directly –Increases with wet/dry cycling

Extinction efficiencies for ubiquitous particle types (Malm, 1999) Particle Type Dry Extinction Efficiency (m 2 /g) Sulfates3.0 Organics3.0 Elemental Carbon10.0 Nitrates3.0 Soil Dust1.25 Coarse Particles0.6 Feedyard PM 10 /TSP /

Air Pollution in Pittsburgh July 2, 2001 PM 2.5 =4  g m - 3 July 18, 2001 PM 2.5 =45  g m - 3 (Adapted from Pandis, 2003)

Nucleation In aqueous solution, two or more species react to form a low-solubility product known as a precipitate Because the precipitate has relatively low solubility, it immediately forms a solid particle in aqueous suspension The particle provides a surface on which more of these reactions can occur

Interactions between Fine PM and Their Precursors NO x emissions SO 2 emissions VOC emissions NH 3 emissions Primary Organic emissions Primary Inorganic PM emissions Crustal Ammonium EC Nitrate Sulfate Organics PM 2.5 Composition during the Winter (Adapted from Pandis, 2003)

The Sulfuric Acid/Ammonia System (Pandis, CMU) Total Available Ammonia (  g m -3 ) Concentration (  g m -3 ) 2 Ammonia:1 Sulfate (Adapted from Pandis, 2003)

Ammonium Nitrate Formation The formation of ammonium nitrate requires –Nitric acid (major sources of NOx in the US are transportation and power plants) –Free ammonia (ammonia not taken up by sulfate) The formation reaction is favored at: –Low temperatures (night, winter, fall, spring) –High relative humidity Hypothesis: A significant fraction of the sulfate reduced will be replaced by nitrate when SO 2 emissions are reduced. (Adapted from Pandis, 2003)

Fine PM Composition PM 2.5 (  g/m 3 ) Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun PM 2.5 mass (Adapted from Pandis, 2003)

Which is the Limiting Reactant? NH 4 NO 3 (  g m -3 ) Total Nitric Acid (  g m -3 ) Total Ammonia (  g m -3 ) A B A:Ammonia limited B: Nitric acid limited (Adapted from Pandis, 2003)

Reductions in Ammonia (July 2001) Inorganic PM 2.5 Reduction (%) Ammonia Reduction (%) 20% Sulfate Reduction (Adapted from Pandis, 2003)

Reducing Inorganic PM 2.5 Controls of SO 2 will reduce sulfate and PM 2.5 in all seasons. A fraction of the now existing sulfate will be replaced by nitrate. For Pittsburgh, ammonia controls in all seasons can minimize the replacement of sulfate by nitrate. For Pittsburgh, NO x controls will help reduce the nitrate during the winter but they will have a small effect during the summer. (Adapted from Pandis, 2003)

Nucleation Model Evaluation (July 27, 2001) Measured Predicted (Adapted from Pandis, 2003)

Nucleation and Ultrafine Particles The model was successful in reproducing the observed behavior (nucleation or lack of) in all simulated dates in July (10) and January (10) Strong evidence that the nuclei are sulfuric acid/ammonium/water clusters –Growth with the help of organics Discrepancies in the nucleation rates –the model tends to predict higher rates Ammonia appears to be the controlling reactant ! –Small to modest reductions of ammonia can turn off the nucleation in the area especially during the summer (Adapted from Pandis, 2003)

CMAQ Ammonia Sensitivity Runs- 50% NH 3 Reduction- January Basecase NitrateNitrate with 50% Ammonia Reduction

50% NO x Reduction- January Effect on Sulfate and Nitrate

50% NOx Reduction- Reduced NH3 base (50% NH3 reduction)- January effect on Sulfate and Nitrate

50% SO2 Reduction- July Effect on Sulfate and Nitrate

50% SO 2 Reduction- January Effect on Sulfate and Nitrate