The Dynamic World of Ammonia 1 NH 3 in the Environment HNO 3(g) - PowerPoint PPT Presentation

The Dynamic World of Ammonia 1

NH 3 in the Environment HNO 3(g) Deposition… Eutrophication? NH 3(g) Acidification? H 2 SO 4 Emissions ≈ 65 Tg N yr -1 ~5 ~6 ~37 ~2 ~4 ~9 2 Sutton et al. (2013) Phil. Trans. R. Soc. B.

Changes in precipitation N Li et al., PNAS , 2016 - wet deposition fluxes decreased (average 29%) o In all but one state, NO 3 + wet deposition fluxes increased (average 22%) o In 37 of 45 states, NH 4

Li et al., PNAS , 2016 NH x also comprises majority of total inorganic nitrogen deposition Biggest uncertainty lies with bidirectional NH 3 deposition Pleim et al., JGR , 2013

Spring overview • Strong concentration gradient • Low concentrations west of RMNP • High concentrations east of RMNP • Ammonia peaks in NE Colorado

A closer look… • Ammonium nitrate episodes associated with upslope flow from east of RMNP 140 360 120 precip 270 100 WD (Degree) 80 neq/m3 180 60 40 90 20 0 0 4/20 4/21 4/22 4/23 4/24 4/25 4/26 4/27 Date SO4= NO3- NH4+ WD 30 per. Mov. Avg. (WD)

NH 3 in Rocky Mountain National Park Denver RMNP RMNP morning NH 3 often increases prior to upslope flow from eastern Colorado NH 3 emissions Adapted from Benedict et al. (2013a) 6 NH 3 (ppb) 4 2 0 12:00 AM 6:00 AM 12:00 PM 6:00 PM 12:00 AM 6:00 AM 12:00 PM 6:00 PM 12:00 AM 6:00 AM 12:00 PM 6:00 PM 12:00 AM 2015-06-25 2015-06-26 2015-06-27 2015-06-28 7 Time (local)

What is dew? Ersa, Greek goddess of dew https://www.flickr.com/photos/steve wall/4680114666/in/photostream/ Radiative cooling of surfaces at night can drop their temperature below the air dewpoint leading to condensed water (dew) formation 8

𝑂𝐼 3(𝑕) ↔ 𝑂𝐼 3 ∙ 𝐼 2 𝑃 ↔ 𝑂𝐼 4 + + OH - 9

Motivation and Goals No quantitative studies on NH 3 emission from dew 1. Is dew a significant NH 3 reservoir? + 2. What happens to NH 4 (dew) upon evaporation? 3. Can dew evaporation explain the NH 3 morning spike? + ∗ 𝑊 𝐹𝑛𝑗𝑡𝑡𝑗𝑝𝑜 𝑂𝐼3 = 𝑂𝐼 4 𝑒𝑓𝑥 ∗ 𝐺𝑠𝑏𝑑 𝑂𝐼3 𝑢 𝑓𝑤𝑏𝑞𝑝𝑠𝑏𝑢𝑗𝑝𝑜 (in μ mol m -2 s -1 ) Verified in lab studies NH 3(g) 10

RMNP Dew Field Work • Dew collector w/ IC analysis • Dew meter to monitor dew formation and evaporation • Picarro Cavity Ringdown Analyzer to monitor gaseous NH 3 Dew meter based on Price and Clark (2014) • Meteorological Electronic balance with artificial turf surface measurements 11

Results – RMNP Dew Composition Average Frac NH3 = 0.94 Wentworth et al., 2016 12

Results – Dew and NH 3 Wentworth et al., 2016 13

Results – NH 3 in the Morning Dew No Dew Wentworth et al., 2016 14

Results – NH 3 Mass Closure Wentworth et al., 2016 Assuming a 150 m boundary layer… + gained  ~Mass closure for NH 3(g) lost to NH 4  NH 4 + (dew) :NH 3(BL) = 1.6 ± 0.7 at dawn 15

Conclusions 1. Ammonia is an abundant and dynamic beast Gas-particle-partitioning • Bidirectional atmosphere-surface exchange • 2. Dew is an important temporary reservoir for ammonia ~60% NH 3 in RMNP BL goes to dew overnight • + is re-released as NH 3 in RMNP ~94% of dew NH 4 • Dynamics are environment/dew composition dependent! • Implications for… Other gases (acetic acid, formic acid, HONO, …) • Reduction in overnight NH 3 dry deposition • + wet deposition…? Permanence of NH 4 • 16 Caters News Agency

http://www.fotocommunity.de/photo/the-light-pours-out-of-me- Acknowledgments jens-kolk/3960881 – Katie Benedict and Yi Li, CSU – Greg Wentworth and Jen Murphy, Univ. of Toronto – Bret Schichtel and Tony Prenni, NPS 17

+ loss from wet deposition? NH 4 Evidence of NH 3 volatilization during rain evaporation…  Is this significant? Only in dry regions?  Does fractional loss decrease with larger rain events? 18

+ % of wet NH 4 inorganic N dep - dominated • NO 3 U.S. wet N dep in 70s and 80s + now • NH 4 comprises > 50% of wet inorganic nitrogen deposition across most of the U.S. Li et al., PNAS , 2016

+ Annual Timelines NH 3 and NH 4 RMNP 1.0 Brush Loveland RMNP NH 3 0.8 Concentration (µmol/m 3 ) 0.6 0.4 0.2 0.0

NH 3 Morning Spike Dew Evaporation? Traffic Emissions? Wichink Kruit et al. (2007) Löflund et al. (2002) Gong et al. (2011) Nowak et al. (2006) Wentworth et al. (2014) Whitehead et al. (2007) Gong et al. (2011) Plant/Soil Emissions? Bash et al. (2010) Mixing Down? Ellis et al. (2011) Walker et al. (2006) 6 NH 3 (ppb) 4 2 0 12:00 AM 6:00 AM 12:00 PM 6:00 PM 12:00 AM 6:00 AM 12:00 PM 6:00 PM 12:00 AM 6:00 AM 12:00 PM 6:00 PM 12:00 AM 2015-06-25 2015-06-26 2015-06-27 2015-06-28 21 Time (local)