SLIDE 1
The Dynamic World of Ammonia
1
NH3 in the Environment
NH3(g)
H2SO4 HNO3(g) ~9 ~5 ~37 ~2 ~4 ~6 Emissions ≈ 65 Tg N yr-1 Sutton et al. (2013) Phil. Trans. R. Soc. B. Deposition… Eutrophication? Acidification?
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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) - - 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
SLIDE 2
SLIDE 3
Changes in precipitation N
- In all but one state, NO3
- wet deposition fluxes decreased (average 29%)
- In 37 of 45 states, NH4
+ wet deposition fluxes increased (average 22%)
Li et al., PNAS, 2016
SLIDE 4
NHx also comprises majority of total inorganic nitrogen deposition
Li et al., PNAS, 2016
Biggest uncertainty lies with bidirectional NH3 deposition
Pleim et al., JGR, 2013
SLIDE 5
Spring overview
- Strong
concentration gradient
- Low
concentrations west of RMNP
- High
concentrations east of RMNP
- Ammonia peaks
in NE Colorado
SLIDE 6
A closer look…
- Ammonium nitrate episodes
associated with upslope flow from east of RMNP
20 40 60 80 100 120 140 4/20 4/21 4/22 4/23 4/24 4/25 4/26 4/27 Date neq/m3 90 180 270 360 WD (Degree) SO4= NO3- NH4+ WD 30 per. Mov. Avg. (WD)
precip
SLIDE 7
6 4 2 NH3 (ppb) 12:00 AM 2015-06-25 6:00 AM 12:00 PM 6:00 PM 12:00 AM 2015-06-26 6:00 AM 12:00 PM 6:00 PM 12:00 AM 2015-06-27 6:00 AM 12:00 PM 6:00 PM 12:00 AM 2015-06-28 Time (local)
NH3 emissions
Adapted from Benedict et al. (2013a)
RMNP Denver
NH3 in Rocky Mountain National Park
RMNP morning NH3 often increases prior to upslope flow from eastern Colorado
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SLIDE 8
What is dew?
Radiative cooling of surfaces at night can drop their temperature below the air dewpoint leading to condensed water (dew) formation
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https://www.flickr.com/photos/steve wall/4680114666/in/photostream/
Ersa, Greek goddess of dew
SLIDE 9
9
𝑂𝐼3() ↔ 𝑂𝐼3 ∙ 𝐼2𝑃 ↔ 𝑂𝐼4 + + OH-
SLIDE 10
Motivation and Goals
No quantitative studies on NH3 emission from dew
- 1. Is dew a significant NH3 reservoir?
- 2. What happens to NH4
+ (dew) upon evaporation?
- 3. Can dew evaporation explain the NH3 morning spike?
NH3(g)
𝐹𝑛𝑗𝑡𝑡𝑗𝑝𝑜𝑂𝐼3 = 𝑂𝐼4
+ ∗ 𝑊 𝑒𝑓𝑥
𝑢𝑓𝑤𝑏𝑞𝑝𝑠𝑏𝑢𝑗𝑝𝑜 ∗ 𝐺𝑠𝑏𝑑𝑂𝐼3
(in μmol m-2 s-1)
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Verified in lab studies
SLIDE 11
RMNP Dew Field Work
- Dew collector w/
IC analysis
- Dew meter to
monitor dew formation and evaporation
- Picarro Cavity
Ringdown Analyzer to monitor gaseous NH3
- Meteorological
measurements
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Dew meter based on Price and Clark (2014) Electronic balance with artificial turf surface
SLIDE 12
Results – RMNP Dew Composition
Average FracNH3 = 0.94
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Wentworth et al., 2016
SLIDE 13
Results – Dew and NH3
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Wentworth et al., 2016
SLIDE 14
Results – NH3 in the Morning
Dew No Dew
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Wentworth et al., 2016
SLIDE 15
Assuming a 150 m boundary layer…
- ~Mass closure for NH3(g) lost to NH4
+ gained
- NH4
+ (dew):NH3(BL) = 1.6 ± 0.7 at dawn
Results – NH3 Mass Closure
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Wentworth et al., 2016
SLIDE 16
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% NH3 in RMNP BL goes to dew overnight
- ~94% of dew NH4
+ is re-released as NH3 in RMNP
- Dynamics are environment/dew composition dependent!
Implications for…
- Other gases (acetic acid, formic acid, HONO, …)
- Reduction in overnight NH3 dry deposition
- Permanence of NH4
+ wet deposition…?
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Caters News Agency
SLIDE 17
Acknowledgments
17 http://www.fotocommunity.de/photo/the-light-pours-out-of-me- jens-kolk/3960881
– Katie Benedict and Yi Li, CSU – Greg Wentworth and Jen Murphy, Univ. of Toronto – Bret Schichtel and Tony Prenni, NPS
SLIDE 18
Evidence of NH3 volatilization during rain evaporation…
- Is this significant? Only in dry regions?
- Does fractional loss decrease with larger rain events?
NH4
+ loss from wet deposition?
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SLIDE 19
NH4
+ % of wet
inorganic N dep
- NO3
- dominated
U.S. wet N dep in 70s and 80s
- NH4
+ now
comprises > 50%
- f wet inorganic
nitrogen deposition across most of the U.S.
Li et al., PNAS, 2016
SLIDE 20
NH3 and NH4
+ Annual Timelines
0.0 0.2 0.4 0.6 0.8 1.0
Concentration (µmol/m3) NH3
Brush Loveland RMNP
RMNP
SLIDE 21
6 4 2 NH3 (ppb) 12:00 AM 2015-06-25 6:00 AM 12:00 PM 6:00 PM 12:00 AM 2015-06-26 6:00 AM 12:00 PM 6:00 PM 12:00 AM 2015-06-27 6:00 AM 12:00 PM 6:00 PM 12:00 AM 2015-06-28 Time (local)
NH3 Morning Spike
Dew Evaporation? Wichink Kruit et al. (2007) Gong et al. (2011) Wentworth et al. (2014) Plant/Soil Emissions? Bash et al. (2010) Ellis et al. (2011) Traffic Emissions? Löflund et al. (2002) Nowak et al. (2006) Whitehead et al. (2007) Gong et al. (2011) Mixing Down? Walker et al. (2006)
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