From Ammonia to PM2.5

Brent AuvermannTexas Cooperative ExtensionTexas Agricultural Experiment

StationAmarillo, 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

N2

NH3

N2O NO

NOx

NH3 – What’s the Big Deal?

• Superfund/EPCRA – Federal litigation on broad CAFO front– Multiple species– Multiple states– Do the math

• NH3 + (SO4, NO3 or Cl) >> PM2.5

• NH3 + PM >> synergistic effect on animal pulmonary health >> effect on human health?

0

200

400

600

800

1,000

0 20 40 60 80 100

N Use Efficiency

CE

RC

LA

Th

resh

old

Cap

acit

y

Y

0

200

400

600

800

1,000

0 20 40 60 80 100

Aggregate N Efficiency (%)

CE

RCL

A T

hre

shold

Cap

aci

ty

Y

Open-Lot Systems

• Beef feedyards– Animal spacing 75-250

ft2/hd– Excreted N 90% of N

consumed in feed (Bierman et al., 1996)

• Open-lot dairies– Animal spacing 200-

400+ ft2/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 NH3(g) directly– Increases with wet/dry cycling

Extinction efficiencies for ubiquitous particle types (Malm, 1999)

Particle TypeDry Extinction

Efficiency (m2/g)Sulfates 3.0

Organics 3.0

Elemental Carbon 10.0

Nitrates 3.0

Soil Dust 1.25

Coarse Particles 0.6

Feedyard PM10/TSP 0.5-0.6/0.3-0.4

Air Pollution in Pittsburgh

July 2, 2001

PM2.5=4 g m-3

July 18, 2001

PM2.5=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

NOx emissions

SO2 emissions

VOC emissions

NH3 emissions

Primary Organic emissions

Primary Inorganic PM emissions

0

5

10

15

20

25

30

35

40

Co

nce

ntr

atio

n

CrustalAmmonium

EC

Nitrate

Sulfate

Organics

PM2.5 Composition during the Winter

(Adapted from Pandis, 2003)

The Sulfuric Acid/Ammonia System (Pandis, CMU)

02468

101214161820

0 1 2 3 3.6 5 10

Ammonia

Ammonium

Sulfate

Bisulfate

Sulfuric acid

Total Available Ammonia (g m-3)

Co

nc

entr

ati

on

(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 SO2 emissions are reduced.

(Adapted from Pandis, 2003)

Fine PM CompositionP

M2

.5 (

g/m

3)

0

5

10

15

20

25

30

35

Organic matter Elemental carbon Sulfate Nitrate Ammonium Crustal components

Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun

2001 2002

PM2.5 mass

(Adapted from Pandis, 2003)

Which is the Limiting Reactant?

0 10 20 30 40

0

20

40

60

80

10

30

50

NH4NO3 (g m-3)

To

tal N

itri

c A

cid

(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)

0 10 20 30 40 50

0

10

20

30

40

Inorg

an

ic P

M2

.5 R

ed

uct

ion

(%

)

Ammonia Reduction (%)

20% Sulfate Reduction

(Adapted from Pandis, 2003)

Reducing Inorganic PM2.5

• Controls of SO2 will reduce sulfate and PM2.5 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, NOx 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% NH3 Reduction- January

Basecase Nitrate Nitrate with 50% Ammonia Reduction

50% NOx Reduction- JanuaryEffect on Sulfate and Nitrate

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

50% SO2 Reduction- JulyEffect on Sulfate and Nitrate

50% SO2 Reduction- JanuaryEffect on Sulfate and Nitrate