Aerosol and trace gas processing by tropospheric … · Aerosol and trace gas processing by CRPAQS...
Transcript of Aerosol and trace gas processing by tropospheric … · Aerosol and trace gas processing by CRPAQS...
Aerosol and trace gas processingby CRPAQS fogs
J. Collett, P. Herckes, H. Chang and T. LeeAtmospheric Science Department
Colorado State UniversityFort Collins, Colorado USA
Outline• Particle and gas scavenging by fogs• SJV fogs
– Past lessons– CRPAQS observations
• Aerosol and gas processing by CRPAQS fogs– Importance of organics– Deposition– New particle production - HMS
• Summary concepts and future research needs
Particle and gas scavenging
• Particlesscavenged bynucleation,diffusion,impaction,interception
• Soluble gasespartition todrop
Gas-liquid equilibrium• Models and field
observationssuggest commonlack of gas-liquidequilibrium– Highly soluble
gases haveinsufficient time toequilibrate withlarge drops
– Species derivedfrom aerosolparticles may besupersaturated indrops (e.g., Ricciet al., 1998)
Equilibrium time for pH 7 drops with r = 10 µmCourtesy of B. Ervens, NOAA
SJV fogs • Dense, widespread radiationfogs occur during winter– Moist air trapped in valley by
thermal inversion– Radiative cooling produces
fogs• Fogs affect particles by
– Production of non-volatilesolute mass
– scavenging and deposition
Particles
Fog Dropsreactions
Fog Drops
Deposition
Evaporation Gases
Past Studies of SJV fogs - I
• Nitrate andammonium typicallymajor species– pH high– Important organic
carbon contributions– Nitrite and sulfate
also present– Composition variable
in time and space
Ammonium1087
Nitrate567
Acetate151
Sulfate100
Formate83
Other Anions44
Other Cations31
Major Ion Concentrations (µN)Fresno Fog (December 10, 1995, 03:00-04:00)
2.0
3.0
4.0
5.0
6.0
7.0
8.0
SJV
Cal
.
Sac
Val
Cal
.
So.
Cal
.
Ore
gon
Coa
st
Col
orad
oR
ocki
es
Mt.
Mitc
hell
Whi
tefa
ceM
t.
pH
Past Studies of SJV fogs - II
• Deposition ofinorganic ionsimportant– What about OC?
• Sulfate production ~balances sulfatedeposition– Secondary organic
aerosol production? Pre-fog
After Fog
Gas Prod.
Aq. Prod.
Wet D
ep.
Dry D
ep.
Emissions
Net C
hange
-10
0
10
20
30
Thou
sand
sSp
ecie
s 1
km C
olum
n Bu
rden
(µg/
m2) Total Sulfate
Total NitrateTotal Ammonia
CRPAQS Fog Measurements
• Angiola– Bulk and
size-resolved fogcomposition
– Vertical fogprofilesfrom tower
– Fogdepositionfluxes
• Other sites– Helm– McKittrick– Bakersfield
CRPAQS Fog Measurements - II
• Fog deposition
Vd = Flux/C
• Lab Analyses– Major ions and metals– Total/Dissolved Organic
Carbon (TOC/DOC)– Organic composition
• Organic acids• Carbonyls• Other trace species by
GC/MSFlux
C
Vd
CRPAQS FogFindings
• Several fog episodes atAngiola and Helm– No fog at McKittrick– 1 event at Bakersfield
• Composition similar to pastSJV fog studies
Angiola
[H+][Na+][NH4+] [K+][Mg++][Ca++][Cl-][NO2-][NO3-][SO4=]
Bakersfield (1 sample) Helm
0
200
400
600
800
1000
12/13 12/23 1/2 1/12 1/22 2/1
Liqu
id w
ater
con
tent
(mg/
m3)
Angiola fogcharacteristics
• Fog layer veryshallow– Rarely reached top
level of tower
• Fog drops very large– Drizzle formation
from shallow fog• Strong radiative
cooling of largedrops
– Fast deposition
0:00-1:00
010203040506070
5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 38 41 43 47Diameter (um)
num
ber c
once
ntra
tion
(cm
-3)
Effective diameters during 12/18/00 event
24.0
26.0
28.0
30.0
32.0
34.0
36.0
38.0
40.0
0:00
1:00
2:00
3:00
4:00
5:00
effe
ctiv
e di
amet
er (u
m)
CRPAQS FogOrganics
• Organic carbon iskey component ofCRPAQS fogs
• ~75% of OC isdissolved
• Fogs process solubleand insoluble OC
0
5
10
15
20
0 5 10 15 20
TOC (ppmC)
Dis
solv
ed O
C (p
pmC
)
n-alkanoic acids - Angiola, 12/17/00
0
5
10
15
20
25
C9 C10 C11 C12 C13 C14 C15 C16 C17 C18 C19 C20 C21 C22 C23 C24 C25 C26
ng/m
L
insolublessolubles
CRPAQS typical fog mass composition
NO3-39%
NO2-3%SO42-
6%
NH4+23%
Organic matter29%
CRPAQS FogOrganics - II
• Many organiccompoundspresent– PM source
tracers• Lots of high
molecularweightmaterial
Organic Carbon Molecular Weight Distribution
0%
20%
40%
60%
80%
100%
12/17 1/10 1/15 1/17 1/21 1/31
MW < 500
500 < MW < 1000
MW > 1000
OOH
benzoic acidCO2Hpimaric acid
vanillin
OOOH
syringol OOH
Opyrene
21.0%
22 .2%4 .8%
8 .3%
21.7%
2 .2%
0 .1%
1.9%
0 .2%
17.6%
56 .8%
MW > 1000
1000> MW >500
Fo rmaldehyde
Fo rmate
Aceta te
diac ids (C2-C5)
n-a lkanes (C11-C40)
n-a lkano ic ac ids (C9-C33)
P AH + o xy-P AH
o ther MW < 500
Fog Dissolved Organic Carbon Composition
Importance ofhigher MWcarbonyls
• HPLC analysis ofCRPAQS samplesshowed fewcarbonyls– Tests show rapid
loss in fog• Not in H2O
• Preserved Fresno1/04 fog samplesreveal largecontributions fromseveral carbonylsand dicarbonyls
Carbonyl stability test
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
9/15
9/18
9/22
9/29
10/7
10/1
5
Date
Con
cent
ratio
n (u
g/m
l)
Acetone
Benzaldehyde
Glyoxal
Methyl Glyoxal
Figure 5.x Typical composition of carbonaceous material comprising the total dissolved organic carbon (DOC) content observed for several California Fresno
radiation fog samples.
Carbonyls9%
o-Tolualdehyde0.01%
Isovaleraldehyde1%
Butyraldehyde0.03%
Acetone&Acrolein0.4%
HCHO3%
Organic Acid29%
m-Tolualdehyde0.06%
Acetaldehyde1%
p-Tolualdehyde0.1%
Hexaldehyde0.2%
Glyoxal2%
Methyl Glyoxal 2%
Unknown
Organic Acid
HCHO
Acetaldehyde
Acetone&Acrolein
Butyraldehyde
Isovaleraldehyde
o-Tolualdehyde
m-Tolualdehyde
p-Tolualdehyde
Hexaldehyde
Methyl Glyoxal
Jan. 2004 Fresno Fog DOC
Composition size-dependence
• Drop composition varieswith size– Pattern varies between
species– Most enriched in small drops
5-stage collector - Jan 17
0
500
1000
1500
2000
2500
NO3- SO42- NH4+
Con
cent
ratio
n (u
N)
V1V2V3V4V5
0
20
40
60
80
100
120
0 20 40 60 80 100 120
small drop nitrite (µN)
larg
e dr
op n
itrite
(µN
)
05
10152025303540
0 5 10 15 20 25 30 35 40
small drop TOC (ppmC)
larg
e dr
op T
OC
(ppm
C)
CRPAQS FogDeposition
• Depositionvelocities inCRPAQS fogshigh– ~ 1-2 cm/s– >> PM2.5
• Depositionvelocity dependson solutedistribution withdrop size
0
1
2
3
4
5
6
7
NO3- SO42- TOC NH4+ Water NO2-
Dep
ositi
on v
eloc
ity (c
m/s
)
0
1
2
3
4
5
6
0 1 2 3 4 5 6
small/large drop concentration ratio
Dep
ositi
on v
eloc
ity (c
m/s
)
CRPAQS FogDeposition
• Fog event fluxes rangefrom 10s to 1000s ofµg/m2
• Assuming a 100 m deepfog, concentrations woulddecrease typically~ 0.5 µg/m3/hr sulfate~ 1 µg/m3/hr nitrate~ 1 µg/m3/hr ammonium~ 0.7 µgC/m3/hr TOC
• Remember, fog solutescan be volatile or non-volatile
Fog deposition
Aqueous reactions andnew particle production
• S(IV) reactions– Oxidation
• by H2O2, O3 andO2/Fe(III)+Mn(II)
• S(IV)-aldehydecomplex formation
• e.g., HCHO + HSO3-
CH2(OH)SO3-
0 2 4 6 8pH
1E-15
1E-13
1E-11
1E-9
1E-7
1E-5
1E-3
1E-2
-d [S
(IV)]
/ dt
(M/s
)
H2O2O3O2/Fe(III) +Mn(II)
Typical Fog Conditions
S(IV)simulations
• Fate of dissolvedSO2 simulated forall sample periodswith single dropmodel– Oxidation by O3
and H2O2
– Rxn with HCHO• Most SO2
expected to formHMS at high fogpH
Large Drops
O3
80%
H2O2
20%HMS97%
S(VI)3%
S(IV) Sinks S(IV) Oxidation
CMUModeling
(Fahey and Pandis)
• Fog modelreasonablypredicts– Bulk fog
composition
– Size-dependence
– Deposition fluxes
00.20.40.60.8
11.21.41.6
0 5 10 15 20
time (hr)
Sulfa
te ( µ
g/m
3 )
Predicted
Observed
01234567
0 5 10 15 20
time (hr)
Nitr
ate
( µg/
m3 )
PredictedObserved
(a) (b)
0
10
20
30
40
50
60
0 20 40 60
Diameter (mm)
Sulfa
te ( µ
M)
0100200300400500600700800900
0 20 40 60
Diameter (mm)
Am
mon
ium
( µM
)
PredictedPredicted
(a) (b)
0
50
100
150
200
250
0 5 10 15 20
time (hr)
Am
mon
ium
Dep
ositi
onal
Flu
x (n
eq/m
2 /min
)
02468
101214161820
0 5 10 15 20
time (hr)C
hlor
ide D
epos
ition
al F
lux
(neq
/m2 /m
in)
Predicted
Observed
(a)
Predicted
Observed
(b)
Acknowledgements
• CSU– S. Kreidenweis, G. Kang. J. Reilly, E. Sherman
• Carnegie Mellon– S. Pandis and K. Fahey
• National Science Foundation
Summary concepts and future needs
• Nitrogen species dominate fogcomposition
• Fogs are effective cleansers of theSJV atmosphere
– Removal rates depend on speciesdistributions across fog drop sizespectrum
– Sulfate removal balanced byproduction
• Organic matter comprises a largeportion of fog solutes
– Combination of volatiles and non-volatiles
– Large amount of high MWmaterial
– Large OC deposition fluxes
• High time resolution aerosol andfog measurements
– PILS + OC/EC in Fresno• Better characterization of organic
matter scavenged by fogs– Improved speciation– Source marker tracking
• Role of fogs in secondary organicaerosol formation
CRPAQS fog papers• Herckes et al. (2002) Organic
Matter in central Californiaradiation fogs, ES&T 36, 4777-4782.
• Ervens et al. (2003) On thedrop-size dependence oforganic acid and formaldehydeconcentrations in fog, J. Atmos.Chem. 46, 239-269.
• Fahey et al. (2004) Theinfluence of size-dependentdroplet composition onpollutant processing by SanJoaquin Valley fogs, submitted.
• Overview paper for specialissue (tbd)