fog processing of atmospheric organic compounds during the ... · san joaquin valleywide air...

Funding fromSan Joaquin Valleywide Air Pollution Study Agency

National Science Foundation (NSF)

Funding fromSan Joaquin Valleywide Air Pollution Study Agency

National Science Foundation (NSF)

Fog Processing of atmospheric organic compounds duringthe California Regional PM10/PM2.5 Air Quality Study

(CRPAQS)

P. Herckes, T. Lee, L. Trenary, G. Kang, and J.L. Collett, Jr.Colorado State University

Main site: Angiola

Satellite sites:Helm

Bakersfield

McKittrick

Fog study sites

Instrumentation

CASCC, sf-CASCC, ss-CASCC, ss-sf-CASCC, 5-stage fog collector,CHRCC, Tower (4 levels of Al-CASCC2), Deposition PlatesPVM, CSASP, CSU-OFDMOUDI, organic Aerosol, Continuous Peroxide Analyzer

December 10th 2000 - February 2nd 2001December 10th 2000 - February 2nd 2001

ss-CASCC: Bulk fogwaterPM 2.5 + interstitial aerosol

ss-sf-CASCC: size fractionated fogSize-cut: approx 17 µm

fog/ground based cloud sampling

Investigation of bulk properties of OMIndividual compound speciation

Variation with drop-sizeProcessing of carbonaceous particles



Total and Dissolved Organic Matter Characterization

sample TOC

DOC 1

DOC 2

DOC 3

DOC aliquot

MW < 1000, DOC aliquot


Filtration 1

Ultrafiltration 1, YM1


Total Organic Carbon concentrations

TOC mgC/L

avg (min-max)

CRPAQS

Angiola 10 (2-41) Herckes et al., 2002 Helm 6-16 Herckes et al., 2002 Bakersfield 27 Herckes et al., 2002 IMS 95 5-41 Collett et al., 1999 Bakersfield 9-276 Jacob et al., 1984 Davis 32.5 (5-111) Zhang et al, 2001 Po Valley fogs (Italy) 15-108 Gelencser et al., 2000


sample TOC

DOC 1

DOC 2

DOC 3

DOC aliquot



Filtration 1



0

2

4

6

8

10

12

14

16

18

20

0 2 4 6 8 10 12 14 16 18 20TOC (ppmC)

DO

C (p

pmC

)

ss-CASCCss-sf-CASCC Largess-sf-CASCC Small1:1 line

Total vs Dissolved Organic Carbonfog-Angiola (SJV, Ca)

Total vs Dissolved Organic Carbonfog-Angiola (SJV, Ca)

25% insoluble (0-64%)25% insoluble (0-64%)


sample TOC

DOC 1

DOC 2

DOC 3

DOC aliquot



Filtration 1



0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

12/17 1/10 1/15 1/17 1/21 1/31

MW < 500

500 < MW < 1000

MW > 1000

Dissolved Organic Matter

significant fraction of DOC has high Molecular Weight (MW)significant fraction of DOC has high Molecular Weight (MW)

samplefiltration

Soluble: liquid sample Insoluble: filter

3 x 25 ml DCMUltrasonic bath

extractSPME

LLE: 3 x 25ml DCM

(SPE) extraction

GC-MS analysis

neutralmethylated

silylated derivatization+ analysis

pH, formaldehyde, TOC/DOC,….

Molecular composition of organic matter in California fog

A large number of different compounds has been identified in the fogwater

Polar compounds:

carboxylic acids (C1-C36)di-carboxylic acids (C2-C9)aromatic acids (benzoic acid…)resin acids (pimaric acid,…)aldehydes (formaldehyde,..)phenols (phenol, nitro-phenol….)methoxyphenols (vanillin, ethyl-guaiacol,…)oxygenated PAH (9, 10 Anthracenedione,..)pesticides (Diazinon, Penoxaline,..)

Nonpolar compounds:

n-alkanes (C20* – C39)Polyaromatic Hydrocarbons (PAH) (pyrene,…)…

Polar compounds:

carboxylic acids (C1-C36)di-carboxylic acids (C2-C9)aromatic acids (benzoic acid…)resin acids (pimaric acid,…)aldehydes (formaldehyde,..)phenols (phenol, nitro-phenol….)methoxyphenols (vanillin, ethyl-guaiacol,…)oxygenated PAH (9, 10 Anthracenedione,..)pesticides (Diazinon, Penoxaline,..)

Nonpolar compounds:

n-alkanes (C20* – C39)Polyaromatic Hydrocarbons (PAH) (pyrene,…)…

OOH

benzoic acidCO2H

pimaric acid

vanillin

OOOH

syringol OOH

O

pyrene

O

O

9,10 anthracenedione

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

n-alkanoic acids (Angiola (CA), December 17, 2000)

Smaller MW compounds predominantly solubleLarger MW compounds predominantly insolubleSmaller MW compounds predominantly solubleLarger MW compounds predominantly insoluble

TOC variation with droplet size

0

5

10

15

20

25

30

35

0 5 10 15 20 25 30 35

TOC of large droplets (ppmC)

TOC

of s

mal

l dro

plet

s (p

pmC

Higher concentrations in smaller dropletsRatio 2.8 on average (0.8-6.3)Higher concentrations in smaller dropletsRatio 2.8 on average (0.8-6.3)

Individual organic compounds

0

5

10

15

20

25

30

0 5 10 15 20 25 30large droplet concentration (d>17µm) in µeq/L

smal

l dro

plet

con

cent

ratio

n (d

<17µ

m) i

n µe

q/L

1:1 lineoxalic acid

Consistent with inorganic compounds

Dissolved Organic Carbon75%

insoluble organic material

25%MW >1000 Da

20%

500 Da < MW <1000 Da19%

MW < 500 Da61%

0.75% (0.55-0.95%)n-alkanoic acids

(C9-C28)

<0.1% (0.05-0.1%)n-alkanes (C10-C40)

0.1% (0.02-0.25%)30 PAH and oxy-PAH

8%(2-24%) formaldehyde

59% unknow ns

30% (1-64%)mono acids C1-C3

2% (0-4%)di-acids (C2-C6)

What we learned about the organic matter

1.6% (<0.1% - 2.6%)

5.1 %(1.1-11%)6.6% (0.2-10%)

11.3% (0.3-27%)

0

2

4

6

8

10

12

acetic acid formic acid formaldehyde oxalic acid

% D

OC

Dominant individual organic species

Limited information due to low time resolutionLimited information due to low time resolution

Scavenging of organic carbon

0

2

4

6

8

10

12

1/14/2001 1/15/2001 1/16/2001 1/17/2001 1/18/2001 1/19/2001 1/20/2001

ratio

OC

/EC

and

TC

in u

g/m

3

0

100

200

300

400

500

600

700

800

LWC

in m

g/m

3

OC/ECTCLWC

13 hour fog event:294 g/m2 water (1 inch =25.4kg/m2)1.2 mg of C/m2

Considering a fog layer of 100m depthdecrease of 12 µgC/m3

significant removal of ambient OC (~10µgC/m3)

- some from volatile species!- entrainment from upper layers

Fog deposition flux: case example December 17/18th, 2000

Conclusions

- organic matter (OM) is an important component of SJV fogs

- 25% of OM is associated with insoluble material

- large fraction of OM has high molecular weight

- only a small fraction is identified at molecular level

- monocarboxylic acids are the dominant species

- small droplets are enriched in OM

- deposition fluxes suggest a significant removal of OM by fogs

Related posters

“Overview of fog studies during the California RegionalPM10/PM2.5 Air Quality Study (CRPAQS)”

7PB10“Aerosol Processing and removal by fogs: Observations in radiation fogs during the CRPAQS study “

7PB11

Acknowledgements

E. Sherman, S. Emert, J. Reilly for assistance during theplanning and execution of the field study

fog processing of atmospheric organic compounds during the ... · san joaquin valleywide air...

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