case studies of oh and gaseous sulfur compounds in relation to aerosol particles in the marine...

Case Studies of OH and Gaseous Sulfur Compounds in Relation to Aerosol Particles in the Marine Atmosphere

Max Adam

Centre for Climate and Air Pollution Studies, School of Physics National University of Ireland Galway, Ireland

19/09/2013ACCENT-Plus Symposium

http://www.ncar.ucar.edu/

ACCENT-Plus Symposium 2

Mace Head Research Station

Mace Head

19/09/2013

• Global Atmosphere Watch (GAW) and EMEP Station

• Extensive Aerosol and GHG measurements

• Marine air sector from 190° - 300°

• Since 2010: OH, H2SO4, MSA(g), NO, NO2, J(O1D), J(NO2)

MSA(g) methane sulfonic acid, CH3SO3HJ(O1D) photolysis frequency of ozoneJ(NO2) photolysis frequency of nitrogen dioxide


O(1D)

H

HCHO

CO

O(3P)

O3

H2O2

RO2

H2O

OH

X

SO2

CH2-CCl3

NH2

XO NO

HSO3 HS

H2SO4HNO3

HCl

HO2

NO

O3

multiplesteps multiple

steps

multiplesteps

multiplesteps

multiplesteps

other S-products

multiplesteps

HO2

Rain

M

O2,M

HXNO2

CH3CCl3

CH3SCH3

NH3

H2

CxHy

hh

h

H2O

O2,M

Aerosol

AerosolRain

AerosolRain

H2SSO2

HCFC

CO,CH4

HX = HCl, HF, HBr, HICxHy = Hydrocarbons

Atmospheric Oxidation Efficiency

OH Primary Production

Ozone Photolysis 340 nm

J(O1D) = Photolysis Frequency, s-1 Formation of O(1D) by UV-B Proxy for UV-B

O3 + h O(1D) + O2

O(1D) + H2O 2 OH

J(O1D)

OH :

Most important oxidant (chemical detergent) of the atmosphere !

Main Consumption:

Reactions with Methane (CH4), Carbon Monoxide (CO)

(OH) 1 sec

19/09/2013

ACCENT-Plus Symposium 4 19/09/2013

Chemical Ionisation Mass Spectrometer (CIMS)

OH H2SO4

MSA(g)


[OH] = m/z 99, Signal– Background

Signal (Mass 99) = Ambient OH + 34SO2 H34SO4-

Background (Mass 99) = Ambient OH + 34SO2 + OH Scavenger (Propane)

Chemical Ionisation Mass Spectrometer (CIMS)

[MSA] = m/z 95

Reagent Ion = NO3- (Mass 62)

[H2SO4] = m/z 97 30 sec measurements

19/09/2013

Measurement Principle for OH, H2SO4 and MSA (g)

Det. Limits (2σ, 5min): OH = 1.3 x 105 molec cm-3

H2SO4, MSA = 4.3 x 104 molec cm-3


Location of CIMS and Radiometers

19/09/2013


1. J(O1D): A Proxy for OH

Berresheim, H., et al. (2013), Geophys. Res. Lett., 40, 1659–1663 Rohrer, F. and Berresheim, H. (2006), Nature, 442, 184-187

• No tidal cycle relation.

Results

Marine Air (NO<50 pptv)

• Strong OH - J(O1D) correlation (R = 0.75)


Mid-day Maxima of H2SO4 and MSA(g) in Marine Air Mace Head, Ireland (10-14 UTC; 05/2010 - 08/2012)

2a. H2SO4 and MSA (g) - Time Series


Monthly Mean Aerosol MSA(a) and Non-Sea Salt Sulfate Concentrations in Marine Air Mace Head, Ireland

2a. MSA(a) and nss-SO4 - Time Series

Ovadnevaite, J. et al., manuscript in prep., 2013


• Total SO2 Measurement Period: 02 May 2011 – 12 August 2011

• Marine SO2 Average Mixing Ratio = 163 (± 58) pptv

SO2 Measurements (Thermo 43i)

2b. H2SO4 - Mass Balance


2b. Mass Balance

[H2SO4]calc=

• Case study of measured vs. calculated H2SO4 on 05 June 2011.

CS = Aerosol Condensational Sink for H2SO4

k OH [ SO 2 ] [OH ]CS

• Discrepancy by a factor of 3.5 is observed.

3.5


k OH [ SO 2 ] [OH ]+k X [SO 2 ] [X ]CS

2c. Mass Balance with X-Compound

[H2SO4]calc=

1Mauldin, R.L., et al. (2012), Nature, 488, 193-196.

• Case study of measured vs. calculated H2SO4 on 05 June 2011.

CS = Aerosol Condensational Sink for H2SO4

• Discrepancy by a factor of 3.5 is observed.

• Presence of another oxidant ‘X’ that oxidises SO2 to H2SO4.

• sCI (from α-pinene, limonene + O3)1, halogen (BrO, ClO, IO, OIO), or NO3 radicals found to be unlikely candidates for ‘X’ .

A major missing oxidant for SO2 !


Schematic of front inlet

Amplification factor = for Criegees in CIMS

[ ] [ ]

[ ]amb cims

amb

sCI sCIAF

sCI

= 3.25


3. MSA – Gas Particle Partitioning

• Nighttime peak MSA(g) mixing ratios – support general anti-correlation of MSA(g) with relative humidity.

1De Bruyn, W.J., et al. (1994), J. Geophys. Res., 99, 16927-16932.

• MSA(g) - low lifetime with respect to aerosol uptake (1/CS) of 31.7 min assuming a sticking coefficient alpha (α) = 0.121


Conclusions

19/09/2013

• OH shows a robust relationship with J(O1D) but has no relation to tide.

• H2SO4 balance: Calculation based only on SO2+OH source underestimates observed H2SO4 by factor 4.2 (on average).

• Evidence for presence of an unknown oxidant X from OH background measurements. Criegees (α-pinene, limonene + O3) are unlikely candidates.

• MSA partitions back to gas phase with rH decreasing. Caution with respect to using average aerosol MSA/nss-SO4 ratio for calculating biogenic nss-SO4 fraction.

16

Elevated Background, Case 2: 9th June 2011

Thank You!

Acknowledgements

H. Berresheim (NUI, Galway)

F. Rohrer (Research Center Jülich, Germany)B. Bohn (Research Center Jülich, Germany)

C. Monahan (NUI, Galway)C. O‘Dowd (NUI, Galway)

J. Ovadnevaite (NUI, Galway)J. M. C. Plane (Univ. of Leeds, UK)

Sponsors: SFI, EPA – Ireland

19/09/2013ACCENT-Plus Symposium

http://www.ncar.ucar.edu/

case studies of oh and gaseous sulfur compounds in relation to aerosol particles in the marine...

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