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Oxygenated volatile organic compounds in the remote marine - - PowerPoint PPT Presentation

Apr 13, 2023 17 likes •218 views

Oxygenated volatile organic compounds in the remote marine troposphere: Results from the Cape Verde Atmospheric Observatory Cape Verde Atmospheric Observatory (CVAO) 16 52' N, 24 52' W Lucy J. Carpenter, Katie Read, James Lee, Ally Lewis,

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Cape Verde Atmospheric Observatory (CVAO) 16° 52' N, 24° 52' W

Oxygenated volatile organic compounds in the remote marine troposphere: Results from the Cape Verde Atmospheric Observatory

Lucy J. Carpenter, Katie Read, James Lee, Ally Lewis, James Hopkins ‐ NCAS, University of York Luis Mendes, Helder Lopez ‐ INMG, Cape Verde Steve Arnold ‐ Earth and Environment, University of Leeds Rachael Beale, Phil Nightingale – PML, UK

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Measurement Method Met stations at 10, 30m Various O3 UV absorption NO/NOx/NOy Chemiluminesence CO VUV Fluorescence C2 -C8 NMHCs and DMS dc-GC-FID C1 -C5 O-VOC dc-GC-FID Halocarbons GC-MS JO1D Radiometer

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Oxygenated volatile organic compounds (OVOCs)

N

Methanol Acetaldehyde Acetone

Atmospheric OVOCs

Cape Verde Atmospheric Observatory (CVAO)

Ocean: source or sink? Biogenic sources Anthropogenic and biomass burning sources

OH loss in marine boundary layer

Primary and secondary sources

CH3 C(O)O2 NO2 PAN HO2organic acids HCHO, HOx , CH3 O2 h, O2 , OH h, O2 , OH

Source of HOx , O3 and PAN

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CAM‐Chem vs measurements

acetone (ppt)

Monthly averages Dominated by anthropogenic emissions (39 %‐91 %)?

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Are MBL acetone concentrations controlled by anthropogenic NMHC?

10 100 1000 10 100 1000 10000

acetone (pptV) propane ( pptV)

propane (ppt)

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OVOC Water Measurements

  • N
  • S

Acetaldehyde (nM) Latitude

  • Methanol,

acetaldehyde and acetone quantified in seawater via MI- PTR/MS

Acetaldehyde in Mauritanian Upwelling (ICON)

Filament 1 Filament 2

Acetaldehyde (nM) Days since patch initiation (T0 )

AMT track

Beale, R. Quantification of oxygenated volatile organic compounds (OVOCs) in seawater, 2011, Ph.D thesis, University of East Anglia, UK. Manuscripts in preparation.

Role of the oceans?

CDOM CDOM

hv

OVOC

  • Jacob et al. (2002)‐
  • cean a

significant source of acetone

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Modelled oceanic acetone fluxes

  • Sea‐air flux F

= kt (Cw – Ca /H) l/kt = 1/kw + 1/Hka

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How does this change model results?

500 1000 1500 2000 2500 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec acetone (pptV) 500 1000 1500 2000 2500

01/01/2007 20/02/2007 11/04/2007 31/05/2007 20/07/2007 08/09/2007 28/10/2007

10th‐90th percentile range Mean (measurements) CAM‐Chem STD model STD‐NOANTH STD‐NOBIO STD‐NOFIRE CAM‐Chem model with ocean

Cumulative LAI (m2 m-2)

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Biological (terrestrial) influences

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Could model bias be due to underestimated biogenic emissions?

y = 20.02x + 0.59 R

2 = 0.39

y = 3.39x + 0.28 R

2 = 0.71

y = ‐3.08x + 3.44 R

2 = 0.83

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 Fractional contribution to acetone O b s e rv e d /m od e lle d

Fractional contribution from biogenic (green), anthropogenic (purple) and biomass burning (red) sources as calculated from CAM‐Chem. Grey lines indicate 1:1 observation:model agreement.

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Methanol

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Modification of atmospheric methanol by oceans

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Acetaldehyde

10 100 1000 1 10 100 1000 10000

acetaldehyde (pptV) propane (pptV)

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Acetaldehyde modification by oceans

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Impact of OVOCs on diurnal mean MBL [OH]

OVOC concentrations from: (i)observations at Cape Verde (ii)monthly‐mean CAM‐Chem model output including ocean fluxes (iii)set to zero CittyCat box model simulations

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50 100 150 200 250 Oct/06 Dec/06 Jan/07 Mar/07 May/07 Jul/07 Sep/07 Nov/07 Jan/08 Mar/08 CO (ppbV)

Using nOH (fossil fuel and biomass) methane oxidation terrestrial nmhc oxidation (mainly isoprene)

  • ceanic voc oxidation

terrestrial ovoc oxidation

Indirect impact: OVOC as sources of CO

Additional % contribution from summer CO emission sources not shared by ethane Reference Methane oxidation 5 % (May-October) Granier et al., 2000 NMHC oxidation 12 % (May-October) Granier et al., 2000 Terrestrial

  • VOC
  • xidation

20 % (June-November) Miller et al., 2008 Oceanic NMVOC

  • xidation

20 % (July-September) Guenther et al., 1995

50 100 150 200 250 Oct/06 Dec/06 Jan/07 Mar/07 May/07 Jul/07 Sep/07 Nov/07 Jan/08 Mar/08 CO (ppbV)

Using nOH (fossil fuel and biomass) methane oxidation terrestrial nmhc oxidation (mainly isoprene)

  • ceanic voc oxidation

terrestrial ovoc oxidation

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Conclusions

  • Oxygenated VOCs are a significant direct sink of OH in the

MBL

  • Their abundance in the remote marine environment is

underestimated (particularly CH3 CHO)

  • Marine and biological terrestrial sources of OVOCs could

explain some of this model underestimation – more work required to establish emission strength and variability

  • >C3 alkanes and alkenes – chemistry and emissions
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Acknowledgements

Funding: Technical support at CVAO: Luis Mendes Neves Helder Lopez

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Modelled (GEOS‐5) and measured wind speed

  • With a squared wind dependence for sea‐air fluxes, the difference between

10 m s‐1 and 6 m s‐1 is a factor ~3.