Cape Verde Atmospheric Observatory€¦ · at the Cape Verde Atmospheric Observatory (CVAO) Lucy...
Transcript of Cape Verde Atmospheric Observatory€¦ · at the Cape Verde Atmospheric Observatory (CVAO) Lucy...
CVAO
16° 52' N, 24° 52' W
Volatile organic compound observations
at the Cape Verde Atmospheric
Observatory (CVAO)
Lucy Carpenter, Katie Read, Shalini Punjabi, Ally Lewis, James Hopkins, James Lee, -
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
www.ncas.ac.uk/capeverdeobservatory/
Dispersion footprints of air arriving at Cape Verde
1) Atlantic and African coastal, 2) Atlantic marine,
3) North American and Atlantic 4) North American and coastal African,
5) European, 6) African, 7) European and African NAME model. Z. Fleming
Downwind of area of high biological productivity (Mauritanian upwelling)
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l-a
(mg/
m3) MODIS
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
VOC sampling
J.R Hopkins et al. J. Environ.Monit., 5 (1) , 8-13
Dual-bed
adsorbent trap
In-situ sampling
from 10-m tower
Condensation trap
10m LOWOX
column
50m PLOT
column
FID 2 FlD 1 Agilent
6890
Per Carbon Response factor (P.C.R.F)
Calibration: NMHCs
•Multi component VOC mixture NPL- 30 component mix (4 ppb range)
•Calibration frequency : every two-four weeks
Results of GAW audit for NMHCs
• RSD of CVAO NMHC cals < 2% for most compounds
R.f. of OVOC = conversion
factor x Response factor of
propane
Precision ~ 15%
Estimated accuracy ~ 20%
Calibration: OVOCs
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0.025
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a/p
pb
v/m
l a)
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area
/ppb
v/m
l
b)
0.000
0.003
0.006
0.009
0.012
area
/ppb
v/m
l c)
Black squares = permeation
tubes (Kintek)
Grey squares = relative
response to propane based on
Apel-Reimer 14 component mix
standard analysed in York 2005
Error bars = average standard
deviation (1 ) of the perm tube
measurements
methanol
acetone
acetaldehyde
Integration – GC Werks
NMHC time series
First-look trends (Apr-May averages)
First-look trends (Apr-May averages)
CO flask data
from M.
Heimann,
Jena
Ethane
CH4 (Monthly mean - 5 year running mean)
Ethane and CH4 growth rate
CH
4 (
5 y
ea
r ru
nn
ing
me
an
)
Methane data
from M.
Heimann, Jena
• 1985-2010 saw global ethane decline of 190 pptv
(24%) (Simpson et al., Nature, 2012)
• Declining fugitive fossil fuel emissions
• At CVAO, [ethane] and CH4 growth rate fairly
stable over last 5 years
Biogenic VOCs: Isoprene
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m3 )
MODIS
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Iso
pre
ne
/ p
ptv
hourly data
monthly average with std dev
Comparison of model with CVAO isoprene data
Arnold et al., ACP, 2009. Model runs for Cape Verde.
Observations generally fall between lower and upper estimates of marine isoprene emissions
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10
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iso
pre
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tv)
top down 1.7 Tg C/yr
bottom up 0.27 Tg C/yr
2008/2009/2010 CVAO data
Daytime maximum in atmospheric isoprene
Mean diurnal cycles in summertime (May-Oct only)
atmospheric isoprene at Cape Verde 2006-2010
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iso
pre
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em
issi
on
s, m
ole
c cm
-2s-1
Predicted oceanic isoprene emissions
Liakakou et al. 2010 (eastern Med) : Inferred fluxes of 108 molec cm-2 s-1
(March) to 6 x109 molec cm-2 s-1 (June) from atmospheric meas
Gannt et al. 2009: Predicted fluxes from ~5 x105 to 6 x108 molec cm-2 s-1
Emissions calculated from
atmospheric isoprene
measurements and
calculated losses due to OH
and O3
(preliminary data)
•Over tropical waters, marine isoprene-derived SOA could contribute
over 40% of the total sub-micron OC fraction of marine aerosol, and
up to 100% (during midday hours) to sub-micron marine OC fluxes
Marine isoprene-derived SOA?
% contribution of 1 hr averaged daily maximum
isoprene-derived SOA to corresponding total sub-micron marine OC emissions for July --Gantt et al. ACP,
2009
Used 3% yield isoprene-SOA
Predicted
fluxes from ~5
x105 to 6 x108
molec cm-2 s-1
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
CH3C(O)O2
NO2 PAN
HO2 organic
acids
HCHO, HOx, CH3O2
h , O2, OH
h , O2, OH
Source of HOx, O3 and PAN
CAM-Chem vs measurements
acetone (ppt)
methanol (ppt)
acetaldehyde (ppt)
OVOC Water Measurements
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oN
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Acetaldehyde (nM)
Lati
tud
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• Methanol,
acetaldehyde
and acetone
quantified in
seawater via
MI-PTR/MS
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Acetaldehyde in Mauritanian Upwelling (ICON)
Filament 1
Filament 2 A
ceta
ldeh
yd
e (n
M)
Days since patch initiation (T0)
AMT track
Beale, R. Quantif ication of oxygenated volatile organic compounds (OVOCs) in
seawater, 2011, Ph.D thesis, University of East Anglia, UK. Manuscripts in preparation.
Role of the tropical Atlantic oceans?
CDOM
hv OVOC
•Jacob et al. (2002)- ocean a
significant source of acetone
Does inclusion of ocean sources/sinks improve model?
•Better agreement overall
•Missing acetone source in
autumn?
•Missing acetaldehyde all year
round
Biogenic contributions
Biomass
burning
Terrestrial
biosphere
Anthro-
pogenic
Observations
Standard model Ocean model
•Model may be missing
terrestrial biogenic OVOC
emissions
•Model scheme for OVOCs
Constrained by OVOC
observations No OVOCs Ocean model
Effect on [OH]
• Low model bias in [OVOC] may result in up to 25% missing model OH
reactivity
• Underestimation of [acetaldehyde] responsible for ~70% of OVOC
reduction of [OH
• If results representative of oceans, could result in up to 8%
underestimation of the global CH4 lifetime
Acknowledgements
Funding:
Bruno Faria, INMG
Martin Heimann and Lena
Kozlova for CH4 data