2
3
HCOOH
2
C H 3 C (O )O O H
G lyoxal
Isoprene
SV O A
M ethylglyoxal
Isoprene nitrate
C 10 nitrates
C H 2O
C H 3C O O H
C H 3O O H
0
6 C 3 O rg. A cids G lycoaldehyde
ISO P O O H
C 10 = C 15
SV O A
1
P yruvic acid
A rom atics
SV O A
IE P O X
N itrate
from
M ACR
+
M VK
PO A
HAC
-1
C H 3C H O
A cetone
M SA
DM S
C H 3O H
-2
-3
11
10
9
8
7
6
5
4
3
2
C arbon
num ber (n )Evaluation of
The First
Global
Dissolved Organic Carbon
c
Sarah Safieddine and Colette Heald
05/01/2017
1
The Reactive Organic Carbon (ROC) is Essential for Tropospheric
Chemistry
Safieddine, Heald, and Henderson,
2017
Emissions
400 [TgCyr-1]
CO
ROC
415 TgCyr-1
NMVOC: 15 TgC
935 TgCyr-1
OA
Emissions [TgCyr-1]
Biogenic
Anthropogenic/biofuel
Biomass
Oceans(net)
905 TgCyr-1
: 1 TgC
460 TgCyr-1
CH4
oxidation
CO2
1275 TgCyr-1
Deposition [TgCyr-1]
Wet: 272
Dry: 188
ROC is simulated by expanding the GEOS-Chem standard simulation, including:
new emissions and chemistry, expanding the wet and dry deposition scheme,
and ensuring carbon closure.
Seasonal Dissolved Organic Carbon (DOC)
DJF
JJA
Rain
[mm/day]
Atmospheric Reactive
Organic Carbon
(ROC) Column
Concentration
[µgC/m2]
Dissolved Organic
Carbon (DOC)
concentration
[mgC/L]
The global DOC is calculated from the wet deposition flux of atmospheric
reactive carbon divided by the global precipitation.
DOC Simulated vs Observed: Surprisingly Good Agreement!
Iavorivska et al., 2016
Comparison of the 2010 simulated DOC with a 30-year record of available DOC
measurements over different environments and regions, shows a good
correlation
Average Carbon Oxidation State: Derived by GEOS-Chem, Measured by
AMS
The average carbon oxidation state
is metric for the degree of
oxidation of atmospheric organic species, a quantity that necessarily increases
upon oxidation
Kroll et al.,
2011
Mass Spectrometry
techniques
provide
key
Mass
spectrometry
techniques
provide
key information on the chemical
composition of organics, such as the average carbon oxidation state, which can
be derived from GEOS-Chem.
First Average Carbon Oxidation State (OSc) Derived From a
Model
In the dissolved form, DOC OSc is generally higher than ROC OSc due to
increase of solubility upon oxidation
The First Simulated Spatial Average Carbon Oxidation State Safieddine and Heald, in prep
• In the atmosphere, ROC OSc is governed by alkanes with lower
photochemistry (oxidation) leading to a lower OSc in winter of the Northern
Hemisphere
• In the dissolved form, DOC OSc is more uniform and generally higher than
Dissolved Organic
Carbon
Precipitatio
n
Conclusions
Conclusions
and Future Work
• Wet deposition is the largest physical sink of reactive organic
carbon
• Improving the understanding of the composition and
evolution of dissolved organic carbon (DOC) will therefore
provide constraints on atmospheric reactive organic carbon
(ROC) lifecycle
• DOC depends on local sources and chemical processing of
reactive organic carbon, as well as precipitation
• ROC is dominated by chemically reduced
hydrocarbons and acetone and DOC is
dominated
globally
by
semi-volatiles,
formaldehyde, and POA.
• 𝑂𝑆𝑐 is negative for most of ROC and DOC
compounds and is higher in dissolved form
due to increase of solubility upon oxidation.
Focus on the US: analysis of NADP data will provide DOC values and
information on the sample chemical composition for model evaluation.