Wet and dry deposition fluxes of
major ions and trace elements to
the South Atlantic
Rosie Chance, Alex Baker, Tim Jickells, Alina Marca
School of Environmental Sciences, University of East Anglia.
Overview
1. Introduction
• GEOTRACES objectives wrt. aerosol
• Carcass Island
2. Sampling and analytical methods
3. Results
• Trace metals
• Macronutrients
• Nitrate isotopes
4. Titanium in seawater
5. Summary and future work
Introduction
GEOTRACES
GEOTRACES objectives
• Constrain magnitude and spatial
distribution of atmospheric flux of TEIs to
the surface ocean.
• Global database quantifying sources of
micronutrients for use in models
• Global-scale ground-truthing of aerosol
deposition models
• Establish range of fractional solubility of
key TEIs
Introduction
Patagonian dust
Why the south Atlantic?
Baker (UEA) – Atlantic database
Methods
Field sampling
Sampling
Methods
Sampling
Carcass Island: A new time series station
• In operation:
Sept 2010 – April 2011
Oct 2011 – April 2012
• Weekly bulk aerosol
samples
Methods
Challenges….
Sampling
Methods
Extraction & Analysis
Sample analysis
Analyte
Method
Nitrate, sulphate, chloride
Ammonium
Ion chromatography
Nitrate isotopes
Bacterial denitrification +
IRMS
Sodium, potassium, calcium,
magnesium
ICP-OES
Trace metals:
Fe, Al, Mn, Zn, V, Ti, Co, Ni,
Cu, Ag, Cd, Pb, Th
ICP-OES & ICP-MS
Total metals
INAA
Deposition flux = Catm • Vd
Results
Trace metals
nmol m-2 day-1
Dry deposition of soluble trace metals
<LoD
Results
Trace metals
nmol m-2 day-1
Dry deposition of soluble trace metals
<LoD
GEOTRACES
Spatial distribution e.g. Al
Results
Principal component analysis
Qualitative differences in aerosol chemical
composition
Results
Back trajectories
Results: Air mass origin
CARCASS
D357
D361
5 day back trajectories calculated using NOAA HYSPLIT model
JC68 Back trajectories
GEOTRACES
Aerosol optical depth
D361
D357
JC68
http://aeronet.gsfc.nasa.gov/new_web/maritime_aerosol_network.html
Results
Trace metals
Contribution of wet deposition
nmol m-2 day-1
S
O
L
U
B
I
L
I
T
Y
CARCASS
D357
D361
Fe
wet
dry
ratio
967
948†
1.0
2109
243*
8.7
4741
3127
1.5
Al
wet
dry
ratio
2068
326†
6.3
1845
76
24.3
14101
13064
1.1
Mn
wet
dry
ratio
64
18†
3.6
83
7
11.9
233
70
3.3
Zn
wet
dry
ratio
223
16†
13.9
1785
8*
223
3104
54*
57.5
† Estimated from soluble fluxes
* Based on max total metal concentration
Results
Macronutrients
Macronutrient deposition
 Wet deposition
Climatology data
(Baker et al., 2010).
μmol m-2 day-1
NH4+
NO3-
West
0.5-0.9
1.9-2.5
East
0.8
2.5
Results
Nitrate isotopes
Nitrate stable isotopes: Carcass Island
Results
Nitrate isotopes
Nitrate stable isotopes: D357
Results
The bigger picture
Climatological approach
Shipboard sampling = “snapshot”
Decoupled from water column
 Flux estimates from larger
data sets, where available!
Aerosol databases:
• GEOTRACES
• COST Action 735
Baker et al., 2010. GBC.
JC68
Titanium
Titanium in the water column (JC68)
Details in cruise report
Summary
• Preliminary TM and nutrient fluxes available (wet, dry
soluble and dry total)
• Dry deposition fluxes very low in the south Atlantic
• Wet deposition fluxes equal to or larger than dry
deposition
Future work
• Sample analysis:
• JC68 cruise
• Carcass Island yr 2, including volcanic ash
• Links to water column data?
• Data compilation/synthesis papers
• East Atlantic
• West Atlantic?
Acknowledgements
Thanks to all who have
helped make the project
possible, especially….
• Rob and Lorraine McGill
• Michael Clarke, Clive Wilkinson,
Nigel Bishop, Arlette Betts and
many others in the Falklands.
• British Antarctic Survey
• Officers, crew and science party
of D357, D361 and JC68