fossil and modern sources of aerosol carbon in the netherlands – a year-long radiocarbon study
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Fossil and modern sources of aerosol carbon in the Netherlands – A year-long radiocarbon study . U. Dusek 1 , M. Monaco 1 , A. Kappetijn 1 , T . Röckmann 1 S . Szidat 2 , H . A. J. Meijer 3 , J. van der Plicht 3 , - PowerPoint PPT PresentationTRANSCRIPT
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Fossil and modern sources of aerosol carbon in the Netherlands – A year-long radiocarbon study
U. Dusek1, M. Monaco1, A. Kappetijn1, T. Röckmann1
S. Szidat2, H. A. J. Meijer3, J. van der Plicht3, 1 Institute for Marine and Atmospheric research Utrecht (IMAU), the Netherlands
2 Center for Isotope Research, Groningen University, the Netherlands3 Laboratory for Radiochemistry and Environmental Chemistry, University of Bern, Switzerland
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Radiocarbon
Carbon isotopes:C12 : 98.89 %C13: 1.11 %
C14: 0.0000000001%Half life: 5730 yrs
Produced bycosmic rays
Exchange withBiosphere as 14CO2
Decay whenExchange withBiosphere stops
Unit of measurement:Fraction modern
fm = 14C sample/14C standard
Standard: oxalic acid (typical activity of 1950 biosphere)
fm > 1 possible through bomb tests
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Carbonaceous aerosol: 14C for source apportionment
Biomass burning Fossil fuel Biogenic
EC OC
fm = 1.1 - 1.2 fm = 0 fm ~ 1.04
Thermally refractory Volatile - refractory
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From aerosol particles to 14C measurement
Sampling: Goal: 50 – 500 ug C
High volume samplers: 500 l/min of air through filter
Convert OC and EC to CO2 Measure 14C content with AMS
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Combustion in pure oxygen
Carbonaceous aerosol
15 min at 650 C
TC
15 min at 360 C
OC
Water extraction
15 min at 360 C
WIOC
15 min at 650 C
RC
2 min at450 C
Pump away
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Time series
Very dry spring
Very rainy Cold summer
Very dry Fall
Marine
Continental
Mixed
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Time series
Marine
Continental
Mixed
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Seasonal variation
fm: WSOC > OC > TC > WIOC > ECLeast seasonal variation in WSOC
Most in ECHighest fm in spring
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Contribution of biomass burning to EC
Detection level of our method?Why so high in spring?
Possible biological influence?Fires in the spring
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Dependence of fm on carbon concentration
Low concentrations of TC: low fmVery high concentrations of TC: low fm
At moderate TC concentrations 1- 5 ug/m3: variations in TC concentration caused by modern source
Pollution events
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Correlation of fm WIOC and EC
fm(WIOC), fm(EC) correlatedCommon modern source
Extra biogenic background source for WIOC
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Day-night variations
Higher fm during night:Higher traffic emissions during day
Condensation of semi-volatile biogenic organic during night
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Conclusions
• Possible components other than EC in refractory material:
Pollen, other biological things?
fM(TC) lowest in summer, highest in spring
• Overall high values of fM(TC) and fM(OC)
• Pollution events with clear low fM signature
• fM(EC) high in continental air masses, except in summer
• Negligible biomass burning contribution in summer
• Distinct day-night variation with lower fM during day
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Acknowledgements
Thanks to
B. Oyama for assistance with sampling and filter preparation
This study was funded by the Dutch NWO grant number 820.01.001
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Contamination: Analysis of standards with known 14C content
Comparison with typical sample size and handling blank values
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Time series
0
10
20
30
40
50
60
70
80
90
100Total Carbon
date
fm (%
)