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Fossil and modern sources of aerosol carbon in the Netherlands – A year-long radiocarbon study

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 ,

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Fossil and modern sources of aerosol carbon in the Netherlands – A year-long radiocarbon study

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  1. 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 Netherlands 3 Laboratory for Radiochemistry and Environmental Chemistry, University of Bern, Switzerland

  2. Radiocarbon Carbon isotopes: C12 : 98.89 % C13: 1.11 % C14: 0.0000000001% Half life: 5730 yrs Produced by cosmic rays Unit of measurement: Fraction modern fm = 14C sample/14C standard Standard: oxalic acid (typical activity of 1950 biosphere) fm > 1 possible through bomb tests Exchange with Biosphere as 14CO2 Decay when Exchange with Biosphere stops

  3. Carbonaceous aerosol: 14C for source apportionment fm = 1.1 - 1.2 fm = 0 fm ~ 1.04 Biomass burning Biogenic Fossil fuel EC OC Thermally refractory Volatile - refractory

  4. From aerosol particles to 14C measurement Sampling: Goal: 50 – 500 ugC High volume samplers: 500 l/min of air through filter Convert OC and EC to CO2 Measure 14C content with AMS

  5. Combustion in pure oxygen TC 15 min at 650 C 2 min at 450 C 15 min at 360 C 15 min at 650 C WIOC Carbonaceous aerosol Water extraction RC 15 min at 360 C Pump away OC

  6. Time series Marine Very dry spring Continental Very dry Fall Mixed Very rainy Cold summer

  7. Time series Marine Continental Mixed

  8. Seasonal variation fm: WSOC > OC > TC > WIOC > EC Least seasonal variation in WSOC Most in EC Highest fm in spring

  9. Contribution of biomass burning to EC Detection level of our method? Why so high in spring? Possible biological influence? Fires in the spring

  10. Dependence of fm on carbon concentration Pollution events Low concentrations of TC: low fm Very high concentrations of TC: low fm At moderate TC concentrations 1- 5 ug/m3: variations in TC concentration caused by modern source

  11. Correlation of fm WIOC and EC fm(WIOC), fm(EC) correlated Common modern source Extra biogenic background source for WIOC

  12. Day-night variations Higher fm during night: Higher traffic emissions during day Condensation of semi-volatile biogenic organic during night

  13. 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

  14. 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

  15. Contamination: Analysis of standards with known 14C content Comparison with typical sample size and handling blank values

  16. Time series

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