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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. Rckmann 1 S. Szidat 2, H. A. J. Meijer 3, J. van der Plicht 3, 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 U. Dusek 1, M. Monaco 1, A. Kappetijn 1, T. Rckmann 1 S. Szidat 2, H. A. J. Meijer 3, J. van der Plicht 3, 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

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Radiocarbon Carbon isotopes: C 12 : 98.89 % C 13 : 1.11 % C 14 : 0.0000000001% Half life: 5730 yrs Carbon isotopes: C 12 : 98.89 % C 13 : 1.11 % C 14 : 0.0000000001% Half life: 5730 yrs Produced by cosmic rays Exchange with Biosphere as 14 CO 2 Decay when Exchange with Biosphere stops Unit of measurement: Fraction modern f m = 14 C sample / 14 C standard Standard: oxalic acid ( typical activity of 1950 biosphere ) f m > 1 possible through bomb tests Unit of measurement: Fraction modern f m = 14 C sample / 14 C standard Standard: oxalic acid ( typical activity of 1950 biosphere ) f m > 1 possible through bomb tests

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Carbonaceous aerosol: 14 C for source apportionment Biomass burning Fossil fuel Biogenic ECOC f m = 1.1 - 1.2f m = 0f m ~ 1.04 Thermally refractoryVolatile - refractory

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From aerosol particles to 14 C measurement Sampling: Goal: 50 500 ug C High volume samplers: 500 l/min of air through filter Sampling: Goal: 50 500 ug C High volume samplers: 500 l/min of air through filter Convert OC and EC to CO 2 Measure 14 C 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 at 450 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 > EC Least seasonal variation in WSOC Most in EC Highest 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 fm Very 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 f m WIOC and EC f m (WIOC), f m (EC) correlated Common 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? f M (TC) lowest in summer, highest in spring Overall high values of f M (TC) and f M (OC) Pollution events with clear low f M signature f M (EC) high in continental air masses, except in summer Negligible biomass burning contribution in summer Distinct day-night variation with lower f M 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 14 C content Comparison with typical sample size and handling blank values

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Time series