DETERMINATION OF CARBONATE CARBON IN PARTICULATE MATTER F. Cavalli, E. Diapouli, A. Karanasiou, K. E. Yttri, C. Theodosi, K. Douglas, M. Gini, K. Eleftheriadis, A. Alastuey, N. Mihalopoulos and J.P. Putaud

ACTRIS initiative involving the following institutes: 1. BACKGROUND Particulate carbonate carbon (CC) is a primary carbonaceous species present in natural ground and building/demolition dust and its concentration is generally significant in Southern European countries. lack of a robust and popular technique to determine CC concentration in atmospheric particulate 2. SCOPE investigate the suitability of selected methods for the determination of particulate carbonate carbon ACTRIS initiative involving the following institutes: Institute of Environmental Assessment and Water Research (IDAEA-CSIC) National Center for Scientific Research “Demokritos” (NCSR -D) Norwegian Institute for Air Research (NILU) University of Crete (UoC) Joint Research Center (JRC), Italy

3. EXPERIMENTAL – CC TEST SAMPLES GENERATION PALLFLEX quartz fiber filters burned at 800 °C for more than 20 hours a commercial carbonate and a natural calcite were used TEST SAMPLES OF CC ONLY with homogeneity better than 6%

5. METHODS for CARBONATE CARBON DETERMINATION 4. SAMPLES 3 samples loaded with commercial calcite, 2 samples with natural calcite, and two blanks were distributed to each laboratory Sample mass was determined gravimetrically Deposit mass ranged between 0.19 and 1.43 mg of carbonate corresponding to 7-60 μg m-3 CaCO3 (face velocity 20 cm s-1) 5. METHODS for CARBONATE CARBON DETERMINATION Acidification Thermal-oxidative pretreatment Thermal optical analysis (TOA)

Test sample CC content from TOA analysis taken as CC reference value 6. VERIFICATION OF CC REFERENCE VALUES: THERMAL-OPTICAL ANALYSIS VERSUS GRAVIMETRIC DETERMINATION CC evolves at ca. 650 degree. In TOA, CC evolves: completely at OC4 with EUSAAR_2 protocol in a sharp peak occurring between OC1 and OC2 steps of NIOSH-online protocol CC TOA μg/cm2 CC gravimetry μg/cm2 The overall CC content recovery was 0.82 (R2=0.95) Possible OC contaminations during sampling or uncertainties in the gravimetric determination can account for recovery < 1 Test sample CC content from TOA analysis taken as CC reference value

7. METHODS for CARBONATE CARBON DETERMINATION i. Acidification (by JRC and IDAEA-CSIC) A suitable glassware containing H3PO4 is directly connected to a OCEC analyser Sample punches are pushed up the needle and located into reactor; then they are briefly submerged and then raised up few times The CO2 evolved from the reaction of CC with H3PO4 is determined by the detector of OCEC analyzer CC by acidification μg/cm2 CC by TOA μg/cm2 Acidification method performance: Average CC recovery of 108% (range: 53%-112%) Method repeatability was better than 9%.

7. METHODS for CARBONATE CARBON DETERMINATION ii. Thermal/oxidative pretreatment (by NILU) Thermal/oxidative pretreatment, i.e. 2 hours at 450 °C in an ambient atmosphere, to remove all OC and EC, and leave carbonate carbon, when present on the filter. After the thermal/oxidative pretreatment, sample punches are analysed by TOA with the EUSAAR_2 protocol: CC content is reduced by 7.3% (range: 0% - 12%), on average, with respect to that of punches from the same sample not subjected to the treatment. Thermal/oxidative pretreatment method performance: it does not significantly affect the carbonate content but its ability to completely remove all OC and EC in real ambient samples it remains undemonstrated yet.

7. METHODS for CARBONATE CARBON DETERMINATION iii. Thermal-optical analysis (by NCSR-D) Is TOA suitable to determine CC content also in the presence of atmospheric OC and EC? A portion of a CC test sample was used as a substrate to collect atmospheric aerosol The new sample, thus composed of CC plus atmospheric OC and EC, is analyzed by TOA with NIOSH-online and EUSAAR_2 protocol TOA method performance: CC recovery of 96% with NIOSH-online protocol by integrating the sharp peak occurring between OC1 and OC2 steps But no distinct carbon peak unambiguously attributable to carbonate, when using the EUSAAR_2 or the traditional NIOSH protocol

8. FUTURE WORKPLAN Generate in laboratory new samples of know CC content and expose them to ambient particulate OC and EC Assess the performance of the selected methods for the determination of carbonate carbon in presence of OC and EC

9. EMEP IOP summer 2012 AEROSOL CARBONATE CARBON: PRELIMINARY RESULTS (JRC) Acidification method applied to determine the CC of sample collected during EMEP IOP summer 2012 Analysis on selected station and samples taking into account the method detection limit of ca. 0.3 μg cm-2 CC On average, CC (μg cm-2) = 0.16 Ca (μg cm-2) - 0.33; R2=0.80 — C/Ca ratio is 0.3 in CaCO3 — Half of aerosol Ca content is present in other forms than CaCO3, i.e. CaO.

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