Speciation of water-soluble organic carbon compounds in boundary layer aerosols during the LBA/CLAIRE/SMOCC-2002 campaign Magda Claeys 1, Vlada Pashynska 1, Reinhilde Vermeylen 1, Gyorgy Vas 1, Jan Cafmeyer 2, Willy Maenhaut 2, and Paulo Artaxo 3 1 Department of Pharmaceutical Sciences, University of Antwerp, Antwerp, Belgium 2 Institute for Nuclear Sciences, Ghent University, Gent, Belgium 3 Institute for Physics, University of São Paulo, São Paulo, Brazil  Organic aerosol is the major aerosol type in biomass burning (pyrogenic) and biogenic aerosols  A major fraction of the organic aerosol is water-soluble and may affect the cloud-nucleating properties of aerosol particles  Characterisation of the water-soluble organic carbon (WSOC) is a complex task, but is of importance for assessing the physico-chemical properties of the organic aerosol and for estimating the relative contributions from pyrogenic and biogenic sources 1. Introduction Tropospheric aerosol research team from Ghent University (UGent) participated in the field work of the LBA/CLAIRE/SMOCC experiment in Amazonia, September-November 2002 [Maenhaut et al., 2003]  several UGent aerosol collection devices set up at Fazenda Nossa Senhora (FNS), Rondônia UGent high-volume filter sampler for organic analysis  R1HiVo: Hi-Vol sampler, which provides separate fine ( 2.5 µm AD) size fractions –double Pallflex quartz fibre filters (of 102 mm diameter) used for each of the two size fractions –the filters had been pre-heated at 550  C to remove organic contaminants Aerosol samplings: from 9 September to 14 November 2002 (66 days) Figure 3 shows the time trends for fine PM (PM2), and for organic matter (OM, estimated as 1.6*OC), EC, and levoglucosan in the fine filters of R1HiVo  all 4 parameters show substantial variation throughout the campaign and are fairly well correlated with each other  several episodes with high levels, because of the impact from biomass burning Figure 4 shows levoglucosan carbon as a percentage of the OC  data for daytime samples are in green, for night time samples in red  interesting diel differences are observed, which may be related to the more shallow boundary layer during night  clear that levoglucosan contributes more to the OC during night (on average 3.3  1.0% during night versus 2.0  0.6% during the day) Figure 5 shows the time trends for levoglucosan, malic acid, and 2-methylerythritol  malic acid and 2-methylerythritol exibit much less (and different) variability than levoglucosan (an excellent indicator for biomass burning) –indicates that they originate from other sources Median concentrations (and concentration ranges) for OC, EC, and the various compounds measured by GC/ion trap MS are given in Table 1  levoglucosan is the dominant organic compound –its concentration (and that of OC) resembles that observed at the same site during the 1999 “burning” season [Graham et al., 2002; Zdráhal et al., 2002]  malic acid and 2-methylerythritol (indicators of photo-oxidation of natural volatile organic compounds) are characteristic of the natural background and are also important organic compounds –the concentration of malic acid is similar to that reported for the 1999 “burning” season at the same site [Graham et al., 2002] –the levels of malic acid and of 2-methylerythritol are of the same order as those found during the CLAIRE-2001 “wet” season campaign at Balbina (north of Manaus) [Claeys et al., 2003]  as could be seen from Figure 3, PM2, OC, EC, and levoglucosan were fairly well correlated with each other –this was also apparent from the R 2 values with OC, which were 0.97 for PM2, 0.92 for EC, and 0.86 for levoglucosan (with N = 74)  several organic compounds were well correlated with levoglucosan, i.e., mannosan (0.98), glucofuranose (0.91), and galactosan (0.93) [data in parentheses are R 2 values], indicating that they are also associated with pyrogenic emissions –also glucose somewhat correlated with levoglucosan (R 2 of 0.61)  in contrast, other compounds were not at all correlated with levoglucosan, e.g., malic acid and 2-methylerythritol with R 2 values of 0.08 and 0.07, resp.  the enantiomers 2-methylthreitol and 2-methylerythritol were well correlated with each other (R 2 of 0.87) Acknowledgements This research was funded by the European Commission (contract no. EVK2 ‑ CT2001 ‑ 00110), the Belgian Federal Office for Scientific, Technical and Cultural Affairs, and the Special Research Fund of Antwerp University. We are grateful to Xuguang Chi for assistance with the analyses for OC and EC, and to Sheila Dunphy for technical assistance. References Birch, M.E., R.A. Cary, Aerosol Sci. Technol. 25 : 221, Claeys, M., et al., submitted manuscript, Graham, B., O.L. Mayol-Bracero, P. Guyon, G.C. Roberts, S. Decesari, M.C. Facchini, P. Artaxo, W. Maenhaut, P. Köll, M.O. Andreae, J. Geophys. Res. 107 (D20), 8047, doi: /2001JD000336, Maenhaut, W., A. Onjia, X. Chi, J. Cafmeyer, V. Pashynska, R. Vermeylen, G. Vas, M. Claeys, Joint International Symposium on Atmospheric Chemistry, Program and Abstracts, Heraklion, Crete, Greece, p. 161, Maenhaut, W., J. Cafmeyer, X. Chi, S. Dunphy, N. Raes, P. Artaxo, see poster board P0823 at this Assembly, Pashynska, V., R. Vermeylen, G. Vas, W. Maenhaut, M. Claeys, J. Mass Spectrom. 37 : 1249, Zdráhal, Z., J. Oliveira, R. Vermeylen, M. Claeys, W. Maenhaut, Environ. Sci. Technol. 36 : 747, Aerosol collections 4. Time trends and median concentrations 5. Correlations between selected species 3. Chemical analyses 6. Mass fraction of OC explained by the organic compounds Table 2 presents the mean percent carbon (and associated standard deviation) of the OC that is attributed to the various organic compounds measured in this study  levoglucosan provides the major contribution (2.5%) and all compounds together account for 4.1%  these two percentages are quite similar to those found for “total” (PM10) filter samples from SAFARI 2000 (where they were 2.5% and 4.9%, resp.) [Maenhaut et al., 2002]  in contrast, for arabitol, mannitol, glucose, and fructose, 5 to 10 times lower percentages are found than for the SAFARI 2000 “total” filter samples –these compounds are presumably mainly associated with the coarse particles Table 2 Mean percentages (and associated standard deviations) of the fine (<2.5 µm AD) OC attributable to the carbon in the organic compounds (data derived from R1HiVo; N = 74). Species Mean % ± std. dev. Levoglucosan 2.5 ± 1.0 Mannosan 0.18 ± 0.07 Galactosan 0.07 ± 0.03 Glucofuranose 0.12 ± 0.05 Arabitol 0.04 ± 0.03 Mannitol 0.07 ± 0.06 Erythritol 0.02 ± 0.01 Glucose 0.12 ± 0.10 Fructose 0.03 ± Methylthreitol 0.10 ± Methylerythritol 0.32 ± 0.24 Malic acid 0.45 ± 0.32 Sum 4.1 ± 0.9 Table 1 Median concentrations and concentration ranges in the fine (<2.5 µm AD) size fraction during the LBA/CLAIRE/SMOCC-2002 campaign (derived from R1HiVo; N = 74). Data for OC and EC are in µg.m –3 ; for all other species in ng.m –3. Species Median conc. Conc. range OC (µg.m –3 ) – 61 EC – 3.8 Levoglucosan – 6100 Mannosan – 440 Galactosan – 210 Glucofuranose – 360 Arabitol 10.4 DL – 34 Mannitol – 43 Erythritol – 30 Glucose – 107 Fructose 9.8 DL – 36 2-Methylthreitol – 81 2-Methylerythritol – 250 Malic acid – 570 Fig. 1 All filters from R1HiVo analysed for organic carbon (OC) and elemental carbon (EC) by a thermal-optical transmission (TOT) technique [Birch and Cary, 1996] Fine front filters  for 74 samples: 1/16 or 1/32 fraction of the front filter extracted with methanol:dichloromethane mixture  analysis for levoglucosan, related saccharidic compounds, and malic acid with a gas chromatography/ion trap mass spectrometry method (GC/ion trap MS) adapted from Pashynska et al. [2002]  the analytical procedure is presented in Figure 1  total ion chromatogram obtained for sample 15D (collected on 23 Sept., daytime) is shown in Figure 2 –levoglucosan is the major organic compound detected, but it can be noted that malic acid and 2-methylerythritol [Claeys et al., 2003] also give rise to prominent peaks in the chromatogram Fig. 2 Fig. 3 Fig. 4 Fig. 5