Open AccessSeasonal variation of high‐molecular‐weight compounds in the water‐soluble fraction of organic urban aerosols
Author(s) -
Samburova V.,
Szidat S.,
Hueglin C.,
Fisseha R.,
Baltensperger U.,
Zenobi R.,
Kalberer M.
Publication year - 2005
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2005jd005910
Subject(s) - aerosol , size exclusion chromatography , environmental chemistry , mass spectrometry , air mass (solar energy) , mass spectrum , ozone , mass fraction , chemistry , analytical chemistry (journal) , chromatography , organic chemistry , physics , boundary layer , thermodynamics , enzyme
Aerosol samples were collected in Zurich, Switzerland, at an urban background site and were analyzed with size exclusion chromatography (SEC) and laser/desorption ionization mass spectrometry (LDI‐MS) for water‐soluble organic compounds with high molecular weight. Daily samples were collected during two campaigns in winter and summer, for 1 month each. The concentration of high‐molecular‐weight compounds (humic‐like substances (HULIS)) was between 0.4 and 4 μg/m 3 in winter and summer. The most intense signals in the LDI‐MS mass spectra were measured between m/z150 and 500, comparing well with the mode of the two main high mass peaks determined with SEC corresponding to masses between 200 and 600 Da. For the maximum molecular weight, however, different results were obtained by the two techniques: whereas a maximum molecular weight between 1300 and 3300 Da was found with SEC, hardly any peaks above m/z700 were measured with LDI‐MS. During summer the maximum molecular weight of HULIS (determined with SEC) correlates positively with several parameters such as ozone and increased temperature indicative of enhanced atmospheric photo‐oxidation. The HULIS concentration also correlates positively with the oxalic acid concentration in the particles. This suggests that HULIS are generated by secondary processes in summer. The lack of such correlations during winter suggests that other sources and processes might be important during colder seasons.