Water-soluble hydroxylated organic compounds in German and Finnish aerosols

Total suspended particulate matter was collected in a German anthropogenically influenced agricultural area and in a Finnish forest. The occurrence of water-soluble compounds leftover by a traditional dichloromethane (DCM)-extraction technique was investigated using an additional water-extraction and analyzing the corresponding trimethylsilyl derivatives by GC-MS. The organic carbon content of the samples and extracts was also measured. The additional extraction with water recovered more than 20% of total organic carbon, which is comparable to the 31% extracted with DCM. The fraction of water-extractable organic carbon that eluted was <10%, but the employed GC-MS approach proved to be useful in the identification and quantification of polar water-soluble organics containing hydroxyl groups. Concentrations and size distributions of polyhydroxymono- and dicarboxylic acids, polyols, and sugars were obtained. The German meadow presented the highest levels of sugars and acidic compounds, whilst polyols were the most abundant class in the Finnish forest. The major compounds of these classes were malic acid, mannitol, arabitol, glucose and sucrose. Levoglucosan was also detected in the water-extract. Acidic compounds occurred mainly in fine particles. Polyols and most sugars presented size distributions with variable fine or coarse maximum. Possible primary and secondary sources of polyhydroxylated compounds are discussed.