n‐Alkanes, fatty acid esters, and fatty acid salts in size fractionated aerosols collected over the Mediterranean Sea

The n-alkanes, fatty acid esters, and fatty acid salts have been analyzed in size fractionated aerosols collected over the Mediterranean Sea using a five-stage cascade impactor. Two main sources of n-alkanes have been identified: terrestrially derived n-alkanes evenly distributed over the whole particle size spectrum and anthropogenic n-alkanes predominantly carried by submicron particles. The comparison between the fatty acid ester (FAE) and fatty acid salt (FAS) particle size distributions allowed an important contribution to be ascertained of the marine source in aerosols ranging from 7.2 to 3.0 μm under rough weather conditions that may be due to larger bubble produced particles. In contrast, FAE and FAS were evenly distributed from the first to the fifth stage, when collected during calm sea surface conditions. Higher values of the degree of unsaturation of FAE and FAS were associated with mass concentration maxima observed on stages 2 and 3 in IMPI aerosol sample whereas lower values were found on the other stages in the same sample, and over the whole particle size spectrum in IMP2 aerosol sample collected during calm weather conditions. The data we present here are discussed in terms of jet and film drop ejections and degradation processes.