Secondary aerosol formation and their modeling

Measurement studies using particle into liquid sampler coupled with an ion chromatograph (PILS-IC), aerosol mass spectrometer (AMS), or aerosol chemical speciation monitor (ACSM) show a large fraction of organics and sulfate in fine particles in summer over the western and eastern Mediterranean. Different formation pathways of organic aerosol (OA), from anthropogenic and biogenic precursors of continental or marine origin, are discussed and quantified, using observations and modeling. The contribution of specific formation pathways, such as autoxidation of biogenic VOC precursors, is estimated. OA properties and their seasonal variation, in particular oxidation state and related solubility, are discussed. The temperature sensitivity of secondary OA formation differs for different aerosol modeling schemes, which is important to take into account when predicting aerosol in a future warmer climate. Over the Mediterranean, sea salt is an important fraction of the coarse aerosol and interacts with the soluble organic aerosol.