Hygroscopicity of nanoparticles produced from homogeneous nucleation in the CLOUD experiments

摘要: Abstract. Sulfuric acid, amines and oxidized organics have been found to be important compounds in the nucleation initial growth of atmospheric particles. Because challenges involved determining chemical composition objects with very small mass, however, properties freshly nucleated particles detailed pathways their formation processes are still not clear. In this study, we focus on a challenging size range, i.e., that grown diameters 10 15 nm following nucleation, measure water uptake. Water uptake is useful information for indirectly obtaining aerosol We use nanometer-hygroscopicity tandem differential mobility analyzer (nano-HTDMA) at subsaturated conditions (ca. 90 % relative humidity 293 K) hygroscopicity during seventh Cosmics Leaving OUtdoor Droplets (CLOUD7) campaign performed CERN 2012. CLOUD7, nanoparticles was measured presence sulfuric acid–dimethylamine, acid–organics derived from α-pinene oxidation. The parameter κ decreased increasing particle size, indicating decreasing acidity No clear effect acid concentration 10 nm produced dimethylamine observed, whereas sharply concentrations. particular, when 5.1 × 106 molecules cm−3 gas phase, mixing ratio 11.8 ppt, 0.31 ± 0.01: close value reported dimethylaminium sulfate (DMAS) (κDMAS ∼ 0.28). Furthermore, difference between acid–imethylamine experiments increased size. values were much smaller than those dimethylamine. This suggests ozonolysis play significant role even sizes.