Molecular size of surfactants affects their degree of enrichment in the sea spray aerosol formation.

ABSTRACT

Sea spray aerosol (SSA), the largest source of natural primary aerosol, plays an important role in atmospheric chemical processes and the earth radiation balance. Its formation process is controlled by many factors. In this study, ethylene glycol (EG) and polyethylene glycol (PEG) with three different molecular weights (200, 400, 600) were used to investigate the influence of molecular size on the properties of submicron SSA produced by plunging jet from an adjustable home-built SSA generator. Different parameters were tested to obtain the optimum experimental conditions. The addition of EG and PEG inhibited the production of SSA and increased the geometric mean diameter (GMD) between 10 and 35 nm. However, PEG with a molecular weight of 600 could promote the production of SSA at higher concentrations, which means that the molecular weight and concentration of the polymer would affect the production efficiency of SSA. Combining with the measurement of surface tension, we found no clear relationship between surface tension and the yield of SSA, due to the properties of the substances themselves. Transmission electron microscopy images show that the addition of EG and PEG could significantly change the structure of salt nuclei in SSA. PEG was significantly enriched in SSA (with enrichment factors within the range 92.9-133.4), and the enrichment was independent of the sampling time, while increasing with the increase of molecular weight. Our results highlight the influence of polymer molecular weight on the properties of SSA, and their importance to improve the accuracy of aerosol emission model parameters.