Hygroscopic Properties of 11 Pollen Species in China

Pollen, one of the most abundant types of primary biological aerosol particles, has significant impacts on human health, climate, and ecosystems. However, the hygroscopicity of pollen species in China remains to be unknown. In this work, we explored for the first time hygroscopic properties of pollen species widely found in China. Six anemophilous and five entomophilous pollen species (11 in total) were studied, and measurements were conducted as a function of relative humidity (RH, up to 95%) at two temperatures (25 and 37 degrees C). All 11 pollen species examined were found to show moderate hygroscopicity; the sample mass at 90% RH, normalized to that under dry conditions, was found to range from 1.33 to 1.43 at 25 degrees C, and the single hygroscopicity parameter (kappa) was derived to be 0.036-0.048. No significant difference in hygroscopicity between anemophilous and entomophilous pollen species was observed, and the effect of the temperature (25 versus 37 degrees C) on pollen hygroscopicity was found to be small.