Chemical composition and bacterial community in size-resolved cloud water at the summit of Mt. Tai, China

Abstract

A three-stage collector was used to collect size-resolved cloud samples at the summit of Mt. Tai. Subsequently, analyses of pH values, water-soluble ions, and trace metals were performed and bacterial community were conducted using MiSeq amplicon sequencing. The pH values of the samples decreased as droplet sizes decreased. Sulfate (SO42–), nitrate (NO3–) and ammonium (NH4+) were the main secondary inorganic ions which their concentration distributed significantly different from size-resolved cloud water. The NH4+ concentration was higher in smaller droplets. The SO42– and NO3– concentrations were higher in larger droplets. The Ca2+ concentration increased as droplet size increased. Small droplet samples tended to have lower pH value, mainly because of the more acidic (SO42– and NO3–) and less acid-neutralizing (NH4+ and Ca2+) components. The bacterial community in size-resolved cloud samples were firstly recognized and dominated by the genera of Lactococcus (average abundance 34.9%) and Bacillus (average abundance 34.0%). Linear discriminant analysis effect size (LEfSe) revealed differences of the bacterial community in size-resolved cloud water samples, which was probably caused by the bacterial size. Redundancy analysis suggested several minor correlations that the H2O2, NO2– concentrations, and trace metals exert effects on the bacterial community.