Aircraft study of cloud water chemistry over Jilin Province in Northeast China

24 cloud water samples were collected aboard an aircraft over Jilin province during June-July 2007. The pH values and concentrations of major water-soluble ions were analyzed. The results showed that the cloud water was obviously acidified, with a mean pH value of 4.93. The dominant ions were SO42-, NH4+, Ca2+, and NO3-, with mean concentrations of 109.7, 74.8, 71.9, and 51.4 μeq/L, respectively. The equivalent ratio of SO42-/NO3-was 2.1, which is comparable to that of the precipitation at Longfengshan. The concentrations of ions in cloud water were mainly affected by synoptic weather condition and long-range transport patterns. Ensemble trajectory analysis revealed that the cloud water with the highest ion concentrations was affected by the regional transport of air pollution from the North China Plains. Comparison of cloud water with rain water samples at ground level suggests that the acidity of rainfalls can be neutralized during the washout process.