Charging states on atmospheric aerosol particles affected by meteorological conditions

Previous studies on haze formation focused mainly on the various chemical components in aerosol particles and their physicochemical effects on particle behaviour (e.g., generation, growth, and agglomeration). This paper describes the measurement of the charging state on atmospheric aerosol particles, which could be affected by meteorological conditions. A series of experiments on particle charging state and meteorological factors was undertaken on the roof of the west 4th building on the Qujiang Campus at Xi'an Jiaotong University (China). Measurements were conducted approximately 20 m above ground level. Our results showed that most atmospheric particles carried net negative or positive charge and that the electric charge on the particles varied diurnally and seasonally. The average amount of charge on particles was higher in winter than in summer. The number concentration of charged particles was higher during the day than overnight. Obvious difference in the average charge of aerosol particles was found between sand–dust days and haze days. A strong relationship was found between the PM_2.5 concentration, charge amount on particles, and humidity. Our findings show that particle formation and growth could partly be attributed to variation in particle charging state, which is related to meteorological conditions including atmospheric humidity.