Temporal Variation of Atmospheric Static Electric Field and Air Ions and their Relationships to Pollution in Shanghai

Atmospheric electric field (EF) and air ions were measured in Shanghai from December 2014 to December 2015 to examine the influence of particulate pollutants. Fair-weather EF exhibits a diurnal variation of multi-modal oscillations in spring, summer, and autumn. Linear correlation analyses show that the local meteorological conditions of relative humidity, temperature, pressure and wind affect atmospheric electric field, with wind direction exhibiting the highest correlation coefficient. Atmospheric EF is significantly higher in the west compared with that in the east, as the air mass from inland areas carries more polluted aerosols. Air ion concentrations are generally higher in the daytime than at night and correlate with meteorological factors. Atmospheric EF undergoes a substantial fluctuation in polluted periods, but remains flat under clean conditions. Overall, in areas with pollution, the atmospheric EF gradually increases with increased pollution or increased particle loading (e.g., PM2.5), a useful indicator of air pollution. The concentration of PM2.5 is positively correlated with the atmospheric electric field under polluted conditions, because as the concentration of aerosol particles declines, the concentrations of small ions and the atmospheric conductivity decrease accordingly, thus causing an increase in the electric field. Overall, aerosol particles, air ions, and their interactions in the presence of various meteorological parameters can have local effects on the atmospheric electric field.