High-energy radiations, such as alpha and beta particles or gamma radiation, ionize air molecules into pairs of positive ions and free electrons. The diurnal and seasonal variations of these air ions were measured for the first time at a rural monitoring station in Ramanandnagar (17°2'N, 74°E), India, and the urban tropical station in Pune (18°31'N, 73°55'E)

The air ions are continuously generated and destroyed by various processes in the atmosphere. Near the surface, the nature of ions is very complex and they show large variations in their physical properties. The attachment of small ions to the aerosol particles is depending on the mobility of air ions. High mobility air ions immediately are attached to the aerosol particles and settle down on the surface. In this study we report, about the air ion variation at different sites like Rural, Coastal, Mountain, Poultry farm and urban in the state of Maharashtra in India. The aim of this study is to understand the plausible distribution of air ions both diurnally and at different times in a day for long time (three years) and with various meteorological variables. The preliminary analysis of the data has reveled that negative air ions are observed to have attached to the aerosol particles and large aerosol particles are formed from small aerosol particles. Therefore uni-polarity factor observed to be below unity for coastal, mountain and rural site and about 2.8 at an urban site. However worst case is observed at the Poultry farm, where uni-polarity factor is 6.3, which is very harmful for human health. There is also effect of meteorological parameters on air ion concentration in the atmosphere.

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In the present study, the observation of indoor air ion concentration at a rural site has been carried out for the first time. These indoor observations are compared with outdoor air ion concentration. Net charge can be introduced into the atmosphere by processes such as combustion, rainfall and ultraviolet radiation. As compared to indoors, average air ions of both the polarities at outdoors are higher. Moreover, the air ion concentrations, experience large fluctuations during daytime, as compared to nighttime values. Positive and negative air ion concentrations are lower and uniform throughout the night both for indoor and outdoor conditions. Pollution index is more or less unity for outdoors in all-the-time period, which is good for human health. Due to limited sources of air ions indoors, it is observed that pollution index decreases from 00:00-02:00 hours and minimum is reached during 12:00-14:00 hours for indoors. During 00:00-02:00 hours, the indoor pollution index is 1.55, which is very harmful to human health.