Study of surface ozone behaviour at urban and forested sites in India

Surface ozone concentrations were measured continuously at Pune for a period of one year during 1991–1992 and for a period of 10 days in January 1992 at Upper Kargudi and in April 1992 at Bandipur, core zones of the Nilgiri Biosphere Reserve forests located in Tamil Nadu and Karnataka States, respectively, in south India. There is a marked diurnal variation in the concentration of surface ozone which clearly follows the diurnal variation of surface temperature. The monthly maximum concentration was observed during the summer season (March–May) and minimum during the monsoon season (June–September). The annual average concentration of ozone was 27 ppb and hourly values varied between 2 and 69 ppb at Pune. However, in the forest environment the 10-day average concentration was 15 ppb and hourly values varied between 5 and 31 ppb. The values of surface ozone at Pune and forest environment are below the U.S. EPA standard (113 ppb, maximum 1 h permissible concentration).