Measurements of Surface Ozone in Rural Site of India

It is known that the formation of surface ozone (O3) is chemically linked to the emissions of major precursor gases, nitrogen oxides (NOx) and volatile organic compounds (VOC). This chemical interdependence is highly complex and gives rise to non-linear and coupled pollutant formation processes. In the present study, an attempt has been made to examine the governing photochemical processes of O3 formation in a rural site. For this purpose, measurements of O3 and selected meteorological parameters have been made at Joharapur (19.3° N, 75.2° E, 474 m above sea level), a tropical rural site in India since March 2002. The annual average diurnal variation of O3 shows that maximum O3 concentration is 29.9 ± 5.7 ppbv at noon and minimum 7.0 ± 3.4 ppbv in the morning with 1 σ standard deviation. The monthly average high (low) O3 44.7 ± 10.8 ppbv (15.0 ± 3.2 ppbv) at noon in April (July), due to possible increase in precursor-gas concentrations by anthropogenic activity and the influence of meteorological parameters. Furthermore, O3 concentration has been observed as a function of season, which shows that the seasonal highest O3 concentration is 37.7 ± 8.7 ppbv at noon in premonsoon and lowest 17.4 ± 3.7 ppbv in monsoon season. The hourly averaged O3 concentration can exceed 70-80 ppbv in premonsoon and winter which is alarming attainment of air quality standard (80 ppbv) over the rural site in India.