Daytime Ozone Variation in Surface Air in a Subtropical Mangrove Estuary at Manakudy, South India

Surface ozone (SOZ) can be very harmful, if it exceeds the threshold limit. It can accumulate over sea and return to the land along with the breeze. Rural and vegetation rich areas often record elevated levels of surface ozone, due to the variations in Volatile Organic Compound (VOC) levels as well as wind velocity and direction. Similarly, methane is also an important greenhouse gas, which plays a vital role in atmospheric budget. The current study analyzes ozone and methane levels, measured during daytime in a mangrove estuary near Manakudy (8.0911 N, 77.477 E), Kanyakumari, South India for a period of ten months, from March 2014 to December 2014. SOZ shows an imprecise diurnal pattern with an early morning peak, whereas methane records an apparent diurnality. The maximum value of SOZ is around 50 ppb, with Summer months possessing high levels of SOZ, followed by Southwest monsoon (SWM) and Northeast monsoon (NEM). High levels of methane are found in SWM followed by NEM with the lowest concentration occurring in Summer. The correlation between SOZ and methane is found to be r = -0.257, p<0.001. The positive correlation of SOZ with temperature and wind speed strongly suggests the role of such surface meteorology in SOZ production and transport.