Tropospheric ozone is a secondary
air pollutant that is not emitted, but is formed by
photochemical reactions between oxides of nitrogen (NOx), COmethane and other volatile organic compounds (VOCs) in the
presence of sunlight. The expansion of urban areas is continuously
contributing photochemical products of urban NOx and VOC
emissions to the rural areas. In developing countries, O3 concentrations
are also projected to increase in future (Van et al., 2009).
Ozone monitoring has shown increasing trend of annual mean
ambient concentrations ranging from 44.2 ppb during 2007 and
2008 (Sarkar and Agrawal, 2010) to 55.6 ppb during 2011 and 2012
(Singh et al., 2014) at Varanasi, situated in middle Indo-Gangetic
region of India. The AOT40 values reported for this region were
correlated with yield losses in agricultural crops (Rai and Agrawal,
2014; Mishra et al., 2013).