Ozone variability: Influence by its precursors and meteorological parameters- an investigation

Abstract

Surface observations on trace gases such as ozone (O3), oxides of nitrogen (August 2014–May 2017) and carbon monoxide (January 2016–May 2017) were used to investigate O3 chemistry. Study shows O3 concentration is high during winter with a mean value of 35.54 ± 7.16 ppbv and low concentration in monsoon with a mean value of 12.70 ± 3.55 ppbv. Oxides of nitrogen (NOx = NO + NO2) concentrations are high during pre-monsoon followed by winter, post-monsoon and monsoon. Mean carbon monoxide (CO) concentrations were observed to be 201.21 ± 36.90 ppbv, 222.61 ± 37.31 ppbv, 170.14 ± 14.34 ppbv, 249.59 ± 52.03 ppbv respectively during winter, pre monsoon, monsoon and post-monsoon. Study suggests that irrespective of seasonal changes, strong correlation coefficients (0.97–0.99) were observed between O3 and air temperature. Solar radiation showed an observable influence on surface O3 concentrations in the lower troposphere. The rate of change of O3 concentration during morning and evening hours at the study site were 3.6 ppbv/h and −3.9 ppbv/h respectively characterizing the site as sub-urban category. The mass concentrations of black carbon (BC) measurements (January–February 2016) were also used to understand its influence on CO and O3 concentrations. The BC showed a strong positive correlation (0.90) with CO whereas strong negative correlation (0.90) with O3. Study also indicates a strong influence of atmospheric boundary layer height on O3 and BC concentrations. Study revealed that emissions from crop residue burning during winter and forest fire during pre-monsoon have significant influence on enhancing CO concentrations at study site.