Study of ground ozone and precursors along with particulate matter at residential sites in the vicinity of power plant

Emission source characterization and meteorological influence are the key aspects to gain insight into the ground ozone governing mechanisms. Receptor-based data analysis techniques help in comprehending local ozone fluctuations in the lack of accurate information on the emission characteristics. Through sophisticated data analysis, the current study offers insight into the key factors influencing the ozone changes in the vicinity of power plants. Ground ozone (O-3) and its precursor variables carbon monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO2), Sulphur dioxide (SO2), benzene, toluene, ethyl-benzene and xylene (BTEX) along with the particulate matter of size less than 10 and 2.5 micron (PM10 and PM2.5) and meteorological variables have been studied at a residential site near the coal-fired power plant in the two cities; Chandrapur and Nagpur during 2016-2019. O-3 is observed to be not correlated significantly (r<0.16 and <0.1 in Nagpur and Chandrapur, respectively) with any of its precursor variables in two cities. On a finer time scale, however, an association of O-3 with CO, NO, NO2 and BTEX suggested that the O-3 formation mechanism is driven by volatile organic compounds (VOCs) (mainly BTEX), CO and NOx. On the coarser scale, however, seasonality and other factors have distorted the correlation. Random forest model with O-3 concentration as the response variable and NO2, NO, SO2, CO, BTEX, PM10 and PM2.5 as independent variables suggested that PM10, NO, CO and solar radiation are highly important variables governing the O-3 dynamics in Chandrapur. In Nagpur, wind direction, relative humidity, temperature, toluene and NO2 are more important. Qualitative analysis to assess the contribution of emission sources suggested the influence of traffic emissions in Nagpur and the dominance of non-traffic related emissions, mainly power plant and mining activities in Chandrapur. The hazard quotient is observed to be >1 in both cities suggesting a health hazard to the residents living in the area.