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

Abstract

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 (O₃) 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 PM_2.5) 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. O₃ 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 O₃ with CO, NO, NO₂ and BTEX suggested that the O₃ formation mechanism is driven by volatile organic compounds (VOCs) (mainly BTEX), CO and NO_x. On the coarser scale, however, seasonality and other factors have distorted the correlation. Random forest model with O₃ concentration as the response variable and NO₂, NO, SO₂, CO, BTEX, PM₁₀ and PM_2.5 as independent variables suggested that PM₁₀, NO, CO and solar radiation are highly important variables governing the O₃ 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.