Analysis of Ozone Photochemistry over Southern Tropical Megacity, Bengaluru, India

Abstract

Rapid infrastructure development, increased population, shift in land use practices and higher vehicular emissions have all influenced Ozone (O3) production through its precursor gases in southern megacity, Bengaluru, India. We have investigated the photochemistry using hourly measurements of O3 and associated precursor gases conducted in Bengaluru during January to December 2019. The rate of formation of O3 is analyzed for Bengaluru for the first time using a photochemical model involving NOx cycle. On the diurnal scale, O3 showed a midday peak (1200–1500 IST), while its precursors showed a bimodal trend with peaks at 0900 IST and 2100 IST. The photolytic rate constants for jNO2 and jnormalO3 were derived from the tropospheric ultraviolet and visible (TUV) radiation model. Using the photolytic rate constants for jNO2 and jnormalO3 under the triad NO‐NO2‐O3, photostationary state (PSS), Leighton ratio (Ф) and its deviations from unity were estimated over Bengaluru. Positive anomalies (Φ > 1) were obtained, and the computed Φ was utilized to determine the total mixing ratios of the peroxy radical (PO2). The seasonal variation in jO3 revealed that in the presence of intense solar radiation and NOx, VOCs, CO and NMVOCs in the mixing layer, O3 forms photochemically over the surface.

Spatial and Temporal Variability of PM_2.5, PM₁₀ and BC Aerosols over Tropical Megacity Bengaluru, India

“…Its population has seen substantial growth of 13.2 % over the last decade [15]. A detailed description of the BMSCE site and urbanization of Bengaluru is presented by Shivkumar et al [16], Dhanya et al [17], and Gopi et al [18]. Urbanization is the key factor that plays an important role in the increase in the levels of PM and BC [19,20].…”