Air quality in different urban hotspots in a metropolitan city in India and the environmental implication

This research study investigates hourly data on concentrations of five major air pollutants such as particulate matter (PM₁₀, PM_2.5) and gaseous pollutants (SO₂, NO₂, CO) measured during 2022 at four hotspot sites (industrial site, traffic site, commercial site, harbour, and one residential site) in Chennai, India. The analysis encompasses temporal variations spanning annual, seasonal, and diurnal variations in the pollutants. Notably, PM₁₀ and CO emerge as the predominant pollutants, with the highest concentrations at industrial and traffic sites (PM₁₀: 67.64 ± 40.77 µg/m³, CO: 1.41 ± 0.84 mg/m³; traffic site: PM₁₀: 58.67 ± 20.05 µg/m³, CO: 0.99 ± 0.57 mg/m³). Seasonal dynamics reveal prominent winter spikes in particulate matter (PM₁₀, PM_2.5) and carbon monoxide (CO) concentrations, while nitrogen dioxide (NO₂) and sulphur dioxide (SO₂) levels peak during the summer season, particularly in the harbour area. The proximity to roadways exerts a discernible influence on diurnal patterns, with traffic sites showcasing broader rush hour peaks compared to sharper spikes observed at other sites. Furthermore, distinct bimodal patterns are evident for PM₁₀ and PM_2.5 concentrations in residential and harbour areas. A common lognormal distribution pattern is identified across the studied sites, suggesting consistent air quality trends despite contrasting locations. The conditional probability function (CPF) is used in conjunction with local meteorological conditions for identifying key pollution sources in each location. The implementation of polar plots emphasizes industries as principal local sources of pollution, at industrial sites significantly contributing to PM₁₀, SO₂, and NO₂ concentrations under specific wind conditions. The main objective of the present study is to facilitate a good understanding of pollutant dynamics, pollution sources, and their intricate interplay with meteorological factors, thereby contributing to the formulation and implementation of effective air pollution control and mitigation strategies.