Temporal and Seasonal Variability of Fine and Coarse Particulate Matter in a Tropical Semi-Arid Region of South India

This study investigates the temporal and seasonal characteristics of particulate matter (PM 1 , PM 2.5 , and PM 10 ) over Kadapa (14.47° N, 78.82° E, 138 m asl), a tropical semi-arid region in South India. The measurements used in this work were conducted using an Optical Particle Counter (OPC 3016-IAQ) during March 2021–February 2022. Distinct seasonal variation was observed: PM 1 and PM 2.5 concentrations were elevated in winter, largely driven by stagnant atmospheric conditions and enhanced emissions, while PM 10 peaked in summer due to resuspension of crustal dust. Weekday concentrations exceeded weekend levels, with pronounced increase on Fridays, indicating stronger anthropogenic contributions. Meteorological parameters strongly modulated PM variability, showing negative correlations with temperature and wind speed, and positive correlations with relative humidity. Also, the atmospheric boundary layer height further modulated pollutant concentration resulting in the accumulation of particles. The analysis from trajectory models (PSCF and CWT) highlighted mixed contributions from continental and marine sources. The results revealed the seasonal shift of airmasses from the Bay of Bengal and the Arabian Sea during summer and monsoon, and inland/northern regions during the winter and post-monsoon seasons. Surprisingly, PM 2.5 levels frequently exceeded WHO guidelines, suggesting potential health risks, though direct health impacts were not assessed. The study is subject to limitations, including reliance on daytime measurements, lack of chemical composition data, and uncertainties in trajectory-based analyses. Overall, the findings provide new insights into the seasonal dynamics and source influences of PM concentrations in a tropical semi-arid environment. The study emphasizes the combined impact of meteorology, local emissions, and regional transport on air quality. The results also underline the need for multi-year, chemically resolved investigations to improve source attribution and inform effective strategies on the air quality management.