Characterising temporal variability of PM2.5/PM10 ratio and its correlation with meteorological variables at a sub-urban site in the Taj City

Abstract

The problem of air pollution poses a major challenge in the city of Taj, Agra because of rapid urbanization and tourism. Research on PM2.5/PM10 ratio contributes to a deeper understanding of the air pollution scenario and promoting sustainable development. This study was carried out at a suburban site in Agra (Jan 2021-Dec, 2022). We analyzed PM2.5/PM10 ratios, and their correlation with Air Quality Index and meteorological factors using various statistical approaches in the OpenAir package in RStudio. The mean concentrations of PM2.5 and PM10 were 46 and 67 μg/m3, respectively. The PM2.5/PM10 ratio was 0.65, indicating fine particulate dominance. Diurnal, intra-annual, and weekly cycles of PM2.5, PM10, and PM2.5/PM10 ratios were examined. PM2.5/PM10 ratio increased with increasing AQI. Correlation analysis revealed, a strong positive correlation (r = 0.94) between PM10 and PM2.5 while the PM2.5/PM10 ratios showed negative association with wind speed (WS), and temperature, and positive association with relative humidity (RH). Higher RH led to higher PM2.5/PM10 ratios indicating worsening of PM2.5 pollution during winter and post-monsoon. Bivariate polar plots exhibited the lowest PM2.5/PM10 ratios in summer at high WS (>10 m/s) from the west, and the highest PM2.5/PM10 ratios in winter and post-monsoon at low WS (<10 m/s).