Influence of seasonal variation on spatial distribution of PM_2.5 concentration using low-cost sensors

Fine particulate matter (PM_2.5) is one of the major airborne pollutants in urban environments and is associated with severe health impacts. In this study, a dense network of low-cost sensor (LCS) is used to cover large spatial area and detect ambient PM_2.5 concentration in Guwahati city. The measurements were conducted at multiple sites in different seasons between July 2022 and June 2023. Seasonal variability significantly influences regional meteorology, aerosol optical depth (AOD), and PM_2.5 concentration. The seasonal average PM_2.5 concentration was highest during winter (113.05 µg m ^-3), followed by post-monsoon (56.11 µg m^-3), then pre-monsoon (46.60 µg m^-3), and least for monsoon (32.36 µg m^-3) season. The elevated PM_2.5 concentrations may be attributed to environmental conditions (low ambient temperature, calm wind, and low planetary boundary layer height) that resulted in the least dispersion of PM_2.5. The concentration-weighted trajectory (CWT) analysis identifies the effect of regional (Indo-Gangetic Plain and northeast region) and transboundary (Bay of Bengal, Bangladesh, and northwest Asian countries) transported air masses on urban air quality. Post-monsoon and winter season has a high influence on long-range transported aerosols, whereas the monsoon and pre-monsoon seasons are affected by ocean and land air masses. Changes in surrounding activities and meteorology influence spatial distribution of PM_2.5 particles. Elevated PM_2.5 concentrations were recorded at in-city and outskirt sites because of the nearby activities (industry and traffic) and build-up area. In meteorology, wind significantly affects spatial dispersion of PM_2.5 concentration to the sites located in upwind and downwind directions.