Seasonal distribution and deposition patterns of size-segregated particulate matter in human respiratory system in Central Delhi, India

Abstract

Seasonal patterns and potential exposure of size-segregated particulate matter (PM) were studied in central Delhi from January 2021 to December 2022. A total of 79 samples were collected using an eight-stage Andersen cascade impactor. The samples were categorized as submicron (PM_{< 0.43–1.1}), fine (PM_1.1–2.1), and coarse (PM_2.1- > 9) fractions of PM. During 2021, average mass concentrations of submicron, fine, and coarse PM were 67.2 ± 10.7, 33.6 ± 5.7 and 124.1 ± 9.1 µg/m³ respectively. During 2022, the corresponding average mass concentrations were 55.1 ± 7.5, 25.8 ± 3.6 and 117.2 ± 8.9 µg/m³ respectively. The submicron and fine particles were more prevalent during the post-monsoon and winter seasons, while coarse particles were more pronounced during summer. The lognormal mass-size distribution displayed a bimodal pattern during the winter and the post-monsoon seasons of 2021 and 2022. Conversely, summer and monsoon seasons exhibited unimodal distributions. The inhalation dose was calculated for all seasons, found in the order post-monsoon > winter > summer > monsoon. Total, regional, and lobar depositions of size-segregated PM in respiratory airways of various age groups were also quantified using the multiple-path particle dosimetry model. Among different age groups, the deposited concentrations ranged from 35–51% for inhaled submicron particles, 57–68% for fine particles, and 89–96% for coarse particles, respectively. The deposited mass in respiratory airways was maximum for coarse particles in summer, while maximum in winter for submicron and fine particles in all age groups. Concentration weighted trajectory analysis for various size ranges in different seasons highlighted the influence of local, regional, and long-range transport of pollutants at the receptor site.