Quantifying the contribution of distant regional and local sources to particulate matter PM loadings in north west India using a combination of statistical tools and low cost PM sensors

Abstract

Particulate matter (PM) emitted from natural and anthropogenic sources is ubiquitous in the atmosphere. It impacts the atmospheric composition, air quality, climate, human health, and the biosphere. Rising industrialization and urbanization in the Indo-Gangetic Plains (IGP), also referred to as India s food basket, have led to severe air quality deterioration. Several sites in this densely populated region frequently exceed the national ambient air quality standards (NAAQS) of PM 10 and PM 2.5 . The PM levels in IGP are modulated by a complex interplay of unique and diverse sources and varying meteorological conditions that transport the emissions from the source to the receptor. However, the lack of spatially and temporally robust PM measurements and inadequate understanding of the source apportionment limits the effective mitigation of PM pollution. This thesis attempts to apportion the PM over a regionally representative site in the IGP into distant, regional, and local sources using a combination of statistical techniques and low-cost PM sensors. The first part of the thesis quantifies the contribution of long-range transport to elevated PM levels and the number of exceedance events compared to the regional sources of PM present in the NW-IGP using long-term ground- based measurements and back-trajectory analysis. I find that long-range transport from the distant regions in the west (Arabia, Thar Desert, Middle East, and Afghanistan) leads to significant enhancements in the average coarse-mode PM mass loadings during all seasons. However, local sources (wind speed lt 1 m s and#8722;1 ) contributed significantly to the enhanced PM 2.5 and coarse-mode PM during the winter season. Regional sources in the NW-IGP were responsible for the exceedance of PM 10 and PM 2.5 NAAQS on more than 36% and 48% of the days in the study period. This study revealed that inefficient regional combustion sources (municipal waste burning, biomass burning) in the NW-IGP should be targeted for ensuring compliance with the existing air quality