Identification of Potential Sources Affecting Fine Particulate Matter Concentration in Delhi, India

Abstract

The seasonal air transport pathways and the potential sources contributing to air pollution in Delhi for the period March 2015 to February 2016 have been identified with the help of PM2.5 data (particulate matter with diameter less than 2.5 μm), potential source contribution function (PSCF), cluster analysis and concentration weighted trajectory (CWT) method. The local sources are identified with the help of conditional probability function (CPF). The presence of re-circulating air masses has shown that the major contributors to air pollution in winter seasons are the local sources and the neighboring states of Haryana and Punjab. Northwesterly flows can be observed throughout the year and are highest in the winter season and comparatively lower in the monsoon season. PSCF values greater than 0.7 and CWT values greater than 110 μgm−3 are observed within the state in the winter season. Haryana and some parts of Uttar Pradesh also have higher PSCF values. The frequency of occurrence of long distance pathways is less in all the seasons in Delhi. The influence of the dust pathways from the Thar Desert areas can be seen in the monsoon season. Slower moving northwesterly and southwesterly flows are associated with high concentration values and indicate high pollution along the pathways. Higher CPF values occur in the northeastern direction. Therefore, the industrial sites, traffic congestion and emission from vehicles in the roads connecting Delhi and Uttar Pradesh have high influence in the rise in pollution levels.