Chemical composition and source attribution of PM2.5 and PM10 in Delhi-National Capital Region (NCR) of India: results from an extensive seasonal campaign

Abstract

Ambient particulate matter concentrations in Delhi and its peripheral towns has been a matter of serious concern in the last decade. Understanding the changing nature of the chemical composition of particulates, their spatial and seasonal variability can be utilized for identifying probable sources. This study presents an extensive dataset of the chemical composition of PM_2.5 and PM₁₀ collected using speciation samplers, from 19 locations representing different activities and spread across Delhi–NCR during summer and winter seasons in the year 2016–17. Identification of contributing sources using chemical ratios as source indicators is attempted. A distinct seasonal variability in both PM_2.5 and PM₁₀ was observed, with winter maxima and summer minima. The fine fraction i.e. PM_2.5 was dominated by organic matter (OM) with mean concentrations of 40.96±25.74?μg/m³ followed by Sulfate-Nitrate-Ammonium (SNA) ions (31.44±20.69?μg/m³) and Elemental Carbon (EC) (19.56±12.57?μg/m³); while the coarse fraction i.e. PM₁₀ was dominated by OM (73.03±40.55?μg/m³) and SNA (47.25±30.56?μg/m³) along with significant contributions from crustal materials (40.85±18.89?μg/m³). The chemical ratios suggested mixed sources of PM with major contributions from vehicular emissions, re-suspended and/or construction dust, and fossil fuel combustion along with intermittent contributions from biomass and open waste burning. This analysis provides useful insights into the sources and processes affecting the particulate formation and underlines the need to control primary emissions as well as secondary precursors for air quality improvements in the region. The data generated under this campaign can also serve as an essential input for further evaluation using receptor modeling.