Real-time measurement and source apportionment of elements in Delhi's atmosphere

Pragati Rai; Markus Furger; Imad El Haddad; Varun Kumar; Liwei Wang; Atinderpal Singh; Kuldeep Dixit; Deepika Bhattu; Jean-Eudes Petit; Dilip Ganguly; Neeraj Rastogi; Urs Baltensperger; Sachchida Nand Tripathi; Jay G Slowik; André S H Prévôt

doi:10.1016/j.scitotenv.2020.140332

Real-time measurement and source apportionment of elements in Delhi's atmosphere

Sci Total Environ. 2020 Nov 10:742:140332. doi: 10.1016/j.scitotenv.2020.140332. Epub 2020 Jun 23.

Authors

Affiliations

¹ Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland.
² Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland. Electronic address: markus.furger@psi.ch.
³ Geosciences Division, Physical Research Laboratory, Ahmedabad 380009, India.
⁴ Department of Civil Engineering, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh 208016, India.
⁵ Laboratoire des Sciences du Climat et l'Environnement, CEA/Orme des Merisiers, 91191 Gif-sur-Yvette, France.
⁶ Centre for Atmospheric Sciences, Indian Institute of Technology Delhi, New Delhi 110016, India.
⁷ Department of Civil Engineering, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh 208016, India. Electronic address: snt@iitk.ac.in.
⁸ Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland. Electronic address: andre.prevot@psi.ch.

PMID: 33167294
DOI: 10.1016/j.scitotenv.2020.140332

Abstract

Delhi, the capital of India, suffers from heavy local emissions as well as regional transport of air pollutants, resulting in severe aerosol loadings. To determine the sources of these pollutants, we have quantified the mass concentrations of 26 elements in airborne particles, measured by an online X-ray fluorescence spectrometer with time resolution between 30 min and 1 h. Measurements of PM₁₀ and PM_2.5 (particulate matter <10 μm and < 2.5 μm) were conducted during two consecutive winters (2018 and 2019) in Delhi. On average, 26 elements from Al to Pb made up ~25% and ~19% of the total PM₁₀ mass (271 μg m^-3 and 300 μg m^-3) in 2018 and 2019, respectively. Nine different aerosol sources were identified during both winters using positive matrix factorization (PMF), including dust, non-exhaust, an S-rich factor, two solid fuel combustion (SFC) factors and four industrial/combustion factors related to plume events (Cr-Ni-Mn, Cu-Cd-Pb, Pb-Sn-Se and Cl-Br-Se). All factors were resolved in both size ranges (but varying relative concentrations), comprising the following contributions to the elemental PM₁₀ mass (in % average for 2018 and 2019): Cl-Br-Se (41.5%, 36.9%), dust (27.6%, 28.7%), non-exhaust (16.2%, 13.7%), S-rich (6.9%, 9.2%), SFC1 + SFC2 (4%, 7%), Pb-Sn-Se (2.3%, 1.66%), Cu-Cd-Pb (0.67%, 2.2%) and Cr-Ni-Mn (0.57%, 0.47%). Most of these sources had the highest relative contributions during late night (22:00 local time (LT)) and early morning hours (between 03:00 to 08:00 LT), which is consistent with enhanced emissions into a shallow boundary layer. Modelling of airmass source geography revealed that the Pb-Sn-Se, Cl-Br-Se and SFC2 factors prevailed for northwest winds (Pakistan, Punjab, Haryana and Delhi), while the Cu-Cd-Pb and S-rich factors originated from east (Nepal and Uttar Pradesh) and the Cr-Ni-Mn factor from northeast (Uttar Pradesh). In contrast, SFC1, dust and non-exhaust were not associated with any specific wind direction.

Keywords: Industries; Local and regional source locations; Non-exhaust; Source apportionment; Toxic metals; Urban air pollution.