Investigating the Impact of VOC Sources during Different Seasons on the
Air Quality of a Metropolitan Region in India
Abstract
Volatile organic compounds (VOCs) play a crucial role in influencing the
air quality of the urban atmospheres, especially in nitrogen oxide (NOx)
dominated regions like India. Additionally, the associated direct health
risks necessitate the identification of VOC sources and their
contribution to the VOC budget of a region. This study presents the
seasonal variability of VOCs measured using a Proton Transfer Reaction
Quadrupole Mass Spectrometer (PTR-QMS) during the year 2019 over the
metropolitan Pune region. Also, the VOC sources have been identified
using the US EPA PMF 5.0 model for different seasons. Toluene (summer: 2
μg/mΛ3, monsoon: 1.11 μg/mΛ3, winter: 7 μg/mΛ3), o-Xylene (summer: 1.41
μg/mΛ3, monsoon: 1.24 μg/mΛ3, winter: 5.67 μg/mΛ3), Acetaldehyde
(summer: 2.80 μg/mΛ3, monsoon: 1.84 μg/mΛ3;, winter: 5.10 μg/mΛ3) and
Acetone (summer: 5.95 μg/mΛ3, monsoon: 2.58 μg/mΛ3, winter: 6.21 μg/mΛ3)
were found to be the prominent anthropogenic source-based emissions
apart from Methanol (summer: 8.68 μg/mΛ3, monsoon: 5.24 μg/mΛ3, winter:
7.72 μg/mΛ3) which mostly has a biogenic source. While most of the
identified sources (vehicular emissions, biomass burning, biogenic
emissions, photochemical secondary products) are common throughout the
year, their contribution to the total measured VOCs across seasons has
varied considerably (9-17%, 8-12%, 5-14%, 19-27% respectively). Of
the resolved factors, ozone formation potential (OFP) was found to be
highest for photochemical secondary products (26%) during all the
seasons, followed by vehicular emissions (23%) and background emissions
(17%). The sources identified in this work are in agreement with a
recent bottom to top emission inventory developed for the region which
shows vehicular emissions as a dominant VOC source. This work highlights
the role of meteorology in varying the VOCs concentration over the Pune
region and eventually the local air quality.