Source Apportionment of PM2.5 & PM10 of Delhi NCR for Identification of Major Sources
This study carried out source apportionment of PM2.5 and PM10 concentrations in Delhi-National capital region (NCR) using two modelling-based approaches. The first approach relied upon monitoring and chemical characterization of PM2.5 and PM10 samples. The chemically speciated samples along with source profiles were fed into the receptor model to derive source contributions. In the second approach, source-wise emission inventory, along with meteorological inputs and boundary conditions were fed into a dispersion model to simulate PM10 and PM2.5 concentrations. The modelled concentrations were compared with actual observations for validation. The validated model has been used to carry out source sensitivity to derive source contributions and future projections of PM2.5 and PM10 concentrations. Finally, various interventions have been tested which can reduce the pollutant concentrations in future years.
Independently derived source contributions from the two approaches (receptor and dispersion) for the year 2016 are compared to judge their mutual consistency. This will help the policy makers to take informed decisions and eventually the validated dispersion model can be used for future projection or intervention analysis. The results of the two approaches not only show consistency with each other but also with the previous study (IITK, 2015) in deriving source contributions. In comparison to the IITK (2015), this study has different monitoring locations and is based on different meteorological conditions prevailing in the year 2016.
A comprehensive exercise of air quality monitoring was carried out for a period of two seasons in one year at 20 representative locations (9 in Delhi City, 4 in Uttar Pradesh, 7 in Haryana) in the NCR including kerbside, industrial, commercial, residential, and reference sites, which has different land use pattern and sources of activity.
This study also estimated the contribution of various regions towards PM2.5 and PM10 concentrations in Delhi and NCR Towns. The average contribution of Delhi's own emissions in Delhi's PM2.5 concentrations was found to be 36% in winters and 26% in summers. However, there are variations across different places in the city.
The results of the two approaches are close for most sectors. It is to be noted that in the dispersion modelling approach, the industrial sector (which seems to be overestimated) includes biomass as an industrial fuel. Dust includes contributions from road dust re-suspension, construction activities, and trans-boundary international contributions. Based on the assessment of species, it may be concluded that in summers, trans-boundary contributions are mainly composed of dust. However in winters, there are also some transboundary contributions from sectors, such as biomass burning and industries also. Overall, the results of source apportionment seem to be consistent for most sectors in both the approaches. In the two seasons, the dispersion model shows contributions of transport sector as 17%-28%, in comparison to the receptor model estimations of 20%-30%. These findings are higher than the contributions of transport sector reported in IITK (2015) report, because in this study we included secondary particulates along with the primary contributions.