Composition, sources, and health risk assessment of particulate matter at two different elevations in Delhi city

Abstract

The PM10 and PM2.5 source apportionment and health risk assessment were performed for two different elevations (lower elevation (LE) ∼5–10 m and higher elevation (HE) ∼30–45 m) at four different locations of Delhi city during January 2017–March 2017. The measured 24-h average PM10 and PM2.5 concentrations at different locations were found between 134.7 and 257.7 μg/m3 and 78.7–121.1 μg/m3, respectively. The 24-h average PM10 and PM2.5 concentrations at the study sites were exceeding the national (NAAQS) and WHO limits by more than 1.3 and 3 times, respectively. The PM mass was enriched with carbonaceous matter, ions, crustal and trace elements and their concentrations (except, Sr, Ni, S, As, V, Sb, Ga- the trace elements associated with coal and heavy oil combustion & NO3− - due to high nitrate formation ability at greater heights) were found higher in LE. The source apportionment study was performed with positive matrix factorisation (PMF). PMF analysis identified vehicular emission (PM10, 9.6–24.3% & PM2.5, 12.1–25.3%), secondary inorganics (PM10, 6.4–22.5% & PM2.5, 11–23%), crustal source (PM10, 9–52% & PM2.5, 3.8–10.7%), fuel oil combustion (PM10, 3–21% & PM2.5, 9–23%), biomass burning (PM10, 7.4–28.6% & PM2.5, 6–50.5%), and coal combustion (PM10, 13–17% & PM2.5, 14–19.1%) as the main sources of PM10 and PM2.5 at the study sites. A significant difference in source contribution between the elevations was observed for coal combustion, fuel oil combustion, biomass burning, and crustal sources. The contribution of vehicular emission and secondary inorganics estimates were broadly similar at both elevations. Coal and fuel oil combustion contribution was found relatively higher at HE. Further, health risk due to exposure to toxic heavy metals in PM2.5 was assessed. Non-carcinogenic and carcinogenic risks (averaged of four sites) for both children and adults were exceeding the acceptable limit by more than 1.13 times. Results also showed that the public residing at HE is more susceptible to have greater health risks than LE at Delhi city. Sources contribution to carcinogenic risk was assessed and the results indicated that coal combustion (41%) contribution was highest followed by crustal sources (22%), fuel oil combustion (17%), vehicular emission (12%), biomass burning (4%) and secondary inorganics (4%).