Chemical characterization and source apportionment of PM10 and PM2.5 were carried
out for two different elevations (lower elevation (LE) similar to 5-10 m and higher
elevation (HE) similar to 30-45 m) at four different locations representing urban
background, city center, upwind, and downwind of the Delhi city during January 2017-March
2017. The 24-h average PM10 and PM2.5 concentrations were varied between 135.2-258.7
and 79.3-120.9 mu g/m(3), respectively. The average PM10 and PM2.5 concentrations
were found significantly higher at LE than HE. The PM samples were analyzed for ions,
elements and carbonaceous matter (EC/OC), and their concentrations (except S, V, As,
Ni, Sb, Sr, Ga, elements associated with industrial combustion activities, and NO3-,
attributed to high nitrate formation potential at HE) were observed higher in LE than
HE at all the study locations. The chemical mass balance model was applied to quantify
the source contributions to PM10 and PM2.5 mass at two different elevations. Model
identified vehicular emission (diesel, PM10 similar to 8.8-21.7% and PM2.5 similar
to 10.5-24.4% and gasoline, PM10 similar to 4.8-15.6% and PM2.5 similar to 6.7-14.8%),
industrial residual oil combustion (PM10 similar to 8.8-23.5% and PM2.5 similar to
3.2-10.4%), road dust (PM10 similar to 13.6-22.3% and PM2.5 similar to 8.8-17.8%),
soil dust (PM10 similar to 33.8-41.1% and PM2.5 similar to 5.8-8.3%), secondary nitrate
(PM10 similar to 6.1-16.2% and PM2.5 similar to 13.4-20.2%), secondary sulfate (PM10
similar to 7.1-12.3% and PM2.5 similar to 10.6-16.7%), and biomass burning (PM10 similar
to 6.8-21.8% and PM2.5 similar to 4.9-38.7%) as the main sources of PM10 and PM2.5
mass at both the elevations at all the study sites. The contribution of industrial
residual oil combustion, vehicular emission, and secondary nitrate to PM10 and PM2.5
mass was found relatively higher in HE than LE. Results also revealed that biomass
burning contributed significantly to PM pollution in the outskirts of Delhi than inside
the city. Further, potential source contribution function analysis revealed that there
may not be a long-range transport of PM emitted from biomass burning in the upwind
region of Delhi during the study period. Shifting to Indian BS VI vehicles and fuel,
switching to cleaner fuel in slum households, strict compliance on industries, and
regular vacuum cleaning of roads will reduce the severe air quality problem in Delhi.
