Source apportionment using UNMIX receptor model: A case study in Delhi
The UNMIX receptor model used for apportionment of significant source of ambient aerosol in Delhi during winter season. The sampling of PM1 was done for 4 months from December–2009 to March–2010 and collected sample were chemically analysed for 12 elements (Na, K, Mn, Ca, Cd, Cr, Cu, Ni, Zn, Pb, Fe, and Mg) and 4 ions (SO4-2, NO3-, Cl-, NH4+). The UNMIX identified three sources. The source profile –1 was influence by Ca and Mn and interpreted as crustal soil, source profile –2 composed of K and Na and interpreted as biomass burning and sources profile–3 was identified by model as secondary aerosol and significantly influenced by SO4-2, NO3- and NH4+. The results validated with enrichment factor analysis, K/Na analysis and factor analysis. The measured and predicted concentration of PM1 were showing good correlation (R2 = 0.77), indicating that the UNMIX model worked well. The NO3-, K, NH4+ SO4-2 and Ca showed high correlation with R2 value greater than 0.70, while Cl-, Na, and Mn showed moderate correlation with R2, varied between 0.52–0.67. The finding can be significant for policy maker and scientists in regional climate study.