Ambient and Episodic Levels of Metals in PM_(10) Aerosols and Their Source Apportionment in Central Delhi, India

摘要

The aim of this study was to assess the levels of metals in particulate matter measuring less than 10 μm (PM_(10)) aerosols in ambient air at a site in central Delhi. A total of seven metals were analyzed in PM_(10) aerosol samples during the postmonsoon period in 2009. The average levels of metals were estimated in the order K ＞ Zn ＞ Mg ＞ Fe ＞ Mn ＞ Cu ＞ Cd. The study also covered the metal accumulation due to fireworks on Diwali festival. A comparison of ambient levels of metal accumulation with the Diwali period revealed that the festival Diwali is a source of severe air pollution when the levels of metals increased by many folds as compared with normal ambient levels. Significant amounts of metals are emitted into the atmosphere by burning of crackers and sparkles on the Diwali day (DD). The contribution of K was the highest during all DDs with its maximum 88% emission on the main DD. Remarkable increase was noticed for K (9.4 times) and Mg (6.1 times) on the DD over the pre-Diwali normal day, whereas for the pre-DD an increase of 6.2 and 4 times was noticed, respectively. Source apportionment using principal-component analysis revealed that crustal, industrial, and vehicular sources mainly contributed the metals in air during normal period, whereas fireworks and vehicular sources were identified as main contributors of metals during the Diwali period.