Seasonal Variation and Yearly Trend in PM2.5 Aerosols Concentration, Their Charracterization And Source Apportionment in Karachi (Pakistan)

Jawad Nasir (1), Asif Noor (1), BADAR GHAURI (1), Christian Khalil (2)

(1) Pakistan Space and Upper Atmosphere Research Commission (SUPARCO), (2) School of Risk and Safety Sciences, University of New South Wales, Australia

     Abstract Number: 595
     Last modified: May 14, 2010

Abstract
The World Bank Report 2006 demonstrated that high concentrations of suspended particulates in urban areas of Pakistan, adversely affect human health, provoking a wide range of respiratory diseases and heart ailments. With a view to examine the annual variations and composition of respirable suspended particulates, an intensive monitoring of PM2.5 over a period of four years (from January 2006 to December 2009).has been carried out at Karachi, the most populated and largest city of Pakistan. The trend shows an average increase of more than 30% in PM2.5 levels from 2006 (annual average 51.53 micro-gram per cubic meter) to 2009 (annual average 68.46 micro-gram per cubic meter) which are approximately 5 - 7 times greater than WHO guidelines for annual mean average (PM2.5 = 10 micro-gram per cubic meter). The highest 24 hour PM2.5 concentrations are noted in winter seasons as 148.7, 173.5, 181.3, 184.6 micro-gram per cubic meter) in consecutive years respectively from year 2006 to 2009 which are approximately 3 – 5 times greater than recommended level by Pakistan NEQS (40 micro-gram per cubic meter for 24-hour mean PM2.5). PM samplings were carried out twice a week by employing low volume air sampler with PTFE supported Zefluor filter papers as collection medium. The collected samples were subjected to chemical analysis for determination of elemental (As, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, Pd, Se, V and Zn) and ionic (SO4-2, NO3-, Cl- and NH4+) composition. The Positive Matrix Factorization (PMF) receptor model was used to apportion sources of the observed PM 2.5 aerosols. Major sources identified were secondary sulfates, secondary nitrates, motor vehicles emissions, biomass burning, industrial emissions and sea salts.