AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Spatial and Temporal Variability in Chemical Composition of Ambient Fine Particulate Matter in the Megacity of Karachi, Pakistan
HAIDER KHWAJA, Lurie Kelly, Zafar Fatmi, David Carpenter, Daniel Malashock, Azhar Siddique, Kamran Khan, Mirza M. Hussain, Fida Khatib, Wadsworth Center, University at Albany
Abstract Number: 504 Working Group: Urban Aerosols
Abstract Air quality was assessed for Karachi, Pakistan using 24-hour fine particulate matter (size is 2.5 micro-meter) samples collected from two sites, Korangi (industrial/residential) and Tibet Center (commercial/residential). Spatial and temporal characteristics and sources of pollution were evaluated from August 2008 through August 2009 using samples analyzed for PM2.5, black carbon (BC), trace metals, and water-soluble ions. Enrichment factors were calculated, and a receptor model was used to identify anthropogenic and natural source contributions. The mass concentration of the sampled PM2.5 exceeded the WHO Guideline of 20 microgram/cubic meter ranging from 30 to 279 microgram/cubic meter. The average for Korangi (102 microgram/cubic meter) was greater than that for Tibet Center (77 microgram/cubic meter). PM2.5 concentrations were higher in the winter, suggesting increased burning and decreased air dispersion. Average BC concentration ranged from 0.04 to 28.7 microgram/cubic metre. Enrichment factors suggest abundant seasonal contributions of trace metals from anthropogenic activities. Concentrations of pollutants were higher at the Korangi site as compared to Tibet Center, indicative of emissions from industrial activities near the site. Chemical mass reconstruction exhibited that fine particulate matter in Karachi consisted of 35% crustal material, 13% secondary ions (SI), 7.6% sea spray, 4.9% BC, 2.7% trace metals, and 37% others (organic matter), on a yearly average basis. The PM2.5 data sets were analyzed using Positive Matrix Factorization (PMF) to identify possible sources and estimate their contributions to the fine particulate matter. Five and seven sources were identified of particulate matter viz., vehicular emissions, secondary aerosols, sea spray, industrial, diesel, crustal material, and re-suspension of dust. Major air pollution concerns for the megacity of Karachi were identified, highlighting the need for stringent laws on PM2.5 emission control to protect human health and the environment.