Concentrations of EC, OC, Water Soluble Metals and Ions in PM10 collected in Lahore, Pakistan
Lahore, the second largest city of Pakistan with a population of over 8 million, houses dispersed small industrial units, in addition to designated industrial estates. The number of motor vehicles has nearly doubled to about 1.5 million during the last six years, about half of which are inefficient 2-stroke engine 2- and 3-wheelers. Currently there are only partial ambient standards for SO2 and NO2 but sparse air quality data indicate very high levels of particulate pollution.
PM10 samples were collected on pre-baked 8”x10” quartz filters using high volume sampler March/April 2006, which were analyzed for organic and elemental carbon using a thermo-optical analyzer, water soluble metals by ICP-MS and ions by ion chromatography.
PM10 averaged 360.8 µg/m3 with a range of 158.0 µg/m3 to 732.8 µg/m3 and standard deviation of 130.4 µg/m3. EC, OC, and OM averaged 16.2 µg/m3 (7.4 to 36.7), 57.5 µg/m3 (18.8 to 177.3) and 103.5 µg/m3 (33.8 to 319.1), respectively. Chloride, nitrate and sulfate averaged 8.3, 6.3, and 9.4 µg/m3, whereas sodium, potassium, and ammonium averaged 1.3, 2.7, and 2.1 µg/m3 respectively. Of the water soluble metals, concentrations of Ca, Mg, Pb, and Zn were especially high averaging 3589 ng/m3 (1029 to 7515), 270 ng/m3 (61 to 457), 429 ng/m3 (2.2 to 2580) and 5548 ng/m3 (189 to 10077), respectively. Eight samples, collected during an apparent episode, showing higher levels of PM10 were also analyzed for Hg; particulate mercury ranged from 408 to 4000 pg/m3 with an average of 1784 pg/m3.