Badar Ghauri

Characterization and source apportionment of ambient air particulate matter (PM2.5) in Karachi.

Concentrations and source apportionment of PM(2.5) monitored at an urban residential site in Karachi Metropolitan, Pakistan have been reported in this paper. PM(2.5) aerosol samples were collected on alternative days (three times per week) for 24-hrs duration on Zefluor(TM) filter papers using Thermo-Electron Corporation Reference Ambient Air Sampler (RAAS). A total of 402 samples were collected from January 2006 to January 2008. According to results high PM(2.5) loads were observed in post monsoon months that is about 2 times than those observed in the summer and monsoon seasons in the yearlong measurements. The collected samples were analyzed using ICP-MS for trace metal concentration. Source apportionment was performed on PM samples using Positive Matrix Factorization (PMF) model. The results derived from PMF model indicated five (05) major contributors to PM(2.5) in Karachi which were: soil/road dust, industrial emissions, vehicular emissions, sea salt originated from Arabian Sea and secondary aerosols.

The use of chemical and statistical methods to identify sources of selected elements in ambient air aerosols in Karachi, Pakistan

Abstract Concentrations of 23 elements plus NO 3 − , SO 4 2− and Cl − were determined for samples collected continuously every 3 or 6 h during 22–27 July, 1985 at a suburban site in Karachi, Pakistan. Concentrations of lithophilic elements and several anthropogenic elements were ~ 80 % higher during daytime than at night. These elevated levels were attributed to daytime increases in wind velocity and anthropogenic activity. Factor analysis showed that ~ 50% of the variance was associated with soil, and ~ 14 % each with oceanic Na and Cl − , anthropogenic Sb and Pb, and Zn, Se and SO 4 2− . A cement (limestone/dolomite) factor was not separated even though Ca and Mg concentrations were unusually high and a cement factory was located nearby. This led to an investigation of a chemical approach to determine the sources. Concentrations of Na, Mg and Ca were determined in water-extracts of the samples. Assuming soluble Na (~ 92 % of total) to be sea derived, marine components of Mg, SO 4 2− , Ca and Br were determined. Solubility considerations were then used to reveal the cement source and apportion the aerosol sources. On the average, approximately 48 % of the total aerosol mass could be accounted for by the ‘cement’ and ‘soil’ components; about 12 % by the ‘sea salt’, about 3% by the ‘fossil fuel’ SO 4 2− (as (NH 4 ) 2 SO 4 ); about 1 % by the NO 3 − (as NH 4 NO 3 ); the remaining 36 % of the aerosol mass was unassigned.

On the widespread winter fog in northeastern Pakistan and India

During the last two winters widespread fog frequently occurred in northeastern India and Pakistan, in a region extending over 1500 km. A particularly severe fog episode lasted from mid-December, 1998 to early January, 1999. The fog caused extensive economic damage and disruptions in transport. We determined concentrations of SO42−, NO3−, and selected trace elements at Lahore, Pakistan during and after the fog event by collecting aerosols on Whatman 41 filters every 12 h. SO42− concentrations of up to 100 µg/m³ were observed during fog. The SO42−/Se ratios and trace element data suggest a distant source of SO42− aerosols, hundreds of kms away. Lahore was downwind of coal-burning in India during the fog. The high concentrations of SO42− observed suggest a more extensive investigation of the chemistry and transport processes in this region is necessary to delineate emission sources and develop control strategies as there are serious likely effects on human health and economy in a region populated by hundreds of millions of people, and on global climate change through direct and indirect forcing.

Particulate matter (PM2.5) concentration and source apportionment in lahore

The work reported in this paper was carried out to study the trends of PM2.5 (particles with an aerodynamic diameter of 2.5 µm or less) concentrations and source apportionment of PM2.5 monitored at an urban residential site in Lahore, Pakistan. PM2.5 aerosol samples were collected for 2 days in a week at 12 h interval in a day, both in dry and wet seasons, on ZefluorTM filter papers using Thermo-Electron Corporation Reference Ambient Air Sampler (RAAS). Total 310 samples were collected during the period under study, i.e., from November 2005 to December 2007. High PM2.5 loads were observed in winter, which were approximately 4 times greater than those observed in the summer, spring, fall and monsoon seasons in the yearlong measurements. Source apportionment was performed on short duration analysis results of November 2005 to March 2006 using Positive Matrix Factorization (PMF) model. The results derived from PMF model indicated that the major contributors to PM2.5 in Lahore are: soil/road dust, industrial emissions, vehicular emissions and secondary aerosols. It is, therefore, concluded that in addition to local vehicular and industrial emissions, the city is also affected from trans-boundary air pollutants particularly due to secondary aerosols (especially SO42-) during winter which increase PM2.5 concentrations manifold when relatively less mixing height exists. The sulfate particles also facilitate in haze/fog formation during calm highly humid conditions, thus reduce visibility and increase the incidents of respiratory diseases encountered in the city every year.

An assessment of air quality in Karachi, Pakistan.

An atmospheric pollution survey was carried out at 13 sites in Karachi, Pakistan, simultaneously from 0600 h to 2100 h for 15 consecutive days in May 1990 which also included meteorological measurements. The monitoring sites were included along the prevailing wind patterns in Karachi. Carbon monoxide levels in the ambient air were found to reach 9–10 ppm along the busy urban streets whereas CO2 level exceeded 370 ppm in these areas. Our survey indicates that NO2 levels were exceeding U.S. ambient air quality standards. Maxmum NO2 concentrations were observed (0.3–0.5 ppm) during the daytime from 0600 h to 2100 h. The surface ozone maximum around noon at the inland sites reached the levels of 40 ppb and 50 ppb respectively compared to upwind coastal Sites 1 level of 25 ppb. The Pb concentrations were approximately 3- to 7-fold higher than average, which corresponded well to urban air. Fossil fuel SO4 (excess) and NO3 were apportionally based on the assumption that these two anions were present as (NH4)2SO4, and NH4NO3 in the aerosols. In the eastern part of the city atmospheric sulphate (SO4) shows the combustion of coal as its source from the vicinity and downwind of a steel manufacturing plant.

Effect of moisture on the radon exhalation rate from soil, sand and brick samples collected from NWFP and FATA, Pakistan

A series of experiments were carried out to study the effect of the moisture content on the radon exhalation rate from soil, sand and brick samples that were collected from the North West Frontier Province and Federally Administered Tribal Areas of Pakistan, using CR-39-based radon dosimeters. After processing, samples were prepared by adding 15, 30 and 45% moisture contents (by weight) and were placed in plastic containers. The dosimeters were installed in it at heights of 25 cm above the surface of the samples. These containers were then hermetically sealed and the dosimeters were exposed to radon for 60 to 65 days. After exposure, CR-39 detectors were etched in 25% NaOH at 80 degrees C for 16 h, and track densities were counted. From the measured track densities, exhalation rate was determined using two different approaches. Maximum average radon exhalation rates of 385 +/- 86, 393 +/- 31 and 362 +/- 36 mBq m(-2) h(-1) were observed at 30% moisture content from soil, sand and brick samples, respectively. A slight decrease in exhalation rate was observed in all samples at moisture content of 45%. According to the t-test, change in the exhalation rate as a function of humidity is significant at 95% confidence level.

Air quality in the Karachi metropolitan area

Abstract Information about air quality in Third World cities is sparse, but air pollution problems are believed to be serious and increasing. The authors describe recent efforts by the Pakistan Space and Upper Atmosphere Commission (SUPARCO) to identify major pollutants, including the particulate content of ambient air; aerosols; and the content of gases such as ozone, nitrogen oxides, sulphur dioxide, and carbon monoxide.

Assessment of fine particulate matter (PM2.5) in metropolitan Karachi through satellite and ground–based measurements

Recent advances in remote sensing have provided new avenues for measuring, monitoring, and understanding processes that lead to atmospheric pollution. Space-based measurements in combination with ground-based information provide the complete spatial and temporal variation, as well as regional and global distribution of air pollutants. The present study involves integration of satellite and ground-based measurements and back trajectory analysis concerning the transport of pollutants from different sources. Satellite-derived aerosol optical depth (AOD) represents integrated atmospheric columnar loading of aerosols and can be used as a substitute to assess surface particulate matter air quality, especially where surface measurements are not available. This study is based on investigation of seasonal and spatial variation of aerosol concentration over Karachi, Pakistan using satellite-based AOD data from moderate resolution imaging spectroradiometer on board Terra/Aqua Satellites, ground-based data of two sun-photometers (NASAs AERONET) and other in situ measurements using DustTrak Particulate Monitor at Karachi (24.87° N, 67.03° E), Pakistan.