Adil R. Khan

Lead content of petrol and diesel and its assessment in an urban environment

Pakistan is one of the few countries in Asia thatcontinues to use only leaded-petrol as vehicular fuel. Theconcentration of Pb in its petrol reported in 1991 was thehighest (1.5 – 2.0 g Pb L-1) of all produced by the various Asiancountries and far exceeded the WHO’s guideline of 0.15 g Pb L-1. We have undertaken a study to trace and quantify this toxicelement in the environs of Karachi, Pakistan’s major metropolis,having more than 30% of the nation’s total number of vehicles.In this article we report the Pb contents of petrol and dieselcurrently manufactured and marketed in the city. Samples of`Regular’ petrol collected in 1999 was found to contain 0.363 gPb L-1 (range: 0.335 – 0.390 g Pb L-1), a factor of 5 lower than thatmarketed prior to 1991. Its concentration in diesel fuel was muchlower (0.017 g Pb L-1). Based on the available statistical data onthe type and volume of vehicular traffic, we assessed that thecurrent lead emission from vehicular traffic into the atmosphereis 391 metric tons a year, which is a factor of 2.7 lower thanthat estimated for 1989.

Composition of aerosols and cloud water at a remote mountain site (2.8 kms) in Pakistan

Major ion and trace metal concentrations were determined in aerosols and cloud water at a site in the Himalayan Mountains of Northern Pakistan. In spite of the fact that the site is well removed from significant urban/industrial pollution sources the SO2−4 concentrations in some of the samples were as high as those observed in North America. Concentrations of Se, Tl, Pb, Cl, Cd, Sb, Zn, and As in aerosols were highly enriched relative to average crustal abundances indicating significant anthropogenic contributions. Cloud water concentrations of major ions and trace elements are reported for 18 samples from six different clouds. The pH varied between 5.3 and 6.8 in spite of the fact that the SO2−4 concentration approached 300 μmol in some samples, values often observed in the northeastern US. Selenium was used as a tracer to determine in-cloud production of SO2−4 in these clouds and in three of the six clouds 40–60% of the observed SO2−4 came from in-cloud production.

Anatomy of an episode of high sulfate concentration at Whiteface Mountain, New York

Abstract Concentrations of seven metals and sulfate in aerosols collected at Whiteface Mountain, New York, were measured continuously in 6-h intervals for 2 weeks in June 1979. Thirteen consecutive samples showed high episodic concentrations of sulfate, Fe, Al and, to a lesser extent, Zn, Pb, K, Mg and Ca. The trajectories for the period of elevated [SO 2− 4 ] passed through the midwestern United States and entered New York State from the southwest. The trajectories for the time periods of low [SO 2− 4 ] before and after the episode entered New York from the north. This relationship between high concentrations and the surface-air trajectories suggests that in this particular episode SO 2− 4 and metals may have been transported from the Midwest. As the effective travel time ( T ) of this air mass, passing through a high SO 2 -emission area, increased, [SO 2− 4 ] increased, while the metal concentrations (particularly [Fe]) decreased. These observations suggest that in this episode Fe and SO 2− 4 were transported together. Analyses of other episodes are needed before any general conclusions can be drawn. This analysis could not have been performed with 24-h sample collection periods and therefore illustrates the advantages of relatively short collection times.

Ion Chromatographic Determination of Anions in Environmental Samples

Abstract The use of ion-exchange chromatography with an IonPac AS 14 column, 3.5 mM Na2CO3/1.0 mM NaHCO3 eluent and suppressed conductivity detection provides a simple, cost-effective, fast, accurate, and highly sensitive method for the determination of F−, Cl−, NO2 −, Br−, NO3 −, PO4 2−, SO4 2−, and C2O4 2− at low μ/L levels in environmental samples. Data on sensitivity, selectivity, accuracy, and % relative standard deviation are described. The method is suitable for many environmental applications including atmospheric aerosols (exposed on cellulose, glass fiber, and quartz filters), rainwater, cloud water, potable- and non-potable waters, and carbonated waters. Dominant components of the aerosol were SO4 2−, NO3 −, and Cl−. Rainwater, on the other hand, has relatively very low concentrations of these three species. The wide-spread concentration range for Cl− in variety of water samples and the high concentrations for SO4 2− in drinking water are striking. Determination of the anionic composition of ca...

Application of the SO42−/Se tracer technique to study SO2 oxidation in cloud and fog on a time scale of minutes

We have demonstrated the use of Se as a tracer to quantitatively determine in situ SO4(2-) production from SO2 oxidation in clouds and fogs. Until now, it has not been possible to study the kinetics of SO2 oxidation because the aerosol sampling interval for Se determination was limited to 2 h or longer. Here we report results of 5-min aerosol measurements carried out at Lahore, Pakistan, during January 9-11, 2001, using new methodology for Se analysis coupled with hydride generation and ICP-MS detection. These improvements will enable the tracer technique to determine in situ SO4(2-) production in clouds and fogs on a time scale of several minutes and possibly 1 min. The method may prove useful for kinetic studies of in-cloud SO2 oxidation and in the study of other phenomena such as atmospheric mixing, cloud drop lifetimes, and aerosol formation that occur on the time scale of a few minutes.

X-ray powder diffractometry of emissions from the cement industry

Abstract X-ray powder diffractometry has been found capable of identifying and distinguishing limestone and cement particles, the two important emissions of the cement industry. The limestone shows strong reflections principally at 1.87,1.91,2.09,2.28,2.49,3.03 and 3.83 A from its main constituent, calcite, whereas cement shows reflections at 1.76, 2.18, 2.60, 2.64, a doublet at 2.73–2.77 and 3.02 A from its main phases, the di-, and tri-calcium silicates. X-ray diffraction analysis of airborne particles collected on glass fibre filters in the vicinity of cement factories in Karachi, Pakistan and Ravena, New York State, revealed limestone but no cement particles. This observation was consistent with our earlier inference drawn from chemical and statistical methods for Karachis ambient aerosols. The method can complement the selective leaching technique suggested earlier by us for source identification. On the basis of model calculations, a methodology has been worked out that would make the present technique adaptable to plant conditions.