Badar M. Ghauri

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.

Identification of pollution sources of anomalously enriched elements

Concentrations of trace chemical constituents were determined in size-fractionated and whole ambient air aerosol samples collected in Karachi, Pakistan, at four locations. The sampling sites were so chosen as to preferentially collect aerosols from sea, industrial areas, downtown and a steel mill. The aerosols from the industrial areas frequently showed unusually high Sb and Pb concentrations, especially in the fine fraction. The Pb/Sb ratio in such cases was

A multielement tracer technique for the determination of SO2 oxidation in clouds

18–25. It was concluded that these were derived from a storage-battery plant where Sb (4–5%) is alloyed with Pb in plates. Mn and Fe rich aerosols were detected in the vicinity of the steel mill, probably from fugitive emissions of raw material and not emission stacks. The SO42−/Se ratio indicated that the emissions from the steel mill chimneys are dispersed over a wide region.

Kinetic models of natural gas combustion in an internal combustion engine

A technique was developed in this laboratory which uses similarities in the physical and chemical properties of SO4 and Se aerosols to quantitatively resolve SO4 in cloud water derived from the gas and aqueous phase oxidation of SO2. We report here the extension of the technique to include As and Sb as tracers and present experimental data to verify assumptions in our earlier studies regarding the sampling of precloud aerosols. In situ SO4 production in clouds [(SO4in)] is given by [SO4in] = [(SO4/M) cw - α/(β,δ,τ) (SO4/M)aa] (M)cw where M represents Se, As, or Sb; α,β, δ and τ are the scavenging efficiencies of SO4, Se, As, and Sb aerosols, respectively; and cw and aa represent cloud water and ambient precloud aerosols. Field data from three cloud systems are presented, which show that δ/β = 0.92 ± 0.12 and τ/β; = 0.95 ± 0.13. Therefore within experimental uncertainties, the scavenging efficiencies of As and Sb are determined to be equal to that of Se. Results of in-cloud oxidation determined in three clouds using Se, As, and Sb are in excellent agreement. Regression analysis of SO4in by As and Se had a slope of 1.02 ± 0.05 (r=0.85). Similarly for Sb and Se the slope was 1.06 ± 0.05 (r=0.85).

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

In this study, combustion of methane was simulated using four kinetic models of methane in CHEMKIN 4.1.1 for 0-D closed internal combustion (IC) engine reactor. Two detailed (GRIMECH3.0 & UBC MECH2.0) and two reduced (One step & Four steps) models were examined for various IC engine designs. The detailed models (GRIMECH3.0, & UBC MECH2.0) and 4-step models successfully predicted the combustion while global model was unable to predict any combustion reaction. This study illustrated that the detailed model showed good concordances in the prediction of chamber pressure, temperature and major combustion species profiles. The detailed models also exhibited the capabilities to predict the pollutants formation in an IC engine while the reduced schemes showed failure in the prediction of pollutants emissions. Although, there are discrepancies among the profiles of four considered model, the detailed models (GRIMECH3.0 & UBC MECH2.0) produced the acceptable agreement in the species prediction and formation of pollutants.

Prediction and measurement of pollutant emissions in CNG fired internal combustion engine

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.

Development and testing of a detailed kinetic mechanism of natural gas combustion in internal combustion engine

Abstract In the present study, the detailed reaction mechanisms were developed and Chemkin 4.1.1 was implemented to predict the formation of pollutant species in compressed natural gas (CNG) fired internal combustion (IC) engine. The proposed mechanisms were developed by coupling the EXGAS (an automatic mechanism generation tool for alkane oxidation) mechanisms with the Leeds NO x mechanism (version 2.0). The simulation results of each proposed mechanism were validated by the experimental measurements for profiles of temperature, pressure and pollutant species (CO, NO x ). The rate of production analysis of each mechanism identified the important reactions in each mechanism which contributed to the formation of pollutant species. In spite of some discrepancies, the experimental measurements indicate that Mechanism-IV (consisting of 208 reactions and 78 species) showed closer agreement for each of the predicted profiles of temperature, pressure and pollutant species (CO, NO x ).

Characterization of carbonaceous aerosols in urban air

Abstract A detailed chemical mechanism to describe the combustion of natural gas in internal combustion (IC) engine has been developed, which is consisting of 233 reversible reactions and 79 species. This mechanism accounts for the oxidation of methane, ethane, propane and nitrogen. It has been tested using IC engine model of CHEMKIN 4.1.1 and experimental measurements. The performance of the proposed mechanism was evaluated at various equivalence ratios (ϕ = 0.6 to ϕ = 1.3), initial reactor conditions (T ini = 500 to 3500 °C; P ini = 1.0 to 10 atm) and engine speed (2000–7000 rpm). The proposed kinetic mechanism shows good concordances with GRI3.0 mechanism especially in the prediction of temperature, pressure and major product species (H 2 O, CO 2 ) profiles at stoichiometric conditions (ϕ = 1.0). The experimental results of measured cylinder pressure, species fractions were also in agreement with simulation results derived from the proposed kinetic mechanism. The proposed mechanism successfully predicts the formation of gaseous pollutants (CO, NO, NO 2 , NH 3 ) in the engine exhaust. Although there are some discrepancies among each simulation profile, the proposed detailed mechanism is good to represent the combustion of natural gas in IC engine.