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Characterization and Source Apportionment of Particulate Matter 2.5 m in Sumatra, Indonesia, during a Recent Peat Fire Episode Siao Wei See, Rajasekhar Balasubramanian,* Elisabeth Rianawati, Sathrugnan Karthikeyan, and David G. Streets Department of Chemical and Biomolecular Engineering, Block E5, #02-11, 4 Engineering Drive 4, and Division of Environmental Science and Engineering, Block EA, #07-23, 9 Engineering Drive 1, Faculty of Engineering, National University of Singapore, Singapore 117576, and Argonne National Laboratory, DIS/900, 9700 South Cass Avenue, Argonne, Illinois 60439 Received for review August 13, 2006 Revised manuscript received November 20, 2006 Accepted March 7, 2007 Abstract: An intensive field study was conducted in Sumatra, Indonesia, during a peat fire episode to investigate the physical and chemical characteristics of particulate emissions in peat smoke and to provide necessary data for source-receptor analyses. Ambient air sampling was carried out at three different sites located at varying distances from the peat fires to determine changes in mass and number concentrations of PM2.5 and its chemical composition (carbonaceous and nitrogenous materials, polycyclic aromatic hydrocarbons, water-soluble inorganic and organic ions, and total and water-soluble metals). The three sites represent a rural site directly affected by the local peat combustion, a semirural site, and an urban site situated downwind of the peat fires. The mass concentration of PM2.5 and the number concentration of airborne particles were as high as 1600 g/m3 and 1.7 × 105 cm-3, respectively, in the vicinity of peat fires. The major components of PM2.5 in peat smoke haze were carbonaceous particles, particularly organic carbon, NO3-, and SO42-, while the less abundant constituents included ions such as NH4+, NO2-, Na+, K+, organic acids, and metals such as Al, Fe, and Ti. Source apportionment by chemical mass balance receptor modeling indicates that peat smoke can travel long distances and significantly affect the air quality at locations downwind. ------------------------------------------------------------------------------------------------- Influence of the Oxidizing Species on the Reactivity of Iron-Based Bimetallic Reductants David M. Cwiertny, Stephen J. Bransfield, and A. Lynn Roberts* Department of Geography and Environmental Engineering and Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218 Received for review December 18, 2006 Revised manuscript received March 16, 2007 Accepted March 16, 2007 Abstract: Anticipating which pollutants are amenable to treatment by iron-based bimetallic reductants requires an understanding of the mechanism(s) driving pollutant reduction. Here, batch studies with six bimetals (Au/Fe, Co/Fe, Cu/Fe, Ni/Fe, Pd/Fe, and Pt/Fe) and four oxidants (alkyl polyhalides, vinyl polyhalides, alkynes, and water) explored the influence of the electron acceptor on reductant reactivity. Bimetals exhibited disparate reactivity toward some oxidant classes. For example, Pt/Fe enhanced rates of cis-dichloroethylene reduction, but it inhibited the reduction of several alkyl polyhalides. Moreover, the rate increase for vinyl polyhalide reduction by Ni/Fe (~100-fold) and Pd/Fe (~1000-fold) was far greater than that measured for alkyl polyhalides (~10-fold), and reactivity toward vinyl polyhalides exhibited a more pronounced dependence on Ni and Pd loadings than did reactivity toward alkyl polyhalides. These results suggest that the reactions of alkyl and vinyl polyhalides with iron-based bimetals involve different active reductants. Neither rates of alkyl nor vinyl polyhalide reduction correlated with rates of iron corrosion by water, contrary to expectations if galvanic corrosion was primarily responsible for organohalide reduction. Trends observed for the hydrogenation of 2-butyne did mirror the sequence we identified for 1,1,1-trichloroethane reduction, consistent with a role for atomic hydrogen as the principal electron donor in these two systems. |
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