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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 peatfires 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 microg/m3 and 1.7 x 10(5) 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 SO4(2-), 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.

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Hydride generation to form arsine and in-line preconcentration of the arsine into an alkaline KMnO4 receiver followed by molybdenum blue (MB) colorimetric determination of the arsenate formed is proposed for the highly sensitive and separate measurement of total inorganic As and As(III). Reduction of As to AsH3 is carried out by NaBH4; when the reduction is carried out at pH 1, all the inorganic As is reduced to AsH3, and when carried out at pH 7, only As(III) is reduced. Reductions at the two different pH levels are carried out in two different arsine generators simultaneously using constant addition of NaBH4 with solenoid pumps. The AsH3 is collected by individual porous membrane diffusion scrubbers filled with a stationary solution of KMnO4, and the contents of the two scrubbers sequentially enter a flow analysis stream. MB is formed by merging with a ammonium molybdate-ascorbic acid reagent, passing through a heated reactor, and is then measured by a LED/photodiode-based absorbance detector. Robustness was confirmed for total As using three types of certified natural water samples. Speciation analysis data from well water samples analyzed by this method agree well with HPLC-ICPMS measurements in a different laboratory. The system has been successfully applied to field measurements of As(III) and As(V), where levels were significantly below 1 mug/L. For a 20-mL sample, the limits of detection (LODs) for this inexpensive instrument are 0.3 microg/L for both As(III) and total As. When an 80-mL sample is analyzed, LODs are 0.07 microg/L As(III) and 0.09 microg/L total As. The general approach should be applicable to many other analyte species of interest that can be isolated from the matrix by the formation of a suitable volatile compound that can be recaptured.

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Toxicological studies have implicated trace metals adsorbed onto airborne particles as possible contributors to respiratory and/or cardiovascular inflammation. In particular, the water-soluble metal content is considered to be a harmful component of airborne particulate matter. In this work, the trace metal characteristics of airborne particulate matter, PM2.5, collected in Singapore from February to March 2005 were investigated with specific reference to their bioavailability. PM2.5 mass concentrations varied between 20.9 mug/m3 and 46.3 microg/m3 with an average mass of 32.8 microg/m3. During the sampling period, there were several bushfires in Singapore that contributed to sporadic increases in the particulate air pollution, accompanied by an acrid smell and asthma-related allergies. The aerosol samples were subjected to analysis of trace elements for determining their total concentrations as well as their water soluble fractions. Our results showed an increase in concentration of several water-soluble trace metals during bushfires compared to their urban background levels in Singapore. In order to measure the human exposure to particulate air pollution, the daily respiratory uptake (DRU) of several trace metals was calculated and compared between haze and nonhaze periods. The DRU values were significantly higher for several metals, including Zn, Cu, and Fe, during bushfires. Electron paramagnetic resonance (EPR) measurements showed that the particulate samples collected during bush fires generate more toxic hydroxyl radicals (OH.) than those in the background air, due to the presence of more soluble iron ions.

Arsenic speciation analysis in marine samples was performed using ion chromatography (IC) with inductively coupled plasma mass spectrometry (ICP-MS) detection. The separation of eight arsenic species, viz. arsenite, monomethyl arsonic acid, dimethylarsinic acid, arsenate, arsenobetaine, tetramethylarsine oxide, arsenocholine and tetramethylarsonium ion was achieved on a Dionex AS4A (weaker anion exchange column) by using a nitric acid pH gradient eluent (pH 3.3 to 1.3). The entire separation was accomplished in 12 min. The detection limits for the eight arsenic species by IC-ICP-MS were in the range 0.03-1.6 µg l −1 , based on 3σ of the blank response (n = 6). The repeatability and day-to-day reproducibility were calculated to be less than 10% (residual standard deviation) for all eight species. The method was validated by analyzing a certified reference material (DORM-2, dogfish muscle) and then successfully applied to several marine samples, e.g. oyster, fish muscle, shrimp and marine algae. The low power microwave digestion was employed for the extraction of arsenic from seafood products.