Metals are released in effluents of most of combustion processes and are under intensive regulations. To improve our knowledge of combustion process and their resulting emission of metal to the atmosphere, we have developed an approach allowing usto distinguish between gaseous and particulate state of the elements emitted. This study was conducted on the emission of volatile metallic species emitted from a coal combustion plant where low/medium volatile coal (high-grade ash) was burnt. The occurrence of volatile metal species emission was investigated by cryofocusing sampling procedure and detection using low-temperature packed-column gas chromatography coupled with inductively coupled plasma-mass spectrometry as multielement detector (LT-GC/ICP-MS). Samples were collected in the stack through the routine heated sampling line of the plant downstream from the electrostatic precipitator. The gaseous samples were trapped with a cryogenic device and analyzed by LT-GC/ICP-MS. During the combustion process, seven volatile metal species were detected: three for Se, one for Sn, two for Hg, and one for Cu. Thermodynamic calculations and experimental metal species spiking experiments suggest that the following volatile metal species are present in the flue gas during the combustion process: COSe, CSSe, CSe2, SeCl2, Hg0, HgCl2, CuO-CuSO4 or CuSO4 x H2O, and SnO2 or SnCl2. The quantification of volatile species was compared to results traditionally obtained by standardized impinger-based sampling and analysis techniques recommended for flue gas combustion characterization. Results showed that concentrations obtained with the standard impinger approach are at least 10 times higher than obtained with cryogenic sampling, suggesting the trapping microaerosols in the traditional methods. Total metal concentrations in particles are also reported and discussed.
Combustion processes are the most important source of metal in the atmosphere and need to be better understood to improve flue gas treatment and health impact studies. This combustion experiment was designed to study metal partitioning and metal speciation in the gaseous and particulate phases. A light fuel oil was enriched with 15 organometallic compounds of the following elements: Pb, Hg, As, Cu, Zn, Cd, Se, Sn, Mn, V, Tl, Ni, Co, Cr, and Sb. The resulting mixture was burnt in a pilot-scale fuel combustion boiler under controlled conditions. After filtration of the particles, the gaseous species were sampled in the stack through a heated sampling tube simultaneously by standardized washing bottles-based sampling techniques and cryogenically. The cryogenic samples were collected at -80 degrees C for further speciation analysis by LT/GC-ICPMS. Three species of selenium and two of mercury were evidenced as volatile species in the flue gas. Thermodynamic predictions and experiments suggest the following volatile metal species to be present in the flue gas: H2Se, CSSe, CSe2, SeCl2, Hg(0), and HgCl2. Quantification of volatile metal species in comparison between cryogenic techniques and the washing bottles-based sampling method is also discussed. Concerning metal partitioning, the results indicated that under these conditions, at least 60% (by weight) of the elements Pb, Sn, Cu, Co, Tl, Mn, V, Cr, Ni, Zn, Cd, and Sb mixed to the fuel were found in the particulate matter. For As and Se, 37 and 17%, respectively, were detected in the particles, and no particulate mercury was found. Direct metal speciation in particles was performed by XPS allowing the determination of the oxidation state of the following elements: Sb(V), Tl(III), Mn(IV), Cd(II), Zn(II), Cr(III), Ni(II), Co(II), V(V), and Cu(II). Water soluble species of inorganic Cr, As, and Se in particulate matter were determined by HPLC/ICP-MS and identified in the oxidation state Cr(III), As(V), and Se(IV).
A cryosampling system together with a low temperature GC-ICP-MS method have been developed for the determination of phosphine for industrial hygiene purposes. The effect of sampling temperature on the collection efficiency of PH 3 was investigated. Two trapping mechanisms were differentiated for temperature ranges from 2190 to 2160 uC and from 2110 to 235 uC. A cartridge filled with NaOH was used during the analytical desorption step to separate CO 2 from phosphine. Phosphine recovery was found to be better than 98% with peak area and retention times RSD values better than 4% and 2%, respectively. The use of a Nafion 1 drying membrane before cryogenic trapping induced losses of PH 3 of about 15%. Sample conservation in a cryocontainer at 2190 uC over a period of 15 days did not lead to significant losses of PH 3 . For field experiments, air samples were collected in the fumigation room of a tobacco factory after fumigation, and outside the fumigation room during fumigation, using both cryogenic sampling and standard filters impregnated with silver nitrate. The results showed that phosphine concentrations in the tobacco factory were below the limit values for occupational exposure to phosphine (VME (France) and TLV-TWA (USA)) and also below the detection limit of the silver impregnated filter-ICP-AES method. Cryogenic trapping in combination with GC-ICP-MS allowed us to determine phosphine concentrations. The concentrations in ambient air are estimated to be about 1 ng m 23 and the detected concentrations in the vicinity of the fumigation room during the fumigation process are lower than 10 ng m 23 . PH 3 in air reacts with HOx radicals and is removed by this mechanism with a half time of 5-28 hours, depending on the conditions. 1 The sunshine increases the OHx radicals concentration and may reduce the half-life to less than 5 hours. The following reaction of phosphine with OHx may occur:This reaction is dependant on PH 3 concentration and is very rapid, with a reaction rate constant at room temperature of about 1.5 6 10 211 cm 3 mol 21 s 21 . 9 The final product of the
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