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Effect of moisture, charge size, and chlorine concentration on PCDD/F emissions from simulated open burning of forest biomass
GRANDESSO, E., B. GULLETT, A. TOUATI, AND D. TABOR. Effect of moisture, charge size, and chlorine concentration on PCDD/F emissions from simulated open burning of forest biomass. ENVIRONMENTAL SCIENCE AND TECHNOLOGY. ACS Publications, Washington, DC, 45(9):3887-3894, (2011).
Loblolly pine (Pinus taeda) was combusted at different charge sizes, fuel moisture, and chlorine content to determine the effect on emissions of polychlorinated dibenzo-p-dioxins and polychlorinated diberizofurans (PCDDslFs) as well as co-pollutants CO, PM, and total hydrocarbons. The experiments were performed in an enclosed chamber under conditions simulating open, prescribed bums of forest biomass. Burn progress was monitored through on line measurement of combustion gasses and temperature while PCDDIF concentrations were determined by ambient sampling methods. PCDD/F toxic equivalency (TEQ) and Total (tetra- to octa-CDDIF) emission factors were independent of charge size (1 to 10 kg) and moisture content (7 to 50%). However, the lower chlorinated, mono- to tri-CDDIF compounds were increased by poor combustion conditions: combustion efficiency lower than 0.919 was generally found when the moisture content was higher than 30%. The increase of fuel matrix chlorine from 0.04% to 0.8% using a brine bath resulted in about a IOO-fold increase of PCDDIF to about 90 ng TEQlkg of carbon burned, Cb. These emission factors were linearly dependent on CI concentration in the biomass. PCDD 2,3,7,8-CI-substituted congeners and homologue patterns were also influenced by the addition of chlorine resulting in emissions with a higher abundance of the most toxic congeners (TeCDD and PeCDD). When both chlorine and moisture content were increased in the fuel, a simultaneous effect of the two parameters was observed. The increased TEQ values expected from higher CI concentrations were mitigated by the presence of water, giving MCE = 0.868, promoting formation of mono- to tri-PCDDIF, and lowering the TEQ value.