Abderrahmane Touati

PCDD/F, PCB, HxCBz, PAH, and PM Emission Factors for Fireplace and Woodstove Combustion in the San Francisco Bay Region

Emissions from residential fireplace and woodstove appliances burning fuels available from the San Francisco Bay area were sampled for polychlorinated dibenzodioxins and dibenzofurans (PCDDs/Fs), polychlorinated biphenyls (PCBs), hexachlorobenzene (HxCBz), particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), oxygenated PAHs, and the monosaccharide levoglucosan. Emission factors for these pollutants were determined, the first known characterization of this extent. Common California natural firewoods and manufactured artificial logs were tested under operating conditions intended to reflect domestic use patterns in the Bay area, which are primarily episodic burning for aesthetic reasons. Emission factors were determined by fuel type, fuel weight, mass emission rates, and energy output, highlighting differences between fuel and combustion facility type. Average PCDD/F emissions factors ranged from 0.25 to 1.4 ng toxic equivalency (TEQ)/kg of wood burned for natural wood fuels and 2.4 ng TEQ/kg f...

PCDD/F emissions from forest fire simulations.

Abstract Polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran (PCDD/F) emissions from combustion of forest biomass were sampled to obtain an estimated emission factor for forest fires. An equal composition of live shoot and litter biomass from Oregon and North Carolina was burned in an enclosed monitored facility, and emissions were sampled with a modified ambient air sampling method. Seven tests resulted in an average PCDD/F toxic equivalency (TEQ) emission of 19 ng / kg burned, a value close to previous indirect estimates. Emissions from the Oregon biomass averaged 25 ng TEQ/kg burned (range: 14–47) and those from the North Carolina biomass averaged 15 ng TEQ/kg burned (range: 1–56). Source-specific distinctions in isomer patterns and homologue profiles, however, suggest that the type of biomass has a significant effect on the composition of the resulting PCDD/F emissions. The mass-specific emissions are about 20 times higher than the concentration of the extracted biomass, suggesting that PCDD/F emissions are not simply a result of vaporization of cuticle-bound PCDD/F but are formed predominantly during the biomass combustion.

PCDD/F, PBDD/F, and PBDE Emissions from Open Burning of a Residential Waste Dump

This work reports on the first known field study determining emission factors for polychlorinated and polybrominated dibenzodioxins/dibenzofurans (P[C/B]DDs/Fs) and polybrominated diphenyl ethers (PBDEs) from open burning of domestic waste. Two burning waste dump sites in Mexico were sampled using high-volume samplers mounted to a mobile sampling boom. Concurrent measurements of CO and CO(2) allowed determination of emission factors via the carbon balance method. PCDD/F emission factors averaged 823 ng toxic equivalency (TEQ)/kg C(burned) (N = 8, 68% relative standard deviation, RSD), a value at least five times higher than those from previous tests with domestic waste burned in barrels and approximately 2000 times higher than those from stacks of modern municipal waste combustors. These emission factors appear to be related to combustion quality, as conditions conducive to smoldering combustion, rather than flaming combustion, resulted in higher emission factors. Emissions of 40 PBDE congeners, likely originating from brominated flame retardants, averaged 724 mug/kg C(burned) (RSD = 96%) and had congener patterns similar to those of reported atmospheric sampling. Emissions of PBDDs/Fs were similar in magnitude to their chlorinated counterparts, averaging 470 ng TEQ/kg C(burned) (RSD = 105%), and may originate as reaction products of PBDE combustion or as thermally desorbed impurities from the PBDE flame retardant.

Effect of Moisture, Charge Size, and Chlorine Concentration on PCDD/F Emissions from Simulated Open Burning of Forest Biomass

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 dibenzofurans (PCDDs/Fs) as well as copollutants CO, PM, and total hydrocarbons. The experiments were performed in an enclosed chamber under conditions simulating open, prescribed burns of forest biomass. Burn progress was monitored through on line measurement of combustion gases and temperature while PCDD/F concentrations were determined by ambient sampling methods. PCDD/F toxic equivalency (TEQ) and total (tetra- to octa-CDD/F) emission factors were independent of charge size (1-10 kg) and moisture content (7-50%). However, the lower chlorinated, mono- to tri-CDD/F 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 100-fold increase of PCDD/F to about 90 ng TEQ/kg of carbon burned, C(b). These emission factors were linearly dependent on Cl concentration in the biomass. PCDD 2,3,7,8-Cl-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 Cl concentrations were mitigated by the presence of water, giving MCE = 0.868, promoting formation of mono- to tri-PCDD/F, and lowering the TEQ value. Open burn simulations were used to study PCDD/F formation in different combustion conditions providing a mathematical correlation between PCDD/F emissions and chlorine and moisture content in the fuel.

Emissions of unintentional persistent organic pollutants from open burning of municipal solid waste from developing countries

Open burning of waste is the most significant source of polychlorinated dibenzo-para-dioxins and dibenzofurans (PCDD/PCDF) in many national inventories prepared pursuant to the Stockholm Convention on Persistent Organic Pollutants. This is particularly true for developing countries. Emission factors for POPs such as PCDD/PCDF, dioxin-like polychlorinated biphenyls (dl-PCB) and penta- and hexachlorobenzenes (PeCBz/HCB) from open burning of municipal solid waste in China and Mexico are reported herein. Six different waste sources were studied varying from urban-industrial to semi-urban to rural. For PCDD/PCDF, the emission factors to air ranged from 3.0 to 650 ng TEQ kg(-1)waste and for dl-PCB from 0.092 to 54 ng TEQ kg(-1)waste. Emission factors for PeCBz (17-1200 ng kg(-1)waste) and HCB (24-1300 ng kg(-1)waste) spanned a wide but similar range. Within the datasets there is no indication of significant waste composition effect on emission factor with the exception of significantly higher Mexico rural samples.

Emission factors for PCDD/PCDF and dl-PCB from open burning of biomass

The Stockholm Convention on Persistent Organic Pollutants includes in its aims the minimisation of unintentional releases of polychlorinated dibenzo-dioxins and dibenzofurans (PCDD/PCDF) and dioxin like PCB (dl-PCB) to the environment. Development and implementation of policies to achieve this aim require accurate national inventories of releases of PCDD/PCDF/dl-PCB. To support this objective, the Conference of Parties established a process to review and update the UNEP Standardized Toolkit for Identification and Quantification of Dioxin and Furan Releases. An assessment of all emission inventories was that for many countries open burning of biomass and waste was identified as the major source of PCDD/PCDF releases. However, the experimental data underpinning the release estimates used were limited in number and, consequently, confidence in the accuracy of the emissions predictions was low. There has been significant progress in measurement technology since the last edition of the Toolkit in 2005. In this paper we reassess published emission factors for release of PCDD/PCDF and dl-PCB to land and air. In total, four types of biomass and 111 emission factors were assessed. It was found that there are no systematic differences in emission factors apparent between biomass types or fire classes. The data set is best described by a lognormal distribution. The geometric mean emission factors (EFs) for releases of PCDD/PCDF to air for the four biomass classes used in the Toolkit (sugarcane, cereal crops, forest and savannah/grass) are 1.6μg TEQ (t fuel)(-1), 0.49μg TEQ (t fuel)(-1), 1.0μg TEQ (t fuel)(-1) and 0.4μg TEQ (t fuel)(-1), respectively. Corresponding EFs for release of PCDD/PCDF to land are 3.0ng TEQ (kg ash)(-1), 1.1ng TEQ (kg ash)(-1), 1.1ng TEQ (kg ash)(-1) and 0.67ng TEQ (kg ash)(-1). There are now also sufficient published data available to evaluate EFs for dl-PCB release to air for sugarcane, forest and grass/savannah; these are 0.03μg TEQ (t fuel)(-1), 0.09μg TEQ (t fuel)(-1) and 0.01μg TEQ (t fuel)(-1), respectively. The average EF for dl-PCB release to land is 0.19ng TEQ (kg ash)(-1). Application of these EFs to national emissions of PCDD/PCDF for global estimates from open burning will lower previous estimates of PCDD/PCDF releases to air and to land by 85% and 90%, respectively. For some countries, the ranking of their major sources will be changed and open burning of biomass will become less significant than previously concluded.

Emissions of PCDD and PCDF from combustion of forest fuels and sugarcane : A comparison between field measurements and simulations in a laboratory burn facility

Release of PCDD and PCDF from biomass combustion such as forest and agricultural crop fires has been nominated as an important source for these chemicals despite minimal characterisation. Available emission factors that have been experimentally determined in laboratory and field experiments vary by several orders of magnitude from <0.5 μg TEQ (t fuel consumed)(-1) to >100 μg TEQ (t fuel consumed)(-1). The aim of this study was to evaluate the effect of experimental methods on the emission factor. A portable field sampler was used to measure PCDD/PCDF emissions from forest fires and the same fuel when burnt over a brick hearth to eliminate potential soil effects. A laboratory burn facility was used to sample emissions from the same fuels. There was very good agreement in emission factors to air (EF(Air)) for forest fuel (Duke Forest, NC) of 0.52 (range: 0.40-0.79), 0.59 (range: 0.18-1.2) and 0.75 (range: 0.27-1.2) μg TEQ(WHO2005) (t fuel consumed)(-1) for the in-field, over a brick hearth, and burn facility experiments, respectively. Similarly, experiments with sugarcane showed very good agreement with EF(Air) of 1.1 (range: 0.40-2.2), 1.5 (range: 0.84-2.2) and 1.7 (range: 0.34-4.4) μg TEQ (t fuel consumed)(-1) for in-field, over a brick hearth, open field and burn facility experiments respectively. Field sampling and laboratory simulations were in good agreement, and no significant changes in emissions of PCDD/PCDF could be attributed to fuel storage and transport to laboratory test facilities.

Emissions from small-scale burns of simulated deployed U.S. military waste.

U.S. military forces have historically relied on open burning as an expedient method of volume reduction and treatment of solid waste during the conflicts in Afghanistan and Iraq. This study is the first effort to characterize a broad range of pollutants and their emission factors during the burning of military waste and the effects that recycling efforts, namely removing plastics, might have on emissions. Piles of simulated military waste were constructed, burned, and emissions sampled at the U.S. Environmental Protection Agency (EPA) Open Burn Testing Facility (OBTF), Research Triangle Park, NC. Three tests contained polyethylene terephthalate (PET #1 or PET) plastic water bottles and four did not. Emission factors for polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), particulate matter (PM(10), PM(2.5)), polychlorinated and polybrominated dioxins/furans (PCDD/F and PBDD/F), and criteria pollutants were determined and are contained within. The average PCDD/F emission factors were 270 ng-toxic equivalency (TEQ) per kg carbon burned (ng-TEQ/kg Cb), ranging from 35 to 780 ng-TEQ/kg Cb. Limited testing suggests that targeted removal of plastic water bottles has no apparent effect on reducing pollutants and may even promote increased emissions.

Near-real-time combustion monitoring for PCDD/PCDF indicators by GC-REMPI-TOFMS.

The boiler exit flue gas of a municipal waste combustor was sampled to evaluate an online monitoring system for chlorobenzene congeners as indicators of polychlorinated dibenzodioxin and dibenzofuran (PCDD/PCDF) concentrations. Continuous measurements of chlorobenzene congeners using gas chromatography coupled to a resonance-enhanced multiphoton ionization - time-of-flight mass spectrometry (GC-REMPI-TOFMS) system were compared over 5-min periods with conventional sampling methods for PCDD/PCDF. Three pairs of values were taken every hour over a period of three days to characterize the combustors response to transient operating conditions (shutdowns and startups). Isolation of specific chlorobenzene congeners from other same-mass compounds was accomplished by using a GC column separator ahead of the REMPI-TOFMS. The 50-fold variation of PCDD/PCDF concentration was paralleled by similar changes in monitored compounds of 1,4-dichlorobenzene, 1,2,4-trichlorobenzene, 1,2,3-trichlorobenzene, and 1,2,4,5-tetrachlorobenzene. A correlation of R = 0.85 and 0.89 was established between 40 pairs of simultaneous 5-min GC-REMPI-TOFMS measurements of 1,2,4-trichlorobenzene and 5 min conventional sampling and analysis for the TEQ and Total measures of PCDD/PCDF, respectively. The GC-REMPI-TOFMS system can be used to provide frequent measures of correlative PCDD/PCDF concentration thereby allowing for an understanding of measures to minimize PCDD/PCDF formation and develop operational feedback to limit emissions.

Development of Size-Selective Sampling of Bacillus anthracis Surrogate Spores from Simulated Building Air Intake Mixtures for Analysis via Laser-Induced Breakdown Spectroscopy

Size-selective sampling of Bacillus anthracis surrogate spores from realistic, common aerosol mixtures was developed for analysis by laser-induced breakdown spectroscopy (LIBS). A two-stage impactor was found to be the preferential sampling technique for LIBS analysis because it was able to concentrate the spores in the mixtures while decreasing the collection of potentially interfering aerosols. Three common spore/aerosol scenarios were evaluated, diesel truck exhaust (to simulate a truck running outside of a building air intake), urban outdoor aerosol (to simulate common building air), and finally a protein aerosol (to simulate either an agent mixture (ricin/anthrax) or a contaminated anthrax sample). Two statistical methods, linear correlation and principal component analysis, were assessed for differentiation of surrogate spore spectra from other common aerosols. Criteria for determining percentages of false positives and false negatives via correlation analysis were evaluated. A single laser shot analysis of approximately 4 percent of the spores in a mixture of 0.75 m3 urban outdoor air doped with approximately 1.1 × 105 spores resulted in a 0.04 proportion of false negatives. For that same sample volume of urban air without spores, the proportion of false positives was 0.08.