East versus West in the US: Chemical Characteristics of PM2.5 during the Winter of 1999

The chemical composition of PM_2.5 was investigated at four sites (Rubidoux, CA, Phoenix, AZ, Philadelphia, PA, and Research Triangle Park, NC) in January and February of 1999. Three samplers were used to determine both the overall mass and the chemical composition of the aerosol. Teflon filters were weighed for total mass. Ions were analyzed using ion chromatography. Elements were determined using X-ray fluorescence. Organic and elemental carbon were measured using a thermo-optical method. At all of the sites, reconstructed mass was observed to be greater than or equal to the measured mass. Good ionic balance was found for ammonium, nitrate, and sulfate at each of the sites. Overall, the chemical composition of the aerosol for each site was in good agreement with the expected composition based upon previous studies, with the exception of relatively high nitrate contribution to the total mass at Philadelphia. Good agreement was found between the predicted amount of sulfate by XRF analysis of sulfur and the sulfate measured by ion chromatography. As expected, sulfate was a more important contributor to the total mass at the East Coast sites. Nitrate contributed more to the total mass at the West Coast sites and was an important factor in the highest observed mass concentration at Rubidoux. Teflon filters appear to lose nitrate to a greater extent than heat-treated quartz fiber filters. Organic carbon was also found to be the largest part of the aerosol mass on minimum days for all sites and a significant portion of the mass on other days with 25-50% of the total mass at all of the sites. At three of the sites, organic carbon (OC) collected on denuded filters was less than that found on nondenuded samples, indicating an absorptive artifact on the quartz fiber filters. It was also found that the crustal component to PM_2.5 was highest at Phoenix. PM_2.5 was also found to contribute significantly to the PM₁₀ particle mass at all the sites.     

Fourier Transform Infrared and Ion-Chromatographic Sulfate Analysis of Ambient Air Samples

Fourier transform infrared (FTIR) spectrometry has been evaluated as a method for determining the sulfate concentration of ambient aerosol particulate samples. Samples were collected on Teflon filters. The filters were analyzed for sulfate by both FTIR and ion chromatography (IC). There is good agreement between sulfate analysis by IC and analysis of the FTIR transmission spectra of the air filters during the first 5 1/2 days of the Carbonaceous Species Methods Intercomparison Study in which the ambient sulfate concentrations were above the 5.8 μg/cm² lower limit of detection of the FTIR technique. A method to improve the FTIR lower limit of detection is discussed. The difficulties incurred during background subtraction of the infrared spectra are described.     

Composition and Size Distribution of Residential Wood Smoke Particles

Residential wood combustion emissions are an important source of organic and elemental carbon particulate matter in many urban and suburban areas. This research determined the organic and elemental carbon composition and size distribution of particulate emissions for hot- and cool-burning wood stoves and from conventional fireplaces. Sampling was done from smoke plumes which had been cooled and diluted by ambient air so that the particulate composition measured would be representative of smoke particles as they actually exist in the atmosphere. Organic and elemental carbon were determined by thermo-optical carbon analysis. Corrections were made for vapor organic carbon adsorption on quartz fiber filters during sampling. Particles emitted by hot-burning stoves were black, had a unimodal size distribution, and contained from 20% to 60% carbon (primarily elemental carbon) and high levels of trace elements (11% K, 1% S, 3% Cl). In contrast, particles from cool-burning stoves were tan, had a bimodal size distribution, and contained from 55% to 60% carbon (almost entirely organic carbon) and minute amounts (< 0.1%) of trace elements. The composition of particles emitted by fireplaces had compositions that were intermediate between those of hot- and cool-burning stoves, but tended to be more similar to cool burning stove emissions.     

Use of proton backscattering to determine the carbon and oxygen content in fine particle samples deposited on PTFE((CF2)n) membrane disk filters

Particulate carbon is routinely measured in the IMPROVE (interagency monitoring of protected visual environments) program by analysis of samples collected on quartz filters. The analysis is performed at Desert Research Institute using the thermal optical reflectance method. Measurements of Si, Al, Ca, Ti, and Fe by X-ray fluorescence at Crocker Nuclear Laboratory are used by IMPROVE to calculate a SOIL parameter by weighting these elements to account for the oxygen and minor elements that are not measured. It is desirable to have alternative methods to measure both carbon and oxygen for data validation purposes.We have tested a method to measure carbon and oxygen concentrations from air samples deposited on PTFE membrane filters using the backscattered proton spectrum. The measurements were performed with a 4.5 MeV proton beam from the cyclotron of the Crocker Nuclear Laboratory during routine IMPROVE measurements of hydrogen by proton elastic scattering analysis. A surface barrier detector at 155° below the plane of the beam was employed in a Cornell geometry setup to measure the proton spectrum. We will discuss a consistent method to estimate the carbon from the PTFE (CF₂)_n membrane substrate that must be subtracted from the measured carbon (filter plus deposit). This method is independent of the number and arrangement of the fibers and the unknown stretching of the substrate. The measured carbon at multiple IMPROVE sites using this new method is generally slightly higher than carbon measured using thermal optical reflectance. The sum of all elements, including the oxygen and carbon determined by proton backscattering, compares somewhat better to gravimetric mass than the same sum using carbon by TOR instead of backscattering.     

Estimating ambient particulate organic carbon concentrations and partitioning using thermal optical measurements and the volatility basis set

We introduce a new method to estimate the mass concentration of particulate organic carbon (POC) collected on quartz filters, demonstrating it using quartz-filter samples collected in greater Pittsburgh. This method combines thermal-optical organic carbon and elemental carbon (OC/EC) analysis and the volatility basis set (VBS) to quantify the mass concentration of semi-volatile POC on the filters. The dataset includes ambient samples collected at a number of sites in both summer and winter as well as samples from a highway tunnel. As a reference we use the two-filter bare-Quartz minus Quartz-Behind-Teflon (Q-QBT) approach to estimate the adsorbed gaseous fraction of organic carbon (OC), finding a substantial fraction in both the gas and particle phases under all conditions. In the new method we use OC fractions measured during different temperature stages of the OC/EC analysis for the single bare-quartz (BQ) filter in combination with partitioning theory to predict the volatility distributions of the measured OC, which we describe with the VBS. The effective volatility bins are consistent for data from both ambient samples and primary organic aerosol (POA)-enriched tunnel samples. Consequently, with the VBS model and total OC fractions measured over different heating stages, particulate OC can be determined by using the BQ filter alone. This method can thus be applied to all quartz filter-based OC/EC analyses to estimate the POC concentration without using backup filters.

© 2016 American Association for Aerosol Research     

Thermal/optical reflectance equivalent organic and elemental carbon determined from federal reference and equivalent method fine particulate matter samples using Fourier transform infrared spectrometry

A fine particulate matter (PM_2.5) monitoring network of filter-based federal reference methods and federal equivalent methods (FRM/FEMs) is used to assess local ambient air quality by comparison to National Ambient Air Quality Standards (NAAQS) at about 750 sites across the continental United States. Currently, FRM samplers utilize polytetrafluoroethylene (PTFE) filters to gravimetrically determine PM_2.5 mass concentrations. At most of these sites, sample composition is unavailable. In this study, we present the proof-of-principle estimation of the carbonaceous fraction of fine aerosols on FRM filters using a nondestructive Fourier transform infrared (FT-IR) method. Previously, a quantitative FT-IR method accurately determined thermal/optical reflectance equivalent organic and elemental carbon (a.k.a., FT-IR organic carbon [OC] and elemental carbon [EC]) on filters collected from the chemical speciation network (CSN). Given the similar configuration of FRM and CSN aerosol samplers, OC and EC were directly determined on FRM filters on a mass-per-filter-area basis using CSN calibrations developed from nine sites during 2013 that have collocated CSN and FRM samplers. FRM OC and EC predictions were found to be comparable to those of the CSN on most figures of merit (e.g., R²) when the type of PTFE filter used for aerosol collection was the same in both networks. Although prediction accuracy remained unaffected, FT-IR OC and EC determined on filters produced by a different manufacturer show marginally increased prediction errors suggesting that PTFE filter type influences extending CSN calibrations to FRM samples. Overall, these findings suggest that quantifying FT-IR OC and EC on FRM samples appears feasible.

© 2018 American Association for Aerosol Research     

Nondestructive Analysis of Total Nonvolatile Carbon by Forward Alpha Scattering Technique (FAST)

The oldest method of nuclear analysis, Rutherford scattering of alpha particles, is the basis of a technique we have developed that is capable of the quantitative nondestructive determination of carbon and all other elements lighter than sodium on an aerosol filter. Samples are collected on thin-stretched teflon filters, which are then placed in the 30-MeV alpha-particle beam of the Crocker Nuclear Laboratory's 193-cm cyclotron. Scattered alpha-particles are detected at the forward angles of 62 and 74 degrees, and the method has become known as FAST, for forward alpha scattering technique. The fluorine content of the air particles is assumed to be much less than the carbon content, and the filter blank carbon is subtracted from the known CF₂ ratio of teflon. Sensitivities for carbon are limited by the need to subtract the 70 μg/cm² of carbon in the filter, which can be done to ±5%, or ±3.5 μg/cm². This amounts to ±0.15 μg/m³ for the National Park Service aerosol samples. Since the FAST analysis is done in vacuum, only nonvolatile species are measured. This technique provides an alternative way to measure carbon without using artifact-prone quartz filters.     

Comparison of particle emissions from an engine operating on biodiesel and petroleum diesel

Biodiesel is an alternative fuel with growing usage in the transportation sector. To compare biodiesel and petroleum diesel effects on particle emissions, engine dynamometer tests were performed on a Euro II engine with three test fuels: petroleum diesel (D), biodiesel made from soy bean oil (BS) and biodiesel made from waste cooking oil (BW). PM_2.5 samples were collected on Teflon and quartz filters with a Model 130 High-Flow Impactor (MSP Corp). Organic (OC) and elemental (EC) carbon fractions of PM_2.5 were quantified by a thermal-optical reflectance analysis method and particle size distributions were measured with an electrical low pressure impactor (ELPI). In addition, the gaseous pollutants were measured by an AMA4000 (AVL Corp). The biodiesels were found to produce 19-37% less and 23-133% more PM_2.5 compared to the petroleum diesel at higher and lower engine loads respectively. On the basis of the carbon analysis results, the biodiesel application increased the PM_2.5 OC emissions by 12-190% and decreased the PM_2.5 EC emissions by 53-80%, depending on the fuel and engine operation parameters. Therefore OC/EC was increased by three to eight times with biodiesel application. The geometrical mean diameter of particles from biodiesels and petroleum diesel had consistent trends with load and speed transition. In all the conditions, there is a shift of the particles towards smaller geometric mean diameter for the biodiesel made from waste oil.     

Filter Material Effects on Particle Absorption Optical Properties

Absorption enhancement and shadowing effects were investigated for nigrosin-laden quartz (fibrous), Teflon (matted), and polycarbonate (membrane) filters in inert surroundings at different sample steady-state temperatures and particle mass loadings. Sample absorptivity was determined using a novel laser-heating technique, which is based on perturbing the sample steady-state temperature and monitoring the thermal response during decay back to steady state, along with a model for thermal energy conservation. In addition, transmissivity measurements were carried out to enable determination of the sample absorption coefficient. The results indicated that the isolated-nigrosin absorption coefficient decreased with steady-state temperature and increased with mass loading and filter pore size. Comparing the absorption coefficient for both the isolated nigrosin and nigrosin-laden filters, indicated that absorption enhancement was most significant for the Teflon filters and least significant for the polycarbonate filters. The effect became more significant as the pore size decreased, steady-state temperature increased, and particle mass loading decreased. The decrease in the isolated-nigrosin, mass-specific absorption cross-section with heavier sample loadings was attributed to shadowing effects.

Copyright 2014 American Association for Aerosol Research     

Determination of hydrogen content, gross heat of combustion, and net heat of combustion of diesel fuel using FTIR spectroscopy and multivariate calibration

The precise determination of the heat of combustion is of great importance for trading automotive diesel. The net heat of combustion (NHC) of fuel is related to the hydrogen elemental composition of fuel as obtained by elemental analysis. Heat of combustion expressed as gross heat of combustion (GHC) and net heat of combustion (NHC) have been predicted from data obtained by proximate analysis (density, ash, water and sulphur content) (ASTM D4868). GHC was obtained using bomb calorimetry (ASTM D240). The results of ASTM D4868 and ASTM D240 were found in good agreement. GHC and NHC fall within the relatively narrow range 45.24-46.08 and 41.91-43.27 MJ/kg, respectively. GHCs of tested diesel samples are, on average, about 7% greater than NHCs. The present paper also present a simple analytical method for determination of hydrogen content, GHC, and NHC of automotive diesel fuel using FTIR spectroscopy and partial-least squares calibration (PLS-1). PLS-1 had a high prediction power for prediction of hydrogen from FTIR spectra of diesel samples. The spectral ranges used in calibration were 400-670 and 2846-2970 cm⁻¹. On the other hand, classical least squares calibration (CLS) was found invalid for determination of hydrogen content in diesel. The results obtained by the proposed analytical method were almost to those obtained by ASTM D4868 and ASTM D240. PLS-1 method, offers a simple and reliable analytical method for quantification of hydrogen content in diesel samples without running expensive analysis like those carried out using carbon, hydrogen, and nitrogen (CHN) instruments.     

Thermal degradation of epoxy resin/carbon fiber composites: Influence of carbon fiber fraction on the fire reaction properties and on the gaseous species release

The thermal degradation of epoxy resin/carbon fiber composites has been performed in ISO 5660 standard cone calorimeter using a piloted ignition. Two kinds of composites that differ by their volume fractions in carbon fiber (56 and 59 vol.%) were tested in this study. The cone calorimeter irradiance level was increased up to 75 kW m^?2 to characterize the carbon fiber volume fraction influence on the composite thermal degradation. Thus, main flammability and combustibility parameters were determined and calculated such as mass loss, mass loss rate, ignition time, thermal response parameter, ignition temperature, thermal inertia, and heat of gasification. As a result, all the characteristic parameters for the thermal resistance of composites were decreased when the carbon fiber volume fraction increased. Moreover, the main gaseous products (such as NO, CO, CO₂, HCN, H₂O, and lightweight hydrocarbons) emitted as well as the oxygen consumption during the composite thermal decomposition were also quantified simultaneously with a portable gas analyzer and a Fourier transform infrared spectrometer. The main species emission yields calculated from the gas analysis results increased slightly when the carbon fiber volume fraction was increased in the initial sample. The epoxy composite was represented as a sooty material with a significant production of soot particles during the combustion process. Furthermore, heat release rate, total heat release, and effective heat of combustion were calculated by using the oxygen consumption calorimetry technique. The results obtained showed that a small increasing of composite carbon fiber amount induced a sharp decrease of heat release rate and total heat release. Copyright © 2014 John Wiley & Sons, Ltd.     

Characterization of Combustion Aerosol Produced by a Mini-CAST and Treated in a Catalytic Stripper

We characterized the properties of combustion aerosol produced at different operating conditions of a mini-CAST burner that was treated in a Catalytic Stripper (CS) operating at 300°C. The goal was to establish a methodology for the production of soot particles resembling those emitted from internal combustion engines. Thermo-optical analysis of samples collected on Quartz filters revealed that the particles contained semi-volatile material that survived the CS. The amount of semi-volatile species strongly depended on the operating conditions ranging from less than 10% to as high as 30% of the particle mass. The mini-CAST operating conditions were also found to have a strong effect on the effective particle density (ρ_e ). The ρ_e , for example, ranged from as low as 0.3 to 1.05 g/cm³ for mondisperse 80 nm particles, although the mass-mobility exponent remained relatively constant (2.1–2.25). These differences are indicative of differences in the primary particle diameter, which was estimated to range between 8.5 and 34 nm depending on the operating conditions. The different types of particles produced were also found to exhibit different affinities for butanol but also different light absorption per mass of elemental carbon which can, therefore, lead to inconsistencies in aerosol instrumentation calibrations (e.g., condensation and optical particle counters, photoacoustic sensors). The work highlights the importance of establishing a detailed and well-defined method in using the mini-CAST-CS approach for instrument calibration in ways mimicking various engine combustion sources.

Copyright 2013 American Association for Aerosol Research     

Near real-time measurement of carbonaceous aerosol using microplasma spectroscopy: Application to measurement of carbon nanomaterials

A sensitive, field-portable microplasma spectroscopy method has been developed for real-time measurement of carbon nanomaterials. The method involves microconcentration of aerosol on a microelectrode tip for subsequent analysis for atomic carbon using spark emission spectroscopy (SES). The spark-induced microplasma was characterized by measuring the excitation temperature (15,000–35,000 K), electron density (1.0 × 10¹⁷–2.2 × 10¹⁷ cm^?3), and spectral responses as functions of time and interelectrode distance. The system was calibrated and detection limits were determined for total atomic carbon (TAC) using a carbon emission line at 247.856 nm (C I) for various carbonaceous materials including sucrose, EDTA, caffeine, sodium carbonate, carbon black, and carbon nanotubes. The limit of detection for total atomic carbon was 1.61 ng, equivalent to 238 ng m^?3 when sampling at 1.5 L min^?1 for 5 min. To improve the selectivity for carbon nanomaterials, which mainly consist of elemental carbon (EC), the cathode was heated to 300°C to reduce the contribution of organic carbon to the total atomic carbon. Measurements of carbon nanotube aerosol at elevated electrode temperature showed improved selectivity to elemental carbon and compared well with the measurements from the thermal optical method (NIOSH Method 5040). The study shows the SES method to be an excellent candidate for development of low-cost, hand-portable, real-time instrument for measurement of carbonaceous aerosols and nanomaterials.     

Potassium titanate whiskers on the walls of cordierite honeycomb ceramics for soot catalytic combustion

In this paper, potassium titanate whiskers was prepared via the Molten salt synthesis on the surface of cordierite ceramics for the regeneration of diesel particulate filters (DPFs). SEM, EDS, XRD, FT-IR, TG-DSC and TPO were carried out to characterize the morphology, microstructure, growth mechanism and catalytic performance of the samples. Potassium titanate whiskers with diameter (100–500 nm) and length (about 3 μm) is tightly combined with the cordierite ceramic substrate. The catalyst performance investigation demonstrates that potassium titanate whiskers decrease the soot combustion temperature apparently. The soot combustion process was studied by thermal analysis tests, and the activation energy of the combustion reaction can be calculated using Freeman-Carroll method. The carbon oxidation activation energy is 14.009 kcal/mol, and the activation energy for the catalytic reaction with potassium titanate whiskers is 6.287 kcal/mol, it can be illustrated that potassium titanate whiskers/cordierite catalyst possess excellence performance for carbon catalytic combustion. The coarseness of the interface increased because potassium titanate whiskers grew on the cordierite substrate, and the trapping ability could improve. This unique microstructure has potential application in the DPF field.     

Impact of organic compounds on the concentrations of liquid water in ambient PM2.5

A field study was undertaken during the summer of 2000 to assess the impact of the presence of organic compounds on the liquid water concentrations of PM_2.5 samples. The selected site, located in Research Triangle Park, North Carolina, was in a semi-rural environment with expected impacts from both biogenic and anthropogenic emissions. Eight samples, collected on Teflon filters over 48-h periods, were analyzed for their liquid water concentrations by using a beta gauge to measure the change in PM_2.5 mass on the filter as a function of relative humidity in a humidity-controlled environmental chamber. The filter samples were also analyzed for mass, elemental and organic carbon, and anionic concentrations. For six of the eight samples, the measured liquid water concentrations exceeded those predicted from the presence of the inorganic constituents. A relationship between the excess liquid water and the measured organic carbon mass was found, although the standard deviations associated with the measurements were large. Through modeling studies it was determined that, on average, about 80% of the liquid water in the PM_2.5 could be accounted for by inorganic ions present, with the remaining 20% associated with organic compounds. The liquid water data were consistent with the presence of aqueous solutions supersaturated with respect to the inorganic ions in the aerosol.     

Aerosol and Carbon Monoxide Emissions from Low-Temperature Combustion in a Sawdust Packed-Bed Stove

Low-temperature combustion in biomass-burning stoves used for cooking results in poor thermal efficiency and high emissions. A sawdust packed-bed stove has been shown to give more stable combustion at higher temperatures than woodstoves. The study examines pollutant emissions from this stove and their dependence on stove dimensions, specifically the vertical port radius and the stove-pot spacing. Emission rates of particulate matter (PM)—along with size resolution—and of carbon monoxide (CO) were measured during steady-state combustion. The stove power increased with increased spacing and vertical port radius. However, the air-flow rate, combustion temperature, and air-fuel ratio showed complex variations with stove dimensions from the described coupling among the pyrolysis, combustion, induced air flow, and mixing. Emission rates of PM (0.21–0.36 gh^?1 and CO (3–8 gh^?1 and were a factor of ten lower than those previously measured from woodstoves. Emission rates of CO decreased, while PM increased, with increasing combustion temperature. Aerosol size distributions were unimodal with mass median aerodynamic diameters (MMAD) of 0.24–0.40 𝛍 a factor of two smaller than from woodstoves. Cool combustion at 534–625°C gave lower PM emission rates but particles of larger MMAD, while hot combustion at 625–741°C gave higher PM emission rates with smaller particle MMAD. The OC/EC ratio obtained for cool combustion was higher (1.20) than that for hot combustion (0.96). Greater elemental carbon formation was seen at the higher temperatures. PM and CO emission rates followed opposite trends with combustion temperature and stove configuration, resulting in no single configuration at which both CO and PM emissions were minimized. However, its superior thermal efficiency and significantly lower emissions than wood stoves should motivate further study of this device to optimize thermal and emissions performance.     

Synthesis and Characterization of Oligo-azomethine by Thermal Condensation Using New Type of Monomers

Summary The synthesis and characterization of a variety of aromatic oligo-azomethine, by thermal polymerization of news monomer catalyzed by concentrated HCl, is reported. The new oligo-azomethine has been characterized using Uv-visible, infrared, ¹H-NMR and ¹³C-NMR spectroscopy. Other techniques such as elemental analysis and thermo-gravimetric analysis are also presented. The oligomeric material was synthesized by condensation between the ester group and the amine group. Surprisingly the oligomeric material retains the OCH₂CH₃ groups and it becomes bound to the C=N groups. The new type of monomers (aminophenyl ester) allow, at the first time, to introduce substituent covalent bonds to carbon atom of imine groups.     

Thermal Separation of Soot Carbon

We present here a simple and versatile variant of the thermal analysis of soot carbon, and a discussion on the encountered analytical artifacts. The method is based on a two-step combustion procedure; the removal of the organic material that does not absorb visible light is optimized during a precombustion step at 340°C during 2 hours under a pure oxygen flow, and the remaining carbon is then determined by coulometric titration of the CO₂ evolved from the combustion of the samples. These analytical conditions minimize the crossover between the different components of the aerosol, but better to a clear-cut division between organics and soot carbon, the quantitative evaluation of their thermal evolution is obtained. Artifacts have been tested thoroughly with various standards and replicates of ambient air samples collected. The method gives reliable soot carbon determination at the microgram level in samples from a wide variety of environments. Combined H / C atomic ratio measurements and investigations of the problems associated with the thermal determination of soot carbon permit gaining some insight on the nature of carbonaceous aerosols. They reinforce the indication that soot carbon is not composed primarily of elemental carbon. Also, it is suggested that highly polymerized natural organic aerosols though different in nature could behave thermally and optically like soot.     

Particulate Carbon Speciation by MnO2 Oxidation

A selective thermal oxidation method was developed for the speciation of carbonaceous aerosols collected on filters into organic carbon (OC) and elemental carbon (EC). The technique is based on studying the thermal oxidation of microcrystalline graphite by MnO₂as well as various organic compounds. The procedure uses a modified Dohrmann DC-52 carbon analyzer with a flame ionization detector to detect the CO₂resulting from the oxidation as methane after catalytic conversion. The results led to the selection of 525 °C as the optimal temperature for the oxidation of OC while leaving EC intact. After the organic oxidation, the sample is heated at 850° C, at which EC is oxidized rapidly and completely by MnO₂. Carbonates that may be present in either the particles or the filter medium are removed by acidification and heating to ～ 120°C prior to performing the organic and EC measurements. Analysis of split ambient particulate samples in which the OC levels had been reduced by solvent extraction produced EC results statistically the same as the original untreated samples. These results suggest that the speciation is not sensitive to the level of organics in the sample. During the Carbonaceous Species Methods Comparison Study (CSMCS) in which the participants analyzed 20 blind samples, with four being triplicates, this technique yielded results in good agreement with the average results of the participants, with coefficients of variation (CV) derived from the triplicate analysis being 2.1%, 2.6%, and 8.1%, respectively, for total, organic, and elemental carbon.     

Behavior of mercury release during thermal decomposition of coals

The mercury release behavior during thermal decomposition of three Chinese coals with different types was studied under nitrogen, carbon dioxide and air at temperatures of 800, 900, 1,000 and 1,100 °C. The thermal treatment experiments were carried out in a quartz tube reactor. Results showed that the release ratio of total mercury during thermal decomposition of coals increases with the increasing temperature. The order of the amount of mercury released under the three atmospheres is nitrogen<carbon dioxide<air for all three coals during thermal decomposition. This indicates that air and carbon dioxide can promote the mercury release due to their reactivity with coal. However, the order of amount of elemental mercury released under the three atmospheres is nitrogen>carbon dioxide>air for all three coals. The release behavior of the total mercury under air is independent of the coal type. Under the other two atmospheres the release behavior is distinguished by the coal type. This work was presented at the 7 ^th China-Korea Workshop on Clean Energy Technology held at Taiyuan, Shanxi, China, June 26–28, 2008.