Particulate Phase Mercury Research Articles

Development and characterization of an annular denuder methodology for the measurement of divalent inorganic reactive gaseous mercury in ambient air.

Atmospheric mercury is predominantly present in the gaseous elemental form (Hg0). However, anthropogenic emissions (e.g., incineration, fossil fuel combustion) emit and natural processes create particulate-phase mercury(Hg(p)) and divalent reactive gas-phase mercury (RGM). RGM species (e.g., HgCl2, HgBr2) are water-soluble and have much shorter residence times in the atmosphere than Hg0 due to their higher removal rates through wet and dry deposition mechanisms. Manual and automated annular denuder methodologies, to provide high-resolution (1-2 h) ambient RGM measurements, were developed and evaluated. Following collection of RGM onto KCl-coated quartz annular denuders, RGM was thermally decomposed and quantified as Hg0. Laboratory and field evaluations of the denuders found the RGM collection efficiency to be >94% and mean collocated precision to be <15%. Method detection limits for sampling durations ranging from 1 to 12 h were 6.2-0.5 pg m(-3), respectively. As part of this research, the authors observed that methods to measure Hg(p) had a significant positive artifact when RGM coexists with Hg(p). This artifact was eliminated if a KCl-coated annular denuder preceded the filter. This new atmospheric mercury speciation methodology has dramatically enhanced our ability to investigate the mechanisms of transformation and deposition of mercury in the atmosphere.

Magnification of atmospheric mercury deposition to polar regions in springtime: The link to tropospheric ozone depletion chemistry

Mercury—in the chemical/physical forms present in the biosphere—is a persistent, toxic, bioaccumulative pollutant that is dispersed throughout the environment on a global scale, mainly via the atmosphere. It is among the “heavy metals” for which the natural biogeochemical cycle has been perturbed by a wide range of human activities, including fossil‐fuel combustion and waste incineration. Results of our recent measurements of gaseous elemental mercury (GEM), as well as total particulate‐phase mercury (TPM) concentrations in Arctic air, ‘total Hg’ concentrations in Arctic snow, and tropospheric BrO concentrations from an earth‐orbiting‐satellite platform are presented and discussed. Findings of our research, and the conclusions derived therefrom, are important for environmental protection as well as the health and well‐being of aboriginal people in Arctic circumpolar nations.

Determination of Mercury in Mainstream Cigarette Smoke by Conventional and Amalgamation Cold Vapor Atomic Absorption Spectrometry

Abstract A method for differentiation of gas- and particulate-phase mercury in mainstream cigarette smoke was developed using electrostatic precipitation (EP) as the trap for the particulate phase and impingers containing acidic potassium permanganate solution as the trap for the gas-phase portion. The mercury collected from the gas phase was analyzed by conventional cold vapor atomic absorption spectrometry (CVAAS) and the particulate phase was analyzed by gold amalgamation CVAAS. Cigarettes were smoked under two smoking regimes, FTC (35-mL puff volume, 2 s puff duration and one puff every 60 s) and an alternative (45-mL puff volume, 2 s puff duration, one puff every 30 s and 50% of any ventilation holes blocked) currently recommended by the Massachusetts Department of Health. For the 1R4F reference cigarette smoked under the FTC smoking regime, the mercury found in the particulate phase was less than 0.2 ng/cig, compared with 4.9 ng/cig in the gas phase. By changing smoking parameters, the mercury concentration in mainstream smoke was found to change proportional to the delivery of cigarette smoke condensate (CSC) for the same type of cigarette. However, the mercury level for different types of cigarettes smoked under the same smoking parameters had no linear relationship with CSC delivery. Spiked recovery was 98% AA± 8% for gas-phase mercury and 97% AA± 2% for the particulate phase. These results indicate that the analytical method developed is suitable for the determination of mercury in mainstream smoke. For routine analytical work in a smoking laboratory, only the gas phase needs to be analyzed for determination of mercury in mainstream smoke because the amount of mercury in the particulate phase is negligible.

International field intercomparison measurements of atmospheric mercury species at Mace Head, Ireland

Eleven laboratories from North America and Europe met at Mace Head, Ireland for the period 11–15 September 1995 for the first international field intercomparison of measurement techniques for atmospheric mercury species in ambient air and precipitation at a marine background location. Different manual methods for the sampling and analysis of total gaseous mercury (TGM) on gold and silver traps were compared with each other and with new automated analyzers. Additionally, particulate-phase mercury (Hg part) in ambient air, total mercury, reactive mercury and methylmercury in precipitation were analyzed by some of the participating laboratories. Whereas measured concentrations of TGM and of total mercury in precipitation show good agreement between the participating laboratories, results for airborne particulate-phase mercury show much higher differences. Two laboratories measured inorganic oxidized gaseous mercury species (IOGM), and obtained levels in the low picogram m -3 range.

Comparison of conventional filtration and a denuder-based methodology for sampling of particulate-phase mercury in ambient air

This paper compares the results of total atmospheric particulate-phase mercury determinations using samples collected by two methods. The conventional filtration method (FM) collects airborne particulate matter first, whereas the denuder-based method (DM) removes gaseous-phase mercury prior to particulate matter collection. In each case, particulate-phase mercury (PM) is collected on a quartz fiber disc held in a miniaturized device and is analyzed using a pyrolysis/gold amalgamation/thermal desorption/cold vapor atomic fluorescence spectrometry (CVAFS) technique. The results show that the concentrations of PM determined using the samples collected by DM are higher than those determined using the samples collected by FM. Evidence presented shows that the higher results are due to mercury-bearing gold particles flaking off from the gold-coated denuder surfaces in the denuder-based sampling system.

99/02242 A fundamental study of mercury partitioning in coal fired power plant flue gas: Senior, C. L. et al. Proc., Annu. Meet. Air Waste Manage. Assoc., [computer optical disk], 1997, 90, WP72B08/1–WP72B08/16

Data suggest that coal-fired power plants are a significant source of atmospheric mercury. Predicting the emissions of mercury cannot be done without a fundamental understanding of the chemical reactions of mercury in flue gas. A research program has been designed to address the major mechanisms for speciation and partitioning, leading to a model that enables the utility industry to predict and, therefore, minimize the emission of regulated trace elements, particularly mercury. Results from preliminary experiments and modeling are presented and discussed. Although combustion produces elemental mercury, coals typically contain sufficient chlorine to oxidize a portion of the elemental mercury to HgCl{sub 2} at temperatures in the range of 750--900 K. At temperatures below approximately 600 K, gaseous mercury species interact with flyash and a significant portion of the gaseous mercury is converted to particulate phase mercury. The authors speculate that residual carbon from coal combustion could also act as an oxidation catalyst in the temperature range of 400--600 K. At temperatures below 400 K, adsorption on carbon-containing ash occurs. Comparison of the results of equilibrium calculations with measurements of speciation of gaseous mercury compounds in flue gas indicate that equilibrium is not attained for mercury by the time the fluemore » gas reaches the inlet to the air pollution control device. The data suggest that the equilibrium is frozen at temperatures in the range of 800--900 K. A better understanding of the gas-to-particle conversion is also needed, particularly the relationship between char or carbon properties and oxidation and/or adsorption of mercury. The authors have completed a preliminary analysis of the forms of mercury on three types of carbon-based sorbents using XAFS.« less

International field intercomparison of atmospheric mercury measurement methods

To determine the extent of comparability of sampling and analytical procedures for atmospheric mercury (Hg) being used by different scientific groups around the world and hence the compatibility of measurement results, the Atmospheric Environment Service (AES) co-ordinated a field intercomparison study in Windsor, Ontario, over a period of 5 days- during Sept./Oct.,1993. This study brought together 2 groups (University of Michigan Air Quality Laboratory; Chemistry Institute of GKSS) which performed conventional (manual) sample collection procedures for total gaseous mercury (TGM) and for particulate-phase mercury (PPM), followed by cold-vapor atomic fluorescence spectrophotometric (CVAFS) analysis in the respective laboratories. Two other groups (Ontario Hydro, and the Ontario Ministry of Environment & Energy) each operated a novel mercury vapor analyzer produced by Tekran Inc. of Toronto. As is the case for the manual methods, this analyzer also uses gold amalgamation and CVAFS. During the intercomparison, meteorological parameters (air temperature, barometric pressure, wind speed/direction and relative humidity) were obtained at the study site.