Hg Emission Rates Research Articles

A Quantitative Method to Measure the Kinetics of Elemental Mercury Emissions From Black Shale (Nova Scotia, Canada).

A controlled chamber method using continuous gold trap atomic fluorescence spectroscopy (AFS) (Tekran 2537X) for the analysis of Hg(0) emissions from moderate mass rock samples was developed and tested. A series of black shale and other bedrock samples from Nova Scotia, Canada, were used to test the method and its reproducibility. Hg(0) emissions at 170°C were measured to quantify both free surficial Hg(0) and Hg(0) that had penetrated the rock structure. High volumes of chamber air (45 L) were sampled using 30min collection times to achieve detectable elemental mercury (Hg(0)) emissions. We found higher percentage masses of Hg(0) were released (1.1%-4.1% of total Hg mass present) in black shale samples as compared to granite and basalt samples from the same region (0.0%-0.3% released) over 350h of continuous analysis time. The pseudo first order emission rate constants ranged from 0.015-0.245h-1 (mean 0.063h-1, standard deviation (SD) 0.102) for the black shale samples analyzed and was 0.004h-1 for the granite sample. The 24-h zero-order emission rate constants ranged between 0.41 and 3.54ngh-1 (mean 1.4ngh-1, SD 1.3) for the black shale samples analyzed and were ~ 0.01ngh-1 for the granite and basalt samples. This technique has useful implications for examining rock properties and Hg(0) emission rates.

Geolocators link marine mercury with levels in wild seabirds throughout their annual cycle: Consequences for trans-ecosystem biotransport

Seabirds are widely used as indicators of marine pollution, including mercury (Hg), because they track contaminant levels across space and time. However, many seabirds are migratory, and it is difficult to understand the timing and location of their Hg accumulation. Seabirds may obtain Hg thousands of kilometers away, during their non-breeding period, and deposit that Hg into their terrestrial breeding colonies. We predicted that Hg concentration in rectrices reflects exposure during the previous breeding season, in body feathers reflects non-breeding exposure, and in blood collected during breeding reflects exposure during current breeding. To test this hypothesis, we measured total Hg concentration in these three tissues, which reflect different timepoints during the annual cycle of rhinoceros auklets (Cerorhinca monocerata) breeding on both sides of the North Pacific (Middleton Island in Alaska and Teuri Island in Hokkaido), and tracked their wintering movement patterns with biologging devices. We (i) identify the wintering patterns of both populations, (ii) examine Hg levels in different tissues representing exposure at different time periods, (iii) test how environmental Hg exposure during the non-breeding season affects bird contamination, and (iv) assess whether variation in Hg levels during the non-breeding season influences levels accumulated in terrestrial plants. Individuals from both populations followed a figure-eight looping migration pattern. We confirm the existence of a pathway from environmental Hg to plant roots via avian tissues, as Hg concentrations were higher in plants within the auklet colonies than at control sites. Hg concentrations of breast feathers were higher in Alaskan than in Japanese auklets, but Hg concentrations in rectrices and blood were similar. Moreover, we found evidence that tissues with different turnover rates could record local anthropogenic Hg emission rates of areas visited during winter. In conclusion, Hg was transported across thousands of kilometers by seabirds and transferred to local plants.

Atmospheric emission of mercury due to combustion of steam coal and domestic coal in China

To study the mercury emission due to the combustion of steam coal and domestic coal in China, we analyzed the mercury contents of coal, fly ash, bottom ash and sluicing water in thermal power plants, steam boilers as well as domestic coal-stoves, in Shaanxi, Shanxi, Shandong and Yunnan Provinces. This study conduct an estimate of the Hg emission rates from steam coal and domestic coal combustion based on the method of mass distribution ratio of fly ash and bottom ash. The results show that the Hg emission rate of coal combustion in thermal power plants is about 50.21% (electrostatic precipitators + wet flue gas desulfurization), and that in heating boilers is about 67.23%, and 92.28% in industrial boilers without flue gas desulphurisation equipment. Furthermore, Hg emission rate is 83.61% due to domestic coal combustion in coal-stoves. The Hg emission amount into the atmosphere from power and heat generation, industrial boilers, domestic coal-stoves and spontaneous combustion of coal gangue is roughly estimated to be 133 ± 4, 100 ± 17, 11 ± 0.1 and 47 ± 26 tons in China in 2014, respectively, and the total Hg emission amount from this paper is estimated at 292 tons. The trends of Hg emission in China from 1991 to 2014 show an accelerating growth after 2002. The proportion of mercury emission due to thermal power, heating generation and industrial energy utilization continuously increased. The atmospheric emission of mercury due to combustion of steam coal, domestic coal and coal gangue accounts nearly 50% in total anthropogenic Hg emissions in China, indicating one of the largest sources of Hg emission in China which should draw more public and scientific attention in the future.

Declining Mercury Concentrations in Bluefin Tuna Reflect Reduced Emissions to the North Atlantic Ocean.

Tunas are apex predators in marine food webs that can accumulate mercury (Hg) to high concentrations and provide more Hg (∼40%) to the U.S population than any other source. We measured Hg concentrations in 1292 Atlantic bluefin tuna (ABFT, Thunnus thynnus) captured in the Northwest Atlantic from 2004 to 2012. ABFT Hg concentrations and variability increased nonlinearly with length, weight, and age, ranging from 0.25 to 3.15 mg kg-1, and declined significantly at a rate of 0.018 ± 0.003 mg kg-1 per year or 19% over an 8-year period from the 1990s to the early 2000s. Notably, this decrease parallels comparably reduced anthropogenic Hg emission rates in North America and North Atlantic atmospheric Hg0 concentrations during this period, suggesting that recent efforts to decrease atmospheric Hg loading have rapidly propagated up marine food webs to a commercially important species. This is the first evidence to suggest that emission reduction efforts have resulted in lower Hg concentrations in large, long-lived fish.

Effect of eutrophication on mercury (Hg) dynamics in subtropical reservoirs from a high Hg deposition ecoregion

Eutrophication can have opposite effects on mercury (Hg) bioavailability in aquatic systems, by increasing methylmercury (MeHg) production but reducing Hg biomagnification. Globally, the effect of eutrophication on Hg dynamics remains largely untested at lower latitudes such as eastern China, a productive subtropical ecoregion with Hg emission and deposition rates that are among the highest worldwide. Here, we quantify Hg (both MeHg and total Hg, THg) concentrations, Hg bioaccumulation, and Hg biomagnification rates in reservoir food webs across a gradient of eutrophication indicated by chlorophyll a (Chl a), zooplankton density, and total phosphorus (TP). We also assess the effect of hydrogeomorphic (HGM) features on Hg concentrations in water and biota. Water THg concentrations were strongly correlated with TP and were greater in reservoirs at higher elevations with short water retention times (WRT). Zooplankton and top predator THg concentrations were negatively correlated with Chl a, suggesting algal biodilution; evidence for zooplankton density dilution was also found when subtropical reservoirs were compared at a global scale with temperate lakes. Mercury bioaccumulation and biomagnification factors, respectively, did not correlate with increasing Chl a or zooplankton density suggesting no effect of plankton density on Hg trophic transfer. In subtropical reservoirs, eutrophication is associated with lower Hg concentrations in biota but does not explain Hg biomagnification; HGM features (i.e., elevation, WRT) and land use (i.e., % crop) appear to also influence Hg concentrations and bioaccumulation in reservoir food webs.

Control strategies of atmospheric mercury emissions from coal-fired power plants in China

Atmospheric mercury (Hg) emission from coal is one of the primary sources of anthropogenic discharge and pollution. China is one of the few countries in the world whose coal consumption constitutes about 70% of total primary energy, and over half of coals are burned directly for electricity generation. Atmospheric emissions of Hg and its speciation from coal-fired power plants are of great concern owing to their negative impacts on regional human health and ecosystem risks, as well as long-distance transport. In this paper, recent trends of atmospheric Hg emissions and its species split from coal-fired power plants in China during the period of 2000–2007 are evaluated, by integrating each plant's coal consumption and emission factors, which are classified by different subcategories of boilers, particulate matter (PM) and sulfur dioxide (SO2) control devices. Our results show that the total Hg emissions from coal-fired power plants have begun to decrease from the peak value of 139.19 t in 2005 to 134.55 t in 2007, though coal consumption growing steadily from 1213.8 to 1532.4 Mt, which can be mainly attributed to the co-benefit Hg reduction by electrostatic precipitators/fabric filters (ESPs/FFs) and wet flue gas desulfurization (WFGD), especially the sharp growth in installation of WFGD both in the new and existing power plants since 2005. In the coming 12th five-year-plan, more and more plants will be mandated to install De-NOx (nitrogen oxides) systems (mainly selective catalytic reduction [SCR] and selective noncatalytic reduction [SNCR]) for minimizing NOx emission, thus the specific Hg emission rate per ton of coal will decline further owing to the much higher co-benefit removal efficiency by the combination of SCR + ESPs/FFs + WFGD systems. Consequently, SCR + ESPs/FFs + WFGD configuration will be the main path to abate Hg discharge from coal-fired power plants in China in the near future. However, advanced specific Hg removal technologies are necessary for further reduction of elemental Hg discharge in the long term. Implications Controlling of atmospheric Hg discharge from coal-fired power plants have aroused great concerns for its adverse impacts on regional environment and human health risks, as well as long-distance transportation. It is of great significance for Chinese decision makers to be aware of the current status of Hg emissions from coal-fired power plants, so that the regulations and policies regarding Hg abatement can be made that are cost-effective and feasible implementation. This study provides the recent trend of atmospheric Hg emissions from coal-fired power plants, and accordingly proposes the preliminary comprehensive Hg control strategies suggestion in the future, which will be helpful for relevant policy making to minimize the harmful risks on environment and human health in China.

Potential Indoor Air Exposures and Health Risks from Mercury Off-Gassing of Coal Potential Indoor Air Exposures and Health Risks from Mercury Off-Gassing of Coal

Coal combustion products (CCPs), including coal fly ash (CFA) and flue gas desulfurization (FGD) gypsum, have gained accepted use as substitutes for traditional substances in building materials. Because of the presence of mercury (Hg) in CCP materials, some concerns have been raised regarding the potential for Hg to off-gas from building materials into indoor air. Risk assessment offers a well-accepted, objective framework in which to determine whether such off-gassing could result in human exposures of health concern. We thus conducted a screening-level human health risk assessment to estimate worst-case inhalation risks from indoor air exposures to Hg for multiple CCP utilization scenarios: (1) FGD-gypsum wallboard used in a school classroom or home, and (2) CFA concrete blocks used in a school classroom. For CFA concrete, published experimental data for Hg emissions during dry curing of concrete were used to calculate a high-end emission rate, and based on extrapolation of these data, an emission rate considered to be more representative of long-term emissions. For wallboard, Hg emission rates were estimated using published data from flux chamber experiments measuring Hg volatilization from FGD-gypsum wallboard samples. Together with the estimated emission rates and conservative values for other parameters (e.g., building characteristics, exposure conditions), a steady-state indoor air model was used to predict indoor air Hg concentrations. Even for parameters intended to overstate potential exposures, predicted indoor air Hg concentrations were typically below background indoor Hg levels. Additionally, estimated Hg air concentrations were well below established inhalation toxicity criteria (noncancer hazard quotients \[HQs\] ranged from 0.00004 to 0.016). Based on our findings, we conclude that potential indoor air Hg exposures associated with the use of CCPs in concrete and wallboard building materials in either classroom settings or residential homes are associated with negligible human health risks.

Distribution and air-sea exchange of mercury (Hg) in the Yellow Sea

Abstract. The Yellow Sea, surrounded by East China and the Korea Peninsula, is a potentially important receptor for anthropogenic mercury (Hg) emissions from East Asia. However, there is little documentation about the distribution and cycle of Hg in this marine system. During the cruise covering the Yellow Sea in July 2010, gaseous elemental mercury (GEM or Hg(0)) in the atmosphere, total Hg (THg), reactive Hg (RHg) and dissolved gaseous mercury (DGM, largely Hg(0)) in the waters were measured aboard the R/V Kexue III. The mean (±SD) concentration of GEM over the entire cruise was 2.61 ± 0.50 ng m−3 (range: 1.68 to 4.34 ng m−3), which were generally higher than other open oceans. The spatial distribution of GEM generally reflected a clear gradient with high levels near the coast of East China and low levels in open waters, suggesting the significant atmospheric Hg outflow from East China. The mean concentration of THg in the surface waters was 1.69 ± 0.35 ng l−1 and the RHg accounted for a considerable fraction of THg (RHg: 1.08 ± 0.28 ng l−1, %RHg/THg = 63.9%). The mean concentration of DGM in the surface waters was 63.9 ± 13.7 pg l−1 and always suggested the supersaturation of Hg(0) in the surface waters with respect to Hg(0) in the atmosphere (the degree of saturation: 7.8 ± 2.3 with a range of 3.6–14.0). The mean Hg(0) flux at the air-sea interface was estimated to be 18.3 ± 11.8 ng m−2 h−1 based on a two-layer exchange model. The high wind speed and DGM levels induced the extremely high Hg(0) emission rates. Measurements at three stations showed no clear vertical patterns of DGM, RHg and THg in the water column. Overall, the elevated Hg levels in the Yellow Sea compared with other open oceans suggested that the human activity has influenced the oceanic Hg cycle downwind of East Asia.

Mercury emission and dispersion models from soils contaminated by cinnabar mining and metallurgy

The laboratory flux measurement system (LFMS) and dispersion models were used to investigate the kinetics of mercury emission flux (MEF) from contaminated soils. Representative soil samples with respect to total Hg concentration (26-9770 μg g(-1)) surrounding a decommissioned mercury-mining area (Las Cuevas Mine), and a former mercury smelter (Cerco Metalúrgico de Almadenejos), in the Almadén mercury mining district (South Central Spain), were collected. Altogether, 14 samples were analyzed to determine the variation in mercury emission flux (MEF) versus distance from the sources, regulating two major environmental parameters comprising soil temperature and solar radiation. In addition, the fraction of the water-soluble mercury in these samples was determined in order to assess how MEF from soil is related to the mercury in the aqueous soil phase. Measured MEFs ranged from less than 140 to over 10,000 ng m(-2) h(-1), with the highest emissions from contaminated soils adjacent to point sources. A significant decrease of MEF was then observed with increasing distance from these sites. Strong positive effects of both temperature and solar radiation on MEF was observed. Moreover, MEF was found to occur more easily in soils with higher proportions of soluble mercury compared to soils where cinnabar prevails. Based on the calculated Hg emission rates and with the support of geographical information system (GIS) tools and ISC AERMOD software, dispersion models for atmospheric mercury were implemented. In this way, the gaseous mercury plume generated by the soil-originated emissions at different seasons was modeled. Modeling efforts revealed that much higher emissions and larger mercury plumes are generated in dry and warm periods (summer), while the plume is smaller and associated with lower concentrations of atmospheric mercury during colder periods with higher wind activity (fall). Based on the calculated emissions and the model implementation, yearly emissions from the "Cerco Metalúrgico de Almadenejos" decommissioned metallurgical precinct were estimated at 16.4 kg Hg y(-1), with significant differences between seasons.

New clues on the contribution of Earth’s volcanism to the global mercury cycle

Active volcanoes are thought to be important contributors to the atmospheric mercury (Hg) budget, and this chemical element is one of the most harmful atmospheric pollutants, owing to its high toxicity and long residence time in ecosystems. There is, however, considerable uncertainty over the magnitude of the global volcanic Hg flux, since the existing data on volcanogenic Hg emissions are sparse and often ambiguous. In an attempt to extend the currently limited dataset on volcanogenic Hg emissions, we summarize the results of Hg flux measurements at seven active open-conduit volcanoes; Stromboli, Asama, Miyakejima, Montserrat, Ambrym, Yasur, and Nyiragongo.. Data from the dome-building Soufriere Hills volcano are also reported. Using our determined mercury to SO2 mass ratios in tandem with the simultaneously-determined SO2 emission rates, we estimate that the 7 volcanoes have Hg emission rates ranging from 0.2 to 18 t yr-1 (corresponding to a total Hg flux of ~41 t·yr-1). Based on our dataset and previous work, we propose that a Hg/SO2 plume ratio ~10-5 is best-representative of gas emissions from quiescent degassing volcanoes. Using this ratio, we infer a global volcanic Hg flux from persistent degassing of ~95 t·yr-1 .

Reply to comment by Ted Michaels on “Recent trends in anthropogenic mercury emission in the northeast United States”: Waste‐to‐energy's low mercury emissions

[1] Sigler and Lee [2006] (hereinafter referred to as SL06) combined measurements of mercury (Hg) and a combustion tracer at a background site to estimate regional Hg emission rates in the northeast United States from 1999/2000 to 2003/2004. Significant interannual variation in regional Hg emission was observed. Inventory calculations of Hg flux from the regional electric power sector suggested that the power sector strongly influences annual variation in Hg emission in the northeast but may not account for as large of a percentage of the total atmospheric Hg flux as expected given previous inventory estimates. [2] We thank Michaels [2007] (hereinafter referred to as M07) for comments on SL06. M07 cited substantial reductions in Hg emissions from municipal waste combustors (MWC) nationwide since 1990 and a clear ability of MWC to achieve federal emissions standards and suggested improper speculation by SL06 as to the role of MWC in Hg emissions in the northeast. Here we briefly address several of the important issues raised by M07. [3] We stress that SL06 did not claim that MWC cannot or do not test significantly lower than U.S. emission standards as defined by the Clean Air Act. More importantly, SL06 did not speculate that ‘‘high mercury emission levels in the northeast might be attributable’’ to MWC and failure to achieve standards, as suggested by M07, or to the performance of any other source category. SL06 cited multiple sources which indicate significant reductions in Hg emissions from MWC in several northeastern states since the late 1990s and were led to specifically investigate inventory Hg flux from the electric power sector because the substantial decline in MWC emissions due to legislative impact would leave power plants as by far the most important Hg emission category in the northeast [U.S. Environmental Protection Agency (EPA), 1997]. Rather than qualifying or searching for reasons behind high emission rates, SL06 sought to understand the observed interannual variation in Hg emissions determined from atmospheric measurements and gain insight into the relative contributions of different sources to total emissions in the northeast. [4] SL06 posited several potential contributing factors for the observation that power sector emissions were unable to account for as high a percentage of total Hg emissions in the northeast as expected. Among them (SL06, paragraph 38) was the possibility that ‘‘emissions from municipal and medical waste combustion emissions have not been reduced to the level targeted by EPA in 1997 and still contribute significantly to the regional Hg emission rate.’’ While not intended to suggest that MWC are responsible for ‘‘high mercury emission levels’’ in the northeast or are unable to test below federal standards, this contention could be misleading and deserves clarification. [5] As M07 noted, U.S. Hg emissions from large MWC declined significantly (95%) between 1990 and 2000 because of Maximum Achievable Control Technologies (MACT) compliance [EPA, 2002]. According to EPA [1997], New Source Performance Standards (NSPS) adopted in 1995 sought to reduce U.S. Hg emissions from municipal and medical waste combustion by at least an additional 90% over 1995 levels by 2000. Using inventory estimates presented by EPA [1997] as a baseline, we therefore expected MWC emissions to have declined from roughly one third of total Hg emission (1995 inventory) in the source region considered by SL06 (New England, MidAtlantic, Maryland, and Delaware) to on the order of 5% during the observation period (1999/2000–2003/2004), assuming no changes in emission among other major sources. This is clearly not the case, despite the dramatic reductions in bulk Hg emissions from MWC that have been achieved during the past decade. For example, recent inventory data suggest that MWC may have contributed approximately 21% of total Hg emissions in the northeast (not including Pennsylvania, Maryland, and Delaware) as recently as 2002, roughly the midpoint of the observation period of SL06, despite an 86% reduction in total MWC emissions in the same region since 1998 [Northeast States for Coordinated Air Use Management (NESCAUM), 2005]. We also note that total Hg emissions from MWC in New England, New York, and New Jersey were approximately 8.5 Mg in 1995 [EPA, 1997]. If a 90% reduction were JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 112, D13314, doi:10.1029/2006JD008069, 2007 Click Here for Full Article

Degassing of gaseous (elemental and reactive) and particulate mercury from Mount Etna volcano (Southern Italy)

There is an urgent need to better constrain the global rates of mercury degassing from natural sources, including active volcanoes. Hitherto, estimates of volcanic fluxes have been limited by the poorly determined speciation of Hg in volcanic emissions. Here, we present a systematic characterisation of mercury partitioning between gaseous (Hg (g)) and particulate (Hg (p)) forms in the volcanic plume of Mount Etna, the largest open-vent passively degassing volcano on Earth. We demonstrate that mercury transport is predominantly in the gas phase, with a mean Hg (p)/Hg (g) ratio of ∼0.01 by mass. We also present the first simultaneous measurement of divalent gaseous mercury ( Hg ( g ) II ) and total gaseous mercury (Hg (g)) in a volcanic plume, which suggests that Hg ( g ) 0 is the prevalent form of mercury in this context. These data are supported by the results of model simulations, carried out with HSC thermodynamic software. Based on a mean “bulk plume” Hg/SO 2 mass ratio of 8.7×10 −6, and a contemporaneous volcanic SO 2 flux of 0.8 Mt yr −1, we estimate an Hg emission rate from Mt. Etna during passive degassing of 5.4 t yr −1 (range, 1.1–10 t yr −1). This corresponds to ∼0.6% of global volcanic Hg emissions, and about 5% of Hg released from industrial activities in the Mediterranean area.

Atmospheric mercury chemistry: Sensitivity of global model simulations to chemical reactions

The effect of new mercury (Hg) chemistry information on Hg atmospheric concentrations is investigated in a systematic manner with a global chemical transport model, taking into account current uncertainties in Hg emission and removal rates. The reactions of interest include the gas‐phase oxidation of Hg(0) by O3, the gas‐phase oxidation of Hg(0) by OH, the aqueous‐phase reduction of Hg(II) by HO2 radicals, a hypothetical gas‐phase reduction of Hg(II) by SO2, and a hypothetical pseudo‐first‐order gas‐phase reduction of Hg(II). The new kinetics of the oxidation of Hg(0) by O3 is fast and would require balancing by a commensurate reduction reaction pathway that has not been identified; it may include some heterogeneous component and should be seen as an upper limit for atmospheric applications. Eliminating the gas‐phase oxidation of Hg(0) by both O3 and OH does not lead to realistic Hg(0) concentrations even after eliminating the aqueous‐phase reduction of Hg(II) by HO2 and having a greater dry deposition rate of Hg(0). Thus gas‐phase oxidation of Hg(0) by oxidants such as O3 and/or OH is required to reproduce global Hg(0) concentration patterns. The reduction of Hg(II) by HO2 (or a reaction with a similar overall rate) is needed to balance the oxidation of Hg(0) by OH and O3 but is not needed if the gas‐phase oxidation of Hg(0) by OH is eliminated. The reduction of Hg(II) in power plant plumes can be represented by a reaction of Hg(II) with SO2; such a reaction is consistent with the global cycling of Hg. However, a first‐order reaction for Hg(II) reduction in power plant plumes is not consistent with our current understanding of the atmospheric Hg chemistry. Additional laboratory studies are recommended to address the remaining uncertainties in the atmospheric chemistry of Hg.

Air-Substrate Mercury Exchange Associated with Landfill Disposal of Coal Combustion Products

Previous laboratory studies have shown that lignite-derived fly ash emitted mercury (Hg) to the atmosphere, whereas bituminous- and subbituminous-derived fly ash samples adsorbed Hg from the air. In addition, wet flue gas desulfurization (FGD) materials were found to have higher Hg emission rates than fly ash. This study investigated in situ Hg emissions at a blended bituminous-subbituminous ash land-fill in the Great Lakes area and a lignite-derived ash and FGD solids landfill in the Midwestern United States using a dynamic field chamber. Fly ash and saturated FGD materials emitted Hg to atmosphere at low rates (−0.1 to 1.2 ng/m2hr), whereas FGD material mixed with fly ash and pyrite exhibited higher emission rates (~10 ng/m2hr) but were still comparable with natural background soils (−0.3 to 13 ng/m2hr). Air temperature, solar radiation, and relative humidity were important factors correlated with measured Hg fluxes. Field study results were not consistent with corresponding laboratory observations in that fluxes measured in the latter were higher and more variable. This is hypothesized to be partially an artifact of the flux measurement methods.

Laboratory study of air–water–coal combustion product (fly ash and FGD solid) mercury exchange

Recent laboratory research has indicated that coal fly ash derived from subbituminous and bituminous type coals is a sink for atmospheric mercury (Hg), however lignite-based ash was found to emit Hg to the air. Solids collected from systems with components that enhance Hg removal (i.e. activated carbon injection (ACI), flue gas desulfurization (FGD), and selective catalytic reduction (SCR) or selective non-catalytic reduction (SNCR)) may have higher Hg concentrations and therefore a higher potential for Hg release. For this study we investigated the potential for Hg release to the air and water from coal combustion products (CCPs) collected from coal-fired units with FGD equipment, SCR and SNCR equipment, and sorbent injection for Hg removal. In the laboratory study, most dry samples acted as sinks for atmospheric Hg in the dark at 25 °C. When exposed to light or increased temperature (45 °C), deposition of Hg to the fly ash substrates in most cases continued but decreased. Wet FGD samples emitted Hg. However, they became a sink for atmospheric Hg or exhibited low Hg emission rates when dried. Mercury flux in the dark at 25 °C was correlated with fly ash carbon content (LOI). Most liquid extracts derived using the synthetic precipitation leaching procedure (SPLP EPA method 1312) had very low Hg concentrations (<13 ng/l).

Exchange rate of mercury between atmosphere and different kinds of Earth’s surfaces on the east slope of Mt. Gongga

Seasonal mercury flux measurements (three sampling periods: 2005 autumn, 2005 winter, and 2006 spring) were conducted at two soil sites, two grasslands and a cornfield on the east slope of Nit. Gongga, located in the southwest of Sichuan Province, China. The mercury flux was monitored using a dynamic flux chamber (DFC) method, and mercury concentrations in the air were measured with a TEKRAN 2537A Mercury Vapor Analyzer. Mercury exchange rates show a distinctly seasonal pattern and vary from-18.7• ng .m -2 "h "1 in winter to 19.2:L26.5 ng *m "2 .h "1 in spring, Hg exchange flux is a bidirectional process, however, it is dominated by dry deposition in winter and emission of mercury is the main process in some other seasons, besides the climate influence on mercury exchange rates. Atmosphere gaseous mercury concentration is anther important factor, high atmosphere mercury concentration (7.6 ng 9 m -a, nearly two times higher than in the spring, 3.2 ng 9 m "3 ) in winter caused by anthropogenic sources bated mercury emission from land surfaces and enhanced Hg deposition. According to our research, vegetation cover can lower mercury flux and increase dry deposition, and this may imply that plants in the background site are the sink of atmosphere mercury. Hg fluxes showed a clear diurnal pattern when the conditions were both sunny and overcast that Hg emission rate reached the maximum at noon and fell to the minimum at night. The daytime mercury flux rate peak is obviously related to solar radiation. The flux also significantly correlates with air temperature, and negatively correlates with air relative humidity.

Mercury emission to atmosphere from Lanmuchang Hg–Tl mining area, Southwestern Guizhou, China

In situ mercury emission fluxes from soil in Lanmuchang Hg–Tl mining area, southwestern Guizhou, China, were measured using dynamic flux chamber (DFC) method in December 2002 and May 2003, respectively. Huge mercury emission fluxes from soil were obtained in the mining area, ranging from −623 to 10 544 ng m −2 h −1 ( n = 92 ) with the maximal mean Hg flux of 2283±2434 ng m −2 h −1. Meanwhile, highly elevated total gaseous mercury (TGM) concentrations in the ambient air observed during the sampling periods varied from 35.2±26.1 ng m −3 (7.9–353.8 ng m −3, n = 532 ) in cold season to 111.2 ± 91.8 ng m - 3 ( 12.7 – 468.0 ng m - 3 , n = 903 ) in the warm season, respectively. The correlations between mercury emission fluxes and environmental parameters, such as solar radiation, temperature, TGM concentration in air, relative humidity and soil Hg concentration are studied. The strong Hg emission fluxes resulted in the elevated TGM concentrations in the ambient air in the study area. We acquired a significant Log–Log correlation between the ratio of average Hg flux and average solar radiation and the soil Hg concentrations at all sampling sites in warm and cold seasons. Within the Langmuchang Hg–Tl mining area with a total area of ∼2.9 km 2, the annual Hg emission rate is calculated to be ∼3.54 kg Hg, which is a strong mercury emission source to the local ambient air.

Evaluation and applications of a gaseous mercuric chloride source

In this study, a diffusion-type device for generating gaseous mercuric chloride (HgCl(2)) was systematically evaluated and applied to validate the annular denuder method for sampling gaseous HgCl(2) species in a synthetic gas stream. The results show that it takes at least 48 h for the system to reach a steady-state condition after the diffusion cell reaches the temperature set-point and the carrier gas is activated. The primary Hg species from the source was proven to be HgCl(2). In the temperature range from -5.00 to 11.80 degrees C, the Hg emission rates from the source vary from 1.8 to 14.2 pg min(-1). It is shown that, under the experimental conditions examined, KCl-coated annular quartz denuders designed for ambient reactive gaseous mercury (RGM) collection could quantitatively collect HgCl(2). It is also demonstrated that the impactors used to remove coarse airborne particulate matter could lead to a loss of up to one third of the HgCl(2) in the gas stream.

Gaseous mercury exchange rate between air and water over Baihua reservir, Guizhou, China during cold season

Field measurement campaigns over lake water surface at Baihua reservoir in Guiyang, Southwestern China were conducted to measure mercury flux using a dynamic flux chamber technique coupled with automatic mercury vapor-phase analyzer from October 30 to November 4, 2001. The dynamic flux chamber is made of quartz glass, and has low blanks. Water samples were collected, and dissolved gaseous mercury (DGM), reactive and total mercury concentrations in water were measured using gold trap pre-concentration and AFS detection method. Meanwhile meteorological parameters, such as wind speed, wind direction, intensity of solar radiation, air and water temperature, and relative humidity were monitored using a portable weather station. Water surface is a net atmospheric mercury emission source even at cold season (autumn), and the average mercury emission rate is 3.0 ng/m 2 .h. We observed a strong correlation between wind speed and mercury emission rate, suggesting that strong wind facilitate mercury evaporation process from the water system during cold season. No significant correlations between Hg emission rate and solar radiation, water and air temperature were obtained.

Mercury in soil near a long-term air emission source in southeastern Idaho

At the Idaho National Engineering and Environmental Laboratory in southeastern Idaho, a 500 °C fluidized bed calciner was intermittently operated for 37 years, with measured Hg emission rates of 9–11 g/h. Surface soil was sampled at 57 locations around the facility to determine the spatial distribution of Hg fallout and surface Hg variability, and to predict the total residual Hg mass in the soil from historical emissions. Measured soil concentrations were slightly higher (p<0.05) within 5 km of the source but were overall very low (15–20 ng/g) compared to background Hg levels published for similar soils in the USA (50–70 ng/g). Concentrations decreased 4%/cm with depth and were found to be twice as high under shrubs and in depressions. Mass balance calculations accounted for only 2.5–20% of the estimated total Hg emitted over the 37-year calciner operating history. These results suggest that much of the Hg deposited from calciner operations may have been reduced in the soil and re-emitted as Hg(0) to the global atmospheric pool.