Laboratory investigation of factors affecting mercury emissions from soils

This study was performed to identify the individual and combined effects of the most important parameters that control mercury (Hg) emissions from soil surfaces: temperature, UV-B exposure, and soil water content. Both soil temperature and UV-B exposure positively affected Hg emissions; however, the increment in Hg emissions was significantly different between wet and dry soils. Mercury emissions from wet soil were more sensitive to an increase in soil temperature than dry soil; however, at constant temperature dry soil emissions were more sensitive than wet soil to changes in UV-B exposure. It was also observed that even after the relative humidity in the soil pores (RH_sp) dropped to nearly 0, the Hg emissions were still higher for initially wet soil than for dry soil, suggesting that initially high water content continued to promote Hg reduction mechanisms for an extended period. These results show the interacting effects of soil moisture with other important parameters. At constant water content, Hg emissions increased the most when the soil was exposed to UV-B radiation, followed by UV-A radiation. With UV-C exposure, atmospheric Hg deposition and O₃ destruction were simultaneously observed.     

Total gaseous mercury emissions from mercury-enriched soil in Guizhou, China

Guizhou is located in the Circum-Pacific Global Mercuriferous Belt, and mercury concentrations in soil in this area are enriched. In-situ total gaseous mercury （TGM） exchange fluxes between air and soil surface were intensively measured at four sampling sites in Guiyang from 21 May to 16 June, 2003, and five sites in the Lanmuchang mercury mining area in December 2002 and May 2003, respectively. The in-situ Hg flux measurement was conducted with a dynamic flux chamber （DFC） of quartz. Overall, net emissions were obtained from all sampling sites. Soil mercury concentration and solar radiation have been proved to be the two most important parameters to control mercury emissions from soil. Meanwhile, rain events can enhance mercury emission rate significantly.     

Spatial variability of mercury emissions from soils in a southeastern US urban environment

We quantified gaseous mercury (Hg⁰) fluxes over soil surfaces in an urban setting during the winters of 2003 and 2004 across the metropolitan area of Tuscaloosa, AL. The objective was to provide a first inspection of the local spatial variability of mercury flux in an urban area. Flux sampling took place on bare, undisturbed, soil surfaces within four evenly spaced landuse areas of Tuscaloosa: industrial, commercial, residential, and mixed landuse. Median total gaseous mercury fluxes (ng/m² h) from each site were as follows: 4.45 (residential site), 1.40 (industrial site), 2.14 (commercial site), and 0.87 (mixed landuse site). Using non-parametric statistical analyses, the residential and mixed landuse sites were found to be statistically different from the overall median flux. Landuse and soil type are the suspected factors primarily controlling the observed spatially variable fluxes. The presence of statistically different fluxes over soil surfaces on a local scale in this preliminary study warrants additional investigation, particularly during the spring and summer seasons when terrestrial mercury emission is the highest. Providing such information will help develop better estimates of mercury emission from urban areas and, ultimately, lead to more accurate and useful spatially relevant inventories.     

Gaseous mercury emissions from urban surfaces: Controls and spatiotemporal trends

The spatial and temporal variability of Hg emissions from urban paved surfaces was assessed through repeated measurements under varying environmental conditions at six sample sites in Toronto, Ontario, Canada. The results show significant spatial variability of the Hg emissions with median values ranging from below detection limit to 5.2 ng/m²/h. Two of the sites consistently had higher Hg emissions (on several occasions >20 ng/m²/h) than the other 4, which were equivalently low (maximum emission: 2.1 ng/m²/h). A surrogate measure of the pavement Hg concentrations was obtained during each day of sampling through the collection of street dust. The median street dust concentration also showed significant spatial variability (ranging from 9.6 to 44.5 ng/g). Regression analysis showed that the spatial variability of the Hg emissions was significantly related to the street dust concentrations. Controlled experiments using Hg amended street dust confirmed the relationship between Hg surface concentration and emission magnitude. Within a given sample site, Hg emissions varied temporally and multiple regression analysis showed that within-site variability was significantly influenced by changes in solar radiation with only a minor effect from surface temperature. Controlled experiments using shade cloths confirmed that solar radiation can have a large influence on the magnitude of Hg emissions within a given site. The emissions measured in Toronto were contextualized through comparison sampling in Austin, Texas. The Hg emissions measured in Austin were within the range detected in Toronto and also showed significant correlation with Hg street dust concentrations between sites. To provide a holistic assessment of Hg emissions from urban environments, samples were also collected from other common urban surfaces (soil, roofs, and windows). Soils consistently had higher emissions than all the other surfaces (7.3 ng/m²/h, n = 39).     

Annual emissions of mercury to the atmosphere from natural sources in Nevada and California

The impact of natural source emissions on atmospheric mercury concentrations and the biogeochemical cycle of mercury is not known. To begin to assess this impact, mercury emissions to the atmosphere were scaled up for three areas naturally enriched in mercury: the Steamboat Springs geothermal area, Nevada, the New Idria mercury mining district, California, and the Medicine Lake volcano, California. Data used to scale up area emissions included mercury fluxes, measured in-situ using field flux chambers, from undisturbed and disturbed geologic substrates, and relationships between mercury emissions and geologic rock types, soil mercury concentrations, and surface heat flux. At select locations mercury fluxes were measured for 24 h and the data were used to adjust fluxes measured at different times of the day to give an average daily flux. This adjustment minimized daily temporal variability, which is observed for mercury flux because of light and temperature effects. Area emissions were scaled spatially and temporally with GIS software. Measured fluxes ranged from 0.3 to approximately 50 ng m^-2 h^-1 at undisturbed sites devoid of mercury mineralization, and to greater than 10,000 ng m^-2 h^-1 from substrates that were in areas of mercury mining. Area-averaged fluxes calculated for bare soil at Steamboat Springs, New Idria, and Medicine Lake of 181, 9.2, and 2 ng m^-2 h^-1, respectively, are greater than fluxes previously ascribed to natural non-point sources, indicating that these sources may be more significant contributors of mercury to the atmosphere than previously realized.     

Mercury in coal and the impact of coal quality on mercury emissions from combustion systems

The proportion of Hg in coal feedstock that is emitted by stack gases of utility power stations is a complex function of coal chemistry and properties, combustion conditions, and the positioning and type of air pollution control devices employed. Mercury in bituminous coal is found primarily within Fe-sulfides, whereas lower rank coal tends to have a greater proportion of organic-bound Hg. Preparation of bituminous coal to reduce S generally reduces input Hg relative to in-ground concentrations, but the amount of this reduction varies according to the fraction of Hg in sulfides and the efficiency of sulfide removal. The mode of occurrence of Hg in coal does not directly affect the speciation of Hg in the combustion flue gas. However, other constituents in the coal, notably Cl and S, and the combustion characteristics of the coal, influence the species of Hg that are formed in the flue gas and enter air pollution control devices. The formation of gaseous oxidized Hg or particulate-bound Hg occurs post-combustion; these forms of Hg can be in part captured in the air pollution control devices that exist on coal-fired boilers, without modification. For a given coal type, the capture efficiency of Hg by pollution control systems varies according to type of device and the conditions of its deployment. For bituminous coal, on average, more than 60% of Hg in flue gas is captured by fabric filter (FF) and flue-gas desulfurization (FGD) systems. Key variables affecting performance for Hg control include Cl and S content of the coal, the positioning (hot side vs. cold side) of the system, and the amount of unburned C in coal ash. Knowledge of coal quality parameters and their effect on the performance of air pollution control devices allows optimization of Hg capture co-benefit.     

Sensitivity of the global atmospheric cycle of mercury to emissions

A systematic investigation of the impact of current uncertainties in Hg emissions from specific source categories on global air Hg concentrations is presented. First, the uncertainties in different emission source categories are discussed and then the results of a base simulation and three sensitivity simulations conducted with a global chemical transport model for mercury (CTM-Hg) are presented. The total Hg emissions in the four scenarios range from 6600 to 9400 Mg/a. The sensitivity studies investigate the impact of the range in uncertainty in natural emissions, emissions of previously deposited Hg, and anthropogenic emissions both in China and worldwide, while taking into account constraints imposed by available data (current/pre-industrial emission ratio of 2–4). In one case, natural emissions and emissions of previously deposited Hg were changed to represent a mid point of the range of values found in the literature. This lead to a 16% increase in background emissions, i.e., natural emissions and emissions of previously deposited Hg combined. Increasing natural emissions by 16% or Chinese anthropogenic emissions by 100% yielded atmospheric Hg concentrations comparable with those measured across the globe without any changes to the atmospheric chemistry. Increasing natural emissions and emissions of previously deposited Hg by 16% and all anthropogenic emissions by 100% as compared to the base scenario yielded atmospheric Hg concentrations that were not compatible with measurements and changes in the chemical behavior of Hg in the atmosphere would be required to yield results that are consistent with observed Hg concentrations. The current uncertainty in total Hg emissions at the global scale is placed at about a factor of two.     

Mercury concentrations in environmental media at a hazardous solid waste landfill site and mercury emissions from the site

Mercury (Hg) concentrations in air, effluent water, landfill gas, leachate, groundwater, and soil at a hazardous solid waste landfill site in Korea were measured along with air–soil surface Hg exchange fluxes at the site. The concentrations and fluxes were considerably higher than have been found elsewhere in Korea. Gaseous Hg concentrations in the air peaked during the day, coinciding with Hg being released from the landfill surface. This suggests that air–soil exchange increased the Hg concentrations in the atmosphere. The air–soil exchange flux increased abruptly when solar radiation reached the soil surface. The Hg flux peaked about 3 h before the solar radiation peaked, possibly because reducible Hg was abundant at the soil surface. The Hg emission flux activation energy (E _a) was low, indicating that the Hg species present and Hg–soil binding were probably not as important (because of the high Hg content of the soil) as in previous studies. The methylmercury to total Hg ratios in the discharged effluent, groundwater, and leachate was clearly higher than typically found in coastal water and freshwater, suggesting bacteria caused active methylation to occur under the reducing conditions in the anaerobic landfill. The results suggested that considerable amounts of Hg are probably transported from the landfill to nearby environmental media and that this will continue if waste with a high Hg content continues to be added to the landfill without being pretreated.     

Environmental geochemistry of mercury in the area of emissions of the Karabashmed copper smelter

Mercury emissions during production of blister copper at the smelter Karabashmed are roughly estimated. The high mercury content in the atmospheric dust, soils, lake sediments of the Karabash geotechnogenic system shows that emissions of the plant are the main source of environmental contamination. The mercury content in soils of residential territory ranges within 0.2–11.4 mg/kg, reaching 15 mg/kg in soils of the impact zone. The maximum mercury content in the bottom sediments of Lake Serebry is 32 mg/kg. The high degree of contamination by other elements of emissions (Cu, Pb, Zn, As, Cd) is also demonstrated. Obtained results justify the need for the instrumental control of mercury in emissions.     

Parameters influencing the variation in mercury emissions from an Alberta power plant burning high inertinite coal over thirty-eight weeks period

Feed coals and fly ashes from a coal-fired power station burning Alberta subbituminous coal were examined for a period of thirty-eight weeks to determine the variation in emitted mercury. Feed coal samples were analyzed for proximate, calorific value and Hg content, while fly ash samples were examined for C and Hg contents. The maceral content of the feed coal was also determined. The emitted mercury was calculated and compared to mercury emitted from the stack according to a mass-balance calculation from a previous study for the same station.Mercury contents ranged from 0.029 to 0.066 mg/kg for feed coal, and from 0.069 to 0.112 mg/kg for fly ash. The carbon/char in fly ash was separated into reactive (vitrinitic/bimacerate) and less reactive (inertinitic) chars using ZnBr₂ at specific gravities of 1.7, 2.0, and 2.25 to 2.4. The result shows that there is a positive correlation between the carbon and mercury content of the fly ash. The reactive char particles in the fly ash may be responsible for the capture mercury in fly ash. The percentage of estimated captured mercury by fly ash increases with increasing carbon content (%) in fly ash. The percentage of emitted mercury for the period of 38 weeks is estimated to be within the range of 49% to 76% of the total input of mercury.     

Impact of natural water chemistry on public drinking water in Japan

Drinking water from Japan (Toyama, Kumamoto, Osaka, and Tokyo Prefecture) and France (Volvic water) was evaluated for taste and health properties using an index based on major and trace mineral content and organoleptic components. Although various reports point to calcium (Ca²⁺) as a key ingredient imparting good taste and magnesium (Mg²⁺) and sulfate (SO₄ ^2?) as causing unpleasant taste in drinking water, recent sensory threshold experiments have indicated that other major ions and minerals directly or indirectly contribute to good taste, including potassium (K), silica (SiO₂), and phosphorous (P). The present study examined major and trace constituents in water to accurately quantify water taste, flavor, and health effects in good-tasting (Volvic, Toyama, and Kumamoto water) and average-tasting water (Osaka and Tokyo water). Trace metal, volatile organic carbon, non-purgeable organic carbon and total inorganic carbon levels were evaluated as parameters influencing the sensory properties of the drinking water. All of the representative good-tasting water contained higher amounts of tasty minerals (Ca²⁺, K⁺, SiO₂) and lower amounts of unsavory, rough (Mg²⁺ and SO₄ ^2?), and bitter (Cl^?) minerals. Stiff diagrams of the water samples indicated that good-tasting water was generally bicarbonate (HCO₃ ^?) type. Seasonal variations in physicochemical parameters did not change the order of abundance of cations and anions but did affect the concentration of various ions present in the water. Trace metals also affected water flavor. Mn facilitates acetaldehyde formation and Fe is associated with polyphenolic oxidation and formation of organoleptic flavor constituents. Trihalomethanes (THMs) may also cause unpleasant drinking water flavors or odors. THMs concentrations for all samples were below 5.7 μg/L, meeting the safety and taste requirements for good drinking water. The Japanese samples were compared against Volvic water, which was used as a standard for good-tasting water. Total dissolved solids concentrations were below 300 mg/L for all specimens, in compliance with World Health Organization guidelines. The results are discussed on the basis of the balance between inorganic major ions and trace minerals and THMs concentration thresholds.     

Atmochemical mercury dispersion aureoles over active geologic structures of the northern Sea of Japan

In the autumn of 2010, contrasting dispersion aureoles of atomic mercury were revealed in the northern Sea of Japan, in the vicinity of the Vityaz’ and Alpatov Rises. Based on the elimination method, the assumption is made that the aureoles resulted from the supply of mercury from hydrothermal or water-gas bottom sources through the sea water column, either in gas bubbles or as a result of diffusion and turbulent mixing. It is inferred that gas-mercury measurements can be used in geological research in sea water areas.     

Preparation of strontium ferrite from strontium residue

Strontium ferrite was prepared from Strontium Waste Residue (SWR) as a material. Strontium chloride was obtained by leaching SWR with ammonia chloride, and then SrCl2 was converted to SrCO3. Strontium ferrite (SrFe12O19) was formed by roasting the mixture of SrCO3 and FeCl3 in a proper proportion. The structure and magnetic susceptibility of strontium ferrite were investi-gated. The results showed that strontium conversion ratio increased with decreasing SWR grain diameter. The largest ratio was pre-sented when n(NH4Cl/Sr) was 3.6. What is more, the conversion process coincided with the kinetic characteristics of fractal reaction. The magnetic susceptibility of strontium ferrite decreased with increasing Fe3+/Sr2+ mole ratio and pH. SrFe12O19 exhibited face-centered and cubic closely-packed hexagonal structures. There were the strong diffraction peaks of Fe2O3 in the X-ray diffracto-gram of strontium ferrite. Strontium recovery ratio was 87.0%.     

Diffuse soil gas emissions of gaseous elemental mercury (GEM) from hydrothermal-volcanic systems: An innovative approach by using the static closed-chamber method

This study was aimed to test a new methodological approach to carry out measurements of gaseous elemental mercury (GEM) diffusively emitted from soils in hydrothermal-volcanic environments. This method was based on the use of a static closed-chamber (SCC) in combination with a Lumex^® RA-915M analyzer that provides GEM measurements in a wide range of concentrations (from 2 to 50,000 ng m⁻³). Gas samples were collected at fixed time intervals from the SCC positioned on the ground (time-series samples). The Lumex^® inlet port was equipped with a three-way Teflon valve allowing the free entrance of air through a carbon trap, in order to: (i) prevent disturbance to the Lumex^® operative flow rate (10 L min⁻¹) during the injection of the gas samples from the SCC and (ii) minimize the instability of the baseline signal induced by possible variations of GEM concentrations in air. In the lab, known amounts of GEM, pipetted from a vessel containing an Hg-saturated air in equilibrium with liquid mercury at 27 °C, were injected in the Lumex^® via the modified inlet port to construct a calibration curve. The latter was used to calculate the amount of GEM in the SCC (K_SCC) from the corresponding GEM concentrations measured by the Lumex^® analyzer. The K_SCC values of the time-series samples were proportionally increasing with the GEM fluxes (ϕGEM), thus ϕGEM values were computed according to the following equation: ϕGEM = (dK_SCC/dt)/A, where A is the basal area of the SCC and dt is the time interval of the time-series sampling. Up to 214 ϕGEM measurements were carried out at Solfatara crater (Campi Flegrei, southern Italy), a hydrothermally altered tuff cone characterized by an anomalous diffuse soil emission of GEM-rich geogenic gases. The measured ϕGEM values varied up to 4 orders of magnitude, from 1,296, corresponding to the sensitivity of the method at the selected sampling time interval (1 min), to 1,957,500 ng m⁻² day⁻¹, and were consistent with those recently measured in this crater using a different method. In the field, 10 replicates were carried out in 5 selected sites, allowing to demonstrate that the proposed method has a high reproducibility (RDS < 4%). The ϕGEM and ϕCO₂ values, the latter being measured in the same 214 sites by using the accumulation chamber method, showed a low correlation, although both gases were originated from the same deep source. This suggests that GEM and CO₂ soil fluxes are differently affected by environmental parameters, such as soil humidity and temperature, which have a strong effect on the release of GEM from the soil, whereas they do not play a significant role in the diffuse degassing of CO₂. The measured fluxes were used to compute the CO₂ and GEM total outputs (402 and 5.41 × 10⁻⁶ t day⁻¹, respectively) from the study area (92,000 m²) and to construct contour maps showing the spatial distribution of the ϕCO₂ and ϕGEM values. By modifying the geometry of SCC and the time interval of the sampling series, the proposed method can be applied to the measurements of GEM soil fluxes in other geological systems and man-made environments.     

Acoustic emissions from stress-induced dauphiné twinning in quartz

Dauphiné (electrical) twins have been introduced into quartz crystals by means of suitably oriented mechanical stresses. Stress-induced twinning was observed optically by means of the photoelastic effect. Accompanying acoustic emission, first detected by ear, was quantitatively measured with a piezoelectric transducer and a suitable filtering and amplification system. Synchronized sound cinematography has been used to correlate the acoustic emission with visual observation of twinning. The resultant motion picture has been used to determine the stress levels required for twinning in Brazilian quartz and to set limits on the twin wall velocity. The possible relevance to rock noise and earthquake precursory phenomena is discussed.     

Mercury emission from the indigenous mercury smelting in Wuchuan mercury mining areas, Guizhou Province, China

Mercury smelting is one of the important anthropogenic atmospheric mercury emission sources. Small-scale mercury smelting activities with indigenous method which is considered illegal and forbidden by local government always extensively existed in the Wuchuan area, northeastern Guizhou Province, China. Because of the simple processes without any environmental protection, a large amount of mercury vapor released to the ambient air during the processing of cinnabar roasting. By determining mercury concentrations in mercury ore and smelting slag samples, a mass balance method was used to calculate mercury emission factors and annual mercury emission from indigenous mercury smelting in Wuchuan mercury mining areas, Guizhou Province, China. The mercury emission factors ranged from 6.9% to 32.1% with the recovery from 78.4% to 93.6% and the annual mercury emission was up to 3.7-9.6 metric tons. The results highlighted that the indigenous mercury smelting was one of the most important anthropogenic atmospheric mercury emission sources in this region.     

Spatial variations in methane emissions from natural wetlands in China

Natural wetlands are thought to be one of the largest natural sources of atmospheric methane concentrations. Although numerous studies referred to the rate of methane fluxes in different geophysical regions, only a few had estimates of the overall geographical methane emissions in China. This study estimated the spatial variations of annual methane emissions with the pixel size of 1 km × 1 km from natural wetlands, excluding water surface, in China. The natural wetland areas were extracted from the database of the 2000 land covers, and geophysical divisions were used to represent different climate conditions. Methane emission in every geophysical region was calculated based on methane release factors obtained from an extensive overview of published literature and the data of elevation and vegetation proportion. The estimated annual methane emissions ranged from 0 to 5,702.8 kg per pixel within the area of 1 km², and the spatial variation in methane emissions was strongly correlated with proportion of wetlands in the area. The total methane emission from natural wetland in China ranged from 3.48 to 7.16 Tg (terrogram, unit of weight) per year, with the mean value of 4.94 Tg per year, based on the area 133,000 km² of natural wetlands. Specifically, the wetland in Northeast China had the highest contribution in China (39 %). Inner Mongolia and Qinghai-Tibet highland represented for about 25 and 21 %, respectively. The other 15 % of the measured methane was released in Northwest, North, Central, and South China.     

Rate of mercury loss from contaminated estuarine sediments

The concentration of mercury in contaminated estuarine sediments of Bellingham Bay, Washington was found to decrease with a half-time of about 1.3 yr after the primary anthropogenic source of mercury was removed. In situ measurements of the mercury flux from sediments, in both dissolved and volatile forms, could not account for this decrease. This result suggests that the removal of mercury is associated with sediment particles transported out of the study area. This decrease was modeled using a steady-state mixing model.Mercury concentrations in anoxic interstitial waters reached 3.5 μg/l, 126 times higher than observed in the overlying seawater. Mercury fluxes from these sediments ranged from 1.2 to 2.8 × 10^?5 ng/cm²/sec, all in a soluble form. In general, higher Hg fluxes were associated with low oxygen or reducing conditions in the overlying seawater. In contrast, no flux was measurable from oxidizing interstitial water having mercury concentrations of 0.01-0.06 μ/l.     

Black carbon and organic carbon emissions from wildfires in Mexico

In Mexico, approximately 7650 wildfires occur annually, affecting 263 115 hectares of land. In addition to their impact on land degradation, wildfires cause deforestation, damage to ecosystems and promote land use change; apart from being the source of emissions of toxic substances to the environment (i.e., hydrogen cyanide, black carbon and organic carbon). Black carbon is a short-lived greenhouse pollutant that also promotes snow and ice melting and decreased rainfall; it has an estimated global warming potential close to 5000.¹ We present an estimate of the black carbon and organic carbon emissions from wildfires in Mexico from 2000 to 2012 using selected emission factors from the literature and activity data from local agencies. The results show average emissions of 5955 Mg/yr for black carbon and 62 085 Mg/yr for organic carbon. Black carbon emissions are estimated to be 14 888 Gg CO₂ equivalent (CO₂ eq) per year on average. With proper management of wildfires, such emissions can be mitigated. Moreover, improved air quality, conservation of ecosystems, improvement of visibility and maintenance of land use are a subset of the related co-benefits. Mitigating forest organic carbon emissions, which are ten times higher than black carbon emissions, would also prevent the morbidity and mortality impacts of toxic organic compounds in the environment.