Mercury Release Research Articles

Evaluation of Wetland Methyl Mercury Export as a Function of Experimental Manipulations

Mercury associated with natural enrichment, historic mining, and ore processing is a contaminant of concern in watersheds of the western USA. In this region, water is a highly managed resource and wetlands, known to be important sites of methyl mercury production, are often an integral component of watersheds. This study applied controlled manipulations of four replicated experimental wetland designs with different water and soil mercury concentrations to determine the potential impacts on methyl mercury export. Wetlands were manipulated by drying and wetting, changing hydraulic retention time, and adding sulfate and nitrate to influent waters. In a summer drying and wetting manipulation, an immediate increase in total methyl mercury release was observed with rewetting, however, concentrations decreased quickly. Drying all wetlands over the winter and rewetting in the spring resulted in high net methyl mercury output relative to that observed before drying. Net methyl mercury output was not influenced by changes in hydraulic retention time from 4 to 8 h or to 30 min, or by increasing the nitrate concentration from 0.1 to 10 mg L(-1). The addition of sulfate to the inlet waters of two mesocosms to increase concentrations from approximately 100 to 250 mg L(-1) did not result in a clear effect on methyl mercury output, most likely due to sulfate concentrations being higher than optimal for methyl mercury production. Despite the lack of response to sulfate amendments, the change in sulfate concentration between the inlet and outlet of the mesocosms and temperature were the parameters best correlated with methyl mercury outputs.

The effect of disinfectants and line cleaners on the release of mercury from amalgam

Dental practices use disinfectants or line cleaners to flush dental unit wastewater lines to minimize odor generation, remove solid waste particles and remove biofilms in dental unit water lines (DUWLs). The authors evaluated 47 disinfectants or line cleaners for their potential to release mercury from amalgam waste. They prepared each product concentration according to the manufacturer's recommendations and gently agitated it along with one amalgam specimen for 24 hours. They filtered the combined decanted liquid and rinse and analyzed it for mercury using modified U.S. Environmental Protection Agency method 245.1. Six preparations released significantly more mercury from amalgam (about 17 to 340 times) than did the deionized water control (P < .001). The amount of mercury released by the other disinfectants/line cleaners was not statistically different from that released by the control. The pH values of all preparations ranged from 1.76 to 12.35. This study and other published reports have demonstrated that preparations containing chlorine release more mercury from amalgam than did some other products and the deionized water control. As a result, the use of these products is not recommended for treating dental office wastewater lines or DUWLs.

Mercury release from deforested soils triggered by base cation enrichment

The Brazilian Amazon has experienced considerable colonization in the last few decades. Family agriculture based on slash-and-burn enables millions of people to live in that region. However, the poor nutrient content of most Amazonian soils requires cation-rich ashes from the burning of the vegetation biomass for cultivation to be successful, which leads to forest ecosystem degradation, soil erosion and mercury contamination. While recent studies have suggested that mercury present in soils was transferred towards rivers upon deforestation, little is known about the dynamics between agricultural land-use and mercury leaching. In this context, the present study proposes an explanation that illustrates how agricultural land-use triggers mercury loss from soils. This explanation lies in the competition between base cations and mercury in soils which are characterized by a low adsorption capacity. Since these soils are naturally very poor in base cations, the burning of the forest biomass suddenly brings high quantities of base cations to soils, destabilizing the previous equilibrium amongst cations. Base cation enrichment triggers mobility in soil cations, rapidly dislocating mercury atoms. This conclusion comes from principal component analyses illustrating that agricultural land-use was associated with base cation enrichment and mercury depletion. The overall conclusions highlight a pernicious cycle: while soil nutrient enrichment actually occurs through biomass burning, although on a temporary basis, there is a loss in Hg content, which is leached to rivers, entering the aquatic chain, and posing a potential health threat to local populations. Data presented here reflects three decades of deforestation activities, but little is known about the long-term impact of such a disequilibrium. These findings may have repercussions on our understanding of the complex dynamics of deforestation and agriculture worldwide.

Mercury content in electrum from artisanal mining site of Mongolia

In Mongolia, artisanal gold mining, modern gold rush, in which people use mercury to extract gold, is being proliferated rapidly and the mercury contamination of mining site is becoming a serious social issue. For the risk assessment of mercury, it is necessary to understand how much mercury is introduced to the environment from what kind of materials during mining activity. It is already known that major contribution of the contamination comes from mercury that was bought at shops and brought to mining sites by miners. However, no information is available on how much mercury is removed from electrum (natural gold grain) to the environment. Since gold deposit is always accompanied by mercury anomaly, it is anticipated that electrum grains contain some amount of mercury of natural origin, and this mercury (primary mercury) contributes to some extent to the contamination. In order to clarify how much mercury is incorporated in electrum grains, micro-PIXE at CSIRO was used for grain-by-grain analysis. The result showed that electrum from study area contains mercury up to 8260ppm. It is concluded that for the risk management of mercury contamination, release of natural mercury from electrum grains during smelting must not be ignored.

Investigations on the release of mercury from liquid eutectic lead–bismuth alloy under different gas atmospheres

Eutectic lead–bismuth alloy (LBE) samples with mercury concentrations similar to those expected for a liquid metal spallation target were prepared. The release of mercury from these samples under a continuous flow of gas was studied as a function of temperature, using γ-spectroscopy and 203Hg as a radioactive tracer. Various gas compositions ranging from a reducing atmosphere (Ar/7%H 2) to oxidising conditions (moist air) were applied. Under reducing conditions, substantial release of mercury from LBE started at temperatures around 473 K. At about 571 K, half of the mercury present in the samples was released within 1 h. Oxidising conditions led to a strong decrease in mercury release. In 1 h-experiments, no release of mercury was observed for temperatures up to 935 K within the limits of experimental error when humid air was used as a carrier gas. Apparently, the formation of an oxide layer on the surface of the melt inhibits the evaporation of Hg. This effect is of importance with respect to accident scenarios in liquid metal spallation targets, where liquid LBE could be exposed to air as well as cooling water. In such a case, a substantial decrease in the evaporation rate of mercury can be expected due to the formation of an oxide layer.

06/00746 Mercury release from FGD: Heebink, L. V. and Hassett, D. J. Fuel, 2005, 84, (11), 1372–1377.

06/00746 Mercury release from FGD: Heebink, L. V. and Hassett, D. J. Fuel, 2005, 84, (11), 1372–1377.

Mercury pollution in the atmosphere-soil-biology ecosystem along the trunk road in Guilin

Based on the mercury distribution in soil, atmosphere and plant in seven sections beside the trunk road, some advances are obtained: (1) Mercury content of fuel oil of petrol station in Guilin is 3.66-9.74 ng/g, higher than that reported by other countries (0.7-3.2 ng/g). The higher the number of petrol, the lower the content. Number 90 petrol widely used is the highest (9.74 ng/g). (2) Mercury content in soil is commonly 0.30-0.80 ixg/g near the road, (0.30--2.60 ~tg/g) besides the street, both are higher than the average of Guilin background value (0.204 ~tg/g). Mercury content in vegetable near the road is generally 0.025-0.055 ~tg/g, higher than that far away from the road (0.022-0.038 ~g/g). The content in cinnamon leaves on both sides of the street is 0.064).16 ~tg/g, also higher than that far away from the street (0.051-0.067 ~tg/g). Guilin Highway atmospheric mercury content is usually 7-12 ng/m 3, higher than the mean background value (4.4--6.6 ng/m3). Atmospheric mercury content near rural roads is below the level on urban roads. The atmospheric mercury content increases apparently in traffic-intensive stations and intersections. (3) The average concentration of mercury in vegetables is mostly 0.025-0.055 ~tg/g. Mercury content in various tissues of vegetable follows the order of leaves (mostly 0.044).09 ~tg/g)>roots (mostly 0.02-0.05 ~tg/g)>stems (mostly 0.01-0.04 ~tg/g). (4) The distribution of mercury in soil, plants and atmosphere near the road is of certain similarity, with a single peak, nearly symmetrical. As far away from road, the content reduces gradually, which shows the release of exhaust gas mercury is the main source of atmospheric mercury pollution. (5) The correlation analysis on different types of samples shows the correlation coefficients are 0.404 (atmosphere, vegetable leaves), 0.297 (soil, vegetable leaves), 0.06 (soil, cinnamon leaves) and 0.909 (traffic flow, leaves, respectively). It is suggested atmospheric mercury is the main contributor to mercury in leaves. (6) The atmospheric mercury content before rain is higher than that after rain. The flow status of air has apparent impact on mercury enrichment. (7) The mercury content of postman's hair is 2.968 ~tg/g, it is 2.74 times that of ordinary crowds hair (1.083 ~tg/g). This indicated mercury pollution from exhaust gas can affect ecological environment, and the effect should not be ignored.

Decrease of soil fertility and release of mercury following deforestation in the Andean Amazon, Napo River Valley, Ecuador

Soil erosion and degradation provoked by deforestation in the Amazon is a global concern, and recent studies propose a link between deforestation, soil erosion and the leaching of naturally occurring mercury (Hg). In the Ecuadorian Amazon, elevated deforestation rates and the proximity of volcanoes could play an important role in soil fertility and soil Hg levels. The goal of this study is to evaluate the impacts of deforestation on Andisol and Inceptisol fertility and Hg levels in the Napo River Valley, Ecuador. Results show a significant decrease in surface soil organic matter (− 15% to − 70% of C and N) and exchangeable cations (− 25% to − 60%) in deforested plots. Hg concentrations at the surface (0–5cm), higher in Andisols (225 ng/g average) than in Inceptisols (95 ng/g average), show a decrease of up to 60% following deforestation. Soil erosion exposes the mineral horizon, a layer with a higher Hg burden, to the elements thus provoking and accelerating Hg leaching. These results suggest that deforestation and the associated Hg leaching could contribute to the fish Hg contamination measured in the Napo River watershed.

Disinfectants' Effect on Mercury Release From Amalgam

Disinfectants' Effect on Mercury Release From Amalgam

Amalgam associated oral lichenoid reaction

Amalgam is one of the most widely used restorative material in dentistry. However due to continuous low level release of mercury (Hg) from amalgam Fillings, its safety and wide scale use has been questioned. The main concerns relate to the potential toxic effects of Hg and the possibility that Hg may induce adverse immunological effects. With regard to the latter. there have been a number of reports suggesting that amalgam fillings may induce oral lichen planus (OLP) like or oral Lichenoid lesions(OLL)Here we present a case report of Amalgam Associated Oral Lichenoid Reaction (AAOLR) or Amalgam Contact Hypersensitivity Lesions( ACHL)s with emphasis on current review literature.

The effect of carbamide peroxide treatment on metal ion release from dental amalgam

Objectives There is concern that hydrogen peroxide generated by tooth bleaching agents may cause enhanced metal ion release (including mercury) from dental amalgam following contact. The aim of this in vitro study was therefore to investigate the effect of a carbamide peroxide (CP) based tooth bleaching gel on metal ion release from dental amalgam. Methods Dental amalgam discs were prepared according to the manufacturers’ instructions. These were treated with either a 10% carbamide peroxide (CP) gel or a 0% CP gel for 24 h. Discs were carefully wiped with cotton wool before immersion in distilled water (20 ml) for 24 h at 37 °C. Following immersion, water samples were taken for metal ion release determination (Ag, Cu, Hg and Sn) using inductively coupled plasma mass spectrometry methods. The specimens were further evaluated for surface changes using scanning electron microscopy (SEM) and Talysurf surface roughness measurements. Results The differences in concentration of metal ions released after treatment with the 10% CP gel and a placebo gel treatment were not statistically significant ( p > 0.05). For example, mercury release following treatment with the 10% CP gel and the 0% CP gel was found to be 1.17(0.5) and 0.57(0.1) μg cm −2, respectively. Roughness measurements for samples treated with the 10% CP gel and 0% CP gel were 2.23(0.47) and 1.74(0.16) μm, respectively, again showing no significant difference between groups ( p > 0.05). SEM images of the amalgam surfaces showed no apparent differences between treatments. Significance Treatment with a 10% CP gel did not significantly enhance subsequent metal ion release from dental amalgams compared to a control gel, contradicting previously published studies.

Questions regarding environmental mercury release, special education rates, and autism disorder: An ecological study of Texas by Palmer et al.

Palmer et al. present an analysis in which they look for an association between Toxic Release Inventory (TRI) reporting data for mercury and rates of autism and special education enrollment in Texas. In their analysis, the link between TRI release data and actual mercury exposure is not clear at all, and thus the conclusions drawn from the analysis are questionable.

1357 ORAL Improvement of local tumour control after simultaneous fractionated irradiation and EGFR inhibition by C225 in FaDu hSCC in vivo is caused by the combined effect of decreased repopulation and increased reoxygenation

Riparian soils are an important environment in the transport of mercury in rivers and wetlands, but the biogeochemical factors controlling mercury dynamics under transient redox conditions in these soils are not well understood. Mercury release and transformations in the Oa and underlying A horizons of a contaminated riparian soil were characterized in microcosms and an intact soil core under saturation conditions. Pore water dynamics of total mercury (HgT), methylmercury (MeHg), and dissolved gaseous mercury (Hg0(aq)) along with selected anions, major elements, and trace metals were characterized across redox transitions during 36 d of flooding in microcosms. Next, HgT dynamics were characterized over successive flooding (17 d), drying (28 d), and flooding (36 d) periods in the intact core. The observed mercury dynamics exhibit depth and temporal variability. At the onset of flooding in microcosms (1–3 d), mercury in the Oa horizon soil, present as a combination of ionic mercury (Hg(II)) bound to thiol groups in the soil organic matter (SOM) and nanoparticulate metacinnabar (β-HgS), was mobilized with organic matter of high molecular weight. Subsequently, under anoxic conditions, pore water HgT declined coincident with sulfate (3–11 d) and the proportion of nanoparticulate β-HgS in the Oa horizon soil increased slightly. Redox oscillations in the intact Oa horizon soil exhausted the mobile mercury pool associated with organic matter. In contrast, mercury in the A horizon soil, present predominantly as nanoparticulate β-HgS, was mobilized primarily as Hg0(aq) under strongly reducing conditions (5–18 d). The concentration of Hg0(aq) under dark reducing conditions correlated positively with byproducts of dissimilatory metal reduction (∑(Fe,Mn)). Mercury dynamics in intact A horizon soil were consistent over two periods of flooding, indicating that nanoparticulate β-HgS was an accessible pool of mobile mercury over recurrent reducing conditions. The concentration of MeHg increased with flooding time in both the Oa and A horizon pore waters. Temporal changes in pore water constituents (iron, manganese, sulfate, inorganic carbon, headspace methane) all implicate microbial control of redox transitions. The mobilization of mercury in multiple forms, including HgT associated with organic matter, MeHg, and Hg0(aq), to pore waters during periodic soil flooding may contribute to mercury releases to adjacent surface waters and the recycling of the legacy mercury to the atmosphere.

Application of Relaxed Eddy Accumulation Technique to Quantify Hg0 Fluxes Over Modified Soil Surfaces

Fluxes of mercury from a waste repository and from an agricultural field amended with sewage sludge were measured. The measurements were performed by utilising a Relaxed Eddy Accumulation (REA) system synchronously coupled to automated mercury cold vapour atomic fluorescence analysers (CVAFA). The waste repository was severely contaminated and fluxes of between 0.16μg m−2 h−1 and 29μg m−2 h−1 could be measured. Fluxes at the slightly contaminated agricultural field measured between 8 ng m−2 h−1 and 1.9μg m−2 h−1. The results showed that the REA-CVAFA system could be used for measurements above both severely-and slightly contaminated soils. The measurements at the chlor-alkali plant showed that temperature was the most important parameter controlling the release of mercury at this site. At the agricultural field, the measurements indicated that both solar radiation and temperature may have influenced the emissions. Most of the mercury added to the field was lost to the atmosphere during the summer season.

Elevated mercury concentrations in fish in lakes in the Mackenzie River Basin: The role of physical, chemical, and biological factors

During the mid-1990s and through the early 2000s, researchers determined that elevated mercury concentrations were a common occurrence in predatory fish in many lakes in the Mackenzie River Basin (MRB), located in northern Canada. Here we present the results of studies investigating factors contributing to higher mercury concentrations in fish in many of these lakes. Twenty-two percent of lake trout, 33% of northern pike, and 50% of walleye populations had mean mercury concentrations > 0.5 μg/g, the guideline for the commercial sale of fish. Higher mercury concentrations were strongly associated with the relatively old age of MRB predatory fish; mean age ranged from 7.6 to 24.9 years for the three species. In contrast, none of the lake trout sampled in eight lakes further south in northern Saskatchewan and Alberta had mean mercury concentrations > 0.5 μg/g; fish also were younger (mean age 6 years for the 8 lakes). Mercury concentrations in MRB fish generally increased with fish length, age, and trophic feeding although the nature of these relationships varied with the lake. Mean length was a good predictor of mean mercury concentrations in walleye populations across the study lakes but not for whitefish, lake trout, and pike; age was a good predictor for lake trout and walleye. Mercury concentrations in water and invertebrates were similar to those observed in more southerly regions where fish do not have elevated mercury concentrations. Mercury concentrations tended to be higher in fish in smaller vs. larger lakes and as a probable consequence of higher summer epilimnion temperatures, which favour a higher net methylation rate, and higher mercury and methyl mercury concentrations in water which enter these lakes from the watershed. Increasing fishing pressures on MRB lakes may be a means of reducing mean fish age, improving growth rates, and decreasing mercury body burdens. Increased global warming may result in higher mercury concentrations in fish through increased water temperatures, a longer ice free season, and increased release of stored mercury from the watershed into these lakes.

Disinfectants' effect on mercury release from amalgam

Mercury environmental discharge is under increased scrutiny by the U.S. Environmental Protection Agency (EPA). Dental amalgam should be processed properly to prevent an additional environmental burden. Some processing agencies require that submitted amalgam be noninfectious. Investigations have demonstrated that oxidizing disinfectants mobilize mercury from amalgam into solution and add mercury to the environmental burden if it is disposed of improperly. The authors conducted a study to evaluate the effect of representative disinfectants on amalgam mercury release. The authors sized a high-copper spherical amalgam alloy to match that typically found in dental unit suction traps. They exposed 20 grams of the alloy to several disinfectant solutions and evaluated the filtered supernatant solution for mercury content. Chlorine disinfectant materials discharged the most mercury ions, followed by bromide, iodophor, peroxide/peracetic acid and phenolic disinfectants. The quaternary ammonium compound did not discharge mercury ions above the detection limit (0.2 parts per billion) into solution. A quaternary ammonium compound did not mobilize mercury ions into solution when used as a disinfectant agent for amalgam. Chlorine disinfectants mobilized mercury ions the most, followed by bromide, iodophor, peroxide/peracetic acid and phenolic disinfectants. Dentists are obligated to be good environmental stewards and should follow practices that reduce environmental mercury release. Dental personnel should be aware that oxidizing disinfectants mobilize mercury ions into solution, which will be added to the environment if they are processed improperly. If required by processing, dental personnel should consider the different oxidizing effects of commonly used disinfectants.

Gaseous Mercury from Curing Concretes that Contain Fly Ash: Laboratory Measurements

Total gaseous mercury in headspace air was measured for enclosed concretes dry curing at 40 degrees C for intervals of 2, 28, and 56 days. Release of mercury was confirmed for ordinary Portland cement concrete (OPC) and three concretes in which class F fly ash substituted for a fraction of the cement: (a) 33% fly ash (FA33), (b) 55% fly ash (FA55), and (c) 33% fly ash plus 0.5% mercury-loaded powdered activated carbon (HgPAC). Mean rates of mercury release (0.10-0.43 ng/day per kg of concrete) over the standard first 28 days of curing followed the order OPC < FA33 approximately FA55 < HgPAC. The mercury flux from exposed surfaces of these concretes ranged from 1.9 +/- 0.5 to 8.1 +/-2.0 ng/m(2)/h, values similar to the average flux for multiple natural substrates in Nevada, 4.2 +/- 1.4 ng/m(2)/h, recently published by others. Air sampling extending for 28 days beyond the initial 28-day maturation for OPC, FA55, and HgPAC suggested that the average Hg release rate by OPC is constant over 56 days and that mercury release rates for FA55 and HgPAC may ultimately diminish to levels exhibited by OPC concrete. The release of mercury from all samples was less than 0.1% of total mercury content over the initial curing period, implying that nearly all of the mercury was retained in the concrete.

Increased Ethyl Mercury Load in Protein A Immunoadsorption

Immunoadsorption is an adsorption technique for extracorporeal removal of circulating autoantibodies in autoimmune diseases. To prevent microbial growth during storage, the protein A columns are primed with thiomersal, which contains toxic ethyl mercury, which may be released during the procedure and potentially begin to accumulate and become toxic. To reduce the thiomersal-related mercury release during immunoadsorption treatment, we introduced a modified rinsing solution containing N-acetylcysteine, which is an avid mercury scavenger. Thirteen patients received 17 protein A immunoadsorption treatments and their venous blood samples were collected immediately before and after each session. The total blood mercury levels were measured by atomic absorption spectrometry, and the ethyl mercury levels by atomic fluorescence spectrometry. Following the manufacturer's recommendations, we used 600 mg of N-acetylcysteine to rinse the mercury from protein-loaded columns before each immunoadsorption treatment. After immunoadsorption, the ethyl mercury levels increased from 0.148 +/- 0.402 ng/g to 2.026 +/- 1.944 ng/g (P < 0.001), and the total blood mercury levels increased from 2.447 +/- 3.065 ng/g to 20.437 +/- 28.603 ng/g (P = 0.02). The post-treatment values of total blood mercury exceeded the upper safety level of 5 ng/g in all 17 immunoadsorption treatments, but no patient developed clinical signs of mercury toxicity. The results of our study showed an increase in total blood mercury and ethyl mercury levels during the immunoadsorption treatments, suggesting mercury release from thiomersal-primed columns despite the addition of N-acetylcysteine to the rinsing solution.

An analytical study of bioaccumulation and the binding forms of mercury in rat body using thermolysis coupled with atomic absorption spectrometry

This study concerns with the development and application of a mercury analyzer system capable of quantitative analysis and binding forms of trace mercury in different body tissues of rats after oral intake of cinnabar and HgCl 2. The analyzer consists of a temperature programmed thermolysis unit for sample decomposition and mercury release, coupled downstream to an atomic absorption spectrometry for mercury detection. No sample digestion was needed and this greatly simplifies the analytical procedure and minimizes potential sources of contamination. The precision of the method is in general better than 1.4%; the detection limit (3 σ) is 6.3 ng/g; the recovery based on the analysis of standard reference materials ranges from 93.5 to 107%. The performance of the method has been compared with inductively coupled plasma–mass spectrometry (ICP–MS) technique and excellent agreements were observed between the two methods. The method has been applied to the investigation of the distribution and binding forms of mercury in rats, which had been fed orally with cinnabar and HgCl 2. The results obtained show that mercury is mainly accumulated in the tissues of liver and kidney, meanwhile, the mercury levels in different tissues change with the feeding time, dosage and the chemical form of mercury compounds. In addition to total mercury measurements, the mercury thermal release profiles obtained from temperature programmed thermolysis provides mercury binding forms information, and preliminary data suggest the presence of protein/polypeptide-bound Hg compounds in kidney samples of rats.

Another Mercury Scare, or Cause for Concern?

Factors affecting mercury release from dental amalgam exposed to carbamide peroxide bleaching agent. I Rotstein, Y Avron, H Shemesh, H Dogan, C Mor and D Steinberg. American Journal of Dentistry 2004; 17:347–350.