Volatile Mercury Research Articles

76. Measurement of volatile mercury emitted from geothermal fields(Abstracts of Papers Presented at the Fall Meeting of the Society)

76. Measurement of volatile mercury emitted from geothermal fields(Abstracts of Papers Presented at the Fall Meeting of the Society)

Ethanol reveals novel mercury detoxification step in tissues.

Volatile mercury was produced de novo by mouse tissue homogenates that contained mercuric ions. Ethanol stimulated the release of tissue mercury into the vapor phase, and the mechanism appears to be an inhibition of reoxidation of volatile mercury. Components responsible for mercury volatilization are heat-labile. The highest volatilizing activity in the liver is associated with the soluble fraction obtained after centrifugation at 105,000g.

Processes taking place in the graphite tube: Anion and matrix effects in atomic absorption spectrometry. II. Determination of mercury

The atomic-absorption behaviour of different mercury compounds in the graphite tube was investigated. It was established that in the case of water-soluble volatile mercury compounds (nitrate, chloride) there is a considerable mercury loss even during the drying of the drop. The mercury can be determined, however, in the form of colloidal mercury sulphide atca. 200° C and with atomization at a relatively low temperature. Some interferences limit the use of the method in practice (compounds evaporating together with the mercury, presence of other metals producing sulphide precipitates) but the use of mercury dithizonate overcomes these limitations. The method was applied for determination of the mercury content of waste water and waste water sludge.

Determination of mercury emissions from a municipal incinerator

A cold-vapor atomic absorption system is described for the determination of volatile mercury in the stack gases of a municipal solid-waste incinerator. The gases are washed in a K/sub 2/CR/sub 2/O/sub 7//HNO/sub 3/ solution. By oxidation of the mercury in the washing bottle, a 99% collection efficiency is obtained. Total collection is guaranteed by adding a gold-coated sand absorber to the sampling train. After sampling, aliquots of the diluted absorbing solution are analyzed according to the reduction-aeration method with SnC/sub 12/. The released mercury is concentrated on a gold absorber. After thermal desorption from the gold, the mercury is measured in a modified atomic absorption spectrometer. The detection limit of the combined method is 1 ng. Calibration is achieved by injection of elemental mercury onto the gold. Generally, the reproducibility is better than 3%. The mercury concentrations found vary from 121 to 163 mu g of Hg per cubic metre of flue gas.

The Direct Determination of Mercury in Fair by Atomic Absorption Spectroscopy at the 184.9 nm Resonance Line

Abstract The direct determination of total mercury levels in human scalp hair was accomplished by atomic absorption spectroscopy at 184.9 nm through the use of a unique carbon bed atomizer. The Robinson quartz T atomizer permitted the analysis of solid hair samples, 1-cm or less in length, with no sample pretreatmant. This direct analysis eliminated both loss of volatile mercury compounds during pretreatment and contamination of the sample by added reagents. The accuracy of the determination was improved thereby. Use of the 184.9 nm line in the vacuum ultraviolet region provided increased sensitivity over the more commonly employed 253.7 nm line. A 1 % absorption signal was generated by 1.5 × 10−11 g Hg. This sensitivity allowed determination of variations as small as 0.1 ppm in mercury concentration along the hair shaft. In general, distal mercury levels were found to be higher than proximal mercury levels. Washing hair with distilled deionized water or acetone had no significant effect on proximal mercury concentration. Hair was shown to absorb elemental mercury vapor from air saturated with mercury vapor. Proximal mercury levels increased from 0.3 ng Hg/cm hair to 9.8 ng Hg/cm hair over a 7-day exposure period.

Release of volatile mercury from soils and non-vascular plants

Vegetation plays a significant role in the biogeochemical cycling of mercury. This conclusion is drawn from data presented here on bioaccumulation and subsequent release of volatile mercury from non-vascular plants together with the results of previous work. There is no obvious relation between total plant Hg or soil Hg and rate of release from the plant. Heat of vaporization for Hg 0 was calculated at 13.99 kcal/g-atom; from soil it was experimentally determined at 13.81 kcal/g-atom but from the most active vascular plant was only 9.49 kcal/g-atom.

Volatile mercury release from vascular plants

Sixty-four species of vascular plants were tested for their ability to release volatile mercury. Rates ranged from 0.001 to 39.5 μg.kg −1.hr −1 depending upon species and method of measurement. Of 13 monocot families 9 contained at least one species capable of Hg emission and of 19 dicot families, 14 possessed this ability.

Determination of total particulate mercury in air with the coleman mercury analyzer system

A simple and rapid cold-vapour atomic absorption system is described for the simultaneous determination of low ambient levels of particulate mercury and volatile mercury compounds. Of the different filters checked for particle collection, quartz fibre filters have the best properties. Sampling characteristics were considered with respect to efficiency, reproducibility and duration of sampling. The homogeneity of the solid mercury deposit on the filter was tested. Possible enrichment during sampling by absorption of volatile mercury compounds and possible mercury losses by volatilization of solid compounds were examined. After sampling the mercury is released by pyrolysis and collected on a gold-coated sand absorber. In order to avoid deactivation of the absorber by condensation of pyrolysis products or interference during the subsequent dcsorption and atomic absorption measurement of the collected mercury, a heated catalytic convertor and two specific absorbers for organic substances are inserted in the analysis line.

Determination of volatile mercury compounds in air with the coleman mercury analyzer system

A simple but very selective cold-vapour atomic absorption system is described for the determination of volatile mercury compounds at very low levels in ambient air. Three different absorbers are compared: activated charcoal, silver-coated sea sand and gold-coated sea sand. To eliminate interferences, a two-step desorption unit is used. After thermal desorption, the mercury is measured by using a modified MAS-50 spectrophotometer. The effects of flow rate and desorption temperature are discussed. The detection limit is 0.1 ng. Above 1 ng, the reproducibility is about 1%. Calibration is done by injection of elemental mercury vapour. The method with gold-coated sand absorbers is most satisfactory and is suitable for the analysis of ambient outdoor and indoor air. All likely volatile mercury compounds are absorbed, and a wide range of mercury concentrations can be determined. In routine application, one analysis takes about 3 min.

Study of excited fragment emission from the electron impact dissociation of volatile mercury(II) halides

Emission resulting, from collisions of 5–200 eV electrons with gaseous H gX 2, and CH 3H gX (X = Cl, Br. I) was characterized in the 3800–5600 A region. HgX BX emission dominates and absolute cross section as a function of electron energy were determined. The formation of electronically excited Hg atoms, and the trend of the cross sections with the nature of the halogen atom are discussed in terms of a simple charge transfer model.

The role of hydrogen sulphide in environmental transport of mercury

HYDROGEN SULPHIDE may be evolved in anoxic sulphur-containing river or lake sediments1. The effect of the presence of sulphide on the availability of inorganic mercury for biological methylation has been considered previously. Essentially mercury in the form of Hg(0) or Hg(II) may be converted into mercuric sulphide in anoxic sediments2. It might seem that this very insoluble material would not, in practice, be available for methylation and that sulphide formation would act as a method of removing mercury from availability to the general environment (that is, it would act as a mercury sink). However in a complex natural system (aquarium sediment) it has been shown that HgS may, in fact, be methylated in the sediments although to produce quantities of methyl mercury substantially less than those produced using a more soluble mercury substrate2. Therefore, although H2S in a sediment would be expected to reduce the rate of mercury methylation considerably by the formation of HgS, it would not be expected to prevent formation of methyl mercury entirely. The effect of H2S on methyl mercury itself has also been investigated using a purely inorganic model3. An aqueous solution of methyl mercuric chloride (1 mg dm−3) loses methyl mercury steadily over 3 days after initial exposure to H2S. A volatile product was evolved into the space above the solution. This product was trapped in a sodium carbonate–disodium phosphate solution, extracted with toluene and shown to co-migrate with methyl mercury on thin layer plates of silica gel. It was concluded that the evolved product of the reaction system was a volatile organo-sulphur derivative of mercury that reverted to methyl mercury on extraction. These observations suggest that reaction between methyl mercury and H2S generated in sediments reduces the amount of methyl mercury available for accumulation by fish and shellfish and represents a powerful mechanism adding to the general mobility of mercury compounds in the environment. It is therefore important to identify the unknown mercury compound evolved from the system described above. We have now investigated the interaction of H2S with River Mersey (England) inter-tidal estuary sediment samples in order to determine its effect on methyl mercury levels in real systems. We have also investigated similar reactions in a model system, leading to the identification of the previously unknown volatile mercury species responsible for the transport of mercury in the work of Rowland et al.3

Gaseous emissions of mercury from an aquatic vascular plant

RECENT studies have demonstrated the emission of mercury to the atmosphere from a variety of sources including contaminated industrial waste beds1–4. Investigations have also shown that vascular plants can take up both inorganic and organic mercury compounds through their root systems and transport them to the leaves5,6. Separate measurements of mercury emanations from the excised leaves of three vascular plant species have shown that there is a release of volatile mercury at room temperatures7. Thus, it would seem that vascular plants have the potential to take up mercury from a substrate, to transport it, and to emit it to the surrounding atmosphere through their leaves. However, no direct measurements of such emissions from living intact plants have been reported. We report here our examination of the common reed, Phragmites communis, growing along the shoreline of a mercury-contaminated lake and our finding that these plants, growing in their natural environment, actively release mercury to the atmosphere.

Metabolic studies of Hg-203 on Chlamydomonas reinhardi.

Sterile cultures of Chlamydomonas reinhardi, WT+, were treated with Hg-203 at 25 degrees C to identify probably formed volatile mercury compounds. Experiments were performed with living and dead cells under aerobic or anaerobic conditions, respectively, and the mercury concentration was measured in the system algae/nutrient medium. We found a timerelated decrease of mercury concentration in the cell suspension and the cell-free nutrient medium due to a reduction of Hg++ to Hg0, probably caused by extracellular enzymes; monomethyl or dimethyl mercury could not be detected.

Mercury Emissions from Geothermal Power Plants

Geothermal steam used for power production contains significant quantities of volatile mercury. Much of this mercury escapes to the atmosphere as elemental mercury vapor in cooling tower exhausts. Mercury emissions from geothermal power plants, on a per megawatt (electric) basis, are comparable to releases from coal-fired power plants.

Investigations on the simultaneous uptake and release of mercury by Dunaliella tertiolecta

By using two different radioactive mercury isotopes, detailed information was obtained on the uptake and simultaneous release of mercury by Dunaliella tertiolecta. Hg-203 was added to a well-aged culture, which 2 days later was separated from the medium, washed and cultivated again in a fresh medium containing Hg-197. It was found that an exchange of mercury takes place between the cells and the medium. An increase in the concentration of volatile mercury occurs simultaneously with the maximum concentration of chlorophyll a. Comparing the culture solutions with the blanks, the dissolved mercury shows similar volatility. This leads to the assumption that the main part of the dissolved mercury in the culture solutions is in the inorganic state.

Distribution of atmospheric mercury species near ground

A recently developed technique makes possible the routine analysis of atmospheric samples for particulate and volatile mercury. The volatile fraction can be analyzed for several chemical species. This work presents the results of some Tampb Bay area analyses and diurnal studies of atmospheric mercury speciation. The mercury in air in the area investigated was primarily volatile (>90%) and was composed of significant proportions of mercury (II)-type compounds, methylmercury (II)-type compounds, and elemental mercury. Dimethylmercury was rarely observed. Results were quite variable suggesting a variety of sources and irregular wind transport processes. The data indicate that background mercury concentrations and the percentage distribution of mercury species in air in a local area may be established by mercury emanations from the ground or from adjacent bodies of water.

Release of Volatile Mercury from Vascular Plants

AbstractVolatile, organic solvent soluble mercury has been found in leaves and seeds of several angiosperms. Leaves of garlic vine (Pseudocallyma alliacium), avocado (Persea americana) and haole‐koa (Leucaena glauca) release mercury in volatile form rapidly at room temperature. In garlic vine, the most active release is temperature dependent, but does not parallel the vaporpressure temperature relationship for mercury. Mercury can be trapped in nitric‐perchloric acid digestion fluid, or n‐hexane, but is lost from the hexane unless the acid mixture is present. Seeds of haole‐koa also contain extractable mercury but volatility declines in the series n‐hexane (90%) > methanol (50%) > water (10%). This suggests that reduced volatility may accompany solvolysis in the more polar media. Gas chromatographic analysis shows that the volatile compound is not dimethyl mercury.

THE EXCRETION OF VOLATILE MERCURY BY RATS INJECTED WITH MERCURIC SALTS.

When mercuric salts are injected into rats, volatile mercury is excreted, in part from the lungs and in part from the body surface. The amount of such excretion is small, averaging about 4 per cent of the total excretion. In the first hours after injection, when the blood levels are high, excretion from the lungs is high, but thereafter, the excretion is about equally divided between the lungs and the body surface. The rate of volatilization falls more rapidly than the total body burden of mercury, parallel to the drop in levels of the metal in the blood and skin.

VOLATILIZATION OF MERCURY BY BACTERIA.

Volatilization of mercury has been observed from various biological media (tissue homogenates, infusion broth, plasma, urine) containing mercuric chloride. That micro-organisms were responsible was indicated by the finding that the rates of volatilization were highly variable, that a latent period often preceded volatilization, that toluene inhibited the process, and that the capacity to volatilize mercury could be transferred from one biological medium to another. Two species of bacteria when isolated and cultured from these homogenates were able to volatilize mercury. Two other bacteria, one of which was isolated from the local water supply, were also highly active. The volatile mercury was identified as mercury vapour. The importance of these findings in relation to the storage of urine samples prior to mercury analysis is discussed.

SOME FACTORS AFFECTING THE DISPERSAL OF LIQUID SEED DRESSINGS AMONG CEREAL SEEDS

A survey of Manitoba seed-treatment practices carried on in 1961 showed that the volatile organic mercury liquid seed dressing Panogen 15 was widely used for seed treatment and that it was frequently applied to seed by means of a "drip" apparatus coupled to an auger-type grain-loader. An attempt was made to measure the efficiency of such equipment for the treatment of barley seed, especially the effect of varying the auger length, diameter and slope, and the rate of grain flow through it. However, when the treated grain collected at different "settings" of the equipment was tested for uniformity of treatment, it was found that changes in auger setting had no visible effect on the machine's performance as a seed treater. Other tests indicated that Panogen 15 spreads more readily from treated to untreated barley seed than it does in oats or wheat, especially when the temperature is about 70°F. Because of the rapid spread of this fungicide, treated barley seed that has been stored for some time before being tested for uniformity of seed treatment cannot be expected to show the efficiency of the grain-loader as a seed treater. Another seed dressing tested is less volatile than Panogen 15, but it spreads very readily at room temperatures, by contact of untreated seed with treated seed. Laboratory tests showed also that liquid seed dressings may disperse by contact uniformly, even when the grain is cold, providing the grain and dressing are thoroughly mixed.