首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
Experimental results from a study of the gas and aqueous phase reactions of elemental mercury (Hg0) with methyl iodide (CH3I) and dimethyl sulfide (DMS) are presented. In aqueous phase experiments with CH3I we found no observable increase in methyl mercury (MeHg). A small formation of MeHg, however, was observed in some (but not all) gas phase experiments in sunlight. A loss of Hg0 and a simultaneous formation of oxidized mercury (Hg(II)) was also observed in these experiments. No reaction, neither methylation or oxidation, was found between Hg0 and DMS under any conditions investigated. These experiments suggest that a simple homogeneous gas or aqueous phase methylation of Hg0 by DMS or CH3I in the atmosphere cannot account for the significant levels of MeHg observed in precipitation.  相似文献   

2.
When balancing the element mercury (Hg) two coal-fired power plant units — one with slag tap boilers (ST, 2 × 220 MW) and one with a dry bottom boiler (DB, 475 MW) were compared. Both systems are provided with electrostatic precipitators (ESP), nitrogen oxides removal (DeNOx) and flue gas desulfurization (FGD) systems. The Hg in the flue gas is predominantly in gas phase. Only 15 % of the Hg introduced by the coal leaves the unit with the bottom or fly ash. Depending on the operating mode, 30 to 40 % of the Hg is separated in the FGD systems. The overall separation rate for the total system ranges between 45 to 55 %, the residue is emitted in the form of gaseous Hg species. At full load, the Hg concentration in the cleaned gas is less than 6 μg/m3. In the flue gas path of another dry bottom boiler (DB1, 480 MW) the concentrations of the gaseous species of bivalent mercury (Hg2+), elemental mercury (Hg0), and total mercury content (Σ Hg) were determined. The sum of the concentrations of Hg2+ and Hg0 is in agreement with the measurement of Σ Hg. Directly downstream of the boiler Hg2+ dominates with 77 %, while Hg0 amounts to 23 %. In the high-dust DeNOx system Hg0 is oxidized almost completely to Hg2+ (96 %). Air heater and electrostatic precipitator do not influence the Hg species concentrations. The FGD system eliminates approximately 80 % of the Hg2+. At the same time the quantity of Hg0 increases by the factor 10. In the cleaned gas Hg0 dominates with 76 % as compared to Hg2+ with 24 %. At full load the concentration of Σ Hg in the cleaned gas is also below 6 μg/m3.  相似文献   

3.
Most technologies used for decontamination presents good results for high concentrations, but limitations for lower ones. The desirable Hg concentration in the water is extremely low because of its toxicity. The aims of this study were to evaluate inorganic mercury (Hg2+) and methylmercury (CH3Hg+) toxicity in Nostoc paludosum, to assess the potential of this cyanobacteria strain to remove these Hg species from aqueous medium and also to investigate Hg methylation by the cyanobacteria. CH3Hg+ determination was performed by gas chromatography-pyrolysis-atomic fluorescence spectrometry in cultures exposed to a concentration of 20 μg L?1 for 30 days. Both Hg species were removed from the supernatant, ranging from 73 to 96% of Hg2+ and from 73 to 95% of CH3Hg+. Ultrastructural Hg2+ effects in the cyanobacteria cells investigated by transmission electron microscopy revealed higher production of glycogen, cyanophycin, and intrathylacoidal spaces than the control group. When Hg was added to the culture in the form of CH3Hg+, a decrease corresponding to approximately 60% of the initial concentration due to Hg volatilization was observed. The production of CH3Hg+ by the cyanobacteria was detected in concentrations near the limit of detection (0.0025%) of the bioaccumulated THg. This is an advantage for biotechnological decontamination applications, as CH3Hg+ is a very toxic specie and can be bioaccumulated and biomagnified. The results demonstrated that cyanobacteria cells are an efficient alternative to retain and/or remove Hg at low concentrations and they constitute a potential tool for a “final cleaning” of contaminated waste water.  相似文献   

4.
Chemical speciation of mercury (Hg) in a wide variety of combustion flue gas matrices has been determined using the mercury speciation adsorption (MESA) method. The MESA sampling system for gas phase Hg species employs a series of heated, solid phase adsorbent traps. Flue gas oxidized Hg species (Hg(II) and MMHg) are adsorbed by a potassium chloride (KCl) impregnated soda lime sorbent. Elemental Hg (Hg0) is collected by an iodated carbon sorbent after passing through the KCl/soda lime sorbent. Total Hg (Hgt) is determined by summation of species. In the laboratory, cold vapor atomic fluorescence spectroscopy (CVAFS) is used for detection of Hg collected on the solid sorbents, after appropriate sample digestion and preparation. The MESA method has been evaluated for species stability, matrix effects, breakthrough, artifacts and precision. Based on eight duplicate samples a mean precision of 6.8% 11% and 4.5% (relative percent difference) has been calculated for Hg0, Hg(II) and Hgt respectively. Intercomparison of the MESA method with other methods shows very good agreement for Hgt. Mass balance calculations at 5 sites range from 75 to 140%, with a mean of 97±25%. Overall mean speciation results from 19 separate determinations suggest that Hg(II) has a 1 sigma range of 40 to 94% in coal combustion flue gas at, the inlet to pollution control devices.  相似文献   

5.
Spectroscopic (XRD, XPS, ICP-MS and AAS) and microscopic (ESEM) techniques have been used in order to study the chemical effects with emphasis on mercury speciation, during thermal treatment of a mercury contaminated soil. In the untreated soil, mercury was found concentrated in spherical particles, which were successively broken down upon thermal treatment. Hg0 and inorganic mercury compounds (presumably HgO(s) and HgSO4(s)) could be detected. No (CH3)2Hg and only traces of CH3Hg+ could be found. The dependence on temperature and heating time indicated that the evaporation of mercury from the soil was partly controlled by diffusion mechanisms. Mercury volatilized in two separate stages during heating; initial elemental vaporization, and subsequent volatilization of the oxide or sulfate phase at higher temperatures (>230°C). By thermal treatment at 470°C and 20 min, a removal of >99% of the mercury could be achieved.  相似文献   

6.
New experiments have been conducted to determine the speciation of dissolved mercury (Hg) over wide pH (1–12) and sulfide concentration ranges (0.5–30 mM) and in the presence of elemental sulfur (S0) or Hg0, conditions that encompass those of near-bottom and pore waters of sediments. Samples containing synthetic red mercuric sulfide (HgS, cinnabar), buffer solution, aliquots of bisulfide (HS?1) solution, and, in special cases, S0 or Hg0 were prepared anaerobically and allowed to equilibrate for several months. Filtered samples were analyzed for pH, total sulfide (ΣS2?), and total mercury [Hg]tot. Plots of [Hg]tot values vs. pH at varying ΣS2? verified the formation of three previously known mercury-sulfide complexes (HgS2Hn n?2) and revealed that a new Hg2SOH+ complex is important at low pH and low ΣS2?. Our constants for ionic strength (I) 0.7 and 250 C are as follows: K1=10?5.76(+0.71, ?1.02) for HgScinn+H2S ? HgS2H2 0; K2=10?4.82(+0.72, ?1.10) for HgScinn+HS? ? HgS2H?; K3=10?13.41(+0.76, ?0.93) for HgScinn+HS? ? HgS2 2?+H+; K4=10?8.36(+0.71, ?0.93) for 2HgScinn+H++H2O ? Hg2SOH++H2S. With decreasing pH, below 1, Hg solubility decreased sharply, indicating the formation of a new solid phase, inferred to be corderoite (Hg3S2Cl2). From our solubility data, we calculated the free energy of formation (ΔGf o) of Hg3S2Cl2 to be ?396 (+3, ?11) kJ/mol. In experiments where excess S0(s) was present, a new mercury-polysulfide dimer was identified; its formation constant is K5=10?1.99(+0.69, ?1.27) for 2HgScinn+2HS? + nS0 ? Hg3S4 IISn oH2 2?. Data from experiments where Hg0(aq) was added confirmed the reversibility of HgS dissolution. An application of our mercury-sulfide speciation model to a natural anoxic basin, Saanich Inlet, British Columbia, is discussed.  相似文献   

7.
Ewert  G.  Paulsen  T.  Linscheid  M. 《Water, air, and soil pollution》2003,144(1-4):141-148
Hearth furnace coke (HOK), a special type of lignite (brown-coal)coke produced in a manufacturing process called `hearth furnace process', and portlandite (Ca(OH)2) particles were placed ina circulating fluidized bed reactor. Defined model waste gases containing HCl/SO2/Hg0/Hg2+ and organic compounds were injected into the reactor to investigate the adsorption of different mercury species. Elemental mercuryreacted immediately with HCl to form HgCl2, but for Hg2+ further investigations had to be made, because todaygas cleaning plants still have problems in observing national limits for the mercury output. The temperature, the mercury content of the gas, and its content of acid compounds as majorinfluences in cleaning exhaust gases were varied without relevantpositive effects on the adsorption rate which decreased from nearly 100% in the first five minutes to unsatisfactory20% some minutes later. The mercury load on the HOK particles onlyshowed a value of 60 μg Hg g-1 HOK. Then organic compounds (guide pollutants such as 1-chlorobutane, monochlorobenzene, toluene, and naphthalene, which are alwayspresent in incineration plant exhaust gases) were added to thegas stream and the results improved significantly. The mercuryload on the HOK particles varied depending on the chemical nature of the organic compound and amounted to 300 μg Hg g-1 HOK maximum. The measured values of mercury in the clean gas stream fell below 10 μg m-3. The characterization of the dynamic behavior of mercury in hot, acid waste gases and the analytical identification of mercurysticking to HOK under the influence of organic compounds leadto new methods for improving the effectiveness and performanceof gas cleaning plants.  相似文献   

8.
Divalent Hg is reduced by sulfite in aqueous solutions. The proposed mechanism involves the formation of an instable intermediate, HgSO3, which decomposes to produce Hg+ which in turn is rapidly reduced to Hg0. The overall rate of the reaction is inversely dependent on the concentration of sulfite. This reaction may influence the concentration of Hg in cloud- and rain-water by reducing water soluble Hg2+ to volatile Hg0. At low concentrations of SO2(g) (5 μg m−3, 25 °C), the rate of the conversion of Hg(SO3)2 2− to Hg0 becomes significant (> 1 % h−1) at pH < 5.5. At higher S02 concentrations (500 pg m−3), the same rate is expected at pH < 4.5.  相似文献   

9.
Source-oriented models are ideally suited to examine the impact of terrain and meteorology and source factors such as stack height when evaluating exposures to air pollutants. A source-oriented, Gaussian plume air pollution dispersion model AERMOD was used to estimate the spatial distribution of elemental mercury (Hg0) from a typical coal-fired boiler emitting 0.001 g Hg0/s. Hg0 was chosen because of its health impact related to potential neurological and reproductive effects which may be especially important for high-risk populations. Results from four simulations using meteorological data from 2004 were compared for flat and hilly terrain from 20- and 55-m stacks at a distance of 1,350 m from the source. Variations within a quadrant were affected primarily by topography. For the 20-m stack, the average annual ambient concentration for individuals living within the northeast (NE) quadrant was significantly lower at 2.5 ng Hg0/m3 (P?<?0.001; confidence interval (CI), 2.4?C2.6) in flat terrain versus 3.3 ng Hg0/m3 in hilly (P?<?0.001; CI, 1.2?C1.3). NE concentrations of the source showed high spatial variability attributed to topography with 1-h maximums of 4.0 ng Hg0/m3 flat versus 7.1 ng Hg0/m3 hilly. Not unexpectedly, average annual concentrations were considerably lower for the 55-m stack although topography remained a significant variable with 0.1 ng Hg0/m3 in flat terrain (p?<?0.001; CI, 0.11?C0.13) and double that exposure at 0.2 ng Hg0/m3 in hilly terrain (p?<?0.001; CI, 0.16?C0.18). Annual average mercury concentrations due to emissions from the 20-m stack were ~20 times higher than ambient concentrations associated with the 55-m stack. A sensitivity analysis was performed for meteorological effects, using meteorological data from years 2001?C2005. Varying the roughness factor had no significant effect on the results. For all simulations, the highest concentrations were located in the NE quadrant. During 2001?C2005, the highest average annual ambient Hg concentration ranged from 6.2 to 7.0 ng Hg0/m3 for the 20-m stack and 0.3?C0.5 ng Hg0/m3 for the 55-m stack. Thus, this model is robust. These results demonstrate the usefulness of a source-oriented model such as AERMOD for incorporating multiple factors for estimating air pollution exposures for communities near point sources. The importance of considering topography, meteorology, and source characteristics when placing air samplers to measure air quality and when using buffer zones to estimate ambient residential exposures is also illustrated. Residential communities in hilly terrain near industrial point sources may have between two to three times the exposures as those in flat terrain. Exposures will vary depending on the stack height of the point source.  相似文献   

10.
Methylation of Hg2+ (Hg(NO3)2) in the presence of fulvic acid (FA) and various metal ions has been studied. The concentrations of Hg2+ and FA ranged from 5 to 20 mg L?1 and 171 to 285 mg L?1 DOC, respectively. The pH range was 3 to 6.5. FA was isolated from an acid brown-water lake by XAD-8 polymeric adsorbent. Methylmercury production in the dark during 2 to 4 days incubation at 30 °C increased with increasing concentrations of Hg2+ ion and FA as well as with additions of metal ions (5 to 10 × 10?5 mole L?1 The observed catalytic activity of metal ions followed the order Fe3+ (Fe2+) > Cu2+ ≈ Mn2+, > Al3+. The production of methylmercury had a pH-optimum around 4 to 4.5 at the conditions tested.  相似文献   

11.
In this study, we evaluated the relative contribution of atmospheric particulate mercury (Hg(p)) and divalent reactive gaseous mercury (RGM) to mercury dry deposition in Japan. The dry deposition fluxes (on a water surface sampler) and atmospheric PM concentrations of Hg, Cd, Cu, Mn, Ni, Pb and V, which were measured concurrently from April 2004 to March 2006 at 10 sites across the nation, were used in this evaluation. We considered that Hg(p) and RGM, but not Hg0, are deposited on the water surface, and that our method of sampling Hg(p) without the use of KCl-coated annular denuders enables the exclusion of a significant amount of RGM artifact. The monthly average dry deposition velocities (= deposition flux/atmospheric PM concentration) of Cd and Pb were found to be similar to each other (Cd/Pb deposition velocities?=?1.06?±?0.58). It was assumed that the deposition velocity of Hg(p) is identical to the mean deposition velocity of Cd and Pb, because the particle size distribution of Hg(p) is likely similar to those of both elements. Using this deposition velocity, the monthly dry deposition flux of Hg(p) was calculated. The average contribution (±1σ) of Hg(p) to the annual deposition flux at ten sites was 26?±?15%. The mercury dry deposition flux increased generally from spring to early summer, which was attributed mostly to the deposition of RGM. This seasonal change correlated to that in photochemical oxidant (primarily O3) concentration in air at most sites. These suggest that mercury dry deposition in Japan is predominantly deposition of RGM, which was formed via oxidation of Hg0 by O3 in the atmosphere.  相似文献   

12.
Dissolved and particulate Hg speciation was determined on four occasions in the Spring to Fall interval of 1989, at three depths of the water column of Onondaga Lake, New York; an urban system in which the sediments and fish flesh are contaminated with Hg. Species determined included total Hg (Hgt), reactive (‘ionic’) Hg (Hgi), monomethylmercury (CH3HgX), elemental Hg (Hg°) and dimethylmercury (CH3)2Hg). Onondaga Lake was found to contain very high levels of Hgt (2 to 25 ng L?1 Hg), Hgj (0.5 to 10 ng L?1 Hg), and CH3HgX (0.3 to 7 ng L?1 Hg), which generally increased with depth in the lake. These concentrations represent a significant level of contamination, based upon comparisons with other polluted and pristine sites. Elemental Hg levels were typically about 0.05 ng L?1 and (CH3)2Hg was near the limits of detection (?0.001 ng) L?1 in most samples. The greatest CH3HgX concentrations in the hypolimnion, as well as the largest gradients of both CH3HgX and (Hgt), were observed upon the first onset of stratification, in early summer. These concentrations did not become more pronounced, however, as stratification and H2S levels in the hypolimnion increased throughout the summer. The very low concentrations of (CH3)2Hg in these MeHg and sulfide-rich waters calls into question the belief that CH3HgX and H2S will react to yield volatile dimethyl-mercury, which can then escape to the atmosphere by diffusion. Mercury speciation was highly dynamic, indicating active cycling within the lake, and an apparent sensitivity to changes in attendant Iimnological conditions that track the stratification cycle.  相似文献   

13.
An intensive survey of mercury speciation was performed at a site on the Upper St. Lawrence River near Cornwall, Ontario, Canada with a history mercury contamination in sediments. Surface sediments were collected every 1.50 h. Total mercury (Hgtotal), methylmercury (MeHg), organic carbon, inorganic and organic sulphur were determined in the solid fraction. Dissolved Hgtotal, MeHg and dissolved organic carbon (DOC) were measured in pore waters. Concentrations of Hgtotal in the upper layers (first 5 cm) were high, ranging from 1.42 to 25.8 nmol g?1 in solids and from 125 to 449 pM in pore waters. MeHg levels were also high, ranging from 4.34 to 34.1 pmol g?1 in solids and from 40 to 96 pM in pore waters. This amounts to up to 1.4% of Hgtotal present as MeHg in solids and 64% in pore waters. A daily pattern for Hgtotal was observed in the solid fraction. The MeHg distribution in solids and pore waters was not correlated with Hgtotal or DOC, suggesting that the concentrations of MeHg are probably more influenced by the relative rates of methylation/demethylation reactions in the sediment–water interface. Acid volatile sulphide levels and DOC were inversely correlated with organic sulphur (Sorg) levels suggesting that both parameters are involved in the rapid production of Sorg. A positive correlation was also observed between Hgtotal and Sorg in solids (R?=?0.87, p?<?0.01) illustrating the importance of organic sulphur in the retention and distribution of Hg in the solid fraction of the sediments. The results suggest that variations of Hgtotal concentrations in Upper St. Lawrence River surface sediments were strongly influenced by the formation/deposition/retention of organic sulphur compounds in the sediment–water interface.  相似文献   

14.
As global mercury emissions from coal fire power plants increase with the continuing rise of coal consumption, mercury capture methods are being developed to prevent mercury??s escape into the atmosphere. Titanium dioxide (TiO2) in the presence of ultra violet light (UV-A; ?? max ??360?nm) and oxygen will capture mercury as the solid product HgO(s). Testing the effects of TiO2 in the presence of other pollutants has so far been limited. We have performed kinetic and product studies of mercury adsorption in the presence of the gaseous flue co-pollutant NO2(g). We extensively studied the gas-phase reaction of NO2(g) with Hg (g) 0 . We compared the gas-phase reaction to the same reaction performed in the presence of thin TiO2 particle surfaces from 0 to 100?% relative humidity. The second-order rate constant was measured to be k?=?(3.5?±?0.5)?×?10?35?cm6 molecules?2?s?1, independent of the presence of titania or the total surface area available for adsorption. Exposure of NO2(g) to titania surfaces that were already saturated in captured mercury (HgO(s)) increased total mercury uptake onto the surface. We discuss the implications of this study to the capture of mercury emissions prior to release to the atmosphere.  相似文献   

15.
The spatial and temporal distribution of elemental Hg (Hg°) and reactive Hg (HgR) has been studied on Pallette Lake, Wisconsin during May – August, 1993 and May, 1994. In general, Hg° concentrations near the lake surface greatly exceeded saturation with respect to atmospheric Hg° indicating a flux out (?) of the lake. Evasional losses were estimated using a thin film model and averaged ?101 pmol m?2 d?1 during July and August, 1993. A large portion of atmospherically deposited Hg is re-emitted. Thus, in-lake Hg° production' and evasion to the atmosphere will significantly reduce the amount of Hg which is transported to the sediments, the principal site of methylation. Laboratory experiments were conducted to ascertain the rate of Hg° formation from Hg(II). Reduction was significantly lower in heat sterilized lakewater suggesting Hg° production was biologically mediated. The temporal distribution of epilimnetic Hg°, as measured at the lake center, was influenced by Hg° evasion, Hg° production and advective transport of water parcels of differing Hg content. Spatial gradients in Hg° and HgR were identified and a transport model was employed to estimate the advective flux of Hg°. The importance of atmospheric deposition and sediment-water interaction as sources of HgR to epilimnetic waters were examined. Porewater concentrations of Hg° and HgR were determined on several occasions. During May, 1994, the depletion of lakewater HgR following a input pulse due to rain was observed and the estimated removal rate (16–20% d?1) agrees well with reduction rates obtained in the laboratory (23% d?1).  相似文献   

16.

Purpose

Soil-plant transfer models are needed to predict levels of mercury (Hg) in vegetables when evaluating food chain risks of Hg contamination in agricultural soils.

Materials and methods

A total of 21 soils covering a wide range of soil properties were spiked with HgCl2 to investigate the transfer characteristics of Hg from soil to carrot in a greenhouse experiment. The major controlling factors and prediction models were identified and developed using path analysis and stepwise multiple linear regression analysis.

Results and discussion

Carrot Hg concentration was positively correlated with soil total Hg concentration (R 2?=?0.54, P?<?0.001), and the log-transformation greatly improved the correlation (R 2?=?0.76, P?<?0.001). Acidic soil exhibited the highest bioconcentration factor (BCF) (ratio of Hg concentration in carrot to that in soil), while calcareous soil showed the lowest BCF among the 21 soil types. The significant direct effects of soil total Hg (Hgsoil), pH, and free Al oxide (AlOX) on the carrot Hg concentration (Hgcarrot) as revealed by path analysis were consistent with the result from stepwise multiple linear regression that yielded a three-term regression model: log [Hgcarrot]?=?0.52log [Hgsoil]???0.06pH???0.64log [AlOX]???1.05 (R 2?=?0.81, P?<?0.001).

Conclusions

Soil Hg concentration, pH, and AlOX content were the three most important variables associated with carrot Hg concentration. The extended Freundlich-type function could well describe Hg transfer from soil to carrot.  相似文献   

17.
The Hg concentrations in coal as fired in power plants in the Netherlands are low, 0.2 mg·kg?1 on average. After combustion the Hg is released partly (between 1 and 98%, on average 42%) in a gaseous phase, which is finally emitted into the air. The other part of the Hg, which remains in the ash is separated from the flue gases by electrostatic precipitators. The variation of the vaporisation percentage of Hg is probably caused by the presence of two chemical forms: Hgo and HgCl2. This may be concluded from the observation that relatively high concentrations of HCl in the flue gases (≈150 mg·m?3) give rise to low Hg concentration in the vapor phase. In cases when the concentrations of HCl are relatively low (≈25 mg·m?3) the amount of Hg in the vapor phase is high. The average gas phase concentrations of Hg in the flue gases, based on 33 measurements with no FGD, is 4.1 μg·mfo ?3. In a wet FGD based on the lime/limestone-gypsum process 50 to 70% of the Hg in the flue gases is removed, leaving a residual concentration of 1–2 μg·mfo ?3. The emission factor is then about 0.5 mg·GJ?1 or 5 μg·kWhr?1. In one particular measuring serie the fate of Hg was studied in a FGD-installation with a prescrubber.  相似文献   

18.

Purpose

Middle-European floodplain soils are often contaminated with mercury (Hg) and periodically flooded. In this study, the influence of a flooding event and subsequent dewatering on the volatilization of elemental Hg and methylated species was investigated in a laboratory experiment.

Material and methods

Undisturbed soil cores were taken from a topsoil (12.1?±?0.75 mg kg?1 Hg) at the Elbe River in Lower Saxony, Germany. Soil columns were incubated at 20 °C with varying soil moisture (water-saturated for 2 weeks, 95 and 90 % water content for 1 week each), and the redox potential (EH) was recorded. The gaseous Hg that accumulated in the headspace of the flux chamber of the columns was pumped over cooled traps filled with adsorber material and analyzed by gas chromatography/inductively coupled plasma mass spectrometry for the various Hg species.

Results and discussion

The watering of the soil resulted in a rapid decrease in the EH and the achievement of strongly reducing conditions (EH??1 Hg at the beginning to 5.78 μg L?1 Hg at the end of the experiment. Species analyses revealed that exclusively elemental Hg volatilized. The volatilization rate was between 1.73 and 824 ng m?2 h?1 Hg, which is consistent with other studies at the Elbe River.

Conclusions

Even when flooded for a longer period of time, floodplain soils should show neither emission of methylated Hg nor exceptionally high volatilization of elemental Hg.  相似文献   

19.
Mercury fallout was measured 10 m from the selected emission site, the Sulfur Banks fumarole area, Hawaii Volcanoes National Park; at stations on Maui and Oahu, respectively 200 km and 380 km distant from the Sulfur Banks; and at the Hawaii Geothermal Project drill site, only 40 km from source. Sulfur Banks and Oahu measurements were carried out on six occasions between 1972 and 1976, each time within the same 24 h period. Gold foil was used for collection of elemental mercury (Hg°) and copper foil for both oxidized (Hgox) and elemental forms. The rate of deposition at the Sulfur Banks was high ? 800 μm m?2 day?1, or 300 kgkm?2 annually. The same figure applied to the relatively nearby geothermal project site. At both remote stations the fallout rate was approximately 10 fold lower. At four measurement times out of six the ratio HgO/Hgox ranged from 0.195 to 0.463 at the Sulfur Banks source and from 1.80 to 5.15 at the remote stations. On two occasions, heavy rains selectively reduced Hgox at the emission site. Model calculations compared Sulfur Banks fallout with rates of re-emission of Hg by vegetation, and the importance of the biotic factor in determination of mass balances and fluxes was emphasized. Aspects of the geochemistry and toxicology of Hg were considered briefly in relation to emission and deposition, and to the occurrence of Hg°.  相似文献   

20.
The distribution of mercury species was determined in soil from a site with Hg contamination. Mercury contamination was primarily confined to the top 40 cm of soil, and the concentration of total Hg ranged from 0.5 to 3000 µg Hg g?1. Of total Hg present, we determined that 91% was inorganic, 0.01% organic (as methyl Hg), and 6% elemental Hg. Furthermore, of total inorganic Hg present, 85% was in the insoluble mercuric sulfide form. Thus, of total Hg present in soil at this contaminated site, 91% was in the relatively insoluble HgS and Hg0 forms.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号