Hg Ratio Research Articles

Material synthesis of HgBa2Can-1CunOy multilayered cuprates under high pressure

Multilayered cuprates having crystallographically inequivalent CuO2 planes are worthful materials to realize the mechanism of high-Tc superconductivity as well as a stage to ascertain new phenomena. The material synthesis of HgBa2Can-1CunOy multilayered cuprates by employing high-pressure synthesis technique is demonstrated. A starting mixture with a composition ratio of Hg:Ba:Ca:Cu:O = 1:2:n-1:n:2n+2+δ was synthesized by mixing the precursor of Ba2Ca2Cu3Oy (y~7.5) with an appropriate amount of HgO, Ca2CuO3, CuO and Cu2O (or Cu). The oxygen content of the mixture was adjusted incisively by ascertaining a ratio of CuO, Cu2O (or Cu) to obtain samples. Almost single-phase samples up to n = 6 were synthesized. The X-ray diffraction analysis of the grain-aligned sample with nominal compositions of n ⩾ 7 revealed that the sample simultaneously comprises from n = 6 up to 16 phases.

Relationships among mercury, selenium, and neurochemical parameters in common loons (Gavia immer) and bald eagles (Haliaeetus leucocephalus)

Fish-eating birds can be exposed to levels of dietary methylmercury (MeHg) known or suspected to adversely affect normal behavior and reproduction, but little is known regarding Hg's subtle effects on the avian brain. In the current study, we explored relationships among Hg, Se, and neurochemical receptors and enzymes in two fish-eating birds--common loons (Gavia immer) and bald eagles (Haliaeetus leucocephalus). In liver, both species demonstrated a wide range of total Hg (THg) concentrations, substantial demethylation of MeHg, and a co-accumulation of Hg and Se. In liver, there were molar excesses of Se over Hg up to about 50-60 microg/g THg, above which there was an approximate 1:1 molar ratio of Hg:Se in both species. However, in brain, bald eagles displayed a greater apparent ability to demethylate MeHg than common loons. There were molar excesses of Se over Hg in brains of bald eagles across the full range of THg concentrations, whereas common loons often had extreme molar excesses of Hg in their brains, with a higher proportion of THg remaining as MeHg compared with eagles. There were significant positive correlations between brain THg and muscarinic cholinergic receptor concentrations in both species studied; whereas significant negative correlations were observed between N-methyl-D-aspartic acid (NMDA) receptor levels and brain Hg concentration. There were no significant correlations between brain Se and neurochemical receptors or enzymes (cholinesterase and monoamine oxidase) in either species. Our findings suggest that there are significant differences between common loons and bald eagles with respect to cerebral metabolism and toxicodynamics of MeHg and Se. These interspecies differences may influence relative susceptibility to MeHg toxicity; however, neurochemical responses to Hg in both species were similar.

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

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

Taguchi approach significantly increases bioremediation process efficiency: a case study with Hg (II) removal by Pseudomonas aeruginosa

Optimization of process parameters for mercury removal by an Hg (II)-reducing Pseudomonas aeruginosa strain. A strain of Ps. aeruginosa was found to reduce 10 mg l(-1) Hg (II) to Hg0 with 70% efficiency in 24 h. To optimize process performance, a statistical tool--Taguchi design of experiments (DOE)--was used to carry out 18 well-defined experiments (L18 Orthogonal array) with eight variable parameters (viz. agitation, temperature, pH, carbon source, medium volume: flask volume ratio and concentrations of Hg (II), ammonium sulfate and yeast extract). When data obtained were analyzed using specialized software for Taguchi design, Qualitek-4 (Nutek Inc., MI, USA), Hg (II) reduction efficiency was predicted to be 95% in 24 h under the optimized process parameters (also suggested by the software). In the validation experiment, Hg (II) removal of 99.29% in 24 h was indeed obtained. Using Taguchi DOE, Hg (II) reduction (and hence its removal) using Ps. aeruginosa could be improved by 29.3%. Taguchi approach could be employed as an efficient and time-saving strategy for parameter optimization in bioremediation processes.

High extraction ability of 1,3-dialkynyl calixarene towards mercury(II) ion

The reaction of 1,3-dipropyn-2-yloxycalix[4]arene with mercury(II) acetate could give mercury-containing alkynyl calixarene polymer. The extraction behavior of 1,3-dipropyn-2-yl-oxycalix[4]arene towards mercury(II) ion was examined. When the mole ratio of Hg 2+/calixarene was 1:1, the extractive percent can reach to 99.1%, and the extraction capacity was up to 431 mg/g. It could also decrease the Hg 2+ concentration from 5 to 0.85 mg/L, which was only 17% of the national standard of effluent and satisfied the national standard of drinking water. The extraction process included chemical reaction.

Fish Intake During Pregnancy and Mercury Level in Cord and Maternal Blood at Delivery: An Environmental Study in Poland

The purpose of this study was to estimate the amount of absorbed mercury (Hg) by mothers and their infants as a result of fish consumption during pregnancy. The cohort consisted of 313 mother-infant pairs recruited initially from ambulatory prenatal clinics in the first and second trimesters of pregnancy. The customary pattern of fish consumption during pregnancy reported by mothers was correlated with Hg levels in cord and maternal blood at delivery. Blood Hg level was measured using atomic absorption spectrometry. The mean Hg concentration in cord blood was markedly higher than in maternal blood at delivery (1.09 microg/L; 95%CI: 1.00-1.13 microg/L vs. 0.83 microg/L, 95%CI: 0.76-0.91 microg/L). There was significant correlation (r(s)=0.62, 95%CI: 0.55-0.69) between Hg levels in cord and maternal blood. The overall ratio of Hg in cord blood vs. maternal blood was 1.7 (95%C: 1.50-1.89). Fish consumed during the last pregnancy trimester correlated stronger with umbilical cord concentrations (r(s)=0.32; 95%CI: 0.22-0.40) than with Hg in maternal blood (r(s)=0.23; 95%CI: 0.14-0.33). The study shows that in Poland, babies are exposed to moderate levels of mercury prior to birth and that fish eating in pregnancy significantly contributes to prenatal Hg exposure. The findings also suggest that the level of cord blood Hg should not be used for describing inter-individual differences in maternal exposure to Hg unless a proper correction factor is introduced.

Mercury bioaccumulation in green frog (Rana clamitans) and bullfrog (Rana catesbeiana) tadpoles from Acadia National Park, Maine, USA

Mercury contamination in the northeastern United States, including Acadia National Park (ANP; ME, USA), is well documented and continues to be a public health issue of concern. Mercury contamination of wild amphibians has received little attention, however, despite reports of worldwide population declines. Here, we report total Hg and methyl Hg (MeHg) concentrations for water, sediment, and green frog (Rana clamitans) and bullfrog (Rana catesbeiana) tadpoles (age, approximately one year) from ANP. Total Hg concentrations (mean+/-standard error) in green frog and bullfrog tadpoles were 25.1+/-1.5 and 19.1+/-0.8 ng/g wet weight, respectively. Mean total Hg was highest for green frog tadpoles sampled from the Schooner Head site (ANP, Bar Harbor, ME, USA), a small, semipermanent beaver pond where Ranavirus was detected during the summer of 2003 sampling period. Methyl Hg comprised 7.6 to 40% of the total Hg in tadpole tissue (wet-wt basis), and mean total Hg levels in tadpoles were significantly different among pond sites (n = 9). Total Hg in pond water was a significant predictor of tadpole total Hg levels. Dissolved organic carbon was a significant predictor of both total Hg and MeHg in water, and total Hg in water also was strongly correlated with MeHg in water. Of the nine pond ecosystems sampled at ANP 44% had a methylation efficiency (water MeHg to total Hg ratio) of greater than 10%, and 33% had total Hg levels in sediment that were approximately equal to or greater than the established threshold level effect concentration for freshwater sediments (0.174 mg/kg dry wt). Our data indicate that wetland food webs in ANP likely are susceptible to high levels of total Hg bioaccumulation and that methylation dynamics appear to be influenced by local abiotic and biotic factors, including disturbances by beavers and in situ water chemistry patterns. These findings may be important to National Park Service resource managers, especially considering the class I airshed status of ANP and the strong potential for negative effects to aquatic ecosystem structure and function from Hg pollution.

Estimating contribution of precipitation scavenging of atmospheric particulate mercury to mercury wet deposition in Japan

Mercury wet deposition is dependent on both the scavenging of divalent reactive gaseous mercury (RGM) and atmospheric particulate mercury (Hg(p)) by precipitation. Estimating the contribution of precipitation scavenging of RGM and Hg(p) is important for better understanding the causes of the regional and seasonal variations in mercury wet deposition. In this study, the contribution of Hg(p) scavenging was estimated on the basis of the scavenging ratios of other trace elements (i.e., Cd, Cu, Mn, Ni, Pb and V) existing entirely in particulate form. Their wet deposition fluxes and concentrations in air, which were measured concurrently from April 2004 to March 2005 at 10 sites in Japan, were used in this estimation. The monthly wet deposition flux of mercury at each site correlated with the amount of monthly precipitation, whereas the Hg(p) concentrations in air tended to decrease during summer. There was a significant correlation ( P<0.001) among the calculated monthly average scavenging ratios of trace elements, and the values in each month at each site were similar. Therefore, it is assumed the monthly scavenging ratio of Hg(p) is equivalent to the mean value of other trace elements. Using this scavenging ratio ( W), the wet deposition flux ( F) due to Hg(p) scavenging in each month was calculated by F= WKP, where K and P are the Hg(p) concentration and amount of precipitation, respectively. Relatively large fluxes due to Hg(p) scavenging were observed at a highly industrial site and at sites on the Japan Sea coast, which are strongly affected by the local sources and the long-range transport from the Asian continent, respectively. However, on average, at the 10 sites, the contribution of Hg(p) scavenging to the annual mercury deposition flux was 26%, suggesting that mercury wet deposition in Japan is dominated by RGM scavenging. This RGM should originate mainly from the in situ oxidation of Hg 0 in the atmosphere.

Aqueous phase methylation as a potential source of methylmercury in wet deposition

The source of monomethylmercury (MMHg) in wet deposition is unknown. Volatilization of gaseous MMHg, evasion and demethylation of dimethylmercury, and methylation of Hg 0 have been either proposed or tested unsuccessfully as potential sources. Here, we show that MMHg in precipitation, sampled across a wide geographical range in North America, is related positively to an operationally defined and measured reactive Hg species (Hg R), but connected weakly to total Hg. The mean molar ratio of MMHg:Hg R measured in continental precipitation (0.025±0.006) is comparable to the MMHg:Hg(II) ratio estimated from first-order rate constants for acetate-mediated Hg methylation and MMHg photolysis (0.025±0.002). This suggests MMHg may be formed in the atmosphere through a reaction between labile Hg(II) complexes and an unknown methylating agent(s), potentially acetate or similar molecules. Availability of Hg(II) appears to limit the reaction, and accordingly, increased atmospheric loadings of Hg could lead to enhanced MMHg in precipitation.

Dynamic and static adsorption and desorption of Hg(II) ions on chitosan membranes and spheres

The adsorption and desorption of Hg(II) ions was studied using static and dynamic methods, employing membranes and spheres of chitosan as the adsorbent. The quantity of adsorption was influenced by chitosan crosslinking and by the adsorbent shape. The Langmuir model was applied to fit the experimental equilibrium data. Glutaraldehyde-crosslinked membranes presented a lower desorption capacity, when compared to natural membranes, but could be regenerated for use in successive cycles. Dynamic adsorption experiments suggested that the adsorption capacity depended mainly on adsorbent geometry, due to differences between surface area to mass ratio and initial concentration of Hg(II) ions. The adsorption capacity determined by the dynamic method was 65% and 77% for membranes and spheres, respectively of the value obtained static method results. A process combining dynamic adsorption and static desorption can be used to concentrate the Hg(II) ions by a factor of nearly seven (7×), when compared to the initially treated volume.

A New Method for Mercury Removal

A method is described for the removal of mercury from solution by using the off-gas produced from aerobic cultures of Klebsiella pneumoniae M426. Cells growing in Hg-supplemented medium produced a black precipitate containing mercury and sulphur. The ratio of Hg:S was determined as approximately 1:1 by analysis using proton-induced X-ray emission, suggesting precipitation of HgS within the culture. The outlet gases produced by a mercury-unsupplemented aerated culture were bubbled into an external chamber supplemented with up to 10 mg HgCl(2)/ml. A yellowish-white precipitate formed, corresponding to 99% removal of the mercury from solution within 120 min. Energy dispersive X-ray microanalysis showed that this metal precipitate consisted of mercury, carbon and sulphur. Formation of mercury carbonate was discounted since similar precipitation occurred at pH 2 and no oxygen was detected in the solid, which gave an X-ray powder pattern suggesting an amorphous material, with no evidence of HgS. Precipitation of mercury with a volatile organosulphur compound is suggested. Bio-precipitation of heavy metals by using culture off-gas is a useful approach because it can be used with concentrated or physiologically incompatible solutions. Since the metal precipitate is kept separate from the bacterial biomass, it can be managed independently.

Studies on spray-dried mixtures of chitosan and hydrolyzed gelatin as tablet binder: A technical note

The results of this investigation showed that spray drying of CH and HG resulted in free-flowing powder, which exhibited improved compressibility and compactibility, thereby suggesting the potential of such spray-dried mixtures of CH and HG as binder in tablets. Optimization of CH:HG ratio needs to be undertaken on a case basis, depending on the presence of other excipients in the formulation.

Relationship between abdominal fat and methionine deficiency in broilers

A study was conducted to determine the relationship between abdominal fat and the intake of methionine deficient diet in broilers. In this study, 66 male broilers at the age of 35 days were used. They were divided into two groups (control, n = 13, and methionine deficient group, n = 53) and all birds were housed in individual pens. During the experiment, normal and deficient diet contained 0.55% and 0.25% methionine, respectively. Control group was fed normal diet for 19 days. Treatment group received methionine deficient diet for 4 days and normal diet for 15 days. Body weight and feed intake were recorded daily. High (HG) and low (LG) groups were theoretically created according to the rates of decreases in individual feed intake. Percent decrease in feed intake of HG and LG groups was 29.4 &amp;plusmn; 2.0 and &amp;ndash;1.3 &amp;plusmn; 1.7, respectively. Abdominal fat in HG and LG groups amounted to 1.62 &amp;plusmn; 0.1 and 1.73 &amp;plusmn; 0.2%, respectively. The feed conversion ratio of HG and LG groups was 3.1 &amp;plusmn; 0.1 and 3.4&amp;nbsp;&amp;plusmn; 0.2, respectively. There was a negative correlation (&amp;ndash;0.45 in HG and &amp;ndash;0.43 in LG) between the percent decrease in feed intake and abdominal fat. &amp;nbsp;

Mercury Concentrations in Bicknell?s Thrush and Other Insectivorous Passerines in Montane Forests of Northeastern North America

Anthropogenic input of mercury (Hg) into the environment has elevated risk to fish and wildlife, particularly in northeastern North America. Investigations into the transfer and fate of Hg have focused on inhabitants of freshwater aquatic ecosystems, as these are the habitats at greatest risk for methylmercury (MeHg) biomagnification. Deviating from such an approach, we documented MeHg availability in a terrestrial montane ecosystem using a suite of insectivorous passerines. Intensive and extensive sampling of Bicknell's thrush (Catharus bicknelli) indicated significant heterogeneity in MeHg availability across 21 mountaintops in northeastern North America. Southern parts of the breeding range tended to be at greater risk than northern parts. Mean blood Hg concentrations for Bicknell's thrush at 21 distinct breeding sites ranged from 0.08 to 0.38 ug/g (ww) and at seven Greater Antillean wintering sites ranged from 0.03 to 0.42 ug/g (ww). Overall concentrations were significantly greater in wintering than in breeding areas. Mercury exposure profiles for four passerine species on Mt. Mansfield, Vermont indicated greatest MeHg uptake in Bicknell's thrush and yellow-rumped warbler (Dendroica coronata) and lowest in blackpoll warbler (Dendroica striata) and white-throated sparrow (Zonotrichia albicollis). The MeHg and total Hg ratio in blood in these four species was nearly 1:1. There was no correlation between blood and feather Hg concentrations in breeding Bicknell's thrush, in part because of apparent retention of winter Hg body burdens, within-season variation of MeHg availability, and confounding factors such as influences from age. Adult thrushes had significantly higher concentrations of feather Hg than did young-of-the-year. Although individual patterns of inter-year feather Hg concentrations were disordered, some individuals exhibited bioaccumulation of MeHg. Female blood Hg concentrations were significantly lower than males', in part because females have additional depurating mechanisms through eggs. Older male Bicknell's thrushes that breed in New England are therefore likely at greatest risk. Mechanisms for Hg methylation in montane areas without standing water are not yet fully understood. However, recent studies indicate that MeHg is present in forest tree leaves and leaf detritus; saturated soils and other moist microhabitats may also contribute to MeHg availability. Our finding of a correlation between regional litterfall Hg flux patterns and Bicknell's thrush blood Hg concentrations demonstrates on-site availability of MeHg. Further investigations into MeHg availability in montane environments are recommended to assess risk to insectivorous passerines, particularly the Bicknell's thrush.

Highly Selective Separation and Determination of Mercury (II) Using N,N′‐bis(2‐mercaptophenyl)ethanediamide

The present work describes a selective and economical method for the determination of mercury using N,N′‐bis(2‐mercaptophenyl)ethanediamide (H2L). The investigation included a study of the characteristics that are essential for solvent extraction and separation of mercury (II). Furthermore, a highly sensitive, selective, and rapid spectrophotometric method is described for the determination of trace amounts of mercury (II) by H2L. This compound reacts with mercury (II) in the range of pH 2–10 to produce a red complex [1:1 mol ratio of Hg(II)/H2L] soluble in dichloromethane. The complex was found to obey Beer's law from 5–128 µg ml−1 with an optimum range when the preconcentration factor is one. The concentration limits in Beer's law are reduced from 0.2–5.12 µg ml−1 with an optimum range when the preconcentration factor is 25. The relative standard deviations were calculated as 0.05% [15 samples, each containing 5 µg ml−1 Hg (II)]. The precision was determined from 25 results obtained for 2.5 × 10−5 M Hg(II); the mean value of Hg(II) was 2.53 × 10−5 M with a standard deviation of 1 × 10−7 M Hg(II). The proposed method has been applied to the determination of mercury in water samples.

Aqueous and vapor phase mercury sorption by inorganic oxide materials functionalized with thiols and poly-thiols

The objective of the study is the development of sorbents where the sorption sites are highly accessible for the capture of mercury from aqueous and vapor streams. Only a small fraction of the equilibrium capacity is utilized for a sorbent in applications involving short residence times (e.g., vapor phase capture of mercury from coal-fired power plant flue gases). So, dynamic capacity rather than equilibrium capacity is more relevant for these kinds of situations. Rapid sorption rates and higher dynamic capacity can be achieved by increasing the accessibility of active sites and decreasing the diffusional resistance to mass transport for the adsorbing species. This requires the use of open structured sorbent materials and attachment of functional groups on the external surface area of supports. The strong interaction of sulfur containing ligands (e.g., thiol) with mercury makes them suitable candidates for immobilization on these types of materials. In this study, inorganic oxide supports like alumina and silica are functionalized with thiol moieties like mercapto silane, cysteine and poly-cysteine for capturing mercury from aqueous and vapor phase. Aqueous phase Hg (II) sorption studies with cysteine/poly-cysteine functionalized silica showed that high dynamic capacity can be achieved by attaching active sites (thiol) on the external area of supports. Vapor phase Hg capture studies with thiol-functionalized mesoporous silica (Hg0 concentration = 3.37 mg/m3 with N2 as the carrier, gas temperature = 70 °C) yielded a capacity of 143 μg Hg/g for the sorbent. Although the sulfur content for the sorbent was low (0.80 wt. %) the molar ratio of Hg captured to sulfur was comparatively high (2.86×10−3) pointing to the high accessibility of sulfur sites.

Association of heavy metals with metallothionein and other proteins in hepatic cytosol of marine mammals and seabirds.

Distribution of Cu, Zn, Cd, Ag, Hg, and Se were determined in hepatocytosol of northern fur seals (Callorhinus ursinus), black-footed albatrosses (Diomedea nigripes), and Dall's porpoises (Phocoenoides dalli). Copper, Zn, and Cd were accumulated preferentially in metallothionein (MT) fraction and their contents in MT fraction increased with the amounts in the hepatocytosol. Silver was bound to both high-molecular-weight substances (HMWS) and MT in the hepatocytosol for all three species, whereas the distribution of Ag in the cytosol was different among the three species. In northern fur seals, Ag mainly was bound to MT, whereas it mainly was associated with HMWS in Dall's porpoises. In contrast, Ag was distributed almost equally in both HMWS and MT for black-footed albatrosses. Mercury content in HMWS and Se content in HMWS and low-molecular-weight substances (LMWS) increased with their contents in hepatocytosol for all the three species. A significant positive correlation was found between Se and Hg contents in high-molecular weight (HMW) fraction in cytosol. The molar ratio of Hg and Se was close to unity in HMW fraction of the specimens with high Hg concentration in cytosol, implying that the Hg-Se complex was bound to the HMWS. Analysis of metals in the hepatocytosol by high-performance liquid chromatography/inductively coupled plasma-mass spectrometry (HPLC/ICP-MS) suggests that multiple isoforms of MT are present in hepatocytosol of the three species and that the metal profiles in hepatocytosols are different among the species. To our knowledge, this is the first report on the association of Ag with HMWS and MT in hepatocytosol of marine mammals and seabirds. Also, distribution and interaction of Hg and Se were investigated for the first time in hepatocytosol of the higher trophic marine animals.

An assessment of the cord blood:maternal blood methylmercury ratio: implications for risk assessment.

In the current U.S. Environmental Protection Agency reference dose (RfD) for methylmercury, the one-compartment pharmacokinetic model is used to convert fetal cord blood mercury (Hg) concentration to a maternal intake dose. This requires a ratio relating cord blood Hg concentration to maternal blood Hg concentration. No formal analysis of either the central tendency or variability of this ratio has been done. This variability contributes to the overall variability in the dose estimate. A ratio of 1.0 is implicitly used in the model, but an uncertainty factor adjustment is applied to the central tendency estimate of dose to address variability in that estimate. Thus, incorporation of the cord:maternal ratio and its variability into the estimate of intake dose could result in a significant change in the value of the RfD. We analyzed studies providing data on the cord:maternal blood Hg ratio and conducted a Monte Carlo-based meta-analysis of 10 studies meeting all inclusion criteria to generate a comprehensive estimate of the central tendency and variability of the ratio. This analysis results in a recommended central tendency estimate of 1.7, a coefficient of variation of 0.56, and a 95th percentile of 3.4. By analogy to the impact of the similar hair:blood Hg ratio on the overall variability in the dose estimate, incorporation of the cord:maternal ratio may support a 3-fold uncertainty factor adjustment to the central tendency estimate of dose to account for pharmacokinetic variability. Whether the information generated in this analysis is sufficient to warrant a revision to the RfD will depend on the outcome of a comprehensive reanalysis of the entire one-compartment model. We are currently engaged in such an analysis.

Sonochemical preparation of HgSe nanoparticles by using different reductants

A convenient sonochemical process for the preparation of HgSe nanoparticles by using different reductants has been discovered. The HgSe nanoparticles, which were prepared in polyethylene glycol 400 (PEG 400), dextrose and hydroxylamine reductive systems, were analyzed by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). It was found that all the products were cubic phase HgSe by XRD measurements. The TEM observations showed that the HgSe nanoparticles were monodispersed and electron diffraction images of selected areas show that the products were polycrystalline. The sizes of most of all the HgSe nanoparticles were mainly among 30–40 nm, which were in coincidence with the very sizes that were estimated by Debye–Scherrer equation from the XRD patterns. XPS result showed that the ratio of Hg to Se was 57:43, indicating that the final products were rich in mercury.

Trace elements in two odontocete species ( Kogia breviceps and Globicephala macrorhynchus) stranded in New Caledonia (South Pacific)

Liver, muscle and blubber tissues of two short-finned pilot whales ( Globicephala macrorhynchus) and two pygmy sperm whales ( Kogia breviceps) stranded on the coast of New Caledonia have been analysed for 12 trace elements (Al, Cd, Co, Cr, Cu, Fe, organic and total Hg, Mn, Ni, Se, V, and Zn). Liver was shown to be the most important accumulating organ for Cd, Cu, Fe, Hg, Se, and Zn in both species, G. macrorhynchus having the highest Cd, Hg, Se and Zn levels. In this species, concentrations of total Hg are particularly elevated, reaching up to 1452 μg g −1 dry wt. Only a very low percentage of the total Hg was organic. In both species, the levels of Hg are directly related to Se in liver. Thus, a molar ratio of Hg:Se close to 1.0 was found for all specimens, except for the youngest K. breviceps. Our results suggest that G. macrorhynchus have a physiology promoting the accumulation of high levels of naturally occurring toxic elements. Furthermore, concentrations of Ni, Cr and Co are close to or below the detection limit in the liver and muscles of all specimens. This suggests that mining activity in New Caledonia, which typically elevates the levels of these contaminants in the marine environment, does not seem to be a significant source of contamination for these pelagic marine mammals.