Inorganic Mercury Compounds Research Articles

Mercury speciation in pilot whale from Faroe Islands, 1977–2015

Mercury (Hg) is a naturally occurring heavy metal, but human activities and natural processes have led to increased pollution with Hg in the environment. Organic mercury, such as methyl mercury (MeHg), is considered more toxic than most inorganic mercury compounds. MeHg is rapidly taken up by aquatic organisms and bioaccumulates through the aquatic food web. The bioaccumulation causes high levels of MeHg in apex predators, such as pilot whales. Pilot whale meat is a traditional food source on the Faroe Islands; thus the consumption of pilot whale meat can lead to high Hg exposures in humans. The majority of the total Hg in pilot whale and fish is generally assumed to be MeHg. However, the relative amount of MeHg to total Hg can be highly variable. For risk assessment, it is relevant to know both the MeHg and the total Hg content. This study summarizes the knowledge of muscle MeHg concentrations relative to total Hg concentrations in pilot whales in the Faroe Islands. The pilot whale tissue was sampled during 1977–78, 1986–87, 2009–2010, and 2015. The 2015 samples included two pairs of fetuses/mothers. The results showed that the 1977–78 pilot whale muscle samples had lower relative concentrations of MeHg to total Hg compared to samples from the subsequent years. This discrepancy between early and later years could not solely be explained by increased demethylation related to concentration differences. Instead, the difference is more likely explained by variations in relative amounts of MeHg in prey of the pilot whales. In the fetuses the total Hg concentration was 20% of the Hg concentration in the mother. The relative MeHg concentrations in the fetuses were also lower (∼20%–30%) than in the mother. However, the MeHg to total Hg fraction in the fetus was similar or higher than in the mother.

The use of CytoSorb in acute oral mercuric chloride poisoning at a potentially lethal dose.

The study aims to present a case of acute mercuric chloride poisoning treated successfully with continuous renal replacement therapy using the CytoSorb filter. A 21-year-old female patient after a suicide attempt by intentional ingestion of mercuric chloride, was admitted to the hospital with features of multiple organ damage for specific treatment. The performed laboratory tests confirmed high levels of mercury in the blood (1051 μg/L) and urine (22,960 μg/L). Due to acute renal failure, continuous renal replacement therapy (CRRT) CVVHD Ci-Ca was initiated; the procedure was then converted to CVVHDF Ci-Ca with ultrafiltration to optimise therapy, and CytoSorb was added to the artificial kidney system on day 3. Specific antidote therapy (DMPS) was administered concurrently. The ongoing treatment resulted in a reduction in subjective complaints, a decrease in blood mercury levels to 580 μg/L, and an improvement in parenchymal organ function. In the event of poisoning with inorganic mercury compounds (mercuric chloride), continuous renal replacement therapy using the CytoSorb filter as an extracorporeal blood purification method may be considered.

Role of activated p21-activated kinase 2 in methylmercury-induced embryotoxic effects on mouse blastocysts.

Methylmercury (MeHg), a biotransformation product derived from mercury or inorganic mercury compounds in waterways, is a potent toxin that exerts hazardous effects on human health via environmental contamination. Previous studies have reported MeHg-induced impairment of nerve development in embryogenesis and placental development. However, the potential deleterious effects and regulatory mechanisms of action of MeHg on pre- and post-implantation embryo development are yet to be established. Experiments from the current study clearly demonstrate that MeHg exerts toxic effects on early embryonic development processes, including the zygote to blastocyst stage. Induction of apoptosis and decrease in embryo cell number were clearly detected in MeHg-treated blastocysts. Additionally, intracellular reactive oxygen species (ROS) generation and activation of caspase-3 and p21-activated protein kinase 2 (PAK2) were observed in MeHg-treated blastocysts. Importantly, prevention of ROS generation by pre-treatment with Trolox, a potent antioxidant, significantly attenuated MeHg-triggered caspase-3 and PAK2 activation as well as apoptosis. Notably, the downregulation of PAK2 via transfection of specifically targeted siRNA (siPAK2) led to marked attenuation of PAK2 activity and apoptosis and the deleterious effects of MeHg on embryonic development in blastocysts. Our findings strongly suggest that ROS serve as an important upstream regulator to trigger the activation of caspase-3, which further cleaves and activates PAK2 in MeHg-treated blastocysts. Activated PAK2 promotes apoptotic processes that, in turn, cause sequent impairment of embryonic and fetal development.

Roles of glutathione peroxidase 4 on the mercury-triggered ferroptosis in renal cells: implications for the antagonism between selenium and mercury.

Understanding of how mercury species cause cellular impairments at the molecular level is critical for explaining the detrimental effects of mercury exposure on the human body. Previous studies have reported that inorganic and organic mercury compounds can induce apoptosis and necrosis in a variety of cell types, but more recent advances reveal that mercuric mercury (Hg2+) and methylmercury (CH3Hg+) may result in ferroptosis, a distinct form of programmed cell death. However, it is still unclear which protein targets are responsible for ferroptosis induced by Hg2+ and CH3Hg+. In this study, human embryonic kidney 293T cells were used to investigate how Hg2+ and CH3Hg+ trigger ferroptosis, given their nephrotoxicity. Our results demonstrate that glutathione peroxidase 4 (GPx4) plays a key role in lipid peroxidation and ferroptosis in renal cells induced by Hg2+ and CH3Hg+. The expression of GPx4, the only lipid repair enzyme in mammal cells, was downregulated in response to Hg2+ and CH3Hg+ stress. More importantly, the activity of GPx4 could be markedly inhibited by CH3Hg+, owing to the direct binding of the selenol group (-SeH) in GPx4 to CH3Hg+. Selenite supplementation was demonstrated to enhance the expression and activity of GPx4 in renal cells, and consequently relieve the cytotoxicity of CH3Hg+, suggesting that GPx4 is a crucial modulator implicated in the Hg-Se antagonism. These findings highlight the importance of GPx4 in mercury-induced ferroptosis, and provide an alternative explanation for how Hg2+ and CH3Hg+ induce cell death.

Low-dose silver nanoparticles plus methyl mercury exert embryotoxic effects on mouse blastocysts via endoplasmic reticulum stress and mitochondrial apoptosis.

The health and environmental impacts of the increasing commercial use of silver nanoparticles (AgNPs) are a growing concern. Methyl mercury (MeHg) is a potent toxin that biotransforms from mercury or inorganic mercury compounds in waterways and causes dangerous environmental contamination. However, the potential interactions and combined effects of AgNPs and MeHg are yet to be established. In the current study, we showed that low/non-embryotoxic doses of AgNPs and MeHg interact synergistically to induce embryotoxicity and further explored the underlying mechanisms affecting mouse embryo development. Notably, co-treatment with noncytotoxic concentrations of AgNPs (10 μM) and MeHg (0.1μM) triggered apoptotic processes and embryotoxicity in mouse blastocysts and evoked intracellular reactive oxygen species (ROS) generation, which was effectively blocked by preincubation with 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (trolox), a classic antioxidant. Further experiments demonstrated that ROS serve as a key upstream inducer of endoplasmic reticulum (ER) stress and mitochondria-dependent apoptotic processes in AgNP/MeHg-induced injury of mouse embryo implantation and pre- and postimplantation development. Our results collectively indicate that AgNP and MeHg at non-embryotoxic concentrations can synergistically evoke ROS, ultimately causing embryotoxicity through promotion of ER stress and mitochondria-dependent apoptotic signaling cascades.

Indices of the DNA repair system in the brain of fish as a biomarker of inorganic mercury burden

Mercury is a widespread heavy metal that causes a stable and prolonged environmental pollution. Low concentrations of inorganic and organic mercury compounds are found in almost all water bodies. The high level of mercury bioaccumulation is a cause of tissue-specific toxicity, including neurotoxicity. Absorbed in nervous tissue mercury can cause brain disorders both in neural and glial cells. The brain of fish is considered one of the most susceptible targets for cytotoxicity of mercury in aquatic ecosystems. Taking into account that different forms of mercury have widespread distribution and exhibit a strong neurotoxic effect, the assessment of mercury cytotoxicity in the brain of fish is relevant and extremely important. Rainbow trout Oncorhynchus mykiss was exposed to mercury chloride in the dose range of 5-20 μg/L for 60 days to study the chronic exposure of low doses. In this paper, we studied the influence of inorganic mercury on oxidative stress, DNA repair proteins – ERCC1 and PARP1 in the trout’s brain. The results obtained have shown that the chronic effect of inorganic mercury causes dose-dependent oxidative stress in the fish brain. In addition, low concentrations of mercury (10 and 20 μg/L) caused a decrease in the content of ERCC1 in the brain of fish. On the contrary, the same doses have caused an increase in PARP1 expression. That is the chronic influence of low concentrations of inorganic mercury has a negative effect in the fish brain. Observed results showed that inorganic mercury has a potential for suppressing DNA repair and, therefore, increases the instability of genome. Thus, ERCC1 and PARP1 can be considered as the sensitive biomarkers of mercury cytotoxicity in the fish brain. A further study of mercury neurotoxicity is needed to find out the hazard of mercury environmental pollution as well as a validation of biomarkers of their impact.

До обґрунтування переліку небезпечних високотоксичних хімічних речовин, які підлягають особливому контролю щодо обігу, зберігання, використання та утилізації. Частина 1 (рицин, сполуки талію та фосфорорганічні сполуки)

ABSTRACT. The Aim of the Research. Based on an analytical review of literature data, to identify a group of highly toxic chemicals which over the past decades are most often used in deliberate criminal and suicidal incidents, sabotage and terrorist act; the traffic, storage, use and disposal of which must be especially carefully monitored by law enforcement agencies. Materials and Methods. An analytical review of scientific publications was carried out using the abstract databases of scientific libraries Pub Med, Medline and text databases of scientific publishing houses Elsevier, Pub Med, Central, BMJ group as well as other VIP databases. Methods of systemic, comparative, and content analysis were used. Results and Conclusions. The scientific publications on hazardous highly toxic chemicals, which over the past quarter century are most often used in the world, notably in deliberate criminal and suicidal incidents, sabotage, and terrorist acts, are being analysed. It was found that these chemicals mainly include ricin, thallium compounds, organophosphorus compounds, as well as chemical warfare agents, arsenic and its compounds, cyanides, and inorganic water-soluble mercury compounds (mercury bichloride, sodium merthiolate), as well as paraquat and diquat pesticides. Based on the analysis of their toxicity, clinical and morphological expression of intoxication with various routes of entry into the body, the need to include them in the List of Highly Hazardous Chemicals, whose traffic, storage, use, and disposal require stricter control of law enforcement agencies, is justified. The first part of this article presents ricin, thallium compounds, organophosphorus compounds, and chemical warfare agents. Key Words: hazardous highly toxic chemicals, ricin, thallium compounds, organophosphorus compounds.

Speciation of Inorganic Mercury Compounds in Solid Samples via Thermo‐desorption Experiments

AbstractTo establish a standardized method for specifying mercury in solid samples, a database of relevant mercury species is created via thermo‐desorption. By measuring Hg(t) and Hg(0), different evaporation characteristics of mercury halides, sulfide, oxides, nitrates, and sulfates were recorded. It was possible to create a baseline for analyzing solid samples with unknown mercury content. All mercury species without a halide compound evaporate over 200 °C and as elemental mercury. All mercury halides evaporate mainly as oxidized species. From this fact it can be concluded that mercury halides desublimate when heated and have a vapor pressure as a solid. This unique characteristic was only seen by mercury halides. All other species seem to decompose into their single components when heated.

Inhibition of Tyrosinase by Mercury Chloride: Spectroscopic and Docking Studies.

Inorganic mercury compounds have been used in skin-lightening products since ancient times. Although a previous study demonstrated that mercury impeded the transfer of Cu2+ to the apotyrosinase, the effect of mercury on tyrosinase is still unclear. In the present study, the mechanism of mercury chloride (HgCl2) induced inactivation of tyrosinase was investigated for the first time. The IC50 values were 29.97 and 77.93 μmol/L for monophenolase and diphenolase, respectively. A kinetic analysis revealed that HgCl2 inhibited tyrosinase activity in an irreversible non-competitive manner. The strong intrinsic fluorescence quenching suggested that the formation of the HgCl2-tyrosinase complex induced conformational changes of the enzyme, and HgCl2 had only one single binding site or a single class of binding site on tyrosinase. The molecular docking and further experiments demonstrated that HgCl2 bound to the amino residuals (His) in the catalytic center of tyrosinase. To our knowledge, these findings presented in this paper were the first evidence of the direct interactions between HgCl2 and tyrosinase, which provided a deep understanding of the inhibition mechanism of mercury on tyrosinase.

Pharmacological activation of dimethylarginine dimethylaminohydrolase (DDAH) activity by inorganic nitrate and DDAH inhibition by NG-hydroxy-L-arginine, Nω,Nω-dimethyl-L-citrulline and Nω,Nω-dimethyl-Nδ-hydroxy-L-citrulline: results and overview.

Asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) are endogenous inhibitors of nitric oxide (NO) synthase. SDMA is excreted in the urine without major metabolization. About 10% of daily produced ADMA are excreted unchanged in the urine. The major elimination route of ADMA (about 90%) involves its hydrolysis to dimethylamine (DMA) and L-citrulline by dimethylarginine dimethylaminohydrolase (DDAH) and excretion of DMA in the urine. High circulating and low excretory concentrations of ADMA are considered risk factors. Experimentally, DDAH activity can be inhibited by SH-specific agents such as inorganic and organic mercury compounds, and by S-nitrosothiols which block the SH group of a particular cysteine moiety of DDAH that is essential for its hydrolytic activity. Alternatively, DDAH activity can be inhibited by organic compounds that compete with the substrate ADMA for DDAH. Arginine analogs that contain substituents on guanidine nitrogen atom(s) (NG) represent a class of DDAH inhibitors. In the present study, we investigated the effects of physiological and natural amino acid derivatives of L-arginine and L-citrulline as well as of nitrate and nitrite, the major circulating and excretory metabolites of NO and NO donating drugs. Here, we report for the first time that the physiological NG-hydroxy-L-arginine, an isolable intermediate in NO synthesis, inhibits recombinant DDAH-1 activity (IC50 ≈ 100µM). Two plant L-citrulline derivatives, i.e., Nω,Nω-dimethyl-L-citrulline and Nω,Nω-dimethyl-Nδ-hydroxy-L-citrulline (connatin), were found to inhibit almost completely hepatic DDAH activity in vitro in rat homogenate at a concentration of 100µM each. At pharmacological concentrations (i.e., 1mM), inorganic nitrate, but not inorganic nitrite, was found to increase rat liver DDAH activity. In urine of 18 patients with Becker's muscular dystrophy, nitrate was found to correlate closely with DMA (Spearman, r = 0.73, p = 0.002). In summary, NG-hydroxy-L-arginine, Nω,Nω-dimethyl-L-citrulline and Nω,Nω-dimethyl-Nδ-hydroxy-L-citrulline are novel inhibitors of DDAH activity. This article provides an overview of amino acid-based DDAH inhibitors and discusses potential underlying inhibition mechanisms.

Methyl-mercury induces apoptosis through ROS-mediated endoplasmic reticulum stress and mitochondrial apoptosis pathways activation in rat cortical neurons

Methyl-mercury (MeHg) is a dangerous environmental contamination biotransformed from mercury or inorganic mercury compounds in waterways, which induces severe toxic effects in central nervous system. Oxidative stress is involved in various ways of intracellular physiological or pathological processes including neuronal apoptosis. For understanding the ways that oxidative stress participating in MeHg-induced apoptosis, the current study attempted to explore the effects of oxidative stress on endoplasmic reticulum (ER) and mitochondria function, especially focussing on ER stress followed by unfold protein response (UPR), as well as mitochondrial apoptosis pathways activation in primary cultured cortical neurons. Cells were exposed to 0, 0.25, 0.5, or 1 µM MeHg for 1–6 h, respectively, followed by cell viability quantification. For further experiments, 100 µM of 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (trolox) pre-treatment for 3 h followed by 1 µM MeHg for 6 h were performed for evaluation of oxidative stress, neuronal apoptosis, ER stress, UPR activation, and mitochondrial dysfunction. Results showed that MeHg induced neuronal oxidative stress, apoptosis, up-regulating glucose-regulated protein (GRP78, GRP94), spliced Xbp1, activating transcription factor 4 (ATF4) mRNA, with activation of UPR including PKR-like ER kinase-eIF2α, inositol-requiring enzyme 1, and ATF6 pathways, as well as C/EBP homologous transcription factor protein and cleaved caspase-12 up-regulation. In addition, mitochondrial function was disrupted by MeHg, which was supported by caspase-3 and caspase-9 activation, and high levels of cytoplasm cytochrome C and apoptosis induce factor. Trolox pre-treatment significantly blocked neuronal apoptosis, ER stress, UPR activation, as well as mitochondrial dysfunction, in addition to the direct anti-oxidation. In conclusion, MeHg induces neuronal apoptosis through ER and mitochondria pathway, oxidative stress plays important roles in mediating apoptosis pathways activation.

Specificity of Mercury Detecting Reagents for Skin Lightening Creams

Inorganic mercury compound have been used for long time in cosmetics preparations for its skin lightening effect. The used of mercury in cosmetics has been prohibited as stipulated in the decision of the BPOM RI (Head of the Food and Drug Supervisory Agency) No.HK.00.01.432.6147. Based on health department research from various countries, there are a number of skin lightening products containing mercury between 660-57.000 μg/kg. People needs a quick and easy way to detect mercury in a lightening cream, so that people can test the safety of cream that used. One alternative that can be used to detect mercury in skin lightening cosmetics is using detecting reagents. The aim of this study was preparation of specific and sensitive mercury detecting reagents. The detecting reagents consisted mixtures of diphenylcarbazone and acetic acid in 96% of ethanol. The specificity test is performed by adding diphenylcarbazone solution into a lightening cream containing whitening agents such as mercury, hydroquinone, bangkuang extract and mixture of these substances. Assay was also performed on simulated cream that contained mercury, zinc oxide, bismuthsubnitrate, and mixture of mercury, zinc oxide and bismuthsubnitrate. The mercury detecting reagents gives a distinctive result that shown by the formation of purple mercury complex in less than 3 minutes.

PH-Dependent Effects of L-Cysteine on Mercury Dissolution of α-HgS and β-HgS.

Mercury sulfide is an insoluble inorganic mercury compound, and it is the main chemical form in traditional oral mercury-containing medicines. Hg2+ has a high affinity for thiols, and small molecule thiols in the gastrointestinal tract may promote mercury dissolution of mercury sulfide by binding to Hg2+. L-cysteine is the only amino acid that possesses a reducing sulfhydryl group (-SH), out of the 20 amino acids. This study investigates the effect of L-cysteine on mercury dissolution of mercury sulfide at pHs ranging from 1.2 to 7.2. The results showed that L-cysteine had different pH-dependent effects on the mercury dissolution of α-HgS and β-HgS. For α-HgS, the dissolved mercury concentration increased from 5.47 ± 0.97ng/mL to 12.49 ± 0.54ng/mL when the pH rose from 1.2 to 4.2, and decreased to 3.37 ± 0.70ng/mL at pH6.0 and then increased to 9.36 ± 0.79ng/mL at pH7.2. For β-HgS, the dissolved mercury concentration increased from 151.09 ± 2.25ng/mL to 2346.71 ± 62.62ng/mL when the pH increased from 1.2 to 7.2. In conclusion, L-Cys was distinctly enhanced upon mercury dissolution of α-HgS and β-HgS with increasing pH. These results may contribute to our understanding of the mercury absorption mechanism of traditional oral mercury-containing medicines.

ON THE ROLE OF BIOMONITORING IN THE ASSESSMENT OF THE HEALTH OF THE POPULATION EXPOSED TO MERCURY

When examining the population exposed to organic and inorganic compounds of mercury, a comprehensive approach is proposed, including chemical monitoring of environmental objects, biological monitoring, clinical examination of persons exposed to mercury, identification of high-risk groups.

Mercury bioavailability, transformations, and effects on freshwater biofilms.

Mercury (Hg) compounds represent an important risk to aquatic ecosystems because of their persistence, bioaccumulation, and biomagnification potential. In the present review, we critically examine state-of-the-art studies on the interactions of Hg compounds with freshwater biofilms, with an emphasis on Hg accumulation, transformations, and effects. Freshwater biofilms contain both primary producers (e.g., algae) and decomposers (e.g., bacteria and fungi), which contribute to both aquatic food webs and the microbial loop. Hence they play a central role in shallow water and streams, and also contribute to Hg trophic transfer through their consumption. Both inorganic and methylated mercury compounds accumulate in biofilms, which could transform them mainly by methylation, demethylation, and reduction. Accumulated Hg compounds could induce diverse metabolic and physiological perturbations in the microorganisms embedded in the biofilm matrix and affect their community composition. The bioavailability of Hg compounds, their transformations, and their effects depend on their concentrations and speciation, ambient water characteristics, biofilm matrix composition, and microorganism-specific characteristics. The basic processes governing the interactions of Hg compounds with biofilm constituents are understudied. The development of novel conceptual and methodological approaches allowing an understanding of the chemo- and biodynamic aspects is necessary to improve the knowledge on Hg cycling in shallow water as well as to enable improved use of freshwater biofilms as potential indicators of water quality and to support better informed risk assessment. Environ Toxicol Chem 2017;36:3194-3205. © 2017 SETAC.

Speciation of mercury in fish oils using liquid chromatography inductively coupled plasma mass spectrometry

This paper describes a simple and rapid procedure, using liquid chromatography (LC) followed by pneumatic nebulization inductively coupled plasma mass spectrometry (ICP-MS), for the separation and determination of inorganic, methyl, and ethyl mercury compounds. We obtained well-resolved chromatograms within 6min using a reversed-phase C8 column as the stationary phase and a solution containing 0.6% v/v 2-mercaptoethanol and 3% v/v methanol as the mobile phase. We applied this method to the speciation of mercury in several fish oil samples purchased locally. The accuracy of the procedure was verified through the analysis of a reference material (NRCC DOLT-3 Dogfish Liver) certified for both total mercury and methyl mercury. The detection limits of the studied mercury compounds were in the range 0.013–0.026ngHgmL−1 in the injected solutions, corresponding to 0.5–1ngg−1 in the original fish oil samples. Employing a microwave-assisted extraction procedure and the mobile phase solution for the extraction of the mercury compounds, we obtained an extraction efficiency of greater than 89% from the fish oil samples. The recoveries of the individual mercury species added to the samples at 10–25ngHgg−1 were between 93 and 107%. The precision measured between sample replicates was greater than 12% for all determinations.

Chemical state of mercury and selenium in sewage sludge ash based P-fertilizers

Phosphorus-fertilizers from secondary resources such as sewage sludge ash (SSA) will become more important in the future as they could substitute conventional fertilizers based on the nonrenewable resource phosphate rock. Thermochemical approaches were developed which remove heavy metals from SSA prior to its fertilizer application on farmlands. We analyzed the chemical state of mercury and selenium in SSA before and after thermochemical treatment under different conditions for P-fertilizer production by X-ray absorption near edge structure (XANES) spectroscopy. In some incineration plants the mercury loaded carbon adsorber from off-gas cleaning was collected together with the SSA for waste disposal. SSAs from those plants contained mercury mainly bound to carbon/organic material. The other SSAs contained inorganic mercury compounds which are most probably stabilized in the SSA matrix and were thus not evaporated during incineration. During thermochemical treatment, carbon-bound mercury was removed quantitatively. In contrast, a certain immobile fraction of inorganic mercury compounds remained in thermochemically treated SSA, which were not clearly identified. HgSe might be one of the inorganic compounds, which is supported by results of Se K-edge XANES spectroscopy. Furthermore, the chemical state of selenium in the SSAs was very sensitive to the conditions of the thermochemical treatment.

Thermogravimetric and XRD study of the effects of chloride salts on the thermal decomposition of mercury compounds

In this paper, the effects of chloride salt (MgCl2, CaCl2 or NaCl) addition on the thermal decomposition of five inorganic mercury compounds (HgCl2, HgS, Hg(NO3)2·H2O, HgO, and HgSO4) were investigated by thermogravimetric analysis. Mercury-contaminated soil samples collected from Inner Mongolia were used to verify the results. The desorption temperatures of the mercury compounds increased in the following order: HgCl = HgCl2 < HgS < Hg(NO3)2·H2O < HgO < HgSO4. Among the chloride salts, MgCl2 had the greatest effect on thermal desorption of the mercury compounds, with the greatest reduction in the initial temperature of thermal desorption. After MgCl2 treatment, the mercury removal rates for the soil were 65.67–81.35 % (sample A), 70.74–84.91 % (sample B), and 69.08 % (sample C). The increase in the mercury removal rate for sample C with addition of MgCl2 was particularly large (34.96–69.08 %). X-Ray diffraction analysis of white crystals from the thermal desorption with MgCl2 indicated that MgCl2 promoted conversion of the mercury compounds in the soil to mercury(II) chloride and dimercury dichloride. This transformation is beneficial for applying thermal desorption to remedy mercury-contaminated soils and treat of mercury containing waste.

Determination of mercury in selected polluted sediments using HPLC-ICP-MS in Westbank area, Western Cape, South Africa

High selectivity, excellent linearity and reproducibility were achieved using HPLC-ICP-MS method for mercury in sediments. The HPLC-ICP-MS method reported previously for mercury in biota analysis was adapted in terms of operational consumables and optimized for the efficient mercury determination in riverbed sediments; a first for South Africa. Results obtained for real environmental samples, were verified by Direct Mercury Analysis (DMA) by an accredited laboratory. The determination of inorganic and organic mercury compounds in sediments was based on the complexation of mercury compounds with cysteine. The separation was achieved on a reversed-phase C18 column (15 cm×4.6mm id) using aqueous 0.1% w/v L-cysteine•HCl+0.1% w/v L-cysteine mobile phase at a flow rate of 0.8 mL min-1 at ambient temperature. The method was found to be suitable for the routine analysis of Hg compounds in sediments as well as aqueous media and was developed to determine the influence of humic substances on the bioavailability of mercury species. The results were comparable and consistent with those determined with a Direct Mercury Analyzer. The detection limit for methylmercury, ethylmercury and inorganic mercury were lower than 10 ng L-1 and recoveries for spiked samples was >90 % . The accuracy of the method was assessed by the analysis of certified reference material (European Reference Material ERMCC580 and Tort-2) and found to be in good agreement. Mercury concentration was determined in sediments collected from the Eerste Kuils River, Westbank area, Kuilsriver, Western Cape, South Africa. Mercury concentration was determined to vary from 2-14 ng g-1 (w.wt).

Metabolic regulation in meagre, Argyrosomus regius (Asso, 1801): Study of gene-diet interactions on lipid metabolism

Metabolic regulation in meagre, Argyrosomus regius (Asso, 1801): Study of gene-diet interactions on lipid metabolism