Mercury Amalgam Research Articles

Phasing out mercury through collective action in artisanal gold mining: Evidence from a framed field experiment

Abstract The application of practices such as mercury amalgamation makes small-scale gold mining an economic activity with a high negative impact on health and the environment. Associative entrepreneurship – collective action – has been proposed as a scheme that would bring cleaner technologies to miners, in order to reduce the harmful effects of using mercury in the gold recovery. In this paper we investigate the extent to which miners can establish and sustain an association that aims to fulfill these goals. This is done by conducting a framed experiment with small-scale gold miners in Colombia. We test the effect of two institutional arrangements on associative entrepreneurship: exclusion and co-management. We found that miners made contributions that did not allow a sustained acquisition of the technology. However, we found that under co-management players could achieve long-lasting and efficient levels of individual contribution; but, conversely, exclusion did not trigger this kind of collective action. Policy implications of our results and avenues for further experimental research are discussed.

Increased mercury release from dental amalgam restorations after exposure to electromagnetic fields as a potential hazard for hypersensitive people and pregnant women.

Over the past decades, the use of common sources of electromagnetic fields such as Wi-Fi routers and mobile phones has been increased enormously all over the world. There is ongoing concern that exposure to electromagnetic fields can lead to adverse health effects. It has recently been shown that even low doses of mercury are capable of causing toxicity. Therefore, efforts are initiated to phase down or eliminate the use of mercury amalgam in dental restorations. Increased release of mercury from dental amalgam restorations after exposure to electromagnetic fields such as those generated by MRI and mobile phones has been reported by our team and other researchers. We have recently shown that some of the papers which reported no increased release of mercury after MRI, may have some methodological errors. Although it was previously believed that the amount of mercury released from dental amalgam cannot be hazardous, new findings indicate that mercury, even at low doses, may cause toxicity. Based on recent epidemiological findings, it can be claimed that the safety of mercury released from dental amalgam fillings is questionable. Therefore, as some individuals tend to be hypersensitive to the toxic effects of mercury, regulatory authorities should re-assess the safety of exposure to electromagnetic fields in individuals with amalgam restorations. On the other hand, we have reported that increased mercury release after exposure to electromagnetic fields may be risky for the pregnant women. It is worth mentioning that as a strong positive correlation between maternal and cord blood mercury levels has been found in some studies, our findings regarding the effect of exposure to electromagnetic fields on the release of mercury from dental amalgam fillings lead us to this conclusion that pregnant women with dental amalgam fillings should limit their exposure to electromagnetic fields to prevent toxic effects of mercury in their fetuses. Based on these findings, as infants and children are more vulnerable to mercury exposures, and as some individuals are routinely exposed to different sources of electromagnetic fields, we possibly need a paradigm shift in evaluating the health effects of amalgam fillings.

Identification of multifunctional graphene-gold nanocomposite for environment-friendly enriching, separating, and detecting Hg²⁺ simultaneously.

By virtue of the specific amalgam of mercury with gold and high specific area of a graphene scaffold, an environment-friendly multifunctional graphene-gold nanocomposite (G-AuNPs) has been identified and prepared by a simple one-pot redox reaction. The resultant G-AuNPs can reversibly enrich about 94% of Hg(2+) in water samples, which can be further separated by only a simple filtration. Importantly, the color of the G-AuNPs suspension exclusively changes from purple-red to light brown upon the addition of Hg(2+) in the presence of ascorbic acid, which can be applied for colorimetric detection of Hg(2+) with a detection limit (3σ, n = 20) of 1.6 × 10(-8) mol·L(-1). Furthermore, using ascorbic acid as reducing agents, both the preparation process and the resultant nanocomposite are nontoxic. To the best of our knowledge, this is the first report to enrich, separate and detect Hg(2+) contaminant simultaneously without causing any secondary pollution.

Implications of the Minamata Convention on Mercury for informal gold mining in Sub-Saharan Africa: from global policy debates to grassroots implementation?

In October 2013, after years of negotiation, governments from 92 countries signed a historic agreement called the Minamata Convention on Mercury, establishing mandatory measures to curb mercury use and pollution. Article 7 of the Convention stipulates that governments must create National Action Plans to reduce and where feasible eliminate mercury use in artisanal gold mining, a rapidly growing informal sector in much of Africa, with strategies to be monitored by the Convention Secretariat. The purpose of this study is to critically analyze the implications of the Minamata Convention for the artisanal mining sector in Sub-Saharan Africa, which currently depends upon mercury amalgamation for gold extraction. Our analysis draws on examples from Zimbabwe and Tanzania, countries with divergent political challenges but both with expanding artisanal mining sectors. We argue that a paradigm shift is needed to address intertwined technological, political and socio-economic challenges facing marginalized populations in mining communities. We highlight why meeting the Convention targets requires that international donors and national policymakers proactively engage—rather than vilify—artisanal miners who use mercury, prioritizing local knowledge and collaborative community-based decision making to develop effective pollution abatement initiatives in gold mining regions. We further argue that gender-sensitive grassroots empowerment initiatives including microfinance programs are vital to facilitate adopting cleaner technology, as required by Article 7. Finally, the analysis underscores the need for fundamentally reforming national mining policy priorities, recognizing marginalized mining communities’ resource rights and tackling livelihood insecurity as part of efforts to implement the Minamata Convention. In considering what ‘grassroots’ implementation could mean, the article contributes to a growing body of scholarship calling attention to fairness and equity concerns in order to achieve the aims of global environmental agreements.

Electrochemical reduction of 2,4-dichloro-1-(4-chloro-2-methoxyphenoxy)benzene (methyl triclosan) at glassy carbon cathodes in dimethylformamide

Methyl triclosan [2,4-dichloro-1-(4-chloro-2-methoxyphenoxy)benzene, 1], which is now considered an environmental pollutant, has been shown to be formed via microbial methylation of triclosan [5-chloro-2-(2,4-dichlorophenoxy)phenol, 2]. In the present work, cyclic voltammetry and controlled-potential (bulk) electrolysis have been employed to investigate the direct reduction of 1 at glassy carbon electrodes in dimethylformamide (DMF) containing 0.050M tetramethylammonium tetrafluoroborate (TMABF4). Cyclic voltammograms for the reduction of 1 at a glassy carbon electrode exhibit three irreversible cathodic peaks with peak potentials of −1.72, −2.07, and −2.35V (versus a cadmium-saturated mercury amalgam reference electrode). These three peaks correspond, respectively, to (a) scission of the ortho C–Cl bond, (b) cleavage of the two para C–Cl bonds, and (c) rupture of the C–O bond. Controlled-potential (bulk) electrolyses of 1 at reticulated vitreous carbon electrodes result in the formation of mixtures of 4-chloro-1-(4-chlorophenoxy)-2-methoxybenzene (3), 4-chloro-2-methoxy-1-phenoxybenzene (4a), 1-(4-chlorophenoxy)-2-methoxybenzene (4b), 1-methoxy-2-phenoxybenzene (5), anisole (6), and phenol.

Voltammetric Determination of Cisteine by Carbon Paste Electrode Cu-Hg Amalgamated

Plants have a defense mechanism for dealing with heavy metals, so that they are produced rapidly due to the high toxicity of the heavy metals. By this plant defense mechanism occurs, phytochelatins which are polypeptides , wherein a glutamic acid is linked to a cysteine via a γ - peptide bond, so that they have an ability to form bonds with metals through group SH in the portion of the cysteine .So it is very important find cheap and easily applied for the determination of phytochelatins methods. In literature are reported reported to an amalgam of Cu-Hg was efficient for determining phytochelatins by complexation of Cu+ with thiol groups by electrochemical methods such as voltammetry and polarography cathodic stripping voltammetry, [1].So in this work is to obtain a carbon paste electrode (CPE) modified with a Cu-Hg amalgam by electrolysis to develop a methodology for the determination of cysteine .The solutions used to obtain copper and mercury amalgam was a 0.05M concentration by applying a potential of -0.8V. Amalgam characterization was performed by cyclic voltammetry , wherein the support electrolyte was a borate buffer of pH 8.1 0.05M in which electrochemical processes typical Cu oxidation and ensuring Hg amalgam was performed properly observed .Subsequently technique cathodic stripping voltammetry (SCV) used for applying different potentials cysteine reservoir (Ed -0.28V) for 300 s and a potential sweep -0.1V to -1.0V. The graphics shows a reduction peak at -520mV associated Cu complex formation of cysteine-SR.The technique has been applied so far has proven to be very efficient since according to literature marked the peak potential is reported in the literature.This technique can be used as is relatively easy to perform and the data shown are very sensitive to very small quantities, although this technique is still used to determine concentrations of cysteine smaller. For later use it with a real sample in the determination of phytochelatins in mosses.Works cited[1] Y. B., S. I. y N. L., «Voltammetric determination of phytochelatins using Copper solid amalgam electrode,» Talanta, pp. 1253-1258, 2003.

Speciation of methylmercury in market seafood by thermal degradation, amalgamation and atomic absorption spectroscopy

Sample thermal decomposition followed by mercury amalgamation and atomic absorption has been employed for the determination of methylmercury (MeHg) in fish. The method involves HBr leaching of MeHg, extraction into toluene, and back-extraction into an aqueous l-cysteine solution. Preliminary studies were focused on the extraction efficiency, losses, contaminations, and species interconversion prevention. The limit of detection was 0.018µgg−1 (dry weight). The intraday precision for three replicate analysis at a concentration of 4.2µgg−1 (dry weight) was 3.5 percent, similar to the interday precision according to analysis of variance (ANOVA). The accuracy was guaranteed by the use of fortified samples involving 83–105 percent recoveries, and certified reference materials TORT-2 (lobster hepatopancreas) and DORM-3 (dogfish liver), providing 107 and 98 percent recovery of certified values. The greenness of the method was also evaluated with the analytical eco-scale being obtained a final score of 73 points which means an acceptable green analysis. The method was applied to fifty-seven market samples of different fish acquired from local markets in several sampling campaigns. The content of MeHg found varied between 0.0311 and 1.24µgg−1 (wet weight), with values that involve 33–129 percent of the total mercury content. Some considerations about food safety were also done taking into account data about Spanish fish consume and Tolerable Weekly Intake (TWI) established for MeHg.

Chitosan catalyzes hydrogen evolution at mercury electrodes

In recent decades chitosan has attracted great attention as biodegradable biomaterial with interesting properties, making chitosan useful in biomedicine and various fields of practical life. Chitosan was generally considered as an electrochemically inactive polysaccharide. Here we show that chitosan (containing glucosamine residues) produced voltammetric and chronopotentiometric reduction peaks at mercury and solid amalgam electrodes in a wide pH range. These peaks strongly increased with the buffer concentration and with decreasing pH and were assigned to the catalytic hydrogen evolution reaction. Under the same conditions chitin oligomers (containing N-acetylated glucosamines) displayed no significant electroactivity. Polyanionic polymers, such as DNA and hyaluronic acid, formed multilayers with the adsorbed chitosan.

Some Key Features and Possible Origin of the Metamorphic Rock-Hosted Gold Mineralization in Buru Island, Indonesia

DOI: 10.17014/ijog.v1i1.172This paper discusses characteristics of some key features of the primary Buru gold deposit as a tool for a better understanding of the deposit genesis. Currently, about 105,000 artisanal and small-scale gold miners (ASGM) are operating in two main localities, i.e. Gogorea and Gunung Botak by digging pits/shafts following gold-bearing quartz vein orientation. The gold extraction uses mercury (amalgamation) and cyanide processing. The field study identifies two types/generations of quartz veins namely (1) Early quartz veins which are segmented, sigmoidal, dis­continous, and parallel to the foliation of host rock. The quartz vein is lack of sulfides, weak mineralized, crystalline, relatively clear, and maybe poor in gold, and (2) Quartz veins occurred within a ‘mineralized zone’ of about 100 m in width and ~1,000 m in length. The gold mineralization is strongly overprinted by an argillic alteration zone. The mineralization-alteration zone is probably parallel to the mica schist foliation and strongly controlled by N-S or NE-SW-trending structures. The gold-bearing quartz veins are characterized by banded texture particularly colloform following host rock foliation and sulphide banding, brecciated, and rare bladed-like texture. The alteration types consist of propylitic (chlorite, calcite, sericite), argillic, and carbonation represented by graphite banding and carbon flakes. The ore mineralization is characterized by pyrite, native gold, pyrrhotite, and arsenopyrite. Cinnabar, stibnite, chalcopyrite, galena, and sphalerite are rare or maybe absent. In general, sulphide minerals are rare (<3%). Fifteen rock samples were collected in Wamsaid area for geochemical assaying for Au, Ag, As, Sb, Hg, Cu, Pb, and Zn. Eleven of fifteen samples yielded more than 1.00 g/t Au, in which six of them are in excess of 3.00 g/t Au. It can be noted that all high-grade samples are originally or containing limonitic materials, that suggest the role of supergene enrichment. Interestingly, most of the high-grade samples contain also high grade As (up to 991ppm), Sb (up to 885 ppm), and Hg (up to 75 ppm). Fluid inclusions in both quartz vein types consist of four phases including L-rich, V-rich, L-V-rich, and L1-L2-V (CO2)-rich phases. Mineralizing hydrothermal fluid is typified by CO2-rich fluid, moderate temperature of 300 - 400 ºC and a typical low salinity (0.36 to 0.54 wt.% NaCl eq). Based on those key features, gold mineraliza­tion in Buru Island meets the characteristics of LS epithermal or orogenic gold deposit types; however, it tends to be fitter with orogenic gold deposit rather than another type.

Environmental Monitoring of the Effects of Conventional and Artisanal Gold Mining on Water Quality in Ngwabalozi River, Southern Zimbabwe

Mineral extraction contributes positive to the socioeconomic fabric of many African countries but has also contributed to the deterioration of environmental quality. It has been branded the most destructive industry in the world. This study sought to assess the effects of conventional gold mining which use cyanide for gold extraction and artisanal gold mining which uses mercury amalgamation on water quality in Ngwabalozi River. Along the river, there are gold panning activities upstream and a conventional mine downstream. Water samples were collected at four sampling points: 1) upstream of the gold panning activities; 2) just downstream of gold panning area; 3) upstream of the conventional mine; 4) downstream of the conventional mine. Benthic macro-invertebrates were also collected at the name four points, identified to family level and counted. Water samples were analyzed for mercury, iron, arsenic, sulphates and turbidity. There were significant differences (p = 0.000) in the measurements of mercury, arsenic, sulphates, taxa richness, total count of individuals, Shannon-Weiner index, evenness index and average tolerance scores among the four sampling sites. Gold panning activities were found to pollute Ngwabalozi River with mercury while the conventional mine polluted the river with sulphates. Gold panning activities also feed a lot of sand into the river resulting in high turbidity. Gold mining reduced the taxa richness, total count of individual and the diversity of benthic macro-invertebrate community in the river. There was pollution induced succession in the river as pollution sensitive species were replaced by pollution tolerant ones.

A Survey of Mining and Tailings Disposal Practices of Selected Artisanal and Small Scale Mining Companies in Ghana

Management of small scale mining operations for maximum profitability with good environmental stewardship requires careful planning of mining and tailings disposal strategies. Field studies and observations of eleven selected artisanal and small-scale gold mining companies winning gold from alluvial (placer) source mostly, but also mine out cropping and underground quartz veins where available from the Takwaian and Birimian Formations in southwestern Ghana. Excavation is either by pitting or using backhoes. Sluicing, panning followed by mercury amalgamation and then roasting to recover the gold is the beneficiation method in use. Riverine waste rocks/tailings disposal is the main management invoked, however some companies do sell their waste to construction firms. Environmentally mining operations are impacting rivers with siltation, mercury pollution, channel diversions and possibly change in heavy metals concentration and water chemistry. Vast arable lands are degraded leaving peasant farmers with no livelihood due to failure by concessionaires to reclaim lands after closure. Only two companies out of the eleven somehow demonstrated environmental consciousness by constructing small tailings dam and backfilling some pits.

Submicron silica spheres decorated with silver nanoparticles as a new effective sorbent for inorganic mercury in surface waters

An analytical method using silica supported silver nanoparticles as a novel sorbent for the enrichment and determination of inorganic mercury (iHg) in surface water samples has been developed. Silver nanoparticles (AgNPs) were synthesized by a completely green procedure and were deposited onto the amine functionalized surface of silica submicrospheres (SiO2-NH2). The prepared nanocomposite material (SiO2/AgNPs) was characterized by transmission electron microscopy, UV-vis spectroscopy, X-ray diffraction and atomic force microscopy. The sorption and desorption characteristics of the nanosorbent SiO2/AgNPs toward Hg species were investigated by a batch method. An excellent separation of iHg and methylHg was achieved in 20 minutes at pH 2. The high selectivity of the SiO2/AgNPs toward iHg was explained by Hg(ii) reduction and subsequent silver-mercury amalgam formation. The analytical procedure for the enrichment and determination of inorganic mercury in surface waters was developed based on solid phase extraction and ICP-MS measurements. The total Hg content was determined after water sample mineralization. The recoveries reached for iHg in different surface waters e.g. river and Black sea water samples varied from 96-101%. The limits of quantification are 0.002 μg L(-1) and 0.004 μg L(-1) for iHg and total Hg, respectively; the relative standard deviations varied in the ranges of 5-9% and 6-11% for iHg and total Hg, respectively, for Hg content from 0.005 to 0.2 μg L(-1). The accuracy of the procedure developed for total Hg determination was confirmed by a comparative analysis of surface river (ICP-MS) and sea (CV AFS) waters.

The Minamata Convention on Mercury: Attempting to address the global controversy of dental amalgam use and mercury waste disposal

In October 2013, a new international binding treaty instrument called the Minamata Convention on Mercury opened for signature in Minamata City, Japan, the site of arguably the worst public health and environmental disaster involving mercury contamination. The treaty aims to curb the significant health and environmental impacts of mercury pollution and includes provisions addressing the mining, export and import, storage, and waste management of products containing mercury. Importantly, a provision heavily negotiated in the treaty addresses the use of dental fillings using mercury amalgam, an issue that has been subject to decades of global controversy. Though use of dental amalgam is widespread and has benefits, concerns have been raised regarding the potential for human health risk and environmental damage from emissions and improper waste management. While the Minamata Convention attempts to address these issues by calling for a voluntary phase-down of dental amalgam use and commitment to other measures, it falls short by failing to require binding and measurable targets to achieve these goals. In response, the international community should begin exploring ways to strengthen the implementation of the dental amalgam treaty provisions by establishing binding phase-down targets and milestones as well as exploring financing mechanisms to support treaty measures. Through strengthening of the Convention, stakeholders can ensure equitable access to global oral health treatment while also promoting responsible environmental stewardship.

One‐Pot Synthesis of Glycopolymer‐Porphyrin Conjugate as Photosensitizer for Targeted Cancer Imaging and Photodynamic Therapy

One-pot system combining multi-reactions is used to synthesize novel porphyrin-glycopolymer conjugates. Sodium mercury amalgam is used to catalyze the reactions: 1) reduction of RAFT polymerized poly(2-(methacrylamido) glucopyranose) (PMAG), 2) converting protoporphyrin to protoporphyrinogen, 3) thiol-ene coupling reaction of PMAG and protoporphyrinogen. The product is oxidized in the same pot to generate the final porphyrin-PMAG conjugates. The resulting conjugates are characterized by NMR, GPC, UV-Vis, and fluorescence spectroscopy. Glycoparticles (≈ 200 nm) bearing glucose units are formed by dissolving the conjugates in water. Glycoparticles show enhanced binding ability toward Con A, bind K562 cells efficiently and kill these cells under light irradiation in dose and light treatment length dependent manners, illustrating the potential biological applications of the conjugates as photosensitizer for cancer imaging and photodynamic therapy.

Cremation, Air Pollution, and Special Use Permitting: A Case Study

ABSTRACT Risks to health posed by emissions of hazardous air pollutants from crematories are emerging concerns. The presence of silver–mercury amalgams in bodies results in airborne emissions of mercury; and the combustion of essentially any material results in emissions of polychlorinated dibenzodioxins and furans (PCDD/Fs; “dioxins”). These and other trace emissions from crematories are not regulated at the U.S. federal or (typically) state level, but neighborhood concerns may necessitate quantitative evaluations of potential local impacts, and local officials may need to rely on such evaluations in order to determine whether and under what conditions to grant (or deny) operating permits. Here we present a case study in which these and other issues were evaluated. Using air dispersion models and health risk assessment models, we predicted exposures that would be within health-based guidelines. Concerned citizens provided information that seemed to suggest otherwise. In the end, communication, education, and compromise led to a favorable result.

Preparation of dental amalgam and spectral diagnosis of mercury in plasmas-laser in the region of 250 nm – 850 nm

In this paper we presents results of the spectral study of plasmas-laser of dental amalgam by technique Laser-induced Breakdown Spectroscopy (LIBS). Plasmas were generated focusing the beam of a Nd: YAG laser on the matrix of the mixture Ag-Sn-Cu and on amalgams with different proportions of mercury (3:2, 5:2, 6:2). Based on the spectral results and reported atomic parameters, became estimation of electron temperature plasmas- laser and their behavior with the concentration of Hg. The estimated values of the electron temperature for the respective proportions were 20 846 K, 19 139 K and 16 872 K, using the distribution of population of Boltzmann energy levels associated with spectral lines, considering conditions Local Thermodinamic Equilibrium (LTE) of plasmas.

English

Introduction Photodynamic antimicrobial chemotherapy studies regarding dental caries have been present more frequently in the literature. However, photodynamic antimicrobial chemotherapy depends on the adjustment of variables such as the type of light source and, photosensitisers target microorganism; this makes it difficult to draw meaningful comparisons. The purpose of this paper was to provide a critical review related to this coadjuvant approach in the prevention and treatment of dental caries. Materials and Methods A database search was made via Medline/PubMed (keywords: photodynamic therapy and dental caries) and 33 articles were found. Results Twelve articles were included after using the filter tool, being excluded reviews and manuscripts reporting works not related to the studied area. Conclusion The manuscripts showed that photodynamic therapy presents optimal results against dental caries, even though better understanding of photodynamic antimicrobial chemotherapy and its components are necessary before the clinical application of this alternative modality in the dental practice. Photodynamic antimicrobial chemotherapy for prevention and treatment of dental caries: a critical review MA Paschoal1, S Duarte2*, L Santos-Pinto1* Introduction The human oral cavity is heavily colonised by a complex, relatively specific and highly interrelated range of microorganisms (as many as 1000 different species have been detected) collectively known as normal oral microflora1. A peculiarity of this environment is that most of the bacteria found here are present in complex aggregates (known as biofilms)2. Microbial biofilms are composed of microorganisms adhered both to each other and to dental surfaces (or interfaces) and embedded in an extracellular polymeric matrix, which includes water and nutrient channels3. A change in a key environmental factor will trigger a shift in the balance of the resident microflora, which will promote the emergence of acidogenic/aciduric bacteria. The constant accumulation of these kind of bacteria change the equilibrium towards dental demineralisation (dental caries lesions)4. The constituents of diet present an important role in the development of dental caries. Sucrose is considered the most cariogenic dietary carbohydrate, because it is fermentable and serves as a substrate for the synthesis of extracellular polysaccharides (EPS) and intracellular polysaccharides in cariogenic dental plaque4. In addition, the presence of EPS (mainly insoluble glucan) promote bacterial adherence to the tooth surface and contribute to the structural integrity of dental biofilms. Yet, there is a clear evidence showing that sucrose exposure and insoluble EPS lead to a more cariogenic biofilm5. Dental caries is among the most significant human chronicle infectious diseases and results in the progressive dissolution of enamel. With the disease progression, it can lead the underlying dentine compromising the vitality of the element and its fixation in the maxillomandibular complex6. Prevention of dental caries can be achieved by controlling the accumulation of dental plaque by mechanical removal7. In cases of insufficient biofilm disorganisation, the association with antimicrobial chemical agents, such as chlorhexidine may help in the decreasing of pathogenic bacteria levels7. Unfortunately, this preventive approach does not reach the population as a whole, allowing dental cavity formation. Treatment of the carious lesion involves the removal of infected dentine with posterior restoration of the affected tooth with any of the variety of materials, for example mercury amalgam, resin composite and glass ionomer cements8. Due to emergence of antibiotic resistant strains, alteration in taste, burning sensation, increase of calculus formation and staining of the teeth and restorative materials stimulated a search for alternative treatments9. Recently, approaches that might offer the possibility of efficient intraoral bacterial count reduction with minimum damage to systemic health (preventive approach) and avoid secondary caries development reducing the chance of material substitution and pulp inflammation as well (curative approach) are necessary. For these circumstances, photodynamic antimicrobial chemotherapy (PACT) offers the possibility of a novel modality to reduce pathogenic bacteria, and consequently, prevent against (new) dental caries lesions10. * Corresponding authors Emails: marcobpaschoal@hotmail.com; lspinto@foar.unesp.br; sd84@nyu.edu 1 Department of Pediatric Dentistry, Araraquara School of Dentistry, Univ Estadual Paulista (UNESP), Araraquara, SP, Brazil 2 Department of Basic Science and Craniofacial Biology, College of Dentistry, New York University (NYU), New York, NY, USA

Mineralogy and spectral reflectance of soils and tailings from historical gold mines, Nova Scotia

Gold was mined in 64 districts in southern Nova Scotia between 1861 and the early 1940s, followed by limited, intermittent production up to the present. There is extensive dispersion of arsenic- and mercury-bearing mine tailings in the receiving environment downstream from many of these sites. Elevated mercury concentrations, highest near old stamp mill foundations, occur because of the mercury amalgamation process used to extract gold until the 1940s. Arsenic, on the other hand, occurs naturally in arsenopyrite, which is associated with the gold-bearing quartz veins and host rocks. Tailings are composed of fine sand- to silt-sized quartz, feldspar, illite and chlorite, and represent the primary rock-forming minerals in the metasedimentary host rocks of the Cambro-Ordovician Meguma Supergroup. Carbonate and sulphide minerals occur in minor to trace amounts, along with secondary minerals such as scorodite (FeAsO 4 ·2H 2 O). The extent of tailings dispersal can be mapped through hyperspectral remote sensing methods, as these major mineral components provide an identifiable spectral signature through visible, near infrared and short-wave infrared regions. This paper examines the mineralogy of soils, tills and tailings in the Upper and Lower Seal Harbour gold districts of Nova Scotia. Ground-truthing of space-borne hyperspectral data demonstrates the potential for remote mapping of the spatial extent of these historical mine wastes.

POTTALI KALPANA: A CONCISE AND POTENT PHARMACEUTICAL DOSAGE FORM OF INDIAN SYSTEMS OF MEDICINE

Indian system of medicine is a treasure of spectacular and peculiar pharmaceutical dosage forms. Ayurvedic herbo - mineral drugs contain several types of formulations with vivid variet ies. Maximum potency with minimum dosage is the philosophy of these drugs. Pottali kalpana is one of such, highly potent, concise and embossed dosage form in Ayurveda. The main ingredients of it, is the amalgam of mercury and sulphur, which is treated with different plant materials and ultimately given a compact form by the application of natural binder. This short review describe about the history, necessity, preparation and mode of application of the Pottali kalpana, an unique Ayurvedic pharmaceutical dos age form.

Enzymatic activity and catalytic hydrogen evolution in reduced and oxidized urease at mercury surfaces

It was originally shown [10] that urease retains its enzymatic activity when adsorbed at bare mercury and solid amalgam surfaces. However the opinion later prevailed that, when adsorbed at bare metal electrodes, proteins are irreversibly denatured. Here we confirm that urease is enzymatically active at a bare solid amalgam surface as found by Santhanam et al., and we show that this enzyme is equally active at a thiol-modified amalgam surface. We also show that it is the reduced form of urease, which is enzymatically active at Hg surfaces. Oxidation of the protein, resulting in formation of disulfide bonds, strongly decreases the enzyme activity. Using constant current chronopotentiometric stripping (CPS) we show that the exposure of surface-attached urease to negative potentials results in the protein unfolding. The extent of the unfolding depends upon the amount of time for which the protein is exposed to negative potentials, and at very short times this unfolding can be avoided. At thiol-modified Hg surfaces the protein is less vulnerable to the effects of the electric field. We conclude that the loss of enzymatic activity, resulting from a 10min exposure of the protein to −0.58V, is not due to reduction of the disulfide bonds as suggested by Santhanam et al. This loss is probably a result of protein reorientation, due to reduction of the Hg-S bonds (formed by accessible cysteines), followed by prolonged electric field effect on the surface-attached protein.