Abatement of mercury pollution in the small-scale gold mining industry: Restructuring the policy and research agendas

This paper critiques contemporary research and policy approaches taken toward the analysis and abatement of mercury pollution in the small-scale gold mining sector. Unmonitored releases of mercury from gold amalgamation have caused considerable environmental contamination and human health complications in rural reaches of sub-Saharan Africa, Latin America and Asia. Whilst these problems have caught the attention of the scientific community over the past 15-20 years, the research that has since been undertaken has failed to identify appropriate mitigation measures, and has done little to advance understanding of why contamination persists. Moreover, the strategies used to educate operators about the impacts of acute mercury exposure, and the technologies implemented to prevent farther pollution, have been marginally effective at best. The mercury pollution problem will not be resolved until governments and donor agencies commit to carrying out research aimed at improving understanding of the dynamics of small scale gold mining communities. Acquisition of this knowledge is the key to designing and implementing appropriate support and abatement measures. (c) 2005 Elsevier B.V. All rights reserved.

Improving awareness of mercury pollution in small-scale gold mining communities: Challenges and ways forward in rural Ghana

This paper critiques the approach taken by the Ghanaian Government to address mercury pollution in the artisanal and small-scale gold mining sector. Unmonitored releases of mercury-used in the gold-amalgamation process-have caused numerous environmental complications throughout rural Ghana. Certain policy, technological and educational initiatives taken to address the mounting problem, however, have proved marginally effective at best, having been designed and implemented without careful analysis of mine community dynamics, the organization of activities, operators' needs and local geological conditions. Marked improvements can only be achieved in this area through increased government-initiated dialogue with the now-ostracized illegal galamsey mining community; introducing simple, cost-effective techniques for the reduction of mercury emissions; and effecting government-sponsored participatory training exercises as mediums for communicating information about appropriate technologies and the environment. (c) 2006 Elsevier Inc. All rights reserved.

Challenges with minimising mercury pollution in the small-scale gold mining sector: Experiences from the Guianas

This paper examines the barriers to mitigating mercury pollution at small-scale gold mines in the Guianas (Guyana, French Guiana and Suriname), and prescribes recommendations for overcoming these obstacles. Whilst considerable attention has been paid to analysing the environmental impacts of operations in the region, minimal research has been undertaken to identify appropriate policy and educational initiatives for addressing the mounting mercury problem. Findings from recent fieldwork and selected interviews with operators from Guyanese and Surinamese gold mining regions reveal that legislative incapacity, the region's varied industry policy stances, various technological problems, and low environmental awareness on the part of communities are impeding efforts to facilitate improved mercury management at small-scale gold mines in the Guianas. Marked improvements can be achieved, however, if legislation, particularly that pertaining to mercury, is harmonised in the region; educational seminars continue to be held in important mining districts; and additional outlets for disseminating environmental equipment and mercury-free technologies are provided.

Towards the abatement of environmental mercury pollution: An electrochemical characterization

Electrochemical experiments in acetic acid-acetate buffer (pH 4.5) are conducted in order to understand metallic and ionic mercury adsorption processes on the pyrite surface. The nature as well as the extent of the spontaneous interaction between pyrite and mercuric ions was evaluated. The spontaneous reduction of mercury species onto pyrite surface was confirmed. These results represent a first step for the use of mining wastes rich in pyrite for mercury pollution abatement. (c) 2005 Elsevier B.V. All rights reserved.

On the development of a mercury-free ternary aluminium anode for cathodic protection

The development of a new mercury-free ternary aluminum anode (CIFTAL) for cathodic protection of marine structures is described. The new anode demonstrated a current efficiency of 83.5% to 85.4% in a current density range of 5.6 to 166.7 mAdmˉ². The current efficiency remained practically stable at 1.4 mAdmˉ² over a test period of 300 days. The service trials of the anode on steel trawlers and aluminum (Indal M 57 S) sheathed wooden boats have shown satisfactory performance in terms of uniform dissolution, current efficiency and driving voltage. In the wake of legislations restricting the use of anodes containing mercury in an endeavor to control the mercury pollution of the near shore aquatic environment, the new anode (CIFTAL) with its stable current output and high current efficiency merits significance in marine cathodic protection.

Mercury (II) removal from aqueous solutions by microporous materials

O Mercúrio é um dos metais pesados mais tóxicos existentes no meio ambiente, é persistente e caracteriza-se por bioamplificar e bioacumular ao longo da cadeia trófica. A poluição com mercúrio é um problema à escala global devido à combinação de emissões naturais e emissões antropogénicas, o que obriga a políticas ambientais mais restritivas sobre a descarga de metais pesados. Consequentemente o desenvolvimento de novos e eficientes materiais e de novas tecnologias para remover mercúrio de efluentes é necessário e urgente. Neste contexto, alguns materiais microporosos provenientes de duas famílias, titanossilicatos e zirconossilicatos, foram investigados com o objectivo de avaliar a sua capacidade para remover iões Hg2+ de soluções aquosas. De um modo geral, quase todos os materiais estudados apresentaram elevadas percentagens de remoção, confirmando que são bons permutadores iónicos e que têm capacidade para serem utilizados como agentes descontaminantes. O titanossilicato ETS-4 foi o material mais estudado devido à sua elevada eficiência de remoção (>98%), aliada à pequena quantidade de massa necessária para atingir essa elevada percentagem de remoção. Com apenas 4 mg⋅dm-3 de ETS-4 foi possível tratar uma solução com uma concentração igual ao valor máximo admissível para descargas de efluentes em cursos de água (50 μg⋅dm-3) e obter água com qualidade para consumo humano (<1.0 μg⋅dm-3), de acordo com a legislação Portuguesa (DL 236/98). Tal como para outros adsorbentes, a capacidade de remoção de Hg2+ do ETS- 4 depende de várias condições experimentais, tais como o tempo de contacto, a massa, a concentração inicial de mercúrio, o pH e a temperatura. Do ponto de vista industrial as condições óptimas para a aplicação do ETS-4 são bastante atractivas, uma vez que não requerem grandes quantidades de material e o tratamento da solução pode ser feito à temperatura ambiente. A aplicação do ETS-4 torna-se ainda mais interessante no caso de efluentes hospitalares, de processos de electro-deposição com níquel, metalúrgica, extracção de minérios, especialmente ouro, e indústrias de fabrico de cloro e soda cáustica, uma vez que estes efluentes apresentam valores de pH semelhantes ao valor de pH óptimo para a aplicação do ETS-4. A cinética do processo de troca iónica é bem descrita pelo modelo Nernst-Planck, enquanto que os dados de equilíbrio são bem ajustados pelas isotérmicas de Langmuir e de Freundlich. Os parâmetros termodinâmicos, ΔG° and ΔH° indicam que a remoção de Hg2+ pelo ETS-4 é um processo espontâneo e exotérmico. A elevada eficiência do ETS-4 é confirmada pelos valores da capacidade de remoção de outros materiais para os iões Hg2+, descritos na literatura. A utilização de coluna de ETS-4 preparada no nosso laboratório, para a remoção em contínuo de Hg2+ confirma que este material apresenta um grande potencial para ser utilizado no tratamento de águas. ABSTRACT: Mercury is one of the most toxic heavy metals, exhibiting a persistent character in the environment and biota as well as bioamplification and bioaccumulation along the food chain. Natural inputs combined with the global anthropogenic sources make mercury pollution a planetary-scale problem, and strict environmental policies on metal discharges have been enforced. The development of efficient new materials and clean-up technologies for removing mercury from effluents is, thus, timely. In this context, in my study, several microporous materials from two families, titanosilicates and zirconosilicates were investigated in order to assess their Hg2+ sorption capacity and removal efficiency, under different operating conditions. In general, almost all microporous materials studied exhibited high removal efficiencies, confirming that they are good ion exchangers and have potential to be used as Hg2+ decontaminant agents. Titanosilicate ETS-4 was the material most studied here, by its highest removal efficiency (>98%) and lowest mass necessary to attain it. Moreover, according with the Portuguese legislation (DL 236/98) it is possible to attain drinking water quality (i.e. [Hg2+]< 1.0 μg⋅dm-3) by treating a solution with a Hg2+ concentration equal to the maximum value admissible for effluents discharges into water bodies (50 μg⋅dm-3), using only 4 mg⋅dm-3 of ETS-4. Even in the presence of major freshwater cations, ETS-4 removal efficiency remains high. Like for other adsorbents, the sorption capacity of ETS-4 for Hg2+ ions is strongly dependent on the operating conditions, such as contact time, mass, initial Hg2+ concentration and solution pH and, to a lesser extent, temperature. The optimum operating conditions found for ETS-4 are very attractive from the industrial point of view because the application of ETS-4 for the treatment of wastewater and/or industrial effluents will not require larges amounts of adsorbent, neither energy supply for temperature adjustments becoming the removal process economically competitive. These conditions become even more interesting in the case of medical institutions liquid, nickel electroplating process, copper smelter, gold ore tailings and chlor-alkali effluents, since no significant pH adjustments to the effluent are necessary. The ion exchange kinetics of Hg2+ uptake is successfully described by the Nernst-Planck based model, while the ion exchange equilibrium is well fitted by both Langmuir and Freundlich isotherms. Moreover, the feasibility of the removal process was confirmed by the thermodynamic parameters (ΔG° and ΔH°) which indicate that the Hg2+ sorption by ETS-4 is spontaneous and exothermic. The higher efficiency of ETS-4 for Hg2+ ions is corroborate by the values reported in literature for the sorption capacity of other adsorbents for Hg2+ ions. The use of an ETS-4 fixed-bed ion exchange column, manufactured in our laboratory, in the continuous removal of Hg2+ ions from solutions confirms that this titanosilicate has potential to be used in industrial water treatment.

Microbial community composition and mercury cycling in sediments of tagus estuary

Tese de doutoramento, Farmácia (Toxicologia), Universidade de Lisboa, Faculdade de Farmácia, 2016

IMPACT OF 2000-2050 CLIMATE CHANGE ON GLOBAL ATMOSPHERIC TRANSPORT AND DEPOSITION OF MERCURY

Since it is very toxic and accumulates in organisms, particularly in fish, mercury is a very important pollutant and one of the most studies. And this concern over the toxicity and human health risks of mercury has prompted efforts to regulate anthropogenic emissions. As mercury pollution problem is getting increasingly serious, we are curious about how serious this problem will be in the future. What is more, how the climate change in the future will affect the mercury concentration in the atmosphere. So we investigate the impact of climate change on mercury concentration in the atmosphere. We focus on the comparison between the mercury data for year 2000 and for year 2050. The GEOS-Chem model shows that the mercury concentrations for all tracers (1 to 3), elemental mercury (Hg(0)), divalent mercury (Hg(II)) and primary particulate mercury (Hg(P)) have differences between 2000 and 2050 in most regions over the world. From the model results, we can see the climate change from 2000 to 2050 would decrease Hg(0) surface concentration in most of the world. The driving factors of Hg(0) surface concentration changes are natural emissions(ocean and vegetation) and the transformation reactions between Hg(0) and Hg(II). The climate change from 2000 to 2050 would increase Hg(II) surface concentration in most of mid-latitude continental parts of the world while decreasing Hg(II) surface concentration in most of high-latitude part of the world. The driving factors of Hg(II) surface concentration changes is deposition amount change (majorly wet deposition) from 2000 to 2050 and the transformation reactions between Hg(0) and Hg(II). Climate change would increase Hg(P) concentration in most of mid-latitude area of the world and meanwhile decrease Hg(P) concentration in most of high-latitude regions of the world. For the Hg(P) concentration changes, the major driving factor is the deposition amount change (mainly wet deposition) from 2000 to 2050.

四角蛤蜊Mactra veneriformis对镉和汞污染胁迫的生理响应

本论文基于对我国沿海重金属污染加剧以及滩涂贝类资源衰退现象的关注，围绕典型滩涂贝类四角蛤蜊生物化学、细胞生物学和免疫学特征开展研究，调查了渤海湾天津近岸海域四角蛤蜊体内重金属含量和分布规律，以及四角蛤蜊对沉积物重金属的富集能力。室内模拟研究了四角蛤蜊对重金属镉和汞的富集能力及同化机制（assimilation mechanism）差异性，四角蛤蜊各组织对镉和汞的解毒机理和负载能力，以及重金属胁迫对四角蛤蜊血细胞结构和功能的损伤效应。研究结果可望为探讨四角蛤蜊受重金属胁迫细胞水平上的响应机制，揭示重金属污染和贝类资源衰退的关系，建立快速可靠的重金属污染生物标志物指标体系，开展生态健康评估和生境修复等提供科学依据。主要研究结果如下： 1．查明了渤海湾天津近岸四角蛤蜊体内和表层沉积物中Cd、Pb、Cu、Zn、Mn、Cr和Ni七种重金属的含量和周年时空分布特征；表层沉积物中Cd具有较强的污染程度和潜在生态风险，四角蛤蜊对重金属元素Cd和Pb具有较高的富集能力，对环境重金属污染具有很好的指示作用。 2．查明了Cd对四角蛤蜊在24h，48h和96h的半致死浓度（LC50）分别为15.96mg/L、5.15mg/L和2.38mg/L，汞的24h，48h和96h LC50分别为3.71mg/L，0.61mg/L和0.21mg/L。镉和汞对四角蛤蜊的安全质量浓度分别为0.0238mg/L和0.0021mg/L。 3．四角蛤蜊软体部对Cd和Hg的富集能力有显著差异。暴露过程中，四角蛤蜊软体部Cd和Hg的增加量分别为0.12-7.7µg/g和0.002-0.024µg/g，富集率分别为0.3-6.2%和0.11-0.68%，吸收率常数分别为0.07-1.10和0.001-0.005。 4．四角蛤蜊受Cd和Hg胁迫后，外套膜、鳃和肝胰腺的金属硫蛋白（MT）含量均在暴露浓度和胁迫时间上都有极显著变化。组织内MT含量的大小关系为：肝胰腺＞鳃＞外套膜。肝胰腺可以作为双壳贝类MT重金属污染指示研究的目标组织。四角蛤蜊对Cd和Hg不同的解毒机制，导致组织中MT的表达含量和Cd胁迫显著相关，而与Hg胁迫无显著相关性。 5．四角蛤蜊肝胰腺和鳃中抗氧化系统酶、脂质过氧化产物、酸性磷酸酶（ACP）和碱性磷酸酶（ALP）在不同Cd胁迫浓度和暴露时间下有显著差异。与对照组相比，超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、谷胱甘肽过氧化物酶（GPx）的活力和丙二醛（MDA）含量均随着暴露时间的增加而增加，达到一个峰值，然后减低。而ACP和ALP活力则表现出先被抑制，然后升高的变化趋势。肝胰腺中CAT和GPx活力高于鳃，鳃中SOD和MDA含量高于肝胰腺，这种差异与两种组织不同的解毒机理有关。 6．重金属胁迫能够造成四角蛤蜊血细胞超微结构的损伤、溶酶体膜稳定性改变、微核和总畸形核生成，各种损伤均表现出明显的浓度依赖效应。2μg/L Hg暴露14天后，血细胞溶酶体膜中性红保持时间（NRR）、微核生成率（MN）和总畸形核生成率（TNA）与对照组相比没有显著差异。相同暴露时间下，25 μg/L Hg处理组血细胞NRR值低于25 μg/L Cd处理组，而MN和TNA值则相反，说明Hg胁迫对四角蛤蜊血细胞溶酶体膜具有较强的损伤作用。研究发现，NRR、MN和TNA三种指标对于衡量重金属污染对四角蛤蜊血细胞的毒性效应有很好的协同检测作用，可望作为有效的生物标志物在环境监测技术中得以应用。

Chemical Evaluation of Selected Organics and Trace Metals in the Mangrove Macroflora Of Cochin

Mangroves are considered to play a significant role in global carbon cycling. Themangrove forests would fix CO2 by photosynthesis into mangrove lumber and thus decrease the possibility of a catastrophic series of events - global warming by atmospheric CO2, melting of the polar ice caps, and inundation of the great coastal cities of the world. The leaf litter and roots are the main contributors to mangrove sediments, though algal production and allochthonous detritus can also be trapped (Kristensen et al, 2008) by mangroves due to their high organic matter content and reducing nature are excellent metal retainers. Environmental pollution due to metals is of major concern. This is due to the basic fact that metals are not biodegradable or perishable the way most organic pollutants are. While most organic toxicants can be destroyed by combustion and converted into compounds such as C0, C02, SOX, NOX, metals can't be destroyed. At the most the valance and physical form of metals may change. Concentration of metals present naturally in air, water and soil is very low. Metals released into the environment through anthropogenic activities such as burning of fossils fuels, discharge of industrial effluents, mining, dumping of sewage etc leads to the development of higher than tolerable or toxic levels of metals in the environment leading to metal pollution. Of course, a large number of heavy metals such as Fe, Mn, Cu, Ni, Zn, Co, Cr, Mo, and V are essential to plants and animals and deficiency of these metals may lead to diseases, but at higher levels, it would lead to metal toxicity. Almost all industrial processes and urban activities involve release of at least trace quantities of half a dozen metals in different forms. Heavy metal pollution in the environment can remain dormant for a long time and surface with a vengeance. Once an area gets toxified with metals, it is almost impossible to detoxify it. The symptoms of metal toxicity are often quite similar to the symptoms of other common diseases such as respiratory problems, digestive disorders, skin diseases, hypertension, diabetes, jaundice etc making it all the more difficult to diagnose metal poisoning. For example the Minamata disease caused by mercury pollution in addition to affecting the nervous system can disturb liver function and cause diabetes and hypertension. The damage caused by heavy metals does not end up with the affected person. The harmful effects can be transferred to the person's progenies. Ironically heavy metal pollution is a direct offshoot of our increasing ability to mass produce metals and use them in all spheres of existence. Along with conventional physico- chemical methods, biosystem approachment is also being constantly used for combating metal pollution