Nelson Belzile

Antimony in the environment: a review focused on natural waters: II. Relevant solution chemistry

This paper discusses the main characteristics of the solution chemistry of antimony in relation to its behaviour and fate in natural waters. It is based on a careful and systematic examination of a comprehensive collection of solution equilibrium and environmentally oriented studies, some published more than 100 years ago. General principles are outlined and main unknowns highlighted. Existing information on antimony reactivity in solution is scarce and often relatively old. Studies performed under conditions relevant to natural water conditions are particularly scant. D 2002 Elsevier Science B.V. All rights reserved.

Selenium and mercury in organisms: Interactions and mechanisms

This paper reviews the growing literature dealing with the antagonistic effect of selenium (Se) compounds on the toxicity of mercury (Hg) compounds in higher animals and organisms present in the aq...

Antimony in the environment : knowns and unknowns

Environmental context. Antimony first attracted public attention in the mid-1990s amid claims that it was involved in Sudden Infant Death Syndrome. A substantial number of papers have now been published on the element and its behaviour in the natural environment. However, many key aspects of the environmental chemistry of antimony remain poorly understood. These include critical areas such as its ecotoxicology, its global cycling through different environmental compartments, and what chemical form it takes in different environments. More focussed research would help the situation. The present review highlights several areas of environmental antimony chemistry that urgently need to be addressed. Abstract. The objective of the present article is to present a critical overview of issues related to the current state of knowledge on the behaviour of antimony in the environment. It makes no attempt to systematically review all published data. However, it does provide a list of the main published reviews on antimony and identifies subjects where systematic reviews are needed. Areas where our knowledge is strong – and the corresponding gaps – in subjects ranging from total concentrations and speciation in the various environmental compartments, to ecotoxicity, to cycling between compartments, are discussed, along with the underlying research. Determining total antimony no longer poses a problem for most environmental samples but speciation measurements remain challenging throughout the process, from sampling to analysis. This means that the analytical tools still need to be improved but experience shows that, to be useful in practice, this should be directly driven by the requirements of laboratory and field measurements. Many different issues can be identified where further research is required, both in the laboratory and in the field, the most urgently needed studies probably being: (i) long-term spatial and temporal studies in the different environmental compartments in order to collect the data needed to establish a global biogeochemical cycle; (ii) laboratory studies of antimony interactions with potential natural binders; (iii) reliable ecotoxicological studies.

Inhibition of pyrite oxidation by surface treatment

Abstract Pyrite samples were analyzed from two distinct locales with the intent of determining the extent of oxidative inhibition occurring in the presence of a passivating agent. Each sample was exposed to air and 9% H 2 O 2 as oxidizing agents over specific time periods with and without the presence of an iron oxide layer on the pyritic surface. The samples were submitted to passivating agents which created reversible interactions protecting and altering the surface. The type of coating agent (acetyl acetone, humic acids, ammonium lignosulfonates, oxalic acid or sodium silicate) and the quality of the surface prior to oxidation were used to determine the effectiveness of the passivating agents. Hydrogen peroxide was utilized to provide a long-term overview of the results because of its harshness as an oxidizing agent. The air oxidation results are linked to the trend shown by the peroxide results and, in each sample type, the use of passivation (especially with pre-oxidation) proved to be effective. In the presence of peroxide with pre-oxidative treatment, the acetyl acetone was able to reduce oxidation by 53% in the NWT sample (22% in the K.C. sample) and sodium silicate reduced oxidation by 55% in the K.C. sample (42% in the NWT sample).

High performance liquid chromatography coupled to atomic fluorescence spectrometry for the speciation of the hydride and chemical vapour-forming elements As, Se, Sb and Hg: A critical review

We present the most recent applications of high performance liquid chromatography (HPLC) hyphenated to hydride generation or chemical vapour generation and atomic fluorescence spectrometry (HG/CVG-AFS), for the determination and speciation of the selected hydride-forming elements arsenic (As), selenium (Se) and antimony (Sb) and the chemical vapour-forming metal Hg. The review focuses on sample preparation, post-column treatments and on the applications of this technique to various liquid and solid samples. This review also intends to discuss some limitations associated to HPLC-HG/CVG-AFS due to the necessity on post-column treatments, including the oxidation of organo-element compounds and the pre-reduction to a suitable valence. Nevertheless, the hyphenated technique HPLC-HG/CVG-AFS remains an efficient, sensitive and affordable approach to perform speciation of the four studied elements as shown by the variety of applications presented and discussed in this review.

Natural attenuation processes applying to antimony: A study in the abandoned antimony mine in Goesdorf, Luxembourg

The processes leading to the attenuation of the antimony concentration in the water draining from the abandoned antimony mine in Goesdorf, Luxembourg, have been studied. Antimony has been mined in Goesdorf since Roman times from a stibnite-rich mesothermal vein system hosted in metasedimentary schist. The draining waters have pH values between 7 and 8 because the mineralization itself contains calcite and dolomite. This study combines the identification of minerals in the supergene zone with the application of bulk techniques (e.g., measurement of antimony in the waters of the adit and the creek draining the mine, sediment sequential extractions) over a period of five years. Antimony concentrations in the water that leaves the supergene zone are controlled by the dissolution of stibnite and the subsequent formation of Sb(III) oxides and sulphates. The relative proportions of the main secondary minerals can be qualitatively estimated as follows: 70% valentinite, 15% senarmontite and 12% sulphates (coquandite, klebelsbergite and peretaite). Further antimony attenuation along the adit and the creek that drain the mine waters is due partly to dilution, through mixing with waters that have not been in contact with the ore, and partly to sorption onto amorphous iron and manganese oxides present in the colluvial sediments.

Determination of mercury by continuous flow cold vapor atomic fluorescence spectrometry using micromolar concentration of sodium tetrahydroborate as reductant solution

Systematic experiments were conducted to evaluate and compare the analytical figures of merit of two reducing agents (SnCl2 and NaBH4) in a continuous flow cold vapor atomic fluorescence mercury analyzer. It was found that sodium tetrahydroborate can efficiently reduce Hg2+ in various environmental samples at a concentration as low as 10 microM (ca. 3.8 x 10(-5)% w/v). Most commonly encountered transition metals (Fe2+, Fe3+, Zn2+, Cu2+, Ni2+, Pb2+ and Cr3+) did not interfere with total Hg determination. No interference from hydride-forming elements (Se4+, Sb3+ and As3+) was observed. Interference caused by Mn2+ and Ag+ could be readily removed by dilution and by using appropriate modification of the reaction matrix. A higher concentration of NaBH4 (0.1 M) is stable for I month when stored in the NaOH matrix (0.2 M) and at low temperature (4 degrees C). A working solution of NaBH4 can be freshly prepared by dilution. With NaBH4, the whole continuous flow system is kept clean much more easily as no precipitate is formed, which in turn considerably reduces memory effects, simplifies analytical operation and reduces the chemical cost six-fold.

Human Exposure to Antimony: I. Sources and Intake

Human beings are exposed to antimony through air, water, and food sources. The authors present and critically discuss the literature information on Sb concentrations in those corresponding sources and intake by humans. Concentrations in air particulate matter vary from a few pg m−3 in remote areas to a few ng m−3 in urban areas and much more in some contaminated sites. Most Sb concentrations in drinking water are below the 1.0 μg·L−1 level, except for some bottled waters that can show higher level under extended conditions of storage. All concentrations in food fall generally well below the 1.0 μg·g−1 on a dry weight basis, suggesting little concern in terms of Sb uptake from this category.

Inverse relationships between selenium and mercury in tissues of young walleye (Stizosedion vitreum) from Canadian boreal lakes.

The concentrations of total mercury (Hg), methylmercury (MeHg) and total selenium (Se) were determined in muscle, liver and brain tissues of young-of-the-year walleye (Stizosedion vitreum) specimens collected from 8 boreal lakes that are located within 107km around the Sudbury smelters in Ontario, Canada. Dry weight basis concentrations of Hg were highest in muscle and lowest in brain (p<0.05), those of MeHg were higher in muscle than in liver and brain but there was no significant difference between liver and brain (p<0.05). The highest Se concentrations were found in liver and the lowest in brain (p<0.05). Considering the biomass of the studied tissues, muscle was the part of the body where most of Hg, MeHg and Se were accumulated. In fish muscle, the percentage of MeHg over Hg was the highest and this percentage was the lowest in liver. The concentrations of Hg, MeHg and Se in the studied tissues were closely related to the concentrations of total dissolved Se in lake waters which vary with the distance of the lakes from the smelters. Thresholds of Se concentrations in tissues were revealed (6.2, 12.0 and 3.5mgkg(-1) dry wt., for muscle, liver and brain, respectively), above which a significant reduction of MeHg concentrations was observed in all studied tissues compared to lower Se levels in the same tissues. Based on the collected information and data analysis, possible mechanisms for the biological processes behind the observed inverse relationships between Se and Hg in fish tissues are discussed.

Selenium Bioaccumulation in Freshwater Organisms and Antagonistic Effect against Mercury Assimilation

We present evidence of selenium bioaccumulation at lower levels of the aquatic food chain and its antagonistic effect against mercury and methyl mercury assimilation in the aquatic food web. Most of our studies were carried out in freshwater lakes of the mining region of Sudbury, Ontario, Canada where the presence of metal smelters has introduced elevated levels of selenium in the surrounding terrestrial and aquatic ecosystems. The studies with different types of aquatic organisms demonstrate a consistent inverse relationship between concentrations of mercury/methyl mercury and selenium in whole bodies (zooplankton, benthic invertebrates, mayflies and amphipods, beetle larvae and newly hatched perch) or in muscle, liver and brain (perch and walleye). This antagonistic effect was also observed in laboratory controlled experiments with the incubated soil and surface water bacterium Pseudomonas fluorescens. We also present some information on Se accumulation at different levels of the food web with samples c...