Antimony: global environmental contaminant

In May of this year, the Institute of Environmental Geochemistry, University of Heidelberg, hosted an exciting scientific meeting: the First International Workshop on Antimony in the Environment. With approximately 60 participants attending from twenty countries, an accomplishment made possible to a great extent with the generous financial support of the German Research Foundation (DFG), there were stimulating presentations on almost all aspects of Sb in the environment: releases of naturally occurring Sb from rocks and minerals to surface waters; emissions of natural and anthropogenic Sb to the atmosphere; accumulation and fate of Sb in soils and sediments. The analytical chemistry of Sb had a very strong presence throughout the meeting, and methods were presented for the quantitative determination of Sb and its predominant chemical species in all of the most important environmental compartments.

Antimony is a fascinating element because of the antiquity of its discovery and use by man, its remarkable history in alchemy and early medicine, the number of modern industrial processes which employ Sb, the extremely broad range of high technology materials which contain it,¹ and the diversity of its chemical behaviour.^2,3 With respect to the predominant sources, biogeochemical behaviour and ultimate fate of Sb in the environment, there have been remarkably few studies compared to other potentially toxic metals such as Hg, Pb, Cd or As. The extensive review by Boyle and Jonasson⁴ outlined some of the gaps in our knowledge of the geochemical cycle of Sb. Since that time there has been growing evidence from a diversity of scientific disciplines that the environmental significance of Sb may have been underestimated by a considerable margin.⁵ There was an urgent need therefore, to bring together all of the scientists who are currently studying Sb in the environment under one roof, with representation invited from all of the relevant disciplines, to summarise the current state-of-the art of our understanding, and to identify the most important research needs: these were the objectives of the workshop.

According to the increasing concentrations, enrichments and accumulation rates of Sb in peat bogs from Europe and polar ice from the Canadian arctic, emissions of atmospheric Sb increased dramatically since the beginning of the Industrial Revolution. The peat bogs show that emissions of Sb have largely evolved parallel to Pb since the Roman Period, indicating the intensity and long history of atmospheric Sb contamination. The snow pit and ice core from Devon Island provides the first complete time series for Sb in the arctic. The ratio of Sb to Sc shows that natural Sb inputs to the Arctic are dwarfed by industrial sources, and that the enrichments of Sb have been increasing during the past few decades. The magnitude of the Sb enrichments in snow and ice from a remote region of the arctic indicates that this element, like Pb and Hg, is a global contaminant. Analyses of aerosols from Tokyo show that Sb is now the most highly enriched trace element in the PM2.5 fraction, with similar enrichments found in Buenos Aires and other major cities.

In soils, adsorption of Sb(V) onto the surfaces of iron oxyhydroxides is an important geochemical sink for Sb. Methylation of Sb appears to be more important than previously believed, and occurs under both oxic and anoxic conditions. Roadway soils are measurably impacted by Sb from brake pads, and part of this anthropogenic Sb appears to be extractable, raising the question of bioavailability. Studies of Sb speciation in plants yield varying proportions of Sb(V), Sb(III) and trimethyl antimony indicative of both rapid and complex biogeochemical cycling from soil to plant.

Many questions remain about the rates and mechanisms of redox-related transformations of Sb in natural waters. With the development of clean lab methods and protocols developed for polar snow and ice, it is now possible to determine the natural abundance of Sb in pristine groundwater. Reports of Sb in bottled waters often show much greater concentrations, possibly because Sb₂O₃ is used as a clarifying agent in the manufacture of glass as well as a catalyst in the manufacture of PET.

Health effects caused by occupational exposure to antimony compounds can be difficult to discern because of the common association between Sb, Pb, and As. However, now that reliable methods are available for measuring Sb in blood, perhaps this can be developed into a monitoring tool to evaluate exposed and unexposed populations.

Given the diversity of commercial and industrial uses of Sb, the number of different sources of Sb to the environment, its dynamic behaviour and the potential toxicity of a number of Sb species, further, more detailed studies of the biogeochemical cycle of this remarkable element are certainly warranted. This journal is an excellent medium for reporting the latest findings. Don’t change that channel.

William Shotyk

Institute of Environmental Geochemistry,

University of Heidelberg,Germany

 

Michael Krachler

Institute of Environmental Geochemistry,

University of Heidelberg,Germany

 

Bin Chen

Department of Environmental Health Sciences,

School of Public Health, University of Michigan, USA

Acknowledgements

The generous financial support of the German Research Foundation (DFG) is gratefully acknowledged. Thanks also to our sponsors: PS Analytical Ltd, LAMY, Capri-Sonne, and the City of Heidelberg.

References

1. J. Emsley, Nature’s Building Blocks. An A–Z Guide to the Elements, Oxford University Press, Oxford, 2001.
2. Environmental Inorganic Chemistry, Properties Processes and Estimation Methods, ed. I. Bodek, W. J. Lyman, W. F. Reehl and D. H. Rosenblatt, Pergamon Press, New York, Oxford, 1988.
3. M. A. Rish, Antimony, in Elements and their Compounds in the Environment, ed. E. Merian, M. Anke, M. Ihnat and M. Stoeppler, VCH, Weinheim, 2nd edn, 2004, pp. 659–670.
4. R. W. Boyle and I. R. Jonasson, J. Geochem. Explor., 1984, 20, 223–302.
5. W. Shotyk, M. Krachler and B. Chen, Anthropogenic Impacts on the Biogeochemistry and Cycling of Antimony, in Biogeochemistry Availability and Transport of Metals in the Environment, vol. 44 of Metal Ions in Biological Systems, ed. A. Sigel, H. Sigel and R. K. O. Sigel, M. Dekker, New York, 2005, pp. 172–203.

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