Article
Reference
Antimony in aquatic systems
FILELLA, Montserrat, et al.
Abstract
Antimony is ubiquitous in the environment. In spite of its proven toxicity, it has received scant attention so far. This communication presents an overview of current knowledge as well as the early results of a concerted, multidisciplinary effort to unveil antimony behaviour and fate in natural aquatic systems.
FILELLA, Montserrat, et al . Antimony in aquatic systems. Journal de Physique. IV Proceedings , 2003, vol. 107, p. 475-478
DOI : 10.1051/jp4:20030344
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DOI : 10. 1051/jp4 : 20030344
Antimony in aquatic systems
M. Filella, N. Belzile', Y.-W. Chen1, C. Elleouee, P. M. May3, D. Mavrocordatos4, P. Nirel5, A. Porquet6, F. Quentel7 and S. Silver8
Department of Inorganic, Analytical and Applied Chemistry, University of Geneva, 30 quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
1 Department of Chemistry and Biochemistry, Laurentian University, Sudbury, Ontario P3E 2C6, Canada
2 Laboratoire de Chimie Analytique, UMR 6521 du CNRS, Université de Bretagne Occidentale, 6 avenue V. Le Gorgeu, 29285 Brest, France
3 Chemistry, School of Mathematical and Physical Sciences, Murdoch University, Murdoch, WA 6150, Australia
4 Particle Laboratory, Swiss Federallnstitute for Environmental Science and Technology, Überlandstrasse 133, 8600 Dübendorf, Switzerland
5 Service Cantonal de l'Écologie de l'Eau, DIAE,
23 avenue Sainte-Clotilde, 1211 Genève 8, Switzerland
6 Department Microbiology & Immunology, University of Illinois at Chicago, 835 South Wolcott, Chicago, IL 60612-7344, U. S. A.
Abstract. Antimony is ubiquitous in the environment. In spite of its proven toxicity, it has received scant attention so far. This communication presents an overview of current knowledge as well as the early results of a concerted, multidisciplinary effort to unveil antimony behaviour and fate in natural aquatic systems.
1. WHY ANTIMONY ? Some facts :
. Sb occurs widely in the environment as a result of natural processes and human activities.
. Sb is an element that has received the barest attention in environmental studies.
. Sb is a pollutant ofpriority interest to USEPA [I] and EU [2].
. EU Classification Group is currently reviewing the possibility of R50-53 classification for Sb203.
Sb production and use have steadily increased. More important, uses of Sb have changed over the years : Traditionally, Sb was used in lead-antimony alloys. Bulk secondary antimony can be recovered as antimonial lead, most of which is regenerated and then consumed by the battery industry. Nowadays, the main form of Sb used is as Sb203 which cannot be recycled and is released into the environment.
180 C14 products
=0120 a Pdmary Sb : ioc nonmetai products
80...
C 140 ~ ; b. Prmars Sb : 40 retardants
0 Secondary 3eantimorial iead
1 M 1920 1940 1960 1980 2000 Year a) b)
Figure 1. a) World Sb production has steadily increased since 1900 [3]. b) Reported industrial consumption of Sb in the US in 2000 : about one-half of the Sb went into flame-retardants [3].
2. TOTAL (DISSOLVED) Sb IN NATURAL WATERS : WHAT THE LITERATURE SAYS [41 e Freshwaters : Sb concentrations vary from a few ng/L to a few mg/L. They reflect the wide range of
physicai and chemical conditions existing in freshwater systems and are very sensitive to the proxirriity of pollution sources.
. Sea water : Sb concentration in oceans is about 200 ng/L (Figure 2a). For some authors, Sb behaves as a conservative element, for others, as a mildly scavenged element.
. Estuaries : Sb behaviour depends on estuarine characteristics. In some cases, it behaves conservatively ; in others, it shows a mid-estuary maximum (Figure 2b).
Sediments : Sb concentrations in sediments rarely exceed 1 mg/g (dry weight). Most of the studies have been performed for polluted systems.
Soils : Sb concentrations are highly variable and depend strongly on the proximity to the source. The mean concentration for unpolluted soils is below 1 mg/g (dry weight). The highest concentrations tend to be found close to the surface.
. s 400 2000 600 O et500 L~ m
0'---*--- 500--'*''''''- 1600-
200 100 looo-
0-500-
1960 1960 1970 1980 1990 2000 0' "
Year of publication
Salinait) t a) b)
Figure 2. a) Evolution of total dissolved Sb concentrations in the oceans as a function ofthe year of publication. The mean value 1985-2000 is 184 (+ 45) ng/L [4]. b) Sb profiles in estuaries. Data from seven campaigns in four estuaries : large variation is observed [4].
3. Sb SPECIATION : EXPECTED AND FOUND
. According to thermodynamic equilibrium predictions, antimony exists as Sb (V) in oxic systems and as Sb (Ill) in anoxie ones [5]. However, the presence of significant amounts of Sb (IH) in oxic waters and of Sb (V) in anoxie ones has often been reported [4].
. It is generally accepted that Sb is present as " dissolved " in natural waters (Figure 3a). However, significant binding by metal oxides has been reported [6].
o 20 Z B . g. 0. "' ".
n.. rI'.
a) b)
Figure 3. a) Typical Sb distribution among size classes (data from [7]) : truly dissolved species predominate. b) Sb distribution in different size classes as a function of DOC percentage in the " dissolved fraction " [6] : no correlation observed.
. The significance of Sb complexation by NOM is controversial. A few studies [8-10] report significant
Sb-NOM interactions but most authors do not (Figure 3b). We have observed [11] that a significant
proportion of Sb in two Sudbury lakes was associated with a refractory fraction (operationally defined
by UV irradiation) consisting partially or entirely of organic matter (Figure 4).
10 10
0
Sb(lli+V) Sb (lll+Vl 20 % 20 t
1515 20-20 -25-25
0 0. 5 1 0 1 2
[Sb] (nM) [Sb] (nM) [Sb] (oM)
a) b)
Figure 4. Sb profiles in sediment porewaters. a) McFarlane Lake, pH = 8. 3-7. 2, DO (SWI)-5. 0 mg/L. b) Clearwater Lake, pH = 6. 2-5. 5, DO (SWI) = 9. 0 mg/L.
4. KINETICS OF Sb OXIDATION AND REDUCTION
Kinetic stabilisation of thermodynamically unstable species has been invoked by several authors to explain their presence in natural systems. It is well known that when a redox process is accompanied by hydrolysis reactions, as it is likely the case for Sb, the overall process can be much slower than expected. Several processes may influence oxidation and reduction rates, including chemical and photochemical transformations and biological mediated reactions. At present, kinetic information for redox reactions of Sb in natural waters is limited and rate constants are generally unknown. The few published observations are shown in Table 1.
Table 1. Published kinetic rate constants for Sb oxidation and reduction relevant in natural waters.
System Rate constants
(day-l) Reference
Sb (III) oxidation rate in the Black Sea 0. 008 [12]
(upper 100 m)
Sb (III) oxidation by [13]
synthetic iron oxyhydroxides 0. 887
natural iron oxyhydroxides 0. 574
synthetic manganese oxyhydroxides 2. 07 Sb (V) reduction rate in the Black Sea 1. 1xl0-6 [14]
(bottom waters)
Our recent results [15] on Sb (III) oxidation by H202 in NaCI solutions over a wide range of pH, ionic strength and oxidant concentrations show that the oxidation reaction is first order with respect to Sb (Ill) and H202. However, no oxidation is observed below the pH value at which speciation calculations [6] indicate that Sb (OH) 4- starts to be formed. In acidic media, the oxidation reaction is zeroth order with respect to Sb (Ill) and first order with respect H202 and chloride. Sb (Ill) concentrations were measured by anodic stripping voltammetry [16].
5. Sb AND BIOTA
Reported concentrations for Sb in freshwater and marine algae range from 0. 02 to 1 gg/g dry weight [4].
Although algae bioaccumulation and detoxifying mechanisms may be important because of their possible role in Sb redox speciation, not many studies have been performed. Kantin [17] sampled three marine algae
in San Diego Bay. In all of them, Sb (V) was the dominant species. Only Sargassum sp. was found to contain Sb (III) (up to 30%), thus demonstrating
an ability to form the reduced compound. This paper has been cited ever since as the justification of the often invoked biological origin of the Sb (lll) found in oxic waters.
However, phytoplankton uptake of Sb (OHk, the largely predominant Sb form in oxic systems, has not been reported. The different behaviour of antimonate, as compared to arsenate and phosphate, may be explained by the weaker Lewis acidity and larger ionic radius of antimonate. More recently, the algae Chlorella
vulgaris, isolated from an As-polluted environment, excreted 40% Sb (V) and 60% Sb (III) on exposure to Sb (III), suggesting that a change in oxidation state is used by this alga as a detoxifying mechanism [18].
It seems clear that the same genes (and encoded biochemical mechanism) conferring resistance towards As (Il), As (V) and Sb (bill) occur widely in Gram-negative and Gram-positive bacteria. Arsenate is
enzymatically reduced to arsenite by ArsC [19]. Arsenite and antimonite are " pumped " out by the membrane protein ArsB that functions alone chemiosmotically or with the additional ArsA protein as an ATPase. It
seems counter-productive to convert a less toxic compound to a more toxic one, but ArsC activity is closely coupled with efflux from the cells so that intracellular arsenite never accumulates. Nothing
seems to be known about Sb (V) resistance mechanisms. Research performed on Sb accumulation and intracellular
metabolism in relation to the treatment of human leishmaniasis with Sb (V) may be of value when trying to understand the role of biota in Sb environmental fate [20].
References
[I] United States Environmental Protection Agency. Water Related Fate of the 129 Priority Pollutants, vol.
1. (USEPA, Washington, DC, USA, 1979) Doc. 745-R-00-007.
[2] Council of the European Communities. Council Directive 76/464/EEC of 4 May 1976 on Pollution Caused by Certain Dangerous Substances Discharged into Aquatic Environment of the Community.
(Official Journal L 129, 1976) pp 23-29.
[3] http ://mineras. usgs. gov/minerals/
[4] Filella M., Belzile N. and Chen Y.-W., Earth-Sci. Rev. 57 (2002) 125-176.
[5] Filella M., Belzile N. and Chen Y.-W., Earth-Sci. Rev. 59 (2002) 265-285.
[6] Filella M. and May P. M., Geochim. Cosmochim. Acta 2003 (in press).
[7] Tanizaki Y., Shimokawa T. and Nakamura M., Environ. Sei. Technol. 26 (1992) 1433-1444.
[8] Gillain G. and Brihaye C., Oceanologica Acta 8 (1985) 231-235.
[9] Albéric P., Violier E., Jézéquel D. et al., Limnol. Oceanogr. 45 (2000) 1088-1096.
[10] Deng T., Chen Y.-W. and Belzile N., Anal. Chim. Acta 432 (2001) 291-302.
[11] Chen Y.-W., Deng T.-L., Filella M. and Belzile N., Environ. Sci. Technol. 2003 (in press).
[12] Cutter G. A., Mar. Chem. 40 (1992) 65-80.
[13] Belzile N., Chen Y.-W. and Wang Z., Chem. Geol. 174 (2001) 379-387.
[14] Cutter GA, Deep-Sea Research 38 (1991) S825-S843.
[15] Quentel F., Filella M., Elleouet C. and Madec C. L. (manuscript in preparation).
[16] Quentel F. and Filella M., Anal. Chim. Acta 452 (2002) 237-244.
[17] Kantin R., Limnol. Oceanogr. 28 (1983) 165-168.
[18] Maeda S., Fukuyama H., Yokoyama E. et al., Applied Organomet. Chem. 11 (1997) 393-396.
[19] Silver S., J. Industrial Microbiol. Biotechnol. 20 (1998) 1-12.
[20] Shaked-Mishan P., Ulrich N., Ephros M. and Zilbersten D., J Biol. Chem. 276 (2001) 3971-3976.
