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Characterization of Natural and Affected Environments
Biomagnification of Tantalum through diverse aquatic food webs Winfred Espejo, Daiki Kitamura, Karen Kidd, Jose E Celis, Shosaku Kashiwada, Cristóbal Galbán-Malagón, Ricardo Barra, and Gustavo Chiang Environ. Sci. Technol. Lett., Just Accepted Manuscript • DOI: 10.1021/acs.estlett.8b00051 • Publication Date (Web): 09 Mar 2018 Downloaded from http://pubs.acs.org on March 9, 2018
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Biomagnification of Tantalum through Diverse
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Aquatic Food Webs
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Winfred Espejoab, Daiki Kitamurac, Karen A. Kiddb‡, José E. Celisd, Shosaku Kashiwadac,
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Cristóbal Galbán-Malagóne, Ricardo Barraa, Gustavo Chiangb†*
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Center, University of Concepción, Casilla 160-C, Concepción, 4070386, Chile.
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Canadian Rivers Institute and Biology, Department, University of New Brunswick, 100 Tucker Park Road, Saint John, NB E2L 4L5, Canada.
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Department of Aquatic Systems, Faculty of Environmental Sciences and EULA-Chile
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Research Center for Life and Environmental Sciences, Toyo University, Oura, 374-0193, Japan.
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Department of Animal Science, Faculty of Veterinary Sciences, University of Concepción, Casilla 537, Chillán, 3812120, Chile.
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Departmento de Ecologia y Biodiversidad, Facultad de Ecologia y Recursos Naturales,
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Universidad Andres Bello, Santiago, 8370251, Chile.
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Present address:
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‡
Department of Biology & School of Geography and Earth Sciences, McMaster University, 1280 Main Street W., Hamilton, ON, L8S 4K1, Canada. †
MERI Foundation, Santiago, 7650720, Chile.
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*Corresponding author: Gustavo Chiang,
[email protected] 24 25 26 27 28 29 30 31
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Abstract
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Tantalum (Ta) is a Technology-Critical Element (TCE) that is growing in global
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demand because of its use in electronic and medical devices, capacitors, aircraft, and hybrid
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cars. Despite its economic relevance, little is known about its environmental concentrations
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and the trophodynamics of Ta in aquatic food webs have not been studied. Invertebrates
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and fishes from coastal marine food webs representing different climatic zones in
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northwestern Chile, western Chilean Patagonia, and the Antarctic Peninsula were sampled
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and analyzed for Ta. The trophic level (TL) of species was assessed with nitrogen stable
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isotopes (δ15N), and carbon stable isotopes (δ13C) were used to trace energy flow in the
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food webs. Levels of Ta varied among taxa and sites, with the highest values found in
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fishes (0.53 – 44.48 ng g-1dry weight) and the lowest values found in invertebrates (0.11 –
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7.80 n ng g-1dry weight). The values of δ13C ranged from -11.79 to -25.66 ‰. Ta
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biomagnified in all four aquatic food webs, with slopes of log Ta versus TL ranging from
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0.16 to 0.60. This has important implications as little is known about its potential toxicity
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and there may be increased demand for TCEs such as Ta in the future.
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Tantalum,
Biomagnification,
Trophic
Transfer,
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Keywords
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Technology-Critical Elements, Marine Organisms, Stable Isotopes.
Aquatic
Ecosystems,
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Introduction
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Tantalum (Ta) is a rare transition element that is highly corrosion-resistant and
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stable at high temperatures,1, 2 and it is increasingly used in technology related to renewable
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energies, electronics, the automotive and aerospace industries, and biomedicine.3, 4 World
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production of Ta has increased over the last two decades, although its extraction remains
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low (ca. 1000 metric tons per year) when compared to other elements.5 Although Australia,
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Brazil, Canada, Ethiopia and Nigeria have produced Ta, countries such as Burundi, Congo
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and Rwanda (65% of global production since 2014) have used it to finance illegal military
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operations during civil wars, dubbing it a “conflict mineral”.5, 6 Nonetheless, it is estimated
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that new uses for Ta will increase global demand and production4 but its environmental
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concentrations and fate are poorly characterized.7
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Published data on Ta levels in the environment are scarce, focusing mainly on
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mineralogical analysis and then abiotic matrices,7 with only a few reports on Ta in aquatic
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animals. Ascidians (Styela plicata) from Japanese waters had 100-410 µg g-1 dw Ta8
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whereas marine organisms from coastal areas of southern England ranged from 0.009 in
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mollusks to 2.3 µg g-1 dw in crustaceans.9 Chebotina et al. 10 reported the bioconcentration
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of Ta from water to phytoplankton (>101) and zooplankton (>107). Despite evidence of Ta
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bioaccumulation in aquatic organisms, the factors affecting its concentrations in different
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species have not been examined.
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Metals such as mercury, persistent organic pollutants and organotin compounds are
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known to biomagnify in diverse aquatic food webs to levels in upper-trophic-level fish that
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may pose a risk to fish consumers and the fish themselves.11-13 The trophic level (TL) of
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species is estimated from δ15N and frequently used to provide a measure of the relative
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trophic position of organisms within food webs.11 Levels of contaminants are regressed
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against TL to understand whether they biomagnify and these relationships can be compared
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among ecosystems differing in species composition, physical and chemical characteristics,
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and climatic zones.11, 12
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There is a lack of knowledge on the concentrations of Ta in biota and whether this
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element biomagnifies through aquatic food webs.7 This is important to address because of
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the likely increased use of Ta and the potential risk it may pose from dietary exposures.13
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The objectives of the present study were to determine the concentrations of Ta and the
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relative trophic level of aquatic organisms from marine coastal food webs across three
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climatic zones in Antarctica and Chile. The results show for the first time that there is an
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increase in Ta concentrations with increasing trophic level, and that its biomagnification
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occurred at sites differing in their physical and biological characteristics.
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Material and methods
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Field collections
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During the austral summer of 2015, four marine ecosystems with different climatic
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conditions were sampled in the following regions of the southern hemisphere (Figure 1):
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northwestern coast of Chile (Sector A), with a tropical hyper-desertic climate;14 western
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Chilean Patagonia (Sector B) with a climate classified as template hyper-oceanic;14 and the
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Antarctic Peninsula area (Sector C), which is classified as a cold desert.15 In northwestern
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Chile, samples were obtained from Pan de Azúcar Bay (26°09´S, 70°40´W). In Chilean
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Patagonia, samples were obtained from two sites: the first was off of La Leona Island
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(44°1´58ʺW, 73°7´56ʺW) and the second was at the mouth of the Marchant River
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(44°5´15ʺS, 73°5´6ʺW). In Antarctica, samples were obtained from Fildes Bay (62°12´S,
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58°58´W).
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Fishes and invertebrates were collected from each of the locations by SCUBA to
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ensure the collection of the selected species, as well as to minimize any impacts of
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sampling. At Pan de Azúcar Bay in northwestern Chile, 8 species of macroinvertebrates
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and 6 species of fishes were collected (N = 61; Supporting Table S1). In Chilean Patagonia,
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4 species of macroinvertebrates and 3 species of fishes were collected at the mouth of the
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Marchant River (N = 31), and 4 species of macroinvertebrates and 3 species of fishes were
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sampled at La Leona Island (N = 28; Supporting Table S2). At Fildes Bay in Antarctica, 9
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of both macroinvertebrate and fish species were sampled (N = 55; Supporting Table S3).
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Fish were anaesthetized with BZ-20 (Veterquimica), sacrificed by severing the spinal cord,
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and sampled for muscle tissues. Soft tissues of mollusks were collected and whole bodies
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of other macroinvertebrates were retained. All specimens were stored at -20°C until
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processed in the laboratory.
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Laboratory analyses
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Individual fish muscle and soft invertebrate tissues were freeze-dried until dry
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masses were constant and then were homogenized into a fine powder using a glass mortar
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and pestle pre-cleaned with 2% Conrad solution (Merck) for 24 h, washed with deionized
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water and HCl 1M and rinsed with distilled water.16 Sub-samples (0.2 g) were placed into
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50 mL Teflon beaker with 5 mL of ultrapure nitric acid and heated (at 110oC) until almost
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dry (about 3 h). Then 5 mL of ultrapure nitric acid and 1 mL of hydrogen peroxide were
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added and the mixture was heated again to near dryness (about 3 h). The residue was
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dissolved in 5 mL of 1% ultrapure nitric acid, filtered with glass fiber filter® (
