Research Article Received: 15 August 2014,
Revised: 7 September 2014,
Accepted: 7 September 2014
Published online in Wiley Online Library: 7 November 2014
(wileyonlinelibrary.com) DOI 10.1002/jat.3078
Acute toxicity of 50 metals to Daphnia magna Akira Okamotoa, Masumi Yamamuroa and Norihisa Tatarazakoa,b* ABSTRACT: Metals are essential for human life and physiological functions but may sometimes cause disorders. Therefore, we conducted acute toxicity testing of 50 metals in Daphnia magna: EC50s of seven elements (Be, Cu, Ag, Cd, Os, Au and Hg) were < 100 μg l 1; EC50s of 13 elements (Al, Sc, Cr, Co, Ni, Zn, Se, Rb, Y, Rh, Pt, Tl and Pb) were between 100 and 1000 μg l 1; EC50s of 14 elements (Li, V, Mn, Fe, Ge, As, In, Sn, Sb, Te, Cs, Ba, W and Ir) were between 1,001 and 100,000 μg l 1; EC50s of six elements (Na, Mg, K, Ca, Sr and Mo) were > 100,000 μg l 1; and. 7 elements (Ti, Zr, Bi, Nb, Hf, Re and Ta) did not show EC50 at the upper limit of respective aqueous solubility, and EC50s were not obtained. Ga, Ru and Pd adhered to the body of D. magna and physically retarded the movement of D. magna. These metals formed hydroxides after adjusting the pH. Therefore, here, we distinguished this physical effect from the physiological toxic effect. The acute toxicity results of 40 elements obtained in this study were not correlated with electronegativity. Similarly, the acute toxicity results of metals including the rare metals were also not correlated with first ionization energy, atomic weight, atomic number, covalent radius, atomic radius or ionic radius. Copyright © 2014 John Wiley & Sons, Ltd. Keywords: Daphnia magna; metals; acute toxicity; physiological toxic effect; electronegativity
Introduction
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Metals are essential for human life and physiological functions. Some metals are essential elements required by humans, and most metals are used in electrical and electric equipment, cars and catalysts (Herincs et al., 2013; Wu et al., 2013; Singh and Rajaraman, 2014). Currently, solar power has been attracting attention as alternative energy to fossil fuels. Copper and the minor metals indium, gallium and selenium are used as semiconductors to increase the electric power generation rate of solar panels (Eisenberg et al., 2013). The lifetime of solar panels is said to be 20–30 years. Consequently, in the near future, metals in a large quantity of solar panels may be released as electric waste (E-waste) into the environment, although valuable materials (copper and other precious metals) will be collected from E-waste by dismantling, crushing and combustion (Huo et al., 2007; Leung et al., 2007; Man et al., 2011; Hu et al., 2013). Cr, Co, Zn, Cd, Cu, Ni and Pb are detected at high levels in dust in some developing countries (Madany et al., 1994; Banerjee, 2003; Wong et al., 2007a, 2007b; Leung et al., 2008, 2013; Lopez et al., 2011; Luo et al., 2012; Ren et al., 2013; Shi et al., 2013), for which recovery work is being conducted at present. In addition, increased usage of Sb as flame retardants has lead to increased metal levels in soil (Wong et al., 2007a, 2007b). As the demand for metals increases, care must be taken regarding environmental pollution. Toxicity testing has already been conducted for most metals detected in the environment. However, the toxicity of some metals is known to possibly change as a result of some chemical modality in solution including pH, hardness and dissolved organic carbon (DOC) (De Schamphelaere and Janssen, 2004). Thus, metal toxicity testing must be performed considering pH, hardness and DOC. However, few studies have conducted toxicity testing of a large number of elements under a unified condition until now. For the intercomparison of metal toxicities, test results under a unified condition are required. Data collected under different conditions cannot assay the correlation between toxicity and physicochemical constants. We conducted a metal toxicity test with D. magna. Daphnia magna has more sensitivity than fishes and phytoplankton
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and there are many studies of metal toxicity. Biesinger and Christensen (1972) reported acute and chronic toxicity testing of 20 metals under a unified condition and insisted on a correlation between their toxicity data and physicochemical constants. They found a correlation between acute/chronic toxicity results and electronegativity. However, only 20 types of metals were analyzed, which is insufficient to reach this conclusion. In this study, we conducted acute toxicity testing of 50 metals and calculated the correlation coefficient between acute toxicity and the physicochemical constants of these metals. Our study provided helpful information to elucidate differences between metals and differences in their toxic mechanisms.
Materials and Methods Test Species A single genetic stock of D. magna has been subcultured at the National Institute for Environmental Studies, Tsukuba, Japan for more than 20 years and was used for the present experiments. Female neonates (age < 24 h), produced by mature females (age ≥ 2 weeks), were subcultured every week. Daphnia magna was used for experiments after the acclimation of several generations. The water temperature for breeding was 21 ± 1°C, and the light/dark cycle was 16/8 h. Breeding was conducted in glass flasks using 35 adult daphnids per liter. Tap water in Tsukuba filtered with activated charcoal was used as breeding water, *Correspondence to: Norihisa Tatarazako, Environmental Quality Measurement Section, Research Center for Environmental Risk, National Institute for Environmental Studies, 16-2 Ogawa, Tsukuba, Ibaraki, 305-8506, Japan. Email:
[email protected] a
Graduate School of Frontier Science, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8561, Japan
b
Environmental Quality Measurement Section, Research Center for Environmental Risk, National Institute for Environmental Studies, 16-2 Ogawa, Tsukuba, Ibaraki, 305-8506, Japan
Copyright © 2014 John Wiley & Sons, Ltd.
Acute toxicity of 50 metals to D. magna and most organic matter was not included. Used breeding water was renewed every other day. Neonates were removed during water renewal. We obtained the green alga Chlorella vulgaris as a food source for daphnia from Chlorella Industry Co. Ltd. (Fukuoka, Japan), and it was diluted to 5 × 108 cell ml 1 and added to the cultivation media.
at 21 ± 1°C, 16 h light/8 h dark, and pH 6.5–8.5. Breeding water was used for test water. To adjust the pH, 1 N sodium hydroxide (96.0% pure; Wako) was used for In, Ta, Nb, Re, W, Sn, Sb, Zr, Bi, Table 1. Acute toxicity of 50 metals to D. magna. Salt used
Chemicals and Test Solutions The stock solutions were 99% pure lithium chloride (Wako Pure Chemical, Osaka, Japan), 99.9% pure beryllium sulfate tetrahydrate (Wako), 99.5% pure sodium(I) chloride (Wako), 99.5 magnesium(II) sulfate heptahydrate, 99.9 % pure aluminium(III) chloride(Wako), 99.5 % pure potassium(I) chloride(Wako), 99.0% pure calcium(II) chloride (Wako), 99.9% pure scandium(III) chloride hexahydrate (Strem Chemicals, Newburyport, MA, USA), 99% pure titanium(IV) chloride (Wako), 99% pure ammonium vanadate(V) (Wako), 99% pure sodium dichromate dihydrate (Wako), 99% pure manganese(II) chloride tetrahydrate (Wako), 99.9 % pure Iron(III) chloride hexahydrate(Wako), 99.5% pure cobalt(II) chloride hexahydrate (Wako), 99.99% pure nickel(II) chloride (Sigma-Aldrich, St. Louis, MO, USA), 99.5% pure copper(II) sulfate pentahydrate (Wako), 98% pure zinc(II) chloride (Wako), 99.9% pure gallium(III) chloride (Wako), 99.99% pure germanium(IV) chloride (Wako), 99.999% pure arsenic(III) trichloride (Wako), 98% pure selenium(IV) tetrachloride (Wako), rubidium(I) chloride(Wako), 99% pure strontium chloride hexahydrate (Wako), 99.99% pure yttrium(III) chloride hexahydrate (Sigma-Aldrich), 99.9% pure zirconium(IV) chloride (Sigma-Aldrich), 99.0% pure sodium molybdate(VI) dihydrate (Wako), 99.9% pure ruthenium(III) chloride n-hydrate (Wako), 95.0% pure rhodium(III) chloride trihydrate (Wako), 99.999% pure silver(I) nitrate (Sigma-Aldrich), 98% pure cadmium chloride 2.5 hydrate (Wako), 97.0% pure tin(IV) chloride (Wako), 99.999% pure cesium chloride (Sigma-Aldrich), 99.999% pure barium chloride (Sigma-Aldrich), 99.99% pure osmium chloride trihydrate (AlfaAesar, Ward Hill, MA, USA), 99% pure iridium(IV) chloride (Wako), 99.9% pure chloroplatinic acid hydrate (Sigma-Aldrich), 99% pure sodium tetrachloroaurate dihydrate (Sigma-Aldrich), 99.5% pure mercury(II) chloride (Wako), 99.999% pure thallium chloride (Alfa-Aesar), 1006 mg l 1 lead standard solution (Wako), and 99.5% pure bismuth nitrate pentahydrate (Wako), which were dissolved in distilled water. These solutions were added to breeding water for the experiments. The following were dissolved in breeding water: 99.995% pure niobium(V) chloride (Sigma-Aldrich), 99% pure palladium(II) chloride (Wako), 99.999% pure indium(III) chloride (Sigma-Aldrich), 99.99% pure antimony(III) chloride (Sigma-Aldrich), 99.995% pure tellurium(IV) oxide (Alfa-Aesar), 99.9% pure hafnium(IV) chloride (Sigma-Aldrich), 99.999% pure tantalum(V) chloride (Sigma-Aldrich), 99.99% pure tungsten(VI) chloride (Sigma-Aldrich) and rhenium(V) chloride (Sigma-Aldrich). These solutions were stirred for 24 h, and the supernatant was used for experiments. These were prepared according to a method of OECD GD23 as WAF (the Water Accommodated Fraction) (OECD, 2000). Of course, all substances are measured. Acute Toxicity Testing
J. Appl. Toxicol. 2015; 35: 824–830
6,300 23 1,600,000 290,000 930 340,000 870,000 250 a 5,700< 1,200 130 9,400 6,700 720 650 9.4 470 b 24,000 2,400 710 940 120,000 490 a 2,900< a 140< 1,500,000 b 290 b 0.91 3.6 1,800 6,200 4,100 1,200 5,800 11,000 a 9,700< a 4.6< 30,000 a 58,000< 8.0 3,000 150 29 0.65 410 280 a 13,000
