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Cadmium Concentrations of Crustacean Zooplankton of Acidified and Nonacidified Canadian Shield Lakes Norman D. Yan,*-+Gerald L. Mackle,t and Peter J. Dillon$ Zoology Department, University of Guelph, Guelph, Ontario, Canada, N I G 2W1, and Dorset Research Centre, Ontario Ministry of the Environment, P.O. Box 39, Dorset, Ontario, Canada, POA IEO
The cadmium in Epilimnetic zooplankton (Cd,) collected from 33 nonacidified, south central Ontario lakes, most of which were remote from local point sources of Cd emissions, ranged in concentration from 0.16 to 29.8 pg/g of dry weight. Levels were positively correlated with aqueous Cd concentrations and negatively correlated with lake water Ca, organic carbon, and total phosphorus concentrations. A stepwise regression model developed for these lakes overestimated Cd concentrations in zooplankton from acidic (pH O. All but three of these lakes are distant from large point sources of Cd emissions. We construct an empirical model with Cd, as the dependent variable in these lakes and determine if Cd, levels in acidified lakes (alkalinity 0.10). There are several obvious possible contributors to the substantial residual variance. The accuracy of the Cd, determinations could be improved (see Methods), particularly in the 20 lakes with 250 bm) biomass in Plastic Lake. Abbreviations indicate contributions of Cyclopoida (Cyclo), H . gibberum (H. g.), D . minutus (Di. min), and D . Pulex (Da. p.).
111) in their tendencies to accumulate Cd. Conclusions
Cadmium contamination of freshwaters is a growing environmental problem in North America (39), and one that is exacerbated by acidification of lake waters (8). Our results indicate that there is not a simple linear relationship between habitat Cd contamination, acidification, and Cd accumulation by freshwater zooplankton. Aqueous and planktonic Cd levels were positively correlated, but the best predictor of Cd, levels in the lakes with positive alkalinity was DOC. Cd levels in zooplankton of clear acidified lakes were unusually low, given their levels of DOC and aqueous Cd. An examination of seasonal changes in Cd levels in the zooplankton of Plastic Lake indicated surveys of the Cd concentrations in zooplankton should be conducted in the fall. Cd, levels in Plastic Lake were relatively stable at that time. The large range in Cd, levels recorded in the survey could not be explained by differences in zooplankton community structure among lakes. In contrast, seasonal changes in community composition were apparently a primary determinant of temporal changes in Cd, levels in Plastic Lake. Acknowledgments
Thanks to A. Bentley, C. Audette, and D. Evans for technical assistance, to M. Stephenson, B. Keller, and three anonymous reviewers for their helpful comments on the manuscript, and to D. Strickland for permission to sample lakes in Algonquin Park. Registry No. Cd, 7440-43-9; Ca, 7440-70-2; Fe, 7439-89-6; Mn, 7439-96-5; P, 7723-14-0; C, 7440-44-0.
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(23) Sprules,W. G.; Holtby, L. B.; Griggs, G. Can. J. 2001.1981, 59, 1611-1614. (24) Williamson, P. Oecologia 1980, 44, 213-220. (25) Yan, N. D.; Mackie, G. L.; Boomer, D. Sci. Total Enuiron. 1989, 87/88, 419-438. (26) Hinga, K. R.; Davis, P. G.; Sieburth, J. M. Limnol. Oceanogr. 1979,24, 536-540. (27) Rantala, R. T. T.; Loring, D. H. Znt. J . Enuiron. Anal. Chem. 1985, 19, 165-173. (28) Seepersaad, B.; Crippen, R. W. J . Fish. Res. Board Can. 1978, 35, 1363-1366. (29) Hatakeyama, S.;Yasuno, M. Bull. Enuiron. Contam. Toxicol. 1982, 29, 159-166. (30) Carney, G. C.; Shore, P.; Chandra, H. Enuiron. Res. 1986, 39, 290-298. (31) Poldoski, J. E. Enuiron. Sci. Technol. 1979, 13, 701-706. (32) Giesy, J. P.; Leversee, G. J.; Williams, D. R. Water Res. 1977, 11, 1013-1020. (33) Winner, R. W. Aquat. Toxicol. 1984,5, 267-274. (34) Campbell, J. H.; Evans, R. D. Sci. Total Enuiron. 1987,62, 219-227.
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Effect of Chemical Modification of Algal Carboxyl Groups on Metal Ion Binding Jorge L. Gardea-Torresdey, Mlchelle K. Becker-Hapak, James M. Hosea, and Dennis W. Darnall' Department of Chemistry, New Mexico State University, Las Cruces, New Mexico 88003, and Bio-recovery Systems, Inc., Las Cruces, New Mexico 88003
Carboxyl groups of biomasses of five different algal species were esterified by using acidic methanol. The extent of esterification was monitored by analyzing the amount of methanol released in the sample hydrolysates by gas chromatography. The effect and extent of esterification on copper(I1) binding to the biomass was determined at pH 5.0 and 2.0. All methanol-modified biomasses showed major decreases in copper(I1) and aluminum(II1) binding, although the amount of decrease varied among algal species. In contrast, gold(II1) binding capacities slightly increased as the algal carboxyl groups were esterified. These results indicate that carboxyl groups on algal cells are responsible for a great portion of copper(I1) and aluminum(II1) binding, and that they play an inhibitory role in gold(II1) binding. Introduction Recently, a great deal of attention has been focused upon the use of nonliving algal biomass as a potential industrial
tool for the extraction of toxic metal ions from wastewaters and mining effluents. The biosorption, or binding, of metal ions by the algal biomass arises from the coordination of 1372
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the ions to different functional groups in or on the algal cell. These coordinating groups (provided by proteins, lipids, and carbohydrates) include amimo, thioether, sulfhydryl, carboxyl, carbonyl, imidazole, phosphate, phenolic, hydroxyl, and amide moieties. The mechanism of binding of metal ions by inactivated algal biomass may depend on the species of metal ion, the algal organism, and the chemical composition of ,the metal ion solution. It has been demonstrated that algal biosorption of metal ions such as aluminum(III), copper(II), lead(II), and cobalt(I1) appears to occur via an ion-exchange process with metal cations competing with protons for negatively charged binding sites on the cell wall (1-4). Crist et al. (5) presented evidence that metallic cation binding to Vaucheria sp. occurred a t least in part by an ion-exchange mechanism and found hydrogen ions were displaced as metal cations were adsorbed by the alga. The binding sites were thought to be carboxyl groups as well as sulfates associated with polysaccharides and proteins. More recently Crist et al. (6) studied the interactions of metals and protons with the algae Vaucheria sp., Sporogyra, and Oedogonium sp. As the investigators had previously suggested, results indicated that metals adsorb to
0013-936X/90/0924-1372$02.50/0
0 1990 American Chemical Society
