Heavy metal speciation and its biological consequences in a group of lakes polluted by a smelter, Flin Flon, Manitoba, Canada

• Published in: Applied geochemistry 1993, Vol.8, p.285-289
• Main Authors: Jackson, T.A., Klaverkamp, J.F., Dutton, M.D.
• Format: Article
• Language: English
• Subjects: Catostomus commersoni; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Esox lucius; Exact sciences and technology; Geochemistry; Pollution, environment geology; Soil and rock geochemistry
• ISSN: 0883-2927; 1872-9134
• DOI: 10.1016/S0883-2927(09)80052-8

Comparative study of lakes polluted with Cd, Zn and Cu from a smelter at Flin Flon, Canada showed that the availability of heavy metals to sedimentary micro-organisms and aquatic food-chain organisms depends on the abundance of DTPA-extractable (bio-available) metal species in the sediments rather than total metal concentrations. Microbial methylation of Hg and resulting accumulation of Hg by northern pike muscle are inhibited by DTPA-extractable Cd but are not significantly affected by total Cd. Similarly, the Cd content of water, plankton and pike liver, and the toxic effects of Cd on heterotrophic sedimentary microbes, are more strongly dependent on DTPA-extractable Cd than on total Cd concentrations in the sediments. The extractability of sediment-bound Cd with DTPA is enhanced by organic matter but is depressed if sulfide exceeds a critical concentration. The DTPA-extractable Cd fraction may include lipophilic complexes that accumulate in fish tissues over time, as suggested by an increasingly significant positive correlation between liver Cd and fork length in pike with increasing abundance of DTPA-extractable Cd. Although Cd is less abundant than Zn or Cu in the DTPA-extractable metal pool, it has the strongest toxic effect on microbial activity, the relative toxicity increasing in the order Zn < Cu < Cd. The results are consistent with inhibition of enzymes by preferential formation of Cd-ligand bonds stabilised chiefly by entropy effects owing to chelation. Among white sucker, concentrations of Hg in muscle tissue and Cd in liver tissue are not significantly dependent on DTPA-extractable Cd but are depressed by sedimentary sulfides and Fe oxyhydroxides, respectively. The contrast between the results for pike and sucker suggests differences in metal uptake pathways and kinds of metal species assimilated, reflecting the difference in the feeding habits of the two fish species.