Interactive effects of metals in mixtures on bioaccumulation in the amphipod Hyalella azteca.

Mixtures were produced of "equi-toxic" concentrations of 10 elements at the 4-week LC25 for Hyalella azteca. Bioaccumulation was determined in 1-week exposures. The first mixtures tested included seven elements; As, Cd, Co, Cr, Ni, Pb and Tl. Copper, Mn and Zn were not included in the initial tests due to potential confounding effects, such as regulation of Cu and Zn by H. azteca and the high concentrations of Mn required to be "equi-toxic", which might cause adsorption of metals to Mn hydroxides if these were formed. The second set of tests included the seven element mixture in combination with, Cu, Mn and Zn individually, the binary pairs, Cu-Mn, Cu-Zn and Mn-Zn; and the tertiary group Cu, Mn and Zn. Interaction factors (IF) were computed which quantified each element's impact on the bioaccumulation of the other nine. Cobalt, Cd and Ni bioaccumulation was significantly inhibited with increasing number of metals in the mixture. Arsenic bioaccumulation was enhanced with increasing number of metals in the mixture exposure. Lead bioaccumulation was enhanced by some mixture combinations. Bioaccumulation of Cr, Cu, Mn, Tl and Zn were not significantly affected by exposure to other metals.