Bioaccumulation of metals in Eisenia fetida after exposure to a metal-loaded bauxsol™ reagent

The present sudy investigated the acute toxic effects of a metal-loaded Bauxsol^™ reagent (MLBR), containing more than 6,450 mg kg⁻¹ of bound metal, on the earthworm Eisenia fetida. Bauxsol is manufactured by Virotec Global Solutions of Gold Coast, Queensland, Australia. The E. fetida were exposed to 0, 10, 20, 40, 60, and 80% treatments of MLBR plus cow manure for 28 d. Good motility and no mortality of E. fetida were found in all treatments after 28 d of exposure. The greatest bioaccumulation of metals by E. fetida occurred in the 20 and 40% MLBR treatments. The bioaccumulation of metals in the worms and bioaccumulation factors (BAFs) were less than the reported toxicity thresholds to cause mortality and less than the reported BAF for moderately contaminated soils, indicating that metals bound to Bauxsol reagents are mostly nonbioavailable. Analyses of the 20% MLBR treatment at 28 d using a sequential extraction procedure showed that more than 95% of the metals are bound within the Fe/Mn oxide fractions. However, changes occurred in metal fractionation after exposure to E. fetida for Cd/Cr, and Fe/Mn. The data also showed that the exchangeable (1 M MgCl₂) and the toxicity characteristic leaching procedure extractant are useful as indicators of metal bioavailability from MLBR to E. fetida.