The sorption efficiency and possible secondary effects of activated carbon (AC) (ø 63-200 μm) was studied with Lumbriculus variegatus in three PCB contaminated sediments applying long AC-sediment contact time (3 years). AC amendment efficiently reduced PCB bioavailability as determined with both, L. variegatus bioaccumulation test and passive samplers. However, dose related secondary effects of AC on egestion rate and biomass were observed (applied doses 0.25% and 2.5% sediment dry weight). The sorption capacity and secondary effects remained similar when the experiments were repeated after three years of AC-sediment contact time. Further, transmission electron microscopy (TEM) samples revealed morphological changes in the L. variegatus gut wall microvilli layer. Sediment properties affected both sorption efficiency and secondary effects, but 2.5% AC addition had significant effects regardless of the sediment. In, conclusion, AC is an efficient and stable sorbent to decrease the bioavailability of PCBs. However, sediment dwelling organisms, such as Oligochaete worms in this study, may be sensitive to the carbon amendments. The secondary effects and possible morphological changes in benthic organisms should not be overlooked as in many cases they form the basis of the aquatic food webs.

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This research investigated the effectiveness of phosphorus (P) and organic matter (OM) as possible in situ remediation techniques for metal contaminated soils. The study was designed to determine the bioavailability of Pb, Zn, and Cd individually and in combination to the earthworm Eisenia fetida in an artificial soil amended with varying levels of P and OM. A toxicokinetic approach using bioaccumulation factors and uptake rate coefficients was used to assess the bioavailability of the heavy metals. Overall, earthworms in P‐amended soils showed significantly reduced Pb levels in the individual and mixture experiments, while Zn and Cd bioavailability was not reduced. X‐ray diffraction analyses indicated that pyromorphites were formed with P amendment, thereby reducing the solubility and bioavailability of Pb within the soil. In contrast, the OM soil amendments increased bioavailability of Pb in the individual experiment and decreased it in the mixture experiment. The results of this study suggest that P amendments may be a viable technique to remediate Pb contaminated residential soils and that earthworm bioassays represent a biologically relevant measure of metal availability in soil.

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