Contrasting effects of black carbon amendments on PAH bioaccumulation by Chironomus plumosus larvae in two distinct sediments: Role of water absorption and particle ingestion

Two sediment matrices with different characteristics were amended with chars from different sources for bioaccumulation assay with filter-feeding Chironomus plumosus larvae. Chars greatly decreased porewater concentrations of PAHs (Ciw) measured using polyethylene devices in sediments. In organic rich sediment matrix-based systems where suspended char particles were absent, PAH concentrations in larvae (CiB) were significantly correlated with Ciw, and there was no difference in water-based bioaccumulation factors (BAFs) between different treatments, suggesting that water absorption was the main contaminant uptake route for larvae. In organic poor sediment matrix-based systems where suspended char particles were present, poor Pearson correlation between CiB and Ciw was found, but there was a significant linear increase of BAF values with char contents, which indicated that ingestion of suspended char particles could also be important for PAH bioaccumulation. Therefore, we need to rethink of the effectiveness and risks for the application of black carbon to sediment/soil remediation. - Highlights: → Chars greatly decreased PAH porewater concentrations. → Without char suspension, PAH bioaccumulation depended on porewater concentrations. → With char suspension, ingestion could also be important for PAH bioaccumulation. - Contrasting effects of chars on PAH bioaccumulation by Chironomus plumosus larvae in two distinct sediments were attributed to the shift of main biouptake routes.