Comparison of acid volatile sulphide, metal speciation, and diffusive gradients in thin-film measurement for metal toxicity assessment of sediments in Lake Chaohu, China

The toxicity of heavy metals in sediments is inseparable from their forms in the environment. Traditional sediment tox-icity assessment systems, such as total metals, dissolved metals in pore water, metals extracted by the Community Bu-reau of Reference procedure, and acid volatile sulphide (AVS)-simultaneously extracted metal (SEM), have their own limitations. This study revealed the horizontal and vertical distribution characteristics of AVS and SEM in Lake Chaohu and three typical groups of two-dimensional profiles of diffusive gradients in thin-film (DGT)-labile S(-II) were ob-tained at representative sampling sites. There was a positive correlation between DGT-labile S(-II) and AVS due to sulphate-reducing bacteria anda negative correlation due to the high sulphate reduction rate induced by high total or-ganic carbon. Moreover, there was no correlation between DGT-labile S(-II) and AVS when bioturbation was dominant in the sediments. To realise the application of DGT measurement in toxicity assessment of heavy metals in sediment through the sandwich relationship of DGT-labile metals vs. metals speciation vs. sediment toxicity assessment, the key relationship of DGT-labile metals vs. metals speciation was explored. DGT-labile Ni showed potential to reveal this relationship.

Automated summary

This study reveals the distribution characteristics of AVS and SEM in Lake Chaohu and investigates the relationship between DGT-labile S(-II) and AVS. It also explores the potential of DGT-labile Ni in revealing the relationship between DGT-labile metals and metals speciation.