Mass stabilisation and leaching characteristics of organotins from contaminated dredged sediments

Organotins including tributyl tin (TBT) are an effective biocide that were widely used to prevent or inhibit the growth of marine invertebrates on a ship's hull. The widespread use of these, however, has created a lasting legacy of TBT-contaminated sediments the world over. Here, experiments assessing the unconfined compressive strength and leach performance of various binders on the stabilsation of organotin contaminated estuarine sediments are demonstrated using monolithic semi-dynamic leach tests. In addition to traditional binders such as Ordinary Portland Cement (OPC), sediment amendments to increase the organic content (OC) using protein powder from Cannabis sativa L. (hemp) plant are kinetically modelled to determine the long-term leachability of organotins. Results show that after 120 days of continuous testing, the OPC +hemp amended monolith cumulatively leached similar to 68 mu g Sn/m(2) TBT with the control (OPC only) performing worst leaching similar to 180 mu g Sn/m(2) TBT. Long-term kinetic modelling of the data indicated that the control would leach a cumulative maximum of similar to 327 mu g Sn/m(2) TBT compared to only similar to 68 mu g Sn/m(2) TBT for the OC amended sample well below the Finnish guideline maxima of 672 mu g Sn/m(2) TBT.

Automated summary

This study demonstrates the evaluation of various binders for the solidification of organotin contaminated estuarine sediments, and simulates the long-term leachability of organotins using the amendment of organic content. The results show that the binder amended with hemp performs the best in terms of leachability of organotins, significantly below the maximum limit set by relevant guidelines.