Three Bench-scale Tests Designed to Destroy Tributyltin (TBT) in Marine Sediments from North Queensland, Australia

Abstract

Organotin compounds, such as tributyltin (TBT), were used as antifouling biocidal agents in ship maintenance throughout the world prior to 2000. As a consequence, TBT has accumulated in marine sediments of some harbours, rivers and ports, and in and around shipyards, dry-docks and marinas. Organotin-contaminated marine sediments, when left undisturbed, pose little risk to the local environment or society, however, due to its toxic nature, TBT can pose a significant risk to the marine environment, groundwater, and potentially human health if contaminated marine sediments are dredged and left untreated on land or disposed to landfill, and disturbance through dredging can liberate TBT into the water column. Both scenarios can provide pathways for dissemination and contamination. Given the low allowable concentrations of TBT in marine sediments, the need for sustainable management and treatment of TBT is imperative. However, despite a worldwide effort to find effective treatment strategies for TBT in marine sediments, few examples exist which actually destroy the TBT molecule. For this reason, TBT is considered one of the world’s most persistent organic pollutants and is stable when in-situ sediments are left at the bottom of ports and harbours. Two samples of contaminated marine sediment were excavated from a slipway in far North Queensland and analysed for TBT and other contaminants. Each sample was then subjected to one of three bench-scale tests: Test 1 a treatment of six oxidising and/or immobilizing chemical agents; Test 2 thermo-chemical treatment; and Test 3 thermal treatment only. The six agents in Test 1 had little or no impact on total TBT, leachable TBT, water soluble TBT, or total petroleum hydrocarbons (TPH), however, the combined thermal and chemical treatment used in Test 2 and the thermal treatment used in Test 3 reduced total TBT, leachable TBT, water soluble TBT, and TPH by >99%.