Evaluation of Bioavailable Tributyltin in the Sediment-Porewater System of Industrialized Korean Bays Using Ex Situ Passive Sampling and Partitioning Models

Abstract

Despite the complete ban on tributyltin (TBT), its ecological risk to benthic organisms remains a concern in coastal areas. To overcome limitations of partition coefficient-based prediction models in estimating bioavailable concentrations, this study developed, for the first time, an ex situ method using a low-density polyethylene (LDPE) passive sampler to measure the freely dissolved concentration (C-free) of TBT in sediment porewater. The equilibrium between LDPE and porewater was reached within 96 h. The total sedimentary concentrations (C-s) and C-free of TBT in three industrialized bays in Korea were measured together, ranging from 26.2 to 931 ng of Sn/g of dw and 6.20 to 1363 ng of Sn/L, respectively. Shipbuilding and repair activities were identified as major sources of TBT, and sediments remain secondary sources of porewater contamination over a decade after regulations. As TBT does not exhibit strong adsorption to black carbon, the two-carbon model could not effectively reduce uncertainty compared to the equilibrium partitioning (EqP) method. Comparisons with environmental threshold values indicated a high ecological risk for benthic organisms near contaminated hotspots. These findings underscore the high applicability of LDPE-based ex situ methods as reliable tools for monitoring freely dissolved TBT in sedimentary environments, as they effectively minimize the influence of complex sediment characteristics.