Degradation of the tributyltin compounds by the microorganisms in water and sediment collected from the harbour area of Osaka City, Japan

Abstract

Surface water and sediment samples were collected from four stations in harbour area of Osaka City and the concentrations of butyltin compounds were determined. Tributyltin compounds (TBT) in surface water ranged from 0.002 to 0.033 mg liter −1. TBT in sediment samples were measured in the range of 0.002–0.966 mg (kg dry) −1. The highest concentrations of TBT in surface water and sediment were found in a marina and the zone of poor flushing. The degradation of butyltin compounds was surveyed by the river die-away method and the difference of degradation rate by microorganisms in water was evaluated in each station. The TBT concentration decreased dearly with the culturing period among all stations. Though the concentration of TBT in marina was 0.16 μg liter −1 after 42 days, TBT was not detected after 18 days in the other sites. Degradation of TBT by the microorganisms isolated from sediment in four stations was also investigated. The degradation process of TBT by the microorganisms from sediment was similar to that in water. Namely, TBT was degraded to DBT and MBT during the culture period. The degradation of TBT by microorganisms in water was compared to that from sediment. The microorganisms in water degraded TBT rather faster than those from sediment in spite of the fact that contamination level of TBT is rather higher in sediment than in water samples.