DISTRIBUTIONS OF BUTYLTINS IN THE SURFACE SEDIMENT OF ISE BAY, JAPAN

Concentrations of tri-n-, di-n-, and mono-n-butyltin (TBT, DBT, and MBT) were determined for surface sediments collected from 44 sites within Ise Bay, Japan. The concentrations of TBT, DBT, and MBT ranged from not detected (ND) to 0.11, ND to 0.073, and ND to 0.098 mug g 1 dry sediment, respectively, excluding one site near a shipyard (TBT concentration 0,54-1.1 mug g-1 dry sediment). The distribution patterns of the three butyltins were similar to each other. The concentration of TBT correlated to the organic carbon (OC) content of the sediment and did not correlate to the sediment particle size. The area with high concentration of butyltin extended from the eastern side of the middle of the bay toward the southwest to Tsu-Matsuzaka Port. This area had a high organic content area and corresponded to the downwelling zone simulated by a baroclinic three-dimensional hydrodynamic model. Another area with high butyltin concentrations, near Yokkaichi Port, was also located in the simulated downwelling zone. The area near Nagoya Port, which is in the simulated upwelling zone, had low butyltin concentrations, although the amount of TBT loading in Nagoya Port was estimated to be several times greater than that in Yokkaichi Port. The ratio of TBT to MBT decreased along the direction of surface flow from Yokkaichi Port to the middle of the bay. These results suggested that the amount of the TBT loading could not explain all of the distribution of the TBT concentration in the sediment, and that tidal bay circulations, hydrodynamically up- and downwelling, and surface flow affected it strongly.