The concentrations of
organotin compounds in the aquatic environment of Maizuru Bay and their spatial distribution are discussed. The concentrations of
tributyltin (TBT) compounds in water samples ranged from 0.001 to 0.002 microg l(-1), and
monobutyltin compounds were the dominant species among the butyltin compounds. TBT concentrations in Maizuru Bay are low compared with other coastal waters of Japan. Drastic differences in TBT concentrations were not observed among the Maizuru Bay sites.
Phenyltin compounds were not detected in the water samples. Concentrations of TBT and
triphenyltin (
TPT) in sediment from Maizuru Bay ranged, respectively, from 0.9 to 11 microg kg(-1), from 0.2 to 17 microg kg(-1) dry weight (dw). TBT concentrations in Maizuru Bay were lower than those in other coastal areas of Japan.
TPT concentrations were greater than TBT concentrations in the fishing port. The concentrations of TBT and
TPT in blue mussels (M. galloprovincialis) from Maizuru Bay were in the range of 2.4 to 9.3 microg kg(-1) and 0.2-13 microg kg(-1) wet weight (ww), respectively. A tolerable average residue level (TARL) was estimated at 74.8 microg kg(-1) from a tolerable daily intake (TDI) of 0.25
bis(tributyltin)oxide microg kg(-1)
body weight day(-1). TBT concentrations detected in blue mussel samples were lower than the TARL values. The acceptable concentration of
TPT, which were calculated using acceptable daily intake instead of TDI, was 127 microg kg(-1). Concentrations of
TPT in blue mussel samples were also lower than the TARL. TBT compounds in blue mussel samples were at similar levels among the various sampling sites, indicating that TBT is not currently being used in ship hull paints; the ratios of degradation products of TBT and
TPT were greater than those of the parent compounds. Concentrations of alternative
biocides in water samples were also investigated in the bay. Although
Sea-Nine 211, M1, and Pyrithiones were not detected,
Diuron and
Irgarol 1051 were detected at 0.010-0.257 and at 0.002-0.018 microg l(-1), respectively. Concentrations of
Diuron were great in the shipping route and near the shipyard, whereas the concentration of
Irgarol 1051 was great at the fishing port. Concentrations of
Diuron and
Irgarol 1051 in sediment from Maizuru Bay ranged, respectively, from <0.08 to 12, from <0.08 to 9.8 microg kg(-1) dw, respectively. Despite being a semi-enclosed bay, we found that sediment in Maizuru Bay is not contaminated by alternative
biocides to the degree found in other coastal areas.
Copper concentrations of sediment were at ordinary levels, and those of blue mussels were slightly lower than those reported previously in other coastal areas of Japan. In both the sediment and blue mussels, there was no correlation between the presence of
copper and antifouling
biocides.