The spatial and temporal behaviours of the organotin compounds (OTCs) (butyl- and phenyltin) were investigated in the Manko and Okukubi protected estuarine ecosystems on Okinawa Island, Japan from February to October 2006. Butyltin compounds (BTCs) were frequently detected in all seasons, while phenyltin (PhTs) were found in winter and early spring. In Manko estuary, the total mean concentrations of BTCs and PhTs were 22.78 +/- 30.85, (mean +/- SD, n = 53) and 0.08 +/- 0.27 ng(Sn) L-1, respectively. In Okukubi estuary, BTCs and PhTs were 12.58 +/- 23.96 and 0.47 +/- 1.67 (n = 55) ng( Sn) L-1, respectively. The Manko sediments can be classified as lightly contaminated, while the Okukubi sediments were uncontaminated with tributyltin (TBT). The mean levels of TBT shown in Manko estuary exceeded the threshold level and represent an ecotoxicological risk to sensitive aquatic life. Generally, the present study reports the occurrence and continuous input of OTCs in the protected estuaries, even 16 years after legal restriction of TBT usage in coastal waters was implemented by the Japanese Environmental Authorities.
Six organotin species tributyltin (TBT), dibutyltin (DBT), monobutyltin (MBT), triphenyltin (TPT). diphenyltin (DPT) and monophenyltin (MPT) were investigated along the coast of Okinawa Island, Japan. Analytical conditions for organotin compounds in seawater and in marine sediments were optimized for GC with pulsed flame photometric detector. In July 2002, samples were collected at 30 locations. Butyltin species were present in all stations, but phenyltin species can be detected in only a few stations. The TBT concentration ranged from 40.2 ng L"1 Sn to ND (not detected) in the seawater, and from 172 to 1.20 ng g"1 Sn (dry weight) in sediments, with the highest values closely related with shipping activity and decreasing according to the distance from potential sources. A comparative study of the concentration of organotin species in 2002 and 2003 showed an
