Assessment of TBT and Antifouling Alternative Contamination in Korean coast after the total TBT ban

Abstract

ABSTRACT

Assessment of TBT and Antifouling Alternative Contamination in Korean coast after the total TBT ban

In 2003, South Korea imposed a total ban on the use of tributyltin (TBT)-based paint for all new ships, including oceangoing vessels, built in the country. In this study, the effectiveness of the total ban on TBT use and the subsequent contamination of coastal environments in Korea with alternative biocides were investigated. The mean TBT levels in seawater samples from 17 sites in Jinhae Bay decreased from 11.3 ng Sn/L (before the TBT ban, 1995/97) to 2.5 ng Sn/L (immediately after the TBT ban, 2003/04), and then 0.2 ng Sn/L in 2009 (6 years after the TBT ban). The residual TBT levels in oyster tissues from samples collected from 13 sites were about four times lower in 2012/13 (mean, 130 ng Sn/g) than in 1995/97 (mean, 500 ng Sn/g). The total ban on TBT use effectively reduced seawater and oyster TBT levels in Jinhae Bay, but TBT levels in seawater and oysters remain above the global environmental quality standards established to protect marine organisms. The sediment TBT levels have not significantly decreased, even 10 years after the partial TBT ban on small ships and 5 years after the total TBT ban on all oceangoing vessels in Korea. Rock shell (Thais clavigera) samples were collected at 10 sites along the coast of Jinhae Bay. The frequency and degree of imposex, sex ratio, and residual TBT levels in the rock shell were compared before, and 5 and 10 years after, the TBT ban. The percentage of females increased from 26% in 1995/97 to 62% in 2013, 10 years after the TBT ban. The mean penis lengths of the imposex (imposition of male organs on females) females decreased from 9.0 mm (before the TBT ban) to 2.9 mm (10 years after the TBT ban). The mean frequency of imposex females decreased from 100% (in 1997/95) to 92% in 2008, and then to 51% in 2013. No imposex females were found at 2 of 10 sampling sites in 2013. The mean TBT concentrations in rock shells were 29 (range, 6–58) ng Sn/g in 2008 and 43 (range, 14–106) ng•Sn/g in 2013. These values were significantly lower than that the 117 (range, 23–269) ng•Sn/g in 1995/97. The mean TBT concentration in rock shells decreased approximately fourfold over the 11 years. Seawater samples from the three major bays, fishing ports and harbors in Korea, were analyzed to determine the levels of TBT and alternative biocides used as alternative antifouling agents. Of the alternative biocides, Diuron and Irgarol 1051 were detected at all of the sampling sites. In contrast, the levels of Pyrithiones, Sea-Nine 211, and Dichlofluanid were below the detection limits in all samples. Diuron levels were higher compared to Irgarol 1051. The Diuron and Irgarol 1051 concentrations in the study area ranged between 29 ng/L and 1360 ng/L and between nd (not detected) and 14.1 ng/L, respectively, indicating that Diuron and Irgarol 1051 have been widely used in Korea. The frequency of detection of Diuron, as well as Irgarol 1051 and M1 (a breakdown product of Irgarol 1051) in Gohyun Bay was high in comparison to the other areas studied. The concentrations of TBT and BTs [MBT + DBT + TBT] in the study area were in the range of nd to 23.9 ng Sn/L and nd to 69.9 ng Sn/L, respectively. The concentration of TBT was high in fishing ports (mean, 4.1 ng Sn/L) and harbor areas (mean, 3.0 ng Sn/L), while it was relatively low in the three major bays (mean, 0.6 ng Sn/L) and open water of Jinhae Bay (mean, 0.1 ng Sn/L). The significant correlation between TBT and Diuron concentrations in the major harbors indicates that the source of Diuron was AF agents used on ships’ hulls. Diuron levels exceeded the UK environmental quality standard (EQS) value in 73% of the fishing port samples, 64% of the samples from the major bays, and 42% of the harbor samples. Irgarol 1051 levels were marginally below the Dutch and UK EQS values at all sites. Sediment samples from shipping (i.e., ports and harbors sites) and shipbuilding (i.e., shipyards) areas were analyzed to determine the levels of booster biocides and butyltins. Diuron was detected at all sampling sites and Irgarol 1051 was identified at 15 of 34 stations, while Pyrithiones and Dichlofluanid were below the detection limits in all samples. The concentration of Diuron in shipbuilding and shipping areas was in the range of 2.3–16.9 ng/g and 6.1–62.3 ng/g, respectively. The Irgarol 1051 concentration was in the range from nd to 7.4 ng/g and was higher in Gohyun Bay than the other areas surveyed. Of the shipping areas studied here, the highest concentration of Diuron was observed at Busan Harbor (62.3 ng/g). The TBT concentrations varied from 3 to 55,264 ng•Sn/g in sediment samples. The highest TBT (55,264 ng Sn/g) and butyltin (70,223 ng Sn/g) concentrations were found in the vicinity of a large repairing shipyard in Ulsan. The Diuron levels in the shipbuilding area were significantly correlated with the levels of TBT and Irgarol 1051. The Diuron concentration in sediment from shipping areas (50%) and the shipbuilding sites (25%) in this study exceeded the proposed maximum permissible concentration (MPC) of 9 ng/g value. The concentration of Irgarol 1051 exceeded the environmental risk limit (ERL) of 1.4 ng/g value in 40% of the shipbuilding sites and 20% of the shipping areas.