Antifouling paint additives in surface sediments were investigated in Okpo Harbor and Onsan Harbor, South Korea, two harbors characterized by contrasting dominant anthropogenic activities. Okpo Harbor is a shipbuilding-oriented harbor with a large shipyard, whereas Onsan Harbor represents a multi-use industrial harbor. Organotin compounds were detected at substantial levels in both harbors; however, their spatial distributions and compositional characteristics differed markedly. Okpo Harbor exhibited relatively low mean concentrations, with distinct inner-harbor hotspots dominated by tributyltin, suggesting relatively fresh TBT inputs or remobilization of TBT-containing legacy residues associated with shipyard activities. In contrast, Onsan Harbor showed higher mean concentrations and broader spatial variability, with monobutyltin predominating, reflecting aged residues derived from advanced degradation of historical TBT inputs. Booster biocides were enriched in inner-harbor areas of Okpo Harbor, likely associated with hull coating and repair activities, whereas concentrations in Onsan Harbor were generally lower and spatially restricted. Potentially toxic elements were elevated in zones influenced by ship repair in Okpo Harbor and by adjacent industrial complexes in Onsan Harbor, consistent with surrounding land-use characteristics. Ecological risks were generally low, with TBT-driven risks localized in inner Okpo Harbor and medium-high mERM-Q values, driven by Zn and Pb, at two industrial sites in Onsan Harbor. These findings highlight the importance of harbor-specific management strategies that consider dominant anthropogenic activities and local environmental conditions.
This study examined hook-size effects on catch characteristics, maturity composition, selectivity, and management performance in red tilefish (Branchiostegus japonicus) longline fisheries off Jeju Island, Korea. Four surveys tested Hook Nos. 11, 13, 14, 15, and 17. Selectivity was estimated using the Share Each Length's Catch Total (SELECT) framework. A scenario-based policy-utility analysis integrated biomass catch per unit effort (CPUE), immature fish proportion, and bycatch ratio. Hook No. 17 was excluded from the main analyses because it caught only one red tilefish. Mean total length differed among Hook Nos. 11, 13, 14, and 15 (one-way analysis of variance, F(3, 208) = 7.545, p < 0.001). In binary logistic regression, Hook No. 14 had higher odds of capturing reproductively mature fish than Hook No. 11 (odds ratio [OR] = 3.97, 95% confidence interval [CI]: 1.44-10.90, p = 0.0075), whereas Hook No. 15 did not differ significantly (OR = 2.82, 95% CI: 0.80-9.91, p = 0.106). The logistic SELECT model with hook-specific relative fishing power had the lowest Akaike's information criterion. Estimated lengths at 50% selectivity (L-50) ranged from 19.45 to 26.53 cm for Hook Nos. 11-15. Hook No. 11 had the highest productivity-oriented utility, whereas Hook No. 14 had the highest balanced and conservation-oriented point estimates. Survey-level bootstrap selection probabilities for Hook No. 14 were 60.0 and 63.3% under the latter scenarios, respectively. Hook No. 14 showed the most favorable conservation-productivity trade-off; however, broader validation is required before considering minimum hook-size regulation.
Early detection and localization of sodium leakage are important for ensuring the safety of sodium-cooled fast reactor (SFR) piping systems. Double-walled piping can mitigate the consequences of external sodium leakage; however, conventional wire-type leak detectors provide limited spatial information and may be affected by incomplete contact between the leaked fluid and sensing electrodes. This study experimentally develops and validates a quantitative leakage detection and localization methodology based on Raman-scattering distributed temperature sensing (DTS) for double-walled piping. A water-mockup test facility, WALSUM, was constructed to simulate leakage in the annular space of a double-walled pipe, and the detection performance was evaluated over leak flow rates of 0.1–7.0 mL/min and fluid temperatures of 35–90 °C. To improve the robustness of leakage identification against measurement noise and thermal transients, a three-point spatial temperature-ratio method was combined with a statistical detection criterion based on the standard deviation of the ratio difference. A critical threshold of 0.03 was established from a three-standard-deviation margin of the non-leakage baseline. The experimental results demonstrated that the DTS system detected the minimum tested leak rate of 0.1 mL/min, with response times ranging from 195 to 2,579 s depending on the leak flow rate and fluid temperature. The response became faster and the leakage-induced thermal signal increased with increasing leak flow rate and fluid temperature. During a 33 h non-leakage transient test involving repeated heating and cooling cycles, no false alarms were observed. In comparative tests, the DTS system successfully detected a leakage event under conditions where the wire-type detector was affected by incomplete electrode contact. In addition, the distributed sensing capability enabled leak localization with a theoretical positional uncertainty of ±0.25 m based on the 0.5 m spatial resolution of the DTS. These results demonstrate the feasibility of Raman-DTS for quantitative, distributed leakage monitoring and localization in double-walled SFR piping and provide experimentally based performance metrics for further development toward practical reactor applications.
