폐기물 배출해역의 환경성 평가에 의한 준설토 피복효과에 관한 연구

Abstract

In this study, the capping effects of the dredged materials applied for remediation and restoration of heavily contaminated areas in the West Sea-Byeong ocean dumping site were evaluated through analyses of sediment physicochemical properties, the assemblages and health of benthic fauna, and sediment ecotoxicity. Management plans for future development were sought to improve the capping effect. First, results of the analysis of sediment physicochemical properties showed significant differences in particle size between areas due to the capping effect of dredged materials. In the capping area, the content of organic matter (COD; about 48%) and heavy metals (about 50%) was lower than such content in the no capping area due to blockage of the contaminated sediment layer, demonstrating the capping effect of dredged materials. In the case of benthic assemblages, differences in particle size, COD, and the number of sensitive species were observed in the capping area. Regarding the evaluation of the health of benthic fauna for each research area, while the score on AZTI’s Marine Biotic Index (AMBI) was 3.2 (good) or less in all areas, the Benthic Pollution Index (BPI) value of 1 has been maintained in the capping area since 2017, indicating better benthic health than in the no capping area (BPI 1–2) and suggesting that the recovery of the benthic ecosystem is underway. As a result of the ecotoxicological test using luminescent bacteria (Vibrio fischeri) and benthic amphipods (Monocorophium acherusicum), in all areas, the relative luminescence inhibition rate and the relative average survival rate were each less than 30%, indicating “no toxicity” according to the criteria presented in the Korean Standard Method of Examination for Marine Environment. The integrated evaluation of the capping effects of dredged materials was determined from scores for the COD, heavy metal concentration index (Geoaccumulation Index: Igeo), BPI, and results of the ecotoxicological test. As a result, the no capping area scored 4–5 (very poor), whereas the reference area was evaluated with a score of 3 (normal). Meanwhile, the score for the capping area was 2 (good) to 3 (normal), indicating that dredged materials were effective in remediating and restoring contaminated sediment. Therefore, it is desirable to apply the capping method in order to establish a physical barrier with dredged materials as a method for remediation and restoration of heavily contaminated sediment in ocean dumping site. By applying such capping materials as zeolite and oyster shells, in addition to dredged materials, a chemical remediation effect can be expected through adsorption and decomposition of highly concentrated heavy metals and organic substances isolated under the capped layer. In addition, when expanding the project to remediate and restore at the ocean dumping site in the future, it will be necessary to establish and operate an integrated ocean dumping site management system by adopting the concept of adaptive management including the steps of assessing problems, establishing and designing the management plan, implementing the plan, monitoring, conducting evaluations, and adjustments.