Marine sediment is periodically dredged for development and maintenance of navigation. Because of the prohibition of ocean disposal, limited landfill space and socioeconomic reasons, beneficial reuse of dredged sediment as soil has been considered as an effective option to manage dredged marine sediment. However, dredged marine sediment is often contaminated by TPHs and heavy metals due to anthropogenic activities. Therefore, the contaminants in sediment should be treated and ecotoxicity of terrestrial stressors remaining in the remediated sediment should be assessed to ensure ecological health of the sediment prior to beneficial reuse. In this study, specifically, it was assessed how the ecotoxicity of a field dredged sediment sample changes by TPH removal. Salinity in the sediment was removed prior to TPH treatment since salinity exhibited the most critical toxicity to terrestrial receptors among potential stressors including salinity, TPH and heavy metals in our previous study. In order to remove TPHs in the sediment, solvent extraction (20 min, 150 rpm, 1:6 solid-liquid ratio) and thermal treatment (300 celsius degree, 30 min) were applied. After the treatment, residual TPH content, heavy metal speciation and soil properties (CEC, TOC, TN, TP) of the treated sediment were analyzed. Toxicity test using Hordeum vulgare (barley) was performed to assess the ecotoxicity. Based on the toxicity test results, growth and germination rates of H. vulgare were reduced by the treatments for TPH removal due to potential residual toxicants such as byproducts formed and residual solvent. To remove the toxicants after the treatments, postremediation procedures such as volatilization and water rinsing were carried out. By the postremediation procedures, the germination and growth rates of H. vulgare were significantly enhanced. The results indicated that processes for the removal of residual toxicants in sediment may be necessary to improve the ecotoxicity of remediated sediment.

Assessment of changes in ecotoxicity of dredged marine sediment by sediment treatments for TPH removal

253rd National Meeting (2017)

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