Spatio-temporal Changes of Sediment Environment in the Taehwa River Estuary, Ulsan of Korea

The Taehwa River is a successful case for restoration of ecological system in Korea through the restoration project conducted during 1995-2005. To sustain this restored ecosystem, seasonal surveys for surface sediment quality were conducted in the entire area of the river estuary during the year 2012. It is noteworthy that the areas with pollutant source inflow exhibited higher organic carbon and acid volatile sulphide concentrations than the pollutant standard indices (20 mg C.g(-1) and 0.2 mg S.g(-1)) in the spring and summer. Trace metal concentrations (As: 13.2; Cu: 64.2; Zn: 185.7; and Pb: 48.3; mg.kg(-1)) also showed a considerable increment from their respective Effect Range Low standards. The observed sediment oxygen demand (avg. 41.13 mmol O(2)m(-2).d(-1)) in the prime habitat of Ruditapes philippinarum was substantially higher in this study than the average value (16 +/- 6 mmol O(2)m(-2).d(-1)) in Southern coastal area of Korea. The results from materials flux study suggest that high phosphate release from sediment into water column in summer and low sedimentation rate of nitrogenous nutrients during fall season could influence prolonging algal blooms in the Taehwa estuary. A further study is needed for a long-term of sediment monitoring on environment quality changes to maintain the restored ecological system and a safe consume of seafood.