Implementation of a Numerical Model of Metals for Total Maximum Daily Loads (TMDLs) in Onsan Harbor, Korea

Abstract

Kim, Y.H.; Sugarman, D.E.; Kim, H.C.; Son, S.; Ha, H.K.; Chang, W.K.; Han, K.W., and Ryu, J., 2018. Implementation of a Numerical Model of Metals for Total Maximum Daily Loads (TMDLs) in Onsan Harbor, Korea. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 1506–1510. Coconut Creek (Florida), ISSN 0749-0208.Accumulation of heavy metals has been one of fundamental environmental concerns for many coastal and estuarine systems, which can be directly influenced by contaminants loading from land. Onsan Harbor, Korea, surrounded by Onsan National Industrial Complex, shows high concentration of heavy metals in the seabed sediments. In order to establish proper environmental management plan for Onsan Harbor, the implementation of a Total Maximum Daily Loads (TMDL) was proposed. As a part of TMDL for metals, numerical model has been developed to evaluate metal fluxes into the Onsan harbor.A bathtub model for four different metals, including Copper, Zinc, Lead, and Mercury, was implemented in Onsan harbor. To supply data for boundary conditions and model calibration, extensive monitoring programs were conducted in the study area for past three years, between 2014 and 2016. The data from the monitoring programs includes freshwater discharge rate, load of metals from streams and tributaries, concentration of dissolved and particulate metals in water and sediments, sedimentation rates, and current velocities. The model was calibrated and validated with these monitoring data and other public data sets, and the results confirm high performance of the metal TMDL model in Onsan Harbor system. To evaluate numeric targets of the TMDL for metals, more than 100 scenarios were simulated with the well-calibrated model. The results show that (1) after the reduction of 10% loading from the present level, the copper concentration in sediments will be lower than Probable Effects Level (PEL) within 12 years, and (2) after the reduction of 10% zinc loading, the zinc concentration in sediments will be lower than PEL in 17 years.