Factors controlling excess radium in the Nakdong River estuary,Korea: submarine groundwater discharge versus desorption from riverine particles |
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| Institution: | 1. Department of Oceanography, Pukyong National University, Pusan 608-737, South Korea;2. College of Natural Sciences, School of Earth and Environmental Sciences, Seoul National University, Building #18-202, Seoul 151-742, South Korea;1. Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, Jiangsu Collaborative Innovation Center for Atmospheric Environment & Equipment Technology, School of Environmental Science and Engineering, Nanjing University of Information Science & Technology, Nanjing 210044, Jiangsu, P. R. China;2. Institute of Chemical Materials, Chinese Academy of Engineering Physics, Mianyang 621999, Sichuan, P. R. China;1. Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russian Federation;2. Department of Chemical Science and Technology, Hosei University, 184-8584 Kajino, Koganei, Tokyo, Japan;3. Department of Chemistry, Graduate School of Science, Tohoku University, 980-8578 Miyagi, Sendai, Japan;4. Department of Physics, Ben-Gurion University of the Negev, P.O. Box 653, 8410501 Be’er Sheva, Israel;1. Institute of Chemical Materials, China Academy of Engineering Physics, Mianyang 621900, People’s Republic of China;2. Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2;3. Center for Crystal Research and Development, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China;1. Institute of Solid State Chemistry, Ural Branch of the Russian Academy of Sciences, 620990 Ekaterinburg, Russian Federation;2. Ural Federal University, 620002 Ekaterinburg, Russian Federation;3. Institute for Electron Microscopy and Nanoanalysis, Graz University of Technology, A-8010 Graz, Austria;1. Key Laboratory of Resource Biology and Biotechnology in Western China (Ministry of Education), College of Life Sciences, Northwest University, Xi’an 710069, China;2. SINTEF Materials and Chemistry, PO Box 124 Blindern, Oslo N-0314, Norway |
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| Abstract: | The activities of naturally occurring radium isotopes (226Ra and 228Ra) in estuarine water were measured downstream of the dam constructed in the Nakdong River, Korea. The sampling of surface waters for radium, silicate, and suspended solid (SS) analyses was conducted at 18 stations during three periods (July 1997, April 1998, and June 1999). In general, radium activities exceeded the value expected from the mixing of two freshwater and seawater endmembers. We characterized the responses of Ra and Si according to three different conditions: (1) when the freshwater discharge and the water level of the dam relative to the sea level at low tide were lower (April 1998), the excess Ra and Si contents were lower in the estuary; (2) when the fresh water discharge was larger following heavy precipitation (July 1997), both excess Ra and Si contents were higher in the estuary with conservative mixing of Si; and (3) when the water level of the dam relative to the sea level at low tide was highest under low freshwater discharge (June 1999), high excess Ra but low Si levels were observed. The occurrence of high Ra activity in June 1999 was likely due to the large submarine brackish groundwater discharge downstream of the estuary. Since brackish groundwater in general contains high concentrations of nutrients, Ba, Ra, etc, our result suggests an important role for the submarine groundwater discharge on the biogeochemistry of estuarine/coastal waters, especially when the water level of the dam (hydraulic head) is high. |
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