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[AOS22-P04] Distribution of iodine and methane dissolved in interstitial water of surface sediment in Tokyo Bay
Keywords:Tokyo Bay, Sapropel, Interstitial water, TOC, Iodine, Methane
Since iodine has a strong biophilic nature, it is taken up by phytoplankton and other organic matter in seawater (Price and Calvert, 1977; Elderfield and Truesdale, 1980). Phytoplankton debris is deposited on the seafloor with other sediment particles. The organic matter is decomposed by geothermal and biogenic effects during the burial process and produces methane. The iodine adsorbed on the organic matter is released into the interstitial water (Wallmann et al., 2006).
In Tokyo Bay, large amounts of domestic and industrial wastewater flow into the bay through several rivers. The nutrients in the wastewater cause eutrophication of the seawater and the proliferation of phytoplankton. The phytoplankton debris is deposited as organic matter on the seafloor, and Tokyo Bay is characterized as an environment with an excessive supply of organic matter derived from living organisms. The objective of this research is to understand the distribution of iodine and methane concentration in interstitial water in Tokyo Bay. Hiyodori, the Tokyo University of Marine Science and Technology (TUMSAT) training ship, collected surface sediment samples from 58 sites in northern Tokyo Bay using an Ekman barge bottom sampler.
The total organic carbon in the surface sediment was about 0.1-3% in the coastal area and 3-5% in the central part of the bay, and the iodine concentration in the interstitial water was about 0.2-3 µM in the coastal area and 3-5 µM in the central part of the bay. The concentrations of total organic carbon and iodine increase from the coast to the center of the bay, indicating that the higher the amount of organic matter in the sediment, the higher the concentration of iodine in the interstitial water. On the other hand, the distribution of methane concentration in interstitial water was different from that of total organic carbon and iodine. The methane concentration in the eastern part of the bay was low, ranging from 0 to 6 µM. In the northwestern coastal area (off Urayasu to off Koto-Ku), methane concentrations were high (>20 µM), especially at the sampling sites near rivers and landfills. The concentrations of iodine and methane in interstitial water at all sampling sites ranged from 0 to 5 µM and 0.5 to 103 µM, respectively. The maximum concentrations of iodine and methane were about 10 and 1000 times higher than those in seawater, respectively, in the very surface layer of the seafloor in contact with seawater.
In Tokyo Bay, large amounts of domestic and industrial wastewater flow into the bay through several rivers. The nutrients in the wastewater cause eutrophication of the seawater and the proliferation of phytoplankton. The phytoplankton debris is deposited as organic matter on the seafloor, and Tokyo Bay is characterized as an environment with an excessive supply of organic matter derived from living organisms. The objective of this research is to understand the distribution of iodine and methane concentration in interstitial water in Tokyo Bay. Hiyodori, the Tokyo University of Marine Science and Technology (TUMSAT) training ship, collected surface sediment samples from 58 sites in northern Tokyo Bay using an Ekman barge bottom sampler.
The total organic carbon in the surface sediment was about 0.1-3% in the coastal area and 3-5% in the central part of the bay, and the iodine concentration in the interstitial water was about 0.2-3 µM in the coastal area and 3-5 µM in the central part of the bay. The concentrations of total organic carbon and iodine increase from the coast to the center of the bay, indicating that the higher the amount of organic matter in the sediment, the higher the concentration of iodine in the interstitial water. On the other hand, the distribution of methane concentration in interstitial water was different from that of total organic carbon and iodine. The methane concentration in the eastern part of the bay was low, ranging from 0 to 6 µM. In the northwestern coastal area (off Urayasu to off Koto-Ku), methane concentrations were high (>20 µM), especially at the sampling sites near rivers and landfills. The concentrations of iodine and methane in interstitial water at all sampling sites ranged from 0 to 5 µM and 0.5 to 103 µM, respectively. The maximum concentrations of iodine and methane were about 10 and 1000 times higher than those in seawater, respectively, in the very surface layer of the seafloor in contact with seawater.