[SVC47-P11] Influence of volcanic activity in river floor sediment chemical composition around Hakone volcano
Keywords:Hakone volcano, Geochemical map, Elemental composition
Experiment and Operation method: Samples were taken at 19 locations in the main stream and tributary of Hayakawa flowing around Hakone volcano. We gathered approximately 1 kg of river floor sediment with shovels and after having been dried, We put it out for a sieve and got an fine grain (0.30-0.85mm) and coarse grain (0.85-1.7mm). Next, using a magnet, a magnetic substance such as magnetite was removed from the sieved sample, and then ultrasonic cleaning was performed with pure water. This was pulverized in an agate mortar and dissolved using 0.15 mL of a 6 M HClO4 solution and 0.30 mL of a 25 M HF solution. This solution was further allowed to stand at 120 C. for 6 hours and at 170 C. for 6 hours, heated at 200 C. until dry up and allowed to cool. Finally, the sample was dissolved with 5.00 mL of 0.5 M HNO3 solution, and 0.5 M HNO3 solution was further added to the total volume of 25 mL to prepare a sample stock solution. This stock solution was suitably diluted and analyzed by ICP-MS (Thermo Science, iCAP Q).
Results and Discussion: For Hayakawa main stream samples, the concentrations of Sc and V are higher compared to the young crust upper chemical composition in the Japanese archipelago (Togashi et al., 2000), which was matched by the characteristics of volcanic ash excelled areas (mainly East Japan). High concentration of As was detected at the point where the river which flows through the submontane of Mount Hakone and Hayakawa river. It is reported that the As concentration is high in a hot spring that springs off at the central cone of Mount Hakone (Kanagawa Prefecture Onsen geology research center HP). The high concentration As of the river floor sediments discovered this time is thought to be the influence of the volcanic activity of Hakone volcano.
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