Japan Geoscience Union Meeting 2015

Presentation information

Oral

Symbol A (Atmospheric and Hydrospheric Sciences) » A-HW Hydrology & Water Environment

[A-HW27] Water and material transport and cycle in watersheds: from headwater to coastal area

Sun. May 24, 2015 4:15 PM - 6:00 PM 301B (3F)

Convener:*Shinji Nakaya(Department of Civil Engineering, Faculty of Engineering, Shinshu University), Mitsuyo Saito(Graduate School of Environmental and Life Science, Okayama University), Shin-ichi Onodera(Graduate School of Integrated and Arts Sciences, Hiroshima University), Kazuhisa Chikita(Department of Natural History Sciences, Faculty of Science, Hokkaido University), Tomohisa Irino(Faculty of Environmental Earth Science, Hokkaido University), Masahiro Kobayashi(Forestry and Forest Products Research Institute), Seiko Yoshikawa(Narional Institute for Agro-Environmental Sciences), Noboru Okuda(Research Institute for Humanity and Nature), Chair:Kazuhisa Chikita(Department of Natural History Sciences, Faculty of Science, Hokkaido University), Masahiro Kobayashi(Forestry and Forest Products Research Institute)

5:33 PM - 5:36 PM

[AHW27-P02] Modeling transportation of noxious trace elements in rivers by means of colloidal iron interaction

3-min talk in an oral session

*Chi HAI1, Shinji NAKAYA1, Mistunori ISHIKAWA1, Tomoko KUJIOKA1, Harue MASUDA2 (1.Shinshu University, 2.Osaka City University)

Keywords:noxious trace elements, river, colloid, Yatuga-take, Asama-yama

Toxic elements in water systems can expose crops to dangerous levels of contamination through irrigation and soil pollution. Therefore, it is of vital importance to ascertain the dynamic state of noxious trace element as they are carried by soil colloids via river systems. However, the behavior of toxic elements varies depending on their current state. Possible states consist of the colloidal state, in which the element is attracted to some colloids by sorption, or water-soluble state where the element exists as an ion or a complex ion.
The study focuses on two rivers with headwaters in volcanic rock areas near Mt. Asama and Mt. Yatsugatake in Saku, Nagano. The concentrations of both major elements and trace elements are measured before and after filtration. By comparing the concentrations before and after filtration, the current state (water-soluble or colloid) of the toxic elements (Arsenic, Cadmium, Cesium and Lead) in river may be determined. From correlations between the various elements, the parameter that explains the effect of the concentration and transportation of toxic trace elements can be elucidated.
As a result, 1) The current state of toxic trace elements in Mt. Asama area is: Arsenic (water-soluble state), Cadmium (colloidal state), Cesium (water-soluble state), and Lead (colloidal state). The state of toxic trace elements in Mt. Yatsugatake area is: Arsenic (water-soluble state), Cadmium (colloidal state), Cesium (colloidal state), and Lead (colloidal state). 2) When the current state of trace elements is colloidal state, the parameter which explains the effect of the concentration and transportation of toxic trace elements is sorption by Fe-Al-Ti colloid. When the current state of trace elements is water-soluble state, the parameter is pH. 3) The model of transportation of noxious trace elements by means of colloidal iron interaction is formed. The model has two types. Type 1: In Y-river in Mt. Yatsugatake area which does not contain much iron, toxic trace elements are attracted to Fe-colloid by sorption. Type 2: In A-river in Mt. Asama area which largely contains colloidal iron, toxic trace elements are also attracted to Fe-colloid by sorption. However, there are some colloidal irons without toxic trace elements.