Behavior of iodine in a forest plot, an upland field and a paddy field in the upland area of Tsukuba, Japan : Seasonal variations in iodine concentration in precipitation and soil water and estimation of the annual iodine accumulative amount in soil horiz

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概要

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• In the course of a series of studies conducted to investigate the long-term behavior of ^<129>I (which has a half-life of 16 million years) in the environment, seasonal variation in the concentration of stable iodine (^<127>I) in precipitation and soil water to a depth of 2.5m in a forest plot, an upland field and a paddy field in the upland area of Tsukuba, Japan, were determined. Iodine concentration in precipitation tended to increase during the summer (high air temperature) season and low-rainfall period, and a positive high correlation was observed between annual rainfall and the annual amount of iodine supplied by precipitation. No seasonal variations in iodine concentration in soil water were observed at any depth in the forest plot and upland field unlike at shallow depths (0.2 and 0.5m) in the paddy field. In the paddy field, from the beginning of summer irrigation, under flooding conditions, iodine concentration in soil water at shallow depths (0.2 and 0.5 m) continuously increased, and immediately before mid-summer (intermittent) drainage and drainage, the maximum iodine concentration (approximately 50μgL^<-1>) and lowest E_h, values (approximately -150 to -200mV) were recorded. These high iodine concentration levels and low E_h values were ascribed to high air temperature (approximately>25℃ on average every 10 days) and the continuation of the groundwater level above the ground surface. As for the temporary winter irrigation period (mean daily air temperature 2-4℃), the iodine concentration was low (1.7-3.7μgL^<-1>) at all depths, as was the case in the non-irrigation period. After mid-summer drainage, and drainage, the iodine concentration in soil water at depths of 0.2 and 0.5 m decreased drastically as the groundwater level decreased. The mean annual amount of iodine accumulated in the surface soil horizons (0-0.67m) in the forest plot was estimated to be approximately 2.9mgm^<-2> (7.5μgkg^<-1> dry soil), which coincided with the mean annual amount of iodine supplied to the earth surface by precipitation. A mildly oxidative subsurface 2Bw horizon (0.60-0.89 m) in the paddy field was estimated to illuviate approximately 3.1mgm^<-2> (20μgkg^<-1> dry soil) of iodine annually by retaining iodine in the soil water percolated to this horizon.

著者

• YUITA Kouichi

  Formerly, National Institute of Agro-Environmental Sciences, Ministry of Agriculture, Forestry and F

• KIHOU Nobuharu

  National Institute for Agro-Environmental Sciences

• ICHIHASI Hideki

  National Institute for Agro-Environmental Sciences

• YABUSAKI Shiho

  Graduate School of Life and Environmental Sciences, University of Tsukuba

• FUJIWARA Hideshi

  National Institute for Agro-Environmental Sciences

• KURISHIMA Katsuaki

  Tsukuba Branch, WDB Co. Ltd.

• NODA Takeshi

  Kyonan Area Forestry and Environment Department, Yamanashi Prefectural Government

• Yuita Kouichi

  Formerly National Institute For Agro-environmental Sciences Ministry Of Agriculture Forestry And Fis

• Yabusaki Shiho

  Graduate School Of Life And Environmental Sciences University Of Tsukuba

• Ichihashi Hideki

  National Institute For Agro-environmental Sciences

• Kurishima Katsuaki

  Tsukuba Branch Wdb Co. Ltd.

• Noda Takeshi

  Kyonan Area Forestry And Environment Department Yamanashi Prefectural Government

関連論文

• Distribution of Organotin Compounds in Seawaters and Sediments in Hiroshima Bay, Japan
• Behavior of iodine in a forest plot, an upland field and a paddy field in the upland area of Tsukuba, Japan : Seasonal variations in iodine concentration in precipitation and soil water and estimation of the annual iodine accumulative amount in soil horiz
• Changes in Topographical Features and Soil Properties after Exclosure Combined with Sand-Fixing Measures in Horqin Sandy Land, Northern China (Soil Physic)
• Behavior of Iodine in a Forest Plot, an Upland Field and a Paddy Field in the Upland Area of Tsukuba, Japan. Iodine Concentration in Precipitation, Irrigation Water, Ponding Water and Soil Water to a Depth of 2.5m(Environment)
• Behavior of Iodine in a Forest Plot, an Upland Field, and a Paddy Field in the Upland Area of Tsukuba, Japan : Vertical Distribution of Iodine in Soil Horizons and Layers to a Depth of 50 m (Environment)

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