Iodine, bromine and chlorine contents in solls and plants of Japan

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Abstract
As apart of the studies on the determination of the average contents of iodine, bromine and chlorine in the soils and plants of Japan, the contents of the 3 elements in the soils and plants were evaluated with emphasis placed on the difference of the land utiJization in the basin of the Nagara River, and on the difference between these values and those obtained previously for the basins of the Miomote River. The results are as follows: 1) The average content of iodine and bromine in the soils of the forest from the basin of the Nagara River was almost 10 times higber than those reported outside of Japan, but the chlorine content was similar to the average level reported (for horizon A; 39 ppm of iodine, 63 ppm of bromine and 110 ppm of chlorine). This result was very similar to the average level found in the Miomote River. 2) In the paddy soils, the chlorine content was slightly lower than that in the forest soils while the iodine and bromine content were more than 10 times lower than in the former (plow layer; 1.7 ppm of iodine, 3.3 ppm of bromine, 43 ppm of chlorine). These results were also very similar to the average of the Miomote River. These findings were ascribed to the eluviation of iodine and bromine from the soil under submerged conditions. 3) In the Brown Forest Soils, there was a positive correlation between the content of the 3 elements and carbon content, with the correlation coefficient being λ=0.96*** for chlorine λ=0.42** for iodine and λ=0.41** for bromine, respectively. And there was a negativ; correlation between the content of the chlorine and pH, the correlation coefficient being λ=-0.87**** 4) The average content of the iodine, bromine and chlorine in the leaves of the wild plants growing in the soil containing large amounts of iodine and bromine were 0.35, 6.4 and 2,100 ppm, respectively. These values were similar to the average values reported outside of Japan, and to the values reported in the basin of the Miomote River. 5) The concentration factor (content in the plant leaves/content in the soil surface [horizon A or plow layer] [in dry weight basis]) for the 3 elements in the wild plants was 0.0090, 0.10 and 19; and in the paddy rice was 0.65,6.2 and 98 for iodine, bromine and chlorine, respectively; there was a considerable difference among the elements, and the wild plants and the paddy rice. These values were similar to the values obtained in the basins of the Miomote River. In the forest soil from the basin of the Nagara River, conversion of the forest land to the paddy field may cause a marked dissolution of the iodine and bromine from the soil, thereby causing damage to the rice plants due to excess absorption of iodine and an increase in the content of bromine residues in crops that exceed the permissible limits.