Deposition Velocity of Gaseous Organic Iodine from the Atmosphere to Rice Plants

Abstract

To obtain parameter values for the assessment of 129I transfer from the atmosphere to rice, deposition of CH3I to rice plants has been studied. The mass normalized deposition velocity (VD) of CH3I for rough (unhulled) rice was 0.00048 cm3 g-1 s-1, which is about 1/300 of that of I2. Translocation of iodine, deposited as CH3I on leaves and stems, to rice grain was negligibly small. Distribution of iodine between hull and inner part of the grain was found to depend also on the chemical forms of atmospheric iodine to be deposited. The ratio of the iodine distribution in a grain exposed to CH3I was as follows: rough rice:brown rice (hulled rice):polished rice = 1.0:0.49:0.38. The distribution ratio in polished grains for CH3I exposed rice was about 20 times higher than that for I2.