The origin of iodine in soil: I. Iodine in rainfall over Germany

Although it has been generally accepted that the major source of iodine in soils are the oceans there exists only one measurement of the iodine content in rainfall both near the coast and at a great distance inland. Concentrations of iodine in rain water and total deposition of iodine at 5 sampling sites distributed over Germany were determined by neutron activation analysis for the years 1994 and 1995. The different species of iodine in rainwater - iodine attached to particulate matter, inorganic and organic forms of iodine - were also determined. The average annual concentrations of iodine in rain ranged between (1.1 +/- 1.3) x 10(-6) and (2.8 +/- 0.8)x 10(-6) g/l in the year 1994 and between (1.8 +/- 0.6) x 10(-6) and (4.7 +/- 1.6) x 10(-6) g/l in the year 1995. The total annual deposition of iodine varied from (1.2 +/- 0.4) x 10(-3) and (2.2 +/- 0.6) x 10(-3) g/m(2) in the year 1995. In the sampling periods of the year 1994, the deposition of iodine ranged between (2.3 +/- 0.6) x 10(-4) and (7.8 +/- 2.2) x 10(4) g/m(2). The concentrations of the inorganic fractions are the highest at all sampling sites: They vary from about 40.9 to 68.6%. The smallest fraction, the particulate- bound iodine, varied from 3.8 to 6.9%. The results of our investigations show that the concentration of iodine in rain near the coast is higher than further inland. The total annual deposition of iodine, however, is not higher at the coastal sites, due to the higher average annual rainfalls at the inland areas.