Level and source of 129I of environmental samples in Xi'an region, China

Iodine-129 is widely used as a tracer in various environmental practices such as monitoring of nuclear environmental safety, seawater exchange and transport, geochemical cycle of stable iodine and dating of geological events. The spatial distribution of I-129 concentration varies significantly on global scale because of anthropogenic input from nuclear activities coupled with scarcity of data on environmental I-129 variability in many parts of the world including Asia. Here we report new data on I-129 and I-127 concentrations in soil, vegetation, river water and precipitation collected from Xi'an area, China. The results indicate values for environmental I-129/I-127 ratios in the investigated area range from 1.1 x 10(-10) to 43.5 x 10(-10) with a mean of 20.6 x 10(-10), which is 1-3 orders of magnitude lower than the ratios observed in Europe, but comparable with those observed in the locations far from direct effect of point release sources and at similar latitude. The main source of I-129 in the investigated area is attributed to the global fallout of both atmospheric nuclear weapons testing and long distance dispersion of fuel reprocessing releases. (C) 2011 Elsevier B.V. All rights reserved.