Sources of highly regional ¹²⁹I in soils in northeast China

The transport and deposition pathways of anthropogenic radionuclides at the global scale, particularly volatile ¹²⁹I, remain somewhat elusive due to a dearth of comprehensive investigations. To gain a better understanding of the transport dynamics and deposition mechanism of anthropogenic ¹²⁹I in the terrestrial environment, one hundred surface soil samples collected from northeast China were analyzed for ¹²⁹I and ¹²⁷I concentrations in this study. Our findings reveal that ¹²⁹I/¹²⁷I atomic ratios in the mid-eastern Inner Mongolia (MIM) were approximately an order of magnitude higher than the rest of the investigated area. This is, besides the global fallout and the long-range transport of ¹²⁹I released from the European nuclear reprocessing plants via westerly winds, possibly attributed to the dust with high ¹²⁹I levels from the East Asian arid regions. In addition to the significant dust-induced ¹²⁹I input, the unique meteorological conditions and topographical features in the MIM synergistically contribute to the pronounced accumulation and deposition of ¹²⁹I in this region. This study will provide novel insights into the transport and deposition mechanism of anthropogenic radionuclides, which is significant for the assessment of anthropogenic nuclear activities on the environment in the future.