资源环境科技发展态势分析平台

We present data of I-129 deposition in fresh snow in the Laohugou glacier basin, northeast Tibetan Plateau, in summer 2016 and 2017, and trace its source and elevational distribution in the troposphere. Our results show that the I-129/I-127 atomic ratios in the fresh snow on the glacier surface are about 2 orders of magnitude larger than those in the Antarctic fresh snow and 4 orders the prenuclear level, indicating a predominantly anthropogenic source of the I-129 in the mountain glacier environment of northeast Tibetan Plateau. The I-129 level in the Laohugou glacier basin is 1-2 orders of magnitude lower than at representative European locations, and not significantly higher than that observed at other sites in Asia. The I-129/I-127 atomic ratio and I-129 level show clear increases with elevation from 4,300 to 5,100m above sea level. The I-129 in the Laohugou glacier basin is probably deposited from the upper troposphere where there exists a local maximum of I-129. A conceptual model for interpretation of the observed I-129 concentration and profile in Laohugou is provided. Thus, this work is of importance in providing a more complete view on the transport, dispersion, and removal of I-129 in the atmosphere.

Plain Language Summary We measured the concentration measurements of I-129, together with I-129/I-127 atomic ratios, deposited in the fresh snow at various altitudes, in the Laohugou glacier basin, western Qilian Mountains, northeast Tibetan Plateau. This unique dataset provides the first evidence how I-129 deposition varies with height in the middle troposphere, and a glimpse on the dispersion and pathway of anthropogenic radioiodine pollutants to the remote Tibetan Plateau glaciers. The dataset is thus an important addition to the global I-129 database. The observations at Laohugou show that I-129 increases, in contrast to I-127 and heavy metals Pb and Ni which decrease, with height in the middle troposphere. This suggests that the source of the deposited I-129 is located in the upper troposphere. A hypothetic interpretation of the observed I-129 profile is provided.