Reconstruction of the Sources and Their Contributions to 129 I in Northern Xinjiang, China.

Anthropogenic 129 I, as a long-lived fission product and volatile radionuclide, can be used to investigate dispersion of air masses and the deposition of atmospheric pollution. Surface soil and soil core samples were collected from Northern Xinjiang and analyzed for 127 I and 129 I. The results show that 129 I/ 127 I atomic ratios in surface soil are inhomogeneous with a range of (2.07-106) × 10 -9 , and the maximum values in each soil core occurred at surface-subsurface layers (0-15 cm) at undisturbed sites. The dominant source of 129 I in Northern Xinjiang is European nuclear fuel reprocessing plant (NFRP) releases, accounting for at least 70% of the total inventory; less than 20% of 129 I originates from the global fallout of atmospheric nuclear weapons tests; less than 10% comes from the regional deposition of nuclear weapons tests at the Semipalatinsk site; and the regional deposition from the nuclear weapons tests at the Lop Nor site is insignificant. The European NFRP-derived 129 I was transported to Northern Xinjiang via long-distance atmospheric dispersion with the westerlies through Northern Eurasia. The distribution of 129 I in the surface soil in Northern Xinjiang is mainly controlled by topography, wind fields, land utilization, and vegetation coverage.