Department of Radiation Physics and Chemistry, Fukushima Medical University, 1 Hikarigaoka, Fukushima, 960-1295, Japan.
The Executive Office of the Nuclear Energy Commission, Uildverchid Street 2, Khan Uul District, Ulaanbaatar, Mongolia.
Environ Sci Pollut Res Int. 2019 Nov;26(32):33494-33506. doi: 10.1007/s11356-019-06420-3. Epub 2019 Sep 16.
Unegt subbasin in Dornogobi Province, southeastern Mongolia, contains the Dulaan Uul uranium deposit, for which development for commercial mining has been conducted as of 2015. Zuunbayan is a commune located close to the Dulaan Uul uranium deposit, and residents of Zuunbayan and their livestock can easily approach the uranium deposit area, including an aboveground dump site, which was created as a result of the mining development. The present study measured and analyzed the gamma dose rate (absorbed dose rate in air) distribution in Unegt subbasin using data collected from a car-borne measurement survey. The gamma dose rate increased from the northern (45-65 nGy/h) to the central (50-69 nGy/h, including Zuunbayan) and the southern (54-195 nGy/h, including Dulaan Uul) parts of the study area. The gamma dose rates (up to 195 nGy/h) around the dump site in Dulaan Uul were significantly higher than the background level (< 80 nGy/h) at several points. Additional in-situ measurements showed that the gamma dose rates reached up to 450 nGy/h at these locations, which was primarily attributed to the gamma radiation emitted by U series elements. Spatial distribution of gamma dose rates around the dump site revealed that the gamma radiation did not originate from the dump, but from the ground, at the measurement points. Analysis of collected soil samples showed that U and Ra were concentrated in deeper soil. These results indicate that the gamma dose rates higher than the background level were not associated with the aboveground mine dump; rather, they were very probably caused by presence of uranium deposits close to the ground surface.
蒙古东南部东戈壁省的 Unegt 流域拥有 Dulaan Uul 铀矿床，自 2015 年以来，该矿床一直处于商业开采开发之中。Zuunbayan 是一个靠近 Dulaan Uul 铀矿床的社区，Zuunbayan 的居民及其牲畜可以轻松进入铀矿床区域，包括一个因采矿开发而形成的露天尾矿库。本研究使用车载测量调查收集的数据，测量和分析了 Unegt 流域的伽马剂量率（空气中的吸收剂量率）分布。伽马剂量率从北部（45-65nGy/h）增加到中部（50-69nGy/h，包括 Zuunbayan）和南部（54-195nGy/h，包括 Dulaan Uul）。Dulaan Uul 尾矿库周围的伽马剂量率（高达 195nGy/h）在几个点明显高于背景水平（<80nGy/h）。额外的现场测量表明，这些地点的伽马剂量率高达 450nGy/h，主要归因于 U 系元素发出的伽马辐射。尾矿库周围伽马剂量率的空间分布表明，伽马辐射不是来自测量点的尾矿库，而是来自地面。对采集的土壤样本的分析表明，U 和 Ra 集中在较深的土壤中。这些结果表明，高于背景水平的伽马剂量率与地上矿山尾矿库无关；相反，它们很可能是由于靠近地面的铀矿床的存在而引起的。
