Remedial effect and operating status of a decommissioned uranium mill tailings (UMT) repository: A micro-ecological perspective based on bacterial community.

From a radioecological perspective, increasing attention has been paid to the long-term stabilisation of decommissioned uranium mill tailings (UMT) repositories. However, little is known about the evaluation of decommissioning and remedial effects of UMT repositories from a microecological perspective based on bacterial communities. Here, we analysed the distribution and structure of soil community assemblies along different vertical soil profiles in a decommissioned UMT repository and explored the impact of soil properties, including physicochemical parameters, metal(loid)s, and radionuclides, on the bacterial assemblage. We found that the α diversity of the bacterial community was unaffected by variations in different soil profiles and taxa were classified at the phylum level with small significant differences. In contrast, the bacterial community structure in and around the UMT repository showed significant differences; however, this difference was significantly affected by soil metal(loid)s and physicochemical properties rather than soil radionuclides. In addition, seven bacterial genera with significant differences between the inner and surrounding regions of the repository could be used as potential indicators to further investigate the remedial effects on soil environmental quality. These findings provide novel insights into the construction of an assessment system and in situ biomonitoring of UMT repositories from a microecological perspective based on bacterial communities.

Response of soil microbial communities to natural radionuclides along specific-activity gradients.

Understanding the response of soil microbial community to abnormal natural radionuclides is important to maintain soil ecological function, but the underlying mechanism of tolerance and survival of microbes is poorly studied. The effects of natural radionuclides on the topsoil microbial communities in anomalous natural radiation area were investigated in this work, and it was found that microbial community composition was significantly influenced by the specific-activities of natural radionuclides. The results revealed that relative abundances of 10 major microbial phyla and genera displayed different patterns along specific-activity gradients, including decreasing, increasing, hump-shaped, U-shaped, and similar sinusoidal or cosine wave trends, which indicated that the natural radionuclides were the predominant driver for change of microbial community structure. At the phylum and genus level, microbial communities were divided into two special groups according to the tolerance to natural radionuclides, such as 238U and 232Th, including tolerant and sensitive groups. Taken together, our findings suggest that the high specific-activities of natural radionuclides can obviously drive changes in microbial communities, providing a possibility for future studies on the microbial tolerance genes and bioremediation strains.

Assessment of radiation dose hazards caused by radon and its progenies in tap water by the human dosimetric model.

Radon is readily soluble in water, and radon exposure caused by household water consumption may pose a threat to public health. In this study, the radon concentration in the tap water of residential buildings was measured, and the average value was 543.33 mBq L-1, which was in line with the radon concentration limit recommended by USEPA (11.11 Bq L-1) and EURATOM (100 Bq L-1), and also within the range of the results of radon concentration measurements in tap water in other countries or regions. Through water bath heating at different temperatures, the radon retention curves of multiple groups of samples at different temperatures were fitted and analyzed. The results showed that the radon retention continued to decrease between 25 and 70 °C, remained stable between 70 and 85 °C, and then continued to decline slowly. Combined with the measurement results, the effective doses of α- and ß-particles emitted by 222Rn and its progenies to residents respiratory and alimentary tissues and organs were calculated using the computational model provided by ICRP under two typical water scenarios of shower and drinking water, and the results show that radon exposure caused by normal water consumption will not pose a serious threat to public health.