Abstract:

Soil radioactive pollution, especially from naturally occurring radioactive nuclides, has always been a key area of concern due to their long half-lives and high difficulty in management. Currently, research on soil radioactive pollution focused on nuclear facilities, uranium mining and metallurgy. There is less attention on the radioactive pollution of surrounding soil caused by the operation of naturally occurring radioactive material (NORM) enterprises. The analysis and research on the radioactive level of soil around NORM enterprises in Guangdong Province are still in an exploratory stage. In order to explore the radioactive levels in the soil around the mines of NORM enterprises in Guangdong Province, in accordance with the “Determination of radionuclides in soil by gamma spectrometry” (GB/T 11743—2013), we analyzed the activity concentrations of key nuclides, such as U-238, Ra-226 and Th-232 in the soil of 26 NORM enterprises in Guangdong Province. The results showed that the maximum activity concentrations of U-238, Ra-226, and Th-232 in the soils at the factories’ boundaries were (378±15) Bq•kg⁻¹, (207±8) Bq•kg⁻¹, and (487±19) Bq•kg⁻¹, respectively. The maximum activity concentrations of U-238, Ra-226, and Th-232 in the soil of residential areas were (337±13) Bq•kg⁻¹, (139±6) Bq•kg⁻¹, and (233±9) Bq•kg⁻¹, respectively. There was no obvious radioactive pollution in the soil outside the factories’ boundaries of the NORM; There were 8 NORM enterprises whose production activities may cause the soil radioactivity levels around the factories’ boundaries to exceed the local environmental background level, while the soil radioactivity levels at the factories’ boundaries of other NORM facilities were equivalent to the background level. This reflected that some NORM enterprises’ production may raise the surrounding soil radioactivity level. It may also be related to inadequate assessment of the background levels. Approximately two-thirds of the enterprises had higher activity concentrations of radioactive nuclides in the soil downwind from NORM boundaries than the sensitive areas and the control points areas. This may be attributed to the scattering of radioactive residues and emissions outside the boundaries during enterprise production activities. For the remaining one-third of the enterprises, there was no significant difference in radioactivity levels in the soil downwind direction of NORM enterprises’ boundaries compared to the nearby residential areas, indicating that these NORM enterprises adhered to standard daily radiation environmental management. By analyzing the soil radioactivity levels around NORM mines in Guangdong Province, daily radiation environment management requirements are proposed for enterprises involved in the development and utilization of associated radioactive minerals. These suggestions are intended to promote the healthy development of the NORM mining industry and have been submitted to the environmental authorities for consideration.

Key words: Guangdong Province, naturally occurring radioactive material (NORM), soil, γ Energy spectrum analysis, radioactive level, radiation environment management

摘要：

土壤放射性污染、特别是天然放射性核素产生的污染因其半衰期长、治理难度大一直是重点关注领域；目前对土壤放射性污染研究集中在核设施、铀矿冶等领域，伴生放射性矿运行对周围土壤的放射性污染关注较少，广东省伴生放射性矿周围土壤放射性水平分析研究尚处于探索阶段。为掌握广东省伴生放射性矿周围土壤放射性水平，按照《土壤中放射性核素的γ能谱分析方法》（GB/T 11743—2013），分析广东省26家伴生放射性矿企业厂界下风向、周围居民点和对照点土壤中U-238、Ra-226、Th-232等关键核素活度浓度。结果表明，厂界土壤中U-238、Ra-226、Th-232活度浓度最大值分别为 (378±15)、(207±8)、(487±19) Bq•kg⁻¹，居民点土壤中U-238、Ra-226、Th-232活度浓度最大值分别为 (337±13)、(139±6)、(233±9) Bq•kg⁻¹，伴生放射性矿开发利用企业厂界外土壤没有放射性污染；有8家企业生产活动可能使得厂界周围土壤放射性水平超过当地环境本底水平，其余企业厂界土壤放射性水平与本底水平相当，反映出部分企业生产抬升周围土壤放射性水平；或与本底水平掌握不够精细有关。约2/3企业厂界下风向土壤中放射性核素活度浓度高于敏感点和对照点，企业生产经营活动存在含放射性渣料洒落、飘逸出厂界等现象；另约1/3企业厂界下风向土壤放射性水平与周围居民点处无明显差异，企业日常辐射环境管理规范。通过对广东省伴生放射性矿周围土壤放射性水平进行分析，对伴生放射性矿开发利用企业提出日常辐射环境管理要求，向生态环境主管部门提出建议，以促进伴生放射性矿开发利用行业健康发展。

关键词: 广东省, 伴生放射性矿, 土壤, γ能谱分析, 放射性水平, 辐射环境管理