小尺度矸石堆场及其周边土壤中放射性元素特征分析及风险评价

Characteristic and risk assessment of radioactive elements in small scale gangue dump and surrounding soil

煤矸石的露天堆放,不仅侵占大量的土地资源,还会带来严重的环境污染问题.为研究煤矸石中放射性核素对周边土壤环境的影响,采集煤矸石及矸石堆周边土壤样品,测试样品中放射性核素^(238)U、^(232)Th的活度浓度,分析煤矸石及周边土壤中放射性核素^(238)U、^(232)Th的分布特征,采用地累积指数法对土壤污染状况进行综合评价.结果表明,矿区煤矸石主要以粘土矿物为主,而粘土矿物是吸附铀、钍的关键性矿物;土壤中放射性元素^(238)U、^(232)Th活度范围分别为31.51—58.81、53.33—94.48 Bq·kg^(−1),远低于煤矸石,其活度浓度呈现出与矸石堆距离增加而减小的分布趋势;煤矸石中^(238)U、^(232)Th主要以残渣态为主,土壤样品中^(238)U赋存形态以有机结合态和碳酸盐结合态最为突出,而^(232)Th总体上以残渣态为主;地累积指数法评价结果表明,S1-S9号采样点处I_(geo)(^(238)U)在不同深度段均小于0,表明周边土壤并未受到^(238)U这种元素的污染,而靠近矸石堆的表层土壤(0—20 cm)受到^(232)Th轻微污染,其污染范围限定在距矸石堆30 m以内.

The open-air stacking of coal gangue not only encroaches on a large amount of land resources,but also brings serious environmental pollution problems.In order to study the influence of radionuclides in coal gangue on the surrounding soil,coal gangue and soil samples were collected in the gangue piles and surrounding areas.The activity concentration and occurrence of radionuclides^(238)U and^(232)Th in coal gangue and soil samples were determined.By adopting the geoaccumulation index method,the pollution indices were calculated to assess soil pollution extend.The results showed that the coal gangue in mining area was mainly composed of clay minerals,which were the key minerals to adsorb uranium and thorium;The activity ranges of^(238)U and^(232)Th in soil were 31.51—58.81、53.33—94.48 Bq·kg^(−1),respectively,which were much lower than that of coal gangue.The concentrations of^(238)U and^(232)Th in soil showed a decrease trend,with the increase of distance from gangue pile;^(238)U and^(232)Th in the coal gangue were mainly residual states.In the soil samples,^(238)U occurred in organic and carbonate states,while^(232)Th was mainly in residual state;The geoaccumulation index showed that I_(geo)(^(238)U)at sampling point S1-S9 was less than 0 in different depth,so the surrounding soil was not polluted by^(238)U,while the surface soil(0—20 cm)near the gangue pile was slightly polluted by^(232)Th,and its pollution range was limited to 30 m.