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首页> 中文期刊> 《生态环境学报》 >广东某铀废石堆周边土壤中铀污染特征及其环境有效性

广东某铀废石堆周边土壤中铀污染特征及其环境有效性

         
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摘要

铀（U）矿冶过程中产生了大量铀废石。通常认为其放射性核素含量低，大多沿山谷露天自然堆放，一般不对堆场做防渗漏处置，对铀废石可能产生的潜在环境影响尚未引起重视。以广东某花岗岩型铀矿山的一个废石堆周边土壤为研究对象，在废石堆上、下游方向分别采集了2条（即BP1和BP2，视作背景土壤，距离废石堆的距离分别为10和20 m）和3条土壤剖面（即WP1、WP2和WP3，视作潜在U污染土壤，距离废石堆的距离分别为50、100和180 m）。通过对剖面间U分布特征的对比，定量估算了受污染土壤中外源U的输入通量；结合逐级化学提取技术，分析了U在土壤剖面的赋存形态及其环境有效性。结果表明：1）铀废石堆对周边土壤产生了显著的放射性污染，废石堆下游方向由近及远的3条U污染剖面（WP1、WP2和WP3）中U平均质量分数比背景剖面分别富集了634.6、10和3.7倍，其外源U的平均输入通量分别为4840.36、86.72和20.46μg·g-1。距污染源（废石堆）愈近，土壤中外源U的输入通量愈大；2）在近源区，大量的外源U优先在土壤表层聚集，随着远离污染源，逐渐转变为优先在剖面的深部淀积；3）与U 污染剖面相比，背景剖面（BP2）的惰性态 U（晶质铁锰氧化物/氢氧化物结合态+残渣态）所占比例最大，活性态 U（可交换态（包括水溶态）+碳酸盐结合态）所占比例最小，说明U污染土壤的外源U输入更倾向于对活性态U的贡献，这是对植物影响最直接的部分。另外，距污染源由近及远，U污染土壤中活性态U所占比例增大，潜在活性态U（有机质结合态+无定形铁锰氧化物/氢氧化物结合态）所占比例降低；4）3条U污染剖面中，平均90%以上的U（活性态和潜在活性态）对生态系统构成了威胁。因此，铀废石堆对周边环境产生的风险应得到充分重视。本研究为开展铀矿冶地域的放射性环境影响评价和土壤修复提供了有益的参考。%There are large amounts of waste rocks produced during uranium mining and hydrometallurgy in China. As their radionuclide contents are generally considered as low, most of these rocks are stacked along the valleys and exposed to open air without percolation-proofing for the sites that store them. Currently, the potential environmental radioactive risks posed by these rocks have not yet received extensive attention. In his study, five soil profiles were selected from the area around a uranium waste rock pile in a granite-type uranium mine in Guangdong Province, China. Among them, two (i.e., BP1 and BP2 in the upstream direction of the pile, with the distances of 10 and 20 meters from the pile, respectively) and other three (i.e., WP1, WP2 and WP3 in the downstream direction, with the distances of 50, 100 and 180 meters from the pile, respectively) were used as the background and potentially uranium-polluted, respectively. Through the comparison between the uranium distributions of these profiles, the influx of exogenous uranium in the uranium-polluted soils was quantitatively estimated. In addition, the chemical speciation and environmental availability of uranium in the soil profiles were analyzed by the sequential chemical extraction procedures. The results demonstrated the following points: 1) A significant radioactive pollution to ambient soils from the uranium waste rock pile was detected. The average contents of the uranium in the downstream profiles WP1, WP2 and WP3 are about 635, 10, and 4 times as much as that of the background, respectively. On the other hand, the influx of exogenous uranium in the profiles WP1, WP2 and WP3 are 4 840.36, 86.72 and 20.46μg·g-1, respectively, indicating that the closer the profile is to the pile, the greater the influx of uranium is;2) A large amount of exogenous uranium detected at the soil surface close to the pollution source (i.e., the uranium waste rock pile) was precipitated in the deeper soil when the soil was away from the pile; 3) Compared with the uranium-polluted profiles, the background profile BP2 had the most inert uranium (i.e., crystalline ferromanganese oxide/oxyhydroxide and residual phases), but the least active uranium (i.e., exchangeable, including water-soluble, and carbonate-bound phases), indicating that the influx of exogenous uranium tended to contribute active uranium to the uranium-polluted soils, thereby producing a direct threat to plants. In addition, the active uranium increased, but the potentially active uranium (i.e., amorphous ferromanganese oxide/oxyhydroxide and organic matter-bound phases) decreased when the soil is more distant from the pollution source;4) In the three uranium-polluted soil profiles studied, over 90%of uranium (including active and potentially active) produced a threat to the ecological system. Therefore, the radioactive risk posed by the uranium waste rock piles should not be ignored. In this sense, this study provided a useful scientific reference for the environmental radioactivity impact assessment and the soil remediation in the fields of uranium mining and hydrometallurgy.

著录项

  • 来源
    《生态环境学报》 |2015年第1期|156-162|共7页
  • 作者

    张彬; 冯志刚; 马强; 陈荣; 王小龙; 段先哲; 韩世礼;

  • 作者单位

    南华大学核资源工程学院;

    湖南 衡阳 421001;

    南华大学铀矿冶生物技术国防重点学科实验室;

    湖南 衡阳 421001;

    南华大学核资源工程学院;

    湖南 衡阳 421001;

    南华大学核资源工程学院;

    湖南 衡阳 421001;

    南华大学核资源工程学院;

    湖南 衡阳 421001;

    南华大学铀矿冶生物技术国防重点学科实验室;

    湖南 衡阳 421001;

    南华大学核资源工程学院;

    湖南 衡阳 421001;

    南华大学铀矿冶生物技术国防重点学科实验室;

    湖南 衡阳 421001;

    南华大学核资源工程学院;

    湖南 衡阳 421001;

    南华大学核资源工程学院;

    湖南 衡阳 421001;

  • 原文格式 PDF
  • 正文语种 chi
  • 中图分类 土壤污染化学;
  • 关键词

    铀废石; 土壤; 铀污染; 赋存形态; 环境有效性; 广东省;

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