乌江流域沉积岩风化过程中铀的富集与释放

以乌江流域石灰岩、白云质灰岩、白云岩、硅质岩、黑色页岩和紫色砂岩等典型岩石的13条风化剖面为对象,运用相关分析和质量平衡计算方法,研究了这些岩石风化过程中铀(U)的富集与释放及其对河水U分布的影响,旨在增进对U生物地球化学循环的了解,也为流域U污染防治提供依据.结果表明,①乌江流域风化物和土壤中U的富集程度基本上高于上陆壳(upper continental crust,UCC)、中国土壤(China soil,CS)和世界土壤(world soil,WS);②U的富集和释放能力与母岩U含量以及风化剖面中粘土矿物和铁氧化物/氢氧化物含量及吸附能力有关;③石灰岩以及少量白云岩和碎屑岩风化过程中U的释放对河水U的分布特征具有重要的控制作用.

Enrichment and Release of Uranium during Weathering of Sedimentary Rocks in Wujiang Catchments

Thirteen weathering profiles of typical rocks such as limestone,dolomitic limestone,dolomite,sillcalite,black shale and purple sandrock from Wujiang catchments were selected for discussing enrichment and release behavior of uranium(U) during rock weathering,and studying its impact on riverine U distribution in the catchments during weathering of these rocks with methods of correlation analysis and mass balance calculation.The purpose of this study is to improve our understanding on biogechemical cycling of U and set a basis for catchment protection against U pollution.The results show that the enrichment extent of U in soils from the Wujiang catchments is usually higher than that of upper continental crust(UCC),China soil(CS) and world soil(WS).The ability of enrichment and release of U is partly controlled by content of U in bedrocks,contents and adsorption ability of clay minerals and Fe-oxides/hydroxides in weathering profiles.Our study also reveals that release of U mainly from weathering of limestone and partly from weathering of dolomite and clastic rocks exerts an important control on riverine U distribution.