乌江流域石灰土中铀等元素形态与铀活性

SPECIATION OF ELEMENTS(eg,URANIUM) AND MOBILITY OF URANIUM IN CALCAREOUS SOILS FROM WUJIANG RIVER CATCHMENTS

以中国西南乌江流域石灰土为例，运用逐级提取（Sequential Extraction，SEE）技术，并结合化学成分和相关参数数据，研究了石灰土中铀（U）等元素的形态，并在此基础上探讨了石灰土中U的活动性及释放潜力，旨在增进对U等元素生物地球化学循环的了解，同时也为流域U污染防治提供科学依据。研究结果表明：①石灰土中Mn主要存在于锰（氢）氧化物中，Ca主要存在于碳酸盐和硅酸盐矿物中，P主要存在于硅酸盐矿物和有机质中，U主要赋存于硅酸盐等残留部分中，其次赋存于有机质结合部分和碳酸盐矿物中；②石灰土剖面中活动态U所占的比例为10％～30％，平均17％，说明石灰土中的部分U在酸性和氧化-还原界面等条件下具有一定的迁移活性，即在上述条件下，石灰土中的部分U可释放进入周围水体或植物中；③石灰土中U的潜在释放量为0．36～1．50g／t，平均U潜在释放量为0．76g／t，因此，在酸雨和侵蚀等作用下，石灰土U释放可显著提高乌江河水U通量。

Taking the calcareous soils from Wujiang River catchments of Southwest China as an example, the study investigated the speciation of elements such as uranium （U） and discussed the mobility and release behavior of U from the studied calcareous soils with a technology of Sequential Extraction （SEE） in combination with chemical composition and related parameters of calcareous soils. The main purpose of the study is to improve our understanding on biogeochemical cycling of mineral elements such as U and set a basis for water environmental protection against U pollution from natural sources especially from natural weathering of U rich bedrocks or U-rich soils by taking proper measures at a catchment＇s scale especially for Wujiang River catchments. The investigation results show that the element Mn in the studied calcareous soils is mainly bound in hydroxides of manganese, Ca is mainly bound in carbonate and silicate minerals, P is mainly hosted in silicate minerals and organic matters, U is mainly hosted in residual phases such as silicate minerals, secondly hosted in organic matters and carbonate minerals. The percentage of mobile U in calcareous soils is 10% to 30%, with an average of 17%, indicating that at least part of U in the studied calcareous soils can be released and transferred under certain acidic and oxidation-reduction surface conditions, that is, at least part of the U in calcareous soils can be released and transferred into water bodies or absorbed by low to high plants under the above surface conditions. The potential release amount of U in calcareous soils can reach to a value of 0.36-1.50 g/t, with an average of 0.76 g/t, so contribution of U flux in Wujiang River from calcareous soils under the role of accelerating soil erosion and atmospheric acid precipitation in Wujiang River catchments should never be ignored.