提出用5步连续提取法分离稻田土壤样品中汞的各种形态(水溶和可交换态、铁锰氧化物结合态、有机结合态、硝酸可溶态、残渣态)。用冷蒸气原子荧光光谱法测定总汞及各种形态汞的含量。汞的质量浓度在32.0 μg·L-1以内与荧光强度呈线性关系,方法的检出限(3s)为0.022 9 μg·L-1。对方法的精密度做了试验,测定值的相对标准偏差(n=10)为1.1%。以4个土壤样品为基体,用标准加入法做回收试验,测得回收率在89.0%~94.0%之间。土壤的分析结果表明:垂直方向上5种不同形态的汞含量均随深度增加而减少;水平方向上土壤中不同形态汞含量大小依次为有机结合态、硝酸可溶态、残渣态汞、铁锰氧化物结合态、可交换态。

A method of 5-step successive extraction for separation of various species of mercury ［including: (a) soluble and changeable species; (b) Mn, Fe oxide combined species; (c) combined organic species; (d) HNO3-soluble species and (e) residual species］ in paddy field soil was proposed, and contents of the 5 species as well as the content of total mercury were determined by CV-AFS. Linear relationship between values of fluorescence intensity and mass concentration of mercury was found in the range within 32.0 μg·L-1, with detection limit (3s) of 0.022 9 μg·L-1. Precision of the method was tested giving value of RSD (n=10) of 1.1%. Recovery was also made by standard addition method, using 4 soil samples as matrixes, give results in the range of 89.0%-94.0%. As shown by the analytical results of the paddy field soil samples, the contents of the 5 species of mercury were decreased in samples with increase of depth of soil-sampling in vertical directions; and the magnitude of contents of the 5 species of mercury in samples sampled in the horizontal directions were found to decrease in the following order: species(c)>(d)>(e)>(b)>(a).