乙酸铵离心交换法和乙酸钙离心交换法测定土壤阳离子交换量

Determination of Cation Exchange Capacity of Soil by Centrifugal Exchange of Ammonium and Calcium Acetates

土壤阳离子交换量(CEC)的测定在农业中有重要的意义,对农业行业标准NY/T295—1995和NY/T1121.5—2006中的离心交换法测定土壤中CEC值的方法进行了优化,讨论了不同pH值的土壤样品对两种方法的选择依据,分析了CEC值测定重现性较差的原因。结果表明,pH值的范围是方法选择的重要依据,pH<7.0的样品适合用乙酸铵离心交换法,pH≥7.0的样品则适用乙酸钙离心交换法。优化后方法的准确度和精密度有了较大的改善,实验中对各步骤的优化缩短了约40%的操作时间,减少工作量,适合于批量样品的准确测定。

The results of Cation Exchange Capacity （CEC） for soil has important significance in agriculture. In this paper, the centrifugal exchange methods used in the agricultural industry standards of NY/T295--1995 and NY/T1121.5--2006 for CEC determination are optimized. The selection of two methods on the basis of soil samples with different pH is discussed. The reason behind the poor reproducibility of CEC determination is also analyzed. The results show that the pH range could be used as an important basis for the methods selection. The samples with pH〈7.0 were suitable for centrifugal exchange of ammonium acetate and those with pH ≥ 7.0 for centrifugal exchange of calcium acetate. Accuracy and precision of the optimized method have been greatly improved and the experimental time is reduced about 40 % by optimizing the operating steps. After the final optimization, the reduced workload is suitable for the accurate determination of a large number of samples.