摘要
分別采用1mol L^(-1) NH_4OAC淋洗法,0.1mol L^(-1)BaCl_2捕掳交换法,6.667×10^(-3)mol L^(-1)Co(NH_3)_6Cl_3提取法以及电荷测定法测定了南方几种不同性质的土壤的阳离子交换性质。结果表明,酸性土壤的阳离子交换量具有不定性,NH_4OAC法的结果很高,而其它方法的结果显著偏低,但方法间仍存在显著差异。不过,各法对微酸性、中性土壤的测定结果无显著差异。与NH_4OAC法相比,BaCl_2法得到较多的Ca,而Co法则交换出较少的K。各法的浸提液pH间虽存在差异,但彼此间有良好的统计相关性。Co法测定的CEC值与交换性阳离子总和较为吻合,其浸提液pH与pH_(KCl)、pH_(CaCl_2)有良好的线性关系。看来,不同方法对酸性土壤阳离子交换量的测定差异主要来自測定过程中介质pH条件及离子强度不同所浸出的交换性酸的多寡。本文认为,Co(NH_2)_6Cl_3法可以作为这些土壤阳离子交换性质测定的例行方法。
We used 1 mol L^(-1) NH_4 OAC buffer, 0.1 mol L^(-1) BaCl_2 with MgSO_4 and 6.667×10^(-3) mol L^(-1) Co (NH_3)_6Cl_3 unbuffered solutions, and charge titration methods respectively to determine the cation exchange properties of the soils from South China. The reaction of the soils studied ranges from acid to neutral. For the acid soils, much higher values of CEC_(NH_4) were obtained than those of CECe, CEC_(Ba), CECco and CEC_(p+v). The differences between these CEC values were statistically significant, and attributed to the difference of the exchangable acids removed by different methods. On the contrary, quite similiar results arrived for the slightly acid to neutral soils with different methods. Compared with the NH_4 OAC buffer, BaCl_2 seemed to repel much more exchangable Ca while Co(NH_3)_6Cl_3 to have less exchangable K. Except for Co(NH_3)_6Cl_3 method, there was always inconsistency between CEC and the sum of exchangable cations. The pH of the Co(NH_3)_6Cl_3 extraction was close to the soil pH in water and had a good correlation with·pH(KCI), pH(CaCl_2) and pH by BaCl_2 compulsive method. The Co(NH_3)_6Cl_3 method, therefore, is recommended to use in conventional measurement of cation exchange properties of these soils because of the simplicity, rapidity and save of reagents.
基金
国家自然科学基金
关键词
土壤
阳离子交换量
测定
南方地区
Cation exchange capacity, Exchangable cations, Exchangable acids, Soils in South China, Testing method
