应用Multi-Langmuir模型评价土壤的表面电荷特性

用返滴定技术测定土壤的可变电荷量(Qv),应用Muti-Langmuir模型评价土壤的表面电荷特性。结果表明,黄壤和黄棕壤可变电荷量的变化范围在0～45cmolkg-1,红壤为0～21cmolkg-1,砖红壤和赤红壤为0～14cmolkg-1。可变电荷量(Qv)依赖土壤悬液的pH,3点位模型能很好地描述6种土壤的可变电荷量随pH的变化关系;黄壤、黄棕壤、湖南红壤、江西红壤、赤红壤和砖红壤的pK1分别为4.45、4.46、4.76、4.62、4.66和4.74,可变电荷量Qv1分别为11.7、9.64、9.31、7.14、4.86和5.95cmolkg-1。黄壤和黄棕壤pK1较红壤、砖红壤和赤红壤约低0.3。pK1与ZPC呈现极显著的线性关系,可变电荷量(Qv(i))与有机质含量呈极显著的正相关。

Evaluation of surface charge characteristics of soils using multi-langmuir model

Soil surface charge was measured with the potentiometric back-titration technique, and its characteristics evaluated with the Multi-Langmuir model. Results show that the variable surface charge of yellow soil and yellow brown soil varied in the range of 0~45 cmol kg^-1, of red soils in the range of 0~22 cmol kg^-1 and of latosolic red soil and latosol in the range of 0~14 cmol kg^-1, depending on pH of their respective soil suspension. The multi-Langmuir model was used to simulate surface charge, assuming that the three-site model might be adopted to describe the relationship of variable charge with pH. Of yellow soil, yellow brown soil, Hunan red soil, Jiangxi red soil, latosolic red soil and latosol, pK¹ was 4.45, 4.46, 4.76, 4.62, 4.66 and 4.74, respectively; and Q^v1 was 11.65, 9.64, 9.31, 7.14, 4.86 and 5.95 cmol kg^-1 respectively. Yellow soil and yellow brown soil was about 0.3 lower than red soil, latosolic red soil and latosol in pK¹. An extremely significant linear correlation of pK¹ with ZPC was observed and so was an extremely significant positive correlation of Q^v(i) with organic matters.