中南地区几种土壤的表面电荷特性　Ⅲ.土壤的电荷量,电荷零点(PZC)和净电荷零点(PZNC)

SURFACE CHARGE CHARACTERISTICS OF SOILS IN CENTRAL AND SOUTHERN Ⅲ.CHARGE AMOUNT,POINT OF ZERO CHARGE(PZC) AND POINT OF ZERO NET CHARGE(PZNC)

研究了中南地区3种土壤的电荷量、电荷零点（PZC）和净电荷零点（PZNC）等表面电荷性质及其与土壤矿质组成的关系。结果表明：（1）从赤红壤、红壤到黄棕壤，永久负电荷量（CECp）趋于增大，主要与土壤的粘土矿物组成和粘粒含量有关；可变负电荷量（CECv）变异趋势不明显，主要与土壤氧化铁铝的组成及含量有关；可变负电荷量占负电荷总量的比例趋于降低；正电荷量趋于减小。（2）供试赤红壤、红壤和黄棕壤的PZC分别为3．90、3．35～3．50和2．96～3．12;赤红壤和红壤的PZNC分别为3．85和2．15～2．84，黄棕壤不存在PZNC。（3）初步提出可变电荷土壤表面电荷性质的指标为：PZC＞3．0、PZNC＞2．0、PZC－PZNC＜1．0和CECv／CEC8．2＞0．4。

Liu Dong-bi (Hubei Academy of Agricultural Science. Wuhan 430064)He Ji--zheng;Liu Fan;Li Xue-yuan (Huazhong Agricultural University, Wuhan 430070)Abstract:Charge amount point of zero charge (PZC) 9 POint of zero net charge (PZNC),the relationships among the above surfaCe charge properties, and the composition of 3 types of soils in central and southern China were stUdied. ResultS showed that: (1) From lateritic soil, red soil to yellow brown soil, the Permanent negative charge amount (CECp) which chiefly relates to soil clay mineral composition tends to increase; whereas the variable negative charge amount (CECv) which mainly depends on Fe and Al oxides content of the soils shows no obvious trends; the variable negative charge to total negative charge ratio and positive charge amount tend to decrease. (2) FOr the examined lareritic soil, red soil and yellow brown soil, PZC is 3.90, 3.35-- 3.50 and 2.96-- 3.12, respectively; PZNC for the examined lateritic soil and red soil is 3.85 and 2.15-- 2.84, respectively, For yellow brown soil, there is no PZNC. (3) Surface charge indexes of variable charge soils were suggested to be PZC>3.0, PZNC>2.0, PZC--PZNC<1.0 and CECv/CEC8.2>0.4 for the soils in central and southern China.