| The basic properties, clay mineral association and surface charge properties for zonal soils in china, including yellow cinnamon soil, yellow brown soil, brown red soil, red soil and latosol, were investigated. The effects of organic acids (acetic acid, oxalic acid, citric acid, tartaric acid) on surface charge properties and second adsorption of cadmium for different soils were also studied. The main results were shown as follows:1. The organic matter content of the examined soils followed the Series: latosol (43.5g/kg)>red soil(26.7g/kg)>brown red soil(17.3g/kg)>yellow brown soil(16.7g/kg) > yellow cinnamon soil(9.6g/kg). The clay content of yellow brown soil (320g/kg) was the lowest, and that of latosol(780g/kg) was the highest. For the clay association, the prominent clay mineral in yellow cinnamon soil and yellow brown soil was hydromica(75~80%), whereas the main clay mineral in latosol was kaolinite(95%).From north to south, the expansive minerals changed regularly from montmorillonite to vermiculite, then to 1.4nm integrade mineral. Gibbsite was present in latosol. The Fe and Al content extracted by DCB solution tends to increase from yellow cinnamon soil to latosol.2. The amount of negative charge increased with the increasing of pH value, while that of the positive charge decreased. At the same pH value, the negative charge of the examined soils tended to decrease from north to south, whereas the positive charge increased. The latosol bore variable negative charge as predominant charge, and the brown red soil and red soil bore not only somevariable negative charge, but also some permanent negative charge. The negative charge was not significantly pH-dependent in yellow cinnamon soil and yellow brown soil. The magnitude of PZNC for the latosol is 4.2, but that for other soils was not detectable in the experimental pH range. The magnitude of PZC tended to increase from yellow cinnamon soil to latosol.3. Isotherms for adsorption of tartaric acid on yellow cinnamon soil and yellow brown soil belonged to "H type", which was called as high affinity type. With the content of tartaric acid in solution increasing from 0 to 4.8mmol/L, the sorption capacity on yellow brown soil was lower than that on yellow cinnamon soil. Isotherms for adsorption of oxalate on red soil also belonged to "H type", and that on yellow brown soil and brown red soil belong to "L type", which was behalf of low affinity type. The adsorption of oxalate on latosol belonged to "C type", which was behalf of high affinity type. According to the Langmuir equation, the maximum sorption capacity of oxalate on soils was: latosol (54.39mmol/kg) > yellow brown soil (27.11mmo/kg) > brown red soil (18.81mmol/kg) > red soil (11.48mmol/kg).4. After yellow cinnamon soil and yellow brown soil adsorbed organic acids, their negative charge quantities decreased if compared to that of original soils , and the positive charge changed slightly, whereas the magnitude of PZC increased. The effects of different organic acids on surface charge of permanent charge soil in order was: oxalic acid > tartaric acid > acetic acid > citric acid. After brown red soil, red soil and latosol adsorbed organic acids, their negative charge increased if compared to that of original soils, whereas the positive charge and the magnitude of PZC decreased. The magnitude of PZNC for latosol decreased about 0.3 pH compared to that of original soil. The effects of different organic acids on surface charge of variable charge soil in order was: citric acid > tartaric acid >oxalic acid > acetic acid. At different contents of organic acids, the effect of the high content organic acids was stronger than that of low content ones.5. The adsorption isotherms for Cd2+ on soils were in agreement with the Langmuir equation (R2>0.95, n=7). The maximum sorption capacity of Cd2+on soils followed the series: yellow cinnamon soil (1146g/kg)> brown red soil (611.6g/kg) > yellow brown soil (593.9g/kg) > latosol (463.6g/kg) > red soil (453.8g/kg). Ad...
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