氧化铝对红壤正、负电荷的影响

EFFECT OF ALUMINUM OXIDES ON POSITIVE AND NEGATIVE CHARGES IN RED SOILS

用人工合成氧化铝包被土壤的方法研究了氧化铝(三水铝石)对红壤地区五种土壤的电荷性质的影响。结果发现,土壤包被氧化铝后正电荷有不同程度的增加,但其增加量随pH的升高而减少,pH7左右时几乎为零。人工氧化铝对负电荷的影响因土而异。带负电荷少的砖红壤包铝后在pH<7范围内负电荷稍有减少;带负电荷多的黄壤和红壤包铝后在低pH时负电荷明显减少,而高pH时负电荷明显增大;另外两个赤红壤包铝后负电荷也有类似的变化趋势,但变幅较小。四种土壤的负电荷由减小转变到增大时转变点的pH值各土不同,在pH3.6—6.2之间。包铝后土壤净电荷的变化趋势与该土壤的负电荷相似。包铝后土壤的ZPNC都有所升高,升高的幅度因土而异,在0.4—1pH单位之间。

Effects of synthetic aluminum oxides (gibbsite) on positive, negative charges, and zero point of net charges (ZPNC) in five soils from southern China were studied by way of coating.After coating with aluminum oxides, positive charges of these soils increased to varying degrees. But the increments reduced with the increase of pH value. When pH value was about 7, positive charges of four soils approched to zero, but there were still a few positive charges in the latosol.The effects of coating with aluminum oxides on the changes in negative charge in the five soils .were different. Negative charges decreased slightly in latosol with less negative charges in the range of pH<7. On the other hand, the negative charges in yellow earth and red soil with more negative charges decreased and increased obviously at low pH and high pH respectively. Similar changes of negative charge were also found in the rest two lateritic red soils, but the ranges of changes were smaller. The pH values at which negative charges changed from decrease to increase were different in four soils, and the pH ranges were within 3.6—6.2.Moreover, the tendency of change in net charge was similar to that of negative charge in each soil. ZPNC of five soils were higher after coating with Al_2O_2, but their increments were different. For example, it was 1.0, 0.7, and 0.4 units for red soil, yellow earth and lateritic red earth (guangzhou) respectively.