氢氧化镁铝改良滨海盐碱土机理与效果研究

Effects and related mechanisms of magnesium aluminum hydroxides on the improvement of coastal saline-alkali soil

从土壤微观层面研究氢氧化镁铝(MAH)和盐碱土胶体间的扩散层重叠现象,并通过不同配比的MAH[Mg∶Al摩尔比分别为3∶1(MAH-1)、2∶1(MAH-2)、1∶1(MAH-3)、1∶2(MAH-4)和1∶3(MAH-5)]和盐碱土的盐分溶出实验筛选出最佳改良方案。结果表明:MAH和盐碱土胶体间存在扩散层重叠现象,并且该现象在碱性环境中依然存在,混合体系pH值和MAH添加量是影响重叠程度的两个重要因素;5种MAH都能降低盐碱土的pH值和含盐量,酸性MAH对盐碱土的改良效果优于碱性MAH,其中酸性最强的MAH-5改良效果最显著;MAH-5在最小添加量10 mg·g^(-1)下就能脱出65%的交换性Na,并且随着添加量增加变化不显著,但随添加量增加Ca2+和N都显著脱出。因此,通过添加MAH利用扩散层重叠降低土壤对盐基离子的吸附实现盐碱土脱盐改良,综合考虑筛选出最佳改良方案:按1%配比添加MAH-5。

This study investigated the overlapping of diffuse layers between magnesium aluminum hydroxide(MAH)and saline-alkali soil colloids in the soil microstructure.The best improvement measure was determined via the salt dissolution experiment,using soils with differ ent ratios of MAH[Mg∶Al=3∶1(MAH-1),2∶1(MAH-2),1∶1(MAH-3),1∶2(MAH-4),and 1∶3(MAH-5)].The results confirmed the existence of the overlapping of diffuse layers between the MAH and saline-alkali soil colloids,even in an alkaline soil environment.The pH and amount of MAH were important factors affecting the overlapping behavior.All five amounts of MAH decreased the pH and salinity of the saline-alkali soil.The improvement effect of acidic MAH on the saline-alkali soil was significantly greater than that of alkaline MAH;MAH-5,which had the highest acidity,had the most significant improvement effects.At the minimum addition of 10 mg·g-1 of MAH-5,65%of the exchangeable Na was removed in the soils,and the removal efficiency did not significantly increase with increasing amounts of MAH-5.However,the amounts of Ca2+and N removed significantly increased with increasing amounts of MAH-5 addition.Therefore,the addition of MAH could reduce the adsorption of salt-based ions through the overlapping of diffuse layers,and consequently improve the sali nation of saline-alkali soil.The most effective measure was determined to be the 1%addition of MAH-5 to soil.