脱硫石膏改良滨海盐碱土的脱盐过程与效果实验研究

针对上海滨海盐碱土的特点,借助土柱淋洗试验方法,研究了脱硫石膏改良滨海盐碱土的脱盐过程与效果,分析了不同石膏质量配比条件下(0%,1%,2.5%,5%和10%),土壤团粒结构和水力传导度变化以及盐碱土-脱硫石膏体系中的离子交换过程与效率.研究结果表明:加入脱硫石膏之后,盐碱土团粒结构得到改善,孔隙度变大,水力传导能力增强,平均导水系数是对照组的4~5倍,有效加快脱盐过程;在土柱开始淋洗的前6d内,离子交换过程表现最活跃,淋洗液的电导率和离子浓度急剧下降.添加脱硫石膏的土柱中钙离子优先置换出钠离子,平均脱钠效率达到对照组的1.8倍.钙钾离子交换和钙镁离子交换也同步发生,但规模明显小于钙钠离子交换.当脱硫石膏质量配比超过1%时,盐碱土的脱盐效果主要取决于原土中的交换性阳离子总量.随着配比增加,盐碱土脱盐的边际效益增加量并不显著.在充分混匀的理想条件下,建议上海滨海盐碱土改良过程中添加脱硫石膏的质量配比高于1%为宜.

The experimental study on the process and effect to the FGD-gypsum as an improvement in coastal saline-alkali soil

Studied the process and efficiency of desalination in FGD-gypsum as an improvement in coastal saline-alkali soil, analyzed the changes of soil’s aggregation and Hydraulic conductivity, and ion exchange process and effect of soil-gypsum system under different gypsum proportions (0%, 1%, 2.5%, 5%, and 10%) with the testing method of leaching aimed at characteristics of coastal saline-alkali soil in Shanghai. The result showed that soil aggregation has improved obviously, porosity has increased, soil hydraulic conductivity has enhanced, the average water diffusivity of soil was 4-5times than the control and sped the process of desalination effectively; ion exchange exhibited actively and the conductivity of eluent fell sharply as same as the concentration of ions in the beginning of 6days. Calcium ions exchanged sodium ions first in experimental groups, the average sodium removal efficiency was 1.8times than the control. Meanwhile, the exchanges of calcium-potassium and calcium-magnesium were going, but less than calcium-sodium. The efficiency of saline-alkali desalination depended on total exchangeable cations mainly in soil when gypsum ratio exceeded 1%. With the increase of gypsum proportion, marginal benefits of desalination were not significant. Finally, we recommended the mass ratio of FGD-gypsum and saline-alkali soil in the process of Shanghai saline-alkali soil improvement was close to 1% in a ideal condition of mixing thoroughly, the proportion could be appropriate to increase in field improvement project.