The Experimental Study On The Process And Effect To The FGD-Gypsum As An Improvement In Coastal Saline-Alkali Soil

Salinization of soil causes a low utilization of coastal saline-alkali and a huge loss in agricultural production. on the other hand, the flue gas desulfurization technology produces large amounts of by-products--flue gas desulfurization gypsum. If these by-products are disposed improperly, not only a considerable amount of utilization of mineral nutrition resources will be wasted, it’s also easy to cause secondary pollution and land use issues. If we can combine the flue gas desulfurization with the coastal saline-alkali soil, it is must be a great advantage in our sustainable development.This article 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, ion exchange process and effect of soil-gypsum system, and the changes of soil nutrients under different gypsum proportions(0%,1%,2.5%,5%, and10%) 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 was4-5times than the control and sped the process of desalination effectively; the high pH of eluent and soils are controlled effectively to down to a alkalescence level and never rebound for a long time; ion exchange exhibited actively and the conductivity of eluent fell sharply as same as the concentration of ions in the beginning of6days. Calcium ions exchanged sodium ions first in experimental groups, the average sodium removal efficiency was1.8times than the control. Meanwhile, the exchanges of calcium-potassium and calcium-magnesium were going, but less than calcium-sodium, the average removal efficiency was just more about3%than the control. The total quality of sodium in eluent was about2times than the magnesium and potassium even though the content of the later two were far more than the former in soil, this showed that the exchanges of calcium-sodium was a priority. The eluting ratio of chlorine ions was positively correlated with hydraulic conductivity, the inflection point of10%group appeared in the sixth day after leaching,4days before the control,and the eluting ratio was also about3times than it. The efficiency of saline-alkali desalination depended on total exchangeable cations mainly in soil when gypsum ratio exceeded1%. With the increase of gypsum proportion, marginal benefits of desalination were not significant. In addition, the lowest total quality of soluble phosphorus in eluent was10%group, the control is just the opposite, about2times than10%group. But the available phosphorus of them was different, control group was the highest concentration of soil available phosphorus, and the concentration decreased with the increase ratio of gypsum, to10%group to meet the minimum19.2mg/kg, but still higher than the grade I of Quality standard for greening soil(15mg/kg), can completely meet the demand of the normal growth of plants. Finally, we recommended the mass ratio of FGD-gypsum and saline-alkali soil in the process of Shanghai saline-alkali soil improvement was close to1%in a ideal condition of mixing thoroughly, the proportion could be appropriate to increase in field improvement project.