The Research Of Migration Regularity In Red Soil Profiles Under Simulated Acid Rain

Longhai city in Zhangzhou, Fujian Province is located in southeast China which is an industry relatively-developed and acid-rain area in China. The area, with plenty of rainfall and frequent acid rain deposition, has lead to seriously leach of nutrient elements(Ca, Mg, K, Na, etc.) and soil acidification further. It will enhance the geochemical activity of aluminum and heavy metals in soil. This will have negative effect on crop’s growth and water environmental quality, and may cause geochemical and ecological disaster.Two representative soil profiles at Longhai area were collected and did detailed in-lab leaching experiment with simulated acid-rain solution. We can come to conclusions as following:1. The weathering degree is high in the study area. The major elements(Ca,Mg, K, Na) are leaching away largely. Aluminium is relatively enriched as the result of soil development. The weathering degree reached at the stage of Si loss and Al enrichment. It is found that the concentrations of micro-elements in soil profiles are mainly controlled by major elements. 2. Element concentration in leaching solution will increase as the acidity of leaching solution increases. The element concentration in leachate solution will also increase as the leaching solution goes down from top soil layer to deeper layers. However, as the leaching experiment goes on, element concentration of in solutions tends to decrease. 3. According to the soil-solution partition coefficient and the concentration of major elements in the leachate,elements can be divided into three groups:(1) Ca, Mg, K, Na,(2) Al, Fe,(3) Si. Group(1) is of higher geochemical activity under supergene condition, which can easily dissolve into solution in the process of leaching. Group(2) and(3) is of weak geochemical activity.4. It is found that the concentrations of micro-elements in leachate solution are also mainly controlled by major elements in soil. According to dissolved concentrations in the leachate trace elements can be divide into four groups:(1) Cu, Cd, Hg, Ni, Pb, U,(2)Cr, Ti, Zr, As, F, P,(3) B(4) S, Se. The element concentrations of group(1) in leachate are controlled by Ca, Mg, Na, Al and K. The elements of group(2) are controlled by Fe and group(3) are controlled by Si. 5. The p H values for the two profiles decreased as leaching depth increase, which is considered as the result of aluminium dissolution significantly.As the soil in study area is strongly acidic, acid rainfall will acidify the topsoil further. It will cause heavy metals and aluminium mobilization, and increase the concentration in water and uptake by plants. So it seems that there is high ecological risk from acid precipitation.