| Aquatic eutrophication is a serious environmental problem in our times. As a controlling factor of aquatic eutrophication, phosphorus is also a main factor which limits plant growing. Though overall understanding to phosphorus transportation mechanism in soil-water interface had been achieved both at home and abroad, few researches on phosphorus transportation in soil-water interface in water level fluctuating zone of the Three Gorges were reported. In order to protect water environment, and understand the transportation of phosphorus in soil-water interface in water level fluctuating zone of the Three Gorges affected by organic matter, experiments were conducted. Choosing purple tide soil, greyish brown tide soil, yellow earth soil from soil-water interface in water level fluctuating zone of the Three Gorges, adopting indoor simulation, which simulated the environmental organic matter (both water body and soil) component and water body pH influence phosphorus transportation during flooding, research put the dynamics model of the phosphorus release under organic acid influencing, have probed into shape transforming and soil, water quality and component of the soil phosphorus in the course of releasing and transporting. The result of study shows:The initial acidity of water body has important influence to the migration of the soil phosphorus. At the beginning of pH<7, the release amount of the phosphorus presented line shape to increase with the reducing of pH; and when pH = 7, the phosphorus was minimum in releasing amount; Whereas when pH>7, the release amount of the phosphorus began to rise again. Though water body initial acidity differed significantly, soil-water system acidity reached unanimity rapidly after flooding water. What merits attention is though soil-water system pH reached unanimity, the impact on release of the soil phosphorus of the initial acidity of water body has not been dispelled because of this, acidic or alkaline treatments help the soil phosphorus releasing during flooding. Therefore, discharging the acidic or alkaline waste water to the water body might promote the phosphorus release from the bottom mud or soil to water body, increased the risk of aquatic eutrophication.With low molecular weight organic acid in water, phosphorus release amount increased in soil or bottom mud to the water body. Compared treatments with P and without P, water added oxalic acid, citric acid, or tartaric acid, phosphorus density covering water of treatment with P was higher than obviously without P during flooding. Compared with the situation that there was the contrasting (CK ) of no organic acid, 3 kinds of organic acid existence could obviously promote the release of the soil phosphorus, and its function ability followed the order of OA> CA> TA, had nothing to do with the other source phosphorus that is added .Organic acid initial level thataccede to water is the remarkable positive correlation of the release of the soil phosphorus, can be described by a linear equation, after the plant source and other low molecular weight organic acid enter soil through various kinds of ways , the phosphorus release and transportation to the water body was obviously promoted during flooding . Under the purple tide soil was flooding, the relationship between the amount of released phosphorus and added organic acid &inundation time could be explained by model QRP<0.45 = α1·eβ1·O1·tλ1,Oi≤20mmol/kg) ,β1,β1 are closely related to organic acid sorption ability of soil, λ1 is positive remarkably correlation to Log kAl。Organic acid existed in water and soil influenced phosphorus release dynamics that have significant difference during flooding. Its reason may be that mechanisms of promoting the soil phosphorus to release are different. Acceding to organic acid of the water body, it is mainly that the acid dissolves function to influence soil phosphorus release during flooding; the treatments that added the organic acid in soil to play a decisive role were absorbed specially by the competition. Meanwhile , equal density organic acid added in water influence phosphorus release function that move to be more than 10 times higher to organic acid added in soil directly, this prove water body organic acid pollution influencing risk in phosphorus release is higher than soil polluted by organic acid. So, it is the key to preventing flooding water soil phosphorus from transporting to water body to control the organic acid pollution of water body.It is in close relation with soil type that phosphorus transportation is water-soil interface, the size of 3 kind soil phosphorus release ability is the purple tide soil >Greyish brown tide soil > yellow earth during flooding water entirely, which is mainly decided by fundamental property of the soil itself. Usually, soil acid is stronger, aluminium oxide or iron is higher, especially the higher the content of amorphous oxide is, the stronger the ability of absorbing the phosphorus of soil is, this may be the reason that the ability ofphosphorus release from yellow earth to the water body was worst. The size of activation ability to the different kinds of soil phosphorus of oxalic acid, citric acid and tartaric acid (density is for lOmmol/kg soil) of the same density is the purple tide soil >Yellow earth >Grayish brown tide soil.The low molecular weight organic acid transformed the fraction of the soil inorganic phosphorus obviously. A trend is that promote inorganic phosphorus fratopm difficult to be utilized by the alga transformed into easy to be utilized. As to neutral and lime soil, after flooding for 90d , compared with no added organic acid treatment, make Ca10-P in the soil transformed to Ca2-P , Cag-P, at the same time Fe-P, Al-P content were reduced, O-P content was increased; And Al-P content of the yellow earth increases after organic acid treatment. The ability size order of organic acid on soil phosphorus fraction is the oxalic acid >Citric acid >Tartaric acid.Three kinds of low member organic acid will all make Olsen-P content in the soil increased,...
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