淹水落干下三峡水库消落带土壤无机磷形态转化特征

为探讨三峡水库消落带土壤无机磷的转化规律,通过布置原位浮台,将装有土壤的塑料盆悬挂在不同水深(0、2、5、15m)处,分别淹没30、60、180 d,落干180 d,研究淹没水深和时长对消落带土壤的理化性质及无机磷形态的影响.结果表明,淹水-落干循环中,土壤pH、有机质、全磷和有效磷含量均呈现先降低后升高的趋势.落干180 d后,土壤pH、有机质和全磷含量降低,有效磷含量升高.土壤淹水后,各形态无机磷占全磷的比例大小为Fe-PAl-PCa8-PCa2-P.淹水0 m、2 m时Ca2-P、Ca8-P随淹水时间持续下降,淹水5 m、15 m时随淹水时间先降低后升高.落干180 d后无机磷含量显著增加,随淹水深度的增加无机磷含量呈降低趋势;Al-P含量随淹水时间先降低后持续升高,随淹水深度变化趋势不明显;Fe-P含量随淹水时间和淹水深度变化无明显规律.

Effects of Flooding and Drying on the Transformation of Soil Inorganic Phosphorus in the Water-Level-Fluctuating Zone of the Three Gorges Reservoir, China

The implementation of the Three Gorges Project formed a water-level-fluctuating zone, and flooding and drying affects the soil properties and water quality of the Water-Level-Fluctuating Zone. The laboratory simulation or field sampling were conducted; however, the results cannot reflect the real conditions in practice. The effects of flooding and drying on the physical and chemical properties of soil and the transformation characteristics of inorganic phosphorus were studied in order to provide a theoretical reference for soil phosphorus loss and water eutrophication in water-level-fluctuating zone of the Three Gorges Reservoir. To investigate the conversion of soil phosphorus, plastic pots with soil were suspended at different depths (0, 2, 5, and 15 m) and submerged for 30, 60, and 180 d, and exposed for 180 d. The effects of submerged depth and time on the soil physical and chemical properties and inorganic phosphorus forms were studied. The results showed that soil pH, organic matter, total phosphorus, and available phosphorus decreased and then increased subsequently during the flooding period. After exposure for 180 d, soil pH, organic matter, and total phosphorus content decreased, while available phosphorus content increased. After flooding, the ratio of various forms of inorganic phosphorus to total phosphorus was Fe-P > Al-P > Ca₈-P > Ca₂-P. The content of Ca₂-P and Ca₈-P decreased at 0 m and 2 m and decreased at 5 m and 15 m and then increased with increased flooding time. After exposure for 180 days, the content of inorganic phosphorus increased significantly, and the content of inorganic phosphorus decreased as flooding depth increased. Al-P content increased with the flooding time, but there was no obvious change with flooding depth. The content of Fe-P did not change with the time and the depth of flooding.