水位对密云水库消落区土壤磷通量影响的模拟研究

南水北调来水引起的水库水位变化导致消落区幅带变化,这直接会影响土壤中磷的转化及通量.本研究采集了陆相和水相分别离水界面1 m和2 m处的4种土柱样品,分别用来模拟消落区淹水和落干情景.在实验室内逐步模拟水位上升或下降,模拟期为9个月,并在每隔3个月的期间收集样品进行分析测试,以研究土壤中无机磷的转化规律.结果表明,密云水库受人为干扰相对较小,与三峡库区相比消落带土壤中总磷含量偏低.模拟过程中,土壤中的无机磷含量始终占总磷含量的50%以上,即无机磷为主要形态.淹水模拟过程中,不同土柱及不同深度的土壤中铁磷的变化复杂,反映了铁磷的含量易受pH、氧化还原电位、有机质等多因素影响.落干模拟过程中,土壤中铁磷和钙磷的变化最为明显,9个月的模拟期后,铁磷的含量较初始值下降了53%~71%,钙磷在土柱表层样品中的含量逐渐减小,而在中层和下层中的含量有所上升.无论是淹水还是落干过程,离水界面1 m内的陆相和水相消落区土壤中磷的转化最为活跃.在模拟的9个月期间,水库淹水期陆相1 m内消落带土壤总磷通量为82.3 kg,铁磷通量为-30.7 kg,铝磷通量为-44.8 kg,钙磷通量为222.6 kg,总无机磷通量为126.5 kg,即消落带土壤中铁磷和铝磷有所释放或转化,而钙磷、总无机磷和总磷皆有所增加.

Impact of water level on phosphorus flux in water level fluctuating zone at Miyun Reservior

South-to-North Water Division Project caused the water level fluctuating area to be larger, which would influence the transformation and loads of phosphorus in soil. In this study, soil core was used to simulate the flooding and drying situation. The soil core samples were collected from 1 m and 2 m up and down from water interface, using which the water level was simulated to be up or down in the 9 months period. Samples were collected each 3 months and the inorganic phosphorus and species were analyzed to study the transformation of phosphorus. The results showed that phosphorus contents in water level fluctuating zone of Miyun Reservoir was relatively low comparing with the Three Gorges Reservoir probably because Miyun Reservoir was less influenced by human activity. During the flooding simulating period, the ratio of inorganic phosphorus content to the total phosphorus was always more than 50%. That is to say inorganic phosphorus was the main species in the soil. The Fe-P content changed complexly during this period indicating it was easily influenced by pH, ORP, organic matters etc. During drying simulating period, the Fe-P and Ca-P contents changed dramatically. After 9 months of simulating period, the content of Fe-P decreased by 53%~71%, the Ca-P content in the top layer of the core gradually decreased while increased in the medium and deep layers. No matter for flooding or drying situation, phosphorus transformation was most active in the 1m up and down from the water interface. During the 9 months period, the total phosphorus, Fe-P, Al-P, Ca-P, total inorganic phosphorus flux was 82.3, -30.7, -44.8, 222.6, 126.5 kg, respectively. That is to say Fe-P and Al-P were transformed or released while Ca-P, total phosphorus and total inorganic phosphorus loads were increased.