落干期三峡库区消落带泥沙有机磷矿化特征

Organic phosphorus （OP） functions as the long-term secondary source for bioavailable phosphorus. The OP mineralization simulates phosphorus release from sediments and therefore affects the level of eutrophication in the received water.Ｔhe water-level-fluctuation zone of the Three Gorges Reservoir exposed in summer, which contributes one-third porption to the reservoir's total flooded area, serves as a key area for enrichment and transformation of the sediment and diffuse pollution associated with phosphorus. Our previous study indicated that the OP mineralization in the sediments would play an important role in transforming internal phosphorus when the water-level-fluctuantion zone exposed in summer. However, little information is known about the characterisitcs as well as the dominant impact factors in the process of OP mineralization.In this study, the sediments deposited on the slope soils will be sampled along the altitudes ranged from 145m to 175m, when the water-level-fluctuation zone freshly exposed in summer. The sediment properties (particle-size-distribution, total phosphorus, organic matter) and contents of OP and its different forms, environmental factors (water content, temperature, Eh, pH) were determined during the process of a laboratory-scale experiment simulating alternating drying and rewetting. Variations of both OP mineralization rates and transformation of different OP forms, will be discussed with response to sediment properties (particle-size-distribution) and environmental factors (temperature, water content).Subsequently the main charcteristics of OP mineralization will be interpreted for exploration of the dominant factors in the process of OP mineralization. This study would provide evidences to ackonwledge the transformation mechanism of internal phosphorus in the large reservoirs impacted by water level fluctuation, and to predict the reservoir's water quality affected by leaching or erosion of drying sediments in the water-level-fluctuation zone of the Three Gorges Reservoir.

有机磷是生物有效磷的二次来源和长期来源。有机磷矿化促使泥沙磷释放，直接影响水体富营养化水平。夏季出露的三峡水库消落带（占受淹总面积的三分之一）是库区泥沙与磷面源污染富集和中转的关键地带。我们前期研究发现：有机磷矿化是落干期消落带泥沙磷内源转化的关键进程，但有机磷矿化过程的特点及影响因素有待研究。本研究选择典型缓型坡裸露的土质消落带，在消落带出露初期沿海拔高度（145m-175m）采集落淤泥沙样品，进行干湿交替室内模拟实验，测试泥沙特性（粒径组成、总磷、有机质）、环境因子（温度、水分、Eh、pH）和有机磷总量及分级形态。研究分析泥沙特性（泥沙粒径组成）、环境因子（温度、水分）对有机磷矿化率、有机磷形态转化的影响规律，阐释落干期三峡库区消落带泥沙有机磷矿化特征及主导因素，为认识大型水库水位变化下落干泥沙磷内源转化机制，预测落干期三峡水库消落带泥沙的淋溶侵蚀对库区水质的影响提供理论依据。