三峡水库水体溶解磷与颗粒磷的输移转化特征分析

根据河流上、下游断面间水、沙和磷的输运系数差异,建立了一种分析河流水体磷的输移转化特征的判定方法.基于2015年1月(枯水期)和7月(丰水期)三峡水库的径流量、输沙量和水体磷形态数据,应用该方法分析了三峡水库水体磷的输移转化特征.结果表明,两个水期三峡水库水体均以TDP为主要磷形态,TDP通量占总磷(TP)通量的51%～96%;枯水期,三峡水库TDP表现为移出作用,主要由三峡拦坝蓄水促进泥沙颗粒吸附TDP引起,丰水期则表现为添加作用,与外源性含高浓度TDP的水量输入有关.在两个水期,三峡全库区泥沙和TPP均呈明显的沉降滞留特征,且TPP相对于沙量呈添加作用,一定程度上说明TDP被泥沙颗粒吸附而转化为TPP作用相对更强.三峡水库清溪场至万州段为水、沙和磷的主要滞留区域,与该区段泥沙颗粒粒径细化、颗粒吸附磷能力增强有关.

Analysis of Transport and Transformation Characteristics Between Dissolved Phosphorus and Particulate Phosphorus in Water of the Three Gorges Reservoir

To understand the difference between transport coefficients of water runoff, sand discharge, and phosphorus flux in each subsection of a river, a judgement method for analyzing the characteristics of phosphorus transport and transformation in water of rivers was established in this study. Based on the measured data of water runoff, sand discharge, and phosphorus fraction concentrations in the water of the Three Gorges Reservoir (TGR) in January and July 2015, characteristics of phosphorus transport and transformation in the water were analyzed by using the conceptual method. The results showed that the predominant phosphorus fraction in water of the TGR was total dissolved phosphorus (TDP), which accounted for 51%-96% of total phosphorus in water. The TDP flux relative to runoff in the TGR decreased in January 2015 That was caused by the adsorption of TDP by suspended particles in the dry season. In contrast, TDP flux showed additive effect relative to water runoff in July 2015 due to exogenous water inputs with high TDP concentrations in the wet season. Both sand and total particulate phosphorus (TPP) presence in the water showed obvious sediment and retention characteristics during the two periods. The TPP flux presented an additive effect relative to sand discharge, meaning that the major transformation direction of phosphorus fractions was from TDP to TPP. The subsection between Qingxichang and Wanzhou was the main retention area of water, sand, and phosphorus in the TGR, which can be associated with the enhancement of phosphorus adsorption capacity caused by particle size reduction of suspended particles in the subsection.