氧化还原循环过程中沉积物磷的形态及迁移转化规律

为研究沉积物在氧化还原循环过程中磷循环迁移转化机制,通过控制实验模拟分析氧化还原条件下,上覆水理化性质变化特征、沉积物各形态磷变化及机制研究,并量化沉积物中磷的重新分配和沉积物磷酸盐的释放通量影响.结果表明:(1)氧化还原电位Eh和p H体系、硫体系、碳体系以及与磷相关性密切的铁体系变化规律具有周期性,并对解释沉积物-水两相界面磷的迁移转化机制有重要作用;(2)在氧化还原循环过程中,各形态磷含量随着氧化还原条件和时间变化,根据水-沉积物磷素变化量化分析可得,可还原态磷(BD-P)和铁铝结合态磷(Na OH-rP)是可逆地重新分配到弱吸附态磷(NH4Cl-P)、聚磷/有机磷(Na OH-nrP)、残渣态磷(Rest-P)和间隙水溶解性活性磷(SRP)中,且沉积物中变化量93. 7%的磷在还原反应时不会释放到水体中;(3)上覆水总磷(TP)浓度变化的92%为上覆水的SRP,表明水-沉积物在该循环过程中以水溶性磷交换为主;(4)根据Fick第一定律得,还原阶段磷扩散通量最大值为0. 58 mg·(m~2·d)-1,而氧化阶段第7 d扩散通量约为0. 16～0. 22 mg·(m~2·d)-1;氧化反应阶段,扩散通量随时间逐渐降低,还原阶段的变化趋势相反,表明还原状态会加速沉积物磷的扩散程度,而曝氧降低了沉积物磷扩散通量.

Speciation and Transformation of Phosphorus in Sediments During the Redox Cycle

To study the mechanism of phosphorus cycling in sediment during the redox cycle, changes in physicochemical properties of overlying water and various forms of phosphorus in sediments were investigated as a way to quantify the redistribution of phosphorus. Additionally, the effect of the release flux of phosphate from sediments under controlled redox conditions was analyzed. The results showed that the redox potential Eh and the pH system, sulfur system, carbon system, and iron-related changes exhibited periodicity and played an important role in explaining the migration and transformation mechanism in the interface phosphorus of the sediment-water phase. During the redox cycle, the phosphorus content of each species varied with the redox conditions and time. Because of this, quantitative analysis based on changes in water-sediment phosphorus could be obtained. Reducible phosphorus (BD-P) and iron-aluminum-bound phosphorus (NaOH-rP) were reversibly redistributed into weakly adsorbed phosphorus (NH₄Cl-P), polyphosphorus/organophosphorous (NaOH-nrP), residual phosphorus (Rest-P), and interstitial water-soluble active phosphorus (SRP). Additionally, 93.7% of phosphorus in the sediment was not released into the water phase during the reduction reaction. The 92% of change in the overlying water total phosphorus (TP) was the SRP of overlying water, which showed that the exchange of the sediment-water phase were mainly soluble active phosphorus in this cycle. According to Fick''s First Law, the maximum phosphorus flux was 0.58 mg·(m²·d)^-1 during reduction and 0.16-0.22 mg·(m²·d)^-1 on day seven of the oxidation phase. In the oxidation stage, the diffusion flux decreased with time, while the opposite trend occurred in the reduction reaction. This indicated that the anaerobic state accelerated the diffusion of phosphorus in sediments, and that oxygen exposure decreased the phosphorus flux in sediments.