生态塘底泥磷吸收/释放行为及作用机制

Adsorptive/releasing behaviors and mechanisms of sedimentary phosphate in multi-pond treatment system

研究pH和Eh对复合生态塘系统表层底泥磷吸收/释放行为的影响,考察不同pH和Eh下各形态磷的吸收/释放潜力及其相关机制,详细探讨Eh逐渐升高对铁磷(Fe-P)形成过程影响.结果表明,不同pH下底泥对各形态磷的束缚力差异明显:铁磷和铝磷在pH=7和pH=8时结合能力最强;碱可提取有机磷(OPalk)在pH=5时结合能力最强;而钙磷在pH=9结合能力最强.Eh主要通过改变Fe(Ⅱ)和Fe(Ⅲ)的相对含量及磷的形成机制影响底泥对磷的吸收/释放.随着Eh由-650 mV升高到-50 mV,Fe(Ⅱ)逐渐氧化为Fe(Ⅲ),而Fe(Ⅲ)的还原受腐殖质络合所抑制,底泥中以P-Fe3+-O-HS-M+形式存在的Fe(Ⅲ)-P显着增加.

Effects of pH and Eh on the adsorptive/releasing behaviors of sedimentary phosphate were studied. The adsorptive/releasing potential under different pH and Eh conditions was investigated and possible mechanisms involved were also proposed for different phosphate fractions. Additionally, the formation mechanism of iron - bound - phosphate with Eh steadily increasing was discussed. Results of this study showed that the binding capability of each phosphate differed greatly under different pH conditions as follows ： iron - phosphate （ Fe - P） and aluminum -phosphate （Al -P） exhibited highest binding capability with pH ranging from pH = 7 to pH = 8 ; organic phosphate extracted by alkaline solutions （ OPalk ） and calcium - phosphate （ Ca - P） showed highest binding capability at pH = 5 and pH = 9, respectively. Mainly through affecting the fractional proportion of Fe（Ⅱ） to Fe（Ⅲ） and their possibly binding forms with phosphate, Eh significantly affected the adsorptive/releasing behaviors of sedimentary phosphate. With Eh increasing from - 650 mV to - 50 mV, Fe（Ⅱ） was gradually oxidized to Fe（Ⅲ） and the reduction of Fe（Ⅲ） was inhibited due to humic covering on their surface. Consequently, Fe（Ⅲ） - P, possibly existed in the form of P - Fe^3＋- 0 - HS - M^＋ , apparently elevated with Eh increasing.