不同pH 值下底泥-水体-凤眼莲系统磷释放与迁移规律研究

实验以凤眼莲(Eichhirnia crasslpes)-水体-底泥系统为研究对象,探讨了pH 值为6.0、7.5、9.0 和10.5 条件下,各系统内各组分(凤眼莲、水体、底泥)中总磷(TP)含量变化和释放的规律。实验结果表明:底泥TP的释放受pH值影响很大,即碱性条件下释放量最大,近中性的释放量最小;随pH 值由低到高,种养凤眼莲各处理底泥TP 的释放量较空白对照分别增加了7.40、6.73、7.33mg·kg^-1和1.13 mg·kg^-1。水体TP 变化是底泥释放和凤眼莲吸收作用平衡后的外观表现,并不单独决定于某一因素,如pH 值在6.0~9.0 范围内,种养凤眼莲处理水质净化优于空白对照,其降低范围在0.03~0.27 mg·L^-1之间;pH 值为10.5 时,种养凤眼莲处理水质净化劣于空白对照。在凤眼莲正常生长的前提下,其吸收吸附是系统可移动TP的主要去向,占系统可移动磷的73.12%~79.06%,但极端碱性条件下,凤眼莲死亡后腐烂产生的TP也是系统可移动TP 的来源之一。

Release and Migration of Phosphorus in a Sediment-Water-Eichhirnia Crasslpes SystemUnder Different pHValue

This work was conducted to study the release and migration of total phosphorus(TP)in a sediment-water-Eichhirnia crasslpes system with pH at 6.0, 7.5, 9.0 and 10.5. The variation of TP concentrations and the characteristics of TP migration were analyzed in each of the system elements, i.e., the Eichhirnia crasslpes plants, the water, and the sediment. Results showed that TP release in the sediment was greatly affected by pH. The maximum and minimum amounts of release were observed under alkaline and approximately neutral condition, respectively. TP release content were 7.40, 6.73, 7.33 mg·kg^-1 and 1.13 mg·kg^-1 higher in the sediment of sediment-water-Eichhirnia crasslpes system than in the sediment without Eichhirnia crasslpes(the control), with pH at 6.0, 7.5, 9.0 and 10.5, respectively. The observed TP con-centration in the water was influenced by both the release from the sediment and the assimilation by the plants. When the pH ranged between 6.0 and 9.0, water quality purification was more effective in treatments with Eichhirnia crasslpes than in the control, where TP content was reduced by 0.03~0.27 mg·L^-1. When pH reached 10.5, however, opposite results were obtained. TP was reduced mainly by assimilation and adsorption by Eichhirnia crasslpes in the system, which accounted for 73.12%~79.06% of the removable phosphorus, when the plants were under normal growth conditions. However, when Eichhirnia crasslpes died in extremely alkaline conditions, the rotten plants became one of the sources for removable phosphorus in the system.