湿地基质-水界面中磷的迁移特征

Transfer Characteristics of Phosphorus between Sediment-Overlying Water of the Wetland

以湿地基质为对象,采用静态试验,用湿地原水作为进水,对湿地基质-水界面上磷的迁移进行了模拟,对静态试验前后基质中磷形态组成的动态变化和差异进行了试验研究。首先,在不同初始浓度条件下,进行了基质-水界面磷的静态迁移试验。在此基础上,对静态试验前后基质各形态磷进行了分析测定。静态迁移试验结果表明,基质中磷的迁移在24 h内均可达到平衡;24 h之后再延长湿地中污水的停留时间,并不能增加基质对污水中磷的吸附量。因此,在外界条件一定时,湿地基质磷的迁移过程均在一定时间内达到吸附/解吸平衡,而与上覆水磷初始浓度大小无关。由基质各形态磷测定结果可知,铁磷和钙磷是基质-水界面内源磷释放的主要来源。其中,铁磷是基质磷中最不稳定的形态,钙磷在一定的pH值条件下也较容易发生转化。其他几种形态磷含量较少,试验前后基质中的含量变化几乎可以忽略不计。因此,基质自身特性对于内源磷释放的影响,主要取决于基质中铁磷和钙磷的含量,在对湿地基质进行筛选时,须考虑基质自身特性。

The sediment of .the wetland was selected as study media and the original water in wetland was used as inflow in this experiment. The simulation on the phosphorus transfer in the interface of wetland sediment-overlying water was carried out by static experiment. The experimental study on the dynamic changes and difference of phosphorus form in the sediment of pre and post static experiment was also done. Firstly, the static transferring experiments were carried on under different initial concentrations. Analysis and determination of various forms of phosphorus in the sediment of pre and post experiment had been done based on this experiment. The experimental results of static transfer had shown that the phosphorus transfer of sediment had reached equilibrium within 24 h. Even though the residence time of sewage of wetlands prolonged after 24 h,the adeorption quantity of phosphorus in the sediment from sewage had not been increased. Therefore,the transfer proeess of phosphorus of sediment reached equilibrium under certain external environment and had no correlation on the initial phosphorus concentration of overlying water. Secondly, according to the results of analysis of various forms of phosphorus of sediment, Fe-P and Ca-P are the main sources of endogenous phosphorus released in the interface of sediment-overlying water. Among them, Fe-P is the most unstable form of phosphorus. Ca-P was also easy to transfer under a certain pH value conditions. And other forms of phosphorus contain less, which can be ignored. Moreover, the influence of self-characteristic of sediment on the endogenous phosphorus release, depended mainly on the contents of Fe-P and Ca-P. The self characteristic of sediment should be consider as selecting the wetland sediment.