养殖池塘底泥-水界面营养盐扩散的室内模拟研究:Ⅱ磷的扩散

Nutrients Diffusion at the Water-Sediment Interface of Farming Ponds by Indoor Simulation Experiment:ⅡDiffusion of Phosphorous Compounds

通过室内模拟试验,对养殖池塘底泥-水界面P营养盐的扩散特点进行了研究。结果表明,养殖池塘底泥P的释放形态主要是PO43-,P的释放与N的释放呈现一定的相关性,P的释放与底泥有机质分解相关,DO(溶解氧)对P的释放速率的影响具有多重性。DO影响了有机质的分解速率,从而影响着P营养盐的再生速率,DO又影响着无机磷酸盐的溶解性。养殖池塘P的释放受到泥水两相营养盐平衡机制的制约,平衡浓度受到DO和氧化还原电位Eh的影响。表层底泥中TP含量与水中PO34-呈现正相关,但TIN(总无机氮)含量与TN(总氮)相关性不强,这可能与养殖池塘中两者来源不同有关,养殖池塘的TIN主要来源于鱼类的代谢活动,而PO34-由于沉降作用大,其大部分可能来源于底泥的P释放。

Sediments from a new farming pond （A） and an old one （B） were sampled and used to carry out indoor experiments for researching on phosphorous compounds diffusion at the water-sediment interface of fanning ponds. The phosphorus releasing curve and daily releasing amount were recorded during the experiments period （8 d）. Based on the experimental results, phosphorus releasing forms, releasing rates, 3- balanced concentrations and releasing lasting time were measured and compared between the two samples. The results showed that PO4^3＋ was the main form of P releasing in both A and B. The maximum phosphorus releasing rate and the balanced concentration of A were 25 mg·m^-2. d^-1and 0.15-0.20 mg· L^-1 respectively, while those of B were higher, being 28.7 mg. m^-2. d^-1 and 0.3 mg· L^-1 respectively. The time when phosphorus releasing reached equilibrium of B was 2 d earlier than that of A, and phosphorus releasing lasting time of B was shorter than that of A. P releasing was affected by the concentration of NO3^--N in water, the higher the NO3^--N, the lower the balanced concentration, Phosphorus releasing was strongly related to nitrogen releasing, indicating phosphorus releasing also partly controlled by the decomposition of organic matter in the sediment as nitrogen releasing. The differences between A and B were due to the differences of DO and Eh in two samples. DO had multiply effects on releasing rates of P： firstly, it affected the decomposing rate of organic matter and thus affected the rebirth rates of nutrients; secondly, it affected the resolvability of phosphates. The higher the Eh, the lower the balanced concentration. Phosphate in pond water positively related to TP in surface layer of sediment, while TIN in pond showed no evident relation to TN in sediment, which probably resulted from the different sources of TIN and phosphate in fanning ponds： TIN mainly produced by fish excretion, while phosphate generated by sediment releasing due to the strong clay sedimentation functions of cleaning most dissolved phosphate in the pond water.