养殖池塘底泥-水界面营养盐扩散的室内模拟研究:Ⅰ氮的扩散

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

通过室内模拟试验,对养殖池塘底泥-水界面N营养盐的扩散特点进行了研究。结果表明,池塘淤泥中TN的累积是伴随着池塘有机质的沉积,养殖池塘底泥N的释放形态主要是NH+4-N,DO对N的释放速率的影响具有多重性。DO(溶解氧)影响了有机质的分解速率,从而影响着营养盐的再生速率,DO又影响着微生物对营养盐的消耗水平。养殖池塘N的释放受到泥水两相营养盐平衡机制的制约,只有当水中浓度低于平衡浓度时,才表现为净释放,否则可能出现负释放,平衡浓度受到DO和Eh(氧化还原电位)的影响。

Sediments from a new farming ponds （A） and an old one （B） were sampled and used to carry out indoor experiments for researching on nitrogenous compounds diffusion at the water-sediment interface of farming ponds. The nitrogen releasing curve and daily releasing amount were recorded during the experiments period （8 d）. Based on the experimental results, nitrogen releasing forms, releasing rates, balanced concentrations and releasing lasting time were determined and compared between the two samples. The results were as followings： TN in the sediments was linearly related to OM（r=0.92, P〈0.01）, indicating that the accumulation of TN in the pond sediment was accompanied with the sedimentation of organic matter. NH4^＋-N was the only form of N releasing in B, while NH4^＋-N was the main form of N releasing in the prophase of A and NO2^- -N became the main form of N releases in the late period. This difference indicated the oxygen debt of old pond sediments was higher than that of new pond sediments. The maximum nitrogen releasing rate of A reached 200 mg. m^-2. d^-1, the absorbing rate of NO3^--N was 60 mg.m^-2.d^-1; while the maximum releasing rate was 254.8 mg·m^-2d^-1 in B, higher than that of A, with the maximum releasing time 2 d earlier than A. The balanced concentration of B was 3 mg·L^-1, also higher than that of A （2 mg. L^-1）, but the releasing lasting time of B was evidently shorter than that of A. DO and Eh were the two factors resulting in the differences, DO exerted multiply effects on releasing rates of N： firstly, it affected the decomposing rate of organic matter and then the rebirth rates of nutrients; secondly it affected the nutrients consuming rates by microorganisms. Nutrients releasing were controlled by the equilibrium mechanisms between the water and sediment, and the concentrations in equilibrium states were influenced by DO and Eh. Net releases took place only at the concentrations of nutrients below those in equilibrium states; otherwise, negative releases took place.