洱海河口湿地沉积物对磷的吸附特征及影响因素

为探明洱海入湖河口湿地沉积物对磷的截留效应，采集干、湿季罗时江湿地沉积物，通过吸附动力学、吸附等温线试验并结合吸附模型拟合，分析沉积物对磷吸附快慢和强弱的时空特征，结合沉积物基本理化指标讨论主导吸附机制和影响因素.结果表明:罗时江湿地表层沉积物对磷快吸附阶段的速率常数较慢吸附阶段高1个数量级，最大吸附速率85.1 mg/（kg·h）]在30 min内达到，吸附速率及磷在颗粒物内部的扩散速率均表现为干季高于湿季；低磷起始浓度下测得沉积物吸附-解吸平衡浓度（EPC₀）为（0.037±0.010）mg/L，相比其他湖泊而言处于中等偏低水平；高磷起始浓度沉积物对磷的最大缓冲容量（MBC）呈干季高于湿季、底层高于表层、湿地内部采样点高于入口和出口的趋势；Dubinin-Radushkevich等温吸附模型计算得到吸附能范围为8.65~12.79 kJ/mol，吸附作用性质为离子交换；沉积物矿物元素Fe、Al的相对含量与吸附特征参数呈显著正相关.研究显示，罗时江湿地沉积物矿物元素Fe、Al的相对含量是该区域沉积物磷吸附动力学和热力学时空差异的主导因素. 

Phosphate Adsorption Characteristics and Influencing Factors in Sediments of Erhai Estuarine Wetland

The effective retention of phosphate and other nutrients in wetlands makes it a good technology for ecological management of agricultural non-point source pollution. Compared with the precipitation of suspended particulate matter, absorption by aquatic plants and transformation by aquatic animals and microbes, the contribution of sediment adsorption to phosphate retention by wetland is worthy of attention. In order to evaluate the retention effect of phosphate by the sediments in estuarine wetland, the sediments in the Luoshijiang Wetland in the upstream of Erhai Lake were collected during wet and dry seasons. Adsorption kinetic and adsorption isotherm experiments were conducted combined with the fitting of the adsorption kinetic and isotherm models, and the spatial and temporal characteristics of adsorption rate and capacity of the sediments towards phosphate were further analyzed. In combination with the basic physicochemical indexes of the sediments, the dominant adsorption mechanisms and influencing factors were fully discussed. The results showed that the adsorption rate constant of phosphate on surface sediments in the fast adsorption stage was one order of magnitude higher than that in the slow adsorption stage, and the maximum adsorption rate (85.1 mg/(kg·h)) was reached within 30 min. The adsorption rate and the diffusion rate of phosphate in the particulate matter were both higher in the dry season than that in the wet season. The equilibrium concentration of adsorption-desorption (EPC₀) of the sediments in low initial phosphate concentration was (0.037±0.010) mg/L, which was at a medium low level compared with that of other lakes. The maximum buffer capacity (MBC) of the sediments towards phosphate in the high initial phosphate concentration showed the following trend: higher in the dry season than that in the wet season, higher in the bottom layer than that in the surface layer, and higher inside the wetland than that in the inlet and outlet. The adsorption energy calculated by the Dubinin-Radushkevich adsorption isotherm model ranged from 8.65 kJ/mol to 12.79 kJ/mol, and the dominant adsorption effect was ion exchange. The relative contents of Fe and Al in sediments were positively correlated with the adsorption parameters. The results indicated that the relative content of Fe and Al in the sediments of the Luoshijiang Wetland was the dominant factor affecting the spatial and temporal differences of phosphate adsorption kinetics and thermodynamics. The research results can not only provide data support for accurately evaluating the ability of wetlands to trap phosphate, but also provide a theoretical basis for the protection of the water environment in plateau lakes.