水生植物对生态沟渠底泥磷吸附特性的影响

以用于小流域源头区农业面源污染防控的3条生态沟渠为研究对象,采集入口处(S1)、中间段(S2)和出口处(S3)沟渠底泥,分析其属性和磷吸附特性。结果表明,沟渠底泥全磷含量在0.19~0.60 g·kg~(-1)范围内,且沿水流方向有增大趋势;草酸提取态磷(Pox)及有机质含量与全磷含量呈显著正相关(P0.01,R2=0.920和P0.05,R2=0.549,n=9);而底泥的p H值则随着水流方向有降低的趋势。Langmuir方程拟合吸附数据发现,底泥吸附/解吸平衡磷浓度(EPC0)、磷最大吸附量(Smax)和磷吸附键能参数(Kc)分别为0.08~0.38 mg·L~(-1)、555.6~909.1 mg·kg~(-1)和0.18~0.52 L·mg~(-1)。样点S2(挺水植物梭鱼草和沉水植物绿狐尾藻交接种植区)的Smax最大、EPC0最小,样点S3次之,而样点S1的Smax最小、EPC0最大。这说明水生植物的种植和合理配置,不仅能够影响底泥基本属性的变化,且能增强底泥对磷的吸附作用,有利于降低生态沟渠的磷输出风险。

Effects of aquatic plants on phosphorus adsorption characteristics by sediments in ecological ditches

Ecological ditches play important roles in controlling agricultural pollution of nitrogen and phosphorus. Here three ecological ditches were selected to investigate properties and P adsorption capacities of sediments. The sediment samples were collected at the inlet(S1), mid-section(S2), and outlet(S3) of a ditch. Total P concentrations in the sediments ranged from 0.19 to 0.60 g·kg^-1. Total P increased, but pH values decreased along water flow direction. Oxalate extractable P(Pox) and organic matters(OM) were significantly and positively related with total P(P < 0.01, R²=0.920 and P<0.05, R²=0.549, respectively; n=9). The Langmuir equation showed good fitting of P adsorption. The equilibrium P concentration(EPC₀), sorption maximum(S_max), and adsorption constant(K_c) were 0.08~0.38 mg·L^-1, 555.6~909.1 mg·kg^-1, and 0.18~0.52 L·mg^-1, respectively. The sediments from S2, located at the joint site of two aquatic plants Pontederia cordata and Myriophyllum aquaticum, had the highest S_max and lowest EPC₀, followed by S3. The S1 sediments had the lowest S_max and highest EPC₀. Therefore, planting and rational combination of aquatic plants influence sediment properties, improve P adsorption capacity, and reduce the potential risk of P losses from the ditches.