紫色土泥沙沉积物对磷的吸附-解吸动力学特征

在紫色土集中分布的四川盆地丘陵区,选择不同土地利用方式（林地、水田、旱坡地、村镇）产生的沟渠泥沙为实验材料,采用平衡法研究了紫色土泥沙沉积物对磷的吸附-解吸动力学特征。结果表明,泥沙对磷的吸附和解吸过程按速率均分为快、慢、动态平衡3个阶段,0～0.75h内泥沙对磷的吸附速率与活性铁铝氧化物含量和粘粒含量之间呈显著正相关,较高的OlsenP水平和砂粒含量是泥沙磷解吸速率高的重要因素。泥沙磷的吸附量和解吸量与反应时间之间均呈幂函数关系（Qt=k·ta,0〈a〈1）。磷吸附量与泥沙中活性铁铝氧化物含量呈极显著正相关。磷解吸量与泥沙中砂粒含量显著正相关,与细颗粒物质（粘粒和粉粒）含量呈显著负相关。村镇沟渠泥沙磷的解吸量显著高于其他沟渠泥沙,其释放风险值得重视。本研究结果为川中丘陵区紫色土泥沙磷的释放风险评价提供了科学依据。

Characteristics of Phosphorus Adsorption and Desorption Kinetics of Sediments from Purple Soils

Ditch sediments were respectively collected from forest,paddy field,dry cropland and residential area in a typical agricultural catchment,where locates in hilly area of purple soil in the central Sichuan Basin.The characteristics of phosphorus（P） adsorption-desorption kinetics of the ditch sediments were studied by the batch equilibrium technique.The P was adsorbed and desorbed on the sediments at different rates.According to the rate,the reaction process of adsorbing-desorbing could be divided into three steps,namely fast,slow and dynamic equilibrium reaction.The rate of phosphorus adsorbing on the sediments in the first 0.75 h was significantly and positively correlated with the content of active iron and aluminum oxides and clay fractions.The high rate of phosphorus desorbing on the sediments could be attributed to the high content of Olsen P and sand particle-size fractions.The amounts of P adsorbed and desorbed from the sediments featured a power function with the reaction time（Qt = k·ta,0 a 1）.The P sorption amount of the sediments was highly and positively correlated with the content of active iron and aluminum oxides.The desorption amount of the sediments was significantly and positively correlated with the content of sand particle-size fractions,but it was significantly and negatively correlated with the content of fine particle-size fractions.The P desorption amount of the sediments from the residential area was significantly higher than that of the sediments from the other fields/areas.The results of this research provide a scientific basis for the risk assessment of P release from the sediments derived from purple soils in hilly area of central Sichuan Basin.