两种亚热带土壤中铁锰的淋溶淀积及其对Pb和Cd的吸附特征

Leaching and Deposition of Fe and Mn in Two Subtropical Soils and Their Adsorption Characteristics of Pb and Cd

以亚热带的棕红壤和黄棕壤为装柱材料,用铁锰混合溶液(0～0.04mol·L-1)淋溶土柱,研究铁锰在土壤中的淀积特征,并用等温吸附法研究其对Pb2+、Cd2+的吸附规律。结果表明:土柱淋溶后,各处理中棕红壤淀积的锰含量比黄棕壤的低0.24～1.17mg·g-1,各处理土壤表面淀积的游离铁和非晶质铁的含量均显著高于锰氧化物。经铁锰溶液淋溶而形成的土壤样品对Pb2+、Cd2+的最大吸附量比未淋溶的土壤高,最大增加量可达33.07mmol·kg-1,可见铁锰淀积能显著提高土壤对Pb2+、Cd2+的吸附能力。土柱上层(装柱5cm处)土壤样品对Pb2+、Cd2+的最大吸附量大于土柱下层(装柱25cm处)样品,最大差值可达到16.22mmol·kg-1。两种土壤对Pb2+的吸附量是对Cd2+的8～15倍。

The characteristics of the deposition of iron and manganese in the brown red soil and yellow brown soil of subtropical area were studied using soil columns leached by the mixed solution of iron and manganese（0～0.04 mol·L-1）,and their isothermal adsorptions to Pb2＋ and Cd2＋ by the leached soils were studied by batch experiments.The results were as follows：after soils were leached in the columns,manganese deposited 0.24～1.17 mg·g-1 less in brown red soils than those in yellow brown soils,and the contents of free iron and amorphous iron were significantly higher than those of manganese oxides in the samples.The maximum adsorption capacities to Pb2＋ and Cd2＋ of leached soil samples were higher than those of the soils not leached,and the increased maximum was up to 33.07 mmol·kg-1.Soil samples at the upper part of the column（column packing at 5 cm）had a larger adsorption capacity compared with the lower（column packing at 25 cm）samples,and the maximum of adsorption difference reached to 16.22 mmol·kg-1.The adsorption amounts to Pb2＋ of two leached soils were 8～15 times higher than those of Cd2＋.