科研之友
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摘要
Purpose Particle size poses important influence on the adsorption and enrichment of heavy metals in soil aggregates. In this study, we conducted adsorption experiments to compare the effect of particle size on the adsorption behavior of cadmium (Cd) in aggregates of soils with different properties. Materials and methods Eight types of acid red soils sampled from South China were partitioned into aggregates of different particle sizes (2-0.25, 0.25-0.05, and < 0.05 mm). The adsorption and desorption characteristics of Cd onto the aggregates were examined through batch experiments. The influence of organic matter and free Fe/Al oxides were also examined by selectively removing the corresponding component. Results Both the Langmuir and Freundlich models are suitable for describing the isothermal adsorption characteristics of Cd in these soil particles. The maximum adsorption capacity (q(m)) of the < 0.05 mm fraction aggregates of most of the soils was the highest (1823.38-5365.75 mg/kg), while the desorption rate (Dr) was the lowest (15.37-37.91%) in this fraction. Organic matter content and pH were more important factors influencing the adsorption and desorption of Cd. The adsorption amount of all the soil particles decreased after organic matter was removed, while after the removal free Fe/Al oxides, obvious increase in adsorption amount was only observed in four types of the soils. Conclusions Cadmium tended to enrich in the fine-sized soil aggregates as a whole. The adsorption/desorption behavior of Cd in aggregates not only depend on the content of the soil components but also on their properties and combination condition with each other.
