名山河流域黄壤组分对微团聚体吸附解吸镉的影响

选取名山河流域4种土地利用方式（林地、水田、茶园、旱地）的黄壤为研究对象,采用平衡液等温吸附法和NH4OAC、EDTA溶液解吸法,研究土壤组分（有机质、游离氧化铁）对微团聚体吸附解吸Cd2＋的影响。结果表明：去除土壤组分前后,原土及各粒径微团聚体对Cd2＋的吸附量均随Cd2＋初始浓度增大而增大,吸附量均按以下次序递减：（〈0.002mm）〉2～0.25mm〉原土〉0.053～0.002mm〉0.25～0.053mm,与有机质、游离氧化铁、CEC呈极显著正相关。吸附减少量大小关系为：去除有机质〉去除游离氧化铁,有机质的贡献率大于游离氧化铁。Freundlich方程拟合效果最佳,达到极显著水平,分布系数Kd值与Cd2＋初始浓度呈曲线负相关。NH4OAC解吸率随原吸附Cd2＋初始浓度增大而增大,以最大解吸率计,递减规律为：0.25～0.053mm〉0.053～0.002mm〉原土〉2～0.25mm〉（〈0.002mm）;EDTA解吸率随原吸附Cd2＋初始浓度增大而减小,递减规律与NH4OAC解吸率相反。去除土壤组分后,NH4OAC解吸率上升,EDTA解吸率下降,茶园与旱地黄壤非解吸率减小,林地与水田黄壤非解吸率增大。去除土壤组分后,非专性吸附与吸附总量呈极显著正相关,专性吸附与吸附总量呈极显著负相关。

Effect of Yellow Soil Components on Adsorption and Desorption of Cadmium by Microaggregates in Mingshan Watershed,Sichuan Province,China

The four kinds of old alluvial yellow soil,including woodland,paddy fields,tea garden and dry land,collected from the Mingshan River,was used to investigate the effect of yellow soil components on adsorption and desorption of Cd2＋ by microaggregates with isothermal adsorption method of equilibrium liquid and desorption method of NH4OAC and EDTA.The results showed that：the distribution of soil organic matter,free iron oxide and cation exchange capacity was basically the same in bulk soil and particle size of microaggregates,being the highest of yellow soil of Woodlang.The adsorbance of Cd2＋ increased with the initial concentration of Cd2＋ before and after removing soil components.The adsorbance was diminishing as the following sequence：（0.002 mm）2～0.25 mm bulk soil0.053～0.002 mm0.25～0.053 mm,being significantly positively correlated with OM,free iron oxides and CEC.The size relationship of adsorption reduction was the following sequence：removal of OMremoval of free iron oxide.The contribution of OM was much more than free iron oxide.The adsorption of Cd2＋ in four patterns of yellow soil was exchange adsorption mainly to complexing adsorption supplemented.Freundlich equation best fitting effect adsorption isotherm reached a significant level.Before and after removing soil components adsorbance and initial concentration of Cd2＋ had showed a nonlinear correlation.The equilibrium constant K was significantly positively correlated with soil organic matter,free iron oxide and cation exchange capacity.After removing soil components,K had decreased which adsorption capacity becamed smaller.The Kd was negatively correlated with initial concentration of Cd2＋.NH4OAC desorption rate increased with initial concentration of Cd2＋.According to the maximum of NH4OAC desorption rate,the size relationship was the following sequence：0.25～0.053 mm0.053～0.002 mmbulk soil2～0.25mm （0.002 mm）,but EDTA desorption rate decreased with the increase of cadmium＇s initial concentration,whose decreasing regularity was contrary to NH4OAC desorption rate.After removing soil components NH4OAC desorption rate increased significantly,while EDTA desorption rate reduced.The desorption rate of tea garden and dry land decreased,which of woodland and paddy fields increased.After removing soil components,non-exclusive adsorption was significantly positively related to total adsorbance,while specific adsorption was significant negative correlated with total adsorption.