红壤中矿物表面对腐殖质吸附萘的影响

矿物表面可改变土壤腐殖质对疏水性有机污染物的结合能力。采用红壤和高岭石分别与胡敏酸结合制备得到的两种复合体对萘的吸附等温线非线性显著,其n=0.76或0.74,并且有机碳归一化吸附分配系数的实验值Koacds是采用Kow计算得出的理论值Koc的5倍以上,表明红壤、高岭石均对腐殖质吸附萘有强化作用,且红壤较之高岭石对腐殖质吸附萘的影响稍强些。主要原因是,红壤中除了高岭石外,还有与腐殖质结合力很强的铁氧化物,而且很可能是吸附态腐殖质组成结构形态发生了有利于对萘吸附的改变。

The effects of mineral surfaces in red soils upon the sorption of naphthalene by humics

Mineral surfaces can alter the capacity of soil humic substances for binding hydrophobic organic contaminants.In this paper,two types of organo-mineral complexes of red soil and kaolinite bound respectively with humic acid were prepared.The sorption isotherms of naphthalene by the two complexes were nonlinear significantly,n=0.76 and/or 0.74,and the organic carbon-normalized sorption partitioning coefficient(Kadsoc) values of naphthalene by experimental determination were 5 times higher than the Koc values by theoretical calculation with simple Kow partitioning models.This shows that the sorption affinity of naphthalene to humics can be enhanced by the sorption of humics on the mineral surfaces of red soil and kaolinite.Moreover,the red soil is slightly stronger than kaolinte in affecting the sorption affinity of naphthalene to humics.The main reasons seem to be that,besides kaolinite,red soils contain iron oxide minerals that can strongly bind humics,and the changes might occur in composition and conformation of the humics adsorbed on mineral surfaces,which is in favor of the sorption of naphthalene on these organo-mineral complexes.