Zhang Yingjie, Zhu Dongqiang, Yu Hongxia
State Key Laboratory of Pollution Control and Resource Reuse, and School of the Environment, Nanjing University, Jiangsu, P.R. China.
J Environ Qual. 2008 May 2;37(3):817-23. doi: 10.2134/jeq2007.0217. Print 2008 May-Jun.
Clay minerals and humic substance (HS)-clay complexes are widely distributed in soil environments. Improved predictions on the uptake of organic pollutants by soil require a better understanding of fundamental mechanisms that control the relative contribution from organic and inorganic constituents. Five selected aromatic compounds varying in electronic structure, including nonpolar phenanthrene (PHEN), 1,2,4,5-tetrachlorobenzene (TeCB), polar 1,3-dinitrobenzene (DNB), 2,6-dichlorobenzonitrile (dichlobenil [DNL]), and 1-naphthalenyl methylcarbamate (carbaryl [CBL]), were sorbed separately from aqueous solution to Na(+)-, K(+)-, Cs(+)-, and Ca(2+)-saturated montmorillonites with and without the presence of dissolved HS at pH about 6. Upon normalizing for hydrophobic effects by solute aqueous solubility, the overall trend of sorptive affinity to HS-free K(+)-clay is DNB >> DNL, CBL > PHEN, TeCB, indicating preferential adsorption of the polar solutes. With the presence of HS, sorption of PHEN, TeCB, and CBL increases by several times compared with the pure clay, attributed to HS-facilitated hydrophobic partition (PHEN and TeCB) or H-bonding (CBL). The enhanced sorption of PHEN by HS is cation dependent, where Cs(+) shows the strongest facilitative effect. Coadsorption of HS does not affect sorption of DNB and DNL to clays except that of DNB to Ca(2+)-clay because cation-dipole interactions between the polar group (NO(2) or CN) of solute and weakly hydrated exchangeable cations dominate the overall sorption.
黏土矿物以及腐殖质（HS）-黏土复合体广泛分布于土壤环境中。要改进对土壤中有机污染物吸收情况的预测，就需要更好地理解控制有机和无机成分相对贡献的基本机制。选取了五种电子结构各异的芳香族化合物，包括非极性的菲（PHEN）、1,2,4,5-四氯苯（TeCB）、极性的1,3-二硝基苯（DNB）、2,6-二氯苯腈（敌草腈[DNL]）以及1-萘基甲基氨基甲酸酯（西维因[CBL]），在pH约为6的条件下，分别将它们从水溶液中吸附到有和没有溶解态HS存在的Na(+) -、K(+) -、Cs(+) -和Ca(2+) -饱和蒙脱石上。通过溶质在水中的溶解度对疏水作用进行归一化处理后，对不含HS的K(+) -黏土的吸附亲和力总体趋势为DNB >> DNL，CBL > PHEN，TeCB，这表明极性溶质具有优先吸附性。在有HS存在的情况下，与纯黏土相比，PHEN、TeCB和CBL的吸附增加了几倍，这归因于HS促进的疏水分配（PHEN和TeCB）或氢键作用（CBL）。HS对PHEN吸附的增强作用取决于阳离子，其中Cs(+)表现出最强的促进作用。HS的共吸附除了对DNB在Ca(2+) -黏土上的吸附有影响外，不影响DNB和DNL在黏土上的吸附，因为溶质的极性基团（NO(2)或CN）与弱水化的可交换阳离子之间的阳离子-偶极相互作用主导了总体吸附。
