Chen Bao-liang, Zhou Dan-dan, Li Yun-gui, Zhu Li-zhong
Department of Environmental Science, Zhejiang University, Hangzhou 310028, China.
Huan Jing Ke Xue. 2008 Jun;29(6):1671-5.
Wax components are ubiquitous in natural environments (such as plant and soil) and play a significant role in sorption of organic contaminants. To elucidate their sorption characteristics, cuticular waxes were isolated from the fruits of apple by organic solvent extraction method, and then the isolated-wax was reconstructed on montmorillonite with different loadings. Sorption behaviors of one polar organic pollutant, 1-naphthol, to isolated-wax, reconstructed-wax, and cuticle-associated-wax samples were compared by batch sorption method. Sorption properties of wax-montmorillonite complexes dependent on different wax-loadings were also investigated. Isotherms of 1-naphthol to wax samples were nonlinear, and fitted well with Freundlich equation. Although sorption of wax in the plant cuticle was weakened by other components of cuticle, its contribution to whole sorption of the cuticle increased with solute aqueous equilibrium concentration. Sorption coefficients at three equilibrium concentrations (1, 10, 100 microg/mL) were calculated, depending on solute concentrations and wax-loadings. Sorption coefficients normalized organic carbon contents (Koc) decreased with the increase of solute aqueous concentration. At low solute aqueous concentration, Koc values increased with the wax-loading increasing, reached maximum, and then decreased. At high solute aqueous concentration, Koc values were almost independent on wax-loadings. These observations indicated that partition was the dominant mechanism at high solute concentration, while specific interactions were involved as additional mechanisms at low solute concentration. Koc values of wax components in different states were in the order of reconstructed-wax (321.2) > isolated-wax (190.4) > cuticular-attached-wax (128.4), suggested that the sorption capability of wax was promoted once they were input into soil environment and then coated on mineral surface.
蜡质成分在自然环境（如植物和土壤）中普遍存在，并且在有机污染物的吸附过程中发挥着重要作用。为了阐明它们的吸附特性，采用有机溶剂萃取法从苹果果实中分离出表皮蜡质，然后将分离出的蜡质以不同负载量重构于蒙脱石上。通过批量吸附法比较了一种极性有机污染物1-萘酚对分离蜡质、重构蜡质和与角质层相关蜡质样品的吸附行为。还研究了蜡质-蒙脱石复合物的吸附特性与不同蜡质负载量的关系。1-萘酚对蜡质样品的等温线呈非线性，与Freundlich方程拟合良好。尽管植物角质层中蜡质的吸附会被角质层的其他成分削弱，但其对整个角质层吸附的贡献会随着溶质水相平衡浓度的增加而增加。根据溶质浓度和蜡质负载量，计算了三个平衡浓度（1、10、100μg/mL）下的吸附系数。归一化有机碳含量的吸附系数（Koc）随着溶质水相浓度的增加而降低。在低溶质水相浓度下，Koc值随着蜡质负载量的增加而增加，达到最大值后又降低。在高溶质水相浓度下，Koc值几乎与蜡质负载量无关。这些观察结果表明，在高溶质浓度下分配是主要机制，而在低溶质浓度下特定相互作用作为附加机制参与其中。不同状态下蜡质成分的Koc值顺序为：重构蜡质（321.2）>分离蜡质（190.4）>与角质层结合的蜡质（128.4），这表明蜡质一旦进入土壤环境并包覆在矿物表面，其吸附能力就会得到提升。
