大豆和小麦根系对菲的吸持作用及其生物有效性

不同作物根系对多环芳烃(PAHs)的吸持作用及其生物有效性研究有助于深入揭示PAHs在生态系统中的环境行为和科学评估PAHs的生态风险.然而,不同作物根系吸持PAHs的差异性及其生物有效性鲜有报道.为此,本研究以菲作为PAHs的代表,探究了不同条件下大豆和小麦根系对菲的吸持/解吸及其吸持菲的有效性.结果表明,根系菲吸持随时间的变化表现为:活体根处理先增加再降低而后趋于平衡,这与活体根系存在菲转运延迟有关;灭活根和烘干根处理则先增加而后趋于平衡.根系的比表面积越大,脂肪含量越高,菲的吸持速率越快.不同菲浓度条件下,各处理根系菲的吸持量均随平衡浓度的增加而增大,Henry吸附等温式拟合R2均大于0.973,灭活根和烘干根用Freundlich吸附等温式拟合效果更好,小麦根系的Langmuir吸附等温式拟合效果优于大豆根系,说明分配作用和表面吸附共同控制作物根系菲的吸持,而活体根系与菲存在特殊的键合作用,其拟合效果较差.脂肪含量越高、含水率越高、膜的通透性越大,根系的吸持容量也越大.吸持在根系上的菲的解吸率的大小顺序为活体根烘干根灭活根;大豆各处理根系小于相应的小麦根系.不同根系吸持菲的生物有效性与解吸结果一致,因此可以用解吸率评价其生物有效性.研究结果可为作物根系吸持PAHs的当季和后茬作物有效性评估提供依据.

Sorption of Phenanthrene to Soybean and Wheat Roots and the Bioavailability of Sorbed Phenanthrene

The study of PAHs sorption and bioavailability to different crop roots could help to reveal the environmental behavior of PAHs in the ecosystem and evaluate the ecological risk of PAHs. However, there is little information about the differences in PAHs sorption to different roots and the bioavailability of the sorbed PAHs. In this paper, the experiments were conducted on the sorption/desorption of phenanthrene to soybean and wheat roots under different sorption times and different phenanthrene concentrations. The results showed that the trend of phenanthrene sorption in vivo was first increased and then decreased and finally reached a balance, which was related to the transport delay in vivo; the trend in dead and dried roots was first increased and then reached a balance. The greater specific surface area and the higher fat content, the faster the balance was. Freundlich isotherm was fitted better than Henry isotherm for dead and dried roots, Langmuir isotherm was best fitted in wheat roots. All of the fitted isotherms indicated that the distribution and the surface adsorption could control the phenanthrene sorption. Because of the special binding between living roots and phenanthrene, the fit effect was poor. The phenanthrene sorption capacity of soybean roots was higher than that of wheat, which was related to the high water content, fat content and membrane permeability. The phenanthrene sorbed on the roots was hard to desorb, and the desorption trends were wheat roots> soybean roots; living roots> dried roots> dead roots. The bioavailability of root-sorbed phenanthrene was consistent with the desorption results. Our results could provide data for the assessment of environmental risks of PAHs sorbed onto crop roots.