红叶石楠叶面角质层组分对Cs的吸附作用

摘要

为准确预测放射性核素在植物叶面的吸附行为,用化学方法(脱蜡,皂化,酸解)分离得到角质层(PHC1),脱蜡角质层(PHC2),脱蜡-脱角质角质层(PHC3),脱蜡-脱角质-脱糖角质层(PHC4)以及蜡质等红叶石楠叶面角质层组分,研究了角质层组分对Cs的吸附特征及影响因素.结果表明:红叶石楠叶片角质层由16.63％蜡质,63.41％角质,12.86％多糖,7.10％角碳组成.PHC1、PHC2、PHC3、PHC4各组分对Cs的吸附30min即达到吸附平衡,饱和吸附量分别为1.73、1.92、4.67和0.58mg/g.角质层组分的饱和吸附量与其极性和芳香性指数具有显著的二元线性正相关性,其中极性指数对核素吸附具有更高权重的影响.糖类和角质是叶面角质层吸附核素的主要介质,各角质层组分吸附Cs贡献率分别为:糖类(51.45％)>角质(38.73％)蜡质(7.51％)>角碳(2.31％).竞争离子的存在能显著降低叶面对核素的吸附作用:随着Na离子浓度的增加,叶面角质层对Cs的吸附性能逐渐下降,当Na和Cs摩尔浓度比为100:1时,红叶石楠叶面角质层的吸附量仅为对照的6％.%For accurately predicting foliar uptake of the radionuclide, leaf cuticular fractions of Photinia serrulatawere isolated by chemical methods including Soxhlet extraction, saponification, and acid hydrolysis, yielding bulk foliar cuticle (PHC1), the dewaxed cuticular fraction (PHC2), the nonsaponifiable fraction (PHC3), and cutan (PHC4). Adsorption behavior of cesium (Cs) onto leaf cuticular fractions of Photinia serrulata (PHC1, PHC2, PHC3, PHC4) was investigated and the relative sorption contribution of the cuticular component was accessed. The leaf cuticle sheet of Photinia serrulata consisted of waxes (16.63％), cutin (63.41％), polysaccharide (24.0％) and cutan (7.10％). The apparent adsorption equilibrium was reached within 30min, and the maximum adsorption capacity were 1.73 (PHC1), 1.92 (PHC2), 4.67 (PHC3), 0.58 (PHC4) mg/g, respectively. The theoretical maximum adsorption capacity of cuticular fractions was binary positive linearly correlated with their polarity and aromaticity index, and the polarity played a more noteworthy role in nuclide accumulation. Sugars and cutin acted as the main adsorption medium of Cs on leaf cuticle layer while epicuticular waxes and cutan show minor contribution on nuclide accumulation. The relative adsorption contribution of cuticular fraction was followed as sugar (51.45％) > cutin (38.73％) waxes (7.51％) > cutan (2.31％). The adsorption capacity of Cs on leaf cuticle of Photinia serrulata distinctively declined with the presence of sodium ion which was negatively correlated with the concentration of sodium. When the concentration of sodium was 100times higher than that of Cs, adsorption amount of bulk cuticle reduced to 6％ in comparison with the control (adsorption of Cs without sodium), indicating that the coexistence of ion can considerably reduce the adsorption of nuclide on leaf cuticle.