玉米和大豆根尖和非根尖部位对Mn(II)的吸附研究

为了探索玉米和大豆根系根尖部位和非根尖部位对Mn(II)吸附的差异及其机制,用砂培试验获取两种植物的新鲜根,将根系分为根尖部位和非根尖部位2部分,用流动电位法和红外光谱法(ATR-FTIR)分别表征了它们根表的zeta电位和官能团;将根系与Mn(II)反应,然后用KNO₃、EDTA-2Na和HCl连续提取的方法确定吸附在植物根表Mn(II)的结合形态和吸附量。研究结果表明:吸附在植物根表的Mn(II)主要以交换态存在,根尖部位的交换态Mn(II)和吸附Mn(II)的总量要明显大于非根尖部位。根尖部位所带负电荷和官能团的数量多于非根尖部位,是前者对Mn(II)具有更高吸附容量的主要原因。因此,植物根系的表面电荷特征和官能团数量在根系及根尖部位吸附Mn的过程中起着重要的作用。

Study on Sorption of Mn(II) on Root Tips and Non Root Tips of Maize and Soybean

To examine the differences in surface charge and functional groups of apical and non-apical parts of plant roots and their effects on Mn(II) sorption onto plant roots, fresh roots of maize and soybean were obtained by sand culture experiment, and the roots were divided into two parts: apical part and non-apical part. Zeta potential and functional groups of the roots were determined by streaming potential and ATR-FTIR, respectively. The roots were reacted with Mn(II) solution, and then exchangeable, complexed, and precipitated forms of Mn(II) sorbed on plant roots were extracted with KNO3, EDTA-2Na and HCl sequentially. The results showed that the zeta potential of apical parts of the two plants were more negative than those of the non-apical parts, and the apical parts of two plants carry more functional groups than the non-apical parts. Mn(II) sorbed on the root surfaces of two crops mainly existed as exchangeable form, and the amounts of exchangeable Mn(II) and total sorbed Mn(II) on the apical parts were signi?cantly greater than these on the non-apical parts. The higher negative charge and the larger number of functional groups on the apical part were responsible for their higher adsorption capacity and greater binding strength for Mn(II) than the non-apical part. Therefore, surface charges and functional groups play an important role in the sorption of manganese on the roots.