不同沉水植物根际微域中菲和芘的降解行为
Degradation of Phenanthrene and Pyrene in the Rhizosphere of Different Submerged Plants

沉水植物在水生态系统的生态功能方面有重要作用, 并对沉积物中多环芳烃(PAHs)的降解有促进作用, 然而其降解的根际效应尚不清楚．本文选取了两种典型的沉水植物(苦草和狐尾藻), 利用自制的多隔层根箱研究了根际微域中菲和芘的降解行为．结果表明：距离根系4 mm微域内, 植物根际促进了菲和芘的降解, 存在根际效应, 且苦草根际微域中菲和芘的去除率增幅(17.9% ～29.9% 和8.8% ～27.4% )大于狐尾藻(13.8% ～26.2% 和10.8% ～22.5% ), 说明苦草的根际效应大于狐尾藻; 同时, 0～6 mm微域内, 苦草根际PAH-降解菌数量高于狐尾藻, 且降解菌数量与菲和芘的去除率均显著正相关; 此外, 苦草和狐尾藻根系对沉积物中氧化还原电位的影响范围分别为6 mm和4 mm, 且氧化还原电位与降解菌数量之间显著正相关, 表明根系释氧提高PAH-降解菌数量, 进而促进了菲和芘的降解．
Submerged plants play an important functional role in ecosystem and are capable of improving the degradation of polycyclic aromatic hydrocarbons(PAHs)in sediments. However，their rhizosphere effects on PAH degradation are still unclear. In this study，degradation of phenanthrene and pyrene in the rhizosphere of two typical submerged plants，Vallisneria spiralis and Myriophyllum spicatum，was studied using a self-designed laminar rhizobox. The results showed that both V. spiralis and M. spicatum enhanced the degradation of phenanthrene and pyrene within the distance of 4 mm from root surface，and the dissipation increments of phenanthrene and pyrene in the rhizosphere of V. spiralis(17.9% ―29.9% and 8.8% ―27.4% )were more than those of M. spicatum(13.8% ―26.2% and 10.8% ―22.5% )，indicating that the rhizosphere effect of V. spiralis on PAH degradation was greater than that of M. spicatum. Within the distance of 6 mm from root surface，PAH-degrading bacterial populations in the rhizosphere of V. spiralis were also larger than those of M. spicatum. Positive correlations were found between PAH-degrading bacterial populations and dissipation ratios of phenanthrene and pyrene. Besides，sediment redox potentials affected by V. spiralis and M. spicatum were within the distance of 6 mm and 4 mm，respectively，which had a significant positive correlation with PAH-degrading bacterial population，indicating that root oxygenation of submerged plants could enhance PAH-degrading bacterial population and then improve the degradation of phenanthrene and pyrene in sediments