苇状羊茅根系分泌物对土壤有机氯农药降解的影响

Effects of Root Exudates of Tall Fescue on Degradation of Soil Organochlorine Pesticides

【目的】分析苇状羊茅(Festuca arundinacea)根系分泌物对土壤有机氯农药(organochlorine pesticides,OCPs)残留量、各残留组分的降解特征及根际微生物群落特征的影响效应,探讨根系分泌物在植物修复OCPs过程中的作用。【方法】借助模拟修复实验,对比研究苇状羊茅根系分泌物对土壤中OCPs残留量及其主要组分(GC-ECD、GC/MS-MS)的降解效应、所在土壤中微生物生物量碳(熏蒸提取-容量分析法)及磷脂脂肪酸组分(PLFA)的影响差异。【结果】根系分泌物能促进土壤OCPs去除:添加根系分泌物后,OCPs去除率(77.57%)显著高于对照组(33.49%);相同处理条件(污染水平、添加剂量)下,根系分泌物对HCHs、毒杀芬、HCB、艾氏剂、γ-氯丹的强化去除率总高于对OCPs总量的强化去除率(p<0.05);对DDTs、灭蚁灵、硫丹Ⅰ、狄氏剂、环氧七氯的强化去除率则普遍低于对OCPs总量的强化去除率。相同污染水平下,添加根系分泌物土壤中的微生物生物量碳也显著高于对照组;实验期间,细菌的磷脂脂肪酸含量占主导地位、真菌次之,其变化趋势与土壤中OCPs残留的降解特征相一致。【结论】OCPs降解过程中,根系分泌物的存在改变了根际土壤中细菌、真菌的种群数量及其群落结构,进而改善了对OCPs的降解效率。

[Objective] The objective of this study was to clarify the effects of root exudates on degradation of organochlorine pesticides （OCPs）in soils and to evaluate microbial ecological characteristics in OCPs- contaminated soils. [Method] Pot experiments were carried out to investigate the effects of root exudates of tall rescue （Festuca arundinacea）on degradation of total amount of OCPs and its main components in soils by methods of GC-ECD and GC/MS-MS. To determine influence of root exudates on the rhizosphere microbial growth and their community structure, soil microbial biomass carbon（SMBC） and their phos- pholipid fatty acids（PLFA） in soils were also analyzed by TOC-500 analyzer and GC-MS, respectively. [Result] The root exudates of tall rescue significantly enhanced the removal of OCPs. The removal rate was significantly higher in the treatment （77.57%）than in the control （33.49%）. Under the same treatment conditions, the enhanced removal rates of hexachlorocyclohexane （HCHs）,toxaphene, hexachlorobenzene （HCB）, aldrin and γ-chlordane were much higher than one of the total amount of OCPs while theextent of enhanced dissipation of dichloro-diphenyl-trichloroethanes （DDTs）, mirex, endosulfan I , dieldrin and heptachlor epoxide were always lower than that in corresponding soils. Soil microbial biomass carbon increased with increasing pyrene concentration and there were close relationship between OCPs degradation and soil microbes during the whole experiment.Microbial community was dominated by bacteria, followed by fungi. They had the similar variation trend along with OCPs degradation, indicating that the 0CPs in soils were degraded mainly by bacteria and fungi. Therefore, root exudates may influence the OCPs degradation through altering bacterial and fungi population. [Conclusion] Root exudates of tall rescue might change soil microbial community and structure during the process of phytoremediation, and further modify the degradation of OCPs.