【作者】 马兆辉；

【导师】 徐建明；

【作者基本信息】 浙江大学 ， 土壤学， 2006， 硕士

【摘要】 有机污染物是重要的土壤污染物之一,研究有机污染物在土壤中的环境行为及其作用机理,是土壤有机污染物根际修复的理论基础,将为土壤有机污染物的防治和修复提供理论和技术依据。 本文研究了五氯酚（PCP）在毫米级根际土壤中的消减规律,并探讨了PCP胁迫下对根际土壤中微生物群落结构及酶活性的影响。获得如下研究成果: （1） 采用三室根箱法,对根际土进行了根室、1mm、2mm、3mm、4mm、5mm近根际以及>5mm远根际的毫米级微域划分。研究发现,20mg PCP·kg^-1污染土壤中距离根际2mm处PCP的残留量最低,残留量顺序为远根际区（>5mm）>根箱中室>5mm>1mm>4mm>3mm>2mm;在污染浓度为50mg PCP·kg^-1的根箱中,PCP的最优消减出现在3mm根际微域,残留量顺序为远根际区（>5mm）>根箱中室>1mm>5mm>2mm>4mm>3mm。这有别于传统植物营养学中发现的营养因子根际梯度递减效应,表现出根际微域污染物消减的特异性。原因可能在于:高低两个胁迫浓度下,2mm和3mm的近根际微域中,根系分泌物的适宜剂量创造了诱导PCP消减的最佳土壤环境,在这种土壤环境中,微生物活性得到最大程度的激发,而根系分泌物本身对PCP的竞争效应降至最低。 （2） PCP的胁迫对根际土壤中酶活性有一定影响。种植黑麦草的处理与对照相比,土壤磷酸酶和脲酶活性在根系分泌物的作用下得到不同程度地激发,其值明显高于对照各土层中磷酸酶和脲酶活性。尽管磷酸酶与脲酶在各土层中的变化趋势与PCP的消减根际效应存在一定程度的差异,但是总体变化趋势基本一致。 （3） 借助新兴的磷脂脂肪酸（phospholipid fatty acid,PLFA）谱图分析技术,深入地研究了PCP胁迫下根际微域中由于根系分泌物诱导引起的土壤微生物群落结构的变化特征,发现根际环境中土壤微生物群落结构在距根表不同距离的毫米级根际微域中表现出不同的演替规律。革兰氏阴性菌是高低两个浓度下PCP降解效率最高的2mm和3mm近根际微域中的优势菌种。更多还原

【Abstract】 Pentachlorophenol (PCP, C6Cl5OH) is a kind of ionizable hydrophobic organic contaminants (HIOCs). The highest concentrations of PCP are usually found in soil and aquatic sediments. The investigation on the environmental behaviors of PCP in soil and the key controlling factors involved will be effective and helpful to achieve the phytoremediation of PCP-contaminated soils.This thesis aimed to evaluate the biodegradation of PCP in millimeter rhizosphere and the corresponding microbiological and biochemical response, and develop the alternative phytoremediation technique for PCP contamination. The results for this research can be summarized as follows:1. A glasshouse experiment was conducted to investigate the rhizosphere effects on the biodegradation of PCP and on the dynamic response of soil microbial community structure, using a specially designed rhizosbox where ryegrass seedlings were grown in soil spiked with PCP at concentrations of 20mg PCP-kg~-1 and 50mg PCP-kg~-1 soil. Changes of PCP concentrations with increasing distance from the root compartment of the rhizosbox were then determined. The most dissipation of PCP in planted soil was at the 2mm and 3mm from the root zone where total PCP decreased to 0.69 mg PCP·kg~-1 and 1.69 mg PCP ·kg~-1, respectively with the spiked concentration of 20 mg PCP·kg~-1 and 50 mg PCP·kg~-1. Meanwhile, good negative correlations with the total PLFAs were found in both low and high PCP spiked treatments (p<0.05). The degradation gradient followed the order: near-rhizosphere > root compartment > far-rhizosphere soil zones for both concentrations where ryegrass {Lolium perenne L.) were grown. In contrast, there were no differences in both PCP-contaminated soils with distance in the unplanted soils.2. The phosphatase activities and urease activities increases in both soils companied by the enhanced dissipation of PCP, which were higher in the near-rhizosphere than that in the far-rhizosphere soils. The results suggest that the effect of root exudate is essential in the dissipation of xenobiotics such as PCP in soil.3. Phospholipid fatty acid (PLFA) profiles, consisted of quantitativedetermination of each PLFA component and the shift in PLFA patterns, can provide comprehensive information for detecting the microbial community. Several fatty acids are known to be "signatures" of subsets of microbial community. Therefore, the specific PLFA profiles can be used to characterize different groups of bacteria. Furthermore, a phospholipid pattern change in the related samples could be indications of a shift in microbial community. In this research, an investigation was conducted using the PLFA profiles to follow shifts in microbial community structure and to illustrate the mechanism of the PCP dissipation in the rhizosphere of ryegrass. We found that the gram-negtive bacteria were relatively gathering in the 2mm and 3mm near rhizosphere, respectively in both 20 mg PCPkg"1 and 50 mg PCP-kg"1 spiked concentration, where presented the highest dissipation and lowest residues. Thus some conclusions were made that the gram-negtive bacteria may be the mainly microbial factors involved in the accelerated process of PCP dissipation in the rhizosphere.更多还原