【作者】 洪有为；

【导师】 袁东星；

【作者基本信息】 厦门大学 ， 环境科学， 2009， 博士

【摘要】 红树林生态系统是热带、亚热带海岸重要的湿地生态系统。河口海岸带生态破坏性开发活动的日益频繁和大量的工农业废水和生活污水的长期直排入近岸海域使红树林湿地遭受极大的破坏。红树林湿地生态系统因生产力高、富含有机质以及强还原性环境条件等特性，使之成为吸收和积累多环芳烃（PolycyclicAromatic Hydrocarbons，PAHs）的重要场所。因此，深入开展红树林湿地中PAHs污染物的环境行为及其对红树林生境的生态效应的研究，具有重要意义。菲（Phenanthrene，PHE）和荧蒽（Fluoranthene，FLA）分别是16种优控PAHs中3环和4环芳烃的代表性化合物，已有的文献报道在红树林湿地水域和表层沉积物中含量较高。本论文通过模拟系统试验，对这两种典型PAHs在红树林生态系统各组成：沉积物、水、红树植物和藻类等多介质中的迁移、转化规律及其对红树植物和藻类的毒性效应进行研究，并探讨了红树林生态系统中优势藻种对PAHs的富集、降解。主要内容和结果包括以下几个方面：（1）研究砂土-红树植物体系中砂土对菲和荧蒽的吸附，以及菲和荧蒽在红树植物组织（根、茎、叶等）的分配转运。将秋茄（Kandelia candel（Linn．）Druce．）一年生幼苗种植在不同浓度菲(1、5、10、50和100μg·g^-1)和荧蒽(2、20、40、80和100μg·g^-1)污染砂土中进行胁迫处理。结果表明PAHs从植物根部向茎叶转运是植物地上部分（茎叶）积累PAHs的重要途径。随着处理浓度的增加和胁迫时间的延长，菲和荧蒽在植物体各组织中的富集量呈逐渐增加的趋势。处理13周后，从富集量来看，植物根、茎、叶中的，菲浓度分别为0．28～4．36μg·g^-1，0．04～0．84μg·g^-1和0．03～0．19μg·g^-1，荧蒽的浓度分别为0．79～35．76μg·g^-1，0．07～1．49μg·g^-1和0．06～0．13μg·g^-1。植物根系对荧蒽的富集量和根富集系数（Rootconcentrationfactor，RCF）均大于菲，而菲的茎富集系数（Shoot concentrationfactor，SCF）、叶富集系数（Leaf concentration factor，LCF）及生物富集系数（Bioconcentration factor，BCF）均比荧蒽的高。秋茄植物有效地去除砂土中菲和荧蒽，平均去除率分别为31．7％和19．7％。（2）研究砂土-红树植物体系中不同浓度菲和荧蒽污染砂土对秋茄幼苗的生长量、叶绿素含量和光合作用、根系活力等生理生态指标的影响。结果表明，随着处理浓度的增加和胁迫时间的延长，幼苗根系受毒害严重，表现为肿大、变黑、腐烂。胁迫前6周根系活力随着处理浓度的增大而增大，第9周后则减小；幼苗根系活力随着胁迫时间的延长呈先增加后降低的趋势。PAHs处理浓度和胁迫时间对植株含水量和根冠比无显著影响，却明显降低了秋茄幼苗的根、茎、叶生物量，总生长量较对照组低，干物质积累量减少。增加PAHs浓度和胁迫时间使叶气孔阻力增加，细胞间隙CO₂浓度减少，叶绿素a、b的含量减少，从而降低了秋茄幼苗的净光合速率和蒸腾速率。菲对秋茄幼苗生长及光合作用的影响大于荧蒽，表明秋茄幼苗对不同类型PAHs有不同的耐受性。（3）研究了藻培养体系中藻类对PAHs的富集、降解以及PAHs对藻的毒性。藻种采自福建九龙江口红树林区，经分离、纯化和培养，将其暴露于含不同浓度菲和荧蒽的培养液中。结果表明，菲对中肋骨条藻和菱形藻的72h-EC₅₀分别为0．95mg·L^-1和0．32 mg·L^-1，荧蒽的72h-EC₅₀分别为0．17 mg·L^-1和0．09 mg·L^-1。中肋骨条藻对菲和荧蒽的耐受性比菱形藻强，荧蒽对实验藻种的毒性比菲大。从藻对PAHs的富集、降解来看，胁迫6 h后，藻即快速地吸附和吸收PAHs；胁迫168 h后，中肋骨条藻和菱形藻对菲的降解率分别为16．4％和54．8％，而对荧蒽的降解仅有6．9％和2．7％，表明实验藻种对菲的降解能力强于荧蒽。在复合毒性实验中，荧蒽存在时中肋骨条藻对菲的降解效率更高，表现出复合污染下的协同作用。不同胁迫时间下，PAHs在培养液中的残留量均有变化；实验藻种对PAHs的富集和降解效率也随胁迫时间的不同而表现出差异。（4）通过水培体系，对PAHs在水体-植物-藻等多介质中的迁移规律进行研究。发现培养初期水相中的PAHs迅速向菱形藻、红树植物根系等介质分配，水里PAHs的浓度显著降低，在植物-藻体系中的下降幅度最大，植物体系次之，藻体系最小。如第1 d，植物-藻、植物、藻体系水相中菲下降幅度分别为78．5％、66．7％和12．1％；而荧蒽的下降幅度分别为88．8％、84．3％和18．2％；荧蒽在不同体系中的分配比菲快。PAHs对藻的毒害作用在胁迫初期就呈现，表现为藻细胞分裂受到抑制，但第4 d后逐渐恢复；胁迫10 d后水中低浓度PAHs反而有利于藻细胞活力的恢复。菲和荧蒽复合胁迫下，藻细胞的生长受抑制程度更加严重，表现为协同效应。菲或荧蒽单独胁迫下其在藻细胞中的富集量随时间的延长呈逐渐降低的趋势，藻细胞对荧蒽的富集量比对菲的高。菲和荧蒽复合胁迫下，植物-藻体系中菱形藻细胞对PAHs的富集量呈先增加后降低的变化。在菱形藻的作用下，水中菲和荧蒽的降解半衰期(T_1/2)分别为105．5 h和120．7 h，联合毒性实验中菲和荧蒽的降解半衰期为74．1 h和108．2 h。从植物根吸收菲和荧蒽的含量-时间关系曲线中发现，在0～30 d内，根中菲和荧蒽含量（干重计）均先增加后逐渐降低，且植物-藻体系中根对菲和荧蒽的最大富集量比植物体系根的大。处理30 d后，红树植物的茎（木质部）、叶对培养液中菲和荧蒽有明显的吸收和积累，但其含量远远小于根中的含量；茎叶中菲的含量明显大于荧蒽。总之，在红树林湿地生态系统中，秋茄植物根系能吸收沉积物中PAHs并向茎叶转运，优势藻种也可快速地富集、降解水体中PAHs，最终起到修复红树林湿地PAHs污染的作用。另一方面，沉积物PAHs污染会使秋茄幼苗根肿大（通气组织的形成）、变黑、腐烂，根系脱氢酶活性降低，叶绿素合成和光合作用受抑制，总生长量和干物质积累量减少。PAHs对藻类有明显的毒害作用，使其光合色素含量减少，藻类可能成为海洋环境水体中PAHs污染的指示生物。该研究成果将为红树林湿地环境风险评价提供重要的科学依据，也为更好地保护和利用红树林资源提供一定的科技支撑。更多还原

【Abstract】 The mangrove ecosystem,as one of the most important intertidal estuarinewetlands along tropical and subtropical coastlines,fulfills important ecosystemservice functions.With the increasing development of destructive activities in coastalecosystems,more and more industrial,agricultural wastewater and living sewage aredischarging directly into offshore marine areas.Human activities have seriously led tothe damage of many mangrove wetlands.The unique features of mangroves such ashigh primary productivity,rich organic carbon and anoxic conditions make them alocation for uptake and preservation of PAHs from anthropogenic inputs.It is veryimportant to investigate the behaviors and environmental effects of PAHs compoundsin mangrove swamps.Phenanthrene （PHE） and fluoranthene （FLA） were selected from 16 priorityPAHs （US EPA） because they were the main representatives of 3-ring and 4-ringPAHs,showing high concentration in mangrove sediments and water.Therefore,theintention of this study was to provide information of the transport and transformationof typical PAHs in simulation systems containing water,sandy soil,algae and plant.Simultaneously,toxicity of typical PAHs to plant and algae was studied.Accumulation and degradation of typical PAHs by the algae enriched from amangrove aquatic ecosystem were discussed.Some successful results have beenreceived.（1） Mangrove plant （Kandelia candel） propagules were obtained from JiulongRiver Estuary Mangrove Nature Reserve,China.K.candel seedlings were cultivatedin PHE or FLA contaminated sandy soil for determining the distribution andtransportation of PHE and FLA in a soil-plant system.The sandy soils withconcentrations of PHE (0,1,5,10,50 and 100μg·g^-1) and FLA (0,2,20,40,80 and100μg·g^-1) were prepared.The results showed that the translocation of PAHs fromroot to shoot was an important pathway for the PAHs intake by plant above-groundpart.The root,shoot and leaf accumulations of PHE and FLA were enhanced with theincrease of their concentrations in the sandy soil.As the exposing time passed,PHEand FLA concentrations of different plant tissues increased significantly in comparison with the control.PHE concentrations of root,shoot and leaf in 13 weeks’treatment were ranged between 0.28～4.36μg·g^-1,0.04～0.84μg·g^-1 and 0.03～0.19μg·g^-1,respectively.And FLA accumulations of root,shoot and leaf were in the rangeof 0.79～35.76μg·g^-1,0.07～1.49μg·g^-1 and 0.06～0.13μg·g^-1,respectively.Thiswork consistently showed that root accumulation of FLA was greater than that of PHE,as shown by root PAH concentrations or RCF.However,the shoot concentrationfactor （SCF） and the leaf concentration factor （LCF） of PHE were much higher thanthose of FLA.In this research,higher values of BCF were more often noted in thePHE treated pots than in the FLA treated pots.The percentage uptake of PHE andFLA by K.candel from sandy soil was 31.7% and 19.7% in average.（2） The influence of increasing concentrations of PHE and FLA on theeco-physiological responses of K.candel,including total biomass,chlorophyll content,photosynthesis and root activity,were investigated.Results were as follows:Afterexposure to PAHs,the roots of K.candel appeared swelling,and then turned blackand rotten.With increasing concentrations of PAHs,the root activity of K.candelseedlings increased gradually before 6 weeks and then decreased after 9 weeks.Withthe prolonging of culture time,the root activity of K.candel seedlings increased atfirst and then decreased;while water content and the root to shoot ratio of K.candelseedling showed no significant difference from the control group at variousconcentrations of PHE and FLA.However,the root biomass and above-groundbiomass of K.candel seedlings decreased significantly in comparison with the control,with an increase of PAHs concentration in the sandy soil.The chlorophyll a,bcontents in the leaves of K.candel decreased moderately with an increase of PAHsconcentration in the sandy soil.Moreover,decrease in stomatal conductance reducedthe input of CO₂,which may be one of the reasons for decreasing net photosyntheticrate of K.candel seedlings leaves.With increasing concentrations of PHE and FLA,decrease in the transpiration rate of K.candel seedling was observed.The effects ofPHE and FLA on the growth of K.candel seedling were similar.However,the toxiceffect of PHE on K.candel was more serious than that of FLA.The tolerance of K.candel to PHE and FLA depended on different physical and chemical properties of thePAHs.（3） In the algae culture system,this study focused on the toxic effect and accumulation and degradation of the two typical PAHs on diatoms found in mangrovearea in Jiulongjiang river estuary,Fujian.After separated,purified and cultured,Skeletonema costatum and Nitzschia sp.were exposed to different concentrations ofPHE and FLA,respectively.The results showed that the values of EC₅₀ of 72 h forPHE to Skeletonema costatum and Nitzschia sp.were 0.95 mg·L^-1 and 0.32 mg·L^-1,respectively.While those of 72h-EC₅₀ of FLA on inhibition of the growths ofSkeletonema costatum and Nitzschia sp.were calculated as 0.17 mg·L^-1 and 0.09mg·L^-1,respectively.The tolerance of Skeletonema costatum to PHE and FLA wasbetter than that ofNitzschia sp..The toxic effect of FLA on Skeletonema costatum andNitzschia sp.was higher than that of PHE.As for accumulation and degradation ofPAHs by diatoms,the results were as follows:After being added into the media for 6h,PAHs were found in both microalgal species,suggesting that Skeletonema costatumand Nitzschia sp.removed PAHs from the media through rapid adsorption andabsorption.For Skeletonema costatum and Nitzschia sp.,the percentage degradationof PHE reached 16.4% and 54.8% after 168 h incubation,and the degradation of FLAwas only up to 6.9% and 2.7%.The results showed that the degradation of PHE wasfaster than that of FLA.In this study,simultaneous degradation of a mixture of PHEand FLA in f/2 medium by Skeletonema costatum was observed,and a synergisticeffect was found.The percentages of PAHs remaining in the media were significantlydifferent at different incubation time,while the differences also found in the rates ofaccumulation and degradation of PAHs by the two microalgal species.（4） Dissipation of PAHs in water in the presence of mangrove plant and algaewas studied.The results indicated an initial rapid uptake of the PAHs by root of K.candel seedlings and Nitzschia sp.,and the corresponding water concentrations oftested PAHs decreased constantly,along with the uptake time.The decrease amplitudeof PAHs in water phase followed the order:plant-algae system＞plant system＞algaesystem.For example,at about 24 h,the concentrations of PHE in water phase ofplant-algae,plant,algae system decreased the amplitude of 78.5%,66.7% and 12.1%,respectively.While those of FLA decreased the amplitude of 88.8%,84.3% and18.2%,respectively.The results suggested that the dissipation of FLA was faster thanPHE in water of different culture systems.The effects of different PAHs andincubation time on cell densities ofNitzschia sp.were studied.The cells in the treated sample did not show any multiplication in 96 h,whereas those in the control hadsignificant division.As the culture time prolonged,low concentration of PAHs inwater was benefit to recovering the viability of Nitzschia sp..The density of cellstreated with single PAH was higher than that treated with mixed PAHs.The resultssuggested that the joint toxicity of FLA and PHE on Nitzschia sp.exhibited synergism.With the prolonging of culture time,accumulation of single PAH by Nitzschia sp.gradually increased.And FLA accumulated in Nitzschia sp.was higher than that ofPHE.With the treatment of PAH mixture,accumulation of PAHs by Nitzschia sp.increased at first and then decreased in the plant-algae system.And the half-lives (T_1/2)for PHE and FLA degradation at the presence ofNitzschia sp.were 105.5 h and 120.7h,larger than those in PAH mixture （74.1 h and 108.2 h）,respectively.After 30 dtreatment,root accumulation of PAH increased at first and then decreased,and higherPAH accumulations of root were more often noted in the plant-algae system than inthe plant culture systems.Distribution of PAH in different plant tissues wasinvestigated.The results showed that the accumulation of PAH in xylem and leaf wasobviously lower than that in root.Moreover,PHE accumulation in xylem and leaf waslarger than FLA.In mangrove wetland ecosystem,root of K.candel absorbed PAHs fromsediment and transmitted to shoot and leaf by transpiration of plant.And dominantmicroalgal species removed PAHs in the water environment through rapid adsorptionand absorption.On the other hand,after exposure to PAHs in sediment,the roots of K.candel appeared swelling,and then turned black and rotten.With increasingconcentrations of PAHs,the root activity,chlorophyll contents and net photosyntheticrate of K.candel decreased.Moreover,the root and above-ground biomass of K.candel decreased significantly in comparison with the control.The toxic effect ofPAHs on microalgal species was observed.The results suggested that microalgaecould be indicator organisms to PAHs pollution in marine environment.The researchprovides reliable information for environmental risk assessment of mangrove wetlandand a scientific support for protection of mangrove resources.更多还原