【作者】 吴湘；

【导师】 杨肖娥；

【作者基本信息】 浙江大学 ， 农业资源利用， 2008， 博士

【摘要】 水体富营养化已成为当代许多国家政府和公众最为关注的环境问题之一。随着富营养化的加剧,藻类水华发生的频率和幅度也大大增加,特别是有毒水华对水环境的危害和水生生物的安全威胁已严重影响了水体的正常功能、社会和经济的可持续发展。氮（N）和磷（P）是引起水体富营养化的主要营养盐因子,其中最主要的限制因子就是磷,因此如何经济、有效和简便地去除富营养化水体中的磷是目前解决水体富营养化问题的关键。近年来,随着人们对生态环境重视程度的提高,使用生态修复的方法来治理富营养化水体已成为新的研究热点。生态修复水体富营养化和植物去除营养盐的能力大小十分相关。本论文应用水体修复小试和中试等技术平台,研究比较了不同季节性植物材料对富营养化水体中P的吸收去除能力以及产生植物之间基因型差异的原因分析。取得的主要创新性成果包括:1.通过比较研究不同季节性的漂浮栽培植物材料[夏秋季:大漂（Pistiastrariotes Linn）、矮杆美人蕉（Canna flaccida）、水鳖（Hydrocharis dubia）:冬春季:冬牧70（Secale Celeale L.）、串叶松香草（Silphium petroliatumLinn.）、多花黑麦草（Lolium multVlorum Lam.）]对富营养化水体中磷素（P）及其他污染物的吸收净化效应的基因型差异,筛选出分别适合在夏秋季（较高温季节）和冬春季（较低温季节）用来进行富营养化水体植物生态修复工程的高效除磷植物材料,以达到常年保持高效净化水质之目的。结果表明,大漂（Pistiastratiotes Linn.）和冬牧70（Secale cereale L.）分别是夏秋季和冬春季对富营养化水体中的P素及其他污染物去除效果最好的植物材料。试验结束后,水体总磷（TP）平均降低了50%左右,化学需氧量（CODMn）平均降低了35%左右,生化需氧量（BOD₅）平均降低了55%左右,叶绿素a（Chla）浓度平均降低了40%左右,较好地抑制了藻类的暴发,降低水体pH值且维持在中性水平,并能显著提高水体透明度。同时我们还通过比较不同季节性的漂浮栽培植物材料对不同P污染水平的富营养化水体（低P:0.01 mg/L;高P:0.50 mg/L）中磷素及其他污染物的去除效应,发现大漂和冬牧70都比较适合用来修复高P（0.50 mg/L）污染水体,因为此时这两种植物对污水中的P素去除效率最高,对其他污染物的净化效果也最好;其次是矮杆美人蕉（Canna flaccida）和串叶松香草（Silyhiumperfoliatum Linn.）,它们也较适合在高P污染水体中生长;除磷效率较低、净化效果较差的植物则分别是水鳖（Hydrocharis dubia）和多花黑麦草（LoliummultVlorum Lam.）,且这两种植物都较适合在低P污染水体中生长。2.通过研究高效除磷的漂浮栽培植物大漂（Pistia stratiotes Linn.）和冬牧70（Secale cereale L.）以及低效除磷的漂浮栽培植物水鳖（Hydrocharisdubia）和多花黑麦草（Lolium multVlorum Lam.）对P吸收的动力学特点与植物去磷效应的相关性,结果发现大漂和冬牧70对磷吸收的最大吸收速率(V_max)和米氏常数（K_m）都要高于对照植物水鳖和多花黑麦草。V_max越高代表植物吸收P素的能力越强;K_m越小代表植物对低P的亲和能力越强。因此,大漂和冬牧70对磷吸收的能力较强且较适合在高P污染水体中生长,而水鳖和多花黑麦草对磷吸收的能力较低且较适合在低P污染水体中生长。研究结果还表明,大漂和水鳖、冬牧70和多花黑麦草这四种不同季节性的漂浮栽培植物生长速率最快、对富营养化水体中P素去除效率最高的植物生长阶段都是在5-20天的这个时间段内,其次植物生长较快、除磷效果较好的则是在20-35天的这个时间段内。3.通过研究高效除磷的漂浮栽培植物大漂（Pistia stratiotes Linn.）和冬牧70（Secale cereale L.）以及低效除磷的漂浮栽培植物水鳖（Hydrocharisdubia）和多花黑麦草（Lolium muitVlorum Lam.）的酸性磷酸酶活性差异与植物去磷效应的相关性,结果发现在不同的供磷水平下（低P供应:0.01mg/L;正常供P:0.50mg/L）这四种植物的酸性磷酸酶活性都会产生不同程度的变化。低磷胁迫能显著增加大漂和水鳖、冬牧70和多花黑麦草的叶片酸性磷酸酶活性;不同植物的叶片酸性磷酸酶活性对低磷胁迫的反应也存在显著的差异,低P胁迫时水鳖和多花黑麦草的叶片酸性磷酸酶活性的增加幅度大于大漂和冬牧70。同样地,低磷胁迫还能够显著增加这四种植物的根系分泌酸性磷酸酶活性,该酶活性的增加可以显著提高磷的生物有效性和植物对磷素的利用效率,由此可见水鳖和多花黑麦草比大漂和冬牧70更适合在低P污染水体中生长。4.不同环境因子对漂浮栽培植物去磷效应的影响研究的结果表明:①在低P处理时,大漂和冬牧70产生最高除磷效率的最佳氮磷比（N/P）是7.5:1;而在高P处理时,大漂和冬牧70产生最高除磷效率的最佳氮磷比（N/P）则是2.5:1;②有效微生物（EM菌）具有较好的氮磷去除功能,特别是将其与高等植物联合对污水进行处理时效果更好,大漂和冬牧70在EM菌的作用下迅速大量繁殖,从而更有效地抑制了藻类的生长;③大漂的最适生长温度是25℃,冬牧70的最适生长温度是15℃,此时这两种植物的生长情况最好,且对水体中P素和其他污染物的吸收去除能力也最强;④大漂和冬牧70的最适pH值都为6.7左右,此时这两种植物的生长情况最好,且对水体中P素和其他污染物的吸收去除能力也最强;⑤水生漂浮植物大漂最适合的曝气方式是连续曝气,这种曝气方式较接近水生漂浮植物适合生长的自然流动水体环境,而冬牧70最适合的曝气方式是间歇曝气。在适当的曝气方式下,大漂和冬牧70这两种漂浮栽培植物对水体中P素和其他污染物的去除能力最好。5.植物修复富营养化水体过程中P的去除途径主要包括植物吸收（包括微生物降解强化植物吸收部分）、植物根系吸附、底泥吸附（絮凝沉淀）和还原状态下厌氧菌分解产生的P挥发（PH₃）这四个部分。本试验以高效除磷的漂浮栽培植物大漂（Pistia siratiotes Linn.）和冬牧70（Secale cereale L.）为研究对象,通过研究模拟条件下的植物生态修复系统,明确了这四种不同的P去除途径分别对水体中总磷（TP）去除量的贡献率大小。结果表明:在植物修复富营养化水体过程中最主要的P去除途径是植物吸收作用和底泥吸附作用,分别可占水体中TP去除量的23%-58%、27%-51%;其次是植物根系吸附作用,可占水体中TP去除量的13%-28%;贡献率最低的是还原状态下的P挥发（PH₃）,一般低于1.5%,这部分的P损耗几乎可以忽略不计,可见还原状态下的P挥发对水体中TP的去除发挥的作用极小。更多还原

【Abstract】 Water eutrophication has become one of the most important environmental problems all over the world.With occurrence of water eutrophication,the frequency and extentof alga bloom has been increased greatly,especially the harm of toxic alga bloom has seriously embarrassed the normal function of water body,continue development of society and economy.Nitrogen（N）and phosphorus（P）are the two main nutrient pollutants which affect water eutrophication easily,however,P is considered to be the limiting nutrient for water eutrophication.Thus,how to remove P from eutrophic water effectively and at low cost has become the key issue for developing technologies for controlling and remediate water eutrophication.In resent years,ecological remediation methods have become new and hot study point. Ecological remediation of eutrophic water is largely dependent on the ability of the plants used to remove the nutrients.In this paper,different seasonal plant species were compared for their abilities of removing P from eutrophic water,and some mechanisms behind genotypic difference in P uptake and removal from eutrophic water were studied,using indoor and field experimental technic platforms.The main innovative results are summarized as follows:1.In order to screen out plant species with highest P removal efficiency,at different seasons（warm season and cool season）,six plant species（e.i.Pistia stratiotes Linn, Secale cereale L.,Pistia stratiotes Linn.,,Canna flaccida,Hydrocharis dubia,Lolium multVlorum Lam）were selected to compare their efficiency of P removal and other pollutant removal from eutrophicated water in summer（with high temperature）and in winter（with low temperature）.The results showed that Pistia stratiotes Linn.and Secale cereale L.were the two species with highest efficiency for removing P and other pollutants in summer and winter,respectively.After the experiment,total phosphorus（TP）was decreased on average by around 50%,CODMn by 35%,BOD₅ by 55%,and Chla concentration by 40%.Alga bloom in treated eutrophic water was restrained effectively,pH was decreased to around 7.0,and water transparence was improved markedly.When the plants were grown in eutrophic water with low P （0.01mg/L）and high P（0.50 mg/L）,Pistia stratiotes Linn.and Secale cereale L.were found to be more suitable for remediating high P-polluted eutrophic water because they showed the highest efficiency for P removal and other pollutant removal,follwed by Canna flaccida and Silphium perfoliatum Linn..Whereas Hydrocharis dubia and Lolium muItVlorum Lam.showed the lowest P removal efficiency,but suitable for growing at low P-polluted eutrophic water.2.By comparing the characteristics of P uptake by the four plant species（two efficient ones Pistia stratiotes Linn and SecaIe cereale L,and two inefficient ones Hydrocharis dubia and Lolium multVlorum Lam）,we found that Pistia stratiotes Linn.and Secale cereale L.had higher Vmax and Km of phosphate absorption than Hydrocharis dubia and Lolium muitVlorum Lam.indicating that Pistia stratiotes Linn.and Secale cereale L.had higher ability absorbing phosphate.However higher Km indicated lower affinity of the roots,and Pistia stratiotes Linn.and Secale cereale L.were proper to gown in high P-polluted water.In contrast,Hydrocharis dubia and Lolium multVlorum Lam.had lower Km values than Pistia stratiotes Linn.and Secale cereale L.,implying they are suitable to grow in low P-polluted water.The results also showed that the highest P removal efficiency was always observed at the growth stage of 5-20 days of these four different plant species（Pistia stratiotes Linn.,Secale cereale L.,Hydrocharis dubia and Lolium multVlorum Lam.）.Secondly period with high P removal efficiency was found at the growth stage of 20-35 days.3.The results from the study of P removal with relation to phosphatase activities among the four plant species（Pistia stratiotes Linn.,Secale cereale L.,Hydrocharis dubia,Lolium multVlorum Lam）showed that that acid phosphatase activity（APA） had different response to P supplied levels.At low P supply（0.01mg/L）,leaf APA of all the four different plant species were enhanced obviously,but different upon plant species.The extent of increase in leaf APA due to low P stress was greater in Hydrocharis dubia and Lolium multVlorum Lam.than those in Pistia stratiotes Linn. and Secale cereale L..Similarly,root APA of all the four plant species were enhanced obviously when they were subjected to low P stress.The enhancement of root APA could greatly improve P bioavailability and use efficiency.Thus it can be concluded that the two contrast plant species,i.e.Hydrocharis dubia and Lolium multVlorum Lam.,could grow in low P-polluted water better than Pistia stratiotes Linn.and Secale cereale L.4.The study of different environmental factors influencing P removal efficiency by the plant species showed that①The best N:P ratio which can induce the highest P removal efficiency was 7.5:1 when Pistia stratiotes Linn.and Secale cereale L.were under low P（0.01 mg/L）treatment,however,the best N:P ratio which can induce the highest P removal efficiency was 2.5:1 when Pistia stratiotes Linn.and Secale cereale L.were under high P（0.50 mg/L）treatment;②EM could remove N and P nutrients from eutrophicated water very effectively especially when it was combined with plants.Pistia stratiotes Linn.and Secale cereale L.could grow and remove P faster, and control alga bloom more effectively when they were combined with EM;③The optimal temperature for growing well and removing P from eutrophic water was 25℃for Pistia stratiotes Linn.while 15℃for Secale cereale L.;④The optimal pH was around 6.7 both for Pistia stratiotes Linn.and Secale cereale L.to grow well and remove P from eutrophic water;⑤Continuous aeration was found to be the optimal aeration mode for the floating hydrophyte Pistia stratiotes Linn.because it was much closer to the natural environment of floating hydrophytes.However,intermittent aeration was observed to be most suitable for Secale cereale L.to effectively remove P from water.The two plant species showed higher P removal efficiency and purifying effectiveness when they were supplied with the optimal aeration mode,respectively.5.The fates of P removal from eutrophicated water in the process of phytoremediation included plant absorption,root adsorption,sediment adsorption（mainly including flocculation and deposition）and P volatilization（PH₃）under reductive state.In this study,we took Pistia stratiotes Linn.and Secale cereale L.which had higher P removal efficiency as experiment materials.The contribution ratios of these four fates of P removal in the total phosphorus（TP）removal from eutrophicated water were respectively studied through simulating ideal ecological phytoremediation system. The study results showed that the two main fates of P removal were plant absorption and sediment adsorption whose contribution ratios respectively were 23-58%and 27%-51%in TP removal;Secondly was root adsorption whose contribution ratio was 13%-28%;The lowest contribution ratio was observed in the track of P volatilization under reductive state whose contribution ratio was only lower than 1.5%,thus,this contribution in TP removal was very small and could be neglected.更多还原