【作者】 钟顺清；

【导师】 徐建明；

【作者基本信息】 浙江大学 ， 土壤学， 2009， 博士

【摘要】 人工湿地广泛用于处理生活污水和控制农业面源污染。湿地植物是人工湿地系统的重要组成部分，植物根系具有发达的通气组织，能将大气中和光合作用产生的氧运送到根部，在根系与土壤界面形成微氧化区域，使植物根表形成铁氧化物胶膜。铁膜的形成不仅影响根际土壤中物质的迁移和转化，而且影响植物对矿质元素的吸收利用。因此，研究湿地植物根表铁膜对磷、铅迁移、转化及植物有效性的影响，对深入了解湿地植物净化水质的内在机理有着积极的意义。本文通过调查采样研究了不同湿地植物在自然条件下形成根表铁膜的差异性以及对磷吸附的特征，探讨了根表铁膜形成对景观湿地植物不定根生长和根系活力的影响，同时也分析了湿地植物土壤微生物群落结构对外加铅、铁的响应。根据自然环境条件，并通过溶液培养试验和土壤盆栽试验系统地研究了根表铁膜影响磷、铅迁移、转化及植物有效性的机理，主要结果如下：(1)通过对不同生境的湿地植物采样分析，发现不同生境的湿地植物根表铁膜量差异较大，同一生境不同植物根表铁膜量差异明显，即同属于莎草科植物根表铁膜含量的顺序为：水毛花＞蔗草＞旱伞草，其中水毛花是旱伞草的6.5倍。(2)铅抑制湿地植物根表铁膜的形成与积累，添加铁促进根表铁膜的积累。溶液培养实验发现高铅对铁膜流失的影响大于低铅，根表铁膜量越大，其流失量更多。在铅污染土壤中，同一铅水平下，宽叶香蒲和黄菖蒲根表铁膜量都随铁添加量的增加呈上升趋势；在同一铁水平下，宽叶香蒲根表铁膜量随铅浓度的增加而降低，而黄菖蒲根表铁膜量并没有随铅浓度的增加而明显降低。(3)当铁浓度低于100 mg／L时，宽叶香蒲新形成不定根生物量随铁浓度的增加降低，但当铁浓度高于100 mg／L时，不定根生物量呈增加趋势；而黄菖蒲的新形成不定根的生物量与根表铁膜量的相关性不显著。植物根表形成铁膜后，宽叶香蒲根系活力与其根表铁膜量呈显著的负相关，相关系数为-0.861~*；而黄菖蒲在各处理之间的根系活力为2.36-5.48μg／g·h，总体变化幅度不大。(4)土壤微生物群落结构对外源铅铁的响应表现为：磷脂脂肪酸(PFLAs)表征的微生物总量在根际高于非根际，香农-维纳指数(H)在500 mg／kg铁处理水平下，非根际土中微生物群落结构多样性随铅浓度增加呈上升趋势，而根际土壤中H指数在高浓度铅(500、1000 mg／kg)处理时高于低铅处理。聚类分析表明根际土中微生物群落结构主要受铁的影响，而非根际土铅起主导作用。(5)不论是未污染土壤还是铅污染土壤，湿地植物根表吸附的磷与根表铁膜量呈明显的正相关。而对铅的吸附取决于铁膜厚度大小，铁膜量大时则呈正相关，否则相关性不显著。(6)溶液培养实验中，铁膜量较少时促进了宽叶香蒲对磷的利用，超出了30 g／kg则抑制了磷的利用；而根表铁膜对黄菖蒲地上部磷含量的影响表现出抑制作用。在50 mg／L铅处理中，根表铁膜提高了宽叶香蒲体内铅的含量；而对黄菖蒲而言，一定量根表铁膜促进了铅向根中迁移，但诱导铁浓度高于100 mg／L时则抑制铅向根中迁移。根表铁膜提高黄菖蒲地上部铅含量。铅污染土壤中，添加铁促进了根表铁膜的形成与积累，当铁与铅添加量之比值为1时有助于磷、铅在宽叶香蒲体内的积累，而当铁添加量为100 mg／kg时，却有助于磷、铅在黄菖蒲植株体内积累。更多还原

【Abstract】 Constructed wetland was widely used in treating domestic sewage and controllingagricultural non-point source pollution. Wetland plant is one of the most essentialcomponents in constructed wetland system. The oxygen from atmosphere andphotosynthesis was transported to roots through aerenchyma. Micro-oxidation zoneformed in rhizosphere, leading to iron plaque formation on plant root surfaces. Formationof iron plaque not only affects the migration, transformation and absorption of mineralelements in rhizosphere, but also their utilization by plants. Therefore, it is very importantto study the effects of iron plaque on migration and bioavailability of phosphorus and leadin order to understand the mechanism of purifying water by wetland plants.The difference of iron plaque and characteristics of phosphorus adsorption wereinvestigated through sampling wetland plants under natural condition to determine ironplaque effects on root activity and growth of adventitious roots, and to examine the effectof lead and iron on soil microbial community structure. The formation of iron plaque onroot surface and its effects on utilization of phosphorus and lead by Typha latifolia andIris pseudacorus were studied under solution culture and pot experiments. The resultsshowed that the amount of iron plaque was affected by the addition of iron and lead, andthen influenced the utilization of phosphorus and lead by plants. The mechanism of ironplaque effect on bioavailability of phosphorus and lead by plants was discussed. The mainfindings are as follows:(1) The amount of iron plaque on the root surfaces varied greatly in various wetlandniches and species. For the Cyperaceae family plants, the amount of iron plaque followedthe order of Scirpus triangulates L.＞Scirpus triqueter L.＞Cyperus alternifolium L. ssp.Flabelliformis(Rottb.) Kuk. and was 6.5 times in Scirpus triangulates L.’s than Cyperusalternifolium L. ssp. Flabelliformis(Rottb.) Kuk.’s.(2) Formation and accumulation of iron plaques were inhibited by lead, butpromoted by iron. Solution culture experiment showed that higher concentration of lead caused more loss of iron plaque, and the loss of iron plaques was more when iron plaqueswere abundance. After iron was added to lead contaminated soil, the amount of ironplaque on the roots of broad-leaf cattail and yellow flag was increased with the increase ofiron addition. The amount of iron plaque on roots of broad-leaf cattail was decreased withaddition of lead, but that on root of yellow flag was not obviously influenced by theaddition of lead.(3) In solution culture experiment, the fresh weight of new adventitious roots inbroad-leaf cattail was decreased with the increase of ferrous concentration from 0 to 100mg/L, and then was increased after ferrous concentration was beyond 100 mg/L. Therewas no obvious correlation between fresh weight of adventitious roots in yellow flag andferrous concentration in solution, but a significantly negative correlation between rootactivity of broad-leaf cattail and amounts of iron plaque with a correlation coefficient of0.861. The root activity of yellow flag ranged from 2.36 to 5.48μg/g·h in this experiment.(4) The response of microbial community structure in the soil planted broad-leafcattail with the addition of iron and lead were as follows: the microbial biomasscharacterized by phospholipid fatty acid in the rhizosphere was more than that in the bulksoil. Shannon index(H) in the bulk soil was increased with lead of 500 mg Fe/kg level.The H index in the rhizosphere in treatments with 500 and 1000 mg/kg lead wassignificantly higher than that of low lead addition. Based on cluster analysis, themicrobiology community was mainly affected by lead nitrate in bulk soil, but by ferroussulfate in the rhizosphere.(5) There was significantly positive correlation between amounts of phosphorusadsorption and iron plaque on the roots surface of wetland plant planted in bothno-polluted soil and lead contaminated soil. The correlation between lead adsorption andiron plaque depended on the amounts of iron plaque.(6) Solution culture experiment showed that the small amounts of iron plaque formedon the roots surface of broad-leaf cattail would promote the phosphorus utilization,whereas, the inhibition was observed when the amount of iron plaque was 30 g/kg, exceptthe treatment of 200 mg Fe/L. Phosphorus content in over-ground parts of yellow flag wasdecreased with the formation of iron plaque. The formation of iron plaque on the roots of broad-leaf cattail could increase the content of lead in roots and over-ground at thetreatment of 250 mg Pb/L in solution. Content of lead in roots of yellow flag wasimproved by iron plaque in 10 mg Pb/L solution, and formation of iron plaque with thetreatment of ferrous less than 100 mg/L increase the content of lead in roots. Once theferrous concentration was beyond 100 mg/L, iron plaque would decrease the content oflead in roots. When the ratio of iron to lead added was 1, accumulation of phosphorus andlead in over-ground of broad-leaf cattail was more than that with other treatments, andlead content in over-ground parts of yellow flag was promoted by iron plaque. Theaccumulation of phosphorus and lead in yellow flag with the soil treatment of 100 mg/kgiron was more than that of 0 and 500 mg/kg iron, and amount of phosphorus and lead inroots was higher than that in over-ground parts.更多还原