【作者】 郑九华；

【导师】 冯永军； 史衍玺；

【作者基本信息】 山东农业大学 ， 土壤学， 2008， 博士

【摘要】 沉陷地是我国主要的退化土地之一,目前采用的复垦方式多为充填覆土,表层覆土的缺乏是制约当前土地复垦工作的主要问题。另外,大量固体废弃物的产生出来也导致了很多环境问题。因此,提出了利用固体废弃物构造土地复垦基质的思想,并把粉煤灰分别按一定比例与酒糟、糠醛渣、污泥等混合成复垦基质进行了试验研究。前期研究结果显示基质中重金属含量较高,特别是镉(Cd)的含量超过了国家土壤环境质量二级标准,必须采取措施降低基质中的重金属镉(Cd)的含量,又设计了降低重金属镉(Cd)含量的植物修复试验。采用盆栽试验的方法,先后对六种不同基质进行了研究,提出了评价植物对基质中重金属元素吸收能力的指标体系,探讨了“超富集植物”的概念。本研究对节土造田、增加耕地面积、改善沉陷地周边环境、实现固体废弃物的资源化利用、促进资源-环境-社会经济的协调发展都具有积极的现实意义,同时也为重金属元素的植物修复研究和“超富集植物”的筛选和培育提供了新的思路和理论依据。论文的主要成果和结论如下:1)通过对基质理化性质和植物生长情况的试验,获得糠醛渣、污泥、酒糟三种有机固体废弃物分别与粉煤灰混合构造土地复垦基质的适宜比例为5-20%。2)经过六年的植物种植试验,基质理化性质得到了明显改善。基质疏松,孔隙率大,通气性好,田间持水量呈逐年增加趋势,容重均低于土壤对照;各基质pH值基本维持在中性范围;有机质和速效氮、磷、钾含量配置初期远高于对照,虽然由于植物吸收和淋洗有所降低,但是仍维持在较高水平;基质配置初期盐分含量较高,经过一段时间的淋洗后,均降至2 g·kg-1以下;各基质重金属元素含量均高于土壤对照,且随着种植年限的增长而降低,除镉(Cd)外,均低于土壤环境质量二级标准值,因此要使基质能安全地用于农业生产,应采取措施降低镉(Cd)的含量。3)建立了基质质量综合评价模型,并对三种基质质量进行了评价,结果与基质中植物生长情况相吻合,说明模型与实际相符合。4)各植物在基质1、2、3中的出苗率普遍高于对照,而且随着种植年限的延长,出苗率有提高的趋势。在基质中种植的植物,初期长势普遍低于土壤对照,随着基质不断熟化,植物均超过土壤对照。从叶绿素含量来看,除了初期有一定不良影响外,总体上与土壤相当。有多种植物的重金属含量超过了相应的国家标准,因此在基质上种植植物时,尽量选择非食用性植物品种,即使种植了蔬菜和牧草等植物,也不应将收获后的产品供人类食用或用于畜牧生产,以免危害人体健康。5)建立和研究了复垦基质先锋植物的适宜性评价模型,结果表明,不同基质中适宜的先锋植物分别如下:基质1为苜蓿,基质2为桧柏、棉花和高羊茅,基质3为桧柏、早熟禾、高羊茅、棉花和苜蓿。6)探讨了评价重金属元素植物修复能力的指标体系和“超富集植物”的概念。以对植物重金属元素的植物修复实际效果为出发点,提出了评价重金属元素的植物修复能力的指标,如吸收模量、修复年限、相对修复年限和相对修复指数等,建立了以相对修复年限为核心的评价体系,并拟定了评价标准。以相对修复年限为评价指标定义相对修复年限为0-10年的植物为“超富集植物”,10-50年的植物为“富集植物”。7)在由不同废弃物按一定的比例混合配制的六种土地复垦基质上,系统地研究了几种植物对重金属镉(Cd)的吸收和富集情况,结果表明,相对修复年限既适用于不同植物对同一种重金属元素的吸收能力的评价,又适用于同一植物对不同重金属元素的吸收能力的评价,是衡量重金属元素植物修复效果的理想指标。8)从不同植物对同一基质重金属镉(Cd)的吸收和富集能力看,不论是经过多年种植的基质,还是第一次种植的基质,小白菜和油菜都是相对理想的植物;而黑麦草、高羊茅和苜蓿的吸收效果并不理想。从同一种植物对不同基质中重金属镉(Cd)的吸收和富集能力看,对基质1、基质2和基质3来讲,小白菜、油菜和甘蓝更适用于在由粉煤灰与酒糟混合配制的基质3、而黑麦草和高羊茅则较适用于由粉煤灰与糠醛渣混合配制的基质1;对基质I、基质II和基质III来讲,由于构成基质的糠醛渣、污泥和酒糟的理化性质和化学成分的差异,植物的适宜程度并未出现一致的规律性。9)根据“超富集植物”的相对修复年限评价标准的0-10年和“富集植物”的10-50年,小白菜、油菜和甘蓝对基质1、基质2和基质3是比较理想的“富集植物”,对基质I、基质II和基质III,只有小白菜完全表现出这种特征,所以,植物对重金属的“超富集”和“富集”特征是相对的,应当指明在什么条件下才有意义。10)如果考虑到植物吸收和重金属淋溶两方面的作用,在种植适宜植物的情况下,基质中重金属镉(Cd)的含量会在10-15年间降至国家土壤环境质量二级标准以下,根系作用层可以满足一般农业生产的需要。更多还原

【Abstract】 Subsiding wasteland is one of the main degradation lands in China and the main reclaiming method is filled and covered with soils. The lack of covered soil is becoming the main problem in land reclamation. On the other hand, great amount of solid wastes are produced and it lead to some environment problems. So the idea that solid wastes were mixed and used as land reclaiming substrates was put forward. Some substrates that separately mixed with fly ash, furfural residue, sewage sludge and lees were studied. The prophase results showed that the content of heavy metals in the substrates were higher than that of the soils, especially the content of Cd exceeded the standard of Soil Environment Quality StandardsⅡin China. Some measures must be adopted to reduce the content of Cd in the substrates, so the experiments whose purpose was to reduce the content of Cd were made. In the experiments six substrates were successively studied with the potted method and some indexes to evaluate the capability of plants absorbing heavy metal Cd from the substrates were put forward. At the same time the comprehension about hyper-accumulator of heavy metal was advanced.The study had great operation significance in economizing soils, increasing the land area, improving the environment quality around the subsiding lands, utilizing solid wastes as resources. The results can provide new ideas and theoretic evidences to the phytoremediation of heavy metals and the selection of hyperaccumulator. The main results and conclusions were as follows:1) Based on the study of physicochemical properties in the substrates and the effects on the growth of plants, the suitable proportions were 5~20%.2) The substrates had higher porosity, better air permeability and less bulk density than soils. The pH maintained around the range suitable to the growth of plants. The salt content was very high in the early period and after washing by rainwater and irrigational water for a year around, the salt content decrease under 2 g·kg-1. The organic matter and available nutrient content was more than that of soils in the early period and decreased because of the plants absorption and washing of water, but still kept a high-level which could satisfy with the need of plant growth. All the contents of heavy metals in the substrates were higher than soils and only the content of Cd higher than the Soil Environment Quality StandardsⅡ, so some measures must be adopted to reduce the content of heavy metal Cd in order to ensure the substrates to be used in agriculture safely.3)The substrate quality evaluation model was established and the substrates integrated quality was evaluated. The results showed that the substrate quality indexes were accord with the growth of plants.4) Preferable biological effects of planting on substrates had been gotten. The emergence rate of each plant in substrate 1, substrate 2 and substrate 3 was all higher than that of soil comparison plant, and with the increase of planting time, the emergence rate went up. Because of worse physicochemical properties, the plant height was lower than that of soils in germination period, but with the maturing of substrates, the plants growth condition improved gradually. The substrates had not large effect on the chlorophyll content as a whole except ryegrass and fescue were affected a little. For some kinds of vegetables and pasturages, the contents of some heavy metals surpass the relevant quality standards, so when some crops were planted on the substrates, the uneatable species should be selected preferably and if some kinds of vegetables and pasturages must be adopted, the output could not be provided to mankind and also not be used in farming, in order to avoid harming peoples’health.5) The expediency evaluation model of pioneer plant on substrates was established and some plants were studied. The results show that the expediency evaluation of pioneer plants were respectively that clover was expedient to substrate 1, juniper, cotton and fescue were expedient to substrate 2 and juniper, annual bluegrass, fescue, cotton and clover were expedient to substrate 3.6) Some indexes to evaluate the capability of the phytoremediation on heavy metals and the comprehension about hyperaccumulator were put forward. Started from the practice effects of the phytoremediation on heavy metals, a few new indexes such as absorption modulus, remediation age, relative remediation age and relative remediation indexes et al were advanced. In order to weigh the capability of plants absorbing heavy metals from the substrates, the evaluation system whose core was relative remediation age and the evaluation standard were established. Based on the evaluation system, the plants whose relative remediation age was between 0~10 years were named as“Hyperaccumulator”and those between 10 ~ 50 years were named as“Accumulator”.7) In the experiments six kinds of substrates were mixed with different solid wastes and the absorption and enrichment of plants on heavy metal Cd was studied. The results showed that relative remediation age was an ideal index to evaluate the capability of the phytoremediation on heavy metals, because it took into account more factors which affected the absorption evaluation effects than others, such as the heavy metal content and the biomass of the over-ground part of plants, the heavy metal content and the whole gross in substrates, harvesting frequency of plants and the environment standard of heavy metal. This made relative remediation age be suitable to the sorption capability evaluation of not only different plants on one heavy metal but also one plant on different heavy metals.8) It can be drawn from the relative remediation age of heavy metal Cd that the absorption capability of different plants was not same. Pakchoi and rape were the ideal plants to all substrates and ryegrass, fescue and clover were not ideal. In addition, for substrate 1, substrate 2 and substrate 3 that utilized for some years, pakchoi, rape and cabbage were suitable to substrate 3 mixed with fly ash and lees and ryegrass and fescue were suitable to substrate 1 mixed with fly ash and furfural residue. For substrate I, substrate II and substrate III that utilized in the first year, because of the differences of their physicochemical properties and chemical constituents, the suitability of the plants didn’t appear accordant regularity.9)According to the relative remediation age evaluation criterions of hyperaccumulators ( 0~10 years) and accumulators( 10~50 years), pakchoi, rape and cabbage were ideal accumulators of heavy metal Cd for substrate 1, substrate 2 and substrate 3, but for substrate I, substrate II and substrate III, only pakchoi had this character completely. So the character of“hyperaccumulator”or“accumulator”was relative.10)If considering the dual functions of plant absorption and heavy metal eluviations, under the condition of growing some suitable plants, the heavy metal Cd content of substrates would drop down to the Soil Environment Quality Standards II in 10~15 years and the heavy metal Cd content of root layers could satisfy the needs of the common agricultural production.更多还原