【作者】 曲贵伟；

【导师】 依艳丽；

【作者基本信息】 沈阳农业大学 ， 农业环境与生态， 2011， 博士

【摘要】 土壤重金属污染对植物生长和土壤生物活动有明显的毒害作用,同时对生态系统稳定和人类健康存在潜在的威胁。当污染面积较大,时间较长时,应用土壤原位修复技术是一个合适的选择。而对于不同的污染土壤选择合适的修复物十分重要。本文采用了室内溶液培养、盆栽试验和半野外试验(semi-field experiment)等方法主要研究了聚丙烯酸盐(聚丙烯酸钾、聚丙烯酸铵及聚丙烯酸钠)对重金属离子的吸附效应和能力及对外加重金属污染土壤和长期重金属污染土壤的修复作用,此外我们也探讨了葡萄牙城市垃圾堆肥对矿区重金属污染土壤修的复作用和植物修复作用。本研究是首次将聚丙烯酸盐应用到重金属污染土壤的修复上,丰富了重金属污染土壤修复技术,并为合理应用城市废弃物如废弃尿不湿和城市垃圾修复重金属污染的矿区土壤提供实践依据。研究结果表明：(一)聚丙烯酸盐对水溶液中重金属离子的吸附效应的试验结果表明：在重金属水溶液中,聚丙烯酸盐可快速吸附重金属离子且在120天的浸泡过程中吸附数量基本稳定。在pH 4.5-6.5条件下,聚丙烯酸盐对重金属离子的吸附量最大。聚丙烯酸盐吸附重金属离子后,吸水能力显著下降；聚丙烯酸盐对重金属的吸附能力远大于醋酸铵,略高于柠檬酸,而与EDTA相近。在土壤盆栽试验中,聚丙烯酸盐可以显著改善Cd污染条件下的黑麦草的生长,显著降低黑麦草对Cd的吸收,土壤中的水溶性Cd的数量也显著降低。在盆栽条件下,聚丙烯酸盐的合理用量应该在0.1%左右。(二)通过盆栽试验研究了在外源性复合重金属污染土壤上聚丙烯酸盐对黑麦草生长、黑麦草中重金属含量以及土壤中水溶性重金属的含量的影响。无论在单一重金属还是复合重金属污染的土壤上,聚丙烯酸盐的使用可以明显改善外源重金属污染土壤上黑麦草的生长并显著地降低植物体内重金属的含量,同时土壤中水溶性重金属的含量也显著下降。复合污染土壤中重金属之间的相互竞争导致了植株和土壤中重金属含量之间的明显差异。(三)通过盆栽试验研究了聚丙烯酸盐和高粱修复长期Cd污染土壤的效果,结果表明与对照土壤相比,聚丙烯酸盐的应用显著改善了Cd污染土壤上高粱的生长,降低了植株体内吸收的Cd的含量和过氧化氢酶及抗坏血酸氧化酶的数量；土壤中的有效Cd的含量也显著下降,而土壤中各种酶的活性则显著提高,土壤性质得到明显改善。试验结果还表明,在聚丙烯酸盐修复的Cd污染土壤上,2个月的生长期间,高粱植株吸收Cd量约占土壤有效Cd总量的6%,因此,高粱可用于污染土壤Cd的植物提取。(四)通过盆栽试验研究了不同水平的聚丙烯酸盐对重金属污染矿区土壤的修复作用,结果表明聚丙烯酸盐的应用提高了矿区污染土壤的持水能力,尽管这种持水能力随着聚丙烯酸盐对重金属的吸附而逐渐下降,其在植株生长期间对植株水分的供应是植株生长得到改善的主要原因之一。不同水平的聚丙烯酸盐(0.2%、0.4%、0.6%)对黑麦草的生长均起到了显著的促进作用,土壤中的有效铅含量显著下降,除土壤脲酶活性随着聚丙烯酸盐水平的增加而降低外,土壤其他酶活性均得到显著改善。应用主成分分析的结果表明,0.2-0.4%水平的聚丙烯酸盐体现了最佳的改善效果。(五)通过盆栽试验研究了聚丙烯酸盐改善植株生长的机理,研究结果表明,在非污染土壤上,聚丙烯酸盐上携带的养分离子如NH4+和K+是促进多年生黑麦草生长的主要原因之一。而在长期重金属污染的矿区土壤上,聚丙烯酸盐的使用显著改善了污染土壤上植株的生长并降低多年生黑麦草植株体内重金属的含量。其作用机理主要是通过聚丙烯酸盐本身携带的养分及其对水分和重金属的吸附形成了一个有益于植物根系生长和微生物活动的微环境,即丰富的水分含量和养分供应及较低的重金属含量。而半野外试验(Semi-field experiment)结果表明聚丙烯酸盐对4种不同污染矿区本地植物的生长和土壤酶活性均起到了显著的促进作用。不同植株的生长和土壤pH与土壤酶活性存在显著的相关关系。不同植株对不同生长季节反映不同,其中C.fasciculatus和S.Purpurea因其在秋冬季节生长较好,可尝试用于矿区土壤的植被固定。(六)通过对重金属污染的矿区土壤的半野外对比试验,尿不湿中的高吸水性聚合物表现出与纯聚丙烯酸盐相似的修复作用。与对照和直接使用尿不湿碎片处理相比,应用纯的聚丙烯酸盐或自尿不湿中提取的聚丙烯酸盐处理,的植株生长及植株覆盖速度明显提高,因此回收尿不湿中的高吸水性聚合物可以显著降低聚丙烯酸盐修复重金属污染土壤的成本。但将尿布湿粉碎后直接应用对土壤的性质及作物生长有一定的影响。这可能是由于其中含有大量的塑料和纤维所造成的。(七)通过盆栽实验,研究了不同用量的城市垃圾堆肥和植株类型对重金属矿区尾矿上发育的土壤的酶活性的影响。城市垃圾堆肥的应用提高了土壤pH,并为植株生长提供养分,从而促进了D.glomerata和E.australis植株生长,改善了土壤酶的活性。其中,与没有植株生长和E.australis生长的土壤相比,有D.glomerata的生长土壤上磷酸酶、蔗糖酶和纤维素酶的活性最高。在使用堆肥的土壤上,E.australia的生长提高了土壤蛋白酶和纤维素酶的活性,但抑制了脱氢酶、磷酸酶和蔗糖酶的活性。这可能是由于其根系分泌的酚类化合物的作用。两种植株在重金属污染土壤上应用各有利弊,其中D.glomerata代表一种快速生长且生物量较高,对土壤养分的需求较大的引进植株,而E.australis则代表一种生长缓慢,生物量低,但可以在养分匮乏的土壤上存活的本地植株。(八)通过盆栽试验研究了应用0.4%的聚丙烯酸盐、城市垃圾堆肥或者两者配合配合使用对长期重金属污染的矿区土壤的修复作用。在没有植株生长的情况下,两者配合使用的土壤蛋白酶、酸性磷酸酶和蔗糖酶活性最大：而在单独使用聚丙烯酸盐和堆肥的土壤上纤维素酶活性和土壤微生物基础呼吸结果相近；使用堆肥使土壤脱氢酶活性改善最显著；相反脲酶活性则因两种物质的使用而受到抑制。在有植株生长的情况下,两种物质配合使用的土壤蛋白酶、蔗糖酶、纤维素酶活性和土壤基础呼吸最高,；而最大的酸性磷酸酶活性则出现在只有聚丙烯酸盐的处理上,脱氢酶活性则出现在只有堆肥的处理中。经过修复物处理的土壤上,植株生长均获得显著改善,最显著仍旧出现在两种物质配合使用的处理上。但是,不同植株对不同修复物反应不同,其中B.maxima在堆肥和聚丙烯酸盐配合的处理上生物量最大,而C.fasciculatus在单独使用堆肥的处理上生长最好,S.purpurea则对单独使用聚丙烯酸盐的处理反应明显。(九)我们研究了聚丙烯酸盐在砂质土壤中被淋移的可能性。在长达2个月的模拟酸雨淋溶条件下,没有吸附铜离子的聚丙烯酸盐由于吸附了大量的水分而完全没有产生移动；吸附铜的聚丙烯酸盐的绝大多数也停留在原来的位置上,只有极少量的(约0.01%)的聚丙烯酸盐可能沿着土壤的大孔隙向下移动,移动距离没有超过5cm。试验结果表明,聚丙烯酸盐在吸附重金属后在土壤中是比较稳定的。更多还原

【Abstract】 Soil contamination with heavy metals has toxic effects on plants and soil organisms, and it also presents a serious threat to ecosystem and human health. As the contaminated area is larger, the in situ remediation technologies are considered. The culturing experiment in water or salt solution, pot experiment and semi-field experiment were carried out to study the effect of insoluble polyacrylate polymers or polymers from diappers on adsorption of heavy metals in the solutions and remediation of artificially and long-term contaminated soil with heavy metals. Meanwhile, the effect of compost solely or together with polymers on remediation of contaminated mine soil was also presented in this thesis. The results got from following studies supply a gap for the application of polyacrylate polymers on remediation of heavy metal contaminated soil. Moreover, they also provide the experimental information about application of municipal waste such as the compost and used diapers. The results showed that:(一) The adsorption of metals by polyacrylate polymer and the effects of polyacrylate polymer on artificially contaminated soil with Cd were studied. At the temperature of 25℃,The heavy metals in the solutions were adsorbed rapidly by the polyacrylate polymer and very stable during 120d’s soaping. The amount of absorption to the heavy metal was highest and stable at the pH 4.5-6.5. The bond of polyacrylate polymer with ions of heavy metals was much more stronger than ammonium acetate, slightly higherer than citric acid, and was similar to EDTA. In the soil pot experiment, the growth of ryegrass was enhanced even in the highest Cd level by application of polyacrylate polymer as compared with that of control, and the concentration of Cd in ryegrass shoot was decreased significantly, the water soluble Cd of soil was reduced remarkably as well. The results also indicated the 0.1% of polyacrylate polmers in this experiment should be reasonable.(二) The effects of polyacrylate polymer on remediation of artificially contaminated soil with Zn, Cu and Cd solely or together were studied. The application of polymer resulted in greater growth of ryegrass, significant reduction of concentration of heavy metals in ryegrass and soil in the contaminated soil with metals solely or together. The competition between metals caused differences in the concentration of metals in ryegrass and soil in the muti-metal contaminated soil.(三) We investigated the application of insoluble polyacrylate polymers to improve soil and plant health. Sorghum was grown in a Cd-contaminated sandy soil. Polyacrylate polymers at 0.2% (w/w) were added to half of the soil. Control soil without plants was also included in the experiment. Growth of sorghum was stimulated in the polymer-amended soil. The concentration of Cd in the shoots, and the activities of catalase and ascorbate peroxidase decreased in plants from polymer-amended soil compared with unamended control. The amount of CaCl2-extractable Cd in the polymer-amended soil was 55% of that in the unamended soil. The activities of soil acid phosphatase,β-glucosidase, urease, protease and cellulase were greatest in polymer-amended soil with sorghum. In conclusion, the application of polyacrylate polymers to reduce the bioavailable Cd pool seems a promising method to enhance productivity and health of plants grown on Cd-contaminated soils. The plant of sorghum could be used for the phytoextraction of Cd in this experiment.(四) We investigated the effects of different application rates of insoluble hydrophilic polyacrylate polymers on plant growth and soil quality from a Pb-contaminated mine soil. The polymer increased the waterholding capacity of the soil from about 250 g/kg in unamended soil to almost 1000 g/kg in soil with 0.6% polymer. However, the capacity of the polymer to retain water decreased progressively, presumably as the polymer sorbed Pb. Growth of orchardgrass (Dactylis glomerata L. cv. Amba) was stimulated in the polymer-amended soil. The greatest accumulated biomass over four cuts was obtained in soil amended with 0.4% of polymer. After orchardgrass had been growing for 101 days, the amounts of CaC12-extractable Pb present in the polymer-amended soil were 15-66% of those in the unamended soil, depending on polymer application rate. The number of bacteria culturable on agar enriched with ’Nutrient’ and yeast extract, and the activities of dehydrogenase, phosphatase, b-glucosidase, protease and cellulase increased following polymer application. In contrast, urease activity was impaired by polymer application, presumably due to the presence of ammonium as a counter ion. Principal component analysis was used to compare the effects of the different rates of polymer application. Overall, the application of 0.2 or 0.4% polymer resulted in closer values for the indicators of soil quality used than the treatment with 0.6% polymer.(五) We evaluated the use of polyacrylate polymers to aid phytostabilization of mine soil. In a pot experiment, perennial ryegrass was grown in a mine soil and in uncontaminated soil.Growth was stimulated in the polymer-amended mine soil compared with an unamended control, and water-extractable levels of soil Cu and Zn decreased after polymer application.In an experiment performed in six 60-cm-diameter cylinders filled with fertilized mine soil, polymers were applied to three cylinders, with the remainder used as unamended control. Total biomass produced by indigenous plant species sown in polymer-amended soil was 1.8 (Spring-Summer) or 2.4 times (Fall-Winter) greater than that of plants from unamended soil. The application of polymers to the mine soil led to the greatest activity of soil enzymes. Soil pH, biomass of Spergularia purpurea and Chaetopogon fasciculatus, and activities of protease and cellulase had large loadings on principal component (PC)1, whereas growth of Briza maxima and the activities of urease, acid phosphatase, andβ-glucosidase had large loadings on PC2. The treatments corresponding to controls were located on the negative side of PC1 and PC2. Amended treatments were on the positive side of PC2 (Spring-Summer) or on the positive side of PC1 (Fall-Winter), demonstrating differential responses of plants and soil parameters in the two growth cycles.(六) We used hydrophilic polymers from diapers to aid establishment of an indigenous plant(Spergularia Purpurea) in a soil from a pyrite mine. The establishment of a plant cover was faster in soil amended with polymer from diapers, and at the end of the experiment (85 days after sowing) the soil was completely covered in all treatments except unamended control. Total biomass in polymer-amended soil was about four to five times greater than that of plants from unamended soil. The concentrations of trace elements in plant shoots decreased in amended soil. The activities of soil acid phosphatase, -glucosidase, protease and cellulase were greatest in soil amended with the polyacrylate polymer or with polymer removed from diapers, while the application of shredded diapers lead to values that were in general intermediate between these treatments and unamended control. Basal and substrate-induced respirations, and dehydrogenase (related to microbial activity) were greatest in soil amended with polymers, but the presence of a plastic film and fibrous materials from shredded diapers prevented any improvement in these parameters compared with unamended soil. In conclusion, hydrophilic polymers from diapers can be used to promote a vegetation cover in pyrite mine soils and improve soil hydrolytic enzymatic activities, although studies are still 39 needed to treat diapers and decrease the toxicity towards soil microorganisms associated with some of the materials present in disposable diapers.(七) We applied three doses of compost from mixed municipal solid waste (0、15、30 g kg-1 of soil) to a soil developed from pyrite mine wastes. Compost application to bare soil increased pH, provided plant nutrients, and enhanced the activity of soil enzymes tested. Growth of D. glomerata and E. australis was stimulated in compost-amended soil compared with unamended controls. The presence of D. glomerata led to the greatest activities of soil acid phosphatase,β-glucosidase and cellulase compared with bare soil or with soil with E. australis. The presence of E. australis increased the activities of protease and cellulase in amended soil, compared with control, but it impaired dehydrogenase,β-glucosidase and acid phosphatase activities. These negative impacts probably derived from phenolic compounds known to be released from roots of this species. The survival strategy of this species seems to include a small need for P in the shoots and the release of exudates that impair microbial activity and P cycling.(八) We tested the application of compost and polyacrylate polymers to promote the growth of indigenous plant species present in the mine area. In the absence of plants, the greatest improvements in soil conditions were obtained by the application of both polymer and compost, which was associated with the greatest values of protease, acid phosphatase, andβ-glucosidase, whereas the activity of cellulase and microbial respiration were similar in soil amended with compost or polymer. Dehydrogenase activity was greatest in soil with compost (with or without polymer), whereas urease activity was impaired by both amendments. In the presence of plants, the application of both amendments led to the greatest activities of protease, urease,β-glucosidase, cellulase, and microbial respiration, but acid phosphatase was mainly enhanced by polymer and dehydrogenase was increased by compost. Plant growth was stimulated in all treatments compared with unamended soil, but the greatest value for total accumulated biomass was obtained in fertilized soil receiving both amendments. However, species responded differently to treatment: while the growth of B. maxima was greatest in soil with compost and polymer, the growth of C. fasciculatus responded better to soil with compost, and S. purpurea grew better in polymer-amended soil. The amendments tested improved the quality of a mine soil and stimulated plant growth. However, botanical composition likely changes over time with amendments, and this needs to be considered when a large scale application of amendments is projected.(九) The risk of downward movement of polymers in columns of a sandy soil was studied. Hydrophilic polymers from diapers with or without Cu were placed at a 10 cm-depth in the soil. Five leaching cycles with artificial rain took place and leachates were analyzed for organic matter (OM) and Cu. At the end of the experiment, the soil columns were sliced and each layer analyzed separately. The results showed that leaching of OM and Cu took place, albeit from mobile fractions in the soil. Some repacking of soil and polymer particles took place, but there was no indication that polymers moved to any great depth in soil columns.更多还原