重金属污染土壤生态修复的芦竹适应机制研究

Heavy metals contamination of soil from the vicinity of nonferrous mining and smelting regions is serious and huge, and ecoremediation of metal-contaminated soils is critical for metals contamination complex control in our country. In the proposal, the adaptability mechanisms of giant reed for soil ecoremediation system contaminated with arsenic, cadmium and lead should be studied. The contents and objectives of the project are as follows: Firstly, the physiological characteristics responses of giant reed phenotypes from the vicinity of non-ferrous mining and smelting areas in Southern China should be investigated. Secondly, restardation or induction mechanisms of heavy metals transferred from root zone to plant by organic acid in exudates from giant reed's roots should be studied under greenhouse conditions, which organic acid in exudates should be extracted with dialysis and then analyzed using HPLC technique. And, the stress responses of giant reed for heavy metals in soils should be studied through SEM/EDX, XRD and SR-EXAFS images of giant reed roots and shoots, such as cell wall, cell membrane and vacuole membrane of roots, and exudates in the inner side of fibro-vascular bundle of shoots while the form speciations and locking areas characteristics of As, Cd and Pb in roots should be determined, respectively. Finally, through field experiments, the structural and functional diversity of microbial communities in root zone soils should be determined by PCR-DGGE fingerprinting while arbuscular mycorrhizal fungi should be cultured in order to improve the ecological stability of giant reed ecoremediation system and serve for the ecological engineering of metals- contaminated soils from the vicinity of non-ferrous mining and smelting areas.

有色金属矿冶区重金属污染土壤面广量大，开展重金属污染土壤生态修复是国家重金属污染综合防治的重大需求之一。本研究以砷镉铅污染土壤芦竹生态修复为对象，通过野外调查，研究我国南方有色金属矿冶区芦竹生态型的生理特性响应机制；通过温室盆栽试验，采用透析法提取根系有机酸分泌物，结合HPLC技术，探讨芦竹根系有机酸分泌物对根区重金属进入芦竹体内的截留/诱导机制；采用SEM/EDX、XRD和SR-EXAFS技术，研究芦竹根细胞壁、细胞膜、液泡膜等亚细胞组织结构、芦竹茎维管束内腔分泌物对根区重金属的响应特征,以及芦竹根中As、Cd、Pb化学形态及其区室化特征，揭示芦竹应答根区重金属的抗性机制；通过田间试验，采用PCR-DGGE技术研究根区土壤中微生物的群落结构与功能多样性，研究丛枝菌根真菌对芦竹修复体系生态稳定性的促进作用机制，为有色金属矿冶区重金属污染土壤生态修复提供科学理论依据。

本项目系统研究了芦竹对土壤中As，Cd和Pb等重金属的适应机制以及对污染土壤的修复作用。在我国南方典型有色金属矿冶区野外调查结果表明，芦竹生态型分布广泛，逆境适应能力强；可以提高污染土壤中脲酶、脱氢酶和蔗糖酶活性，改善土壤微生物群落特征。.田间长期定位试验表明，单施有机肥或同时施用有机肥和粉煤灰，土壤中有效态As和Pb分别从8.45%和29.6%降低至2.19% 和13.5%，有效态Cd从25.3% 降低至6.49%。芦竹明显改良土壤中微生物脲酶，蔗糖酶和脱氢酶活性，活力分别达到了358 NH4-Nμg/g•d，777 glucose mg/g•d和178 TPF μg/g•d。As，Cd和Pb通过芦竹体内COO-，羰基以及Me2+-CH2-CH3等结合从地下部运移地上部。SOD是芦竹抗氧化作用的主要途径，过氧化物在谷胱甘肽循环中通过GSH氧化成GSSG得到还原。同时施用有机肥和粉煤灰，芦竹生物量，芦竹地下部As，Cd和Pb累积量增加；土壤中脱氢酶活性、微生物条带数和微生物多样性指数明显增加。.野外长期修复结果表明，污染土壤上芦竹中As，Cd和Pb主要累积在根系。根部Cd与Pb含量存在显著相关性（p<0.05）。根部重金属主要沉积在芦竹根表铁膜中。芦竹显著降低了土壤中酸提取态Cd对土壤微生物群落的影响。.盆栽试验结果表明，污染土壤上芦竹叶片中丙二醛含量明显降低，SOD酶活性降低而CAT酶活性增强。叶片中POD酶活性的降低有利于芦竹对重金属的富集，同时GSH与氧化基团结合生成GSSG，提高了芦竹的抗氧化作用。须根为芦竹地下部Cd主要的富集部位，也是芦竹阻隔Cd向芦竹体内运移的屏障。芦竹和其他修复植物组合修复增强了芦竹对污染土壤中重金属的耐受能力；土壤中蔗糖酶、酸性磷酸酶和总磷酸酶活性得到明显改善。修复植物组合提高了土壤中微生物数量和物种多样性，尤其是芦竹与桑树或构树间种修复下土壤中微生物数量明显高于芦竹单一修复。.上述结果表明，芦竹是一种理想的生态修复先锋植物，有机肥和粉煤灰等施用可提高芦竹的生态修复效率，可用来生态修复矿冶区重金属污染土壤。