重金属污染土壤间作修复的研究进展

种植单一的超富集植物修复重金属污染土壤,不但中断农业生产导致经济收益降低,而且因生物量较低、修复周期长等诸多弊端导致修复效果不甚理想。间作作为一种传统的农艺管理方式,利用生态位和生物多样性原理等能提高农作物对资源的有效利用,对共植的农作物种类增量提质。在中、轻度污染土壤修复中利用间作体系,通过调控超富集植物与农作物的生长发育,促进超富集植物根系低分子量有机酸(LMWOAs)的分泌,降低其根际土壤p H,增加重金属活性,从而增加超富集植物对重金属的吸收,同时抑制农作物根系LMWOAs的分泌,以减少农作物对重金属的吸收,提高其产量和品质,实现"边生产边修复",提高土地利用率,并增加经济效益。本文根据近几年来国内外相关文献,综述了间作条件下超富集植物和农作物生物量、生理生化响应、重金属吸收、转运、富集等方面的变化,以及间作对土壤环境质量的影响,并对间作修复重金属污染土壤领域的发展趋势,如超富集植物和农作物间作的信号转导和分子生物学机制、间作体系下两类植物根际微生物类群的差异及其功能机制,以及构建高效间作体系提高重金属污染土壤的修复效率等方面进行了展望。     

铅污染土壤的植物修复研究进展

利用植物修复技术对土壤重金属污染进行治理是目前国内外有关学者研究的热点和难点问题。本文系统地阐述了重金属Pb污染土壤的植物修复,从Pb超富集植物、植物吸收累积Pb的机制和影响因素以及螯合剂在Pb污染土壤植物修复中的作用等几方面介绍了国内外的有关研究现状及其发展趋势。     

铀对植物的胁迫效应研究进展

铀是一种具有较高化学毒性的放射性核素。铀矿开采、核事故泄露、核废物的不恰当处理等会对周围土壤造成放射性污染。植物体内富集的铀可通过食物链进入人体,从而对人体健康造成伤害。国内外学者针对铀污染土壤的植物修复技术开展了一系列研究工作。本研究系统地总结了铀对植物胁迫效应的研究进展,主要包括铀对植物生长发育、生理生化、基因毒害、水分代谢和营养代谢等方面的影响。并结合当前研究现状,对未来的研究方向进行了展望。本研究结果为进一步阐释富集植物对铀的吸收和转运机制,以及铀污染土壤的植物修复提供了理论依据,对于监测治理铀污染土壤和保护生态环境具有重要意义。     

丛枝菌根真菌在植物修复重金属污染土壤中的作用

菌根是真菌与植物根系所建立的互惠共生体,其中以丛枝菌根(AM)真菌在自然界中分布最广。在重金属污染条件下,AM真菌可以减轻重金属对植物的毒害,影响植物对重金属的吸收和转运,在重金属污染土壤的植物修复中显示出极大的应用潜力。文章通过讨论菌根植物对重金属修复的作用机制,提出菌根技术在重金属植物修复中应在通过广泛调查、筛选超积累植物的基础上,不断探索植物-菌根体系修复问题,以促进重金属污染土壤的生物修复。     

砷污染土壤的蜈蚣草修复研究进展

本文评述了As污染土壤的蜈蚣草植物修复及其对As的解毒机制的研究进展,内容着重包括蜈蚣草对As的富集特征,As在蜈蚣草中的赋存形态、迁移及其转化,土壤以及土壤中P、Ca和K等元素对蜈蚣草吸收、转运As的影响等方面。     

植物–微生物联合修复镍污染土壤研究进展

土壤健康是粮食安全的保障,人类活动给土壤造成的污染亟待治理。镍是人体必需微量元素,但过量的镍具有较大的毒性。目前我国土壤中镍污染比较严峻,应尽快响应《土壤污染防治行动计划》来改善土壤中镍污染状况。本文综述了植物–微生物联合修复技术的基本原理,微生物在镍污染土壤中对植物生长状况、有效态镍含量以及植物吸收镍的影响,对寻找合适的植物和微生物修复镍污染土壤具有重要意义;最后,提出将有机酸运用到植物–微生物联合修复镍污染土壤中、建立PGPB库和寻找我国超富集植物等下一步研究的重点。     

砷污染土壤的生物修复研究进展

土壤As污染已是全球性问题,我国也不例外,对As污染土壤的生物修复已是研究热点,但相关机理仍不完全清楚.本文综述了国内外微生物、蚯蚓、植物在As污染土壤中吸收转化As及其解As毒机理,以及微生物-植物复合系统修复As污染土壤方面实验室内研究情况.目前广泛认为植物修复土壤重金属/非金属污染较有应用前景,可限于甚至是使用超富集植物单一作用下仍有较多缺陷,如通过微生物技术及蚯蚓调节根际微生态,以利于植物在污染土壤中存活或/和吸收更多的As,将极具应用前景.     

间作条件下超积累和非超积累植物对重金属镉的积累研究

通过温室盆栽试验,研究了超积累植物龙葵、非超积累植物黑麦草、苋菜分别与玉米间作条件下对重金属Cd的积累特性。结果表明,几种间作作物中地上部生物量最大的是龙葵,其次是苋菜,最小的是黑麦草,其中土壤Cd浓度为1.59 mg/kg时,龙葵地上部生物量分别是苋菜、黑麦草的2.41、10.6倍;土壤Cd浓度为1.92 mg/kg时,龙葵地上部生物量分别是苋菜、黑麦草的2.42、9.06倍,3种富集植物地上部生物量的差异达到显著水平。玉米间作条件下超积累植物龙葵各器官中Cd含量表现为叶茎籽粒根,即地上部大于根部;而苋菜中Cd含量表现为根茎叶,黑麦草中Cd含量表现为根部地上部,即非超积累植物Cd含量为根部大于地上部。土壤中Cd含量为1.59 mg/kg时,龙葵地上部Cd累积量分别为苋菜、黑麦草的28.0、59.9倍;龙葵的富集系数是苋菜、黑麦草的28.2、59.3倍,转运系数分别是苋菜、黑麦草的8.08、55.9倍。土壤中Cd含量为1.92 mg/kg时,龙葵地上部Cd累积量分别为苋菜、黑麦草的30.8、43.5倍;龙葵的富集系数分别是苋菜、黑麦草的29.4、41.4倍,转运系数分别是苋菜、黑麦草的7.98、53.6倍。综上可知,超积累植物龙葵对土壤中Cd的吸收与转运能力远远大于非超积累植物苋菜、黑麦草,龙葵是最理想的与玉米间作的Cd污染土壤修复的植物修复材料。     

3种植物对红壤中镉的富集特性研究

重金属超富集植物是重金属污染土壤植物修复的基础,研究了3种重金属富集植物羽叶鬼针草、美洲商陆和紫叶芥菜对重金属Cd的吸收积累规律,为植物修复Cd污染的农田和生态环境建设提供科学依据。采用盆栽方法,在不同浓度（0、20、35、50、65、80mg·kg^-1）Cd处理下,分别测定3种植物地上部与根部Cd的含量,计算了地上部Cd迁移量、根系耐性指数、富集系数,研究了土壤中Cd添加量与植物富集Cd量的相关性。结果表明,随着土壤中Cd离子浓度的升高,3种植物地上部和根系中的Cd含量也在增加,相关系数都大于0．99;综合地上部与根部Cd含量,地上部Cd迁移量,根系耐性指数和富集系数,3种植物对Cd的富集能力的相对顺序为：羽叶鬼针草〉美洲商陆〉紫叶芥菜。羽叶鬼针草、美洲商陆种植在Cd处理浓度为65mg·kg^-1的土壤中和紫叶芥菜种植在Cd处理浓度为80mg·kg^-1的土壤中栽培时,3种植物地上部与根部的Cd含量均超过了100mg·kg^-1,达到了Cd超富集量的标准。羽叶鬼针草、美洲商陆和紫叶芥菜对Cd有很强的耐受性和富集性,可以作为先锋植物去修复被Cd污染的土壤。     

丛枝菌根真菌在植物修复砷污染土壤中的作用

丛枝菌根真菌能增强植物对矿质元素的吸收、提高植物的抗逆性、增强抗病性、改善植物根际微环境,减轻重金属对植物的毒害,影响植物对重金属的吸收和转运,在重金属污染土壤的植物修复中显示出极大的应用潜力。近年来,As污染已成为全球非常突出且急需解决的环境问题之一,对As污染土壤的生物修复也因而成为研究热点。本文主要从丛枝菌根真菌改变土壤pH和酶活性、增强植物对As的耐性和影响植物对As的吸收方面综述了丛枝菌根在As污染土壤修复中应用的研究进展,揭示出菌根应用在As污染土壤中的作用潜力和研究方向。     

Accumulation and Fractionation of Rare Earth Elements in a Soil-Wheat System

Time series bioaccumulation of rare earth elements (REEs) in field-grown wheat with and without a dressing of extraneous REE fertilizer at different growth stages and fractionation of REEs during their transport in a soil-wheat system were determined. Time-dependent accumulation of extraneous REEs was found in different parts of wheat. An upward transport of extraneous REEs from roots to shoots under a soil dressing and a downward transport from leaves to roots with a foliar dressing were also observed. Moreover, fractionation of REEs occurred in the soil-wheat system. Compared to the host soil a positive Eu anomaly in the stems and grains as well as heavy REE enrichment in the grains were found. The ability of the different wheat organs to fractionate Eu from the REE series was ranked in the order of stems ≥ grains > leaves > roots.     

Distribution and provenance implication of rare earth elements and Sr-Nd isotopes in surface sediments of Jiulong River,Southeast China

Purpose

The purposes of this paper are to investigate the geochemical characteristics of rare earth elements (REEs) in the surface sediments of Jiulong River, southeast China, to probe the provenance compositions of the sediments, and to analyze the potential anthropogenic influence on REEs in the sediments. REEs and Sr-Nd isotopes were selected as the tools because REEs can be used to identify the anthropogenic effects on sediments and Sr-Nd isotopes have been widely known as powerful tracers for provenance analysis.

Materials and methods

Fifty-three samples of surface sediments (0~5 cm) were collected from Jiulong River. The concentrations of REEs and Sr-Nd isotopic compositions in the surface sediments were determined by inductively coupled plasma mass spectrometry (ICP-MS) and thermal ionization mass spectrometry (TIMS), respectively. The chondrite-normalized and WRAS-normalized REEs patterns, enrichment factor, plots of La-Th-Sc and La/Yb-∑REE, and plots of ε_Nd(0) vs ⁸⁷Sr/⁸⁶Sr and ε_Nd(0) vs δEu are presented.

Results and discussion

The mean concentration of ΣREEs in the surface sediments of Jiulong River was 254.25 mg kg^?1. The mean values of ΣLREEs (227.6 mg kg^?1), ΣHREEs (26.64 mg kg^?1), and (La/Yb)_N ratios (9.24) suggested an enrichment of LREEs compared to HREEs. Negative Eu anomalies were observed in the surface sediments. The distribution patterns of REEs in the surface sediments from different areas of Jiulong River were remarkably similar. The values of ⁸⁷Sr/⁸⁶Sr, ¹⁴³Nd/¹⁴⁴Nd, and ε_Nd(0) were 0.714091~0.733476, 0.511875~0.512271, and ??14.88~??7.16, respectively. The plots of ε_Nd(0) vs ⁸⁷Sr/⁸⁶Sr, ε_Nd(0) vs 1/[Nd], and ε_Nd(0) vs δEu indicated that the sediments in Jiulong River were mainly derived from natural geological processes and the REEs might be also influenced by anthropogenic activities such as Fujian Pb-Zn deposit, coal ash, and industrial sludge.

Conclusions

The REEs in the surface sediments at different sites are similar in geochemical characteristics, with a right-inclined distribution pattern and higher enrichment of light REEs (LREEs) compared to heavy REEs (HREEs), and a negative Eu anomaly but no evidence of Ce anomaly. The sediments in Jiulong River were mainly derived from natural geological processes (granite and magmatic rocks), and the REEs in the sediments were also influenced by anthropogenic activities (Fujian Pb-Zn deposit, coal ash, and industrial sludge).

     

Arsenic Uptake by Two Hyperaccumulator Ferns from Four Arsenic Contaminated Soils

A greenhouse study was conducted to evaluate and compare arsenic accumulation from four arsenic contaminated soils by two arsenic hyperaccumulators, Pteris vittata and Pteris cretica. After growing in soils for six weeks, the plants were harvested and separated into above- and below-ground biomass. Total As, P, Ca, K, glutathione and biomass were measured for the plants, and total As, Mehlich-3 P and As, exchangeable K and Ca, and arsenic fractionation were performed for the soils. Pteris vittata had significantly higher total biomass (14 g/plant) and As accumulation than P. cretica. Arsenic accumulation in both ferns followed the arsenic concentrations in the soil. The P/As molar ratio in the fronds, growing in arsenic contaminated soils, ranged from 80 to 939 in P. vittata and 130 to 421 in P. cretica. Plant arsenic concentrations were significantly positively correlated with Mehlich-3 arsenic in the soils. Soil pH was also significantly correlated with Mehlich-3 arsenic before and after plant uptake. Plant As uptake was significantly correlated with exchangeable potassium in the soil before plant uptake. Glutathione availability was not implicated as a major detoxification mechanism in these ferns. Though both plants were effective in taking up arsenic from various arsenic contaminated soils, P. vittata was overall a better candidate for phytoremediation of arsenic contaminated soils.     

植物对重金属镉的吸收转运和累积机制

Cd是土壤污染的主要因素之一,痕量的Cd2 不仅对植物生长有毒害作用,同时对人体健康产生极大的危害.研究植物如何从土壤中吸收Cd2 ,并在整个植物体内运输和积累的机理,对开发植物修复技术及生态环境的恢复具有重要意义.近年研究表明:土壤微环境影响植物对Cd2 的吸收;植物根细胞壁通过选择性吸收可以吸附和固定土壤中的Cd2 ,其中大部分Cd2 被截留在细胞壁中,其余的则通过协助扩散或主动运输等方式透过细胞膜进入根细胞中;在根细胞中Cd部分累积在液泡中,部分则通过木质部运输到地上部分;茎叶部的大部分Cd2 通过络合作用被固定在液泡中,少量被截留在细胞壁和细胞质中.在植物结实期,Cd通过韧皮部进入籽实中,而籽粒中的Cd几乎不能运输到其他部分,主要通过食物链进入动物和人体中.本文综述了植物对Cd的吸收和运输机制方面的研究进展.     

Examination of Correlation between Histidine,Sulfur, Cadmium,and Cobalt Absorption by Morus L., Robinia pseudoacacia L., and Populus nigra L.

We investigated the relationship between histidine, sulfur (S), cadmium (Cd), and cobalt (Co) in three hyperaccumulating plants, namely Morus L., Robinia pseudoacacia L., and Populus nigra L. The samples were collected around Gaziantep and Bursa cities because these two cities have more than 1,500,000 populations, in Turkey, as well as they are highly industrialized. Analyses for Cd, Co, and S were done by inductively coupled plasma mass spectrometer (ICP-MS) and for histidine by high-performance liquid chromatography-mass spectrometer (HPLC-MS). Related with role of histidine in detoxification, it was considered that histidine did not bind nickel (Ni) directly in the cytoplasm, but in transport vesicles because metal-rich vesicles had been observed in the cytoplasm of cells of hyperaccumulator plants. The linear correlations were r_his-Cd = 0.70 and r_his-Co = 0.74 for P. nigra L., r_his-Co = 0.52 and r_Co-S = 0.76 for R. pseudoacacia L. It was concluded that P. nigra L. leaves can be considered as hyperaccumulators.     

Lead uptake,distribution, and remobilization in cucumber

Mobility and distribution of lead (Pb) were investigated in cucumber (Cucumis sativus L.) grown in solution culture. Based on the observation that Pb uptake is influenced by the chemical form of iron (Fe) (complexed or ionic) in the solution, Fe distribution was also determined. Iron concentration was even in the stem (separated to internodes) and petioles but slightly increased at the shoot tip while Pb concentration decreased upwards. In the leaves Fe concentration decreased upwards (whereas in the control it increased a little at the youngest leaves) while Pb concentration increased to the largest leaves then decreased towards the shoot tip. It is suggested that the distribution of Pb in cucumber is passive process and it accumulates in the apoplast while Fe distribution is determined by the requirements of synthetic processes in young or photosynthesizing tissues. Lead probably lowers Fe transport into the symplast in the leaves causing slight chlorosis at the youngest leaves. In the plants that were loaded with Pb, decapitated and rooted again in Pb‐free culture solution we found no significant remobilization of Pb which supports that Pb binds strongly to the binding sites in the apoplast or is detoxified in an immobile form.     

Soil‐plant relationships,micronutrient contents,and cardenolide production in natural populations of Digitalis obscura

The production of secondary metabolites by plants growing in natural populations is conditioned by environmental factors. In the present study, we have investigated the relationships among soil properties, micronutrients in soils and plants, and cardenolide production from wild Digitalis obscura (Scrophulariaceae) populations. Young and mature leaves and soil samples were collected in ten different populations, corresponding to three Mediterranean bioclimatic belts (Thermo‐, Meso‐, and Supramediterranean belts). Soil (total and EDTA‐extractable) and leaf micronutrients (Fe, Mn, Zn, and Cu), and leaf cardenolide accumulation have been determined. Significant negative correlations were observed between Fe, Mn or Zn concentration in leaves and soil pH, as well as between Fe or Mn in leaves and carbonate content of soils. Only EDTA‐extractable Mn was significantly correlated with Mn content in the plants. With regard to cardenolide content in leaves, this parameter was negatively correlated with Zn_leaf in young leaves and with Mn_leaf in old leaves. Positively correlated, however, were Fe and cardenolide content in young leaves. The influence of environmental conditions and leaf micronutrient contents on cardenolide accumulation is discussed.     

氮素形态和韧皮部烫伤对玉米韧皮部铁运输的影响

用营养液培养方法研究了在不同供铁条件下不同形态N和韧皮部烫伤对玉米苗期韧皮部Fe运输的影响。结果表明,韧皮部烫伤提高了玉米根系Fe的再利用,降低了初生叶中Fe的再利用,尤其在缺Fe条件下这种作用更明显,提高和降低的幅度更大。韧皮部烫伤还降低了伤流总量,增加了Fe的浓度。在供应铵态N的条件下,Fe的韧皮部运输比供应硝态N条件下有显著增加,Fe的再利用明显提高。     

Quantification of zinc transport via the phloem to the grain in rice plants (Oryza sativa L.) at early grain-filling by a combination of mathematical modeling and 65Zn tracing

Zinc (Zn) is an essential nutrient for human beings, and most Zn intake occurs through vegetables or cereals such as rice (Oryza sativa L.) grains. Recently, we detected Zn as well as cadmium, which may be partitioned to rice grains, in the phloem saps from the uppermost internodes of rice and in the xylem saps from the cut stems at early grain-filling. To quantify Zn transport to the grains via the phloem and xylem, a mathematical model previously developed for cadmium transport to rice grains was applied. We examined the translocation of zinc into the grains of rice plants at early grain-filling by feeding zinc-65 (⁶⁵Zn) via a root-bathing medium, through culm cuts above and below the flag-leaf nodes, and through the flag leaves. The estimate made using the mathematical model and experimental data for three types of ⁶⁵Zn transport suggests that the grain Zn may be accumulated predominantly via the phloem through two means of transport, phloem transport of stored Zn from the leaves and, more importantly, xylem-to-phloem transfer at the nodes from Zn as it is being absorbed. The Zn transport via the phloem to the grains is more selective than that of cadmium, a non-nutrient element, as also evidenced by the greater transport of cadmium to the glumes via the xylem.     

Field Trials for in Situ Decontamination of Heavy Metal Polluted Soils using Crops of Metal-Accumulating Plants

Certain wild plants as well as crop plants, so-called hyperaccumulators, are able to accumulate large amounts of heavy metals in aerial parts. This property may be exploited for the clean-up of soil contaminated by metals (phytoremediation), if the yield and metal accumulation are big enough to finish remediation within a reasonable period (e.g. five years). Therefore, the ability of various plants to accumulate zinc and cadmium were compared in field trials. The wild species Thlaspi caerulescens and Alyssum murale as well as the tree Salix viminalis showed a strong ability to accumulate zinc and cadmium. However, phytoremediation of investigated soils contaminated with cadmium (6.6 ppm) or zinc (810 ppm) lasts too long based on present technology. Literature data and preliminary experiments indicate that major obstacles could be overcome: Yield and metal-uptake rates have to be increased dramatically in order to allow remediation within reasonable periods.