贵州独山锑矿区土壤-头花蓼系统中重金属的分布特征

通过野外调查采样,分析贵州独山锑矿区土壤6种重金属(Sb、As、Cd、Zn、Pb、Mn)含量及其在头花蓼不同部位的分布特征。结果表明:矿区土壤Sb、As、Cd、Zn、Pb和Mn的平均含量分别为1566.55、23.98、1.21、117.81、34.27和460.98 mg·kg-1,Sb、As、Cd、Zn含量分别为贵州省土壤背景值的699.35、1.20、4.88和1.18倍,且土壤中Sb与As呈显著正相关性(P0.05),具有同源性。内梅罗综合污染指数法评价表明,矿区土壤重金属污染指数为112.75~1295.22(平均500.37),为重度污染水平。头花蓼在锑矿区污染土壤中具有较强的耐受性,且Sb、Mn在头花蓼各部位的含量分布分别为根叶茎花、叶花根茎,As、Cd、Zn、Pb无明显规律。矿区头花蓼各部位的As、Cd、Pb含量均未超过《中医药-中草药重金属限量》国际标准值,但该矿区头花蓼中的Sb对人体的健康存在一定健康风险。     

贵州水银洞金矿紫茎泽兰重金属元素测定与分析

利用原子吸收法对贵州水银洞金矿紫茎泽兰及其基质中Cr、Pb、Zn、Cd、Hg和As含量进行了测定和分析。结果表明,贵州水银洞金矿废水处理区土壤Hg(12.575 mg·kg^-1)和As(501.374 mg·kg^-1)已严重超标,Hg和As的平均含量分别是国家土壤环境质量三级标准(GB15618-1995)的8.383倍和12.534倍,污染极为严重;紫茎泽兰对该矿区不同的重金属富集能力不同,尤其对该矿区Cr有较强的富集作用,具有一定的Cr污染修复潜力。紫茎泽兰对所测定的6种重金属元素的吸收转移能力有较大的差异,整个植株对Pb、Zn 和Cr具有很强的吸收转移能力。其茎、叶对不同的重金属元素的吸收转移能力也呈现出很大的差异,紫茎泽兰茎对Cr、Pb和Cd具有很强的吸收转移能力,而叶对Zn、Pb和Hg具有很强的吸收转移能力。除As外,紫茎泽兰对Cr、Pb、Zn、Cd和Hg都具有不同程度的耐受能力,对该矿区的生态恢复具有重要的作用。     

贵州木油厂汞矿区4种藓类植物及其基质中重金属元素分析

通过对贵州木油厂汞矿区4种藓类植物(真藓、卵蒴真藓、羽枝青藓和圆枝粗枝藓)及其生长基质中的Cu、Zn、Ca、Mg、Cd、Pb、Hg、As 8种元素进行测定分析,以揭示藓类植物与生长基质中重金属元素及其污染程度的关系.结果表明:(1)贵州木油厂汞矿区藓类植物生长基质中Cu、Hg和As元素的平均含量分别是相应国标值的1.29倍、300倍和1.69倍,说明该矿区已受到Cu、Hg和As的污染,且Hg污染特别严重.(2)羽枝青藓的As、Zn、Cd和Pb含量均最高,圆枝粗枝藓的Cu、Ca、Mg和Hg含量均最高,对重金属具有较强的耐受性.(3)羽枝青藓和圆枝粗枝藓对Zn均强烈富集,其富集系数分别为6.14和3.364;羽枝青藓、卵蒴真藓和真藓对Pb均强烈富集,其富集系数分别为13.769、9.547和3.004;表明羽枝青藓对Zn和Pb的富集能力最强,可用于土壤Zn和Pb的污染治理.(4)4种藓类植物对Cu 的富集系数为0.915～1.184,卵蒴真藓和圆枝粗枝藓对Hg的富集系数分别为0.542和0.682,圆枝粗枝藓对As的富集系数为0.74,均为同一水平,表明4种藓类植物可指示其生长基质中Cu、Hg和As的含量.(5)元素间的相关分析显示,木油厂汞矿的Cd和As之间呈显著负相关(P＜0.05),表明两元素间有拮抗作用.     

粤东铅锌尾矿三种优势植物对重金属的吸收和富集特性研究

为探讨铅锌矿废弃地优势植物在重金属污染土壤植物修复中的应用潜力,利用野外采样分析法,从粤东梅县丙村铅锌尾矿区采集其三种优势植物类芦、黄荆、盐肤木的根、茎、叶和土壤样品,测定和分析Pb、Zn、Cu、Cd四种重金属含量.结果表明:该矿区土壤污染严重,Pb、Zn、Cd含量远超土壤环境质量的三级标准,Cu超出二级标准;根际土壤和非根际土壤重金属含量均为Pb＞Zn＞Cu＞Cd,但根际土壤的重金属含量显著低于非根际土壤;这三种植物对Pb、Zn、Cu的转移系数大于1.0,对Cu的富集系数最高,Pb最小,但对四种重金属的富集系数均小于1.0,均未达到超富集植物临界含量标准.三种植物为该矿区的优势植物,说明它们对土壤的重金属污染有很强的耐性,虽然并非典型的超富集植物,但对污染土壤仍有较好的修复效果.     

四川甘洛铅锌矿区优势植物的重金属含量

通过野外调查采样,分析了四川凉山州甘洛县铅锌矿区土壤的重金属含量,以及矿区生长的13种优势植物对Pb、Zn、Cd、Cr、Cu的吸收与富集能力及其富集特性.结果表明,矿区土壤受Pb、Zn、Cd 3种重金属污染严重,13种植物体内的Pb含量均高于普通植物10倍以上,具有修复矿区土壤铅污染的潜力,其中植物1的转运系数和富集系数都大于1,满足Pb超富集植物的基本特征.Zn在凤尾蕨、细风轮菜、大火草、蔗茅、小飞蓬和牛茄子中含量较高.小飞蓬和紫茎泽兰的Cd含量较一般植物高出17～61倍,其中,紫茎泽兰的转运系数与富集系数均大于1,其对Cd的吸收特性值得进一步研究.     

大型水生植物对重金属的富集与转移

通过野外调查和室内分析,研究了云南阳宗海南北两区域自然生长的17种水生植物的生长状况及植物和对应水样、根区底泥中重金属(As、Zn、Cu、Cd、Pb)的含量。结果表明:植物长势良好,未发现受害症状。水体As严重污染,Pb轻度污染,Zn、Cu和Cd均未超标。9种沉水植物同时对As、Zn、Cu、Cd、Pb的富集系数(植物全株重金属含量与水中该元素含量的比值)远大于1,具有共富集特征。在平均含As0.175mg/L的水中,金鱼藻、黑藻、小眼子菜、八药水筛全株As平均含量分别为(150±7.3)、(179±35)、(92±31)、(265±21)mg/kg(干重),对As具有较强富集能力;对于8种湿生和挺水植物,北部采样点的喜旱莲子草、田栖稗、细叶小苦荬和长芒稗对As,长芒稗、细叶小苦荬、圆果雀稗、水蓼和风车草对Cd,海芋和圆果雀稗对Zn的富集系数(植物地上部重金属含量与底泥中该元素含量的比值)以及圆果雀稗对Cd和Zn转移系数(植物地上部重金属含量与根中该元素含量的比值)均大于1。聚类分析结果表明,金鱼藻、黑藻、八药水筛、小眼子菜、穗状狐尾藻5种水生植物同时对As、Zn、Cu、Cd、Pb具有较强的吸收和富集能力,在重金属复合污染水体修复中具有较大潜力。     

张家湾子金矿苔藓植物物种多样性及其对重金属污染的监测

调查了贵州省张家湾子金矿苔藓植物,并利用原子荧光光谱仪AF-640和AAnalyst800原子吸收光谱仪,对重污染区、相对污染区和清洁区苔藓植物优势种及土壤基质6种重金属元素(Cu、Zn、Cd、Pb、Hg、As)含量进行测定.在该金矿共采集苔藓样品75份,鉴定为9科16属23种.优势科为丛藓科和真藓科,生活型主要有4种:矮丛集型、高丛集型、交织型和平铺型,矮丛集型以80.3％占绝对优势.重金属含量测定结果表明,该矿区受Hg、As、Cd污染严重;硬叶净口藓对Cd的富集系数为5.58,属于强烈富集;匐灯藓对Cd富集系数为1.64,属于相对富集.苔藓与土壤重金属含量呈正相关,苔藓植物能监测该矿区重金属污染.     

铜尾矿库剑叶金鸡菊根际尾矿和植株的重金属元素含量及相关性分析

以安徽省铜陵市杨山冲铜尾矿库复垦区(覆土复垦)和未复垦区生长的剑叶金鸡菊(Coreopsis lanceolata Linn.)为研究对象,对2个区域剑叶金鸡菊根际尾矿的基本理化性质和6种重金属元素含量进行了比较,并对2个区域剑叶金鸡菊不同器官的重金属元素含量及其转移系数和富集系数,以及Ca和总磷含量及其比值(R)进行了比较;在此基础上,对不同器官重金属元素含量与根际尾矿相应重金属元素含量以及相应器官Ca和总磷含量及R值进行了Pearson相关性分析。结果表明:2个区域的根际尾矿均偏碱性;复垦区根际尾矿的电导率及有机质、总碳、总氮、总磷、速效磷、速效钾、Cu、Zn、Pb和Cd含量均高于未复垦区;并且,2个区域根际尾矿的Cu、Zn、As和Cd含量均超过国家土壤二级标准。2个区域剑叶金鸡菊各器官的Cu、Zn和Mn含量均较高,而Pb、Cd和As含量较低;主根和须根的Cu和As含量以及茎叶的Cd和Zn含量均较高。与未复垦区相比,复垦区剑叶金鸡菊主根的Zn、Pb、Cd、Mn和As含量较高,而茎叶的重金属元素含量却较低。2个区域剑叶金鸡菊中Cd的转移系数最大,而Cu和As的转移系数分别为最小和未检出;并且,复垦区剑叶金鸡菊中Zn、Pb、Cd和Mn的转移系数显著(P0.05)低于未复垦区。2个区域剑叶金鸡菊不同器官重金属元素的富集系数大多较低。另外,复垦区剑叶金鸡菊主根的Ca和总磷含量以及须根和茎叶的总磷含量均高于未复垦区。相关性分析结果表明:剑叶金鸡菊主根和须根的Pb含量与根际尾矿的Pb含量分别呈显著和极显著(P0.01)正相关,茎叶的Cu和Zn含量与根际尾矿的相应重金属元素含量分别呈极显著和显著负相关;主根的Mn含量与Ca和总磷含量呈显著正相关;须根的Cd和As含量与Ca含量分别呈极显著和显著负相关,Mn含量与总磷含量呈显著负相关;茎叶的Cu、Zn和Cd含量与Ca含量以及Cu和Mn含量与R值均呈显著正相关,Mn含量与Ca含量呈极显著正相关。综合分析结果显示:剑叶金鸡菊对6种重金属元素均有一定的吸收和积累能力,属于多重金属耐性植物;并且,覆土复垦可显著降低重金属元素从剑叶金鸡菊根部向茎叶转移,建议将其作为Cu和As污染地植物固定修复的物种。     

浙江油茶产地土壤和果实金属元素含量特征

为探讨油茶(Camellia oleifera)产地土壤和油茶果实中金属元素分布和富集特征,在油茶果实成熟期,对浙江5个油茶产地土壤及油茶果实中金属元素进行污染分析和富集能力评价。结果表明,浙江油茶产地土壤中Pb、Cr、Cd、As、Hg、Ni、Cu和Zn含量低于农用地土壤污染风险筛选值,综合污染等级为安全。个别产区常山县土壤中As、Ni、Cu和江山县土壤中Pb、Cr、Fe含量显著高于其他产地;常山和建德土壤中Cd单因子污染指数分别为0.93和0.81,处于污染警戒线。Cr、Ni、Cu、Zn主要分布在油茶籽中,Hg主要分布在壳中,Pb、Cd、As、Fe和Mn主要分布在青皮中。油茶籽中Cu、Fe、Mn的富集系数大于0.4,吸收能力强,Ni、Zn的富集系数小于0.4,具有一定吸收能力,Pb、Cr、Cd、As和Hg的富集系数小于0.1,吸收能力低;壳中Cu、Mn的富集系数大于0.4,吸收能力强,Fe的富集系数小于0.4,具有一定吸收能力,Pb、Cr、Cd、As、Hg、Ni、Zn的富集系数小于0.1,吸收能力低;青皮中Cu、Fe、Mn的富集系数大于0.4,吸收能力强,Pb、Cr、Cd、As、Hg、Ni、Zn的富集系数小于0.1,吸收能力低。浙江油茶主产区土壤质量安全,适合油茶种植。油茶果实对Cu、Fe、Mn有一定富集能力,对Pb、Cr、Cd、As和Hg无富集能力。     

乐安河—鄱阳湖湿地植物群落特征及其优势植物对重金属Cu、Pb、Cd的富集

选择乐安河—鄱阳湖湿地典型植物群落,采用重要值方法评价各样点植物群落特征并筛选出典型优势植物,通过室内理化测试分析不同生境中优势植物植株及其根区土壤中重金属Cu、Pb、Cd的含量;采用生物富集系数(BCF)方法评价不同优势植物对重金属Cu、Pb、Cd的富集特性。结果表明:研究区湿地植物以草本为主,在各样点共发现124种物种,包括蕨类植物2科2属2种,种子植物40科97属122种,并从中筛选出羊蹄、红蓼、鼠曲草、紫云英、苎麻等5种富集能力较强的优势植物;植物根区土壤中的Cu、Cd含量均超过土壤环境质量三级标准,而且Cu、Cd的最高含量分别为824.03、5.03 mg·kg-1;不同优势植物对Cu、Pb、Cd等3种重金属元素中的1种或2种表现出较强的富集能力,其中优势物种红蓼对Cu具有较强的富集能力,含Cu量最高为148.80 mg·kg-1,另一种优势物种鼠曲草对三种元素的生物富集系数均较高,且对Cd的最高富集含量为15.17 mg·kg-1,对Cd的生物富集系数最高值为19.14,高于其他植物10倍以上,鼠曲草对重金属Cd具有富集植物的基本特征,且对Cu和Cd具有共富集特征并具有较高的耐性,紫云英、羊蹄等对Cd的富集能力也较强。上述5种优势植物种群对鄱阳湖湿地Cu、Pb、Cd等重金属污染物的生态修复具有一定参考价值,可作为鄱阳湖湿地重金属污染修复植物的选择对象。     

Phytoremediation of Heavy Metals in Contaminated Water and Soil Using Miscanthus sp. Goedae-Uksae 1

The aim of this study is to characterize the heavy metal phytoremediation potential of Miscanthus sp. Goedae-Uksae 1, a hybrid, perennial, bio-energy crop developed in South Korea. Six different metals (As, Cu, Pb, Ni, Cd, and Zn) were used for the study. The hybrid grass effectively absorbed all the metals from contaminated soil. The maximum removal was observed for As (97.7%), and minimum removal was observed for Zn (42.9%). Similarly, Goedae-Uksae 1 absorbed all the metals from contaminated water except As. Cd, Pb, and Zn were completely (100%) removed from contaminated water samples. Generally, the concentration of metals in roots was several folds higher than in shoots. Initial concentration of metals highly influenced the phytoremediation rate. The results of the bioconcentration factor, translocation factor, and enrichment coefficient tests indicate that Goedae-Uksae 1 could be used for phytoremediation in a marginally contaminated ecosystem.     

表面活性剂对长柔毛委陵菜(Potentilla griffithii var. velutina)修复重金属污染的促进作用

研究了十二烷基苯磺酸钠(SDBS)、十六烷基三甲基溴化铵(CTAB)、聚乙二醇辛基苯基醚(TritonX-100)等不同离子类型的表面活性剂对水稻土中重金属的解吸效果,并采用盆栽实验研究了上述3种表面活性剂对Zn超富集植物长柔毛委陵菜(Potentilla griffithii var. velutina)的生物量、吸收和富集重金属的影响.结果表明:CTAB对水稻土中Zn、Pb、Cd和Cu的解吸效果好于SDBS和TritonX-100,而且3种表面活性剂对各重金属的解吸率大小都为Cd>Zn>Cu>Pb.3种表面活性剂促进长柔毛委陵菜叶、柄和根的生物量增加了0.2～2.5倍,并且长柔毛委陵菜各部位的生物量大小为叶>柄>根.3种表面活性剂都增加了长柔毛委陵菜各部位对Zn、Cd吸收及其叶和柄对Pb、Cu的吸收,同时显著促进Zn、Pb、Cd和Cu从植物根部向地上部转运,从而增加了Zn、Pb、Cd和Cu在长柔毛委陵菜地上部的提取量和分布以及长柔毛委陵菜对Zn、Pb、Cd和Cu的富集能力;因此3种表面活性剂都提高了长柔毛委陵菜修复重金属污染土壤的效率.     

Heavy metal uptake by arbuscular mycorrhizas of Elsholtzia splendens and the potential for phytoremediation of contaminated soil

A pot culture experiment and a field experiment were carried out separately to study heavy metal (HM) uptake from soil contaminated with Cu, Zn, Pb and Cd by Elsholtzia splendens Nakai ex F. Maekawa inoculated with arbuscular mycorrhizal (AM) fungi and the potential for phytoremediation. The HM-contaminated soil in the pot experiment was collected from the field experiment site. Two AM fungal inocula, MI containing only one AM fungal strain, Glomus caledonium 90036, and M II consisting of Gigaspora margarita ZJ37, Gigaspora decipens ZJ38, Scutellospora gilmori ZJ39, Acaulospora spp. andGlomus spp., were applied to the soil under unsterilized conditions. In the pot experiment, the plants were harvested after 24 weeks of growth. Mycorrhizal colonization rate, plant dry weight (DW) and P, Cu, Zn, Pb, Cd concentrations were determined. MI-treated plants had higher mycorrhizal colonization rates than MII-treated plants. Both MI and MII increased shoot and root DW, and MII was more effective than MI. In shoots, the highest P, Cu, Zn and Pb concentrations were all observed in the plants treated with MII, while MI decreased Zn and Pb concentrations and increased P but did not alter Cu, and Cd concentrations were not affected by either of two inocula. In roots, MII increased P, Zn, Pb concentrations but did not alter Cu and Cd, and MI did not affect P, Cu, Zn, Pb, Cd concentrations. Cu, Zn, Pb, Cd uptake into shoots and roots all increased in MII-treated plants, while in MI-treated plants, Cu and Zn uptake into shoots and Cu, Zn, Pb, Cd into roots increased but Pb and Cd uptake into shoots decreased. In general, MII was more effective than MI in promoting plant growth and HM uptake. The field experiment following the pot experiment was carried out to investigate the effects of MII under field conditions. The 45-day-old nonmycorrhizal and MII-colonized seedlings of E. splendens were transplanted to HM-contaminated plots and harvested after 5 months. MII-inoculation increased shoot DW and shoot P, Cu, Zn, Pb concentrations significantly but did not alter shoot Cd concentrations, which led to higher uptake of Cu, Zn, Pb, Cd by E. splendens shoots. These results indicate that the AM fungal consortium represented by MII can benefit phytoextraction of HMs and therefore play a role in phytoremediation of HM-contaminated soils.     

Heavy metal absorption status of five plant species in monoculture and intercropping

Absorption ability for heavy metals varies among plant species. This study is to evaluate the absorption characteristics of different plant species and planting patterns for heavy metals. Five plant species (tomato, maize, greengrocery, cabbage, and Japan clover herb) were cultivated in monoculture and in intercropping in soil contaminated with heavy metals (Cd, Pb, Cr, Cu, and Fe), to determine the absorption status. Tomato absorbs greater amounts of heavy metals (especially Cd). Furthermore, accumulation of heavy metals increased when tomato was intercropped with other plant species. Maize accumulates greater amounts of Cr, Cu, and Fe. The heavy metal concentrations were reduced when maize was intercropped. Cd and Pb accumulated more in roots of Japan Clover Herb, and the levels of all five heavy metals decreased when intercropped. Tomato intercropping is a feasible method for phytoremediation of heavy metal-contaminated soil, and maize intercropping is feasible for obtaining safe harvest which can be eaten securely.     

Assessing the Tolerance of Castor Bean to Cd and Pb for Phytoremediation Purposes

This study evaluated Cd and Pb accumulation by castor bean (Ricinus communis cv. Guarany) plants grown in nutrient solution, aiming to assess the plant’s ability and tolerance to grow in Cd- and Pb-contaminated solutions for phytoremediation purposes. The plants were grown in individual pots containing Hoagland and Arnon’s nutrient solution with increasing concentrations of Cd and Pb. The production of root and shoot dry matter and their contents of Cd, Pb, Ca, Mg, Cu, Fe, Mn, and Zn were evaluated in order to calculate the translocation and bioaccumulation factors, as well as toxicity of Cd and Pb. Cadmium caused severe symptoms of phytotoxicity in the plant’s root and shoot, but no adverse effect was observed for Pb. Castor bean is an appropriate plant to be used as indicator plant for Cd and tolerante for Pb in contaminated solution and it can be potentially used for phytoremediation of contaminated areas.     

Phytochelatins as biomarkers for heavy metal stress in maize (Zea mays L.) and wheat (Triticum aestivum L.): combined effects of copper and cadmium

Heavy metal contaminated soils often show increased levels of more than one metal, e.g. copper (Cu), cadmium (Cd), zinc (Zn), lead (Pb) or nickel (Ni). In case such soils are used for crop production, prediction of yield reduction or quality decline due to heavy metals in the soil is inadequate when based only on chemical soil analysis. The use of biomarkers such as phytochelatins (PC), non-protein thiols specifically induced in plants upon exposure to heavy metals, may be an additional tool or diagnostic criterion in heavy metal research and in practice. In the present work, Cu and Cd uptake and induction of PC synthesis are studied with hydroponically grown maize and wheat plants exposed to mixtures of the two metals. We observed a close positive relationship between the concentrations of Cd and PC in the plant shoot material. A decreased shoot concentration of Cd after addition of Cu, due to metal competition at common root absorption sites, coincided with lower shoot PC levels. Also differences in metal uptake and xylary metal transport among the two plant species were reflected in corresponding differences in PC concentration. The observed direct relationship between shoot PC concentration and the degree of metal-induced growth inhibition makes the use of PC promising for the purpose tested for.     

Accumulation of zinc, cadmium, and lead in four populations of Sedum alfredii growing on lead/zinc mine spoils

Sedum alfredii Hance is a newly reported zinc (Zn) and cadmium (Cd) hyperaccumulator native to China. In this study,four populations of S. alfredii were collected from Yejiwei (YJW), Jinchuantang (JCT) and Qiaokou (QK) lead (Pb)/Zn mines located in Hunan Province as well as Quzhou (QZ) Pb/Zn mine located in Zhejiang Province for exploring the intraspecies difference of this plant in metal accumulation. Although they grew in the Pb/Zn spoils with relatively similar levels of Zn,Cd and Pb, remarkable differences among the four populations in tissue heavy metal concentrations were observed. The shoot Zn concentration of QZ population (11 116 mg/kg) was highest and nearly five times higher than that of the JCT population (1930 mg/kg). Furthermore, the shoot Cd concentration observed in the QZ population (1 090 mg/kg) was also highest and 144 times higher than that found in the JCT population (7.5 mg/kg). As for Pb concentrations In the shoot of different populations, a fourfold difference between the highest and the lowest was also found. Such difference on metal accumulation was opulation-specific and may be significantly explained by differences in the soil properties such as pH, organic matter (OM), and electrical conductivity (EC). Taking biomass and metal concentration in plants into consideration, the QZ, YJW and QK populations may have high potential for Zn phytoremediation, the QZ population may have the highest potential in Cd phytoremediation, and the QK population may be the most useful in Pb phytoremediation.     

Effect of arbuscular mycorrhizal fungal inoculation on heavy metal accumulation of maize grown in a naturally contaminated soil

A pot culture experiment was carried out to study heavy metal (HM) phytoaccumulation from soil contaminated with Cu, Zn, Pb, and Cd by maize (Zea mays L.) inoculated with arbuscular mycorrhizal (AM) fungi (AMF). Two AM fungal inocula--MI containing only one AM fungal strain (Glomus caledonium 90036) and MII consisting of Gigaspora margarita ZJ37, Gigaspora decipens ZJ38, Scutellospora gilmori ZJ39, Acaulospora spp., and Glomus spp.--were applied to the soil under unsterilized conditions. The control received no mycorrhizal inoculation. The maize plants were harvested after 10 wk of growth. MI-treated plants had higher mycorrhizal colonization than MII-treated plants. Both MI and MII increased P concentrations in roots, but not in shoots. Neither MI nor MII had significant effects on shoot or root dry weight (DW). Compared with the control, shoot Cu, Zn, Pb, and Cd concentrations were decreased by MI but increased by MII. Cu, Zn, Pb, and Cd uptake into shoots and roots all increased in MII-treated plants, while in MI-treated plants Cu, Zn, and Pb uptake into shoots and Cd uptake into roots decreased but Cu, Zn, and Pb uptake into roots and Cd into shoots increased. MII was more effective than MI in promoting HM extraction efficiencies. The results indicate that MII can benefit HMphytoextraction and, therefore, show potential in the phytoremediation of HM-contaminated soils.     

Functional expression of a bacterial heavy metal transporter in Arabidopsis enhances resistance to and decreases uptake of heavy metals

Large parts of agricultural soil are contaminated with lead (Pb) and cadmium (Cd). Although most environments are not heavily contaminated, the low levels observed nonetheless pose a high risk of heavy metal accumulation in the food chain. Therefore, approaches to develop plants with reduced heavy metal uptake are important. Recently, many transgenic plants with increased heavy metal resistance and uptake of heavy metals were developed for the purpose of phytoremediation. However, to reduce heavy metal in the food chain, plants that transfer less heavy metals to the shoot are required. We tested whether an Escherichia coli gene, ZntA, which encodes a Pb(II)/Cd(II)/Zn(II) pump, could be useful for developing plants with reduced heavy metal content. Yeast cells transformed with this gene had improved resistance to Pb(II) and Cd(II). In Arabidopsis plants transformed with ZntA, ZntA was localized at the plasma membrane and improved the resistance of the plants to Pb(II) and Cd(II). The shoots of the transgenic plants had decreased Pb and Cd content. Moreover, the transgenic protoplasts showed lower accumulation of Cd and faster release of preloaded Cd than wild-type protoplasts. These results show that a bacterial transporter gene, ZntA, can be functionally expressed in plant cells, and that that it may be useful for the development of crop plants that are safe from heavy metal contamination.