Greenhouse evaluation of EDTA effectiveness at enhancing Cd,Cr, and Ni uptake in <Emphasis Type="Italic">Helianthus annuus</Emphasis> and <Emphasis Type="Italic">Thlaspi caerulescens</Emphasis>

Background, Aims and Scope  Phytoremediation is a promising means for the treatment of heavy metal contamination. Although several species have been identified as hyperaccumulators, most studies have been conducted with only one metal. Experiments were conducted to investigate the ability of Helianthus annuus and Thlaspi caerulescens to simultaneously uptake Cd, Cr and Ni. Materials and Methods  The efficiency of plants grown in a sandy-loam soil was investigated. The ability of two EDTA concentrations (0.1 and 0.3 g kg⁻¹) for enhancing the phytoremediation of Cd, Cr and Ni at two different metal concentrations (24.75 mg kg⁻¹ and 90 mg kg⁻¹) was studied. Results   Thlaspi hyperaccumulated Ni with 0.1 g kg⁻¹ EDTA. When the EDTA dosage was increased to 0.3 g kg⁻¹, Thlaspi was able to hyperaccumulate both Ni and Cr. Since Thlaspi is a low-biomass plant, it was considered insufficient for full-scale applications. Helianthus annuus hyperacummulated Cr (with 0.1 g kg⁻¹ EDTA) and Cd (0.3 g kg⁻¹ EDTA). Discussion  When the contamination was 8.25 mg kg⁻¹ per metal, the total metal uptake was 10–25% (1.35 to 2.12 mg) higher and had the same uptake selectivity (Cr>>Cd>Ni) for both EDTA levels. It was hypothesized that complexation with EDTA interfered with Ni translocation. For these experiments, the optimal results were obtained with the H. annuus-0.1 g kg⁻¹ EDTA combination. Conclusions  Although the use of EDTA did increase the amount of metal that could be extracted, care should be taken during in-situ field applications. Chelators can also increase the amount of metals that are leached past the root zone. Metal leaching and subsequent migration could lead to ground water contamination as well as lead to new soil contamination. Recommendations and Perspectives  Additional research to identify the optimal EDTA dosage for field applications is warranted. This is necessary to ensure that the metals do not leach past the root zone. Identification of a plant that can hyperaccumulate multiple metals is critical for phytoremediation to be a viable remediation alternative. In addition to being able to hyperaccumulate multiple metals, the optimal plant must be fast growing with sufficient biomass to sequester the heavy metals.     

EDTA强化盐生植物修复Pb、Cd和盐渍化复合污染土壤

为修复重金属和盐渍化复合污染土壤,采用温室盆栽实验,研究了EDTA强化盐生植物景天三七(Sedum aizoon L.)和翅碱蓬(Suaeda salsa)对土壤中Pb、Cd和盐分阴离子(NO_3~-、Cl-、SO_4~(2-))的去除效果。结果表明,EDTA能够促进盐生植物吸收和富集污染土壤中的Pb、Cd,当添加4 mmol·kg~(-1)的EDTA时,对于Pb、Cd中度污染土壤,景天三七对2种重金属的去除率分别为32.59%和36.47%,翅碱蓬分别为22.93%和29.36%;对于Pb、Cd和盐分阴离子复合污染土壤,景天三七对轻度污染土壤中2种重金属的去除率分别为41.37%和47.25%,翅碱蓬对中度污染土壤中2种重金属的去除率分别为36.42%和41.48%,景天三七对3种盐分阴离子的去除率表现为NO_3~-Cl-SO_4~(2-),而翅碱蓬对盐分阴离子的去除效果差异较小。景天三七的生物量明显大于翅碱蓬,植物抗逆性指标显示景天三七耐受Pb、Cd和盐分阴离子的能力更强。EDTA强化景天三七修复实际污染土壤,Pb、Cd的去除率分别达到37.87%和41.61%,NO_3~-、SO_4~(2-)和Cl-分别为59.22%、42.11%和51.65%,能够有效修复重金属和盐渍化复合污染土壤。     

EDTA与耐性细菌对黑麦草吸收复合污染红壤中铅镉的影响

为比较耐性细菌与EDTA两种方法强化植物富集重金属效果的优劣,以黑麦草(Lolium perenne L.)为供试植物,利用土培试验和室内分析,比较EDTA与耐性细菌(Rhodococcus baikonurensis,编号为J6)对黑麦草吸收重金属复合污染土壤中铅(Pb)、镉(Cd)的影响。试验采用双因素完全随机区组设计,因素一为Cd、Pb污染浓度,设置6个水平,各个水平的Cd、Pb浓度分别为0、0 mg·kg~(-1);5、50 mg·kg~(-1);10、100 mg·kg~(-1);20、200 mg·kg~(-1);50、400 mg·kg~(-1);80、800 mg·kg~(-1),并依次以代号A1、A2、A3、A4、A5、A6表示。因素二为分别添加EDTA、接种J6菌,以空白为对照。结果表明:在A1、A2条件下,添加J6菌可促进黑麦草生长,提高生物量。接种J6菌对黑麦草吸收Pb、Cd具有促进作用,在不同浓度的重金属处理条件下,接菌后的黑麦草地上部Cd含量呈提高趋势,最高达27%、地下部Pb、Cd含量也分别提高17%~64%、5%~23%;而添加EDTA后的黑麦草仅有地下部Pb含量提高40%(A5)、60%(A6)。接种J6菌可降低根际土的Cd、Pb全量,同时提高有效态Cd、Pb含量。接种J6菌也可提高黑麦草Cd的转运系数。总体而言,接种J6菌可促进黑麦草对重金属复合污染土壤中的Cd、Pb的吸收,其效果优于添加螯合剂EDTA。     

Phytoextraction of Pb and Cd from a contaminated agricultural soil using different EDTA application regimes: Laboratory versus field scale measures of efficiency

Enhanced phytoextraction of heavy metals using chelating agents and agricultural crops is widely discussed as a remediation technique for agricultural soils contaminated with low mobile heavy metals. In this study, phytoextraction efficiency of Zea mays after single and split applications of EDTA was tested on the laboratory and the field scale. EDTA effectively increased the mobility of target heavy metals (Pb and Cd) in the soil solution. Split applications provided generally lower water-soluble levels of Pb and Cd both in the pot and the field experiment. Therefore, the risk of groundwater contamination may be reduced after split applications. Higher Pb and Cd mobilisation after single applications increased plant stress, phytotoxicity and reduced plant dry above-ground biomass production compared to corresponding split doses. Single doses enhanced plant uptake of Pb and Cd and the phytoremediation efficiency compared to corresponding split doses. Results of plant dry above-ground biomass and heavy metal uptake obtained from the pot experiment could be to some extent verified in the field experiment. Plant uptake of Pb and Cd was lower and biomass production dropped after EDTA additions in the field experiment. Remediation factors in the field experiment were in general significantly lower than in the pot experiment mainly due to the much higher mass of soil per plant under field conditions. This highlights the limitations when going from the lab to the field scale. The low phytoremediation efficiency in the field and the mobilisation of high amounts of Pb and Cd down the soil profile may make the use of EDTA and Z. mays not suitable for the remediation of severely heavy metal contaminated soils in a reasonable time frame and may result in substantial groundwater pollution under used crop management.     

Plant-Available Phosphorus after Application of Synthetic Chelating Agents

Fertilizer phosphorus (P) can become immobilized in acidic soils through bonds with iron (Fe) and aluminum (Al). Two chelating agents, ethylenediamine tetraacetic acid disodium salt (EDTA) and hydroxyethyl ethylenediamine triacetic acid (HEEDTA), were tested in a greenhouse study for efficiency at increasing plant-available P to corn (Zea mays L.). Fertilizer P was added with or without chelate to the center of pots, simulating a starter band of P. Without the presence of chelates, biomass above and below ground increased linearly as P fertilizer rates increased at 0, 9.6, 19.3, 28.9, and 38.5 kg P ha^?1. Applications of EDTA and HEEDTA did not significantly increase water-soluble P (WSP), Mehlich 1 P, and Mehlich 3 P compared to soils without chelates. Applications of EDTA increased P uptake in the belowground biomass. Despite previous research showing that chelates increased WSP in soils, a decrease in P sorption was not observed with the additions of chelating agents to soils.     

两种螯合剂单独和复合浸提土壤重金属效果的研究

为揭示土壤重金属的浸出规律,采用振荡浸提方法,研究了三聚磷酸钠(STPP)和乙二胺四乙酸钠(Na2EDTA)对土壤中Pb、Cd和Cu的浸出效果,重点考察混合液浓度、振荡时间、p H对土壤重金属浸出率的影响,并比较浸提前后重金属的存在形态。结果表明:Na2EDTA和STPP均能将土壤中重金属离子浸出,其中STPP的浸出能力较小;浸提剂浓度为5 mmol·L-1时,混合液对Pb、Cd和Cu的浸出率均高于同浓度的Na2EDTA、STPP单独浸提的浸出率;当浸提剂浓度大于10 mmol·L-1时,混合液对Pb、Cu的浸出率低于同浓度的Na2EDTA、STPP单独浸提的浸出率;混合浸提剂对重金属的浸出率随p H的升高有所降低,浓度为10 mmol·L-1、振动时间为2 h较为适宜;混合浸提剂主要浸出酸可交换态、还原态、氧化态的重金属,能较大程度地降低土壤中重金属的含量。     

有机酸和EDTA对铅污染土壤上蒜苗品质的影响

研究了外源有机酸(草酸、柠檬酸)和EDTA对铅胁迫蒜苗的缓解效应.结果表明:在铅污染土壤上施用外源柠檬酸+草酸、EDTA、柠檬酸+草酸+1/2 EDTA、柠檬酸+草酸+1/3EDTA可增强蒜苗抗性,提高产量,降低铅含量,改善蒜苗品质.综合蒜苗各品质指标及铅含量,以使用柠檬酸+草酸+1/3EDTA效果最好,该处理明显降低了蒜苗铅含量,又缓解了EDTA对蒜苗品质的负面效应,对铅污染土壤上蒜苗安全生产可起到积极效果.     

海带岩藻聚糖硫酸酯纯化去除重金属砷和铅的研究

从福建省沿海生长的海带中提取岩藻聚糖硫酸酯,采用截留分子量50、30、10ku的平板超滤膜进行梯度超滤,发现50ku以上占了提取的岩藻聚糖硫酸酯的(84.29±2.772)%。采用EDTA和盐酸处理分子量大于50ku的岩藻聚糖硫酸酯,结合超滤技术进行脱除重金属As和Pb元素的研究,分别用原子荧光光谱仪和电感耦合等离子质谱检测处理前后岩藻聚糖硫酸酯中重金属As和Pb元素的残留量。结果显示,超滤后岩藻聚糖硫酸酯的相对电导率明显降低;用SPSS13.0统计方法对数据进行t检验,结果表明,试验组与对照组存在显著性差异,即用超滤结合螯合方法能显著脱除岩藻聚糖硫酸酯中重金属As和Pb。     

舒巴坦、EDTA对抗菌药物体外抗菌活性的影响

为探明β-内酰胺酶抑制剂舒巴坦和膜通透性促进剂EDTA对抗菌药物体外抗菌活性的影响及二者之间的相互作用。采用微量肉汤稀释法,测定了12种抗菌药物及其与舒巴坦、EDTA、舒巴坦+EDTA联用对临床分离的6株产超广谱β-内酰胺酶(ESBLs)鸡大肠杆菌的最低抑菌浓度(MIC)。结果表明,舒巴坦降低了第3代头孢菌素类、阿米卡星、氟苯尼考及磷霉素的MIC值;EDTA降低了氟喹诺酮类、多西环素、氟苯尼考及黏菌素的MIC值;舒巴坦+EDTA与阿米卡星、磷霉素、氟苯尼考、第3代头孢菌素联用较舒巴坦或EDTA与这4类抗菌药联用对多数菌株的MIC值均进一步降低。β-内酰胺酶抑制剂舒巴坦和膜通透性促进剂EDTA不仅可以增强部分抗菌药对产ESBLs鸡大肠杆菌的抗菌效果,而且二者之间有一定的协同作用。     

EDTA对玉米汞害的缓解机制初探

研究表明,向含汞污水中加入ＥＤＴＡ,能恢复汞引起的玉米种子萌发过程中的淀粉酶、脂肪酶、蛋白酶、呼吸速率的降低,并恢复汞引起的苗期生长过程中的叶绿素含量、叶可溶性糖的积累速度,根系活力,以及硝酸还原酶活力的降低。导致种子萌发和幼苗生长恢复。