Copper Release Behavior in Two Calcareous Soils Amended with Three Organic Materials

Understanding time-dependent copper (Cu) desorption behavior is critical for improving the prediction of Cu availability in soils. This study was conducted to evaluate the influence of municipal waste compost, sheep manure, and wheat straw on desorption characteristics of Cu and to evaluate the suitability of different kinetic models to describe the Cu release pattern in two calcareous soils. Diethylenetriaminepentaacetic acid (DTPA) and ethylenediaminetetraacetic acid (EDTA) were employed to extract Cu from soils. Best-fitted kinetic models including Elovich, simple Elovich, two-constant rate, and parabolic diffusion were selected based on their low standard error and high coefficient of determination. Extractable copper significantly decreased with increasing rates of sheep manure and wheat straw but increased with increasing rates of municipal waste compost amendment. Results revealed that copper was more readily desorbed from clay soil compared to silt loam soil. The copper desorption patterns were almost similar for both extractants; however, EDTA extracted more Cu from soils.     

Mehlich 3 soil test extractant: A modification of Mehlich 2 extractant

Abstract

The objectives of this study were to modify the Mehlich 2 (M2) extractant to include Cu among the extractable nutrients, retain or enhance the wide range of soils for which it is suitable and minimize it's corrosive properties. The substitution of nitrate for chloride anions and the addition of EDTA accomplished those objectives. The new extracting solution, already designated Mehlich 3 (M3) is composed of 0.2N CH₃COOH‐0.25N NH₄N0₃‐0.015NNH₄F‐0.013NHN0₃‐0.001M EDTA. Extractions from 105 soils using M3, M2, Bray 1 (Bl) and Ammonium Acetate (AA) were compared to evaluate the new extractant. The quantity of F extracted by M3 exceeded that by M2 20% and that by Bl 4% but the results from all extractions were highly correlated. Extractions of both K and Mg by M3 were 6–8% higher than those by AA and 3–4% higher than those by M2, but, again, there was high correlation among methods. Addition of EDTA increased Cu extractions by 170%, Mn by 50% and Zn by 25%. Cu extractions by M3 correlated with those from the Mehlich‐Bowling method. High correlations between Mn, as well as Zn, extracted by M3 and M2 were shown.     

Effects of Lead Forms and Organic Acids on the Growth and Uptake of Lead in Hydroponically Grown Wheat

This study investigated the effects of lead (Pb) form (free or complexed) and type and concentration of chelants [citric acid and ethylenediaminetetraacetic acid (EDTA)] on the growth and ability of wheat to accumulate Pb. Wheat variety Auqab-2000 was exposed to four levels of EDTA and citric acid (0, 500, 1000, and 1500 μM) in the presence of Pb (1000 μM). Both the free Pb (1000 μM) and high concentration (1500 μM) of EDTA and citric acid reduced the plant biomass. Without the addition of chelants, only a little Pb was accumulated by wheat shoots. This demonstrates that organic acids used in enhanced phytoextraction applications do not merely serve to increase metal mobility and plant availability but also can help to increase translocation rates of metals absorbed by the plant roots. Greater translocation of Pb from roots to shoots was observed with EDTA than that with citric acid.     

腐植酸、EDTA、Cr(Ⅵ)调控猪粪尿废水异化Fe(Ⅲ)还原偶联VFAs的转化能力比较

以人工合成Fe(OH)3作为电子受体,在猪粪尿废水中添加具有铁还原能力的菌株,厌氧恒温培养,通过对猪粪尿废水中添加不同浓度腐植酸、EDTA、Cr(Ⅵ),揭示3种典型理化因素调控猪粪尿废水中异化Fe(Ⅲ)还原偶联挥发性脂肪酸(Volatile fatty acids,VFAs)转化能力。结果表明,电子穿梭体腐植酸促进Fe(Ⅲ)还原,加速VFAs降解,而络合剂EDTA和重金属Cr(Ⅵ)则会阻碍Fe(Ⅲ)还原,减缓VFAs降解。虽然三种影响因子影响机理不同、途径不同,但最终Fe(Ⅲ)还原和VFAs平衡点不变。     

EDTA对中低污染土壤中重金属的解吸动力学

采用0.05 mol·L-1的 EDTA 作为解吸剂,对中低污染负荷土壤中Cd、Pb、Cu、Zn进行了振荡解吸研究,并运用一级动力学方程、Elovich方程和双常数方程进行模拟.结果表明,污染土壤中重金属Cd、Pb、Cu、Zn的解吸率随着解吸时间的延长而不断增加,中污染负荷土壤Cd、Ph、Cu、Zn解吸率高于低污染负荷土壤.反应720 min后,EDTA对中污染和低污染土壤中Cd、Pb、Cu、Zn的解吸率分别为Cd 45.16%、30.88%,Pb 51.32%、26.45%,Cu 17.86%、14.23%,Zn 23.31%、19.63%.双常数方程是描述污染土壤中Cd、Pb、Cu、Zn解吸动力学过程的最佳方程,其次为Elovich方程,最差模型是一级动力学方程.Cd、Pb、Cu、Zn的解吸速率随解吸时间延长而不断降低,Cd、Pb、Cu、Zn在中污染土壤中的解吸速率大于其在低污染土壤中的解吸速率.     

EDTA对Zn胁迫下紫花苜蓿生长和Zn积累特性的影响

以紫花苜蓿为材料,采用盆栽法,研究了EDTA对Zn胁迫下紫花苜蓿生长和Zn积累特性的影响,为螯合剂诱导植物修复Zn污染土壤提供理论指导依据。结果表明,与CK(不施加Zn和EDTA)相比,单一Zn胁迫(250μg/kg Zn)下紫花苜蓿的株高、叶片干质量、根系干质量、叶片相对生长量、叶绿素a含量、叶绿素b含量和叶绿素a/b增加,但与CK差异不显著;而Zn+EDTA复合处理(250μg/kg Zn+10μg/kg EDTA)的紫花苜蓿叶片干质量、叶片相对生长量、根系相对生长量、叶绿素a含量、叶绿素b含量、叶片Zn含量、耐性指数较单一Zn胁迫处理分别显著增加了24.9%、35.7倍、2.3倍、13.0%、11.8%、27.2%、18.6%。可见,EDTA有助于提高Zn胁迫下紫花苜蓿的叶绿素含量,从而增加生物量、转运指数和耐性指数。因此,紫花苜蓿可作为重金属Zn污染土壤的修复植物,而EDTA则能有效地促进紫花苜蓿对Zn的吸收。     

Chelate-enhanced phytoextraction and phytostabilization of lead-contaminated soils by carrot (Daucus carota)

The objective of this study was to study the influence of different ethylenediamine tetraacetate (EDTA), nitrilotriacetic acid (NTA) and oxalic acid (HOx) concentrations on tolerance and lead (Pb) accumulation capacity of carrot (Daucus carota). The results indicated that by increasing Pb, NTA and HOx concentrations in the soil, the shoot, taproot and capillary root dry matters increase effectively. In contrary, EDTA caused to reduce capillary roots biomass. EDTA was more effective than NTA and HOx in solubilizing soil Pb. The highest Pb content in shoots (342.2 ± 13.9 mg kg^?1) and taproots (301 ± 15.5 mg kg^?1) occurred in 10 mM EDTA, while it occurred for capillary roots (1620 ± 24.6 mg kg^?1) in 5 mM HOx, when the soil Pb concentration was 800 mg kg^?1. The obtained high phytoextraction and phytostabilization potentials were 1208 (±25.6) and 11.75 (±0.32) g Pb ha^?1 yr^?1 in 10 mmol EDTA kg^?1 soil and no chelate treatments, respectively. It may be concluded that chelate application increases Pb uptake by carrots. Consequently, this plant can be introduced as a hyperaccumulator to phytoextract and phytostabilize Pb from contaminated soils.     

Topical effect of various agents on gelatinase activity in the tear film of normal dogs

OBJECTIVE: To evaluate the topical effect of various agents, currently used in the treatment of melting ulcers, on gelatinase activity present in the tear film of normal dogs. ANIMAL STUDIED: Eight normal adult beagles. PROCEDURES: Each animal received the following agents: cyclosporine A 1%, N-acetylcysteine 10%, ciprofloxacin 0.3%, ethylenediaminetetraacetic acid (EDTA) 1%, doxycycline 0.001%, polysulfated glycosaminoglycans (PSGAG) 5%, autoserum, and artificial tears during a 48-h period following a Latin square design. Tear samples were collected with micro-capillary pipettes following a corneal surface irrigation of each eye with sterile saline on four different occasions. Basal and total gelatinase activities were evaluated by optical density after processing in a commercial gelatinase activity assay. From the optical density ratio, a semi-quantitative measure of gelatinase activity was obtained. Basal and total activities were measured in all samples. RESULTS: The lowest total gelatinase activity, representing a percent decline in the enzyme activity although not significant, was observed 1 h after the last treatment in seven out of the eight ophthalmic agents; EDTA (68%), ciprofloxacin (76%), cyclosporine A (68%), doxycycline (47%), artificial tears (26%), PSGAG (25%), and N-acetylcysteine (20%). However, only the reduction observed with EDTA 6 h after the last treatment was significantly lower compared to the reduction observed with the artificial tears. CONCLUSION: This study indicated that only EDTA was able to significantly reduce the gelatinase activity in a persistent manner in the tear film of normal canine eyes. Further studies will be required to evaluate the effect of EDTA under ulcerative conditions and to more accurately ascertain the potential in vivo effect of the other agents.     

EDTA强化植物修复的环境风险研究

采用柱状盆栽淋溶试验,研究乙二胺四乙酸(EDTA)对有植物生长时,不同浓度Cd处理的土壤中重金属淋溶作用的影响及其动态特征。实验结果表明:土壤重金属Cd处理的浓度为80 mg/kg和160 mg/kg时,加入5 mmol/kg和10 mmol/kg的EDTA,增加了渗滤液中TOC的含量,极大地增加了渗滤液中Cd的含量,且土壤样品中TOC的淋失量和重金属Cd的淋失量都集中发生在淋溶实验的前期。两者相比EDTA对土壤中重金属的活化效应更强,遇到降水,会因淋失对地下水造成严重的重金属污染,应尽量避免在降水期间施用ED-TA。植物根系在渗滤发生的最初期对渗滤有影响,会减少渗滤液的体积,从而减少渗滤液中TOC和重金属的总含量。     

Influence of graded EDTA applications on mobilization and translocation of trace elements—a soil column experiment

Increasing concerns about potential environmental effects of ethylenediaminetetraacetic acid (EDTA) accumulation in soils require better understanding of its behavior and its effect on trace element mobilization. In this study we investigated the effect of EDTA on soil trace element mobilization in undisturbed soil columns taken from a heavy metal contaminated field. The columns were leached by EDTA solutions of different concentrations under unsaturated, steady‐state conditions. The transport of trace elements (Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sn, Zn) and EDTA was monitored by regularly collecting the leachates. After the termination of the leaching experiment the soil columns were divided into 5 layers to determine trace elements and EDTA concentrations in the soil. The results revealed that the soil analysis alone was not suitable to infer mobilization or immobilization patterns in relation to the EDTA concentration, as the mobilized fraction was too small in relation to the total trace metal concentrations in the soil. Analysis of the leachates displayed that after 2–4 pore volumes the EDTA output concentration reached about 80% of the input concentration. The trace element concentrations in the leachates showed that some elements were mobilized by EDTA (Cd, Cu, Fe, Pb, Co, Ni, Zn) while others were immobilized (Mn, Cr, Mo, Sn) in the soil columns after EDTA application.