Ethylenediaminetetraacetate Concentration Research Articles

Hemp (Cannabis sativa L.) Tolerates Chelator Stress Showing Varietal Differences and Concentration Dependence

The world’s arable land has been contaminated by heavy metals to a large extent, which has led to the decreasing availability of farmland. Thus, the remediation of heavy metal pollution deserves due attention, and phytoremediation is preferred. Hemp has been proposed as an ideal alternative crop for remediating heavy-metal-contaminated soil, owing to its well-developed roots, large biomass, and tolerance to heavy metals. Chelators can activate heavy metals to enhance plant absorption, but they may cause stress to plant growth. Therefore, it is very important to optimize the combination of chelator and plant (cultivar) for efficacious phytoremediation. The effects of different concentrations (2, 5, 10, 15, and 25 mmol·L−1) of the chelators disodium ethylene diamine tetra-acetate (EDTA) and citric acid (CA) on the seed germination and plant growth of hemp cultivars were investigated. Triple application of increasing concentrations of EDTA or CA two days apart gradually reduced the germination potential, germination rate, radicle length, and embryonic shoot length of hemp seed, although 2 mmol·L−1 of CA could even promote seed germination. Distinct varietal differences were found in the response of hemp to chelator stress. Under the scheme of four-time uses one week apart, both chelators caused a concentration-dependent linear decrease in the plant height, stem diameter, and biomass of hemp plants, but the growth inhibition due to CA was relatively milder. This could be partially explained by the change in tested physiological indices in hemp leaf. In conclusion, 2 mmol·L−1 of CA helped with seed germination and was almost nontoxic to plant growth; cultivar BM was more tolerant to the chelators than cultivar Y1.

Effect of chelating agents on phytoxicity and bioaccumulation of heavy metals in vascular plants

In this work the effect of chelating agents ethylenediaminetetraacetate (EDTA) and nitrilotriacetate (NTA) on phytotoxicity and bioaccumulation of Cd and Co in tobacco plants (Nicotiana tabacum L.) hydroponically grown in diluted Hoagland media (HM) spiked with 109Cd and 60Co was studied. Speciation analysis using a program Visual MINTEQ showed, that the portion of bioavailable ionic Me2+ forms significantly decreased in the presence of EDTA or NTA in 25% HM for account of [Me-EDTA]2- or [Me-NTA]- complexes. We found that the equimolar addition of EDTA or NTA to 50 μmol/dm3 CdCl2 or CoCl2 in HM positively diminished phytotoxicity of Cd or Co on tobacco plants. Bioaccumulation of Cd by tobacco roots during 8 d cultivation was minimally affected in the presence of equimolar concentrations of EDTA or NTA to 10 μmol/dm3 CdCl2 in media. On the contrary, equimolar concentration of EDTA or NTA added into HM caused considerable decrease of Co uptake by tobacco roots. Cadmium showed higher mobility in conductive tissues of tobacco plants than cobalt and the transport ratio in the presence of EDTA or NTA increased 2-times or 3-times in comparison with control experiments (without addition of chelates), respectively. In the case of cobalt this effect was observed in a less extent. Obtained data suggest the possibilities and constraints in the use of chelating agents in phytoextraction technologies in term of phytotoxicity, uptake and translocation of metals in plant tissues.

Solubility of TINOPAL CBS-X fluorescent dye at different EDTA concentrations and pH values: Implications regarding its applicability in field tracer tests

TINOPAL CBS-X has been described in published literature as a fluorescent dye that is suitable for use as a tracer in groundwater investigations. However, several of these field tests have yielded unexpected results. In this study the influence that the complexation agent EDTA (ethylenediaminetetraacetate) and pH have on the solubility of TINOPAL CBS-X have been systematically investigated in the laboratory and the results obtained validated with thermodynamic calculations using the PhreeqC software. Modeling indicated that the amount of EDTA required for complete TINOPAL CBS-X dissolution is, in many aquifers, so great that its use is no longer feasible. However, softening the water by adding NaOH appears to be a promising way to increase TINOPAL CBS-X solubility. Water with a low availability of bivalent and/or trivalent ions yielded solubilities up to two orders of magnitude higher than waters from limestone aquifers with a high Ca2+ ion content. Results revealed that the spectrum of TINOPAL CBS-X applicability as a conservative tracer in aquatic environments is limited to a limited range of specific water chemistries. The long tailing in the breakthrough curve and the retarded breakthrough of TINOPAL CBS-X in a previously reported carbonate karst aquifer field tracer test was accurately reproduced by a transport model with a modified input function based on solubility modeling. Travel times and attenuation by incompletely dissolved tracers are tend to be overestimated, which can be problematic with regard to predictions of contaminant transport, or the delineation of water protection zones. The use of TINOPAL CBS-X as a conservative tracer and the concentrations required needs therefore to be carefully evaluated with respect to water-hardness, pH, alkalinity, and dilution rates. An input script for PhreeqC is provided to help estimate appropriate concentrations of TINOPAL CBS-X, thus enhancing its potential and reliability for future groundwater research.

Nitric oxide removal from flue gas by combined persulfate and ferrous–EDTA solutions: Effects of persulfate and EDTA concentrations, temperature, pH and SO2

The effects of persulfate (PS) and ethylenediaminetetraacetate (EDTA) concentrations at different temperature and pH on the removal of NO were studied using combined Na2S2O8 and Fe2+-EDTA aqueous solutions. The experiments were conducted in the temperature and pH ranges of 23–70°C and 2–12, respectively, using 0.05–0.20M PS and 0.01M Fe2+ in the absence and presence of 0.005–0.050M Na2-EDTA. The effect of SO2 was also preliminarily investigated. Increased temperature led to increased conversions of NO (percent inlet NO removed) at all PS levels but high concentrations of EDTA produced antagonistic effects with increasing temperature. With 0.10M Na2S2O8, 0.01M Fe2+ and ⩽0.01M EDTA, NO conversion increased with temperature from 23 to 70°C. At 70°C, NO conversion increased from 83.40–96.28% as EDTA concentration increased from 0.005 to 0.01M EDTA but decreased to 29.22 and 0.4% with 0.02 and 0.05M EDTA, respectively. The results at 40 and 50°C showed optimal NO conversions in the pH range 6–8, and higher at 50°C. However, at higher pH (>11), NO conversion is higher at 40°C than at 50°C. The speciation and material balance of the iron species were determined at different Fe2+ and EDTA concentrations. The results, which showed sustained NO absorption at lower temperatures and mid-pH, could in practice minimize process pH adjustment and energy usage in wet scrubbers. The process could be applicable to the simultaneous cleanup of NOx and SO2 from oil- and coal-fired power plant and industrial boiler.

The effects of antioxidants and shelf life conditions on oxidation markers in a sunflower oil salad dressing emulsion (SOSDE)

The effects of levels of antioxidant [gallic acid or ethylene diamine tetraacetate (EDTA)] in a sunflower oil salad dressing emulsion (SOSDE) and shelf life affecting conditions on aroma, anisidine values (AV) and peroxide values (PV) were determined. Aroma differences between products with different concentrations of antioxidants were more apparent for ambient than accelerated stored SOSDEs. Aroma differences were more noted between SOSDEs with different antioxidants than antioxidant concentrations per se. PV differences between accelerated stored SOSDEs with high and low EDTA concentrations were found. AV differences existed between SOSDEs with different gallic acid concentrations for both storage conditions, and for accelerated stored SOSDEs with different EDTA concentrations. The accelerated storage model is more suitable for SOSDEs with metal chelator antioxidants e.g. EDTA, than free radical scavenging antioxidants e.g. gallic acid. PV, AV and aroma of accelerated stored SOSDEs do not clearly predict ambient shelf life.

A Modified o-Phthalaldehyde Fluorometric Analytical Method for Ultratrace Ammonium in Natural Waters Using EDTA-NaOH as Buffer.

In the existence of appropriate amount of disodium ethylenediaminetetraacetate (EDTA), precipitation would not occur in seawater and other natural waters even if the sample solution was adjusted to strong basicity, and the NH3-OPA-sulfite reaction at the optimal pH range could be used to determine ammonium in natural waters. Based on this, a modified o-phthalaldehyde fluorometric analytical method has been established to determine ultratrace ammonium in natural waters. Experimental parameters, including reagent concentration, pH, reaction time, and effect of EDTA, were optimized throughout the experiments based on univariate experimental design. The results showed that the optimal pH range was between 10.80 and 11.70. EDTA did not obviously affect the fluorometric intensity. The linearity range of the proposed method was 0.032–0.500 µmol/L, 0.250–3.00 µmol/L, and 1.00–20.0 µmol/L at the excitation/emission slit of 3 nm/5 nm, 3 nm/3 nm, and 1.5 nm/1.5 nm, respectively. The method detection limit was 0.0099 µmol/L. Compared to the classical OPA method, the proposed method had the advantage of being more sensitive and could quantify ultratrace ammonium without enrichment.

The Effect of Extraction Conditions on the Chemical Characteristics of Pectin from Opuntia ficus indica Cladode Flour

Pectin from the cladode flour of Opuntia ficus indica was extracted at different ethylenediaminetetraacetate concentrations (10 or 20 %), temperatures (40 or 80 °C), pH values (2 or 11), and times (10, 20, 30 40, 50 or 60 min). The effects of the extraction conditions on the yield, purity, and chemical composition of pectin were assessed. The highest pectin yield was observed for pectin obtained under alkaline conditions and 20 % of EDTA. However, pectin produced from alkaline extractions had a lower content of GalA than pectin produced from acid extractions. Higher temperatures favored the extraction of pectin under acid conditions, but these conditions diminished the arabinose content of pectins in a time-dependent manner. The tested extraction conditions caused only slight changes in the molecular weight of the extracted pectin as a function of time.

Label-free gold nanoparticles for the determination of neomycin

A new spectrophotometric method for the determination of neomycin has been developed. The method is based on aggregation of label-free gold nanoparticles leading to change in absorption spectra and color of the solution. Influence of different factors (the concentration of ethylenediaminetetraacetate (EDTA), pH, the concentrations of neomycin and the nanoparticles) on the aggregation and analytical performance of the method was investigated. EDTA plays an important role not only as a masking agent to eliminate interferences of metal cations but strongly affects the sensitivity of the nanoparticles relative to neomycin. The method allows to determine neomycin with detection limit of 28ngmL−1. It was applied to analysis of eye- and ear-drops. The sample pretreatment is simply done by diluting the formulation with water.

Remediation of an electroplating contaminated soil by EDTA flushing: chromium release and soil dissolution

Remediation of soils contaminated with Cr (as Cr(III) complexes/precipitates and/or Cr(VI) oxyanion) and cationic metals (Cu, Ni, Zn, and Pb) by ethylenediaminetetraacetate (EDTA) flushing has been challenging and rarely investigated. This study aimed to evaluate the efficiency of EDTA flushing for metal extraction of soil from an electroplating site, with a specific focus on chromium release and soil dissolution. Column flushing tests were performed on a sandy soil contaminated by electroplating activities in the field. Three EDTA concentrations (5, 10, and 20 mM) and flow interruptions were employed to investigate the operation of EDTA flushing. Results demonstrated that Cr, Cu, and Ni were continuously released along with dissolution of Fe, Al, Mg, and Mn throughout the entire flushing process (up to 600 pore volumes), whereas Zn and Pb removal primarily occurred in the first 50–200 pore volumes. By comparing the Cr and Fe release patterns, the observed Cr release by EDTA flushing possibly resulted from a combination of dissolution of Fe oxides, dissolution of metal–chromate precipitates, and ligand competition for the surface sites (substitution reaction). The latter two mechanisms appeared to be more influential at the early stage. It was also revealed that soil dissolution was predominant, and metal extraction became inefficient at the later stage of flushing, especially with the concentrated EDTA solution. On the other hand, when the flushing process was temporarily paused (i.e., flow interruptions), Cr, Cu, Ni, and Zn concentrations elevated, whereas Pb levels in the effluent decreased, indicating the significance of rate-limited metal exchange of newly formed metal–EDTA complexes. In consideration of EDTA utilization efficiency and potential ecological risks, diluted EDTA solution is recommended for field applications.

Significance of the concentration of chelating ligands on Fe3+-solubility, bioavailability, and uptake in rice plant

Present study investigated the significance of the concentration of chelating ligand on Fe(3+)-solubility in growth medium and its influence on Fe bioavailability and uptake in rice plant. Rice seedlings were grown in modified Murashige and Skoog (MS) hydroponic growth medium with moderate (250μM) and high (500μM) concentrations of ethylenediaminetetraacetate (EDTA) and hydroxyiminodisuccinate (HIDS) under sterile and non-sterile conditions. Concentrations of soluble Fe in the growth medium increased with increasing ligand concentrations, and the growth of rice seedlings was higher at moderate ligand concentration than at control (without chelant) and high ligand concentration. This explains the relationship between Fe solubility and bioavailability in the growth medium, and its effect on Fe uptake in rice plant. Fe exists in the growth medium predominantly as particulate (insoluble) forms at low ligand concentration, and as soluble [Fe(OH)(2+), Fe(OH)(2)(+), Fe-L complex] and apparently soluble (colloidal) forms at moderate ligand concentration. At high ligand concentration, most of the Fe(3+) in the growth medium forms soluble Fe-L complex, however, the bioavailability of Fe from Fe-L complex decreased due to lopsided complex formation equilibrium reaction (CFER) between Fe and the ligands. Also, Fe is solubilized forming stable and soluble Fe-L complex, which is then detached as less stable, but soluble and bioavailable substance(s) after (time-dependent) biodegradation. Therefore- i) ligand concentration and stability constant of Fe-L complex (K(Fe-L)) influence Fe bioavailability and uptake in rice plant, and ii) the biodegradable ligands (e.g., HIDS) would be more effective Fe fertilizer than the environmentally persistent and less biodegradable ligands (e.g., EDTA).

Accumulation and spatial distribution of Cd, Cr, and Pb in mulberry from municipal solid waste compost following application of EDTA and (NH4)2SO4

Municipal solid waste compost can be used to cropland as soil amendment to supply nutrients and improve soil physical properties. But long-term application of municipal solid waste (MSW) compost may result in accumulation of toxic metals in amended soil. Phytoremediation, especially phytoextraction, is a novel, cost-effective, and environmentally friendly approach that uses metal-accumulating plants to concentrate and remove metals from contaminated soils. Ethylenediaminetetraacetate (EDTA) was applied to metal-contaminated soil to increase the mobility and phytoavailability of metals in soil, thereby increasing the amount of toxic metals accumulated in the upper parts of phytoextracting plants. The objectives of this study were (1) to investigate the accumulation and spatial distribution of toxic metals (Cd, Cr, and Pb) in mulberry from MSW compost with the application of EDTA and (NH(4))(2)SO(4), (2) to examine the effectiveness of EDTA and (NH(4))(2)SO(4) applied together on toxic metals (Cd, Cr, and Pb) removal by mulberry under field conditions, and (3) to evaluate the potential of mulberry for phytoextraction of toxic metals from MSW compost. The tested plant-mulberry had been grown in MSW compost field for 4 years. EDTA solution at five rates (0, 50, 100, 50 mmol L(-1) + 1 g L(-1) (NH(4))(2)SO(4), and 100 mmol L(-1) + 1 g L(-1) (NH(4))(2)SO(4)) was added into mulberry root medium in September 2009. Twenty days later, the plants were harvested and separated into six parts according to plant height. Cd, Cr, and Pb contents in plant samples and MSW compost were analyzed using an atomic absorption spectrophotometer. In the same treatment, Cd, Cr, and Pb concentrations in mulberry shoot were all higher than those in root, and Cd and Pb concentrations in shoot increased from lower to upper parts, reaching the highest in leaves. Significant increases were found in toxic metal concentration in different parts of mulberry with increasing EDTA concentration, especially when combined with (NH(4))(2)SO(4). Mulberry exhibited high ability to accumulate Cd with bioconcentration factors (BCFs) higher than 1. EDTA application also significantly increased Cd BCFs. More than 30 % of metal uptake was concentrated in mulberry branches (stem of above 100 cm height) and leaves. Results presented here show that mulberry is a woody plant that has the potential of Cd phytoextraction from MSW compost by removing leaves and cutting branches. The application of EDTA combined with (NH(4))(2)SO(4) significantly enhanced the efficiency of mulberry in removing Cd from the compost medium. Adding (NH(4))(2)SO(4) into the compost will lower the risk of the exposure of environment to excessive non-biodegradable EDTA in a large-scale EDTA-assisted phytoextraction by reducing the dosage of EDTA. In China, the need for sod is increasing day by day. Sod is often produced on arable soil and sold together with soils. This would lead to the soil being infertile and the soil layer thin. After several times' production, the soil can no longer be used for cultivating crops and be destroyed. In order to fully utilize MSW compost resources and save valuable soil resources, MSW compost can be used to replace arable soil to produce sod after extraction of toxic metals in it.

Effects of diclofenac sodium and disodium ethylenediaminetetraacetate on electrical parameters of the mucosal membrane and their relation to the permeability enhancing effects in the rat jejunum.

The effects of diclofenac sodium and disodium ethylenediaminetetraacetate (EDTA) on electrical parameters of rat jejunal membrane were investigated, together with measurement of the mucosal-to-serosal flux of sulphanilic acid or L-phenylalanine. Both adjuvants increased the flux rate of sulphanilic acid to a similar extent when added to the mucosal solution at 10 mM, but there were apparent differences in their effects on the electrical parameters. The addition of EDTA induced the gradual reduction in the membrane resistance (Rm) by 6-8 ohm cm-2, while the effect of diclofenac on Rm was complicated and concentration-dependent. The short circuit current (Isc) was reduced rapidly to the level of 30-40 microA cm-2 by the addition of diclofenac, but was less affected by EDTA. The flux rate of L-phenylalanine was decreased extensively by diclofenac or the 10 mM concentration of EDTA, suggesting an inhibition of carrier-mediated transport systems in the membrane. Together with our preceding communication (Yamashita et al 1985, J. Pharm. Pharmacol. 37: 512-513), it became obvious that the sites of action of diclofenac and EDTA were different, the former directly interacting with the epithelial cell to alter the permeability and functions of the cell membrane, while the primary effect of EDTA could be at the intercellular junctions.

Fabrication of hierarchical CdS microspheres assembled by nanowires: solid state electro-chemiluminescence in H2O2 solution

Hierarchical CdS microspheres self-assembled by nanowires were synthesized via an ethylenediamine tetraacetate assisted solvothermal approach using cadmium chloride and l-cysteine as reaction agents. The phase structure, morphology, and optical properties of the products were investigated by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, and electro-chemiluminescence, respectively. Studies showed that the final morphology of the products was strongly influenced by the concentration of ethylenediamine tetraacetate and reaction temperature. The as-prepared hierarchical CdS spheres could be a good candidate for a detective technology due to its high electro-chemiluminescence intensity.

Redistribution of residual Pb, Zn, and Cd in soil remediated with EDTA leaching and exposed to earthworms (Eisenia fetida)

After soil remediation with ethylenediamine tetraacetate (EDTA) leaching/washing, the residual Pb, Zn, and Cd species are left in the soil in non‐labile forms. The effect of earthworms as main soil biotic factors on the residual Pb, Zn, and Cd fraction lability (mobility, bioavailability to plants, and oral‐availability) was investigated. Contaminated soil from a smelter site was treated with increasing EDTA concentrations (2.5 to 4‐times 40 mmol kg−1) to gradually reduce the heavy metal content and lability. Leached soils were processed by Eisenia fetida and heavy metal lability and fractionation determined in casts and earthworm‐processed soils. In general E. fetida increased heavy metal accessibility/mobility, but the induced changes diminished with the intensity of soil EDTA treatment. Fractionation results indicate the possibility of a time‐dependent complexation of heavy metals to carbonates favoured by earthworms’ gut processes. The transition of residual heavy metals in time (ageing) should be considered.

Adsorption Mechanisms of EDTA at the Water−Iron Oxide Interface: Implications for Dissolution

The interactions between chelating agents and metal oxide particles play important roles for the distribution and availability of metal ions in aquatic environments. In this work, the adsorption of ethylenediaminetetraacetate (EDTA) onto goethite (α-FeOOH) was studied as a function of pH, time, and background electrolyte concentration at 25.0 °C, and the molecular structures of the surface complexes formed were analyzed by means of infrared spectroscopy using the attenuated total reflectance sampling technique. The collective infrared spectroscopic results of this study show that two surface complexes consisting of HEDTA3− and H2EDTA2− predominate at the water−goethite interface within the pH range of 3−9. No direct interactions of these complexes with surface Fe(III) ions were detected; hence, most likely the surface complexes are stabilized at the interface by electrostatic and hydrogen-bonding forces. The formation of the EDTA surface complexes is fast (time scale of minutes), but a slower (time scale of hours to days) dissolution reaction also occurs. The dissolved iron in solution is in the form of the highly stable FeEDTA− solution complex, and the experimental evidence presented indicates that this complex can readsorb to the mineral surface. As dissolution proceeds, the concentration of FeEDTA− in the solution phase increases, and this in turn leads to a buildup of readsorbed FeEDTA− onto goethite. In the pH range of 4−7, this dissolution and readsorption process increases the total EDTA concentration at the surface. Under the experimental conditions in the present study, it is primarily the presence of uncomplexed EDTA in solution that drives the dissolution of goethite resulting in the subsequent readsorption of FeEDTA−, while the HEDTA3− and H2EDTA2− surface complexes are stable during this process.

Photocatalytic oxidation of cyanide in aqueous titanium dioxide suspensions: Effect of ethylenediaminetetraacetate

The kinetics of the photocatalytic oxidation of cyanide in aqueous TiO 2 suspensions was investigated as a function of catalyst loading (0.1–5.0 g l −1), air-flow rate (0.2–1.1 l min −1), and the concentration of ethylenediaminetetraacetate, EDTA (0.4–40 mM) at pH 13.0. The cyanide oxidation rate did not vary with the TiO 2 loading while a slight increase in the degradation rate with an increase in the air-flow rate was found. Cyanate (NCO −) was the only product of the cyanide decomposition. The effect of EDTA on the photocatalytic oxidation of cyanide was examined at different molar ratios of EDTA to cyanide (0.1–10.5) by keeping the initial cyanide concentration at 3.85 mM. EDTA retarded the photocatalytic oxidation of cyanide and the decrease in the oxidation rate was not proportional to the molar ratio of EDTA to cyanide. The first-order rate constant, k (min −1) for the oxidation of cyanide in the presence of EDTA may be expressed as k = 3.38 × 10 −3 × ([EDTA]/[CN −]) −0.23. A mechanism of the oxidation of cyanide by a photocatalytic process in absence and presence of EDTA is presented.

The role of EDTA in phytoextraction of hexavalent and trivalent chromium by two willow trees

Effects of the synthetic chelator ethylenediamine tetraacetate (EDTA) on uptake and internal translocation of hexavalent and trivalent chromium by plants were investigated. Two different concentrations of EDTA were studied for enhancing the uptake and translocation of Cr from the hydroponic solution spiked with K(2)CrO(4) or CrCl(3) maintained at 24.0 +/- 1 degrees C. Faster removal of Cr(3+) than Cr(6+) by hybrid willows (Salix matsudana Koidz x Salix alba L.) from the plant growth media was observed. Negligible effect of EDTA on the uptake of Cr(6+) was found, but significant decrease of the Cr concentration in roots was measured. Although the translocation of Cr(6+) within plant materials was detected in response to EDTA concentration, the amount of Cr(6+) translocated to the lower stems was considerably small. EDTA in the nutrient media showed a negative effect on the uptake of Cr(3+ )by hybrid willows; the removal rates of Cr(3+ )were significantly decreased. Translocation of Cr(3+) into the stems and leaves was undetectable, but roots were the exclusive sink for Cr(3+) accumulation. Weeping willows (Salix babylonica L.) showed lower removal rates for both chemical forms of Cr than hybrid willows. Although EDTA had a minor effect on Cr(6+ )uptake by weeping willows, positive effect on Cr(6+ )translocation within plant materials was observed. It was also determined that EDTA in plant growth media significantly decreased the amount of Cr(3+) taken up by plants, but significantly increased Cr(3+) mobilization from roots to stems. Results indicated that EDTA was unable to increase the uptake of Cr(6+) by both plant species, but translocation of Cr(6+)-EDTA within plant materials was possible. Addition of EDTA in the nutrient media showed a strong influence on the uptake and translocation of Cr(3+) in both willows. Cr(3+)-EDTA in tissues of weeping willows was more mobile than that in hybrid willows. The information has important implications for the use of metal chelator in plant nutritional research.

Fate of DTPA, EDTA, and EDDS in Hydroponic Media and Effects on Plant Mineral Nutrition

ABSTRACT Synthetic chelators are commonly used in hydroponic media to solubilize iron (Fe); however, the fate of these chelators is unknown. This study examined the persistence of three synthetic chelators, ethylenediaminetetraacetate (EDTA), diethylenetriaminepentaacetate (DTPA), and ethylenediaminedisuccinate (EDDS) in a bench-scale lettuce production system. The EDDS concentration decreased rapidly within 7d, most likely due to biodegradation. The EDTA and DTPA concentrations stayed steady throughout the experiments despite additions to maintain a constant volume and loss of chelator may have been due to either plant uptake or photodegradation of the chelator. Despite large differences in solution chemistry, the final shoot concentrations of iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn) were similar among chelator treatments, whereas root concentrations of these same elements were highly variable. The concentration of DTPA in a commercial lettuce production system was measured and highly variable concentrations were found.

Advanced Oxidation for Treatment of Aqueous Extracts from EDTA Extraction of Pb and Zn Contaminated Soil

The feasibility of using advanced oxidation processes (AOPs): ozone, ozone/sonification, and ozone/ultraviolet (UV) irradiation in treatment to remove heavy metals and ethylenediamine tetraacetate (EDTA) from aqueous extracts, obtained after soil extraction with EDTA, was examined. Extraction of soil contaminated with 1,243 mg kg−1 Pb and 1,190 mg kg−1 Zn with 40 mmol kg−1 EDTA removed 41.8±0.9 and 7.2±.0.2% of Pb and Zn. Of the AOPs tested, only the use of ozone/UV enabled the decomposition of EDTA–heavy metals complexes in aqueous soil extracts, and recovery of released Pb and Zn by sorption on a commercial sorbent Slovakite. After treatment, the concentration of Pb, Zn, and EDTA in the extracts was fairly low ( 2.87±1.15 mg L−1 , 7.58±2.12 mg L−1 , and 0.012±0.002 mmol L−1 , respectively), and could presumably be reduced even further with a continuation of treatment. The treated extract was used for subsequent soil rinsing, which removed an additional 12.7±1.6 and 2.7±0.1% of soil Pb and Zn. The result...

Attenuation of Wastewater-Derived Contaminants in an Effluent-Dominated River

Although wastewater-derived chemical contaminants undergo transformation through a variety of mechanisms, the relative importance of processes such as biotransformation and photolysis is poorly understood under conditions representative of large rivers. To assess attenuation rates under conditions encountered in such systems, samples from the Trinity River were analyzed for a suite of wastewater-derived contaminants during a period when wastewater effluent accounted for nearly the entire flow of the river over a travel time of approximately 2 weeks. While the concentration of total adsorbable organic iodide, a surrogate for recalcitrant X-ray phase contrast media in wastewater, was approximately constant throughout the river, concentrations of ethylenediamine tetraacetate, gemfibrozil, ibuprofen, metoprolol, and naproxen all decreased between 60% and 90% as the water flowed downstream. Comparison of attenuation rates estimated in the river with rates measured in laboratory-scale microcosms suggests that biotransformation was more important than photolysis for most of the compounds. Further evidence for biotransformation in the river was provided by measurements of the enantiomeric fraction of metoprolol, which showed a gradual decrease as the water moved downstream. Results of this study indicate that natural attenuation can result in significant decreases in concentrations of wastewater-derived contaminants in large rivers.