Simulation of the Mobility of Metal−EDTA Complexes in Groundwater:  The Influence of Contaminant Metals

Jc, Friedly; Kent, Douglas B.; Ja, Davis

doi:10.1021/es010926m

Cited by 41 publications

(30 citation statements)

References 33 publications

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“…Numerous field studies have shown that complexation with EDTA may mobilize contaminant metal ions. EDTA may avoid the precipitation of heavy metals in solution or, on the contrary, cause a dissolution effect of heavy metals adsorbed in sediments 7,9,10 . Hence, the result is an enhanced mobilization of heavy metals.…”

Section: Ecotoxicological Risks Of Edtamentioning

confidence: 99%

EDTA: the chelating agent under environmental scrutiny

Oviedo¹,

2003

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Recebido em 6/3/03; aceito em 28/4/03 EDTA: THE CHELATING AGENT UNDER ENVIRONMENTAL SCRUTINY. The chelating agent EDTA (ethylenediaminetetraacetic acid) is a compound of massive use world wide with household and industrial applications, being one of the anthropogenic compounds with highest concentrations in inland European waters. In this review, the applications of EDTA and its behavior once it has been released into the environment are described. At a laboratory scale, degradation of EDTA has been achieved; however, in natural environments studies detect poor biodegradability. It is concluded that EDTA behaves as a persistent substance in the environment and that its contribution to heavy metals bioavailability and remobilization processes in the environment is a major concern.

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Section: Ecotoxicological Risks Of Edtamentioning

confidence: 99%

EDTA: the chelating agent under environmental scrutiny

Oviedo¹,

2003

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“…In real soils or sediments also dissolution of aluminum and manganese phases has to be considered (Jardine et al, 1993;Friedly et al, 2002), however, AlEDTA rapidly reacts with other phases and finally Fe(III)EDTA is formed. Drainage water from soil columns (calcareous soil, pH 7.6) to which EDTA had been added was found to contain high levels of dissolved iron, presumably in the form of Fe(III)EDTA (Madrid et al, 2003).…”

Section: Addition Of Edta: Metal and Metal-ligand Leaching Below The mentioning

confidence: 99%

Root-zone modeling of heavy metal uptake and leaching in the presence of organic ligands

2004

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We present a mechanistic model which describes root uptake and leaching of heavy metals in the plant root zone, accounting for solution-and surface-complexation, (kinetic) mineral dissolution, heavy metal diffusion towards the root, root uptake, root exudation, ligand degradation and convective-dispersive transport of the soluble species. The model was used to simulate the influence of EDTA addition on Cu transport and plant uptake and the effect of oxalate exudation by roots on Cu transport and bioavailability using parameter values from the literature. In the simulations we assumed that free Cu 2+ is the bioavailable form. Under slightly acidic conditions (pH 6) the model predicted that EDTA stabilizes Cu while at a slightly alkaline pH (pH 7.5), EDTA mobilizes Cu. The addition of EDTA approximately halved the cumulative Cu uptake after 360 days at pH 4.5, and reduced the uptake by a factor of 100 and 1000 at pH 6 and 7.5, respectively. Although the total dissolved concentration was increased, plant uptake was reduced by the formation of bio-inavailable complexes. The exudation of oxalate resulted in a decrease of the Cu concentration breaking through below the root zone, due to sorption of Cu-oxalate. In the presence of dissolved organic carbon (DOC), the exudation of oxalate increased Cu leaching considerably at pH 6 and 7.5. In the absence of DOC, the exudation of oxalate reduced Cu uptake due to the formation and adsorption of Cu-oxalate on goethite surface sites. Exudation of oxalate in the presence of DOC resulted in a further decrease of Cu uptake. Oxalate gradually takes over from DOC in binding Cu due to simultaneous production of oxalate and leaching of DOC. The simulations show that addition or exudation of ligands does not necessarily increase the solubility, transport and bioavailability of metals. Depending on the conditions (mainly the pH), also reduced transport and uptake can be observed, either by formation of ternary surface complexes or reduction of free metal concentration. The model can be easily extended to include further processes.Abbreviations: DOC -dissolved organic carbon; EDTA -ethylenediaminetetraacetate; NTA -nitrilotriacetic acid.

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“…Such a peculiarity of EDTA hinders the metal recovery in form of insoluble compounds, which is the common practice for treatment of spent solutions containing heavy metal ions. Resistant to chemical and biological degradation EDTA may also be capable to dissolve Fe 3+ , Al 3+ , Ca 2+ , Mg 2+ and heavy metals in soils and sediments, facilitating their movement in the hydrological cycle [1]. In a reciprocal manner the behavior of EDTA is itself influenced by the presence of metals.…”

Section: Introductionmentioning

confidence: 99%