Potentiometric examination of ternary complexes of 2,4-D and 2,4-MCPA, components of a weedkiller, with Cu2+, Cd2+, Hg2+, Pb2+ and Zn2+, and a quantum approach to their structures
TL;DR: In this paper, the ternary interactions of some phenoxyacetic acids derived from a herbicide, with the heavy metals present in soil in trace amounts has been realized by potentiometric measurements.
Abstract: The study of the ternary interactions of some phenoxyacetic acids derived from a herbicide, with the heavy metals present in soil in trace amounts has been realized by potentiometric measurements. The stability constants of the ternary complexes have been calculated at 25°C and ionic strength 0.1(NaNO3). The experimental results have confirmed the presence of one ternary hydroxide species MH−1(2,4-D)(2,4-MCPA) for Cu(II), Pb(II) and Zn(II) on one hand and MH−2(2,4-D)(2,4-MCPA) for Hg(II) on the other. The order of stability constants has been found to be: Cu(II)>Hg(II)>Pb(N)>Zn(N)>Cd(N). Finally, a quantum approach has been achieved by the semi-empirical AM1 method for the mercuric complex.
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TL;DR: In this paper, a correlation lineaire entre l'efficacite inhibitrice obtenue experimentale-ment and the difference d'energie ΔE entre les orbitales moleculaires frontieres was found.
Abstract: L'etude experimentale de l'inhibition de la corrosion du cuivre dans le milieu nitrique par des acides amines tels que l'arginine (Arg), la cysteine (Cys), la glycine (Gly), la lysine (Lys) et la valine (Val) a ete completee par une approche theorique des equilibres de dissociation protoniques de ces acides amines a l'aide d'une methode semi- empirique: Austin Model one (AMl). Le site le plus favorable a la protonation de ces composes est l'atome d'azote du groupement amine. Une correlation lineaire entre l'efficacite inhibitrice obtenue experimentale-ment et la difference d'energie ΔE entre les orbitales moleculaires frontieres a savoir la plus haute occupee (EHOMO) et le plus basse vacante (ELUMO) a ete determinee. Cet examen a permis de constater que la cysteine est le meilleur inhibiteur de la serie des acides amines testes. En outre, le calcul des affinites protoniques et les charges atomiques nettes de la cysteine permet de mettre en evidence les groupements fonctionnels de la Cysteine (NH3+, SH, COOH) qui participent aux phenomenes de complexation Cu (II)/Cys a la surface du cuivre.
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TL;DR: Safety assessment for drinking water is conducted by allocating health-based guidelines for exposure through this environmental medium, and the tolerable daily intake (TDI) approach is used by WHO in the case of pesticides with assumed thresholds of effect, while low-dose extrapolation is used in the cases of non-threshold carcinogens.
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TL;DR: Several basic processes determining the pesticide interception by grassed strip and numerical models necessary to integrate the complexity of interacting processes and formulate reliable managing guidelines are analyzed.
Abstract: Grassed buffer strips are one way to reduce pesticide transfer by surface runoff from farmed fields to streams. Numerous experimental studies have demonstrated that this type of development is very effective in various conditions. The results are nevertheless very variable. This variability is partially explained by the multiplicity of processes and contributive factors and by the fact that the latter are dynamic in nature and site-specific. Several results also show that the intercepted products are not systematically immobilized within the strip but can move in the subsurface, thus affecting the overall effectiveness of the system. As a consequence of this complexity, the present guidelines for the sizing and siting of grassed strips are still only qualitative or are the result of empirical approaches. The present review analyses the available results and defines needs for further research. This concerns several basic processes determining the pesticide interception by grassed strip and numerical models necessary to integrate the complexity of interacting processes and formulate reliable managing guidelines.
124 citations
"Potentiometric examination of terna..." refers background in this paper
...During the last years, it has been noticed that the increasing use of pesticides in soils used forcultivation causes pollution of the aqueous system by infiltration of irrigation or rainwater (Younes et al., 2000; Lacas et al., 2005)....
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TL;DR: The adsorption of 2,4-dichlorophenoxyacetic acid by two powdered coal activated carbons was studied in aqueous solution and it was found to decrease with an increase in pH over the range 1.5-9.5 and to depend on the NaCl concentration.
Abstract: The adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) by two powdered coal activated carbons was studied in aqueous solution. The modelling of the adsorption equilibrium showed that the adsorption of 2,4-D fitted a Langmuir isotherm. Adsorption was influenced by the activated carbon type, adsorbent concentration and solution characteristics. The adsorption was found to decrease with an increase in pH over the range 1.5–9. Maximum adsorption occurred at pH ≈ 2.5, which corresponds to the 2,4-D pKa value. The amount of 2,4-D adsorbed was also found to depend on the NaCl concentration.
42 citations