Photodegradation of pesticides in the presence of humic substances

Jensen-Korte, Uta; Anderson, C.; Spiteller, Michael

doi:10.1016/0048-9697(87)90518-3

Cited by 49 publications

(28 citation statements)

References 3 publications

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“…It is possible that EA photolysis occurs at more than one wavelength range. Solar radiation reaching the earth's surface having a wider wavelength range (290 -> 800 nm) spanning through the wavelengths of UV-B, UV-A and visible light up to the infrared region (Zepp and Cline, 1977;Zepp et al, 1985;Jensen-Korte et al, 1987;Niu et al, 2004;Katagi, 2004) may provide better chance for EA photolysis. In this study, we did not diagnose what wavelength component of the solar radiation was most important or responsible for the rapid photo-degradation of EA.…”

Section: Discussionmentioning

confidence: 97%

Potential environmental fate of elsinochrome A, a perylenequinone toxin produced in culture by bindweed biocontrol fungus Stagonospora convolvuli LA39

et al. 2006

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The photosensitizing perylenequinone toxin elsinochrome A (EA) is produced in culture by the bindweed biocontrol fungus Stagonospora convolvuli LA39 where it apparently plays a pathogenicity related role. We investigated the fate of EA with reference to its stability under different temperature and light conditions. EA remained stable when boiled in water at 100°C for 2 h. Similarly, exposing EA to 3-27°C in the dark for up to 16 weeks did not affect its stability either in dry or in aqueous form. However, results from irradiation experiments indicate that direct photolysis may be a significant degradation pathway for EA in the environment. EA either in dry form or dissolved in water was degraded by different irradiation wavelengths and intensities, with degradation plots fitting a first order rate kinetics. EA degraded faster if exposed in aqueous form, and at higher quantum flux density (jsmol s F m-2). Sunlight was more effective in degrading EA than artificial white light and ultraviolet radiations (UV-A or UV-B). Exposing EA to natural sunlight, particularly, during the intense sunshine (1,420-1,640 ismol s 2) days of 30

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Section: Discussionmentioning

confidence: 97%

Potential environmental fate of elsinochrome A, a perylenequinone toxin produced in culture by bindweed biocontrol fungus Stagonospora convolvuli LA39

et al. 2006

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“…It can be concluded that humic substances are able to transform a great variety of organic substrates through the influence of solar-light. The ecological impact of the absorption of light by humic substances is difficult to evaluate however it should participate significantly to the auto-purification of superficial waters [9][10][11].…”

Section: Resultsmentioning

confidence: 99%

Effect of light on humic substances : production of reactive species

Aguer¹,

Richard²,

Andreux³

1999

Analusis

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Humic substances (HS) absorb photons in the UV and the visible region of the solar spectrum up to 500 nm. The energy absorbed in this way lies within the range 58 -98 kJ mol -1 making a number of photochemical processes possible. In particular, reactive species capable of transforming a great variety of organic compounds can be produced. The continuing interest in the photochemical behavior of humic substances is due to their ability to act as depolluting agents by photoinducing the degradation of pollutants.Here, we report the identification of some reactive species generated by the photochemical excitation of humic substances, the characterization being mainly based on the scavenging and probe molecule techniques. We also present the influence of irradiation wavelength, pH value and concentration of oxygen on the photoinductive properties of humic substances. Exemples of photoinduced degradation of pollutants are given. Experimental sectionHumic and fulvic acids were purchased either from International Humic Substances Society (IHSS) or were extracted from different soils using a standard procedure [1]. Soils were sampled at three locations: A h horizon from a Mountain Ranker soil under grassland, B h horizon from a Mountain Podzol under pine and heather, and A p horizon from a cultivated brown leached soil. Experiments were also performed with Aldrich humic acids and humic acids synthetized from phenol [2]. Substrates were of the highest grade commercially available. Samples were prepared by solubilizing humic substances (10 to 100 mg L -1 ) in distilled water buffered at pH = 6.5 with phosphates. Solutions were filtered on 0.45 µm Millipore filters then irradiated at 253.7 and 365 nm using germicidal and "black-light" lamps respectively. Irradiation was also conducted using polychromatic lamps (300 -450 nm). Solutions were then analysed by High Performance Liquid Chromatography using a Waters chromatograph equipped with a photodiode array detector and a reverse-phase column (Merck Lichrospher; 250 mm × 3.9 mm; column packing, C 18 , 5 µm). Mixtures methanol-water in proportion depending of the substrate tested were used as eluents at a flow of 1 mL/min. The chloride ions released in the phototransformations of dichloromethane and 3-(4'-chloro-phenyl)-1,1-dimethylurea (monuron) were titrated with a chloride specific electrode Orion. Results and discussion Solvated electronsThe formation of solvated electrons was observed by laserflash photolysis of humic and fulvic acids solutions [3]. These species are likely to result from the photoionization of phenolic moieties of humic substances because such a reaction is known to occur with phenols and phenolate anions [4]. At first, solutions of humic substances were irradiated at short wavelength (253.7 nm) using dichloromethane (2 × 10 -2 M) as substrate. The release of chloride ions was observed during irradiation. This finding shows that humic substances are able to photoinduce reductions. The quantum yield Φ of chloride formation which is defined as the ratio bet...

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“…Les substances humiques sont parmi les principaux composants des sols susceptibles d'absorber la lumière solaire dans les milieux aquatiques et terrestres naturels (Jensen-Korte et al, 1987;Aguer et al, 1996;Vulliet et al, 2001;Maneger et al, 2009;Tajeddine et al, 2008Tajeddine et al, , 2010. Sous l'effet des radiations ultraviolet, elles peuvent être totalement dégradées et en même temps augmenter (Kamiya et al, 1998;Hustert et al, 1999) ou empêcher (Wang et al, 1995;Bachmann et al, 1999) la photodécomposition des polluants organiques.…”

Section: Introductionunclassified

Etude des capacités photodégradantes des substances humiques naturelles extraites de deux sols cultivables du Togo

Koriko¹,

Zonvide²,

Tchangbédji³

et al. 2011

International Journal of Biological and Chemical Sciences

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RESUMESous l'effet de la lumière, les substances humiques peuvent avoir des aptitudes à dégrader les polluants organiques. Il peut se former ainsi des états excités, des oxygènes singulet ( 1 O 2 ), des radicaux peroxyde (RO 2 . ), (HO 2 . /O 2 .-) et hydroxyle (OH . ) ou encore des électrons solvatés (e -aq ) intervenant dans la dégradation des polluants organiques. Ces réactions interviennent dans l'environnement aquatique et à la surface des sols. Au cours de cette étude, nous nous sommes intéressés aux propriétés photodégradantes des acides humiques extraits de deux sols cultivables du Togo. A cet effet, nous avons utilisé les solutions aqueuses d'un tampon phosphate à pH = 6,5. L'objectif de ce travail a été donc, d'évaluer et de comprendre les propriétés photosensibilisatrices des acides humiques et notamment les rôles de quelques espèces réactives. La première étape de cette étude fut la réactivité photochimique des acides humiques avec une molécule modèle (2,6-diméthylphénol). La deuxième étape a consisté à utiliser le 2,4,6-triméthylphénol pour caractériser des états excités à caractère triplet ; l'acide téréphtalique pour la mise en évidence des radicaux hydroxyles et l'alcool furfurylique pour caractériser les oxygènes singulet. Le 2,6-diméthylphénol utilisé comme molécule modèle nous a prouvé les capacités photodégradantes de ces substances humiques. L'utilisation des molécules sondes a montré la formation des espèces réactives comme les oxygènes singulet, les états excités à caractère triplet et les radicaux hydroxyles. D'autres espèces pourraient être présentes.

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Photodegradation of pesticides in the presence of humic substances

Cited by 49 publications

References 3 publications

Potential environmental fate of elsinochrome A, a perylenequinone toxin produced in culture by bindweed biocontrol fungus Stagonospora convolvuli LA39

Potential environmental fate of elsinochrome A, a perylenequinone toxin produced in culture by bindweed biocontrol fungus Stagonospora convolvuli LA39

Effect of light on humic substances : production of reactive species

Etude des capacités photodégradantes des substances humiques naturelles extraites de deux sols cultivables du Togo

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