1
|
Salta Z, Kosmas AM, Ventura ON. Kinetics and thermodynamics of the hydroxylation products in the photodegradation of the herbicide Metolachlor. PURE APPL CHEM 2020. [DOI: 10.1515/pac-2018-1205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
Electronic structure calculations have been performed to determine the thermochemistry and kinetics of the reaction between OH and the radicals of the S enantiomer of the herbicide Metolachlor, 2-chloro-N-(2-methyl-6-ethylphenyl)-N(2-methoxy-1-methylethyl) acetamide (MC), produced by photoinduced breaking of the C–Cl bond. Both density functional and ab initio composite methods were employed to calculate the structure of reactants, intermediates, transition states and products, in gas phase and in aqueous solution. The expected relative abundance of each product was calculated and compared to the experimentally observed concentrations. It is shown that a combination of thermodynamic and kinetic characteristics interplay to produce the expected theoretical abundances, which turn out to be in agreement with the experimentally observed distribution of products.
Collapse
Affiliation(s)
- Zoi Salta
- SMART Lab, Scuola Normale Superiore di Pisa , Piazza dei Cavalieri, 7, 56126 Pisa , Italy
| | - Agnie M. Kosmas
- Physical Chemistry Sector, Department of Chemistry , University of Ioannina , Ioannina 45110 , Greece
| | - Oscar N. Ventura
- Computational Chemistry and Biology Group, CCBG, DETEMA, Facultad de Química, Udelar , Montevideo , Uruguay
| |
Collapse
|
2
|
Thiam A, Salazar R. Fenton-based electrochemical degradation of metolachlor in aqueous solution by means of BDD and Pt electrodes: influencing factors and reaction pathways. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2019; 26:2580-2591. [PMID: 30474812 DOI: 10.1007/s11356-018-3768-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Accepted: 11/14/2018] [Indexed: 06/09/2023]
Abstract
This work explores the role of electrode material and the oxidation ability of electrochemical advanced oxidation processes (EAOPs), such as electro-oxidation (EO) with or without H2O2 production, electro-Fenton (EF), and UVA photoelectron-Fenton (PEF), in the degradation of metolachlor. The performance of the EAOPs using Boron-doped diamond (BDD) or Pt as anode has been compared from the analysis of decay kinetics, mineralization profile, and energy consumption using small undivided batch cell. Metolachlor concentration always decays following a pseudo-first-order kinetics. Using the Pt anode, none of the processes reaches 30% mineralization, including PEF. In contrast, the BDD anode showed a higher mineralization rate allowing almost total mineralization in PEF due to the synergetic action of UVA light and oxidant hydroxyl radicals formed in the bulk from Fenton's reaction, as well as in the BDD, which has large reactivity to oxidize the pollutants. The increase in current density and decrease in metolachlor concentration accelerated the mineralization in PEF, although lower current efficiency and higher energy consumption was obtained. The GC-MS and HPLC analysis allowed the identification of up to 17 aromatics intermediates and 7 short-chain carboxylic acids. Finally, a reaction pathway for metolachlor mineralization by EAOPs is proposed. PEF with BDD allowed total removal of the herbicide in real water matrix and a high mineralization (83.82%).
Collapse
Affiliation(s)
- Abdoulaye Thiam
- Programa Institucional de Fomento a la I+D+i, Universidad Tecnológica Metropolitana, Ignacio Valdivieso 2409, P.O. Box 8940577, San Joaquín, Santiago, Chile.
| | - Ricardo Salazar
- Laboratorio de Electroquímica del MedioAmbiente, LEQMA, Facultad de Química y Biología, Universidad de Santiago de Chile, USACh, Casilla 40, Correo, 33, Santiago, Chile
| |
Collapse
|
3
|
Salta Z, Kosmas AM, Ventura ON. Computational characterization of the herbicide metolachlor and its mono-hydroxylated photodegradation products. Theor Chem Acc 2018. [DOI: 10.1007/s00214-018-2353-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
|
4
|
Nicol É, Genty C, Bouchonnet S, Bourcier S. Structural elucidation of metolachlor photoproducts by liquid chromatography/high-resolution tandem mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2015; 29:2279-2286. [PMID: 26522321 DOI: 10.1002/rcm.7382] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Revised: 08/24/2015] [Accepted: 08/30/2015] [Indexed: 06/05/2023]
Abstract
RATIONALE Metolachlor is one of the most intensively used chloroacetanilide herbicides in agriculture. It has been detected in water; consequently, under UV-visible irradiation, it can be transformed in degradation products (TPs). The structures of TPs were elucidated by liquid chromatography/high-resolution tandem mass spectrometry (LC/HR-MS/MS). The potential toxicities of these TPs were estimated by in silico tests. METHODS Aqueous solutions of metolachlor were irradiated in a self-made reactor equipped with a mercury vapor lamp. Analyses were carried out using high-performance liquid chromatography coupled to quadrupole time-of-flight (QTOF) mass spectrometer. High-resolution m/z measurements, MS/MS and isotopic labeling experiments allowed structural elucidation of metolachlor TPs. Their toxicities were estimated in silico, using the T.E.S.T. RESULTS Ten major metolachlor photoproducts were characterized by LC/MS/MS after irradiation of metolachlor in aqueous solution. Elucidation of their chemical structures was identified using high-resolution measurements and MS/MS experiments. They resulted from the combination of dehalogenation, hydroxylation and cyclisation processes. The potential oral rat lethal dose (LD50) was assessed with QSAR tests for metolachlor and each photoproduct. Results indicate that most of the TPs are much more toxic than metolachlor. CONCLUSIONS UV-vis irradiation of metolachlor in aqueous solution leads to the formation of ten photoproducts. QSAR estimations show that the location of added hydroxyl group(s) is of key relevance as regards to biological activity and that routine water analysis should take into account the TPs are more toxic than the parent molecule.
Collapse
Affiliation(s)
- Édith Nicol
- École Polytechnique, Laboratoire de Chimie Moléculaire, UMR 9168 CNRS, route de Saclay, 91128, Palaiseau cedex, France
| | - Christophe Genty
- École Polytechnique, Laboratoire de Chimie Moléculaire, UMR 9168 CNRS, route de Saclay, 91128, Palaiseau cedex, France
| | - Stéphane Bouchonnet
- École Polytechnique, Laboratoire de Chimie Moléculaire, UMR 9168 CNRS, route de Saclay, 91128, Palaiseau cedex, France
| | - Sophie Bourcier
- École Polytechnique, Laboratoire de Chimie Moléculaire, UMR 9168 CNRS, route de Saclay, 91128, Palaiseau cedex, France
| |
Collapse
|
5
|
Gutowski L, Baginska E, Olsson O, Leder C, Kümmerer K. Assessing the environmental fate of S-metolachlor, its commercial product Mercantor Gold® and their photoproducts using a water-sediment test and in silico methods. CHEMOSPHERE 2015; 138:847-855. [PMID: 26299980 DOI: 10.1016/j.chemosphere.2015.08.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Revised: 07/23/2015] [Accepted: 08/06/2015] [Indexed: 06/04/2023]
Abstract
Pesticides enter surface and groundwater by several routes in which partition to sediment contributes to their fate by abiotic (e.g. photolysis, hydrolysis) and biotic processes. Yet, little is known about S-metolachlor (SM) transformation in water-sediment systems. Therefore, a newly developed screening water-sediment test (WST) was applied to compare biodegradation and sorption processes between pure SM and Mercantor Gold® (MG), a commercial formulation of SM. Photolysis in water was performed by Xe lamp irradiation. Subsequently, the biodegradability of SM and MG photolysis mixtures was examined in WST. The primary elimination of SM from water phase was monitored and structures of its TPs resulting from biotransformation (bio-TPs) were elucidated by LC-MS/MS. SM was extracted from sediment in order to estimate the role of sorption in WST for its elimination. A set of in silico prediction software tools was applied for toxicity assessment of SM and its bio-TPs. Obtained results suggest that the MG adjuvants do not significantly affect biodegradation, but do influence diffusion of SM into sediment. 50% of SM could not be re-extracted from sediment with 0.01 M CaCl2 aqueous solution recommended in OECD test guideline for adsorption. Neither the parent compound nor the photo-TPs were biodegraded. However, new bio-TPs have been generated from SM and MG photo-TPs due to bacterial activity in the water-sediment interphase. Moreover, according to in silico assessment of the bio-TPs the biotransformation might lead to an increased toxicity to the water organisms compared with the SM. This might raise concerns of bio-TPs presence in the environment.
Collapse
Affiliation(s)
- Lukasz Gutowski
- Sustainable Chemistry and Material Resources, Institute of Sustainable and Environmental Chemistry, Leuphana University Lüneburg, C13, DE - 21335 Lüneburg, Germany.
| | - Ewelina Baginska
- Sustainable Chemistry and Material Resources, Institute of Sustainable and Environmental Chemistry, Leuphana University Lüneburg, C13, DE - 21335 Lüneburg, Germany.
| | - Oliver Olsson
- Sustainable Chemistry and Material Resources, Institute of Sustainable and Environmental Chemistry, Leuphana University Lüneburg, C13, DE - 21335 Lüneburg, Germany.
| | - Christoph Leder
- Sustainable Chemistry and Material Resources, Institute of Sustainable and Environmental Chemistry, Leuphana University Lüneburg, C13, DE - 21335 Lüneburg, Germany.
| | - Klaus Kümmerer
- Sustainable Chemistry and Material Resources, Institute of Sustainable and Environmental Chemistry, Leuphana University Lüneburg, C13, DE - 21335 Lüneburg, Germany.
| |
Collapse
|
6
|
Gutowski L, Olsson O, Leder C, Kümmerer K. A comparative assessment of the transformation products of S-metolachlor and its commercial product Mercantor Gold(®) and their fate in the aquatic environment by employing a combination of experimental and in silico methods. THE SCIENCE OF THE TOTAL ENVIRONMENT 2015; 506-507:369-379. [PMID: 25460972 DOI: 10.1016/j.scitotenv.2014.11.025] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Revised: 11/05/2014] [Accepted: 11/05/2014] [Indexed: 06/04/2023]
Abstract
Even appropriately used, pesticides can enter the surface and groundwater by several routes where photochemical degradation along with biotic processes contributes to their fate, resulting sometimes in the formation of stable transformation products (TPs). Yet, little is known about S-metolachlor (SM) transformation in the aquatic environment. Furthermore, commercial formulation of a pesticide might have different physical and biological properties compared to its pure grade. The present study assessed the biodegradability of the pure SM and its commercial product Mercantor Gold(®) (MG) by employing two OECD biodegradation (301D, F) tests. Photolysis in water was investigated by using a Xe lamp. Subsequently the biodegradability of the photolysis mixtures was examined. The primary elimination of SM was monitored and structures of its TPs were elucidated by HPLC-UV-MS/MS. Additionally, a set of in silico prediction programs was applied for supporting analytical results and toxicity assessment of SM and TPs. S-metolachlor and Mercantor Gold(®) were not biodegraded. HPLC-UV analysis showed higher elimination of SM in MG compared to pure SM during photolysis. A total of 10 photo-TPs of SM and MG were identified. According to MS data and in silico predictions, chemical structures were proposed for all found photo-TPs. Likewise for the parent compounds, no biodegradation has been observed for their photo-TPs. However, in the 301F test new bio-TPs have been generated from photo-TPs which were observed for the first time according to authors' best knowledge. The results suggest that the MG formulation does not affect the biodegradation process, but it influences the photolysis efficiency and potentially might result in faster formation of TPs in the environment. This study also demonstrates that photo-TPs can be further transformed into new products due to bacterial activity in the water phase. Moreover biotransformation might lead to an increased toxicity compared with the parent compound.
Collapse
Affiliation(s)
- Lukasz Gutowski
- Sustainable Chemistry and Material Resources, Institute of Sustainable and Environmental Chemistry, Leuphana University Lüneburg, C13, DE-21335 Lüneburg, Germany.
| | - Oliver Olsson
- Sustainable Chemistry and Material Resources, Institute of Sustainable and Environmental Chemistry, Leuphana University Lüneburg, C13, DE-21335 Lüneburg, Germany.
| | - Christoph Leder
- Sustainable Chemistry and Material Resources, Institute of Sustainable and Environmental Chemistry, Leuphana University Lüneburg, C13, DE-21335 Lüneburg, Germany.
| | - Klaus Kümmerer
- Sustainable Chemistry and Material Resources, Institute of Sustainable and Environmental Chemistry, Leuphana University Lüneburg, C13, DE-21335 Lüneburg, Germany.
| |
Collapse
|
7
|
Remucal CK. The role of indirect photochemical degradation in the environmental fate of pesticides: a review. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2014; 16:628-53. [PMID: 24419250 DOI: 10.1039/c3em00549f] [Citation(s) in RCA: 119] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Photochemical degradation contributes to the environmental fate of many pesticides in surface waters. A better understanding of the role of direct and indirect photochemical degradation of pesticides is necessary in order to predict their environmental fate and persistence. This review includes all major pesticide classes and focuses on the importance of dissolved organic matter (DOM) as a sensitizer in indirect photodegradation within aquatic systems. Photochemical studies conducted under environmentally relevant conditions (i.e., aqueous solutions with irradiation wavelengths >290 nm) are included. Comparisons are made between observed photodegradation rates in pure or buffered water and in water containing DOM to assess the extent of pesticide susceptibility to DOM-sensitized indirect photolysis. When data is available, the role of specific reactive species in indirect photodegradation is described. While it is possible to assess the relative importance of direct and indirect photodegradation on a pesticide-by-pesticide basis in many cases, it is often difficult to make generalizations based on compound class. Knowledge gaps and inconstancies in the current body of literature are discussed and areas that require additional research are described.
Collapse
Affiliation(s)
- Christina K Remucal
- University of Wisconsin-Madison, Department of Civil and Environmental Engineering, 660 N. Park St., Madison, WI, USA.
| |
Collapse
|
8
|
Kinani A, Rifai A, Bourcier S, Jaber F, Bouchonnet S. Structural characterization of photoproducts of pyrimethanil. JOURNAL OF MASS SPECTROMETRY : JMS 2013; 48:983-987. [PMID: 23893647 DOI: 10.1002/jms.3244] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Revised: 05/24/2013] [Accepted: 05/25/2013] [Indexed: 06/02/2023]
|
9
|
Souissi Y, Bouchonnet S, Bourcier S, Kusk KO, Sablier M, Andersen HR. Identification and ecotoxicity of degradation products of chloroacetamide herbicides from UV-treatment of water. THE SCIENCE OF THE TOTAL ENVIRONMENT 2013; 458-460:527-34. [PMID: 23707723 DOI: 10.1016/j.scitotenv.2013.04.064] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2012] [Revised: 04/21/2013] [Accepted: 04/22/2013] [Indexed: 05/22/2023]
Abstract
The widespread occurrence of chlorinated herbicides and their degradation products in the aquatic environment raises health and environmental concerns. As a consequence pesticides, and to a lesser degree their degradation products, are monitored by authorities both in surface waters and drinking waters. In this study the formation of degradation products from ultraviolet (UV) treatment of the three chloroacetamide herbicides acetochlor, alachlor and metolachlor and their biological effects were investigated. UV treatment is mainly used for disinfection in water and wastewater treatments. First, the chemical structures of the main UV-degradation products were identified using gas chromatography coupled with mass spectrometry and liquid chromatography-mass spectrometry. The main transformation reactions were dechlorination, mono- and multi-hydroxylation and cyclizations. The ecotoxicity of the mixed photoproducts formed by UV-treatment until 90% of the original pesticide was converted was compared to the toxicity of chloroacetamides using the green alga Pseudokirchneriella subcapitata, the crustacean Daphnia magna and the marine bacteria Vibrio fischeri as test organisms. UV-treatment of alachlor and metolachlor increased the toxicity compared to the parent compounds while an equal toxicity was found for photolysis products of acetochlor. This suggests that toxic photodegradation products are generated from chloroacetamides under UV-treatment. An important perspective of this finding is that the photolysis products are at least as toxic as the parent compounds.
Collapse
Affiliation(s)
- Yasmine Souissi
- Ecole Polytechnique, Laboratoire des Mécanismes Réactionnels, CNRS, route de Saclay, 91128 Palaiseau cedex, France
| | | | | | | | | | | |
Collapse
|
10
|
Rifai A, Souissi Y, Genty C, Clavaguera C, Bourcier S, Jaber F, Bouchonnet S. Ultraviolet degradation of procymidone--structural characterization by gas chromatography coupled with mass spectrometry and potential toxicity of photoproducts using in silico tests. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2013; 27:1505-1516. [PMID: 23722685 DOI: 10.1002/rcm.6598] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Revised: 04/09/2013] [Accepted: 04/11/2013] [Indexed: 06/02/2023]
Abstract
RATIONALE Procymidone is a dicarboximide fungicide mainly used for vineyard protection but also for different crops. The structural elucidation of by-products arising from the UV-visible photodegradation of procymidone has been investigated by gas chromatography coupled with mass spectrometry. The potential toxicities of photoproducts were estimated by in silico tests. METHODS Aqueous solutions of procymidone were irradiated for up to 90 min in a self-made reactor equipped with a mercury lamp. Analyses were carried out on a gas chromatograph coupled with an ion trap mass spectrometer operated in electron ionization and methanol positive chemical ionization. Multistage collision-induced dissociation (CID) experiments were performed to establish dissociation pathways of ions. Toxicities of byproducts were estimated using the QSAR T.E.S.T. program. RESULTS Sixteen photoproducts were investigated. Chemical structures were proposed mainly based on the interpretation of multistage CID experiments, but also on their relative retention times and kinetics data. These structures enabled photodegradation pathways to be suggested. Only three photoproducts remain present after 90 min of irradiation. Among them, 3,5-dichloroaniline presents a predicted rat LD50 toxicity about ten times greater than that of procymidone. CONCLUSIONS 3,5-Dichloroaniline is the only photoproduct reported in previous articles. Eight by-products among the sixteen characterized might be as toxic, if not more, than procymidone itself considering the QSAR-predicted rat LD50.
Collapse
Affiliation(s)
- Ahmad Rifai
- Laboratoire des Mécanismes Réactionnels UMR-7651, Ecole Polytechnique, Palaiseau, France
| | | | | | | | | | | | | |
Collapse
|