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Liu H, Liu M, Zong X, Liu A, Yuan M, Fang S. Mechanism of safener mefenpyr-diethyl biodegradation by a newly isolated Chryseobacterium sp. B6 from wastewater sludge and application in co-contaminated soil. Chemosphere 2023; 345:140385. [PMID: 37839750 DOI: 10.1016/j.chemosphere.2023.140385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 07/14/2023] [Accepted: 10/06/2023] [Indexed: 10/17/2023]
Abstract
Safener mefenpyr-diethyl (MFD) was applied to cereal crops along with herbicides to improve herbicide selectivity for crops and weeds. However, the degradation mechanism of MFD in the environment remains unclear. One MFD-degrading bacterium, Chryseobacterium sp. B6, was isolated from activated sludge. According to Box-Behnken's optimal design, the degradation efficiency of MFD can reach 92% under conditions of pH 7.5, 30 °C, and a MFD concentration of 184 mg L-1. The degradation half-life experiment showed that a high concentration of MFD (300 mg L-1) inhibited the degradation ability of strain B6. Additionally, strain B6 was resistant to Ba2+, Cr3+, Li+, Zn2+, and Cu2+. The MFD degradation products of strain B6 were detected by GC/MS and its degradation pathway was proposed. MFD was first hydrolyzed by a hydrolase to an intermediate (RS)-1-(2,4-dichlorophenyl)-5-methyl-2-pyrazoline-5-carboxylic acid ethyl ester-3-carboxylic acid, and then further degraded by a decarboxylase to form the intermediate (RS)-1-(2,4-dichlorophenyl)-5-methyl-2-pyrazoline-5-carboxylic acid ethyl ester, finally, it is completely degraded by strain B6. Furthermore, strain B6 could effectively remove MFD from MFD-contaminated soil, and the half-life of MFD was also significantly reduced in MFD and Cu2+ co-contaminated soil after inoculating strain B6. To our knowledge, strain B6 was the first strain reported to degrade safener MFD, and this study provides a valuable candidate to remediate the co-contaminated soil with MFD and Cu2+.
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Affiliation(s)
- Hongming Liu
- Anhui Provincial Key Laboratory of Molecular Enzymology and Mechanism of Major Diseases, Anhui Normal University, Wuhu, 241000, PR China; Anhui Provincial Key Laboratory of the Conservation and Exploitation of Biological Resources, Anhui Normal University, Wuhu, 241000, PR China.
| | - Mengna Liu
- Anhui Provincial Key Laboratory of Molecular Enzymology and Mechanism of Major Diseases, Anhui Normal University, Wuhu, 241000, PR China; Anhui Provincial Key Laboratory of the Conservation and Exploitation of Biological Resources, Anhui Normal University, Wuhu, 241000, PR China
| | - Xuan Zong
- Anhui Provincial Key Laboratory of Molecular Enzymology and Mechanism of Major Diseases, Anhui Normal University, Wuhu, 241000, PR China; Anhui Provincial Key Laboratory of the Conservation and Exploitation of Biological Resources, Anhui Normal University, Wuhu, 241000, PR China
| | - Aimin Liu
- Anhui Provincial Key Laboratory of Molecular Enzymology and Mechanism of Major Diseases, Anhui Normal University, Wuhu, 241000, PR China; Anhui Provincial Key Laboratory of the Conservation and Exploitation of Biological Resources, Anhui Normal University, Wuhu, 241000, PR China
| | - Meng Yuan
- Anhui Provincial Key Laboratory of Molecular Enzymology and Mechanism of Major Diseases, Anhui Normal University, Wuhu, 241000, PR China; Anhui Provincial Key Laboratory of the Conservation and Exploitation of Biological Resources, Anhui Normal University, Wuhu, 241000, PR China
| | - Shangping Fang
- School of Anesthesiology, Wannan Medical College, Wuhu, Anhui, 241002, PR China.
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2
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Femi-Oloye OP, Oloye FF, Jones PD, Giesy JP. Sorption behaviour and toxicity of an herbicide safener "cyprosulfamide". Sci Total Environ 2023; 859:160077. [PMID: 36372173 DOI: 10.1016/j.scitotenv.2022.160077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 11/01/2022] [Accepted: 11/05/2022] [Indexed: 06/16/2023]
Abstract
Cyprosulfamide is a herbicide safener that works against the injurious effects of herbicides such as isoxaflutole, dicamba, nicosulfuron, tembotrione, thiencarbazone-methyl. However, its sorption behaviour in soils and toxicity to aquatic organisms are yet to be thoroughly examined. This study determined the octanol-water partition coefficient, sorption properties, acute and chronic toxic effects, and potency of cyprosulfamide to the cladoceran water flea (Daphnia magna). The influence of soil properties such as organic carbon content, cation exchange capacity, pH, and field capacity on adsorption and desorption properties were also examined. The Log Kow (0.55) of cyprosulfamide was less than that of some other safeners, such as benoxacor or furilazole, found in aquatic environments. The sorption of cyprosulfamide to the soil was driven by pH, so sorption decreased with an increase in pH. Other characteristics, such as cation exchange capacity (CEC), organic carbon content, and field capacity, do not directly correlate with the distribution coefficient. Cyprosulfamide generally has a low affinity for soil and is thus mobile and prone to transport to surrounding surface waters. No lethality was observed at the highest concentration (120 mg/L) tested for acute toxicity to D. magna; hence the LC50 will be >120 mg/L. During chronic exposures, cyprosulfamide caused adverse effects at a concentration of 120 mg/L on the number of neonates and brood size. The death rate for the chronic study was a function of concentration and increased with days of exposure. Cyprosulfamide is unlikely to cause lethality to D. magna at relevant environmental concentrations.
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Affiliation(s)
- O P Femi-Oloye
- Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B3, Canada.
| | - F F Oloye
- Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B3, Canada.
| | - P D Jones
- Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B3, Canada; School of Environment and Sustainability, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B3, Canada.
| | - J P Giesy
- Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B3, Canada; Department of Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B3, Canada; Department of Integrative Biology, Center for Integrative Toxicology, Michigan State University, 1129 Farm Lane Road, East Lansing, MI, USA; Department of Environmental Sciences, Baylor University, Waco, TX 76706, USA.
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3
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McFadden M, Reber KP, Sivey JD, Cwiertny DM, LeFevre GH. Microbial Biotransformation Products and Pathways of Dichloroacetamide Herbicide Safeners. Environ Sci Technol Lett 2023; 10:72-78. [PMID: 37091899 PMCID: PMC10111411 DOI: 10.1021/acs.estlett.2c00862] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Accepted: 11/29/2022] [Indexed: 05/03/2023]
Abstract
Dichloroacetamide safeners are common ingredients in commercial herbicide formulations. We previously investigated the environmental fate of dichloroacetamides via photolysis and hydrolysis, but other potentially important, environmentally relevant fate processes remain uncharacterized and may yield products of concern. Here, we examined microbial biotransformation of two dichloroacetamide safeners, benoxacor and dichlormid, to identify products and elucidate pathways. Using aerobic microcosms inoculated with river sediment, we demonstrated that microbial biotransformations of benoxacor and dichlormid proceed primarily, if not exclusively, via cometabolism. Benoxacor was transformed by both hydrolysis and microbial biotransformation processes; in most cases, biotransformation rates were faster than hydrolysis rates. We identified multiple novel products of benoxacor and dichlormid not previously observed for microbial processes, with several products similar to those reported for structurally related chloroacetamide herbicides, thus indicating potential for conserved biotransformation mechanisms across both chemical classes. Observed products include monochlorinated species such as the banned herbicide CDAA (from dichlormid), glutathione conjugates, and sulfur-containing species. We propose a transformation pathway wherein benoxacor and dichlormid are first dechlorinated, likely via microbial hydrolysis, and subsequently conjugated with glutathione. This is the first study reporting biological dechlorination of dichloroacetamides to yield monochlorinated products in aerobic environments.
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Affiliation(s)
- Monica
E. McFadden
- Department
of Civil and Environmental Engineering, University of Iowa, 4105 Seamans Center for the Engineering Arts and Sciences, Iowa City, Iowa 52242, United States
- IIHR-Hydroscience
and Engineering, University of Iowa, 100 C. Maxwell Stanley Hydraulics
Laboratory, Iowa City, Iowa 52242, United States
| | - Keith P. Reber
- Department
of Chemistry, Towson University, Towson, Maryland 21252, United States
| | - John D. Sivey
- Department
of Chemistry, Towson University, Towson, Maryland 21252, United States
| | - David M. Cwiertny
- Department
of Civil and Environmental Engineering, University of Iowa, 4105 Seamans Center for the Engineering Arts and Sciences, Iowa City, Iowa 52242, United States
- IIHR-Hydroscience
and Engineering, University of Iowa, 100 C. Maxwell Stanley Hydraulics
Laboratory, Iowa City, Iowa 52242, United States
- Center
for Health Effects of Environmental Contamination (CHEEC), University of Iowa, 251 North Capitol St., Chemistry Building, Room W195, Iowa City, Iowa 52242, United States
- Public
Policy Center, University of Iowa, 310 South Grand Ave., 209 South
Quadrangle, Iowa City, Iowa 52242, United States
| | - Gregory H. LeFevre
- Department
of Civil and Environmental Engineering, University of Iowa, 4105 Seamans Center for the Engineering Arts and Sciences, Iowa City, Iowa 52242, United States
- IIHR-Hydroscience
and Engineering, University of Iowa, 100 C. Maxwell Stanley Hydraulics
Laboratory, Iowa City, Iowa 52242, United States
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4
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Xu X, Gujarati PD, Okwor N, Sivey JD, Reber KP, Xu W. Reactivity of chloroacetamides toward sulfide + black carbon: Insights from structural analogues and dynamic NMR spectroscopy. Sci Total Environ 2022; 803:150064. [PMID: 34525700 DOI: 10.1016/j.scitotenv.2021.150064] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 08/22/2021] [Accepted: 08/27/2021] [Indexed: 06/13/2023]
Abstract
Chloroacetamides are commonly used in herbicide formulations, and their occurrence has been reported in soils and groundwater. However, how their chemical structures affect transformation kinetics and pathways in the presence of environmental reagents such as hydrogen sulfide species and black carbon has not been investigated. In this work, we assessed the impact of increasing Cl substituents on reaction kinetics and pathways of six chloroacetamides. The contribution of individual pathways (reductive dechlorination vs. nucleophilic substitution) to the overall decay of selected chloroacetamides was differentiated using various experimental setups; both the transformation rates and product distributions were characterized. Our results suggest that the number of Cl substituents affected reaction pathways and kinetics: trichloroacetamides predominantly underwent reductive dechlorination whereas mono- and dichloroacetamides transformed via nucleophilic substitution. Furthermore, we synthesized eight dichloroacetamide analogs (Cl2CHC(=O)NRR') with differing R groups and characterized their transformation kinetics. Dynamic NMR spectroscopy was employed to quantify the rotational energy barriers of dichloroacetamides. Our results suggest that adsorption of dichloroacetamides on black carbon constrained R groups from approaching the dichloromethyl carbon and subsequently favored nucleophilic attack. This study provides new insights to better predict the fate of chloroacetamides in subsurface environments by linking their structural characteristics to transformation kinetics and pathways.
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Affiliation(s)
- Xiaolei Xu
- Department of Civil and Environmental Engineering, Villanova University, Villanova, PA 19085, USA
| | | | - Neechi Okwor
- Department of Chemistry, Towson University, Towson, MD 21252, USA
| | - John D Sivey
- Department of Chemistry, Towson University, Towson, MD 21252, USA
| | - Keith P Reber
- Department of Chemistry, Towson University, Towson, MD 21252, USA
| | - Wenqing Xu
- Department of Civil and Environmental Engineering, Villanova University, Villanova, PA 19085, USA.
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5
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McFadden M, Patterson EV, Reber KP, Gilbert IW, Sivey JD, LeFevre GH, Cwiertny DM. Acid- and Base-Mediated Hydrolysis of Dichloroacetamide Herbicide Safeners. Environ Sci Technol 2022; 56:325-334. [PMID: 34920670 PMCID: PMC8733929 DOI: 10.1021/acs.est.1c05958] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Safeners are used extensively in commercial herbicide formulations. Although safeners are regulated as inert ingredients, some of their transformation products have enhanced biological activity. Here, to fill gaps in our understanding of safener environmental fate, we determined rate constants and transformation products associated with the acid- and base-mediated hydrolysis of dichloroacetamide safeners AD-67, benoxacor, dichlormid, and furilazole. Second-order rate constants for acid- (HCl) and base-mediated (NaOH) dichloroacetamide hydrolysis (2.8 × 10-3 to 0.46 and 0.3-500 M-1 h-1, respectively) were, in many cases (5 of 8), greater than those reported for their chloroacetamide herbicide co-formulants. In particular, the rate constant for base-mediated hydrolysis of benoxacor was 2 orders of magnitude greater than that of its active ingredient co-formulant, S-metolachlor. At circumneutral pH, only benoxacor underwent appreciable hydrolysis (5.3 × 10-4 h-1), and under high-pH conditions representative of lime-soda softening, benoxacor's half-life was 13 h─a timescale consistent with partial transformation during water treatment. Based on Orbitrap LC-MS/MS analysis of dichloroacetamide hydrolysis product mixtures, we propose structures for major products and three distinct mechanistic pathways that depend on the system pH and compound structure. These include base-mediated amide cleavage, acid-mediated amide cleavage, and acid-mediated oxazolidine ring opening. Collectively, this work will help to identify systems in which hydrolysis contributes to the transformation of dichloroacetamides, while also highlighting important differences in the reactivity of dichloroacetamides and their active chloroacetamide co-formulants.
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Affiliation(s)
- Monica
E. McFadden
- Department
of Civil and Environmental Engineering, University of Iowa, 4105 Seamans Center for the Engineering Arts and Sciences, Iowa City, Iowa 52242, United States
- IIHR-Hydroscience
and Engineering, University of Iowa, 100 C. Maxwell Stanley Hydraulics
Laboratory, Iowa City, Iowa 52242, United States
| | - Eric V. Patterson
- Department
of Chemistry, Stony Brook University, 100 Nicolls Road, 104 Chemistry, Stony Brook, New York 11790, United States
| | - Keith P. Reber
- Department
of Chemistry, Towson University, Towson, Maryland 21252, United States
| | - Ian W. Gilbert
- Department
of Chemistry, Towson University, Towson, Maryland 21252, United States
| | - John D. Sivey
- Department
of Chemistry, Towson University, Towson, Maryland 21252, United States
| | - Gregory H. LeFevre
- Department
of Civil and Environmental Engineering, University of Iowa, 4105 Seamans Center for the Engineering Arts and Sciences, Iowa City, Iowa 52242, United States
- IIHR-Hydroscience
and Engineering, University of Iowa, 100 C. Maxwell Stanley Hydraulics
Laboratory, Iowa City, Iowa 52242, United States
| | - David M. Cwiertny
- Department
of Civil and Environmental Engineering, University of Iowa, 4105 Seamans Center for the Engineering Arts and Sciences, Iowa City, Iowa 52242, United States
- IIHR-Hydroscience
and Engineering, University of Iowa, 100 C. Maxwell Stanley Hydraulics
Laboratory, Iowa City, Iowa 52242, United States
- Center
for Health Effects of Environmental Contamination (CHEEC), University of Iowa, 251 North Capitol Street, Chemistry Building—Room
W195, Iowa City, Iowa 52242, United States
- Department
of Chemistry, University of Iowa, E331 Chemistry Building, Iowa City, Iowa 52242, United States
- . Phone: (319) 335-1401
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6
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Zhang W, Yan J, Huang Y, Wang Z, Cheng B, Ma J, Wei Y, Meng Y, Lu H. Benoxacor caused developmental and cardiac toxicity in zebrafish larvae. Ecotoxicol Environ Saf 2021; 224:112696. [PMID: 34455182 DOI: 10.1016/j.ecoenv.2021.112696] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2021] [Revised: 08/20/2021] [Accepted: 08/22/2021] [Indexed: 06/13/2023]
Abstract
Benoxacor (BN) is a highly effective antidote of dichloroacetamide herbicides generally used to protect crops from herbicidal damage. As a commonly used agrochemical, this herbicide antidote is continuously discharged in watercourses thus causing toxicity to aquatic organisms, and ultimately leading to contamination of the food chain. To date, its potential toxicity to the cardiac development of aquatic organisms has not been evaluated. In the present study, we have selected the zebrafish as a model to study the impact of BN on embryonic developmental and cardiac toxicity. The zebrafish embryos were exposed in 0.5, 1.0 and 2.0 mg/L BN from 5.5 to 72 h post-fertilization (hpf). The results indicated that the exposure to BN led to increased mortality and diminished heart and hatching rates in the embryos. BN exposure also brought pericardial edema (PE) and linear stretching of heart. Besides, exposure to BN induced an excessive accumulation of reactive oxygen species (ROS) in the zebrafish embryos and abnormal activities of the antioxidant enzymes, including catalase (CAT) and malondialdehyde (MDA). Moreover, exposure to BN caused serious cardiac toxicity of the embryos, accompanied by abnormality of heart development- and apoptosis-related genes. Surprisingly, astaxanthin (ASTA), as a common antioxidant, was found to be able to partially rescue the cardiac toxicity caused by BN, which indicated that ROS are probably the major reason for the resulting cardiotoxicity in zebrafish embryos. Our results suggest the need for a comprehensive safety evaluation of the regular consumption of benoxacor, which provides scientific basis for the development of health standards and assessment of potential risk in aquatic organisms or even human.
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Affiliation(s)
- Weixin Zhang
- Ganzhou Key Laboratory for Drug Screening and Discovery, School of Geography and Environmental Engineering, Gannan Normal University, Ganzhou 341000, Jiangxi, China
| | - Jiajie Yan
- Ganzhou Key Laboratory for Drug Screening and Discovery, School of Geography and Environmental Engineering, Gannan Normal University, Ganzhou 341000, Jiangxi, China
| | - Yong Huang
- Ganzhou Key Laboratory for Drug Screening and Discovery, School of Geography and Environmental Engineering, Gannan Normal University, Ganzhou 341000, Jiangxi, China; College of Chemistry and Chemical Engineering, Gannan Normal University, Ganzhou 341000 Jiangxi, China
| | - Ziqin Wang
- Ganzhou Key Laboratory for Drug Screening and Discovery, School of Geography and Environmental Engineering, Gannan Normal University, Ganzhou 341000, Jiangxi, China
| | - Bo Cheng
- Ganzhou Key Laboratory for Drug Screening and Discovery, School of Geography and Environmental Engineering, Gannan Normal University, Ganzhou 341000, Jiangxi, China
| | - Jinze Ma
- Ganzhou Key Laboratory for Drug Screening and Discovery, School of Geography and Environmental Engineering, Gannan Normal University, Ganzhou 341000, Jiangxi, China
| | - You Wei
- Ganzhou Key Laboratory for Drug Screening and Discovery, School of Geography and Environmental Engineering, Gannan Normal University, Ganzhou 341000, Jiangxi, China; College of Chemistry and Chemical Engineering, Gannan Normal University, Ganzhou 341000 Jiangxi, China
| | - Yunlong Meng
- Ganzhou Key Laboratory for Drug Screening and Discovery, School of Geography and Environmental Engineering, Gannan Normal University, Ganzhou 341000, Jiangxi, China; College of Chemistry and Chemical Engineering, Gannan Normal University, Ganzhou 341000 Jiangxi, China
| | - Huiqiang Lu
- Ganzhou Key Laboratory for Drug Screening and Discovery, School of Geography and Environmental Engineering, Gannan Normal University, Ganzhou 341000, Jiangxi, China; College of Chemistry and Chemical Engineering, Gannan Normal University, Ganzhou 341000 Jiangxi, China; Jiangxi Engineering Laboratory of Zebrafish Modeling and Drug Screening for Human Diseases, Jiangxi Key Laboratory of Developmental Biology of Organs, Affiliated Hospital of Jinggangshan University, Ji'an 343009, China.
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7
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Liu S, Deng X, Zhou X, Bai L. Assessing the toxicity of three "inert" herbicide safeners toward Danio rerio: Effects on embryos development. Ecotoxicol Environ Saf 2021; 207:111576. [PMID: 33254422 DOI: 10.1016/j.ecoenv.2020.111576] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Revised: 10/24/2020] [Accepted: 10/27/2020] [Indexed: 06/12/2023]
Abstract
Recent studies indicated that 'inert ingredients' exert negative effects on the environment. Herbicide safeners are classed as 'inert ingredients', which increase the selectivity and detoxification of herbicides. However, little attention has been focused on the environmental behavior of herbicide safeners. AD-67 (AD), fenclorim (FM), and flurazole (FZ) are three commercially available herbicide safeners. In this study, zebrafish embryos were used as a model to investigate the potential developmental toxicity of these three safeners. The results showed that AD, FM, and FZ 96 h-LC50 values were 2.52, 1.26, and 2.01 mg/L, respectively. Significant decreased body lengths were observed in embryos after 96 h of exposure to 0.2 mg/L FM and FZ. Hatching rates significantly increased at 24 h and decreased at 96 h in all treatment groups (0.02 mg/L AD, 0.2 mg/L AD, 0.02 mg/L AD, 0.2 mg/L FZ, as well as 0.01 and 0.1 mg/L FM). No significant (p > 0.05) changes in heartbeat numbers (60 s), but clearly increased malformation rates were observed in response to safeners exposure. Furthermore, embryos showed signs of oxidative stress, such as decreased activities of superoxide dismutase, altered activities of glutathione reductase and catalase and cell apoptosis. The gene transcription related to body malformation (egf, krt 17, and tbx 16) and cell apoptosis (bcl 2 and bax) changed in treated groups. These genes have been connected to potential toxicological mechanisms. These results indicate that the herbicide safeners AD, FM, and FZ induced developmental toxicities in zebrafish embryos. This study is the first report of the toxicity of safeners in the development of zebrafish embryos. The results may be useful for assessing the risk of herbicides safeners in the aquatic ecosystem.
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Affiliation(s)
- Sihong Liu
- Long Ping Branch, Graduate School of Hunan University, Changsha 410125, China; Key Laboratory for Biology and Control of Weeds, Hunan Agricultural Biotechnology Research Institute, Hunan Academy of Agricultural Sciences, Changsha 410125, China
| | - Xile Deng
- Key Laboratory for Biology and Control of Weeds, Hunan Agricultural Biotechnology Research Institute, Hunan Academy of Agricultural Sciences, Changsha 410125, China.
| | - Xiaomao Zhou
- Long Ping Branch, Graduate School of Hunan University, Changsha 410125, China; Key Laboratory for Biology and Control of Weeds, Hunan Agricultural Biotechnology Research Institute, Hunan Academy of Agricultural Sciences, Changsha 410125, China
| | - Lianyang Bai
- Long Ping Branch, Graduate School of Hunan University, Changsha 410125, China; Key Laboratory for Biology and Control of Weeds, Hunan Agricultural Biotechnology Research Institute, Hunan Academy of Agricultural Sciences, Changsha 410125, China.
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Oloye FF, Femi-Oloye OP, Challis JK, Jones PD, Giesy JP. Dissipation, Fate, and Toxicity of Crop Protection Chemical Safeners in Aquatic Environments. Rev Environ Contam Toxicol 2021; 258:27-53. [PMID: 34529146 DOI: 10.1007/398_2021_70] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Safeners are a group of chemicals applied with herbicides to protect crop plants from potential adverse effects of agricultural products used to kill weeds in monocotyledonous crops. Various routes of dissipation of safeners from their point of applications were evaluated. Despite the large numbers of safeners (over 18) commercially available and the relatively large quantities (~2 × 106 kg/year) used, there is little information on their mobility and fate in the environment and occurrence in various environmental matrices. The only class of safeners for which a significant amount of information is available is dichloroacetamide safeners, which have been observed in some rivers in the USA at concentrations ranging from 42 to 190 ng/L. Given this gap in the literature, there is a clear need to determine the occurrence, fate, and bioavailability of other classes of safeners. Furthermore, since safeners are typically used in commercial formulations, it is useful to study them in relation to their corresponding herbicides. Common routes of dissipation for herbicides and applied safeners are surface run off (erosion), hydrolysis, photolysis, sorption, leaching, volatilization, and microbial degradation. Toxic potencies of safeners vary among organisms and safener compounds, ranging from as low as the LC50 for fish (Oncorhynchus mykiss) for isoxadifen-ethyl, which was 0.34 mg/L, to as high as the LC50 for Daphnia magna from dichlormid, which was 161 mg/L. Solubilities and octanol-water partition coefficients seem to be the principal driving force in understanding safener mobilities. This paper provides an up-to-date literature review regarding the occurrence, behaviour, and toxic potency of herbicide safeners and identifies important knowledge gaps in our understanding of these compounds and the potential risks posed to potentially impacted ecosystems.
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Affiliation(s)
- Femi F Oloye
- Department of Chemical Sciences, Adekunle Ajasin University, Akungba-Akoko, Nigeria.
| | - Oluwabunmi P Femi-Oloye
- Toxicology Centre, University of Saskatchewan, Saskatoon, SK, Canada
- Department of Animal and Environmental Biology, Adekunle Ajasin University, Akungba-Akoko, Nigeria
| | | | - Paul D Jones
- Toxicology Centre, University of Saskatchewan, Saskatoon, SK, Canada
- School of Environment and Sustainability, University of Saskatchewan, Saskatoon, SK, Canada
| | - John P Giesy
- Toxicology Centre, University of Saskatchewan, Saskatoon, SK, Canada
- Department of Biomedical Veterinary Sciences, University of Saskatchewan, Saskatoon, SK, Canada
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9
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Xu X, Sivey JD, Xu W. Black carbon-enhanced transformation of dichloroacetamide safeners: Role of reduced sulfur species. Sci Total Environ 2020; 738:139908. [PMID: 32531604 DOI: 10.1016/j.scitotenv.2020.139908] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 05/27/2020] [Accepted: 05/31/2020] [Indexed: 05/24/2023]
Abstract
Dichloroacetamide safeners are commonly included in herbicide formulations to protect crops from unintended herbicide toxicity, but knowledge of their environmental fate is scarce. Hydrogen sulfide, a naturally-occurring nucleophile and reductant, often coexists with black carbon (e.g., biochar, soot) in subsurface environments and could influence the fate of these safeners. In this study, we demonstrated that graphite powder, a model black carbon, significantly accelerated the transformation of three dichloroacetamide safeners (AD-67, benoxacor, and dichlormid) and two chloroacetamide herbicides (metolachlor and acetochlor) by hydrogen sulfide. Chloride was formed together with an array of sulfur-substituted products, suggesting a nucleophilic substitution pathway. Our results suggest that the electron-accepting capacity of black carbon can oxidize hydrogen sulfide species to elemental sulfur, which can further react with bisulfide to form polysulfide, likely accounting for the observed accelerated transformation of (di)chloroacetamides in systems containing black carbon and hydrogen sulfide. Moreover, our product analyses indicate that dimerization and/or trimerization of (di)chloroacetamides is possible in the presence of hydrogen sulfide and graphite, which is anticipated to decrease the mobility of these products in aquatic environments relative to the parent compounds. Herein, we also discuss how the structure and concentration of (di)chloroacetamides can influence their reactivity in the presence of black carbon and reduced sulfur species.
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Affiliation(s)
- Xiaolei Xu
- Department of Civil and Environmental Engineering, Villanova University, Villanova, PA 19085, USA
| | - John D Sivey
- Department of Chemistry, Towson University, Towson, MD 21252, USA
| | - Wenqing Xu
- Department of Civil and Environmental Engineering, Villanova University, Villanova, PA 19085, USA.
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Ricko AN, Psoras AW, Sivey JD. Reductive transformations of dichloroacetamide safeners: effects of agrochemical co-formulants and iron oxide + manganese oxide binary-mineral systems. Environ Sci Process Impacts 2020; 22:2104-2116. [PMID: 32959852 DOI: 10.1039/d0em00331j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The toxic effects of herbicides are often incompletely selective and can harm crops. Safeners are "inert" ingredients commonly added to herbicide formulations to protect crops from herbicide-induced injury. Dichloroacetamide safeners have been previously shown to undergo reductive dechlorination in anaerobic abiotic systems containing an iron (hydr)oxide mineral (goethite or hematite) amended with Fe(ii). Manganese oxides (e.g., birnessite) are important redox-active species that frequently co-occur with iron (hydr)oxides, yet studies examining the effects of more than one mineral on transformations of environmental contaminants are rare. Herein, we investigate the reactivity of dichloroacetamide safeners benoxacor, furilazole, and dichlormid in binary-mineral, anaerobic systems containing Fe(ii)-amended hematite and birnessite. As the molar ratio of Fe(ii)-to-Mn(iv) oxide increased, the transformation rate of benoxacor and furilazole increased. The safener dichlormid did not transform appreciably over the sampling period (6 hours). The concentration of pH buffer ([MOPS] = 10-50 mM), ionic strength ([NaCl] = 10-200 mM), and order of solute addition (e.g., safener followed by Fe(ii) or vice versa) do not appreciably affect transformation rates of the examined dichloroacetamide safeners in Fe(ii) + hematite slurries. The presence of agrochemical co-formulants, including the herbicide S-metolachlor and three surfactants, in solutions containing Cr(H2O)62+ (as a model homogeneous reductant) also did not substantially influence rates of safener transformation. This study is among the first to examine laboratory systems of intermediate complexity (e.g., systems containing mixtures of agrochemical co-formulants or mineral phases) when assessing the environmental fate of emerging contaminants such as dichloroacetamide safeners.
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Affiliation(s)
- Allison N Ricko
- Environmental Science & Studies Program, Towson University, Towson, Maryland, USA.
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Simonsen D, Cwiertny DM, Lehmler HJ. Benoxacor is enantioselectively metabolized by rat liver subcellular fractions. Chem Biol Interact 2020; 330:109247. [PMID: 32866466 DOI: 10.1016/j.cbi.2020.109247] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 08/19/2020] [Accepted: 08/27/2020] [Indexed: 10/23/2022]
Abstract
This study investigated the enantioselective metabolism of benoxacor, an ingredient of herbicide formulations, in microsomes or cytosol prepared from female or male rat livers. Benoxacor was incubated for ≤30 min with microsomes or cytosol, and its enantioselective depletion was measured using gas chromatographic methods. Benoxacor was depleted in incubations with active microsomes in the presence and absence of NADPH, suggesting its metabolism by hepatic cytochrome P450 enzymes (CYPs) and microsomal carboxylesterases (CESs). Benoxacor was depleted in cytosolic incubations in the presence of glutathione, consistent with its metabolism by glutathione S-transferases (GSTs). The depletion of benoxacor was faster in incubations with cytosol from male than female rats, whereas no statistically significant sex differences were observed in microsomal incubations. The consumption of benoxacor was inhibited by the CYP inhibitor 1-aminobenzotriazole, the CES inhibitor benzil, and the GST inhibitor ethacrynic acid. Estimates of the intrinsic clearance of benoxacor suggest that CYPs are the primary metabolic enzyme responsible for benoxacor metabolism in rats. Microsomal incubations showed an enrichment of the first eluting benoxacor enantiomer (E1-benoxacor). A greater enrichment occurred in incubations with microsomes from female (EF = 0.67 ± 0.01) than male rats (EF = 0.60 ± 0.01). Cytosolic incubations from female rats resulted in enrichment of E1-benoxacor (EF = 0.54 ± 0.01), while cytosolic incubations from male rats displayed enrichment of the second eluting enantiomer (E2-benoxacor; EF = 0.43 ± 0.01). Sex-dependent differences in the metabolism of benoxacor in rats could significantly impact ecological risks and mammalian toxicity. Moreover, changes in the enantiomeric enrichment of benoxacor may be a powerful tool for environmental fate and transport studies.
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Affiliation(s)
- Derek Simonsen
- Department of Occupational and Environmental Health, The University of Iowa, Iowa City, IA, 52242, United States; Interdisciplinary Graduate Program in Human Toxicology, The University of Iowa, Iowa City, IA, 52242, United States; IIHR Hydroscience and Engineering, The University of Iowa, Iowa City, IA, 52242, United States
| | - David M Cwiertny
- IIHR Hydroscience and Engineering, The University of Iowa, Iowa City, IA, 52242, United States; Department of Civil and Environmental Engineering, The University of Iowa, Iowa City, IA, 52242, United States; Center for Health Effects of Environmental Contamination, The University of Iowa, Iowa City, 52242, Iowa, USA
| | - Hans-Joachim Lehmler
- Department of Occupational and Environmental Health, The University of Iowa, Iowa City, IA, 52242, United States; Interdisciplinary Graduate Program in Human Toxicology, The University of Iowa, Iowa City, IA, 52242, United States; IIHR Hydroscience and Engineering, The University of Iowa, Iowa City, IA, 52242, United States.
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Acharya SP, Johnson J, Weidhaas J. Adsorption kinetics of the herbicide safeners, benoxacor and furilazole, to activated carbon and agricultural soils. J Environ Sci (China) 2020; 89:23-34. [PMID: 31892395 DOI: 10.1016/j.jes.2019.09.022] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 09/23/2019] [Accepted: 09/24/2019] [Indexed: 05/24/2023]
Abstract
Chloroacetamide herbicides, namely acetochlor and metolachlor, are common herbicides used on corn and soybean fields. Dichloroacetamide safeners, namely benoxacor and furilazole, are commonly used in formulations containing chloroacetamide herbicides. Extensive reports on adsorption of chloroacetamide herbicides are available, yet little information exists regarding adsorption potential of co-applied safeners. Herein, the adsorption and desorption characteristics of selected herbicide safeners to granular activated carbon (GAC) and in agricultural soils are reported. Further, soil column studies were performed to understand the leaching behaviour of the herbicide Dual II Magnum. Equilibrium sorption experiments of safeners to three agricultural soils and one GAC showed that adsorption was best fitted by the Freundlich isotherm. The Freundlich adsorption constant, Kf, for benoxacor and furilazole sorption onto three agricultural soils ranged from 0.1 to 0.27 and 0.1 to 0.13 (mg/g) × (mg/L)ˆ(1/n), respectively. The Kf for benoxacor and furilazole to GAC was 6.4 and 3.4 (mg/g) × (mg/L)ˆ(1/n), respectively, suggesting more favorable sorption of benoxacor to GAC than furilazole to GAC. The sorption to soils was reversible as almost 40%-90% of both safeners was desorbed from three soils. These results were validated in four replicated soil column studies, where S-metolachlor was shown to leach similarly to the safener benoxacor, originating from the herbicide formulation. The leaching of S-metolachlor and benoxacor was influenced by soil texture. Cumulatively, these results show that safeners will move through the environment to surface waters similarly to the active ingredients in herbicides, but may be removed during drinking water treatment via GAC.
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Affiliation(s)
| | - Jacob Johnson
- Center for Science and Mathematics Education, University of Utah, 155 South 1452 East, Salt Lake City, UT 84112, USA
| | - Jennifer Weidhaas
- Civil and Environmental Engineering, University of Utah, Salt Lake City, UT, USA.
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Kral AE, Pflug NC, McFadden ME, LeFevre GH, Sivey JD, Cwiertny DM. Photochemical Transformations of Dichloroacetamide Safeners. Environ Sci Technol 2019; 53:6738-6746. [PMID: 31117539 DOI: 10.1021/acs.est.9b00861] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Dichloroacetamide safeners are commonly added to commercial chloroacetamide herbicide formulations and widely used worldwide, but their environmental fate has garnered little scrutiny as a result of their classification as "inert" ingredients. Here, we investigated the photolysis of dichloroacetamide safeners to better understand their persistence and the nature of their transformation products in surface waters. High-resolution mass spectrometry (HRMS) and nuclear magnetic resonance (NMR) spectroscopy were used to characterize photoproducts. Of the four commonly used dichloroacetamide safeners, only benoxacor undergoes direct photolysis under simulated natural sunlight ( t1/2 ∼ 10 min). Via a photoinitiated ring closure, benoxacor initially yields a monochlorinated intermediate that degrades over longer irradiation time scales to produce two fully dechlorinated diastereomers and a tautomer, which further photodegrade over several days to a structurally related aldehyde confirmed via NMR. Dichlormid, AD-67, and furilazole were more slowly degraded by indirect photolysis in the presence of the photosensitizers nitrate, nitrite, and humic acid. Reactive entities involved in these reactions are likely hydroxyl radical and singlet oxygen based on the use of selective quenchers. These safeners also directly photolyzed under higher energy ultraviolet (UV) light, suggesting their potential transformation in engineered systems using UV for disinfection. The finding that dichloroacetamide safeners can undergo photolysis in environmental systems over relevant time scales demonstrates the importance of evaluating the fate of this class of "inert" agrochemicals.
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Affiliation(s)
- Andrew E Kral
- Department of Civil & Environmental Engineering , University of Iowa , 4105 Seamans Center for the Engineering Arts and Sciences, Iowa City , Iowa 52242 , United States
| | - Nicholas C Pflug
- Department of Chemistry , University of Iowa , E331 Chemistry Building, Iowa City , Iowa 52242 , United States
| | - Monica E McFadden
- Department of Civil & Environmental Engineering , University of Iowa , 4105 Seamans Center for the Engineering Arts and Sciences, Iowa City , Iowa 52242 , United States
| | - Gregory H LeFevre
- Department of Civil & Environmental Engineering , University of Iowa , 4105 Seamans Center for the Engineering Arts and Sciences, Iowa City , Iowa 52242 , United States
- IIHR-Hydroscience & Engineering University of Iowa , 100 C. Maxwell Stanley Hydraulics Laboratory, Iowa City , Iowa 52242 , United States
| | - John D Sivey
- Department of Chemistry , Towson University , 543 Smith Hall, Towson , Maryland 21252 , United States
| | - David M Cwiertny
- Department of Civil & Environmental Engineering , University of Iowa , 4105 Seamans Center for the Engineering Arts and Sciences, Iowa City , Iowa 52242 , United States
- Department of Chemical & Biochemical Engineering , University of Iowa , 4133 Seamans Center for the Engineering Arts and Sciences, Iowa City Iowa 52242 , United States
- IIHR-Hydroscience & Engineering University of Iowa , 100 C. Maxwell Stanley Hydraulics Laboratory, Iowa City , Iowa 52242 , United States
- Center for Health Effects of Environmental Contamination , University of Iowa , 251 North Capitol Street , Chemistry Building - Room W195, Iowa City , Iowa 52242 , United States
- Public Policy Center , University of Iowa , 310 South Grand Avenue , 209 South Quadrangle, Iowa City , Iowa 52242 , United States
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