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A comparative assessment of the transformation products of S-metolachlor and its commercial product Mercantor Gold (R) and their fate in the aquatic environment by employing a combination of experimental and in silico methods
... Effets des mélanges de pesticides sur la transformation des molécules individuelles 1.2.1. Photo-transformation L'effet des adjuvants sur la photo-dégradation de pesticides a été mis en évidence dans l'eau, avec notamment une photo-dégradation plus importante du S-métolachlore formulé (Mercantor Gold ® ) par rapport à la substance active pure (Gutowski et al., 2015). De même, à la surface de cire cuticulaire synthétique mimant la surface de feuille, la photo-dégradation de la mésotrione et du nicosulfuron est considérablement augmentée en présence d'adjuvants par rapport à chacune des molécules pures (Ter Halle et al., 2010). ...
... Les transformations abiotiques du S-métolachlore dans le sol et l'eau sont principalement régies par le processus de photolyse, l'hydrolyse étant en effet considérée comme négligeable (EFSA, 2004;Zemolin et al., 2014;Gutowski et al., 2015). ...
... La présence de nitrates accélère également la photo-dégradation du métolachlore, en raison de la production de radicaux hydroxyles générés par la photolyse des nitrates (Dimou et al., 2005). Le S-métolachlore formulé (Mercantor Gold ® , 960 g L -1 de S-métolachlore) est aussi plus rapidement photodégradé que le S-métolachlore pur, certainement en raison de la présence d'acide dodécylbenzènesulfonique dans la formulation, un adjuvant qui solubilise et disperse la substance active, augmentant son exposition à la lumière (Gutowski et al., 2015). Au contraire, en présence de matière organique dissoute, un écran se forme, menant à une diminution de la photo-dégradation du métolachlore (Dimou et al., 2005). ...
Les pesticides de nouvelle génération sont le plus souvent épandus à de faibles doses et en mélange. Peu d’études se sont intéressées jusqu’à présent à l’effet de ces mélanges sur la biodégradation et la toxicité de chaque pesticide et/ou métabolite. Le but de ces travaux de thèse était d’étudier les voies de biotransformation de chacun des trois herbicides d’un mélange constitué de mésotrione (β-tricétone), nicosulfuron (sulfonylurée) et S-métolachlore (chloroacétanilide) utilisé sur les cultures de maïs, ainsi que la toxicité (test Microtox ® ) des herbicides et de leurs métabolites, seuls et en mélanges. L’identification des métabolites de la mésotrione chez la souche Bacillus megaterium Mes11 et une étude de protéomique différentielle ont suggéré l’implication de nitroréductases dans la première étape de la biotransformation de cet herbicide, rôle confirmé ensuite par la caractérisation structurelle et fonctionnelle de deux enzymes capables de transformer la mésotrione : les nitroréductases NfrA1 et NfrA2, appartenant à la sous-famille NfsA-FRP des Nitro-FMN réductases. La voie de biotransformation du nicosulfuron a, quant à elle, été étudiée chez la souche Pseudomonas fluorescens SG-1 isolée à partir de sol agricole, capable de transformer cet herbicide par co-métabolisme. Cette biotransformation conduit à la formation de deux métabolites majoritaires issus du clivage de la liaison sulfonylurée du nicosulfuron, l’un deux (l’ADMP, 2-amino-4,6-diméthoxypyrimidine) présentant une toxicité 20 fois supérieure à celle de la molécule mère. Nous avons également étudié qualitativement et quantitativement la biotransformation de la mésotrione et du nicosulfuron par la souche Mes11 séparément ou en mélange, et en présence ou non de S-métolachlore Les résultats ont montré un effet négatif de la mésotrione sur la biotransformation du nicosulfuron et un effet positif du S-métolachlore sur la biotransformation de la mésotrione. Tous les mélanges d’herbicides testés ont montré des effets synergiques pour la toxicité vis-à-vis de A. fischeri, tandis que les mélanges de métabolites (avec ou sans S-métolachlore) étaient majoritairement synergiques ou antagonistes. La dernière partie des travaux de thèse est focalisée sur le développement d’une technique préventive de traitement de la pollution par les pesticides d’origine agricole (bioprophylaxie). Nous avons fait la preuve de concept de cette technique par une étude en microcosmes de sol. L’épandage simultané de l’herbicide 2,4-D (acide 2,4-dichlorophénoxyacétique) et de la souche Cupriavidus necator JMP134 capable de le minéraliser a en effet permis de réduire le temps de demi-vie de ce composé d’un facteur 3, tout en conservant son activité herbicide.
... Few studies focused on pesticides and their commercial formulations' biodegradation in the water-sediment systems (García-Ortega et al., 2006;Krieger et al., 1989). Only Gutowski et al. (2015) studied the environmental fate of SM and MG in a combined consecutive photolysis -biodegradation test. However, no sediment phase was included in this study. ...
... The final concentration of SM and MG was adjusted by measuring NPOC (non-purgeable organic carbon) of the tested substance (i.e. before photolysis) and photolysis treated samples, to provide required carbon content, and to reach adequate theoretical oxygen demand (ThOD), (described further in Section 2.3) Details on the experimental methods and the structural elucidation of the photo-TPs can be found in Gutowski et al. (2015). ...
... The mass spectrometer was connected to an Agilent LC 1100 series (Agilent Technologies, Böblingen, Germany, HPLC 1100 series). The complete analytical method, operating parameters of the source, and ion-trap are described in detail by Gutowski et al. (2015) and were summarized in Text S2 (SI). ...
... Other studies have also reported considerable abiotic losses of pesticides and herbicides via sorption on wood particles [22,27]. The authors of [48] observed a low biodegradability for S-metolachlor of less than 5% after 28 days. These Figure 3 shows the loss of metolachlor during the experiments. ...
... Other studies have also reported considerable abiotic losses of pesticides and herbicides via sorption on wood particles [22,27]. The authors of [48] observed a low biodegradability for S-metolachlor of less than 5% after 28 days. These results agree with our observations. ...
We developed, tested, and optimized two laboratory denitrification assays for both managers and scientists to assess the effects of xenobiotics on the denitrification process over 7 days (short batch assay, SBA) and 28 days (long semi-continuous assay, LSA). The assays facilitate (1) measuring the efficiency of nitrate removal under the influence of xenobiotics, (2) determining the removal of the tested xenobiotics via adsorption or biotic decomposition, and (3) testing the influencing parameters for optimizing the denitrification process. The adsorption of the xenobiotics was assessed by inhibiting all biological processes through the addition of HgCl 2. Our tests demonstrate that the ratio of the initial nitrate concentration to the amount of bioavailable organic matter provided is essential to avoid organic carbon or nitrate limitation. While a pH < 7 resulted in decreased denitrification, a pH > 8 led to nitrite accumulation, indicating incomplete denitrification. Over durations of more than a week, weekly replenishments of the nitrate and HgCl 2 and weekly purging with argon gas to reduce the oxygen concentrations are needed. The assays provide information about the accumulation of xenobiotics in the bioreactors that is necessary for the environmentally friendly treatment of the bioreactor fillings and provide insight into the potential of the bioreactors to remove pesticides from polluted water resources.
... Pesticides and their TPs are frequently detected in soil, groundwater and surface water, and they represent an important source of chemical pollution (Fenner et al., 2013;Huntscha et al., 2008). Several studies investigated pesticide TPs and their toxicities and showed that TPs might pose similar or even higher toxic effects on different species (Bustos et al., 2019;Escher and Fenner, 2011;Gutowski et al., 2015). Therefore, these substances may pose a greater risk to the environment than their parent compounds. ...
... If there is no information of pesticide degradation, it would be a challenge to explore the fate and J o u r n a l P r e -p r o o f ecological effects of pesticides. Under the circumstances, Exposure-or effect-driven approaches (Escher and Fenner, 2011) and hybrid approaches of a combination of in vitro and in silico methods (Gutowski et al., 2015;Hensen et al., 2020b) were developed to evaluate the toxicity of pesticide TPs, and QSAR is also increasingly used for the assessment of environmental properties of pesticide TPs (Jose Villaverde et al., 2017;Villaverde et al., 2018). To predict the fate of pesticides in the natural environment and to access the environmental risks they might pose, it is necessary for us to improve the understanding of the chemical reactions and TP structures of pesticides under various environmental conditions (Sevilla-Moran et al., 2010). ...
Difenoconazole is a widely used triazole fungicide that has been frequently detected in the environment, but comprehensive study about its environmental fate and toxicity of potential transformation products (TPs) is still lacking. Here, laboratory experiments were conducted to investigate the degradation kinetics, pathways, and toxicity of transformation products of difenoconazole. 12, 4 and 4 TPs generated by photolysis, hydrolysis and soil degradation were identified via UHPLC-QTOF/MS and the UNIFI software. Four intermediates TP295, TP295A, TP354A and TP387A reported for the first time were confirmed by purchase or synthesis of their standards, and they were further quantified using UHPLC-MS/MS in all tested samples. The main transformation reactions observed for difenoconazole were oxidation, dechlorination and hydroxylation in the environment. ECOSAR prediction and laboratory tests showed that the acute toxicities of four novel TPs on Brachydanio rerio, Daphnia magna and Selenastrum capricornutum are substantially lower than that of difenoconazole, while all the TPs except for TP277C were predicted chronically very toxic to fish, which may pose a potential threat to aquatic ecosystems. The results are important for elucidating the environmental fate of difenoconazole and assessing the environmental risks, and further provide guidance for scientific and reasonable use.
... Studies that analyzed these properties showed that TPs are often more mobile and persistent in the aquatic environment than their parent compounds. Some of these studies also showed that TPs might pose similar or even higher toxic effects on different species (Belfroid et al., 1998;Bustos et al., 2019;Escher and Fenner, 2011;Gutowski et al., 2015cGutowski et al., , 2015aSinclair and Boxall, 2009). Factors that could indicate a consistent or even increased toxicity of TPs compared to their parent compounds were described by Sinclair and Boxall (2009). ...
... In combination with the computer based in silico tool MultiCASE literature data was used to assess and evaluate the environmental toxicity and genotoxicity of TPs (Tier I). MultiCASE was used due to its inclusion of the required endpoints and its applicability for TPs of organic compounds as shown by previous studies (Gutowski et al., 2015c;Mahmoud et al., 2014;Menz et al., 2017;Rastogi et al., 2014). In case of toxic indications, photolysis experiments of the parent compounds were performed to produce a reaction mixture of TPs for further toxicity testing in a luminescent bacteria test (LBT) and a genotoxicity test (umu-test) (Tier II). ...
In order to conduct a fast and comprehensive toxicity screening of pesticide transformation products (TPs), this study used a tiered approach by a combination of in silico and experimental methods to determine the probability to be of relevance for risk assessment. The six pesticides Boscalid, Penconazole, Diuron, Terbutryn, Octhilinone (OIT), and Mecoprop were used as model compounds. Identification of corresponding environmental known and unknown TPs were done by literature analysis and photolysis experiments in combination. Aquatic solutions of the pesticides were photolysed to generate TPs which can be expected in the aquatic environment. The resulting mixtures were screened for TPs by high resolution LC-MS/MS. The herein developed approach was conducted at three different tiers: Literature review and in silico methods were used to predict exemplary the environmental bacterial toxicity and the genotoxicity of every single TP at tier I. In case of indications to be toxic, experiments at tier II were applied. Hereby, the photolytic mixtures containing parent compound and TPs were used for the consecutive toxicity test. Microtox assay for the parent compounds and the photolytic mixture was conducted to determine the acute and chronic toxicity and the growth inhibition of V. fischeri. Umu-tests were conducted to determine primary DNA damage. At tier III, single substance standards were used to conduct toxicity tests in case of toxic indication by previous tiers and availability of analytical standard. Identification of TPs revealed 45 known environmental TPs that originated from the six pesticides. The number of substances that need to be assessed was therefore more than sevenfold. By the tiered approach, it was possible to assess toxicological effects on environmental bacteria of 94% of the selected TPs. For 20% we found strong evidence to be toxic to environmental bacteria, as they were assessed at least at two tiers. For further 44% of the TPs we found slight evidence, as they could be assessed at one tier. Contrary, this approach turned out to be unsuitable to assess genotoxic effects of TPs neither by in silico tools nor by experiments. The number of substances that could probably pose a risk onto environment was quadrupled in comparison to the consideration of solely the parent compounds. Thus, this study demonstrates that the conducted screening approach allows for easy and fast identification of environmental relevant TPs. However, the study presented was a very first screening. Its applicability domain needs to be assessed further. For this purpose as a very next step the approach suggested here should be verified by applying additional endpoints and including additional parent compounds.
... Furthermore, irradiance reference spectra were recently updated and validated against high resolution spectroradiometers, which will allow for more accurate half-life calculations because (1) the irradiance values are more accurate than those previously used and (2) they are available at 1 nm increments, which is important when the absorption spectrum of the compound has only a small overlap with the solar spectrum. 10 Although the investigation of photodegradation in the aquatic environment is most common for plant protection products [11][12][13][14][15] and pharmaceuticals, [16][17][18][19][20][21][22] it has also been conducted for personal care products, 23,24 industrial chemicals 25 and fragrances. [26][27][28] In a study by Buerge et al. (2003), the authors found that photodegradation led to the elimination of several non-biodegradable fragrance ingredients in lake systems. ...
... Previous studies have investigated the fate and potential risks of the transformation products in various ways such as biodegradation assays of photolysis mixture or individual transformation products, applying different QSAR models to transformation products or fugacity modeling of transformation products. 12,21,[31][32][33] The objective of this work was to evaluate the photodegradation of the fragrance ingredient (E)-4-(2,2,3,6tetramethylcyclohexyl)but-3-en-2-one to further assess its persistence in aquatic environments and the formation and degradation of its transformation products. Using this fragrance ingredient as an example, a streamlined workow was also created to more efficiently evaluate the potential direct photodegradation of other chemicals in the future for regulatory assessment. ...
Photodegradation can be an important abiotic degradation process to consider for the fate and persistence assessment of chemical substances in the environment. In this work, using a fragrance ingredient (FI, (E)-4-(2,2,3,6-tetramethylcyclohexyl)but-3-en-2-one) as an example, we developed a streamlined workflow to investigate direct photodegradation of chemicals in the aquatic environment, including laboratory investigation of kinetics and transformation products and estimation of its aquatic environmental half-lives. Direct photodegradation was determined to be the dominant photodegradation process for FI with a quantum yield of 0.25, which was supported by photodegradation experiments conducted in natural sunlight. Accounting for light attenuation by dissolved organic matter in natural waters of different depths resulted in aquatic half-lives of <31 days even at polar latitudes. Photoisomerization was shown to be a major photodegradation pathway along with the formation and subsequent degradation of constitutional isomers and photooxidation products. These results contributed to FI being assessed as non-persistent in the environment.
... Weiterhin noch existierende unbeabsichtigte Stoffeinträge erfolgen unter anderem aus Reifenabrieb, Fassadenverwitterung, Verbrennungsprozessen, aber beispielsweise auch Flammschutzmittel aus elektronischen Geräten und Nachtwäsche oder organische Siliciumverbindungen und viele weitere chemische Stoffe aus Textilien sind zu nennen . Neben den eigentlichen Substanzen, denen häufig ausschließlich unser Interesse gilt, sind jedoch in Produkten oft noch weitere Stoffe enthalten [17,18], die zusätzlich das Verhalten und die Wirkung der Hauptinhaltstoffe (oft der Wirkstoffe) beeinflussen können, ja manchmal sogar sollen . ...
... wirkungen (nicht zu schwache, nicht zu starke, richtige räumliche Anordnung) eingehen kann . Darüber hinaus können Transformationsprodukte aber auch unpolarer sein als ihre Muttersubstanzen (zum Beispiel [18,25]) . ...
Mikroverunreinigungen sind schon seit langem ein Thema, das
große Aufmerksamkeit erfährt. Eine Vielzahl von technischen
Lösungen zur Behandlung von Abwasser („Ansetzen am Ende
des Rohres“) wurde vorgeschlagen, untersucht und vereinzelt
umgesetzt. Insbesondere für die erweiterte Abwasserreinigung
konnte zwischenzeitlich gezeigt werden, dass sie das Problem alleine
bei weitem nicht löst, sondern zum Teil sogar verschlimmert,
und das zum Preis eines erhöhten baulichen, technischen,
energetischen, chemischen und finanziellen Aufwands. Daher
muss der Verminderung oder Vermeidung des Eintrags direkt an
der Quelle (am Anfang des Rohres) sehr viel mehr Aufmerksamkeit
geschenkt werden als bisher.
... chemical-use/what-chemicals-are-used). Additionally, medications and many products such as pesticides contain also adjuvants and excipients (Wirz et al., 2015;Gutowski et al., 2015), which modulate their environmental fate and activity. This is most often not in focus. ...
... Khaleel et al., 2017;Herrmann et al., 2015;Rastogi et al., 2014Rastogi et al., , 2015aRastogi et al., , 2015b. Other studies even demonstrated that biodegradation of photo TPs led to the generation of new, recalcitrant bio-TPs (Herrmann et al., 2016b;Gutowski et al., 2015). In other words, reducing the concentration of a given parent compound by a treatment does not necessarily imply lower risk. ...
Pharmaceuticals and many other chemicals are an important basis for nearly all sectors including for example, food and agriculture, medicine, plastics, electronics, transport, communication, and many other products used nowadays. This comes along with a tremendous chemicalization of the globe, including ubiquitous presence of products of chemical and pharmaceutical industries in the aquatic environment. Use of these products will increase with population growth and living standard as will the need for clean water. In addition, climate change will exacerbate availability of water in sufficient quantity and quality. Since its implementation, conventional wastewater treatment has increasingly contributed to environmental protection and health of humans. However, with the increasing pollution of water by chemicals, conventional treatment turned out to be insufficient. It was also found that advanced effluent treatment methods such as extended filtration, the sorption to activated charcoal or advanced oxidation methods have their own limitations. These are, for example, increased demand for energy and hazardous chemicals, incomplete or even no removal of pollutants, the generation of unwanted products from parent compounds (transformation products, TPs) of often-unknown chemical structure, fate and toxicity. In many countries, effluent treatment is available only rarely if at all let alone advanced treatment. The past should teach us, that focusing only on technological approaches is not constructive for a sustainable water quality control. Therefore, in addition to conventional and advanced treatment optimization more emphasis on input prevention is urgently needed, including more and better control of what is present in the source water. Measures for input prevention are known for long. The main focus though has always been on the treatment, and measures taken at the source have gained only little attention so far. A more effective and efficient approach, however, would be to avoid pollution at the source, which would in turn allow more targeted treatment to meet treated water quality objectives globally. New developments within green and sustainable chemistry are offering new approaches that allow for input prevention and a more targeted treatment to succeed in pollution elimination in and at the source. To put this into practice, engineers, water scientists and chemists as well as microbiologists and scientists of other related disciplines need to cooperate more extensively than in the past. Applying principles such as the precautionary principle, or keeping water flows separate where possible will add to this. This implies not minimizing the efforts to improve wastewater treatment but to design effluents and chemicals in such a way that treatment systems and water environments can cope successfully with the challenge of micropollutants globally (Kümmerer et al., 2018). This paper therefore presents in its first part some of the limitations of effluent treatment in order to demonstrate the urgent need for minimizing water pollution at the source and, information on why source management is urgently needed to improve water quality and stimulate discussions how to protect water resources on a global level. Some principles of green and sustainable chemistry as well as other approaches, which are part of source management, are presented in the second part in order to stimulate discussion.
... [19] With the aim of covering a larger range of polarities, the chemical structures of some degradation products of chloroacetamides were investigated using both GC/MS/MS and LC/MS/MS except for metolachlor for which only TPs characterized by GC/MS/MS have been reported. [19] Gutowski and coworkers [20] have recently compared TPs formed by photolysis of s-metolachlor and its commercial product Mercantor Gold. They concluded that the TPs formed are the same and that the formation of TPs from Mercantor Gold is faster. ...
... [22] All the protonated molecules of metolachlor-D 6 wileyonlinelibrary.com/journal/rcm with those of Gutowski and coworkers [20] shows that many fragment ions are common but not all the molecular ions. For all the photoproducts, the loss of CH 3 OH from MH + in mass spectrometry, combined with the fact that none of the six deuterium atoms are eliminated, demonstrate that the ether function and the adjacent alkyl chain were not affected by irradiation. ...
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. 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. program. 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. 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. Copyright
... Several approaches for the identification of transformation products and their inclusion in chemical safety assessment have been presented [2,4,[13][14][15][16][17]. These typically rely on the use of in silico tools for the prediction and safety assessment of transformation products as a time and cost-effective means to provide useful information where there is a lack of experimental data. ...
... was similar in the SBA after 7 days and the LSA after 28 days, it can be assumed that adsorption of metolachlor reached an equilibrium already during the first days of the experiments. Other studies also report about considerable abiotic losses of pesticides and herbicides via sorption on wood particles(Ilhan et al. 2011;Krause Camilo et al. 2013).(Gutowski et al. 2015) observed a low biodegradability of Smetolachlor of less than 5 % after 28 days. These results agree with our observations. Abiotic loss, total loss, and residue of metolachlor in the SBA after 7 days and in LSA 1 and 2 after 28 days (mean, n=4). No biotic loss could be observed in SBA and LSA2. In LSA1, the biotic/abiotic loss could not ...
We developed, tested, and optimized two laboratory denitrification assays for both managers and scientists to assess the effects of xenobiotics on the denitrification process over 7 days (short batch assay, SBA) and 28 days (long semi-continuous assay, LSA). The assays facilitate (1) measuring the efficiency of the nitrate removal under the influence of xenobiotics, (2) determining the removal of the tested xenobiotic via adsorption or biotic decomposition, and (3) testing influencing parameters for optimizing the denitrification process. The adsorption of the xenobiotic was assessed by inhibiting all biological processes through the addition of HgCl 2 . Our tests demonstrate that the ratio of the initial nitrate concentration to the amount of bioavailable organic matter provided is essential to avoid organic carbon or nitrate limitation. While pH < 7 resulted in decreased denitrification, pH > 8 led to nitrite accumulation, indicating incomplete denitrification. Over durations of more than a week, weekly replenishments of the nitrate and the HgCl 2 , and weekly purging with argon gas to reduce oxygen concentrations are needed. The assays provide information about the accumulation of xenobiotics in the bioreactors necessary for an environmentally friendly treatment of the bioreactor fillings and provide insight into their potential to remove pesticides from polluted water resources.
... The remaining TPs in the bacterial cultures could be of environmental concern because they often show higher toxicity than the parent compound. Increased toxicity of TPs of various xenobiotics has been recently documented (Gutowski et al., 2015;Pacholak et al., 2022;Sosa-Martínez et al., 2020). ...
The purpose of this research was to investigate the biodegradation of nitrofurantoin (NFT), a typical nitrofuran antibiotic of potential carcinogenic properties, by two microbial communities derived from distinct environmental niches - mountain stream (NW) and seaport water (SS). The collected samples represent the reserve of the protected area with no human intervention and the contaminated area that concentrates intense human activities. The structure, composition, and diversity of the communities were analyzed at three timepoints during NFT biodegradation. Comamonadaceae (43.2%) and Pseudomonadaceae (19.6%) were the most abundant families in the initial NW sample. The top families in the initial SS sample included Aeromonadaceae (31.4%) and Vibrionaceae (25.3%). The proportion of the most abundant families in both consortia was remarkably reduced in all samples treated with NFT. The biodiversity significantly increased in both consortia treated with NFT suggesting that NFT significantly alters community structure in the aquatic systems. In this study, NFT removal efficiency and transformation products were also studied. The biodegradation rate decreased with the increasing initial NFT concentration. Biodegradation followed similar pathways for both consortia and led to the formation of transformation products: 1-aminohydantoin, semicarbazide (SEM), and hydrazine (HYD). SEM and HYD were detected for the first time as NFT biotransformation products. This study demonstrates that the structure of the microbial community may be directly correlated with the presence of NFT. Increase in biodiversity of the microbial community does not have to be correlated with an increase in functional capacity, such as the ability to biodegradation because higher biodiversity corresponded to lower biodegradation. Our findings provide new insights into the effect of NFT contamination on aquatic microbiomes. The study also increases our understanding of the environmental impact of nitrofuran residues and their biodegradation.
... Of course these studies are also of importance to understand the biodegradability of ILs and the risk to human and the environment since e.g. transformation products can be more toxic than the parent compound (Gutowski et al., 2015;Hensen et al., 2020;Kümmerer et al., 2019). Therefore, studies investigating the biodegradation pathway or identifying transformation products give further insights into the biodegradation or even mineralisation of the cation and anion, which are complementary to the biodegradation rates measured according to standard methods. ...
Ionic liquids (ILs) are increasingly of interest for environmentally open applications. Therefore, completely mineralizing ILs are highly desirable. We reviewed the current state of knowledge on ILs' environmental biodegradability and identified research needs. Literature data were evaluated as for applied standard methods (e.g. OECD, ISO, APHA) for biodegradation of ILs in order to get an overview on the validity of the test results received and ILs' biodegradability. 109 studies were evaluated. The ILs were categorised based on the cation's core structure. The biodegradation data was classified according to a traffic light system (red: 0–19% degradation, amber: 20–59% degradation, green: ≥ 60% degradation). Not all studies could be assessed for compliance with the test guidelines due to missing test parameters. Moreover, no study discussed all validation criteria as defined by the test guidelines. Consequently, the reliability and quality of the existing biodegradation data is restrained. With regard to the different cations classified for ≥60% biodegradability, phosphonium ILs are the least biodegradable, followed by imidazolium ones. The most ILs that were biodegradable are cholinium ILs. The results indicate the need for more and qualitatively better testing according to standard methods including application and reporting of all validation criteria in order to get reliable data that enables the comparison of the test data and a comprehensive understanding of ILs' biodegradability. Moreover, reliable data allows the selection of sufficiently environmentally biodegradable ILs if an introduction into the environment during use cannot be excluded.
... 55,56 This idea is also supported by the confirmed formation of hydroxy acetochlor and the suggested formation of N-ethyl-N-(2-ethyl-6-methylphenyl)- 57 However, previous experiments with S-metolachlor under oxic nutrient-limiting conditions suggest (L3) the formation of N-ethyl-N-(2-ethyl-6-methylphenyl)-2-hydroxyacetamide without any detection of ethanosulfonic acid. 58 Despite their lower production than the oxalinic acid TPs, acetochlor and S-metolachlor ethanosulfonic acids are chloroacetanilide TPs most frequently detected in the environment. 59,60 The higher mobility, that is, log P ow ≈ 0, of ethanesulfonic acids compared to their parent pesticides and other TPs (log P ow between 2 and 3; Table S7) has been assumed to control their concentration dynamics in surface water. ...
Current approaches are often limited to evaluating the contribution of pesticide dissipation processes in water-sediment systems as both degradation and phase transfer, that is, sorption-desorption, contribute to the apparent decrease of pesticide concentration. Here, the dissipation of widely used herbicides acetochlor and S-metolachlor was examined in laboratory by water-sediment microcosm experiments under oxic and anoxic conditions. Compound-specific isotope analysis (CSIA) emphasized insignificant carbon isotope fractionation in the sediment, indicating prevailing pesticide degradation in the water phase. Conceptual modeling accounting for phase transfer and biodegradation indicated that biodegradation may be underestimated when phase transfer is not included. Phase transfer does not affect carbon isotope fractionation for a wide spectrum of molecules and environmental conditions, underscoring the potential of pesticide CSIA as a robust approach to evaluate degradation in water-sediment systems. CSIA coupled with the identification of transformation products by high-resolution tandem mass spectrometry suggests the degradation of acetochlor and S-metolachlor to occur via nucleophilic substitution and the predominance of oxalinic acids as transformation products under both anoxic and oxic conditions. Altogether, combining the pesticide CSIA, the identification of transformation products, and the use of conceptual phase-transfer models improves the interpretation of pesticide dissipation in water-sediment systems.
... Studies compared the predictions of the EPI suite with the biodegradation assays according to the OECD test guideline. These studies concluded that the predictions were in agreement with the results of these tests when studying the TPs of organic pollutants formed by the photodegradation (Gutowski et al., 2015;Mahmoud et al., 2013). These results aim to estimate the toxic potential of the formed TPs, since in vitro, in vivo or biodegradation tests were not performed, but showed that the TPs are relevant when studying the degradation of pollutants because they may present toxicity to the ecosystem and human health. ...
Titanate nanomaterials have been outstanding in the removal of emerging contaminants by the photocatalysis process. These photocatalysts, when modified through techniques such as doping with metals, they have advantages over TiO2, especially in the region of visible light. In this work, the photocatalytic performance of four recent reported catalysts, pristine titanate nanowires, cobalt-doped titanate nanowires, iron-doped titanate nanowires and ruthenium-doped titanate nanowires, for the removal of the antidepressant trazodone under visible light radiation was compared. The iron-doped titanate nanowires presented the best catalytic activity by the catalyst surface area. Additionally, thirteen transformation products (TPs) were identified by high-resolution mass spectrometry and, to the best of our knowledge, nine of them have never been described in the literature. It was shown that for each catalyst different TPs were formed with distinct time profiles. Finally, toxicity assessment by computational methods showed that TPs were not readily biodegradable and they presented toxicity to aquatic organisms with mutagenic potential. These findings reinforce the importance of taking into consideration the TPs formed during the removal of pollutants since many of them may be toxic and can be produced during photocatalysis.
... Of course these studies are also of importance to understand the biodegradability of ILs and the risk to human and the environment since e.g. transformation products can be more toxic than the parent compound (Gutowski et al., 2015;Hensen et al., 2020;Kümmerer et al., 2019). Therefore, studies investigating the biodegradation pathway or identifying transformation products give further insights into the biodegradation or even mineralisation of the cation and anion, which are complementary to the biodegradation rates measured according to standard methods. ...
Silicones have many applications and are produced in large quantities. Despite their potential toxicity, information on their environmental mineralisation is scarce. Therefore, we investigated a group of five organosilicon compounds (o-MeOC6H4SiMe3 (1), p-MeOC6H4SiMe3 (2), (p-MeOC6H4)2SiMe2 (3), o-Me2NC6H4SiMe3 (4) and p-Me2NC6H4SiMe3 (5)), recently developed to be ‘benign by design’ based on their readily degradable core structure. Five different degradability tests were performed, one assessing hydrolytic and two analysing biological and photolytic stability, respectively.
All substances, except (p-MeOC6H4)2SiMe2 (3), hydrolysed within 24 hours to 50% indicating that this is one of the major pathways of their primary elimination. In agreement with previous research, none of the substances was readily biodegradable. In contrast, 99% of p-Me2NC6H4SiMe3 (5) was primarily eliminated by photolytic and hydrolytic processes. The elimination rates of the other substances ranged from 7% to 64%. Irradiation at shorter wavelengths increased both the extent and speed of photodegradation.
Eleven transformation products of p-Me2NC6H4SiMe3 (5) were detected, all of which were completely eliminated within 64 min of irradiation with a Hg lamp (200–400 nm). The insertion of an electron-donating group on the benzene ring like in p-Me2NC6H4SiMe3 (5) clearly enhanced photolytic degradability but further research is necessary to achieve truly biodegradable silicones.
... Metolachlor has significant solubility in water (530 mg l −1 at 20 °C) and mobility, and a low log K oc (3.01) [15]. Its advanced oxidation by photolysis, photo-assisted Fenton reaction, ozonation, combination of ozone and hydrogen peroxide has been described in the literature [16][17][18][19][20][21]. A detailed product study of metolachlor airplasma induced oxidation in a DBD reactor has been recently completed in our laboratory [22]. ...
There is a long-time interest in non-thermal plasma research applied to different environmental issues. We have recently developed a reactor for water treatment by air non-thermal plasma, which can be energized by either DC (positive or negative polarity) or AC high voltage. This paper reports and discusses the results of a study in which the performance of this reactor was tested under the three discharge regimes, DC- and DC+ corona and DBD. Comparative experiments were carried out to characterize the system with regard to ROS (OH radicals, hydrogen peroxide and ozone) production and efficiency of treatment of the persistent herbicide metolachlor. DC- discharges turned out to be significantly more effective in the production of ROS than either DC+ and DBD: higher ozone and hydrogen peroxide concentrations were obtained at any given energy input and OH radical formation was more efficient. Specifically, the rate of OH radical formation was (16.2 ± 1.2), (6.34 ± 0.11) and (4.15 ± 0.13) μM kJ-1 for DC-, DBD and DC+, respectively. In view of these findings, it was not surprising that DCdischarge regime sustained the most efficient process of metolachlor removal. The efficiency was evaluated considering the decay of metolachlor concentration as a function of time and of energy input, the G50 parameter and the extent of mineralization achieved. The results clearly show that according to all these indicators DC- discharges appear to be the best choice among the three which can be implemented in this reactor. HPLC/UV-MS analyses revealed that, regardless of the type of discharge employed, the same oxidation intermediates are formed from metolachlor, although at different rates depending on the discharge type. These observations therefore suggest that the same mechanisms and reactive species are probably involved in the degradation of metolachlor by DC-, DC+ and DBD air non-thermal plasma.
... Due to the excessive use of these products, there is a widespread contamination of water, soil and air. For example, many studies [3][4][5] revealed the presence of insecticides in the atmosphere, in the fog, in droplets rain, in surface water and groundwater. Several studies on the contamination of food products revealed the presence of unacceptable levels of insecticide residues in food products such as cereals, vegetables, fruits, fish, milk, tea, honey and medicinal herbs [6,7]. ...
With the growing number of insecticides that can potentially contaminate the environment, the determination of their acute
mammalian toxicity is of prime importance in risk assessment. Chemoinformatics presents an alternative to animal testing
because laboratory tests are costly in time and money and actively opposed by animal rights activists. In this work, the
Quantitative Structure-Toxicity Relationship (QSTR) model established by using the artificial neural network (ANN) has been
used for estimating the acute oral toxicity (LD50) of these insecticides to male rats. The 123 insecticides of the training set and
the sixteen insecticides of external testing set have been described by means of using molecular descriptors. The QSTR model
was validated internally and externally. A good results (Q2 =0.96 and Q2ext =0.95) were obtained. The prediction results are in
good agreement with the experimental values of LD50.
... CBT was performed according to the OECD-guidelines 301D. Inoculum was received from the municipal waste water treatment plant of Lüneburg (EWG = 70 000) (Gutowski et al. 2015). To obtain a theoretical oxygen demand of 5 mg L -1 a start concentration of OIT of 2.18 mg L −1 and of its photolytic mixture were prepared. ...
Pesticides like biocidal products are applied to urban outdoor materials. Due to rain events applied biocides are leached out and spread into the aqueous environment. Many processes like biodegradation and photolysis lead to the degradation and transformation of substances. Aqueous photolysis of the analyzed biocide octhilinone (OIT) leads to the degradation with a quantum yield of Φ = 0.01 under simulated solar radiation. Biodegradation of the initial substance compared to the photolytic mixture shows an increased biological activity. Toxic effects on luminescent bacteria could be observed in low concentration ranges below 1 µg L-1. This research demonstrates that new insights on the fate and behavior of TPs in the aquatic environment are necessary to provide the assessment of risk potential and the development of water pollution control measures.
... Among non-target organisms, soil microorganisms are extremely important, since they are a key component in soil ecosystems, dominating cycling of nutrient element and playing a major role in maintaining soil quality. The impact of S-metolachlor on aquatic system and wetlands, dissipation and leaching have been studied over the past years [4,5,6,7]. ...
S-metolachlor is a promising alternative to metolachlor. However, the extensive use of S-metolachlor as herbicide in vegetable fields in China has caused concerns about its environmental fate. Here we investigated the effects of temperature, relative humidity (RH) and PH on the degradation rate of S-metolachlor in vegetable soil. The degradation rates of S-metolachlor increased with increasing temperatures and RH and either acidic or basic PH facilitates S-metolachlor degradation. The degradation of S-metolachlor under these conditions followed the first-order kinetics resulting in the half-lives (T-1/2) ranging from 12.18 d to 70.71 d at 5–35°C, and 27.28 d to 53.72 d at RH 30–90%; and 29.62–19.69 d at pH 6–8. Stronger response of soil enzymes including catalase, dehydrogenase, urease and cellulase to S-metolachlor was detected in soil with high organic matter. PLFA profiles showed that, totally, the microbe populations including actinomycetes, fungi and bacteria increased gradually in the first 14 days after the treatment and decreased from 14d to 28d after the treatment. All the S-metolachlor treatments caused the increase of aerobe and anaerobe. High S-metolachlor concentration, 13.9 mg/kg, could cause significant variation at the first 2 weeks, stimulating growth of the entire soil microbial community. These findings might have practical implications for the fate of S-metolachlor residue in vegetable fields. Environmental factors, especially temperature, relative humidity and pH should be considered in combination with the appropriate application dose of S-metolachlor for achieving satisfactory weed-control efficacy, reducing runoff, and minimizing effects on environmental quality.
... Various kinds of pharmaceutically active compounds (PhACs) have been detected in samples from aquatic environments, such as wastewater, coastal water, surface water, and even drinking water, and their main pathway is known as the effluent of wastewater treatment plants (Verlicchi et al., 2012;Liu and Wong, 2013;Godoy et al., 2015). The "pseudo-persistence" of PhACs in water environments can result in potentially adverse effects on aquatic communities and humans, even at trace environmental concentrations (Fent et al., 2006;Corcoran et al., 2010;Gutowski et al., 2015). Consequently, the control of such emerging pollutants in effluent has been one of the major global concerns. ...
... Taken together, degradative processes largely contributed to S-MET dissipation under both continuous-flow and batch mode, and prevailed over sorption and plant uptake. The extent of S-MET degradation in the wetlands contrasts with recent laboratory experiments highlighting low biodegradability (<5% after 28 days) and high photodegradation (about 75% after 8 h of radiation with Xe lamp) of S-MET in Mercantor Gold ® (Gutowski et al., 2015b). In our case, photodegradation of S-MET was limited due to transient ponding and fast infiltration into the wetland whereas biodegradation may prevail. ...
Pesticide dissipation in wetland systems with regard to hydrological conditions and operational modes is poorly known. Here, we investigated in artificial wetlands the impact of batch versus continuous-flow modes on the dissipation of the chiral herbicide S-metolachlor (S-MET) and hydrological tracers (bromide, uranine and sulforhodamine B). The wetlands received water contaminated with the commercial formulation Mercantor Gold(®) (960 g L(-1) of S-MET, 87% of the S-enantiomer). The tracer mass budget revealed that plant uptake, sorption, photo- and presumably biodegradation were prominent under batch mode (i.e. characterized by alternating oxic-anoxic conditions), in agreement with large dissipation of S-MET (90%) under batch mode. Degradation was the main dissipation pathway of S-MET in the wetlands. The degradate metolachlor oxanilic acid (MOXA) mainly formed under batch mode, whereas metolachlor ethanesulfonic acid (MESA) prevailed under continuous-flow mode, suggesting distinct degradation pathways in each wetland. R-enantiomer was preferentially degraded under batch mode, which indicated enantioselective biodegradation. The release of MESA and MOXA by the wetlands as well as the potential persistence of S-MET compared to R-MET under both oxic and anoxic conditions may be relevant for groundwater and ecotoxicological risk assessment. This study shows the effect of batch versus continuous modes on pollutant dissipation in wetlands, and that alternate biogeochemical conditions under batch mode enhance S-MET biodegradation.
... Furthermore, if these TPs turn out to be persistent, they will be of special interest for environmental risk assessment. Laboratory tests to identify the combined effect of photolysis and aerobic biodegradation on the formation of persistent TPs were successfully applied for two formulations of herbicide pesticides (Gutowski et al., 2014). However such, studies have not yet been performed for UR. ...
The widespread use of pesticides threatens the environment and ecosystems. Despite the positive effects of plant protection products, pesticides also have unexpected negative effects on nontarget organisms. The microbial biodegradation of pesticides is one of the major pathways for reducing their risks at aquatic ecosystems. The objective of this study was to compare the biodegradability of pesticides in simulated wetland and river systems. Parallel experiments were conducted with 17 pesticides based on the OECD 309 guidelines. A comprehensive analytical method, such as target screening combined with suspect and non-target screening, was performed to evaluate the biodegradation via identification of transformation products (TPs) using LC-HRMS. As evidence of biodegradation, we identified 97 TPs for 15 pesticides. Metolachlor and dimethenamid had 23 and 16 TPs, respectively, including Phase II glutathione conjugates. The analysis of 16S rRNA sequences for microbials characterized operational taxonomic units. Rheinheimera and Flavobacterium, which have the potential for glutathione S-transferase, were dominant in wetland systems. Estimation of toxicity, biodegradability, and hydrophobicity using QSAR prediction indicated lower environmental risks of detected TPs. We conclude that the wetland system is more favorable for pesticide degradation and risk mitigation mainly attributed to the abundance and variety of the microbial communities.
In this study, abiotic transformation of an important strobilurin fungicide, kresoxim-methyl, was investigated under controlled laboratory conditions for the first time by studying its kinetics of hydrolysis and photolysis, degradation pathways and toxicity of possibly formed transformation products (TPs). The results indicated that kresoxim-methyl showed a fast degradation in pH9 solutions with DT50 of 0.5 d but relatively stable under neutral or acidic environments in the dark. It was prone to photochemical reactions under simulated sunlight, and the photolysis behavior was easily affected by different natural substances such as humic acid (HA), Fe3+and NO3-which are ubiquitous in natural water, showing the complexity of degradation mechanisms and pathways of this chemical compound. The potential multiple photo-transformation pathways via photoisomerization, hydrolyzation of methyl ester, hydroxylation, cleavage of oxime ether and cleavage of benzyl ether were observed. 18 TPs generated from these transformations were structurally elucidated based on an integrated workflow combining suspect and nontarget screening by high resolution mass spectrum (HRMS), and two of them were confirmed with reference standards. Most of TPs, as far as we know, have never been described before. The in-silico toxicity assessment showed that some of TPs were still toxic or very toxic to aquatic organisms, although they exhibit lower aquatic toxicity compared to the parent compound. Therefore, the potential hazards of the TPs of kresoxim-methyl merits further evaluation.
Paichongding (IPP) and cycloxaprid (CYC) have been effectively used as the alternative products of imidacloprid (IMI) against IMI-resistant insects and exhibit a great market potential. However, risk assessment of IPP and CYC for non-target organisms, especially ecological risk assessment for non-target aquatic organisms, is still lacking. Here, we predicted the toxicity and potential risks of IPP, CYC, and their transformation products (TPs) to hydrobionts. The results indicated that IPP and CYC could generate 428 and 113 TPs, respectively, via aerobic microbial transformation. Nearly half of the IPP TPs and nearly 41 % of the CYC TPs exhibited high or moderate toxicity to Daphnia or fish. Moreover, we found that IPP, CYC, and 80 TPs of them posed potential risks to aquatic ecosystems. Almost all harmful TPs contained a 6-chloropyridine ring structure, suggesting that this structure may be associated with the strong toxicity of these TPs to aquatic organisms, and these TPs (IPP-TP2 or CYC-TP2, IPP-TP197 or CYC-TP71, IPP-TP198 or CYC-TP72, and IPP-TP212 or CYC-TP80) may appear in aquatic environments as final products. The risks posed by these TPs to aquatic ecosystems require more attention. This study provides insights into the toxicity and ecological risks of IPP and CYC.
Chiral pesticides are unique hazardous materials. Here, we systematically studied the potentially harmful products of enantioselective indoxacarb degradation throughout tea growth, processing, and brewing and tested their toxicity to tea geometrid larvae and honeybees. The half-lives of S-indoxacarb and R-indoxacarb during tea growth were 2.6 d and 3.3 d, respectively. There was a trend toward the production of S-indoxacarb from R-indoxacarb. The degradation products IN-JT333, IN-MK638, IN-MF014, and IN-KG433 were also characterized in tea growth and processing and detected. IN-JT333, previously known as a direct insecticidal compound produced by the enzymatic transformation of indoxacarb in insects, was first found in plant samples. The fixation and rolling of green tea and the rolling of black tea were the most important steps that affected indoxacarb and its degradation products. The leaching rates of R-indoxacarb and S-indoxacarb were slightly higher in green tea than in black tea. The maximum leaching rates of IN-MK638 and IN-MF014 during the brewing process reached 89.9% and 94.1%, respectively. Contact toxicity tests with honeybees and tea geometrid larvae in the lab showed that the relative toxicities of the compounds could be ranked as follows: S-indoxacarb > indoxacarb (3S + 1R) ≫ R-indoxacarb. TEST toxicity predictions showed that relative toxicities were ranked IN-KG433 > indoxacarb > IN-JT333 > IN-MK638 > IN-MF014. The toxicity of the degradation product IN-KG433 is higher than that of indoxacarb itself, and its maximum leaching rate is as high as 88.2%. It therefore transfers readily from processed tea to the tea infusion during the brewing process. These findings indicate the need to pay attention to the risk of metabolites and enantiomeric differences and provide new, comprehensive insight into the risk factors for indoxacarb in tea and are relevant to the study of other chiral pesticides.
Knowledge of direct and indirect photodegradation of pesticides and associated isotope fractionation can help to assess pesticide degradation in surface waters. Here, we investigated carbon (C) and nitrogen (N) isotope fractionation during direct and indirect photodegradation of the herbicides atrazine and S-metolachlor in synthetic water, mimicking agriculturally impacted surface waters containing nitrates (20 mg L–1) and dissolved organic matter (DOM, 5.4 mgC L–1). Atrazine and S-metolachlor were quickly photodegraded by both direct and indirect processes (half-lives <5 and <7 days, respectively). DOM slowed down photodegradation while nitrates increased degradation rates. The analysis of transformation products showed that oxidation mediated by hydroxyl radicals (HO•) predominates during indirect photodegradation. UV light (254 nm) caused significant C and N isotope fractionation, yielding isotopic fractionation values ε_C = 2.7 ± 0.3 and 0.8 ± 0.1‰, and ε_N = 2.4 ± 0.3 and –2.6 ± 0.7‰ for atrazine and S-metolachlor, respectively. In contrast, photodegradation under simulated sunlight led to negligible C and slight N isotope fractionation, indicating the effect of the radiation wavelengths on the isotope fractionation induced by direct photodegradation. Altogether, these results highlighted the importance of using simulated sunlight to obtain environmentally-relevant isotopic fractionation values to help distinguish photodegradation from other degradation pathways in surface waters.
A novel and accurate liquid chromatography–tandem mass spectrometry method was developed to sequentially determine three persistent herbicides (atrazine (ATZ), acetochlor (ACE), and metolachlor (MET)) and seven characteristic metabolites (desethylatrazine (DEA), deisopropylatrazine (DIA), diaminochlorotriazine (DACT), MET–oxanilic acid (MET-OA), MET-ethanesulfonic acid (MET-ESA), ACE-ESA, and ACE-OA) in fresh fish tissues from six fish species. A modified QuEChERS method was conducted to extract the target compounds from fish tissues. Matrix-matched calibrations of the target analytes were carried out at spiking levels of 1, 10, 100, and 1000 ng g⁻¹. The method was validated in accordance with Codex guidelines (CAC/GL 71–2009). Recoveries for the target analytes were 67–120% with relative standard deviations below 20%, and the matrix effects ranged from −58.7% to 59.3%. The limits of detection and quantitation were 0.01–1.90 and 0.02–6.35 ng g⁻¹, respectively. Moreover, the method was successfully applied to analyze the concentrations of the target chemicals in fresh tissue samples of six fish species (n = 67) collected from four markets in Nanning City, Guangxi Province, China. The concentrations in all samples were 1.1–140.5 ng g⁻¹. Interestingly, this study was the first to measure DEA and DIA in fish liver, and their highest concentrations were 10.7 and 14.2 ng g⁻¹, respectively. This method provides a basis for studying the pathways of biotransformation, bioaccumulation, detoxification, and exposure patterns of ACE, ATZ, MET, and their metabolites in aquatic environments.
Herbicides are an important crop protection technology of modern agriculture. However, their application over large extensions of land generates diffuse pollution sources that are not only difficult to monitor and control, but also that threaten the quality of human water resources and river ecosystems world-wide. Although field assessments and laboratory tests are required before active ingredients are introduced to market, the fate and degradation extent of pesticides and their metabolites in the environment is subject to significant uncertainty. This thesis work establishes a proof of concept for the application of compound specific isotope analysis (CSIA) to monitor pesticide degradation and transfer at catchment scale. The thesis includes both field characterization and numerical modelling to investigate the value of CSIA as a monitoring tool and as a model uncertainty reduction technique. Laboratory experiments are further employed to support interpretation of field data and validate numerical model structure development.
Prior to registration, careful assessment of transformation products (TPs) that are more toxic than their parent compounds is required, and EU regulations require greater use of non-animal test methods and risk assessment strategies. Predicting the toxicity of transformation products and chemical mixtures is a major challenge for modern toxicology. Since the metabolic processes of transformation products and toxic effects of chemical mixtures involve complex mechanisms, it is essential to use in silico modeling methods to consider different chemico-biological interactions of metabolic transformation and mixture toxicity. This chapter reviews previous modeling methods used to study pesticide metabolites and mixtures.
Biocides are, inter alia, applied as preservatives on facades to prevent the growth of microorganisms. Their incomplete mineralization results in new compounds, so-called transformation products (TPs). Rain causes that both applied biocides and their TPs leach from facades with stormwater into the urban aquatic environment. This study is the first to investigate the introduction of the biocides Diuron, Terbutryn, and Octylisothiazolinone (OIT) and their TPs into the groundwater via urban stormwater infiltration systems. In this study, the TPs of these biocides were created by laboratory photolysis and elucidated using LC-HRMS. The results were then used to analyze TPs by LC-MS/MS in stormwater and groundwater samples, which were taken from an urban swale-trench system and from groundwater wells upgradient and downgradient of the infiltration system. A sprinkling experiment was conducted to evaluate facades as a contamination source. Biodegradation tests were conducted to determine bio-persistence of biocides and their TPs. Fourteen TPs were identified under laboratory photolysis. TP-186, TP-210, and TP-256 of Terbutryn were hitherto unknown. Nine TPs were qualitatively detected in environmental water samples. Parent compounds, TP-219 of Diuron and TP-212, TP-214, and TP-226 of Terbutryn were detected at a maximum concentration of 140 ng L-1 during stormwater events. Concentrations in groundwater were considerably below German drinking water limits, but were higher in groundwater samples downgradient from the investigated swale-trench system than in those collected upgradient. Neither the biocides nor most of their TPs were readily biodegradable under simulated surface water conditions. The results show that entry of biocides and their TPs into groundwater is caused by infiltration of urban stormwater.
Complex environmental mixtures consist of hundreds to thousands of unknown and unregulated organic compounds that may have toxicological relevance, including transformation products (TPs) of anthropogenic organic pollutants. Nontargeted analysis and suspect screening analysis offer analytical approaches for potentially identifying these toxic transformation products. However, additional tools and strategies are needed to reduce the number of chemicals of interest and focus analytical efforts on chemicals that may pose risks to humans and the environment. This brief review highlights recent developments in this field and suggests an integrated framework that incorporates complementary instrumental techniques, computational chemistry, and toxicity analysis, for prioritizing and identifying toxic TPs in the environment.
To prevent water shortages in the future and to reduce domestic water consumption, decentralized grey water (GW) reuse has become increasingly important. This water has, however, to be free of pollutants. Conventional treatment of GW does not fully eliminate micropollutants such as the UV filter substance ethylhexyl methoxycinnamate (EHMC). EHMC, which is commonly used in sunscreens and personal care products, is an endocrine disruptor and shows potential to bioaccumulation, which is also reflected in its low water solubility. Photolysis has been proposed as an alternative treatment method for other micropollutants, but it is not clear yet whether it can also be used to eliminate EHMC. One goal of this study was to better understand the basic pathways involved in this process. It aimed to identify photo-transformation products (photo-TPs) by using, in the test conditions, an initial concentration of EHMC higher than those expected in the environment. Acetonitrile (ACN) was added in low concentrations to the aqueous solution to overcome the low aquatic solubility of EHMC. The influence of this co-solvent on the degradation kinetics was studied. The photolysis experiments were carried out using a medium pressure mercury lamp, which emits UV light in the range of 200–400 nm. The quantum yield of the photolysis of EHMC was 0.0042 and 0.0023 mol·Einstein− 1 (for 0.2 and 0.5% ACN (v/v), respectively), and the relative and absolute UV photon fluxes were determined. HPLC was used to monitor the elimination kinetics of EHMC, which followed first-order kinetics. The results of LC-MSn analyses revealed that beside others, several oxidized and hydroxylized EHMC isomers were formed as photo-TPs in aqueous solution. Using a set of in silico quantitative structure-activity relationship (QSAR) models, this study also offered new insights concerning the environmental fate and toxicity of the TPs of EHMC.
Photocatalytic-assisted ozone degradation of metolachlor (MTLC) aqueous solutions was investigated using neat TiO2 (prepared by sol-gel method) and TiO2/carbon composite (prepared from commercial available metal oxide and carbon phase) as catalysts. In terms of MTLC degradation, O3 on its own is enough to achieve 100% removal, but the introduction of light increased the rate of removal. On the other hand, the combination of O3 with light and the tested catalysts is mandatory to reach high mineralization in short reaction times. After 60 min of reaction, the TOC removal was 87% and 75% in the presence of the prepared composite and TiO2, respectively. The concentration of two short chain carboxylic acids, oxalic and oxamic acids, was followed during MTLC degradation. The amount of these acids decreased when O3 and light were combined.
In general, nitrogen ions, such as nitrate and ammonium, were detected in the studied processes. All treatments released ammonium and light based processes also produced nitrate.
Microtox® analysis showed that the combined process in the presence of the prepared catalysts led to a remarkable reduction in the toxicity of the treated solution, decreasing the inhibition of luminescent activity of Vibrio Fisheri from 74% to 12%.
Desipramine (DMI) is a widely used tricyclic antidepressant, and it is the major metabolite of imipramine (IMI) and lofepramine (LMI); IMI and LMI are two of the most commonly used tricyclic antidepressants. If DMI enters the aquatic environment, it can be transformed by the environmental bacteria or UV radiation. Therefore, photolysis of DMI in water was performed using a simulated sunlight Xenon-lamp and a UV-lamp. Subsequently, the biodegradability of DMI and its photo-transformation products (PTPs) formed during its UV photolysis was studied. The influence of variable conditions, such as initial DMI concentration, solution pH, and temperature, on DMI UV photolysis behavior was also studied. The degree of mineralization of DMI and its PTPs was monitored. A Shimadzu HPLC-UV apparatus was used to follow the kinetic profile of DMI during UV-irradiation; after that, ion-trap and high-resolution mass spectrometry coupled with chromatography were used to monitor and identify the possible PTPs. The environmentally relevant properties and selected toxicity properties of DMI and the non-biodegradable PTPs were predicted using different QSAR models. DMI underwent UV photolysis with first-order kinetics. Quantum yields were very low. DOC values indicated that DMI formed new PTPs and was not completely mineralized. Analysis by means of high-resolution mass spectrometry revealed that the photolysis of DMI followed three main photolysis pathways: isomerization, hydroxylation, and ring opening. The photolysis rate was inversely proportional to initial DMI concentration. The pH showed a significant impact on the photolysis rate of DMI, and on the PTPs in terms of both formation kinetics and mechanisms. Although temperature was expected to increase the photolysis rate, it showed a non-significant impact in this study. Results from biodegradation tests and QSAR analysis revealed that DMI and its PTPs are not readily biodegradable and that some PTPs may be human and/or eco-toxic, so they may pose a risk to the environment.
The use of herbicides is increasing around the world. The benefits achieved by the use of these herbicides are indisputable. Despite their importance in agriculture, herbicides can be dangerous to the environment and the human health, depending on their toxicity, and the degree of contamination. Also, it is essential and evident that the risk assessment of herbicides is an important task in the environmental protection. The objective of this work was to investigate and implement an Artificial Neural Network (ANN) model for the prediction of acute oral toxicity of 77 herbicides to rats. Internal and external validations of the model showed high Q2 and r m 2 - values, in the range 0.782 – 0.997 for the training and the test. In addition, the major contribution of the current work was to develop artificial neural network-based equation to predict the toxicity of 13 other herbicides; the mathematical equation using the weights of the network gave very significant results, leading to an R2 value of 0.959. The agreement between calculated and experimental values of acute toxicity confirmed the ability of ANN-based equation to predict the toxicity for herbicides that have not been tested as well as new herbicides
Pesticides are transported from agricultural fields into surface and groundwater bodies and can harm associated ecosystems. In particular, the ecological and hydrological functions of many small water bodies are endangered due to their large contact area with agricultural fields. In this review, data on pesticide concentrations in small German water bodies have been collected to assess current risk. The database consists of 53,762 datasets from 765 water samples. The database is very heterogeneous, reflecting variable sampling regimes and the amount and types of pesticide used. Furthermore, the studies are clustered in selected regions and are not comprehensive across Germany. Data analysis reveals that most concentrations are < 0.05 mu g L-1. However, concentrations up to 130 mu g L-1 are also reported. More than 55% of all samples contain multiple-pesticide contaminations with up to 36 pesticide detections per sample. Environmental quality standards are exceeded in 274 concentrations. Among the 15 most frequently detected pesticides, five pesticide transformation products are found. Data for small standing water bodies represent just 1 % of the total database. Since the database is not representative, further analyses were not carried out.
Herbicide metolachlor (MET) and insecticide buprofezin (BUP) were determined in natural waters by means of a newly-developed, simple and sensitive thermochemically-induced fluorescence derivatization (TIFD) method. The TIFD approach is based on the thermolysis transformation of naturally non-fluorescent pesticides into fluorescent complex O-phthalaldehyde-thermoproduct(s) in water at 70 °C for MET and at 80 °C for BUP. The TIFD method was optimized with respect to the temperature, pH, complex formation kinetic and pesticides concentrations. The limit of detection (LOD=0.8 ng mL-1 for MET and 3.0 ng mL-1 for BUP) and quantification (LOQ=2.6 ng mL-1 for MET and 9.5 ng mL-1 for BUP) values were low, and the relative standard deviation (RSD) values were small (between 1.2 and 1.8%), which indicates a good analytical sensitivity and a great repeatability of TIFD method. Recovery studies were performed on spiked well, sea and draining waters samples collected in the Niayes area by using the solid phase extraction (SPE) procedure. Satisfactory recovery results (84-118%) were obtained for the determination of MET and BUP in these natural waters.
The budding yeast Saccharomyces cerevisiae represents a well-consolidated and widely used eukaryotic model, with a number of features that make it an ideal organism to carry out functional toxicological studies. Several advantages are permitted by the use of yeast cells, as the possibility to identify molecular biomarkers, unknown mechanisms of action and novel potential targets. Thanks to the evolutionary conservation, yeast can provide also useful clues allowing the prioritization of more complex analyses and toxicity predictions in higher eukaryotes. The last two decades were incredibly fruitful for yeast "omics", but referring to the analysis of the effects of pesticides on yeast much still remains to be done. Furthermore, a deeper knowledge of the effects of environmental pollutants on biotechnological processes associated with the use of yeasts is to be hoped.
Purpose of this pilot study is to test the QSAR expert system CASE Ultra for adverse effect prediction of drugs. 870 drugs from the SIDER adverse effect dataset were tested using CASE Ultra for carcinogenicity, genetic, liver, cardiac, renal and reproductive toxicity. 47 drugs that were withdrawn from market since the 1950s were also evaluated for potential risks using CASE Ultra and compared them with the actual reasons for which the drugs were recalled. For the whole SIDER test set (n=870), sensitivity and specificity of the carcinogenicity predictions are 66.67 % and 82.17 % respectively; for liver toxicity: 78.95 %, 78.50 %; cardiotoxicity: 69.07 %, 57.57 %; renal toxicity: 46.88 %, 67.90 %; and reproductive toxicity: 100.00 %, 61.10 %. For the SIDER test chemicals not present in the training sets of the models, sensitivity and specificity of carcinogenicity predictions are 100.00 % and 88.89 % respectively (n=404); for liver toxicity: 100.00 %, 51.33 % (n=115); cardiotoxicity: 100.00 %, 20.45 % (n=94); renal toxicity: 100.00 %, 45.54 % (n=115); and reproductive toxicity: 100.00 %, 48.57 % (n=246). CASE Ultra correctly recognized the relevant toxic effects in 43 out of the 47 withdrawn drugs. It predicted all 9 drugs that were not part of the training set of the models, as unsafe.
The benefits of global pesticide use come at the cost of their widespread occurrence in the environment. An array of abiotic and biotic transformations effectively removes pesticides from the environment, but may give rise to potentially hazardous transformation products. Despite a large body of pesticide degradation data from regulatory testing and decades of pesticide research, it remains difficult to anticipate the extent and pathways of pesticide degradation under specific field conditions. Here, we review the major scientific challenges in doing so and discuss emerging opportunities to identify pesticide degradation processes in the field.
The aim of this work was to study herbicide degradation through selected microorganisms from humus and soil subjected to different plantation systems. The following bacterial species were identified: Klebsiella pneumoniae pneumoniae GC s.B strain 1, Pseudomonas alcaligenes, Enterobacter aerogenes GC s.A and Klebsiella pneumoniae pneumoniae GC s.B strain 2. Growth studies yet suggested the possibility of a very long lag phase. Although, culture with the herbicide presented biofilm formation and there were color changes in the herbicide that could have interfered with the espectrophotometry readings. After 5 days of incubation at 35ºC, the difference in the concentration of herbicide was 14.42% on average and after 10 days, 35.01%.
The environmental fate of transformation products from organic pollutants such as drugs has become a new research area of increasing interest over the last few years. Whereas in the past mainly parent compounds or their major human metabolites were studied, new questions have arisen what compounds could be formed during incomplete degradation in the aquatic environment and what effects the resulting transformation products might have on nature and mankind. Psychiatric drugs are among the most important prescription drugs worldwide, but so far only little data is provided upon their degradation behavior. This especially accounts for tricyclic antipsychotic drugs of the phenothiazine class. Therefore, the degradation of such drugs was investigated in this study. In this study the aerobic Closed Bottle test (The Organisation for Economic Co-operation and Development (OECD) 301D) was used to assess the ready biodegradability of three trifluoromethylated phenothiazine drugs: fluphenazine, triflupromazine, and trifluoperazine. As it is known from literature that phenothiazine drugs can easily form various photolytic transformation products under light exposure, photochemical transformation was also investigated. Since transformation products are usually not available commercially, the calculation of environmental parameters with the aid of quantitative structure activity relationship (QSAR) software was used for first evaluation of these compounds. According to the OECD test guideline, all trifluoromethylated phenothiazines had to be classified as not readily biodegradable. Chromatographic data revealed the formation of some transformation products. Comparing retention time and mass spectrometric data with the analytical results of the light exposure experiments, we found peaks with the same retention time and mass spectra. So these transformation products were not of bacterial, but photolytic, origin and are formed very quickly even under low light doses. A special chromatographic column and solvent gradient along with multiple stage mass spectrometric fragmentation experiments uncovered the presence of, in total, nine photolytic transformation products and allowed for their structural elucidation. Typical modifications of the molecules were sulfoxidation, exocyclic N-oxidation, and transformation of the trifluoromethyl to a carboxylic moiety. The obtained results of the QSAR calculations show that all transformation products are highly mobile in the aquatic environment and elimination through biotic or abiotic pathways cannot be expected. Transformation products of trifluoromethylated phenothiazine drugs have to be expected in the aquatic environment, yet nothing is known about their toxicological properties. Therefore, further risk assessment upon these drugs and their fate is strongly recommended.
The chemical and photochemical stability of the herbicide metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] was determined in organic-free water and lake water containing various solutes. Metolachlor was fairly stable in lake water in the dark, with < 4% loss after 100 days. Sunlight photodegradation of metolachlor was faster than purely chemical degradation but was still a relatively slow process, with estimated near-surface half-lives in the lake water of 22 calendar days in summer and 205 calendar days in winter at 40o N latitude. In 5 mg/L solution of dissolved organic matter, the estimated half-lives were 2-3 times longer, depending upon the season. Four dechlorinated photoproducts were identified in lake water, accounting, after 40 days of sunlight irradiation, for 18% of the metolachlor originally present. These products resulted from dechlorination, hydroxylation,dehydrochlorination with subsequent morpholine ring formation, and N-dealkylation.
A large variety and quantity of pesticides are continuously discharged into the environment worldwide. Once they reach the environment, they are subject to biotic or abiotic transformation processes. Photodegradation can be regarded as one of the most crucial factors affecting the fate of pesticides in the environment. However, these photodegradation processes may lead to the formation of unexpected transformation products (TPs), sometimes more toxic and persistent than the parent compounds. Little information is available yet about these TPs and their environmental impact, so this is becoming an essential topic for the environmental risk assessment of the parent compounds. This chapter reviews some aspects of interest related to the studies of identification of these TPs and the establishment of transformation routes to give new perspectives on their occurrence, fate and potential effects on the environment. Recent trends in their identification and analysis as well as future needs will be also discussed.
The presences of micro-pollutants (active pharmaceutical ingredients, APIs) are increasingly seen as a challenge of the sustainable management of water resources worldwide due to ineffective effluent treatment and other measures for their input prevention. Therefore, novel approaches are needed like designing greener pharmaceuticals, i.e. better biodegradability in the environment. This study addresses a tiered approach of implementing green and sustainable chemistry principles for theoretically designing better biodegradable and pharmacologically improved pharmaceuticals. Photodegradation process coupled with LC–MSn analysis and in silico tools such as quantitative structure–activity relationships (QSAR) analysis and molecular docking proved to be a very significant approach for the preliminary stages of designing chemical structures that would fit into the “benign by design” concept in the direction of green and sustainable pharmacy. Metoprolol (MTL) was used as an example, which itself is not readily biodegradable under conditions found in sewage treatment and the aquatic environment. The study provides the theoretical design of new derivatives of MTL which might have the same or improved pharmacological activity and are more degradable in the environment than MTL. However, the in silico toxicity prediction by QSAR of those photo-TPs indicated few of them might be possibly mutagenic and require further testing. This novel approach of theoretically designing ‘green’ pharmaceuticals can be considered as a step forward towards the green and sustainable pharmacy field. However, more knowledge and further experience have to be collected on the full scope, opportunities and limitations of this approach.
Recent studies have confirmed that the aquatic ecosystem is being polluted with an unknown cocktail of pharmaceuticals, their metabolites and/or their transformation products (TPs). Although individual chemicals are typically present at low concentrations, they can interact with each other resulting in additive or potentially even synergistic mixture effects. Therefore it is necessary to assess the environmental risk caused by these chemicals. Data on exposure is required for quantitative risk assessment of TPs and/or metabolites. Such data are mostly missing because of the non-availability of TPs and very often metabolites for experimental testing. This study demonstrates the application of different in silico tools for qualitative risk assessment using the example of photodegradation TPs (photo-TPs) of diatrizoic acid (DIAT), which itself is not readily biodegradable. Its photolytic transformation was studied and the photodegradation pathway was established. The aerobic biodegradability of photo-TPs under the conditions of an aquatic environment was assessed using standardized OECD tests. The qualitative risk assessment of DIAT and selected photo-TPs was performed by the PBT approach (i.e. Persistence, Bioaccumulation and Toxicity), using experimental biodegradation test assays, applying different QSAR models with several different toxicological endpoints and in silico read-across approaches. The qualitative risk assessment pointed out that the photo-TPs were less persistent compared to DIAT and none of them possessed any bioaccumulation threat. However, a few photo-TPs were predicted to be active for mutagenicity and genotoxicity, which indicate the need for further testing to confirm these predictions. The present study demonstrates that in silico qualitative risk assessment analysis can increase the knowledge space about the environmental fate of TPs.
The fate of thalidomide (TD) was investigated after irradiation with a medium-pressure Hg-lamp. The primary elimination of TD was monitored and structures of phototransformation products (PTPs) were assessed by LC–UV–FL–MS/MS. Environmentally relevant properties of TD and its PTPs as well as hydrolysis products (HTPs) were predicted using in silico QSAR models. Mutagenicity of TD and its PTPs was investigated in the Ames microplate format (MPF) aqua assay (Xenometrix, AG). Furthermore, a modified luminescent bacteria test (kinetic luminescent bacteria test (kinetic LBT)), using the luminescent bacteria species Vibrio fischeri, was applied for the initial screening of environmental toxicity. Additionally, toxicity of phthalimide, one of the identified PTPs, was investigated separately in the kinetic LBT.
Pesticide contamination of groundwater is of paramount importance because it is the most sensitive and the largest body of freshwater in the European Union. In this paper, an isotopic dilution method based on on-line solid phase extraction-liquid chromatography (electrospray)-tandem mass spectrometry (SPE-LC(ESI)-MS/MS) was used for the analysis of 22 pesticides in groundwater. Results were evaluated from monitoring 112 wells and piezometers coming from 29 different aquifers located in 18 ground water bodies (GWBs), from Catalonia, Spain, for 4years as part of the surveillance and operational monitoring programs conducted by the Catalan Water Agency. The analytical method developed allows the determination of the target pesticides (6 triazines, 4 phenylureas, 4 organophosphorous, 1 anilide, 2 chloroacetanilides, 1 thiocarbamate, and 4 acid herbicides) in groundwater with good sensitivity (limits of detection <5ng/L), accuracy (relative recoveries between 85 and 116%, except for molinate), and repeatability (RSD<23%), and in a fully automated way. The most ubiquitous compounds were simazine, atrazine, desethylatrazine and diuron. Direct relation between frequency of detection of each target compound and Groundwater Ubiquity Score index (GUS index) is observed. Desethylatrazine and deisopropylatrazine, metabolites of atrazine and simazine, respectively, presented the highest mean concentrations. Compounds detected in less than 5% of the samples were cyanazine, molinate, fenitrothion and mecoprop. According to the Directive 2006/118/EC, 13 pesticides have individual values above the requested limits (desethylatrazine, atrazine and terbuthylazine lead the list) and 14 samples have total pesticide levels above 500ng/L. The GWB with the highest levels of total pesticides is located in Lleida (NE-Spain), with 9 samples showing total pesticide levels above 500ng/L. Several factors such as regulation of the use of pesticides, type of activities in the area, and irrigation were discussed in relation to the observed levels of pesticides.
Although it is known for many years, that transformation products (TPs) of pesticides are often more persistent, mobile, and sometimes more toxic than the parent compound, former catchment scale studies of substance release and flushing effects focused only on the parent compound. In this study, four river points were sampled in the Hula Valley, Israel, and samples were analyzed in the lab for chlorpyrifos (CP) and endosulfan residues (including transformation products; TPs). Sampling results of the first rainfall in autumn 2009 identified a strong release of most substances to the rivers. First flush effects of these substances were assessed regarding the risk for drinking water supply and ecology, like fresh water invertebrates and fish. Although, these substances were found in Jordan River water during the first significant rainfall the observed levels are below international drinking water guideline values with no adverse effects on human health in the region. However, the observed CP and chlorpyrifos oxon (CPO) levels are above the acute toxicity for fresh water invertebrates and fish. The study shows that the Hula Valley was an important source of pesticides and TPs at the Upper Jordan River basin and that substance flushing is extremely important for pesticides-monitoring campaigns.
This study characterizes the transfer of S-metolachlor (SMOC) and its metabolites, metolachlor ethane sulfonic acid (MESA) and metolachlor oxanilic acid (MOXA) to the alluvial aquifer. Sorption and mineralization of SMOC and its two ionic metabolites were characterized for cultivated soils and solids from the vadose (unsaturated) zone in the Ain Plain (France). Under sterile soil conditions, the absence of mineralization confirms the importance of biotic processes in SMOC degradation. There is some adsorption and mineralization of the parent molecule and its metabolites in the unsaturated zone, though less than in soils. For soils, the MESA adsorption constant is statistically higher than that of MOXA and the sorption constants of the two metabolites are significantly lower than that of SMOC. After 246days, for soils, maximums of 26% of the SMOC, 30% of the MESA and 38% of the MOXA were mineralized. This partly explains the presence of these metabolites in the groundwater at concentrations generally higher than those of the parent molecule for MESA, although there is no statistical difference in the mineralization of the 3 molecules. The laboratory results make it possible to explain the field observations made during 27months of groundwater quality monitoring (monthly sampling frequency). The evolution of both metabolite concentrations in the groundwater is directly related to recharge dynamics; there is a positive correlation between concentrations and the groundwater level. The observed lag of several months between the signals of the parent molecule and those of the metabolites is probably due to greater sorption of the parent molecule than of its metabolites and/or to degradation kinetics.
Thalidomide (TD), besides being notorious for its teratogenicity, was shown to have immunomodulating and anti-inflammatory activities. This is why recently TD became a promising drug for the treatment of different cancers and inflammatory diseases. Yet nothing is known about the environmental fate of TD, which therefore was assessed experimentally and by in silico prediction programs (quantitative structure activity relationship (QSAR) models) within this study. Photolytic degradation was tested with two different light sources (medium-pressure mercury lamp; xenon lamp) and aerobic biodegradability was investigated with two OECD tests (Closed Bottle test (CBT), Manometric Respirometry test (MRT)). An additional CBT was performed for TD samples after 16min of UV-photolysis. The primary elimination of TD was monitored and the structures of its photo-, abiotic and biodegradation products were elucidated by HPLC-UV-Fluorescence-MS(n). Furthermore, elimination of dissolved organic carbon was monitored in the photolysis experiment. LC-MS revealed that new photolytic transformation products (TPs) were identified, among them two isomers of TD with the same molecular mass. These TPs were different to the products formed by biodegradation. The experimental findings were compared with the results obtained from the in silico prediction programs where e.g. a good correlation for TD biodegradation in the CBT was confirmed. Moreover, some of the identified TPs were also structurally predicted by the MetaPC software. These results demonstrate that TD and its TPs are not readily biodegradable and not fully mineralized by photochemical treatment. They may therefore pose a risk to the aquatic environment due to the pharmacological activity of TD and unknown properties of its TPs. The applied techniques within this study emphasize the importance of QSAR models as a tool for estimating environmental risk assessments.
Aqueous solutions of metolachlor and metolachlor-d(6) were photolyzed with UV-visible radiations. The structures of 15 by-products of metolachlor were determined through gas chromatography-mass spectrometry analyses using electron and chemical ionization combined with multistage mass spectrometry. The photolysis by-products of metolachlor resulted mainly from dehalogenation and hydroxylation, in some cases accompanied by cyclization. In silico tests for toxicity prediction showed that the toxicity of some photolysis products is expected to be greater than that of metolachlor. Persistence studies showed that the by-product relative abundances vary in large amounts with the irradiation time. The post-photolysis evolution of the solution was also studied, in order to determine the persistence of the main by-products. It allowed to establish that most of the by-products can be found more than 12 h after the end of the photolysis, which is of a great concern as treated water is generally available for consumption only a few hours after treatment in most of industrial processes. Copyright © 2012 John Wiley & Sons, Ltd.
Sulfonamides are one of the most frequently used antibiotics worldwide. Therefore, mitigation processes such as abiotic or biotic degradation are of interest. Photodegradation and biodegradation are the potentially significant removal mechanisms for pharmaceuticals in aquatic environments. The photolysis of sulfamethoxypyridazine (SMP) using a medium pressure Hg-lamp was evaluated in three different media: Millipore water pH 6.1 (MW), effluent from sewage treatment plant pH 7.6 (STP), and buffered demineralized water pH 7.4 (BDW). Identification of transformation products (TPs) was performed by LC-UV-MS/MS. The biodegradation of SMP using two tests from the OECD series was studied: Closed Bottle test (OECD 301 D), and Manometric Respirometry test (OECD 301 F). In biodegradation tests, it was found that SMP was not readily biodegradable so it may pose a risk to the environment. The results showed that SMP was removed completely within 128min of irradiation in the three media, and the degradation rate was different for each investigated type of water. However, dissolved organic carbon (DOC) was not removed in BDW and only little DOC removal was observed in MW and STP, thus indicating the formation of TPs. Analysis by LC-UV-MS/MS revealed new TPs formed. The hydroxylation of SMP represents the main photodegradation pathway.
Photodegradation of metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] at 253.7 nm was carried out in water containing soil minerals (kaolinite, montmorillonite, and goethite) and fulvic acid under two different pH conditions. The rate of photolysis was dependent on the nature of the soil constituents and the initial pH of the medium. Based on the regression analysis, it was shown that the photodegradation followed the first-order kinetics with respect to the metolachlor concentration, and the half-life of the herbicide under UV irradiation was longer in the absence of soil constituents. Hydroxylation, dehalogenation, oxoquinoline formation, and demethylation were the main processes observed during the photolysis of metolachlor. More degradation products were formed in the presence of kaolinite, montmorillonite, and goethite than with fulvic acid and water alone. The major degradation product formed under UV irradiation in all the treatments was identified as 4-(2-ethyl-6-methylphenyl)-5-methyl-3-morpholine. Keywords: Photodegradation; metolachlor; soil minerals; fulvic acid; degradation products
We studied the dechlorination of metolachlor by four microorganisms, Streptomyces sp., Phanerochaete chrysosporium, Rhizoctonia praticola, and Syncephalastrum racemosum, in a growth medium containing 0.35 mM metolachlor. A significant amount of the herbicide was dechlorinated by all cultures, resulting in the formation of seven dechlorinated products as determined by high-performance liquid chromatography and mass spectrometric analyses. Transformation mechanisms included dehalogenation with subsequent hydroxylation of the chloroacetyl group; further reactions led to ring formation between the acetyl group and the benzylic ethyl side chain. Dehalogenation in conjunction with demethylation at the N-alkyl substituent and hydroxylation at the aralkyl side chain were also observed. Streptomyces was the most active culture in dechlorinating metolachlor; 41 % of the added herbicide was recovered as dechlorinated products after a 16-day incubation period. Dechlorinated products from P. chrysosporium, R. praticola, and S. racemosum amounted to 28.4, 26.8, and 13.5 %, respectively, of the originally added metolachlor. Upon incubation of the dechlorination product G or I with Streptomyces, both compounds were further transformed, indicating metabolism of the primary products.
Metolachlor is an important selective herbicide used for the control of several annual grassy weeds and certain broad-leafed weeds in corn, soybean, peanut, and other crops. It is the most heavily used agricultural pesticide in Ontario. There is, however, very little information in the open literature on the aquatic fate and persistence of metolachlor, a fact that hinders the assessment of its ultimate impact on the aquatic ecosystem. This study showed that metolachlor was very stable in natural water systems. No apparent biodegradation or biotransformation of metolachlor was observed in three test lake waters after an incubation period of 170 days. With a polynuclear aromatic hydrocarbon (PAH) degrading bacterial culture as the test organism, metolachlor was estimated to have an environmental persistence much greater than medium molecular weight PAHs. Thus the extensive herbicidal use of metolachlor may have a long-lasting impact on Canadian aquatic ecosystems. The white rot fungus Phanerochaete chrysosporium was able to biotransform metolachlor. Based on the three identified metabolites, a tentative metabolic pathway of metolachlor biotransformation by P. chrysosporium was proposed, involving demethylation, hydroxylation, and hydrolytic dechlorination. © by John Wiley & Sons, Inc.
Most herbicides applied to crops are adsorbed by plants or transformed (degraded) in the soil, but small fractions are lost from fields and either move to streams in overland runoff, near surface flow, or subsurface drains, or they infiltrate slowly to ground water. Herbicide transformation products (TPs) can be more or less mobile and more or less toxic in the environment than their source herbicides. To obtain information on the concentrations of selected herbicides and TPs in surface waters of the Midwestern United States, 151 water samples were collected from 71 streams and five reservoir outflows in 1998. These samples were analyzed for 13 herbicides and 10 herbicide TPs. Herbicide TPs were found to occur as frequently or more frequently than source herbicides and at concentrations that were often larger than their source herbicides. Most samples contained a mixture of more than 10 different herbicides or TPs. The ratios of TPs to herbicide concentrations can be used to determine the source of herbicides in streams. Results of a two-component mixing model suggest that on average 90 percent or more of the herbicide mass in Midwestern streams during early summer runoff events originates from the runoff and 10 percent or less comes from increased ground water discharge.
In some countries effluents from hospitals and households are directly emitted into open ditches without any further treatment and with very little dilution. Under such circumstances photo- and biodegradation in the environment can occur. However, these processes do not necessarily end up with the complete mineralization of a chemical. Therefore, the biodegradability of photoproduct(s) by environmental bacteria is of interest. Cardiovascular diseases are the number one cause of death globally. Captopril (CP) is used in this study as it is widely used in Egypt and stated as one of the essential drugs in Egypt for hypertension. Three tests from the OECD series were used for biodegradation testing: Closed Bottle test (CBT; OECD 301 D), Manometric Respirometry test (MRT; OECD 301 F) and the modified Zahn-Wellens test (ZWT; OECD 302 B). Photodegradation (150 W medium-pressure Hg-lamp) of CP was studied. Also CBT was performed for captopril disulfide (CPDS) and samples received after 64 min and 512 min of photolysis. The primary elimination of CP and CPDS was monitored by LC-UV at 210 nm and structures of photoproducts were assessed by LC-UV-MS/MS (ion trap). Analysis of photodegradation samples by LC-MS/MS revealed CP sulfonic acid as the major photodegradation product of CP. No biodegradation was observed for CP, CPDS and of the mixture resulting from photo-treatment after 64 min in CBT. Partial biodegradation in the CBT and MRT was observed in samples taken after 512 min photolysis and for CP itself in MRT. Complete biodegradation and mineralization of CP occurred in the ZWT.
The herbicide metolachlor has been widely used for over 20 years for selective weed control in more than 70 crops worldwide. Its favourable soil behaviour and low risk for developing weed resistance means that metolachlor integrates well into sustainable weed-management practices, such as conservation tillage. Metolachlor consists of four stereoisomers, with herbicidal activity coming mainly from the S-isomer pair. A new catalyst system developed allows the commercial production of enantiomerically-enriched S-metolachlor (ISO draft common name). In field trials carried out 1995–1996 S-metolachlor demonstrated equivalent efficacy on major grass weeds and tolerance to different maize cultivars at 65% the use rate of metolachlor. In laboratory studies in different soils degradation half-lives were similar for metolachlor and S-metolachlor. The mean half life of S-metolachlor was 23 days in dissipation studies at different European field sites. At the lower use rates and with highly concentrated formulations containing up to 96% (w/v) active ingredient, the use of S-metolachlor will result in a substantial reduction of risk to applicators, consumers and the environment and the herbicide will continue to play an important role in sustainable weed-management.
The search for environmental transformation products of organic pollutants (like drugs) is a difficult task and usually only few compounds are detected. This might be due to effective degradation but could also be a result of analytical deficits dealing with complex matrices. Especially transformation products of very low concentrations in sludge were difficult to identify so far. Additionally, the use of standard separation techniques might lead to the loss of isomeric compounds, which possess identical spectroscopic and spectrometric properties. To date no complete study investigating the environmental fate of any tricyclic antipsychotic drug has been reported. Therefore, this study investigated the popular neuroleptic drug chlorpromazine and its potential transformation by all main environmental pathways: aerobic and anaerobic biodegradation as well as abiotic photolytic degradation by sunlight. Analysis of test samples by high performance liquid chromatography coupled to multiple stage mass-spectrometry (HPLC-MS(n)) allowed the detection of numerous compounds. Further, the use of a special software allowed distinguishing between transformation products of small intensities and background "noise" caused by sludge or matrix. Three aerobic tests of different bacterial density (the Closed Bottle test, OECD 301D; the Manometric Respiratory test, OECD 301F; the modified Zahn-Wellens test, 302B; one anaerobic test (a modified anaerobic degradation test according to ISO 11734) as well as a photodegradation test were performed in the present study. According to the individual test guidelines, chlorpromazine had to be classified as not biodegradable in all of the biodegradation tests. However, a special chromatographic column and gradient along with mass spectrometric fragmentation experiments of higher order uncovered the presence of a total of 61 abiotic and biotic transformation products which where formed during the course of the tests. The structures of three aerobic and one anaerobic biotransformation products were elucidated by HPLC-UV-Flourescence-MS(n). Photodegradation showed almost complete elimination of chlorpromazine after 4h of irradiation with a xenon arc lamp. 57 photoproducts were found and for 28 of them LC-MS(n) fragmentation experiments (n=4) were performed. The molecular structures of the three main photolysis products were elucidated. The identified transformation products are expected to be found in the aquatic environment, yet nothing is known about their ecotoxicological properties. As some of the performed tests showed toxic effects of chlorpromazine or its transformation products on bacteria, further risk assessment upon this drug and its fate is strongly recommended.
Cyclodextrins (CDs) possess a variety of chiral centers and are capable of recognizing enantiomeric molecules through the formation of inclusion complexes. Two types of CDs, α-cyclodextrin (α-CD) and β-cyclodextrin (β-CD), were selected to evaluate the effects of the enantioselective ecotoxicity of racemic metolachlor (Rac-metolachlor) and its S-enantiomer (S-metolachlor) on the freshwater algae Scenedesmus obliquus (S. obliquus) by acute toxicity test. The results showed that the aquatic toxicity of S-metolachlor was higher than Rac-metolachlor and that CDs enhanced the toxicity of metolachlor enantioselectively by increasing the aquatic toxicity of Rac-metolachlor rather than that of S-metolachlor to S. obliquus. The equilibrium constant for Rac-metolachlor-CD complexes was higher than that of S-metolachlor-CDs, which was responsible for the greater aquatic toxicity shift effect of Rac-metolachlor. Thermodynamic studies of CD complexes showed that inclusion for all of the complexes was primarily a spontaneous, enthalpy-driven process. These results will help to understand the preliminary mechanism of shifting aquatic toxicity of metolachlor by CDs and the CDs mediated environmental processes of metolachlor, to correctly apply CDs to chiral pesticides formulation and environmental remediation of chiral contaminants.
Understanding herbicide sorption within soil profiles is the first step to predicting their behavior and leaching potential. Laboratory studies were conducted to determine the influence of surface and subsurface soil properties on acetochlor, atrazine, and S-metolachlor sorption. Soil samples were taken from horizons A, B, and C of two loamy soils of the humid pampas of Argentina under no-till management; horizon A was divided into two layers, A(0) (0-5 cm) and A(1) (5 cm to the full thickness of an A horizon). Sorption isotherms were determined from each sampled horizon using the batch equilibrium method and seven concentrations (0, 0.1, 0.5, 2.0, 5.0, 10.0, and 20.0 mg L(-1)). Sorption affinity of herbicides was approximated by the Freundlich equation. The sorption strength K(f) (mg(1 - 1/n) kg(-1) L(1/n) ) over the soils and horizons studied followed the order S-metolachlor (16.51-29.19) > atrazine (4.85-12.34) ≥ acetochlor (5.17-11.97), which was closely related to the hydrophobicity of herbicides expressed as octanol-water partition coefficient (K(OW) ). The K(f) values of the three herbicides were positively correlated with soil organic carbon, with a significance of p < 0.01. Values of K(f) for the three herbicides decreased with depth in the two soils, indicating greater sorption onto surficial soil horizons and possibly a delayed transport toward subsurface soils and subsequent pollution of groundwater.
The effects of (Rac)-metolachlor and (S)-metolachlor on the avoidance behavior, bodyweight change and in vivo enzyme activity of earthworms (Eisenia foetida) were determined and compared in this study. The effects of (Rac)-metolachlor on the enzyme activities of E. foetida and bodyweight were more significant than those of (S)-metolachlor at the same concentrations. In the short term (2 d, 7 d), (S)-metolachlor had faster effects on cellulase and catalase activities of E. foetida. However, in the relatively long term (14 d, 28 d), (Rac)-metolachlor had higher toxic effects on cellulase and catalase activities. The inter-group difference between (Rac)-metolachlor and (S)-metolachlor on E. foetida enzyme activities was the most significant for catalase, and the least significant for cellulase. The test of avoidance behavior shows that earthworms are more sensitive to the stimulation of (Rac)-metolachlor than to that of (S)-metolachlor. The results will help to develop an understanding of the biologically mediated environmental processes of these two herbicides.
Chiral pesticides comprise a new and important class of environmental pollutants nowadays. With the development of industry, more and more chiral pesticides will be introduced into the market. But their enantioselective ecotoxicology is not clear. Currently used synthetic pyrethroids, organophosphates, acylanilides, phenoxypropanoic acids and imidazolinones often behave enantioselectively in agriculture use and they always pose unpredictable enantioselective ecological risks on non-target organisms or human. It is necessary to explore the enantioselective toxicology and ecological fate of these chiral pesticides in environmental risk assessment. The enantioselective toxicology and the fate of these currently widely used pesticides have been discussed in this review article.
Application and microbial degradation of the fungicide tolylfluanide gives rise to a new decomposition product named N,N-dimethylsulfamide (DMS). In Germany, DMS was found in groundwaters and surface waters with typical concentrations in the range of 100-1000 ng/L and 50-90 ng/L, respectively. Laboratory-scale and field investigations concerning its fate during drinking water treatment showed that DMS cannot be removed via riverbank filtration, activated carbon filtration, flocculation, and oxidation or disinfection procedures based on hydrogen peroxide, potassium permanganate, chlorine dioxide, or UV irradiation. Even nanofiltration does not provide a sufficient removal efficiency. During ozonation about 30-50% of DMS are converted to the carcinogenic N-nitrosodimethylamine (NDMA). The NDMA being formed is biodegradable and can at least partially be removed by subsequent biologically active drinking water treatment steps including sand or activated carbon filtration. Disinfection with hypochlorous acid converts DMS to so far unknown degradation products but not to NDMA or 1,1-dimethylhydrazine (UDMH).
A large number of herbicide transformation products has been detected in surface waters and groundwaters of agricultural areas, often even in higher concentrations and more frequently than their parent compounds. However, their input dynamics and fate in surface waters are still rather poorly understood. This study compares the aquatic fate, concentration levels, and dynamics of the transformation product metolachlor ethanesulfonic acid (metolachlor ESA) and its parent compound metolachlor, an often-used corn herbicide. To this end, laboratory photolysis studies were combined with highly temporally resolved concentration measurements and lake mass balance modeling in the study area of Lake Greifensee (Switzerland). It is found that the two compounds show distinctly different concentration dynamics in the lake tributaries. Concentration-discharge relationships for metolachlor ESA in the main tributary showed a high baseflow concentration and increasing discharge dependence during harvest season, whereas baseflow concentrations of metolachlor were negligible and the discharge dependence was restricted to the period immediately following application. From this it was estimated that 70% of the yearly load of metolachlor ESA to the lake was due to groundwater recharge, whereas, for metolachlor, the bigger part of the load, 50-80%, stemmed from event-driven runoff. Lake mass balance modeling showed that the input dynamics of metolachlor and metolachlor ESA are reflected in their concentration dynamics in the lake's epilimnion and that both compounds show a similar fate in the epilimnion of Lake Greifensee during the summer months with half-lives on the order of 100-200 days, attributable to photolysis and another loss process of similar magnitude, potentially biodegradation. The behavior of metolachlor ESA can likely be generalized to other persistent and highly mobile transformation products. In the future, this distinctly different behavior of mobile pesticide transformation products should find a more appropriate reflection in exposure models used in chemical risk assessment and in pesticide risk management.
We screened several strains of microorganisms and microbial populations for their ability to mineralize or transform the herbicide metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)-acetami de] because such cultures would potentially be useful in the cleanup of contaminated sites. Although we used various inocula and enrichment culture techniques, we were not able to isolate microorganisms that could mineralize metolachlor. However, strains of Bacillus circulans, Bacillus megaterium, Fusarium sp., Mucor racemosus, and an actinomycete were found to transform metolachlor. Several metabolites could be determined with high-performance liquid chromatography. The tolerance of the strains to high concentrations of metolachlor was also evaluated for the usefulness of the strains for decontamination. Tolerance of the actinomycete to metolachlor concentrations over 200 ppm (200 micrograms/ml) was low and could not be increased by doubling the sucrose concentration in the growth medium or by using a large biomass as inoculum. However, a Fusarium sp. could grow and transform metolachlor up to a concentration of 300 ppm.
Alachlor, metolachlor, and propachlor are detoxified in biological systems by the formation of glutathione-acetanilide conjugates. This conjugation is mediated by glutathione-S-transferase, which is present in microorganisms, plants, and mammals. Other organic sulfides and inorganic sulfide also react through a nucleophilic attack on the 2-chloro group of acetanilide herbicides, but the products are only partially characterized. Sorption in soils and sediments is an important factor controlling the migration and bioavailability of these herbicides, while microbial degradation is the most important factor in determining their overall fate in the environment. The biodegradation of alachlor and metolachlor is proposed to be only partial and primarily cometabolic, and the ring cleavage seems to be slow or insignificant. Propachlor biodegradation has been reported to proceed to substantial (> 50%) mineralization of the ring structure. Reductive dechlorination may be one of the initial breakdown mechanisms under anaerobic conditions. Aerobic and anaerobic transformation products vary in their polarity and therefore in soil binding coefficient. A catabolic pathway for chloroacetanilide herbicides has not been presented in the literature because of the lack of mineralization data under defined cultural conditions.
The photolysis of metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide] in a sunlight simulator under actinic radiation was investigated. The focus of the study was to determine the extent of monochloroacetic acid (MCA) production. MCA was concentrated and derivatized from photolysate as the n-propyl ester using propanol and sulfuric acid and then identified as the ester using GC/MS and GC/ECD. On the basis of regression analysis, it was shown that the direct photodegradation of approximately 10 microM metolachlor followed pseudo-first-order kinetics with respect to the metolachlor concentration, and the half-life of the herbicide ( approximately 74 h) was independent of the pH of the medium. Photolysis in synthetic field water (SFW) resulted in a significant reduction of photolysis time (t(1/2) approximately 9 h). Direct photolysis experiments indicate a 5.19 +/- 0.81% (n=3) conversion of metolachlor to MCA, while photolysis in synthetic field water and in a Don River water sample resulted in 29.8 +/- 4.6% (n = 3) and 12.6 +/- 4.1% (n = 3) conversion, respectively; MCA was shown to be hydrolytically stable over the time course of the photoreaction. The photodegradation of alachlor, butachlor and a model chloroacetanilide, 2-chloro-N-methylacetanilide, in SFW were also investigated.
On-line solid-phase extraction liquid chromatography in combination with mass spectrometry (MS), i.e. MS/MS and orthogonal-acceleration time-of-flight MS, was used for the characterization of photodegradation products of alachlor in river water. Various MS/MS scan functions were used, in particular the precursor-ion and the daughter-ion modes, to screen for degradation products with structures closely related to that of alachlor and to obtain information on characteristic fragments of the degradation products. Elemental compositions of compounds found and some of their fragments were calculated from the accurate mass information obtained with orthogonal-acceleration time-of-flight MS. Some ten degradation products could be characterized by combining various types of mass spectral information. Since quite a number of isomers were identified, structures of the degradation products were proposed by considering the most likely fragmentation patterns in MS/MS experiments. Degradation products of alachlor found in the current study were compared with those reported in the literature.
Modern approaches to drug discovery have dramatically increased the speed and quantity of compounds that are made and tested for potential potency. The task of collecting, organizing, and assimilating this information is a major bottleneck in the discovery of new drugs. We have developed LeadScope a novel, interactive computer program for visualizing, browsing, and interpreting chemical and biological screening data that can assist pharmaceutical scientists in finding promising drug candidates. The software organizes the chemical data by structural features familiar to medicinal chemists. Graphs are used to summarize the data, and structural classes are highlighted that are statistically correlated with biological activity.
Our goal was to create a photodegradation model based on the META expert system [G. Klopman, M. Dimayuga, J. Talafous, J. Chem. Inf. Comput. Sci. 34 (1994a) 1320-1325]. This requires the development of a dictionary of photodegradation pathways. Equipped with such a dictionary, we found that META successfully predicts degradation pathways of organic compounds under UV light. Our model was tested on a wide range of industrial compounds for which literature data exists. The results were excellent as the hit/miss ratio was better than 92%. This work complements our previous elaboration of equivalent mammal metabolism, aerobic and anaerobic biodegradation models.
To elucidate the photochemical behavior of pesticide metolachlor, degradation was carried out in aqueous media of different compositions such as sea, river, lake, and distilled water under natural and simulated solar irradiation. In addition, the effect of important constituents of natural water such as dissolved organic matter (DOM, isolated from Pamvotis Lake) and nitrate ions was also examined. It was found that photodegradation proceeds via a pseudo-first-order reaction in all cases. The presence of DOM inhibits the photolysis reaction with half-lives ranging from 87 to 693 h whereas the degradation rate was accelerated up to 11 times in the presence of NO(3)(-). In addition, the toxicity of the degradation products formed (generally through hydroxylation, dealkylation, and cyclization reactions) was also performed using the marine luminescent bacterium Vibrio fisheri. Our results indicated a toxicity increase of the irradiated solution showing that photoproducts of higher acute toxic effects were formed.
Although laboratory studies have revealed that many different neutral degradates of chloroacetamide herbicides can form during thermochemical, biological, and photochemical transformations, relatively few have been sought in the environment, despite their likely generation in appreciable amounts, relative persistence, and known or potential toxicity. The present paper describes a GC/ MS method for the analysis of 20 neutral chloroacetamide degradates, along with the four parent compounds, three triazine herbicides, and two neutral triazine degradates. Using large volume injections and 300:1 concentration via solid phase extraction, detection limits for most neutral chloroacetamide degradates were in the hundreds of pg/L range (low ng/L range for degradates possessing a hydroxy group). In a depth profile taken in midsummer from the upper Chesapeake Bay, 19 of the 20 neutral chloroacetamide degradates of interest were detected, along with three ionic oxanilic acid derivatives. Of those degradates encountered, eight do not appear to have been previously reported in natural or affected environmental samples. Concentrations of most neutral chloroacetamide degradates exceeded those of the parent compounds, while the total concentration of the neutral chloroacetamide degradates was 20-30 times that of the parents. These micropollutants therefore merit more detailed attention as contaminants of potential environmental concern.
The resolved isomer of metolachlor, S-metolachlor, was registered in 1997. New formulations based primarily on the S-metolachlor isomer are more active on a gram for gram metolachlor basis than formulations based on a racemic mixture of metolachlor containing a 50:50 ratio of the R and S isomers. The labelled use rates of S-metolachlor-based products were reduced by 35% to give equivalent weed control to metolachlor. However, several companies have recently registered new metolachlor formulations with the same recommended use rates for weed control as S-metolachlor. This research was done to compare the soil behaviour and the biological activity of metolachlor and S-metolachlor in different soils under greenhouse and field conditions. Although K(d) ranged from 1.6 to 6.9 across the five soils, there were no differences in the binding of metolachlor and S-metolachlor to soil or in the rate of soil solution dissipation in a given soil. However, both greenhouse and field studies showed that S-metolachlor was 1.4-3-fold more active than metolachlor against Echinochloa crus-galli (L.) Beauv. in five different soils and that S-metolachlor was more active than metolachlor in three Colorado field locations. When the rates of metolachlor and S-metolachlor were adjusted for S isomer concentrations in the formulations, there were no differences between the formulations in field, greenhouse or bioassay studies. Thus herbicidal activity is due to the S isomers, with the R isomers being largely inactive.
Metolachlor is one of the most widely used herbicides in the world for controlling weeds. It has been detected in both ground and surface waters in the United States, and there are rising concerns in regard to its health risks and in developing effective treatment processes for its removal from water. Degradation of metolachlor via ultraviolet (UV) photolysis and an UV/hydrogen peroxide advanced oxidation process (AOP) was studied. The quantum yield of metolachlor at 254 nm was found to be 0.302 +/- 0.001 mol E-1 through direct UV photolysis in the range of pH 6-8. The second-order rate constant of the reaction between metolachlor and hydroxyl radical was determined to be 9.07 (+/-0.21) x 10(9) M-1 s-1 by using a competition kinetics model that utilized nitrobenzene as a reference compound. In addition, these parameters were successfully applied in modeling the kinetics of elimination of metolachlor using an UV/H2O2 process in both laboratory and natural waters. The formation of several photolysis byproducts was identified using gas chromatography/mass spectrometry, and a scheme for the metolachlor photodegradation pathway is proposed.
Pesticides having a wide variety of structures have been and are being developed to exhibit an intended efficacy to pests, fungal diseases, and weeds, and are usually applied as formulations to these targets in the field. Many types of formulations have been developed by considering the physicochemical properties of the pesticide, not only to maximize their efficacy but also to prevent unfavorable environmental contamination from pesticide and its degradation products. A lower water solubility of the pesticide usually leads to utilization of a water-miscible organic solvent and formulation additives (adjuvants) including surface-active agents (surfactants) to solubilize, suspend, or disperse the active ingredient (a.i.) of pesticide in its aqueous solution being applied in agricultural practices. Among adjuvants, surfactants are some of the most important components and can improve the biological activity by modifying spray droplet size, retention, and spreading on leaf surfaces or by enhancing uptake and translocation of the a.i. to crop (Knowles 2001). The various kinds of surfactants with a wide variety of molecular weight and ionic character as well as natural and petroleum oils are used as wetting, spreading, sticking, and penetration agents and humectants (Hazen 2000; Krogh et al. 2003).
United States Environmental Protection Agency. Chloroacetamide herbicides and their transformation products in drinking water
- U S Epa
U.S. EPA. United States Environmental Protection Agency. Chloroacetamide herbicides
and their transformation products in drinking water. http://www.waterrf.org/
PublicReportLibrary/91123.pdf, 2006.
EC) No 1107/2009 of the European Parliament and of the Council of 21 October 2009 concerning the placing of plant protection products on the market and repealing Council Directives 79
Regulation (EC) No 1107/2009 of the European Parliament and of the Council of 21 October 2009 concerning the placing of plant protection products on the market and
repealing Council Directives 79/117/EEC and 91/414/EEC; 2009.
- L Gutowski
L. Gutowski et al. / Science of the Total Environment 506–507 (2015) 369–379
United States Environmental Protection Agency. EPA/OPPT/exposure assessment tools and models/estimation program interface (EPI) suite version 3
- U S Epa
U.S. EPA. United States Environmental Protection Agency. EPA/OPPT/exposure assessment
tools and models/estimation program interface (EPI) suite version 3.12 (August 17,
2004). http://www.epa.gov/oppt/exposure/pubs/episuite.htm, 2004. [accessed
December 10, 2013].
Water quality -determination of dissolved oxygen. German standard methods for the examination of water, wastewater and sludge
- Iso
ISO. Water quality -determination of dissolved oxygen. German standard methods for
the examination of water, wastewater and sludge. Weinheim: WILEY-VCH Verlag
GmbH & Co. KGaA; 1990 [Beuth Verlag GmbH, Berlin].
Selection of microorganisms degrading S-metolachlor herbicide
- P F Martins
- C O Martinez
- G De Carvalho
- Pib Carneiro
- R A Azevedo
- Sav Pileegi
Martins PF, Martinez CO, de Carvalho G, Carneiro PIB, Azevedo RA, Pileegi SAV, et al.
Selection of microorganisms degrading S-metolachlor herbicide. Braz Arch Biol
Technol 2007;50:153-9.