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The ECHA guidance on persistence (P) assessment has been updated with respect to non-extractable residues (NER). Unless further characterized, total NER shall be considered as non-degraded parent compound. We investigated how different NER fractions affect degradation half-lives (DegT50) of chemicals and the P assessment. Total NER consist of the fractions sorbed/sequestered (NER I), covalently bound (NER II), and bioNER (incorporated into the biomass, NER III). NER I pose a risk due to potential release, NER II have much lower release potential, and bioNER do not have any. NER I and NER II are considered as xenoNER. Data from 46 degradation tests with 24 substances were analyzed to find DegT50 for four scenarios: (i) extractable parent compound, (ii) parent plus total NER, (iii) parent plus xenoNER, and (iv) parent plus NER I. The microbial turnover to biomass (MTB) model was applied to calculate bioNER, and then xenoNER were calculated as total NER minus bioNER. The half-lives were determined by the fit program CAKE, using single first-order kinetics (SFO) for all fits. We found increasing degradation half-lives for the scenarios: extractable parent only < parent + NER I < parent + xenoNER < parent + total NER. A third of all chemicals show half-lives above the persistence criterion (120 days in OECD 307 and 308, and 40 days in OECD 309) for scenario i, and two thirds with scenario ii and, therefore, would be classified as 'persistent'. For two compounds, the subtraction of bioNER led to a change to 'not persistent'. The inclusion of NER in the P assessment (ECHA 2017, 2023) will thus have significant effects on the DegT50 of compounds and the persistence assessment. Experimental quantification of NER I (scenario iv) significantly reduces half-lives, in comparison to total NER (scenario ii). The results are closer to half-lives for parent only (scenario i) and give the lowest acceptable DegT50 below the vP criteria under the latest guidance. In addition, refining the DegT50 based on modelled bioNER can provide a more realistic option for persistence assessment, without laborious and costly analyses for NER I determination, when considered in the regulatory assessment of persistence. Moreover, bioNER can also be calculated for existing test data. [ABSTRACT FROM AUTHOR]

Abstract The ECHA guidance on persistence (P) assessment has been updated with respect to non-extractable residues (NER). Unless further characterized, total NER shall be considered as non-degraded parent compound. We investigated how different NER fractions affect degradation half-lives (DegT50) of chemicals and the P assessment. Total NER consist of the fractions sorbed/sequestered (NER I), covalently bound (NER II), and bioNER (incorporated into the biomass, NER III). NER I pose a risk due to potential release, NER II have much lower release potential, and bioNER do not have any. NER I and NER II are considered as xenoNER. Data from 46 degradation tests with 24 substances were analyzed to find DegT50 for four scenarios: (i) extractable parent compound, (ii) parent plus total NER, (iii) parent plus xenoNER, and (iv) parent plus NER I. The microbial turnover to biomass (MTB) model was applied to calculate bioNER, and then xenoNER were calculated as total NER minus bioNER. The half-lives were determined by the fit program CAKE, using single first-order kinetics (SFO) for all fits. We found increasing degradation half-lives for the scenarios: extractable parent only

The kinetics of diazinon degradation in soils as affected by the presence of potentially toxic elements was studied. Metal (Zn2+, Cd2+, V3+ and Mn2+) treated soils as well as the control soils were spiked with diazinon at two concentrations of 10, and 50 mg kg-1. The residual diazinon concentrations were measured by corona discharge-ion mobility spectrometry at 0, 1, 10, 30, and 60 d. Degradation time (DT50) was calculated using three kinetic models. At 10 and 50 mg kg-1 of diazinon, no residual concentration could be detected at the day 30 and 60, respectively. In the Shervedan soil, the DT50 values for 10 and 50 mg kg-1 spiked diazinon concentration ranged from 0.51 to 2.3 d and 2.87 to 5.31 d, respectively. The greatest and the lowest DT50 values were consistently obtained in the control and V-treated soil. In the Lavark and Chamaseman soil, the pattern was similar to that of the Shervedan soil, except that Zn was more stimulatory than V in the Lavark soil. In general, metal-treated soils revealed lower diazinon concentrations. For the first time, it is reported that V can enhance the rate of diazinon degradation in soils. Overall, it is concluded that V and Zn are the most stimulatory potentially toxic elements for enhancing diazinon degradation in the soils. Therefore diazinon degradation time in the metal polluted soils is generally shorter. [ABSTRACT FROM AUTHOR]

In this work, a simple sensitive validated liquid chromatography mass spectroscopy (LC-MS/MS) analytical method was developed for the determination of Spirodiclofen residues in different aquatic toxic media. The toxic media were those that provide nutrients and help with the growth of different aquatic organisms for their survival and multiplication. The different media were the M4 medium for Daphnia magna and The Organization for Economic Cooperation and Development (OECD TG 201) medium for alga. Fe2O3-Ag2O/TiO2 nanocomposites were prepared by using a precipitation method, which was used as a photo-catalyst for the removal of Spirodiclofen pesticide from aquatic media. The experiment was performed under direct sunlight at a single fortification level (1.0 µg/mL) in M4 and OECD TG 201 media. The optimum catalyst concentration for the complete degradation was found to be 10 mg/L under sunlight. Spirodiclofen residues in water were determined by LC-MS/MS, and the rate constant DT50 (half-life) values were calculated from the obtained data. The results showed that with Fe2O3-Ag2O/TiO2 nanocatalyst, the DT50 (half-life) value was found to be approximately 8 h. These results revealed that iron-oxide- and silver-oxide-incorporated TiO2 nanocomposites were excellent photocatalysts when compared with TiO2, Fe2O3-TiO2, and Ag2O-TiO2 for the decontamination of pesticide residues in aquatic media samples. [ABSTRACT FROM AUTHOR]

The precipitation process was applied to synthesize chitosan-coated zinc oxide nanoparticles (chitosan-ZnO NPs). Then, various characterization tools were used such as XDR, SEM, TEM, FTIR, and EDX. The use of these 50 nm chitosan-ZnO NPs in soil decontamination of thifluzamide and difenoconazole pesticide residues is being investigated. In two distinct soils, the effect of catalytic decontamination on pesticide residues was examined (sandy loam and sandy clay soils). The studies required two sets of pesticide concentrations. One set of samples was added to the chitosan-ZnO NPs catalyst, and the other set was studied without the addition of a catalyst. Photocatalytic studies were conducted under the sunlight in July. The soil samples were hand-spread in a glass dish to a height of 5 mm and sprayed with an aqueous solution of pesticide. From 8 a.m. to 5 p.m., these samples were exposed to sunlight in October 2021. We found that the best concentration of catalyst was 0.05%. The acquired samples were quantified using validated Ultra-Fast Liquid Chromatography (UFLC) with Photo Diode Array (PDA) detection. Kinetic parameters such as rate constant k and the degradation rate of pesticides DT50 have been calculated using Pesticide Residue Dissipation Data. The findings showed that the tested fungicides degenerate according to pseudo-first-order kinetics. Based on the findings, we concluded that photocatalytic degradation of pesticides in soils are faster than photolysis. [ABSTRACT FROM AUTHOR]

Temperature is a key factor that influences pesticide degradation. Extrapolating degradation half-lives (DT50) measured at a given temperature to different temperatures remains challenging, especially for tropical conditions with high temperatures. In this study, the use of the standard Arrhenius equation for correcting temperature effects on pesticide degradation in soils was evaluated and its performance was compared with that of alternative Arrhenius-based equations. To do so, a database of 509 DT50 values measured between 5 and 35 °C for 32 pesticides on tropical and temperate soils was compiled for the first time through an extensive literature search. The temperature correction models were fitted to the database using linear mixed regression approaches that included soil type and compound effects. No difference in the temperature dependence of DT50 between tropical and temperate soils was detected, regardless of the model. A comparison of the prediction performances of the models showed that constant activation energy (Ea) cannot be considered valid for the whole range of temperatures. The classical Arrhenius equation with an Ea of 65.4 kJ.mol−1, as recommended by the European Food Safety Authority (EFSA), was shown to be valid for correcting the DT50 only for temperatures ranging from 5 to 20 °C. However, for temperatures greater than 20 °C, which are common in tropical environments, the median Ea was significantly lower at 10.3 kJ.mol−1. These findings suggest the need to adapt the standard temperature correction of the European pesticide risk assessment temperature procedure when it is applied in tropical settings. [ABSTRACT FROM AUTHOR]

Cacopsylla pyri (Linnaeus, 1758) is the most significant and widespread pear pest. It attacks the pear only, causing direct and indirect damages. This study was conducted in order to evaluate the efficacy of insecticide spinetoram in the control of C. pyri. The experiment was set up according to EPPO methods, at the locality Kula (Republic of Serbia) in a pear orchard (Williams variety). Spinetoram (250 g/kg a.i., WG) was foliar applied in the amount of 0.3 kg/ha, during overlapping pest generations, when pear was on BBCH 75 scale. The efficacy was evaluated through the number of larvae aged L1-L3 and L4-L5. Spinetoram has shown satisfying efficacy, especially in the control of L1-L3 larvae (81.6%). In a dissipation study, spinetoram residues in pear fruits were determined using QuEChERS method followed by HPLC-DAD. The method was validated to fulfill SANTE/12682/2019 criteria. Three days after the application, spinetoram residues in pear fruits were below the MRL (0.2 mg/kg). The results have shown that spinetoram dissipation pattern followed the first-order kinetics (R2 = 0.979) with a half-life of 2.17 days, in pear fruits. This study suggests that spinetoram could be safely used in pear, and it could take an important place in insecticide resistance management.

Sulfonylurea herbicides can lead to serious weed resistance due to their long degradation times and large-scale applications. This is especially true for chlorsulfuron, a widely used acetolactate synthase inhibitor used around the world. Its persistence in soil often affects the growth of crop seedlings in the following crop rotation, and leads to serious environmental pollution all over the world. Our research goal is to obtain chlorsulfuron-derived herbicides with high herbicidal activities, fast degradation times, as well as good crop safety. On account of the slow natural degradation of chlorsulfuron in alkaline soil, based on the previously reported results in acidic soil, the degradation behaviours of 5-substituted chlorsulfuron analogues (L101–L107) were investigated in a soil with pH 8.39. The experimental data indicated that 5-substituted chlorsulfuron compounds could accelerate degradation rates in alkaline soil, and thus, highlighted the potential for rational controllable degradation in soil. The degradation rates of these chlorsulfuron derivatives were accelerated by 1.84–77.22-fold, compared to chlorsulfuron, and exhibited excellent crop safety in wheat and corn (through pre-emergence treatment). In combination with bioassay activities, acidic and alkaline soil degradation, and crop safety, it was concluded that compounds L104 and L107, with ethyl or methyl groups, are potential green sulfonylurea herbicides for pre-emergence treatment on wheat and corn. This paper provides a reference for the further design of new sulfonylurea herbicides with high herbicidal activity, fast, controllable degradation rates, and high crop safety. [ABSTRACT FROM AUTHOR]

Chlrosulfuron, a classical sulfonylurea herbicide that exhibits good safety for wheat but causes a certain degree of damage to subsequent corn in a wheat–corn rotation mode, has been suspended field application in China since 2014. Our previous study found that diethylamino-substituted chlorsulfuron derivatives accelerated the degradation rate in soil. In order to obtain sulfonylurea herbicides with good crop safety for both wheat and corn, while maintaining high herbicidal activities, a series of pyrimidine- and triazine-based diethylamino-substituted chlorsulfuron derivatives (W102–W111) were systematically evaluated. The structures of the synthesized compounds were confirmed with 1H NMR, 13C NMR, and HRMS. The preliminary biological assay results indicate that the 4,6-disubstituted pyrimidine and triazine derivatives could maintain high herbicidal activity. It was found that the synthesized compounds could accelerate degradation rates, both in acidic and alkaline soil. Especially, in alkaline soil, the degradation rate of the target compounds accelerated more than 22-fold compared to chlorsulfuron. Moreover, most chlorsulfuron analogs exhibited good crop safety for both wheat and corn at high dosages. This study provided a reference for the further design of new sulfonylurea herbicides with high herbicidal activity, fast degradation rates, and high crop safety. [ABSTRACT FROM AUTHOR]

The precipitation process was applied to synthesize chitosan-coated zinc oxide nanoparticles (chitosan-ZnO NPs). Then, various characterization tools were used such as XDR, SEM, TEM, FTIR, and EDX. The use of these 50 nm chitosan-ZnO NPs in soil decontamination of thifluzamide and difenoconazole pesticide residues is being investigated. In two distinct soils, the effect of catalytic decontamination on pesticide residues was examined (sandy loam and sandy clay soils). The studies required two sets of pesticide concentrations. One set of samples was added to the chitosan-ZnO NPs catalyst, and the other set was studied without the addition of a catalyst. Photocatalytic studies were conducted under the sunlight in July. The soil samples were hand-spread in a glass dish to a height of 5 mm and sprayed with an aqueous solution of pesticide. From 8 a.m. to 5 p.m., these samples were exposed to sunlight in October 2021. We found that the best concentration of catalyst was 0.05%. The acquired samples were quantified using validated Ultra-Fast Liquid Chromatography (UFLC) with Photo Diode Array (PDA) detection. Kinetic parameters such as rate constant k and the degradation rate of pesticides DT50 have been calculated using Pesticide Residue Dissipation Data. The findings showed that the tested fungicides degenerate according to pseudo-first-order kinetics. Based on the findings, we concluded that photocatalytic degradation of pesticides in soils are faster than photolysis.

Cacopsylla pyri (Linnaeus, 1758) is the most significant and widespread pear pest. It attacks the pear only, causing direct and indirect damages. This study was conducted in order to evaluate the efficacy of insecticide spinetoram in the control of C. pyri. The experiment was set up according to EPPO methods, at the locality Kula (Republic of Serbia) in a pear orchard (Williams variety). Spinetoram (250 g/kg a.i., WG) was foliar applied in the amount of 0.3 kg/ha, during overlapping pest generations, when pear was on BBCH 75 scale. The efficacy was evaluated through the number of larvae aged L1--L3 and L4--L5. Spinetoram has shown satisfying efficacy, especially in the control of L1--L3 larvae (81.6%). In a dissipation study, spinetoram residues in pear fruits were determined using QuEChERS method followed by HPLC-DAD. The method was validated to fulfill SANTE/12682/2019 criteria. Three days after the application, spinetoram residues in pear fruits were below the MRL (0.2 mg/kg). The results have shown that spinetoram dissipation pattern followed the first-order kinetics (R2 = 0.979) with a half-life of 2.17 days, in pear fruits. This study suggests that spinetoram could be safely used in pear, and it could take an important place in insecticide resistance management. [ABSTRACT FROM AUTHOR]

A mesocosm experiment was conducted to assess the side effects of the fungicide QuadrisR on soil bacterial functioning. QuadrisR was applied to a loamy sand soil at increasing concentrations (0.0–35.0 mg kg−1 dry soil) calculated according to its active ingredient azoxystrobin (Az). Soil sampling was carried out from the 1st to the 120th day of soil incubation to determine the changes occurred in bacterial catabolism using the technique of community-level physiological profiling (CLPP) via Biolog EcoPlates™. It was found that the field recommended fungicide concentration (2.90 mg kg−1 dry soil) altered mostly the low-available Biolog carbon sources (< 0.50 optical density (OD)), whereas the fungicide higher concentrations (14.65 and 35.00 mg kg−1 dry soil) were effective also on medium (0.50–1.00 OD) and highly (> 1.00 OD) utilizable ones. Pearson correlation analysis revealed that the main environmental factors correlated with the utilization rates of Biolog carbon sources (CSs) were soil nutrients and pH. No linear relationships were found between Az soil residues and the use of CSs. We concluded that QuadrisR affects bacterial catabolic profiles in loamy sand soils through soil acidification and altering soil nutrient pool. The study also revealed that CLPP and EcoPlate™ are useful practical tools for testing the fungicide ecotoxicity. [ABSTRACT FROM AUTHOR]

Fe–Ag co-doped TiO2 nanoparticles (NPs) were prepared as a photocatalyst using a precipitation method for the removal of flumioxazin pesticide residues in water. The analytical method was validated with specificity, linearity, recovery, precision, the limit of quantification, and detection limit. Linearity was determined by different known concentrations of standard solutions. Detection limit was identified as the lowest concentration resulting in a 3-fold response to baseline noise. Photolytic and photocatalytic studies were conducted in borosil glass bottles under sunlight at a single fortification level (1.0 μg/mL) in Milli-Q water with various pH values (pH 4.0, 7.0, and 9.0). The optimum catalyst concentration recommended for complete degradation was found to be 50 mg/L under sunlight. The HPLC-UV method was used to determine flumioxazin residues in water, and the rate constant, DT50, and DT90 values were calculated from the data obtained. The photolytic results do not indicate a significant residue loss due to adsorption. Fe–Ag co-doped TiO2 NPs are an outstanding decontaminating catalyst in various water samples.

Sulfonylurea herbicides are widely used as acetolactate synthase (ALS) inhibitors due to their super-efficient activity. However, some sulfonylurea herbicides show toxicity under crop rotation due to their long degradation time, for example, chlorsulfuron. Our research goal is to obtain chlorsulfuron-derived herbicides with controllable degradation time, good crop safety and high herbicidal activities. Based on our previously reported results in acidic soil, we studied the degradation behaviors of 5-dialkylamino-substituted chlorsulfuron derivatives (NL101–NL108) in alkaline soil (pH 8.39). The experimental data indicate that addition of the 5-dialkylamino groups on the benzene ring of chlorsulfuron greatly accelerated degradation in alkaline soil. These chlorsulfuron derivatives degrade 10.8 to 51.8 times faster than chlorsulfuron and exhibit excellent crop safety on wheat and corn (through pre-emergence treatment). With a comprehensive consideration of structures, bioassay activities, soil degradation and crop safety, it could be concluded that 5-dialkylamino-substituted chlorsulfuron derivatives are potential green sulfonylurea herbicides for pre-emergence treatment on both wheat and corn. The study also provides valuable information for the discovery of new sulfonylurea herbicides for crop rotation.

Antibiotics play a key role in the management of infectious diseases in humans, animals, livestock, and aquacultures all over the world. The release of increasing amount of antibiotics into waters and soils creates a potential threat to all microorganisms in these environments. This review addresses issues related to the fate and degradation of antibiotics in soils and the impact of antibiotics on the structural, genetic and functional diversity of microbial communities. Due to the emergence of bacterial resistance to antibiotics, which is considered a worldwide public health problem, the abundance and diversity of antibiotic resistance genes (ARGs) in soils are also discussed. When antibiotic residues enter the soil, the main processes determining their persistence are sorption to organic particles and degradation/transformation. The wide range of DT50 values for antibiotic residues in soils shows that the processes governing persistence depend on a number of different factors, e.g., physico-chemical properties of the residue, characteristics of the soil, and climatic factors (temperature, rainfall, and humidity). The results presented in this review show that antibiotics affect soil microorganisms by changing their enzyme activity and ability to metabolize different carbon sources, as well as by altering the overall microbial biomass and the relative abundance of different groups (i.e., Gram-negative bacteria, Gram-positive bacteria, and fungi) in microbial communities. Studies using methods based on analyses of nucleic acids prove that antibiotics alter the biodiversity of microbial communities and the presence of many types of ARGs in soil are affected by agricultural and human activities. It is worth emphasizing that studies on ARGs in soil have resulted in the discovery of new genes and enzymes responsible for bacterial resistance to antibiotics. However, many ambiguous results indicate that precise estimation of the impact of antibiotics on the activity and diversity of soil microbial communities is a great challenge.

The persistence of S-metolachlor was monitored under maize plots during two growing seasons in Southern Guinea Savanna soil of Ladoke Akintola University of Technology, Ogbomoso, Teaching and Research Farm and a farm settlement in Ogbomoso in two growing seasons in the using Spectronic 2ID for residue analysis of samples. The treatments applied were 1.6 l/ha, 1.2 l/ha, and 0.8 l/ha and two controls of hand weeding alone and zero weed control and replicated thrice. S-metolachlor residue from the soil decreased faster during the first four weeks after application; followed by a slower rate of disappearance four to eight weeks after application. The disappearance time (DT) values showed that 10% (DT10) of the initial concentration was lost by 9.7, 10.1, and 13.2 days after application for 1.6, 1.2, and 0.8 l/ha rates respectively. At 80.1 days after application, 75% (DT75) of S-metolachlor at the usual recommended rate of 1.6 l/ha had disappeared; at 55.4 days after application, 50% (DT50) of this rate had disappeared. Weed control assessment at this period showed a relatively inadequate control of weeds due to the loss of the applied S-metolachlor. This indicated that adequate weed control cannot be expected by eighth week after application and beyond. S-metolachlor was found to be moderately persistent in this zone. [ABSTRACT FROM AUTHOR]

Antibiotics play a key role in the management of infectious diseases in humans, animals, livestock, and aquacultures all over the world. The release of increasing amount of antibiotics into waters and soils creates a potential threat to all microorganisms in these environments. This review addresses issues related to the fate and degradation of antibiotics in soils and the impact of antibiotics on the structural, genetic and functional diversity of microbial communities. Due to the emergence of bacterial resistance to antibiotics, which is considered a worldwide public health problem, the abundance and diversity of antibiotic resistance genes (ARGs) in soils are also discussed. When antibiotic residues enter the soil, the main processes determining their persistence are sorption to organic particles and degradation/transformation. The wide range of DT50 values for antibiotic residues in soils shows that the processes governing persistence depend on a number of different factors, e.g., physico-chemical properties of the residue, characteristics of the soil, and climatic factors (temperature, rainfall, and humidity). The results presented in this review show that antibiotics affect soil microorganisms by changing their enzyme activity and ability to metabolize different carbon sources, as well as by altering the overall microbial biomass and the relative abundance of different groups (i.e., Gram-negative bacteria, Gram-positive bacteria, and fungi) in microbial communities. Studies using methods based on analyses of nucleic acids prove that antibiotics alter the biodiversity of microbial communities and the presence of many types of ARGs in soil are affected by agricultural and human activities. It is worth emphasizing that studies on ARGs in soil have resulted in the discovery of new genes and enzymes responsible for bacterial resistance to antibiotics. However, many ambiguous results indicate that precise estimation of the impact of antibiotics on the activity and diversity of soil microbial communities is a great challenge. [ABSTRACT FROM AUTHOR]

Herbicides play an important role in the production of crops, but their residues may cause numerous human/environmental problems. Dissipation kinetics of pendimethalin and residues in soil, maize straw and cobs in winter maize under field conditions were studied by gas chromatograph-electron capture detector (GC-ECD). Dissipation followed the first order kinetics and accounted by a biphasic pattern. The half-life for initial phase and later phase was 11.70 and 34.13 days for recommended and 9.19 and 46.81 days for double dose, respectively. Percent recovery from cobs, straw and soil samples varied from 76.2-88.5, 76.6-84.4, and 85.0-89.5%. The limit of quantification was 0.001 µg/g of sample. At harvest pendimethalin residues were below detectable limit in soil, maize cobs and maize plant at both application rates (1 and 2 kg/ha). Pendimethalin is safe for use and does not appear to pose any health hazard to consumers or harm to the environment.

This study evaluates the dissipation of terbuthylazine, metolachlor, and mesotrione at different depths in soils with contrasting texture. The field trial was conducted at the Padua University Experimental Farm, north-east Italy. The persistence of three herbicides was studied in three different soil textures (clay soil, sandy soil, and loamy soil) at two depths (0-5 and 5-15 cm). Soil organic carbon content was highest in the clay (1.10%) followed by loam (0.67%) and sandy soil (0.24%); the pH of soils was sub-alkaline. Terbuthylazine, metolachlor, and mesotrione were applied on maize as a formulated product (Lumax®) at a dose of 3.5 L ha−1. Their dissipation in the treated plots was followed for 2 months after application. The concentrations of herbicides were analyzed by liquid chromatography-mass spectrometry. The dissipation of terbuthylazine, metolachlor, and mesotrione could be described by a pseudo first-order kinetics. Terbuthylazine showed the highest DT50, followed by metolachlor and mesotrione. Considering the tested soil, the highest DT50 value was found in clay soil for terbuthylazine and metolachlor, whereas for mesotrione there was no difference among soils. Significant differences were found between the two soil depths for terbuthylazine and metolachlor, whereas none were found for mesotrione. These results suggest that soil texture and depth have a strong influence on the dissipation of terbuthylazine and metolachlor, whereas no influence was observed on mesotrione because of its chemical and physical properties. [ABSTRACT FROM AUTHOR]

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Biodegradation of Paichongding (IPP), a recently developed cis -nitromethylene neonicotinoid insecticide, was investigated in two different soils under aerobic condition. IPP degradation rate was strongly affected by soil physic-chemical characteristics and the inoculation of IPP-degrading bacteria. Inoculation of IPP-degrading bacteria can increase degradation rate and decrease DT50 (half-life value). The removal ratio of RR-IPP, SS-IPP, SR-IPP and RS-IPP at 60 days after treatment (DAT) reached 30.17%, 28.06%, 51.48% and 45.76% in Yellow clayed soil (S1), 20.04%, 19.78%, 36.22% and 40.59% in Huangshi soil (S2), respectively. DT50 of IPP in S1 and S2 decreased after inoculation of Sphingobacterium sp. M3-1. Furthermore, based on the identified eight metabolites (M1–M8) by LC–MS/MS and their behavior, a biodegradation pathway of IPP in soils was proposed. New metabolites, M4, M6 and M7 were observed and determined in soils. Biodegradation of IPP involved continuous biocatalytic reactions such as nitro reduction and elimination, hydrolysis, C-N cleavage, de-methyl, and ether cleavage reactions. Finally, IPP was bio-transformed into M7 and M8. [ABSTRACT FROM AUTHOR]

BACKGROUND Thiamethoxam is a systemic and contact pesticidal active substance in the neonicotinoid class of insecticides used worldwide to control a range of insects. Recently, concerns have been expressed regarding possible effects of neonicotinoids on bees and other wildlife. The DT50 of thiamethoxam in soil may be crucial to assessing the potential long-term exposure of non-target organisms to thiamethoxam. There are currently no detailed publicly available data for the field soil degradation of thiamethoxam under European conditions. We give field soil DT50 values of thiamethoxam from studies conducted in several European locations, under a range of realistic agronomic conditions. RESULTS Field soil DT50 values normalised to 20 °C ranged between 7.1 and 92.3 days (geomean = 31.2 days; n = 18). CONCLUSION The degradation rate of thiamethoxam was not significantly affected by application type, cropped fields versus bare soil, soil pH, organic matter content or repeated annual applications. Soil photolysis and leaching were negligible; therefore, calculated DT50 values were taken to represent microbial degradation. The field degradation rates of thiamethoxam were faster than those previously reported from laboratory degradation studies. They demonstrate that thiamethoxam will degrade to concentrations that are <10% of the maximum within a year of application, and will not accumulate in soil after repeated applications. © 2015 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

In agricultural areas, pesticides can enter receiving waterbodies by means of agricultural runoff and pollute these systems. Constructed wetlands are capable of removing several pollutants including pesticides. Unfortunately, few studies are from South America, and therefore, information is urgently needed on pesticide mitigation in agricultural runoff by native plants. To this aim, an experimental setup of polypropylene tubs was used, which were planted with two types of native plants ( Nymphaea amazonum and Eleocharis mutata). Mesocosms were exposed to low (10 μg/l) and high (30 μg/l) target concentrations of lambda-cyhalothrin, while for imidacloprid, a low (60 μg/l), high (180 μg/l), and an extra high (1,000 μg/l) dose, were applied using batch experiments of 2 weeks each. Removal efficiencies for lambda-cyhalothrin from the water phase showed 100 % removal at 72 h for both low and high target concentrations for N. amazonum mesocosms, while for E. mutata mesocosms, a 100 % removal was observed at 48 h for mesocosms exposed to low target concentrations and for high target concentrations at 72 h. For imidacloprid, a 100 % removal was observed for E. mutata and 86 % for N. amazonum mesocosms exposed to low target concentrations (60 μg/l) at 216 h. For the highest dose (1,000 μg/l), the removal efficiency was on average 72 % at 216 h for both types of mesocosms. Statistical two-way ANOVA analysis ( α = 0.05) showed that the removal of lambda-cyhalothrin was independent of the dose applied and the plant type, while for imidacloprid, removal was dependent on the dose applied and independent of the plant type. After the experimental period, analyses of the plants and sediment showed that 48.5 % of the applied amount of lambda-cyhalothrin was detected in the sediment and 0.4 % in plant material (shoots and leaves), while the amount in roots was below the limit of detection for N. amazonum mesocosms. For E. mutata mesocosms, 44.6 % of lambda-cyhalothrin was detected in sediment and 0.5 % in roots. For N. amazonum mesocosms, 78.9 % of the applied amount of imidacloprid was retained in plants (plant material and roots) and 17.31 % in sediment, while for E. mutata mesocosms only 0.5 % of imidacloprid was detected in plant material and roots. In this experiment, the DT of lambda-cyhalothrin in the water phase of both types of mesocosms was on average 1 day, while for imidacloprid, this was calculated to be around 1-10 days. The results obtained provide necessary information for the construction of a field scale wetland capable of efficient removal of pesticides in agricultural runoff. [ABSTRACT FROM AUTHOR]

We used three non-linear bi-phasic models, bi-exponential (BEXP), first-order double exponential decay (FODED), and first-order two-compartment (FOTC), to fit the measured degradation data for six commonly used pesticides (atrazine, terbuthylazine, bromacil, diazinon, hexazinone and procymidone) in two New Zealand soils. Corresponding DT50 and DT90 values for each compound were numerically obtained and compared against those estimated by simple first-order kinetic (SFOK) model. All 3 non-linear models gave good fit of the measured data under both soil depths and were well supported by the values obtained for the respective statistical indices (RMSE, CRM and r2). The FOTC model gave by far the best fit for most compounds, followed by the FODED and BEXP models. Overall, DT50 values derived by non-linear models for the six compounds in soils from both sites were lower than the values obtained by the SFOK model. Differences in the SFOK and the three non-linear models derived DT90were, however, an order of magnitude higher for some compounds, while for others differences were very small. Although all three non-linear models described most data by giving excellent fits, in a few instances > 5-10% asymptotes hindered the estimation of DT90 values. This work shows that when degradation deviates from first-order kinetic, application of non-linear decay models to describe the kinetics of degradation becomes important in order to derive the true end-points for pesticides in soil. [ABSTRACT FROM AUTHOR]

Abstract: Adipocere is formed from body fat in moist and oxygen-deficient decay conditions. The persistence of adipocere may cause problems for the reuse of graves after the expiration of statutory resting times in some countries. Up to now, no quantitative data existed on the persistence of adipocere in either aerated or anoxic conditions. We investigated the rate of degradation (disappearance) of adipocere in five different samples from human corpses. The experimental incubation was (a) in water without air contact, (b) in water with access to air, (c) in physiological saline with access to air, (d) on sterilized quartz sand, (e) in vitro on living soil, and (f) buried 15cm deep in field soil. The weight loss of the samples was determined after 215 (293) days and half-lives were calculated under the assumption of simple first-order kinetics. Furthermore, the nitrogen content and the fatty acid composition of the adipocere samples were analyzed. The results revealed half-lives that differ between the adipocere samples from 11 to 82 years under anaerobic conditions (mean of all samples, 37 years). In air, the half-life of adipocere was reduced to about one tenth, ranging from 0.7 to 10 years (mean of 2.8 years for all samples incubated in aerated physiological saline, mean of 4.0 years for all samples incubated on living soil in the laboratory). Burying adipocere in a biologically active field soil resulted in half-lives of disappearance from 1.2 years to 2.1 years (mean, 1.5 years). The N content of the adipocere samples ranged between 1.9 and 6.7mgNg−1. The sample with the highest N content was also that with the lowest half-life of disappearance in all types of incubation. The fatty acid analysis of the samples revealed a composition typical of adipocere, with a clear dominance of saturated acids (palmitic, myristic and stearic acid) over unsaturated ones. The variation of fatty acid composition between the different adipocere samples could only be attributed partly to their age and the burial conditions. It can be concluded that the aeration of adipocere-laden corpses will lead to a disappearance of adipocere (and hence restitution of the decay process) within a time span of several years. [Copyright &y& Elsevier]

This study was conducted to examine the toxic effects of paraquat on Daphnia magna and its behavior in Korean agricultural conditions. Acute immobilization toxicity tests on D. magna were performed for 48 h at three different exposure systems: water-alone (System A), water-sediment system (System B), and an equilibrated water-sediment system (System C). The concentration of paraquat in the System A was very stable over 48 h and the EC50 was 6.39 ppm. In contrast, the concentration of paraquat in water phase of the System B drastically decreased. The dissipation time in water (DT50) in the System B ranged from 5.45 h to 13.05 h, while the EC50 increased 3 times to 20.8 ppm. The concentration of paraquat in the water phase of the System C decreased over 90%, and no adverse effect was observed at 80 ppm. Considering that the toxicity of paraquat greatly decreased in the System B, there was a large margin between predicted environmental concentration (PEC) and the concentration that would cause adverse effects on D. magna in environmentally relevant conditions. This study clearly indicated that paraquat equilibrated in the water sediment system did not acutely affect D. magna dwelling in the aquatic ecosystems, including rice paddies of Korea. [ABSTRACT FROM AUTHOR]

We investigated dissipation and sorption of atrazine, terbuthylazine, bromacil, diazinon, hexazinone and procymidone in two contrasting New Zealand soils (0-10 cm and 40-50 cm) under controlled laboratory conditions. The six pesticides showed marked differences in their degradation rates in both top- and subsoils, and the estimated DT50 values for the compounds were: 19-120 (atrazine), 10-36 (terbuthylazine), 12-46 (bromacil), 7-25 (diazinon), 8-92 (hexazinone) and 13-60 days for procymidone. Diazinon had the lowest range for DT50 values, while bromacil and hexazinone gave the highest DT50 values under any given condition on any soil type. Batch derived effective distribution coefficient (Kdeff) values for the pesticides varied markedly with bromacil and hexazinone exhibiting low sorption affinity for the soils at either depth, while diazinon gave high sorption values. Comparison of pesticide degradation in sterile and non-sterile soils suggests that microbial degradation was the major dissipation pathway for all six compounds, although little influence of abiotic degradation was noticeable for diazinon and procymidone. [ABSTRACT FROM AUTHOR]

Flurprimidol is a plant growth regulator that can be applied as a granular formulation. Understanding flurprimidol release from a granular formulation and movement in various mediums will impact how it is used. Dissipation of flurprimidol from a granular formulation and movement through organic media and sand were evaluated in a greenhouse and laboratory experiment. Experimental variables included media type, depth, and irrigation event. Dissipation isotherms were determined by applying nonlinear regression. Mobility was evaluated using columns filled with media, which was surface-spiked with the granular formulation and then irrigated once daily for 22 consecutive days. Leachate was collected and analyzed by high-performance liquid chromatography-mass spectroscopy. Half-life (DT50), defined as time to 50% reduction, varied among sand, media, and media depth. Flurprimidol dissipation was rapid through sand with DT50 of 6 days. DT50 increased with increasing media depth from 5 to 10 cm for pine bark plus sand, 18 and 35 days, and hardwood bark plus sand, 77 and 173 days, respectively. Maximum flurprimidol leaching was a cumulative 71% of applied amounts over 22 irrigation events through the sand. Hardwood and pine bark media allowed less than 25% of flurprimidol to escape through the column. Data for all media indicated that flurprimidol was mobile through the substrates but exhibited hysteresis with pine bark and hard wood bark media. An initial pulse of flurprimidol will release slowly from this formulation over time. These results indicate that flurprimidol will dissipate from a granular formulation over time and that it will have movement through sand soil and pine bark and hardwood bark media to reach the roots of growing plants. [ABSTRACT FROM AUTHOR]

Sulfonylurea herbicides are widely used as acetolactate synthase (ALS) inhibitors due to their super-efficient activity. However, some sulfonylurea herbicides show toxicity under crop rotation due to their long degradation time, for example, chlorsulfuron. Our research goal is to obtain chlorsulfuron-derived herbicides with controllable degradation time, good crop safety and high herbicidal activities. Based on our previously reported results in acidic soil, we studied the degradation behaviors of 5-dialkylamino-substituted chlorsulfuron derivatives (NL101–NL108) in alkaline soil (pH 8.39). The experimental data indicate that addition of the 5-dialkylamino groups on the benzene ring of chlorsulfuron greatly accelerated degradation in alkaline soil. These chlorsulfuron derivatives degrade 10.8 to 51.8 times faster than chlorsulfuron and exhibit excellent crop safety on wheat and corn (through pre-emergence treatment). With a comprehensive consideration of structures, bioassay activities, soil degradation and crop safety, it could be concluded that 5-dialkylamino-substituted chlorsulfuron derivatives are potential green sulfonylurea herbicides for pre-emergence treatment on both wheat and corn. The study also provides valuable information for the discovery of new sulfonylurea herbicides for crop rotation. [ABSTRACT FROM AUTHOR]

Abstract: A kinetic model approach for determination of biodegradation half-lives from soil simulation testing is presented. The model describes transformation of the parent compound to metabolites and formation of bound (non-extractable) residues as well as mineralization in soil under aerobic laboratory conditions. Experimental data for several pesticide compounds from various soil simulation tests are used for fitting kinetic rate constants. Formation of bound residues, either from parent or metabolites or from both, can be described by first-order kinetics for all examined compounds. Correlation of kinetic rate constants of primary degradation and formation of bound residues from parent compound suggests a common mechanism, presumably co-metabolic microbial activity, for both processes. Inverse modelling allows for estimation of primary degradation half-life DegT50 instead of disappearance time DT50. Application of the DegT50 approach in PBT assessment might result in a different persistent classification for which the developed model delivers an appropriate evaluation tool. [Copyright &y& Elsevier]

The article discusses the research on statistical tools for determining the appropriate selection of regression models for analysis of environmental fate datasets. This research showed through a case study that the inappropriate use of pseudo-first-order regression models can result in inaccurate estimates of soil degradation rates. Statistical tools which can be used to determine an appropriate statistical model to suit a certain environmental fate dataset were proposed. It is concluded that the results from this study depicted that unless the proposed diagnostic and statistical procedures were used, inaccurate estimates of dissipation times may result.

In a field study carried out at three different locations, the dissipation of spiromesifen on cotton and chili was studied and its DT50, and DT99 were estimated at each location. Spiromesifen was sprayed on chili at 96 and 192 g a.i. ha−1 and cotton at 120 and 240 g a.i. ha−1. Samples of chili fruits were drawn at 0, 1, 3, 5, 7, 10, 15, 21, 30 days after treatment and that of cotton seed and lint at first picking and harvest. Soil samples were drawn 30 days after treatment from 0 to 15 and 15 to 30 cm layer. Quantification of residues was done on GC–MS in Selected Ion Monitoring (SIM) mode in mass range 271–274 m/z. The LOQ of this method was found 0.033 μg g−1, LOD being 0.01 μg g−1. The DT50 of spiromesifen when applied at recommended doses in chili fruits was found to be 2.18–2.40 days. Ninety-nine percent degradation was found to occur within 14.5–16.3 days after application. Residues of spiromesifen were not detected in cotton seed and lint samples at the first picking. In soil, no residues of spiromesifen were detectable 15 days after treatment. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports the results of a laboratory study aimed at defining the leaching potential of the following pesticides and respective metabolites belonging to the families of N-methylcarbamates and triazines: benfuracarb (BF), carbofuran (CF), 3-keto-carbofuran (3KC) and 3-hydroxy-carbofuran (3HC), atrazine (ATR), simazine (SIM), terbuthylazine (TER), deethylatrazine (DEA), deisopropylatrazine (DIA) and desethylterbuthylazine (DET). All tested compounds, but BF, are very mobile in soil. Triazines exhibited a relatively high persistence, especially DEA, with a DT50 of 72 days. On the contrary, all the tested carbamates resulted easily degradable in soil with a partial exception represented by CF, with a DT50 of 12 days. The GUS indices show high leaching potentials for all the tested triazines and CF. The GUS index of 3KC lies in the typical area of transient compounds; those of BF and 3HC clearly exhibited a non-leaching behaviour. In the leachate corresponding to the BF column, the parent compound was found at low concentration while its main metabolite, CF, reached much higher values. Also, when applied as parent compound, CF was determined at high values, whereas its metabolites 3KC and 3HC were never detected in the leachates. As to triazines, in the ATR column, the parent compound was found at high levels in the leachate, where DEA exhibited values more than 4 times higher than DIA. In the SIM column DIA reached levels 8-fold higher than those in the ATR column. TER occurred at levels close to that of ATR in the respective leachate; DET was found at high levels whereas DIA was not detectable. [Copyright &y& Elsevier]

Spiromesifen (Oberon®) is a new insecticide and miticide of chemical class ketoenol active against white flies (Bemisia spp. , Trialeuroides spp. ) and spider mites (Tetranychus and Panonychus spp. ). Due to its potential significance in insect resistance management, it is important to establish its behaviour on crop and environment. In the present study, the degradation/dissipation of spiromesifen on tea crop under tropical environmental conditions was studied and its DT50 (t 1/2), and DT90 (time to reduce to 90% of the initial value) were estimated. Spiromesifen was sprayed on tea crop after first rain flush at four different locations @ 96 and 192ga. I. Ha−1. Samples of tea leaves were drawn at 0, 1, 3, 5, 7, 10, 15, 21 and 30 days after treatment and that of soil at 10 days after treatment and at harvest from 0 to 15 and 15 to 30cm layers. After crude extraction of tea leaves for spiromesifen residues with acetone:water, the contents were partitioned with cyclohexane:ethyl acetate and cleaned up on Florosil column. Soil residues were also extracted similarly. Quantification of residues was done on GC–MS in Selected Ion Monitoring (SIM) mode in mass range 271–274 m/z. The LOQ of this method was found to be 0. 05μgg−1 while LOD being 0. 015μgg−1. The DT50 of spiromesifen when applied at recommended doses in tea leaves was found to be 5. 0–8. 5 days. Ninety-nine percent degradation was found to occur within 33–57 days after application. In soil, no residues of spiromesifen were detectable 10 days after treatment. [Copyright &y& Elsevier]

Abstract: A mixture of four tetracyclines; oxytetracycline (OTC), chlortetracycline (CTC), tetracycline (TC), and doxycycline (DC) was applied in fifteen 12000l outdoor microcosms at four treatment levels plus controls each with three replicates (n =3). The dissipation times of parent compounds were monitored and half-lives (DT50) of 1–4 days, depending on treatment level were recorded. This is in accordance with half-lives from previous findings in bench-top experiments. Parent compound DT50, were determined using HPLC–UV. Furthermore, the samples were analyzed for ten different tetracycline products using LC/MS/MS. Two products were found for chlortetracycline; 4-epi-anh-chlortetracyline and the iso-chlortetracycline. Iso-forms were only found for CTC and only at the highest treatment (300μgl−1). The half-lives, trajectories, and relative amounts of the products were analogous for all four tetracyclines. DT50 for products were less than 1.2 days. Formation of 4-epi-anh-tetracyclines, occurred at neutral to weak alkaline conditions. [Copyright &y& Elsevier]

Abstract: This study reports the results of Koc and soil DT50 experiments used for the definition of the leaching potential through the GUS Index of five metabolites: endosulfan sulphate (ES) from endosulfan, 2,6-dichlorobenzoic acid (DBA) from dichlobenil, 3,4-dichloroaniline (DCA) from propanil, 2,4-dichlorophenol (DCP) from 2,4-d and 4-chloro-2-methylphenol (CMP) from MCPA. The Koc values for all the compounds were lower than 300, indicating high potential mobility in soil. Soil DT50 values were around 24 days for DBA and ES, and <3 days for the other three metabolites. The leaching potential expressed by the GUS Index was high for DBA and ES (>2.8) and low to negligible for CMP, DCA and DCP (<0.32). In short, the intrinsic characteristics of DBA and ES are typical of leachers, but their significance as groundwater contaminants should be further surveyed through leaching in soil columns treated with their parent compounds. [Copyright &y& Elsevier]

The fate and effects of azadirachtin were examined using in situ enclosures deployed in a typical forest pond of northern Ontario. A commercial azadirachtin-based insecticide formulation, Neemix 4.5, was applied as the test substance. Fate studies were conducted to determine kinetics and persistence of azadirachtin isomers A and B in the aqueous phase and whether either isomer partitioned significantly to bottom sediments or pore water. Aqueous azadirachtin residues dissipated following slow linear kinetics with time to 50% dissipation of 25, 45, and 30 days for azadirachtin A, azadirachtin B, and total residues, respectively. Sediment pore water concentrations increased slowly, reaching low-level equilibrium with the overlying water column toward the end of the summer season. No significant sorption to bottom sediments was observed. Results demonstrated that fate and dissipation of azadirachtin residues are consistent from year to year and that biota may be chronically exposed to diminishing levels of azadirachtins A and B in aqueous phase under conditions of a typical forest pond environment. [Copyright &y& Elsevier]

Pesticide residues in crop plants are routinely measured in an edible commodity or in feed items to determine safe use. Pesticides present as dislodgeable foliar residues (DFR) are measured for use in non-dietary risk assessments where worker, resident and bystander re-entry may lead to contact with the treated foliage. Possible correlations between dietary and DFR residue decline have been investigated considering data from 177 dietary residue trials along with 56 DFR trials from outdoor studies on the same crops besides residue decline data available in the Plant Properties Database (PPDB).The residue studies proved to follow the non-normal distribution and the comparison between DT 50 of both types of residues for all the active substances revealed higher numerical DT 50 mean values of the dietary residue compared to the DFRs. The dissipation from dietary residue studies is slower with a higher population mean compared to the mean for DFR studies for most active substances studied. A DT 50 value from dietary residue studies could potentially act as a conservative surrogate DT 50 for DFR which could be useful in determining the length of DFR studies and benefit both the agrochemical industry and the regulatory bodies in supporting non-dietary pesticide risk assessment. • First study to investigate correlation between dietary and non-dietary residues. • Half-lives from dietary residue could act as a surrogate for dislodgeable residue. • Correlation between pesticide residue half-lives could refine the risk assessment. • This correlation would help both regulatory bodies and agrochemical industry. • This correlation could save time, money and resources during pesticide registration. [ABSTRACT FROM AUTHOR]