Exploring the dynamic behaviors of five pesticides in lettuce: Implications for consumer health through field and modeling experiments

Lettuce, a globally consumed nutritious vegetable, is often linked to concerns regarding pesticide residues. To address this issue, we conducted field trials and utilized dynamiCROP modeling to examine the uptake, distribution, translocation, and dissipation of five pesticides (λ-cyhalothrin, difenoconazole, acetamiprid, dimethomorph, and β-cypermethrin) commonly detected in lettuce. At harvest, pesticides residues were below the maximum residue limits (MRLs) at 0.05, 0.39, 0.047, 0.72, and 0.072 mg kg-1, respectively. Simulation results elucidated distinct behaviors of the pesticides following application to lettuce foliage across various compartments. However, all pesticides exhibited a common dissipation trend, initially stabilizing or increasing before gradually declining. For all five pesticides, the largest contribution of residues on lettuce leaves came from the leaf surface during the early period after application, and from the soil in the long term. Health risk assessments indicated negligible risks associated with consuming lettuce containing these pesticides, both in the short and long term.

Accumulation, translocation, metabolism and subcellular distribution of mandipropamid in cherry radish: A comparative study under hydroponic and soil-cultivated conditions

The accumulation and transportation of pesticides in plants can provide valuable insights to assess potential risks and ensure food safety. The uptake and downward translocation of mandipropamid were examined in hydroponic and soil-cultivated cherry radishes. The uptake of mandipropamid in cherry radish was rapid (bioconcentration factors of 1.1-10.7), whereas the downward translocation was limited (translocation factors of 0.1-0.9). The subcellular distribution results indicated a predominant accumulation in solid fractions of cherry radish (proportions of 52.9-98.7%), potentially because of the hydrophobicity (log Kow of 3.2) of mandipropamid. Owing to the decrease in half-life (>10%), the cultivation of cherry radish enhanced the dissipation of mandipropamid in both nutrient solutions (without stereoselectivity) and soils (with stereoselectivity). In addition, eleven metabolites and three pathways are proposed. This study provides valuable insights for the varying extent of translocation and proper utilization and safety evaluation of mandipropamid in crops.

Evaluation of Iron Chlorin e6 disappearance and hydrolysis in soil and garlic using salting-out assisted liquid-liquid extraction coupled with high-performance liquid chromatography and ultraviolet-visible detection

Iron Chlorin e6 (ICE6), a star plant growth regulator (PGR) with independent intellectual property rights in China, has demonstrated its efficacy through numerous field experiments. We innovatively employed salting-out assisted liquid-liquid extraction (SALLE) with HPLC-UV/Vis to detect ICE6 residues in water, soil, garlic seeds, and sprouts. Using methanol and a C18 column with acetonitrile: 0.1% phosphoric acid mobile phase (55:45, v:v), we achieved a low LOQ of 0.43 to 0.77 μg kg-1. Calibration curves showed strong linearity (R2 > 0.992) within 0.01 to 5.00 mg kg-1. Inter-day and intra-day recoveries (0.05 to 0.50 mg kg-1) demonstrated high sensitivity and accuracy (recoveries: 75.36% to 107.86%; RSD: 1.03% to 8.78%). Additionally, density functional theory (DFT) analysis aligned UV/Vis spectra and indicated ICE6's first-order degradation (2.03 to 4.94 days) under various environmental conditions, mainly driven by abiotic degradation. This study enhances understanding of ICE6's environmental behavior, aids in risk assessment, and guides responsible use in agroecosystems.

Dissipation and potential risk of tristyrylphenol ethoxylate homologs in peanuts by spraying and root irrigation: A comparative assessment

Peanuts, known for their nutritional value, health benefits, and delicious taste, are susceptible to agricultural chemical contamination, posing a challenge to the peanut industry in China. While tristyrylphenol ethoxylates (TSPEOs) have garnered attention for their widespread use in pesticide formulations, their dissipation and potential risks in peanuts remain a gap in knowledge. This study, unique in its focus on TSPEOs, investigates their dissipation and potential risks under two common application modes: spraying and root irrigation. The concentration of total TSPEOs in peanut plants was significantly higher when sprayed (435-37,693 μg/kg) than in root irrigation (24-1602 μg/kg). The dissipation of TSPEOs was faster in peanuts and soil when sprayed, with half-lives of 3.67-5.59 d (mean: 4.37 d) and 5.41-7.07 d (mean: 5.95 d), respectively. The residue of TSPEOs in peanut shells and soil were higher with root irrigation (8.9-65.2 and 25.4-305.1 μg/kg, respectively) than with spraying (5.4-30.6 and 8.8-146.5 μg/kg, respectively). These results indicated that the dissipation behavior of TSPEOs in peanuts was influenced by application modes. While the healthy and ecological risk assessments of TSPEOs in soil and peanut shells showed no risks, root irrigation might pose a higher potential risk than spraying. This research provides valuable data for the judicious application of pesticides during peanut cultivation to enhance pesticide utilization and reduce potential risks.

Dissipation, processing factors and dietary risk assessment of the bioinsecticide abamectin in herbal plants belonging to Lamiaceae family from open field to herbal tea infusion

Abamectin, the mixture of avermectin B1a and B1b, is widely used as a bioinsecticide and is an alternative to chemical pest control from insects. To our knowledge, its behaviour is not fully recognized, especially in herbs. Thus, the objective of this study was to investigate the environmental fate of abamectin in herbal plants belonging to the Lamiaceae family, its dissipation in open field studies laboratory processing treatments and dietary risk assessment. Three medicinally and culinary important species of herbs: Melissa officinalis L., Mentha × piperita L. and Salvia L. were treated with single and double dose than recommended on the label during their cultivation (BBCH 11-29). Residues were monitored using the QuEChERS method followed by the LC-MS/MS. The dissipation pattern of the sum of avermectin B1a and B1b and their persistence were observed 14 d after spraying. Abamectin decline was very rapid in plants and followed the first-order kinetics model. The half-life (t1/2) was in the range of 0.96-1.08 d (single dose) and 0.93-1.02 d (double dose). The pre-harvest intervals (decrease to the level of 0.01 mg kg-1) were 7.29-7.92 d at single and 7.99-8.64 d at double dose application. Herbal infusion preparation in previously washed and dried mint, lemon balm and sage leaves was the key processing step in the removal of abamectin residues. The reduction of initial deposits after single dose treatment was noted up to 65% (PF = 0.35-0.67) and up to 79% after double dose application (PF = 0.21-0.72) in herbal tea. Acute risk assessment of children and adults for the highest residues in EFSA PRIMo model at single and double dose expressed as hazard quotients (HQ) were <1, indicating no risk to humans via consumption of the herbal products. The data provide a better understanding of abamectin behaviour in herbal plants and can help assure herbs' safety for consumers.

Type of probability distribution reflects how close mixing dynamics in river chemistry are to thermodynamic equilibrium

The distribution of geochemical species are typically either (log)normally distributed or follow power laws. Here we link these types of distributions to the dynamics of the system that generates these distributions, showing that power laws can emerge in dissipative systems far from equilibrium while (log)normal distributions are found for species for which the concentrations are close to equilibrium. We use observations of the chemical composition of river water from the sampling space in central Italy as well as discharge data to test this interpretation. We estimate the dissipation rate that results when groundwater drains into the river and the dissolved chemical species mix with the river water. We show that calcium (Ca2+) and bicarbonate (HCO3-) concentrations are close to saturation along most of the downstream length of the Arno river, with decreasing dissipation rates and a lognormal distribution, while sodium (Na+) and chloride (Cl-) concentrations increase substantially downstream, show increased dissipation rates, and are power-law distributed. This supports our hypothesis that power law distributions appear to be indicative of dissipative systems far from thermodynamic equilibrium, while (log)normal distributions indicate weakly dissipative systems close to equilibrium. What this implies is that probability distributions are likely to be indicative of the thermodynamics of the system and the magnitude of disequilibrium constrains the range over which power-law scaling may be observed. This should help us to better identify the generalities and mechanisms that result in these common types of distributions and to better classify variability in systems according to how dissipative these are.

Exploring the influence of invasive weed biochar on the sorption and dissipation dynamics of imazethapyr in sandy loam soil

The management of invasive weeds on both arable and non-arable land is a vast challenge. Converting these invasive weeds into biochar and using them to control the fate of herbicides in soil could be an effective strategy within the concept of turning waste into a wealth product. In this study, the fate of imazethapyr (IMZ), a commonly used herbicide in various crops, was investigated by introducing such weeds as biochar, i.e., Parthenium hysterophorus (PB) and Lantana camara (LB) in sandy loam soil. In terms of kinetics, the pseudo-second order (PSO) model provided the best fit for both biochar-mixed soils. More IMZ was sorbed onto LB-mixed soil compared to PB-mixed soil. When compared to the control (no biochar), both PB and LB biochars (at concentrations of 0.2% and 0.5%) increased IMZ adsorption, although the extent of this effect varied depending on the dosage and type of biochar. The Freundlich adsorption isotherm provided a satisfactory explanation for IMZ adsorption in soil/soil mixed with biochar, with the adsorption process exhibiting high nonlinearity. The values of Gibb's free energy change (ΔG) were negative for both adsorption and desorption in soil/soil mixed with biochar, indicating that sorption was exothermic and spontaneous. Both types of biochar significantly affect IMZ dissipation, with higher degradation observed in LB-amended soil compared to PB-amended soil. Hence, the findings suggest that the preparation of biochar from invasive weeds and its utilization for managing the fate of herbicides can effectively reduce the residual toxicity of IMZ in treated agroecosystems in tropical and subtropical regions.

Potential effects of individual and combined exposure to tetraconazole and cadmium on zebrafish from the perspective of enantioselectivity and intestinal microbiota

As the wide use of pesticides, they could form combined pollution with heavy metals, which would affect their environmental behaviors and toxic effects. Particularly, the effects would be more intricate for chiral pesticides. In this study, the accumulation and dissipation trends of tetraconazole enantiomers in zebrafish were investigated by individual and combined exposure of cadmium (Cd) and tetraconazole (including racemate and enantiomers) after confirming the absolute configuration of tetraconazole enantiomer. For the enantiomer treatments, Cd enhanced the accumulation of S-(+)-tetraconazole, but declined the concentrations of R-(-)-tetraconazole in zebrafish. The dissipation half-lives of tetraconazole enantiomers were extended by 1.65-1.44 times after the combined exposure of Cd and enantiomers. The community richness and diversity of intestinal microbiota were reduced in all treatments, and there were significant differences in R + Cd treatment. There was synergistic effect between Cd and S-(+)-tetraconazole for the effects on the relative abundances of Fusobacteria, Firmicutes, Proteobacteria, Actinobacteria, and Bacteroidetes. For R-(-)-tetraconazole, Cd mainly exhibited antagonistic effects. In the combined exposure of Cd and S-(+)-tetraconazole, the relative abundance changes of Cetobacterium (Fusobacteria, increase) and Edwardsiella (Proteobacteria, decrease) might affect the carbohydrate metabolism and energy metabolism, and led to the increase of S-(+)-tetraconazole bioaccumulation concentration. In the combined exposure of Cd and R-(-)-tetraconazole, Cd could increase the relative abundance of Edwardsiella (Proteobacteria), and affect the amino acid metabolism, which might reduce the bioaccumulation concentration of R-(-)-tetraconazole. This study reported for the first time that the abundance of intestinal microbiota in zebrafish might affect the bioaccumulation and dissipation of tetraconazole enantiomers, and would provide new insight for the study of combined pollutions.

Residual estimation of spirotetramat and its metabolites in chilli and soil by LC-MS/MS

Two applications of spirotetramat were done to study the dissipation and persistence of spirotetramat and its four different metabolites in chilli and soil at 10 days interval. Total spirotetramat residues were estimated by LC-MS/MS instrument. The mean initial deposits of total spirotetramat after application of spirotetramat 15.31 OD @ 60 (X dose), 75 (1.25 × dose) and 120 (2 × dose) g a.i. ha-1 on green chilli were found to vary from 0.38 to 0.83 mg kg-1 during the initial year. Spirotetramat and its metabolite residues in green chilli were found to be below limit of quantification (0.01 mg kg-1) after 15 days of application. The spirotetramat cis enol (the major metabolite) was formed in both the soil and the plant. The residues of spirotetramat-monohydroxy were below LOQ irrespective of any substrate during the estimation. In soil, the total initial spirotetramat deposits for the 1st year were found 0.09 for X dose, 0.12 for 1.25 × dose and 0.20 mg kg-1 for 2 × dose. After 3 days for both X and 1.25 × doses and 5 days for 2 × dose, the total spirotetramat residues were below LOQ. The spirotetramat's half-life values have been determined to be between 3.19 and 3.93 days and 1.00 and 1.59 days, respectively, in soil and green chilli fruits. One day waiting period is proposed for the safe consumption of green chilli when the spirotetramat was applied irrespective of the dose.

Investigation of dissipation kinetics and half-lives of fipronil and thiamethoxam in soil under various conditions using experimental modeling design by Minitab software

To determine the extent of pesticide buildup and their environmental contamination, the environmental half-lives of pesticides are examined. The influence of the factors affecting the half-lives of fipronil and thiamethoxam including soil type, sterilization, temperature, and time and their interactions was studied using experimental modeling design by Minitab software. Based on the dissipation kinetics data, fipronil concentrations reduced gradually over 60 days while thiamethoxam concentrations decreased strongly. Also, fipronil and thiamethoxam dissipated more rapidly in calcareous soil than in alluvial soil. Thiamethoxam, however, disappeared more rapidly than fipronil in all treatments. Incubation at 50 °C leads to rapid the pesticide degradation. For prediction of the dissipation rate, model 5 was found to be the best fit, Residue of insecticide (%) = 15.466 - 11.793 Pesticide - 1.579 Soil type + 0.566 Sterilization - 3.120 Temperature, R2 = 0.94 and s = 3.80. Also, the predicted DT50 values were calculated by a model, DT50 (day) = 20.20 - 0.30 Pesticide - 7.97 Soil Type + 0.07 Sterilization - 2.04 Temperature. The shortest experimental and predicted DT50 values were obtained from treatment of thiamethoxam at 50 °C in calcareous soil either sterilized (7.36 and 9.96 days) or non-sterilized (5.92 and 9.82 days), respectively. The experimental DT50 values of fipronil and thiamethoxam ranged from 5.92 to 59.95 days while, the modeled values ranged from 9.82 to 30.58 days. According to the contour plot and response surface plot, temperature and sterilization were the main factors affecting the half-lives of fipronil and thiamethoxam. The DT50 values of fipronil and thiamethoxam increased in alluvial soil and soil with low temperature. In general, there is a high agreement between the experimental results and the modeled results.

Synergistic mechanism and environmental behavior of tank-mix adjuvants to topramezone and atrazine

An effective way to reduce herbicide quantity is to use adjuvants in order to optimize the amount of herbicide and improve its control efficiency. In order to screen for efficient herbicide tank-mix adjuvants, improve the control of weeds in maize fields, reduce the amount of effective ingredients, and improve the adsorption and digestion behavior of herbicides in soil, this study evaluated the synergistic effects and soil behavior of four types of tank-mix adjuvants combined with herbicides. Different types of adjuvants can enhance herbicide production. Surface tension was significantly reduced by 13% after the pesticide solution was applied with AgroSpred™ Prime. The contact angle with the foliar surface was significantly reduced and solution wettability improved using Atp Lus 245-LQ-(TH). The permeability of topramezone and atrazine in leaves of Amaranthus retroflexus L. and Digitaria sanguinalis (L.) Scop. was increased by 22-96% after adding either tank-mix adjuvant. The solution drying time and maximum retention on leaves were not affected by the tank-mix adjuvants. Ethyl and methylated vegetable oils can reduce the adsorption of topramezone in the soil, thus reducing its half-life in soil. The tank-mix adjuvants had no significant effect on soil dissipation or adsorption of atrazine. AgroSpred™ Prime and Atp Lus 245-LQ-(TH) have the best synergistic effect on topramezone and atrazine in the control of A. retroflexus L. and D. sanguinalis (L.) Scop. in maize fields.

Characteristics of bacterial community and extracellular enzymes in response to atrazine application in black soil

The ecological functioning of black soil largely depends on the activities of various groups of microorganisms. However, little is known about how atrazine, a widely used herbicide with known harmful effects on the environment, influences the microbial ecology of black soil, and the extracellular enzymes related to the carbon, nitrogen and phosphorus cycles. Here, we evaluated the change in extracellular enzymes and bacterial community characteristics in black soil after exposure to various concentrations of atrazine. Low concentrations of applied atrazine (10 - 20 mg kg-1) were almost completely degraded after 120 days. At high concentrations (80 - 100 mg kg-1), about 95% of the applied atrazine was degraded over the same period. Additionally, linear fitting of data indicated that the total enzymatic activity index (TEI) and bacterial α-diversity index were negatively correlated with atrazine applied concentration. The atrazine had a greater effect on bacterial beta diversity after 120 days, which differentiated species clusters treated with low and high atrazine concentrations. Soil bacterial community structure and function were affected by atrazine, especially at high atrazine concentrations (80 - 100 mg kg-1). Key microorganisms such as Sphingomonas and Nocardioides were identified as biomarkers for atrazine dissipation. Functional prediction indicated that most metabolic pathways might be involved in atrazine dissipation. Overall, the findings enhance our understanding of the factors driving atrazine degradation in black soil and supports the use of biomarkers as indicators of atrazine dissipation.

Spatiotemporal dynamics and modeling of thiacloprid in paddy multimedia systems with the effect of wetting-drying cycles

The widespread presence of thiacloprid (THI), a neonicotinoid, raises concerns for human health and the aquatic environment due to its persistence, toxicity, and bioaccumulation. The fate of THI in paddy multimedia systems is mainly governed by irrigation practices, but the potential impacts remain poorly documented. This study investigated the effects of water management practices on THI spatiotemporal dynamics in paddy multimedia systems by combining soil column experiments and a non-steady-state multimedia model. The results indicated the wetting-drying cycle (WDC) irrigation reduced THI occurrences in environmental phases (i.e., soil, interstitial water, and overlying water) and accelerated the THI loss through the THI aerobic degradation process. THI occurrences in the soil and water phases decreased from 18.8% for conventional flooding (CF) treatment to 9.2% for severe wetting-drying cycle (SW) treatment after 29 days, while the half-lives shortened from 11.1 days to 7.3 days, respectively. Meanwhile, the WDC decreased THI outflow from leakage water, which reduced the THI risk of leaching. There was no significant difference in THI plant uptake and volatilization between CF and WDC treatments. The mean proportions of THI fate in paddy multimedia systems followed the order: THI degradation (57.7%), outflow from leakage water (25.5%), occurrence in soil (12.4%), plant uptake (3.4%), occurrence in interstitial water (0.7%), occurrence in overlying water (0.3%), volatilization (<0.1%) after 29 days. The sensitivity analysis identified the soil organic carbon partition coefficient (KOC) as the most sensitive parameter affecting THI's fate. In addition, the topsoil layers of 0-4 cm were the main sink of THI, holding 67% of THI occurrence in the soil phase. The THI occurrence in interstitial water was distributed evenly throughout the soil profile. These findings made beneficial theoretical supplements and provided valuable empirical evidence for water management practices to reduce the THI ecological risk.

Analysis, residue behaviour and risk assessment of combination product of iprovalicarb + copper oxychloride in representative fruiting vegetables, cucurbit and in soil using LC-MS/MS and ICP-MS

Combination product of two herbicides, i.e. iprovalicarb and copper oxychloride, is a new formulation. There is paucity of data on the dissipation pattern and risk assessment of this combination product in crops. To understand the dissipation behaviour/kinetics of this product, a supervised field trial was undertaken on cucumber and tomato. Method validation for a QuEChERS-based method for analysis of these pesticides from cucumber and tomato matrices reveals that all the parameters were within the acceptance range in accordance with SANTE. The limit of quantitation (LOQ) for iprovalicarb in cucumber and tomato fruits, and in soil matrices when analysed on LC-MS/MS was established at 0.01 mg kg-1. Similarly, the LOQ for copper oxychloride (as copper) on ICP-MS was established at 0.5 mg kg-1 in cucumber and tomato fruits and 5.0 mg kg-1 in soil. Dissipation of iprovalicarb was slower in tomato fruits as compared to cucumber fruits. The initial accumulation of the residues of iprovalicarb was 0.073 and 0.243 mg kg-1 in cucumber and 0.214 and 0.432 mg kg-1 in tomato fruits at standard and double dose, respectively. Similarly, copper oxychloride residues were 3.51 and 6.45 mg kg-1 in cucumber and 1.26 and 2.56 mg kg-1 in tomato fruits at standard and double dose, respectively. The residues were below LOQ in cucumber fruits, tomato fruits and soil at the time of harvest. The residues of copper oxychloride persisted till harvest time in cucumber fruits and in soil. A preharvest interval (PHI) of 3 day is recommended on safer side for the combination product of iprovalicarb + copper oxychloride. Theoretical maximum daily intake (TMDI) is less than maximum permissible intake (MPI) for iprovalicarb and copper oxychloride at both the doses from 0 day and onward. The results from the present study can be of immense importance for establishing label claims, maximum residue limits (MRLs) and risk assessment by national and international regulatory agencies.

Thiamethoxam dynamics in pepper plants: Deciphering deposition and dissipation pattern across diverse planting modes and regions

To reduce the application dosage of thiamethoxam (TMX), we investigated the deposition and dissipation patterns in a pepper-planted ecosystem under different planting modes across four regions in China, namely Hainan (HN), Zhejiang (ZJ), Anhui (AH) and Hebei (HB). This study focused on the deposition and dissipation of TMX at concentrations of 63.00, 47.25, 31.50, 23.63 and 15.75 g a.i.hm-2. As the application dose increased, the deposition amount of TMX initially increased in the plants and cultivated soil, showing obvious geographic differences in four cultivation areas. Surprisingly, the initial amount of TMX deposited the pepper-cultivated greenhouse of ZJ and AH was 1.1-2.1-fold and 1.0-3.6-fold higher than that in the open field system at the same application dose, respectively. In pepper leaves, stems, fruits and soil, the dissipation exhibited rapid growth and then slowed. However, the residual concentration showed an increasing trend, followed by a subsequent decrease in the pepper roots. In different planting regions, the dissipation rate of TMX followed the order HN > ZJ > AH > HB in pepper plants and cultivated soil. In comparison to the open field, the total TMX retention rate in greenhouse was higher, indicating overall greater persistence in the greenhouse conditions. These findings reveal the deposition and dissipation characteristics of TMX within the pepper-field ecosystem, offering a significant contribution to the risk assessment of pesticides.

Fate and toxicity of 2,4-D and fipronil in mesocosm systems

2,4-D and fipronil are among Brazil's most used pesticides. The presence of these substances in surface waters is a concern for the aquatic ecosystem health. Thus, understanding the behavior of these substances under environmentally relevant conditions is essential for an effective risk assessment. This study aimed to determine the degradation profiles of 2,4-D and fipronil after controlled application in aquatic mesocosm systems under influencing factors such as environmental aspects and vinasse application, evaluate pesticide dissipation at the water-sediment interface, and perform an environmental risk assessment in water and sediment compartments. Mesocosm systems were divided into six different treatments, namely: control (C), vinasse application (V), 2,4-D application (D), fipronil application (F), mixture of 2,4-D and fipronil application (M), and mixture of 2,4-D and fipronil with vinasse application (MV). Pesticide application was performed according to typical Brazilian sugarcane management procedures, and the experimental systems were monitored for 150 days. Pesticide dissipation kinetics was modeled using first-order reaction models. The estimated half-life times of 2,4-D were 18.2 days for individual application, 50.2 days for combined application, and 9.6 days for combined application with vinasse. For fipronil, the respective half-life times were 11.7, 13.8, and 24.5 days. The dynamics of pesticides in surface waters resulted in the deposition of these compounds in the sediment. Also, fipronil transformation products fipronil-sulfide and fipronil-sulfone were quantified in water 21 days after pesticide application. Finally, performed risk assessments showed significant potential risk to environmental health, with RQ values for 2,4-D up to 1359 in freshwater and 98 in sediment, and RQ values for fipronil up to 22,078 in freshwater and 2582 in sediment.

Assessment of degradation mechanism of imidacloprid residues in grape rhizosphere soil by UHPLC-Orbitrap™-MS and its residual impact on soil enzyme activity

Imidacloprid (IM) is a systemic insecticide persistent in the environment and possesses a negative impact on the non-targeted ecosystem. The objective of the present study was to evaluate the dissipation and degradation mechanism of IM residues in grape rhizosphere soil and to investigate its residual effect on soil enzyme activity at different IM spiking levels. The half-life of IM residue in soil was 27, 36, and 43.5 days at a spiking level of 1, 10, and 50 mg kg-1, respectively following a bi-phasic first + first-order dissipation kinetics. UHPLC-Orbitrap™-MS analysis by targeted metabolomics approach revealed that IM metabolites such as IM-amine analogue, guanidine (reduction), 5-hydroxy IM (hydroxylation), IM-Urea (oxidation), reduced NO analogue of IM (oxidation), and olefin of guanidine IM (dehydrogenation) were identified and proposed the degradation mechanism in grape rhizosphere soil. Toxicity of IM residues on five extracellular enzymes, viz., dehydrogenase, acid phosphatase, alkaline phosphatase, β-glucosidase, and urease revealed that activity of dehydrogenase, acid phosphatase, and alkaline phosphatase remained unaffected at 60th day of sampling. The β-glucosidase and urease were negatively affected throughout the incubation period indicating the influence of IM residues on carbon and nitrogen mineralization in soil. Thus, long-term exposure of IM to grape rhizosphere through soil drenching could affect soil enzyme activity which has a negative effect on the soil nutrient cycle and soil microbiome.

Dissipation behavior and dietary risk assessment of cyclaniliprole and its metabolite in cabbage under field conditions

Cyclaniliprole, a novel diamide insecticide, can successfully control Spodoptera litura (Fabricius, 1775) in cabbage. Understanding the residual level of cyclaniliprole in crops and the risk related to its dietary intake is imperative for safe application. Here, we established a simplified, sensitive method for simultaneous analysis of cyclaniliprole and its metabolite NK-1375 (3-bromo-2-((2-bromo-4H-pyrazolo[1,5-d]pyrido[3,2-b]-[1,4]oxazin-4-ylidene)amino)-5-chloro-N-(1-cyclopropylethyl)benzamide) in cabbage by liquid chromatography-tandem mass spectrometry (LC-MS/MS) to investigate their dissipation behavior and residual characteristics. Cyclaniliprole showed rapid dissipation in cabbage and had a half-life of 1.8-2.7 days. The highest residue of total cyclaniliprole (sum of cyclaniliprole and NK-1375) in cabbage from different pre-harvest intervals (3 and 5 days) was 0.25 mg/kg. Our results confirmed the generally low dietary risk quotient of cyclaniliprole (0.243-1.036%) among different age and gender groups in China. Therefore, cyclaniliprole did not pose an unacceptable risk to consumers. This study contributes to setting cyclaniliprole maximum residue limit in cabbage by assessing its dissipation fate and food safety risks.

Dissipation kinetics, decontamination, consumer risk assessment and monitoring of flonicamid and imidacloprid residues in capsicum under open field and polyhouse condition

Liquid chromatography mass spectrometry (LC-MS)-based detection of flonicamid, imidacloprid and 6-chloronicotinic acid residues was validated and analysed in capsicum fruit, processed products and soil. The standard concentrations (0.0025 to 0.25 μg mL-1) of insecticides had a good linear curve (r2>0.99). Limit of detection and limit of quantification values were 0.0025 and 0.01 mg kg-1, respectively. The accuracy (80.53 to 100.33 %) of capsicum matrices and soil (89.41 to 100.52 %) and precision (RSD <10%) were established. Dissipation of imidacloprid (20 and 40 g a.i. ha-1) and flonicamid (75 and 150 g a.i. ha-1) at single (X) and double dose (2X) was studied under open field and polyhouse conditions. Under open field conditions, the flonicamid and imidacloprid residues persisted with half-life of 1.98, 2.90 days (X) and 2.80, 3.14 (2X) days, respectively. While under polyhouse conditions, the flonicamid and imidacloprid residues persisted with a half-life of 2.84, 3.66 (X) and 3.24, 3.97 (2X) days, respectively. The metabolite, 6-CNA, was not detected in any samples under open field and polyhouse condition. Among decontamination treatments, cooking in boiling water for 10 minutes reduced 78 to 81.60 percent of imidacloprid and flonicamid residues in both doses. The estimated dietary risk assessment of imidacloprid and flonicamid residues (RQ <1) indicated that the risk is within the acceptable limit. In farmgate capsicum samples, residues of flonicamid (7 samples) and imidacloprid (11 samples) were detected. Market samples of capsicum products (powder, flakes and sauce) were not detected with residues of selected insecticides.

Residue behaviors, degradation, processing factors, and risk assessment of pesticides in citrus from field to product processing

Pesticide residues in citrus may cause health risks in related juice products, and bring much uncertainty during the processing procedures. In this study, based on the dispersive solid-phase extraction (d-SPE) and UPLC-MS/MS, the residual levels of ten analytes in citrus and its processed products were monitored. The results showed that dissipation of the pesticides followed the first-order kinetics and the half-lives in citrus varied greatly, ranging from 6.36 to 63.0 days. The terminal residues of the five pesticides at harvest time were <0.01-0.302 and <0.01-0.124 mg/kg in raw citrus and citrus flesh, respectively, all of which were lower than the corresponding maximum residue limits (MRLs) of 0.5-1 mg/kg. In the processing experiments, the residues of ten analytes in sterilized juice, concentrated juice, and citrus essential oil were in the range of <0.01 to 0.442 mg/kg, <0.01 to 1.16 mg/kg, and <0.01 to 44.0 mg/kg, respectively, and the corresponding processing factors (PFs) were 0.127-1.00, 0.023-3.06, and 0.006-39.2. Particularly, in citrus essential oil, the PFs of etoxazole, fluazinam, lufenuron and spirotetramat-keto-hydroxy were 1.68-39.2, exhibiting obvious enrichment effects. By integrating the residue data of the field trials and the PFs, the acute and chronic dietary risks of the target pesticides in citrus juice were 0.031-1.83 % and 0.002-2.51 %, respectively, which were far lower than 100 %, demonstrating no unacceptable risk to human health. This work provides basic data for the establishment of the MRLs and dietary exposure risk assessment for processed citrus products.

The Dissipation Behavior and Risk Assessment of Carbendazim Under Individual and Joint Applications on Peach (Amygdalus persica L.)

Dissipation, residue levels, and ingestion risks of carbendazim in peach (Amygdalus persica L.) were investigated with individual and joint applications in the present study. The dissipation kinetics of carbendazim, chlorpyrifos, prochloraz, and imidacloprid were evaluated by the first-order kinetics. When carbendazim was individually applied, the final residual concentration was 2.97 mg kg-1 and the half-life was 17.4 d. In the joint application of carbendazim with chlorpyrifos, prochloraz, and imidacloprid, the residual concentrations at 35 d after spraying were 7.16, 7.50, and 4.26 mg kg-1 and the half-lives were 30.8, 23.7, and 23.2 d, respectively, which showed an increase of 1.3-1.8 times compared with the single application of carbendazim. In addition, the effects of household processing of rinsing and peeling were investigated, and a high removal rate of 54.6% and 76.5% were found. Furthermore, the carbendazim ingestion risk assessment was conducted, which indicated that the acute health risk (aHI) and hazard quotient (HQ) of carbendazim were all within acceptable levels ranging from 21.7% to 40.9%. However, a higher ingestion risk of carbendazim was found under the joint application. This study provides some preliminary guidance for the joint application and risk assessment of carbendazim in peach, which is worth further investigation.

Interactions of anthelmintic veterinary drugs with the soil microbiota: Toxicity or enhanced biodegradation?

Anthelmintic (AH) compounds are used to control gastrointestinal nematodes (GINs) in livestock production. They are only partially metabolized in animals ending in animal excreta whose use as manures leads to AH dispersal in agricultural soils. Once in soil, AHs interact with soil microorganisms, with the outcome being either detrimental, or beneficial. We aimed to disentangle the mechanisms of these complex interactions. Two soils previously identified as « fast » or « slow», regarding the degradation of albendazole (ABZ), ivermectin (IVM), and eprinomectin (EPM), were subjected to repeated applications at two dose rates (1, 2 mg kg-1and 10, 20 mg kg-1). We hypothesized that this application scheme will lead to enhanced biodegradation in «fast » soils and accumulation and toxicity in «slow » soils. Repeated application of ABZ resulted in different transformation pathways in the two soils and a clear acceleration of its degradation in the «fast » soil only. In contrast residues of IVM and EPM accumulated in both soils. ABZ was the sole AH that induced a consistent reduction in the abundance of total fungi and crenarchaea. In addition, inhibition of nitrification and reduction in the abundance of ammonia-oxidizing bacteria (AOB) and archaea (AOA) by all AHs was observed, while commamox bacteria were less responsive. Amplicon sequencing analysis showed dose-depended shifts in the diversity of bacteria, fungi, and protists in response to AHs application. ABZ presented the most consistent effect on the abundance and diversity of most microbial groups. Our findings provide first evidence for the unexpected toxicity of AHs on key soil microbial groups that might have to be considered in a regulatory context.

Spontaneous symmetry breaking and localization in nonequilibrium steady states of interactive quantum systems

The time evolution of a physical system is generally described by a differential equation, which can be solved numerically by adopting a difference scheme with space-time discretization. This discretization, as a numerical artifact, results in accumulated errors during evolution and thus usually plays a negative role in simulations. In a quantum circuit, however, the "evolution time" is represented by the depth of the circuit layer, and thus is intrinsically discrete. Hence, the discretization-induced error therein is not a numerical artifact, but a physical observable effect responsible for remarkable nonequilibrium phenomena absent in conventional quantum dynamics. In this paper, we show that the combination of measurement feedback and temporal discretization can give rise to a new type of quantum dynamics. As physical consequences of this interactive quantum dynamics, a nonequilibrium steady state with spontaneous symmetry breaking is revealed in a zero-dimensional (single-qubit) system. A localization mechanism distinct from that in the well-established Anderson localization has also been proposed in a one-dimensional interactive quantum system.

The Dissipation Kinetics, Residue Level and Dietary Risk of Kresoxim-Methyl in Rosa roxburghii and Soil Based on the QuEChERS Method Coupled with LC-MS/MS

This study aimed to investigate the dissipation, residues and dietary assessment of kresoxim-methyl in the application of Rosa Roxburghii and soil field using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results show that kresoxim-methyl in R. roxburghii samples was extracted by acetonitrile and purified by ethyl enediamine-N-propylsilane (PSA), while kresoxim-methyl in soil samples was extracted by acetonitrile and purified by octadecylsilyl solid phase dispersant (C18). 0.1% formic acid (v/v)-water-methanol solution was used as the mobile phase, LC-MS/MS exhibited a good linearity in the range of 0.001-10 mg L-1. The recoveries of R. roxburghii and soil matrix were 82.48%-102.55%, and the relative standard deviation (RSD) were 1.13%-4.21%. The limit of detection (LOD) and quantification (LOQ) of kresoxim-methyl in R. roxburghii and soil samples was 0.50 and 0.60 µg kg-1, respectively. The dissipation dynamics of kresoxim-methyl in R. roxburghii and soil followed the first-order kinetics, with the half-life of 4.28 and 4.41 days, respectively. The terminal residual amount of kresoxim-methyl in R. roxburghii and soil samples was 0.003-1.764 and 0.007-2.091 mg kg-1, respectively. The dietary intake risk assessment indicates that a risk quotient (RQ) for kresoxim-methyl based on the national estimated daily intake (NEDI) of 0.1995 mg was 0.79%, suggesting that the use of kresoxim-methyl on R. roxburghii at recommended dosage was safe to consumers. This study provides the theoretical basis for guiding the rational use of kresoxim-methyl in the production of R. roxburghii.

Residue dynamics and dietary risk assessment of new formulation of novaluron and lambda cyhalothrin on tomato

Presence of residues on food commodities is major bottleneck of insecticide use under good agricultural practices (GAPs). The use of less persistent with two different mode of action insecticide is novel approach of getting maximum insect control without developing insecticide resistance. Novaluron, an insect growth disruptor and lambda cyhalothrin, a nerve poison has been used widely for the management of lepidopteran pests. Dissipation and consumer risk analysis studies were carried out on a new combination product of novaluron and lambda cyhalothrin are used for control insects of tomato at recommended standard dose of 71 + 14 g/ha and double dose of 142 + 28 g/ha of active ingredients. Extraction and cleanup of sample residues was done using QuEChERS technique and analyzed in GC-ECD. The residues of novaluron were dissipated within 10 to 15 days, and the residues of lambda cyhalothrin were at 7 to 10 days, both at the standard and double the standard dose, following a first order reaction kinetics. Analysis of risk and hazard quotient revealed that the test insecticides do not pose any dietary risk to consumer as TMDI < MPI and HQ < 1.