Concentrations Of Thiamethoxam Research Articles

An Aptamer Sensor Based on Alendronic Acid-Modified Upconversion Nanoparticles Combined with Magnetic Separation for Rapid and Sensitive Detection of Thiamethoxam.

The widespread use of thiamethoxam has led to pesticide residues that have sparked global concerns regarding ecological and human health risks. A pressing requirement exists for a detection method that is both swift and sensitive. Herein, we introduced an innovative fluorescence biosensor constructed from alendronic acid (ADA)-modified upconversion nanoparticles (UCNPs) linked with magnetic nanoparticles (MNPs) via aptamer recognition for the detection of thiamethoxam. Through base pairing, thiamethoxam-specific aptamer-functionalized MNPs (apt-MNPs) were integrated with complementary DNA-functionalized UCNPs (cDNA-UCNPs) to create the MNPs@UCNPs fluorescence biosensor. Thiamethoxam specifically attached to apt-MNPs, leading to their separation from cDNA-UCNPs, which in turn led to a reduction in fluorescence intensity at 544 nm following separation by an external magnetic field. The change in fluorescence intensity (ΔI) was directly correlated with the concentration of thiamethoxam, enabling the quantitative analysis of the pesticide. With optimized detection parameters, the biosensor was capable of quantifying thiamethoxam within a concentration span of 0.4-102.4 ng·mL-1, and it achieved a detection limit as minute as 0.08 ng·mL-1. Moreover, leveraging the swift magnetic concentration properties of MNPs, the assay duration could be abbreviated to 25 min. The research exhibited a swift and precise sensing platform that yielded promising results in samples of cucumber, cabbage, and apple.

Maternal neonicotinoid pesticide exposure impairs glucose metabolism by deteriorating brown fat thermogenesis.

Neonicotinoids (NEOs) are well-designed highly selective pesticides that target nicotinic acetylcholine receptors. However, their extensive use, accumulation, and biomagnification pose significant risks to humans. Increasing evidence has suggested that NEOs may affect glucose homeostasis, but little research has linked NEOs exposure to gestational diabetes mellitus (GDM), which is the most common disease in pregnancy. We here aimed to investigate the association between NEOs exposure and GDM occurrence. 100 pregnant women who completed a 75 g oral glucose tolerance test (OGTT) at 24-28 weeks of gestation were enrolled. Urinary concentrations of seven widely used NEOs were quantified using ultra-high performance liquid chromatography multiple reaction monitoring mass spectrometry (UHPLC-MRM-MS/MS). Correlation analysis revealed the associations between NEOs concentrations and glucose homeostasis parameters. The toxic effects of thiamethoxam (TMX) and clothianidin (CLO) were assessed using pregnant mice, and the potential mechanism in impairing glucose disposition regarding brown adipose tissue (BAT) thermogenesis has been elucidated. Among the 100 urine samples, 88 % were contaminated by NEOs with concentrations ranging from 2.50 to 491.34 nmol/L. TMX and CLO were the most frequently detected NEOs, highly detected in women with GDM. Moreover, we found statistically significant associations between TMX concentrations and 1hBG, and 2hBG. Exposure to mixed NEOs during gestation resulted in elevated glucose levels and impaired insulin sensitivity in normal pregnant and GDM mice models. In addition, we found the metabolic disorders induced by NEOs were linked to the deterioration of BAT thermogenesis in vivo. In general, we demonstrated that prenatal exposures to NEOs were associated with an increased risk of GDM by deteriorating the thermogenic capacity of BAT.

Urinary neonicotinoid exposure and its association with hypertension and dyslipidemia among the elderly: A cross-sectional study in Shenzhen, China.

In recent years, neonicotinoids (NEOs) as a new type of insecticide have been increasingly used worldwide, causing significant impacts on human health. This study collected urine samples from 1147 elderly individuals (including 714 in the control group and 433 in the hypertension group) in Shenzhen, China, and detected the concentrations of six types of NEOs and four metabolites of NEOs (mNEOs). The aim of this study is to investigate the association between NEOs exposure and hypertension and dyslipidemia. After measurement, we find that the lowest detection rate (DR) among NEOs is imidacloprid (IMI), at only 39.3%. The NEO with the highest urine median concentration is dinotefuran (DIN) (1.31μg/L), while the mNEO with the highest median concentration is DM-ACE (2.74μg/L). Through univariate analysis, we found that DM-THM may promote the development of hypertension, while logistic regression indicated that IMI-OF could be a risk factor for hypertension. As prototypes of these two metabolites, thiamethoxam (THM) and IMI may also be risk factors for hypertension. Linear regression analysis revealed a negative correlation between the concentration of thiamethoxam (THD) and low-density lipoprotein (LDL) level, while DIN was positively correlated with triglyceride (TG) level and negatively correlated with high-density lipoprotein (HDL) level. Mediation effect analysis showed that THD may influence the risk of hypertension in the elderly by affecting LDL level. Based on this study, we believe that exposure to NEOs may increase the risk of hypertension in the elderly population.

Effects of sublethal concentration of thiamethoxam formulation on the wild stingless bee, Partamona helleri Friese (Hymenoptera: Apidae): Histopathology, oxidative stress and behavioral changes

Bees are pollinators of native and cultivated plants around the world. However, several factors are contributing to the decrease in their populations in recent years, with emphasis on the increasing use of insecticides in agriculture. Thiamethoxam is a neonicotinoid neurotoxicant, which binds to nicotinic acetylcholine receptors, causing hyperexcitation, paralysis and death of insects. Although thiamethoxam's target is the nervous system, it can affect other organs through ingestion, such as the midgut, affecting non-target insects such as bees. Partamona helleri Friese (Hymenoptera: Apidae) is a stingless bee, pollinator of several native and cultivated botanical families, and can be exposed to sublethal concentrations of thiamethoxam. This study evaluated the side effects of chronic oral exposure to thiamethoxam on the midgut, oxidative stress and behavior of P. helleri workers. The bees were exposed orally, for 7 days, to the approximate sublethal concentration of thiamethoxam found in pollen grains (0.09 ng/g). The results demonstrated changes in the midgut epithelium of workers treated with thiamethoxam, such as cytoplasmic vacuolization, cellular protrusions, increased apocrine transfer, mitochondrial damage, decreased proteins and neutral polysaccharides and the presence of cells undergoing autophagy and apoptosis. Sublethal concentration of thiamethoxam also induced oxidative stress, evidenced by changes in the activities of detoxification enzymes and antioxidant markers. Finally, thiamethoxam affects the bee's behavior, driving the distance covered and walking speed of this insect. The results indicate that the exposure of P. helleri workers to sublethal concentration of thiamethoxam have negative impacts upon midgut morphology and physiology and behavioral traits.

Dual trace detection of hazardous substances by aptamer-functionalized gold nanofilms based on surface-enhanced Raman spectroscopy

This work proposes the application of multi-residue Surface-enhanced Raman spectroscopy (SERS) detection based on an internal standard and aptamer-functionalized gold nanofilms. First, two types of complementary DNA (cDNA) are fixed on the self-assembled monolayer of a halide ion-regulated nano-membrane through gold-sulfur bonds. Then, two signal probe molecules are prepared and modified. The aptamer specifically binds to cDNA, generating SERS signals. Detection of the target analytes is achieved by measuring the Raman intensity and using the internal standard method. The results show that the concentrations of thiamethoxam and dichlorodiphenyltrichloroethane (DDT) at 10-12 M can be effectively measured under optimal experimental conditions. The Raman intensity exhibits a linear relationship at the shifts of 1085 cm-1 for 4-mercaptopyridine (4-MPY) and 1583 cm-1 and 2223 cm-1 for 4-mercaptobenzoic acid (4-MBN). When applied to the detection of thiacloprid in actual lake water samples, the results show no significant difference compared to the standard.

A practical and theoretical study of the pesticide thiamethoxam on activated charcoal derived from Iraqi date seeds and Koura clay as good absorbents

In this study, activated charcoal extracted from Iraqi date seeds was used to study the effective removal of liquid thiamethoxam pesticide residues. Using Karwa clay to increase the adsorption capacity of thiamethoxam, activated charcoal made from Iraqi date kernel waste was produced using two different processes: chemical catalysis and physical catalysis treated with a phosphoric acid solution (5M). Several elements, including thiamethoxam concentration, mixing duration, contact time, amount of activated charcoal temperature, and pH of the medium, have been studied to influence thiamethoxam removal efficiency. The results showed that the maximum adsorption dose was 0.05 g/L, the dye concentration was 100 mg/L, and the adsorption duration for activated charcoal was 2.5 hours, which is the ideal condition for removal efficiency of 10-63%, while the adsorption duration for activated charcoal was 2.5 hours, which is the ideal condition for removal efficiency. 10-63%. The adsorption time on the Kora clay was 3.5 hours, which is the ideal condition for removal efficiency of 10-74%. Adsorption equilibrium was performed using Freundlich, Temkin, Harkins-Jura, Dupin, Elovitch, and Langmuir, and the results on the activated charcoal surface showed that the Harkins-Jura model with R2 values of 0.987 and the results on the kura clay surface showed that the Langmuir model with R2 values of 0.157 showed agreement. Best with experimental data for adsorption. According to thermodynamic analysis, the pesticide is endothermic, spontaneous, and indicates increased unpredictability at the adsorbent interface. It also indicates the pHZpc of the negatively charged carbon surface at pH = 2.0. Two pseudo-first-order models and two pseudo-second-order models were included in the kinetic analysis. The results indicate that the pseudo-second order model with R2 > 0.9661 on the activated charcoal surface fits the experimental data best. The results also indicate that the pseudo-second order model with R2 > 1 on the Kura clay surface fits the experimental data better. Density function theory, or DFT, was used to simulate thiamethoxam and help us determine the origin of the reaction.

Impact of Sublethal Insecticides Exposure on Vespa magnifica: Insights from Physiological and Transcriptomic Analyses.

Insecticides are widely used to boost crop yields, but their effects on non-target insects like Vespa magnifica are still poorly understood. Despite its ecological and economic significance, Vespa magnifica has been largely neglected in risk assessments. This study employed physiological, biochemical, and transcriptomic analyses to investigate the impact of sublethal concentrations of thiamethoxam, avermectin, chlorfenapyr, and β-cypermethrin on Vespa magnifica. Although larval survival rates remained unchanged, both pupation and fledge rates were significantly reduced. Enzymatic assays indicated an upregulation of superoxide dismutase and catalase activity alongside a suppression of peroxidase under insecticide stress. Transcriptomic analysis revealed increased adenosine triphosphate-related processes and mitochondrial electron transport activity, suggesting elevated energy expenditure to counter insecticide exposure, potentially impairing essential functions like flight, hunting, and immune response. The enrichment of pathways such as glycolysis, hypoxia-inducible factor signaling, and cholinergic synaptic metabolism under insecticide stress highlights the complexity of the molecular response with notable effects on learning, memory, and detoxification processes. These findings underscore the broader ecological risks of insecticide exposure to non-target insects and highlight the need for further research into the long-term effects of newer insecticides along with the development of strategies to safeguard beneficial insect populations.

Sublethal exposure to thiamethoxam and pyraclostrobin affects the midgut and Malpighian tubules of the stingless bee Frieseomelitta varia (Hymenoptera: Apidae: Meliponini).

The stingless bee Frieseomelitta varia Lepeletier 1836 (Hymenoptera: Apidae) is an essential pollinator in natural and agricultural ecosystems in the Neotropical region. However, these bees may be exposed to pesticides during foraging, which can affect both individuals and their colonies. One example comes from the use of pyraclostrobin (a fungicide) and thiamethoxam (an insecticide) for pest control in pepper crops, which F. varia visits. This study aimed to evaluate the isolated and combined sublethal effects of thiamethoxam (TMX) (0.000543 ng a.i./µL) and pyraclostrobin (PYR) (1.5 ng i.a./µL) on the morphology of the midgut and Malpighian tubules of F. varia workers. Results showed that both pesticides, regardless of the exposure time (through feeding during 48 h or 96 h), disturbed the morphology of the analyzed organs. Specifically, F. varia exposed orally to sublethal concentrations of thiamethoxam and pyraclostrobin, either alone or in combination, exhibited a higher rate of damage to the midgut (e.g., vacuolization, apocrine secretion, and cellular elimination) compared to the bees in the control groups, both after 48 h and 96 h of exposure. In Malpighian tubules, vacuolation is the only damage present. As the observed morphological alterations likely compromise the excretion and absorption functions, exposure to pyraclostrobin and thiamethoxam may lead to disturbances at both the individual and colony levels. These results highlight the urgent need for a future reassessment of the safety of fungicides and insecticides regarding their potential effects on bee populations.

Influence of Pesticide Application Method, Timing, and Rate on Contamination of Nectar with Systemic and Nonsystemic Pesticides.

Exposure to pesticides is one potential factor contributing to the recent loss of pollinators and pollinator diversity. Few studies have specifically focused on the relationship between pesticide management during ornamental plant production and contamination of nectar. We evaluated contamination of nectar in Salvia 'Indigo Spires' (Salvia longispicata M. Martens & Galeotti × S. farinacea Benth.) associated with applications of the systemic insecticide thiamethoxam, and the nonsystemic fungicides boscalid and pyraclostrobin. Applications were made at the labeled rates for the commercially available products, and we compared the influence of application method (drench vs. spray), timing (relative to flowering), and rate (low vs. high) for each pesticide. Nectar was sampled using 50-µL microcapillary tubes and analyzed by liquid chromatography-tandem mass spectrometry. The results indicate that concentrations from the spray application resulted in the least contamination of nectar with the systemic thiamethoxam, with lower concentrations occurring when thiamethoxam was applied before blooming at the lowest rate. Concentrations of thiamethoxam and its metabolite clothianidin were detected in nectar in all treatments (regardless of the method, timing, or rate of application), and ranged from 3.6 ± 0.5 ng/mL (spray-applied before blooming, low rate) to 1720.0 ± 80.9 ng/mL (drench-applied after blooming, high rate). Residues of clothianidin in nectar ranged from below quantification limits (spray-applied before blooming, low rate) to 81.2 ± 4.6 ng/mL (drench-applied after blooming, high rate). Drench applications resulted in the highest levels of nectar contamination with thiamethoxam, and exceeded published median lethal concentrations (LC50s/median lethal doses for native bees and/or honeybees in all cases). Spray treatments resulted in nectar concentrations exceeding published LC50s for some bee species. In comparison, all nonsystemic treatments resulted in concentrations much lower than the published no-observable-effect doses and sublethal toxicity values, indicating low risks of toxicity. Environ Toxicol Chem 2024;43:2616-2627. © 2024 SETAC.

Milkweed in agricultural field margins - A neonicotinoid exposure route for pollinators at multiple life stages

Neonicotinoid insecticides move from targeted crops to wildflowers located in adjacent field margins, acting as a potential exposure source for wild pollinators and insect species of conservation concern, including monarch butterflies. Monarchs rely on milkweed over multiple life stages, including as a host plant for eggs and a food source for both larvae (leaves) and adults (flowers). Milkweeds, which are closely associated with field margins, can contain neonicotinoid residues, but previous assessments are constrained to a single plant tissue type. In 2017 and 2018, we sampled milkweeds from 95 field margins adjacent to crop fields (corn, soybean, hay, wheat, and barley) in agricultural landscapes of eastern Ontario, Canada. Milkweeds were sampled during the flower blooming period and leaves and flower tissues were analysed. The neonicotinoids acetamiprid, clothianidin, thiamethoxam, and thiacloprid were detected. Maximum concentrations in leaf samples included 10.30 ng/g of clothianidin in 2017, and 24.4 ng/g of thiamethoxam in 2018. Clothianidin and thiamethoxam percent detections in flowers (72 % and 61 %, respectively) were significantly higher than detections in leaves (24 % and 31 %, respectively). Thiamethoxam concentrations were significantly higher in paired flower samples than leaf samples (median 0.33 ng/g vs <0.07 ng/g) while clothianidin concentrations also trended higher in flowers (median 0.18–0.55 ng/g vs <0.18 ng/g). Only thiamethoxam showed significant differences between years, and we found no effect of crop type, with hay, soybean and corn fields all yielding 50–56 % detections in leaves. We found significantly higher concentrations in older milkweed flowers than young flowers or leaves (medians 0.87 ng/g vs <0.18 ng/g and 0.45 ng/g vs <0.07 ng/g for clothianidin and thiamethoxam, respectively). Our results highlight the importance of considering variation in milkweed tissue type and age of flowers in neonicotinoid exposure risk assessments. Efforts to increase milkweed availability in agricultural landscapes should consider how exposure to neonicotinoids can be mitigated.

Exposure to neonicotinoid pesticides induces physiological disorders and affects color performance and foraging behavior in goldfish.

We investigated the effects of neonicotinoid pesticides (NEOs) on the spontaneous swimming and foraging behavior, as well as the morphological and physiological changes of goldfish. Most fish reared in thiamethoxam (THM)-sprayed rice fields showed the scales easily peeled off, and increased ascites. Some individuals showed decreased bio-defense activity and low plasma Ca2+. Similar changes were found in the exposure test to THM (1.0 and 20.0 μg/L) and dinotefuran (1.2 and 23.5 μg/L). Next, the effects of a low concentration of THM (1.0 μg/L) on the spontaneous swimming and foraging behavior of fish were examined. Fish exposed to THM for 1 week became restless and had increased the swimming performance, especially under natural light, white LED lighting and blue LED lighting. Goldfish exposed to THM had also increased intake of shiny white beads under green LED illumination. These results indicate that the exposure to NEO, even for a short period and at low levels, not only suppressed bio-defense activities and metabolic abnormalities, but also stress response, the swimming and foraging behavior of the fish are likely to be significantly suffered.

Selection of Aphis craccivora (Hemiptera: Aphididae) for Resistance to Thiamethoxam Insecticide Under Laboratory Conditions

Abstract The cowpea aphid, Aphis craccivora Koch (Hemiptera: Aphididae), is a polyphagous pest that causes yield losses in a variety of crops worldwide. Its management relies mainly on the use of chemical insecticides. This study followed the development of resistance to thiamethoxam in A. craccivora under laboratory conditions for 24 generations. The initial median lethal concentration (LC50) of thiamethoxam in a susceptible laboratory population of A. craccivora was 2.62 ppm. Exposure of surviving aphids in each generation to thiamethoxam caused an increase in the LC50 with each successive generation. After 24 generations, the LC50 had increased to 225.83 ppm, an 86.2-fold increase over the initial LC50. Resistance, as indicated by the increasing LC50, appeared as early as the second generation with a 1.4-fold increase over the initial generation. By the 14th generation, the LC50 had increased by 29-fold, and by the 16th generation, it had quickly increased by 69.4-fold. Our results indicate that A. craccivora populations repeatedly exposed to thiamethoxam in a cropping system can lead to rapid development of resistance to the insecticide. Any overuse or other misuse of the pesticide may lead to an even more rapid development of high levels of resistance to thiamethoxam within a short period of time. Elevated levels of the detoxifying enzymes, carboxylesterase, glutathione-S-transferase, and mixed function oxidases, in aphids exhibiting resistance as compared with the initial susceptible population indicated that the detoxifying enzymes, especially the carboxylesterases, are likely involved in facilitating the development of resistance to thiamethoxam in A. craccivora.

Insights into the uptake, translocation, and accumulation dynamics of cyantraniliprole and thiamethoxam seed coating pesticides in maize plants.

Seed coating with pesticides is used extensively for the protection of both seeds and plants against pests. In this study, the uptake and transport of seed-coating pesticides (insecticides), including cyantraniliprole (CYN) and thiamethoxam (THX), were investigated. The translocation of these pesticides from the soil to the plant and their accumulation in different plant parts were also calculated. After sowing the seeds with seed coating pesticides, soil and plant samples were taken across the study area. These samples were extracted and analyzed in liquid chromatography with tandem mass spectrometry (LC-MS/MS). CYN and THX were used in maize plants for the first time to observe soil degradation kinetics, and CYN showed a higher half-life than THX in soil. Both pesticides have been taken up by the corn maize plant and transferred and accumulated to the upper parts of the plant. Although the THX concentration was between 2.240 and 0.003mg/kg in the root, between 3.360 and 0.085mg/kg in the stem, it was between 0.277 and 3.980mg/kg in the leaf, whereas CYN was detected at higher concentrations. The concentration of CYN was 1.472mg/ kg and 0.079mg/kg in the roots and stems of the maize plant, respectively. However, the bioconcentration factor (BCF) indicates the soil-to-plant accumulation of CYN from 28 to 34.6 and that of 12.5 to 4567.1 for THX on different sampling days. The translocation factor (TFstem) represents the ratio of pesticides absorbed from the stem and transported to the roots. For CYN, TFstem ranges from 3.6 to 20.5, while for THX, it varies between 1.5 and 26.8, indicating a higher translocation rate for THX. The ratio of leaf to root concentration are 3.6 to 20.5 for CYN and 1.8 to 87.7 for THX, demonstrating effective translocation for both pesticides. The TF values for both pesticides are above 1, signifying successful root-to-stem-to-leaf movement. Notably, THX exhibits a notably higher transport rate compared to CYN.

The Effect of Different Thiamethoxam Concentrations on Riptortus pedestris Development and Fecundity.

The stink bug, Riptortus pedestris (Fabricius) (Hemiptera: Alydidae), is a highly destructive pest that significantly damages legume crops in East and South Asia. Neonicotinoid insecticides containing thiamethoxam are widely used to control R. pedestris in soybean fields. However, the current knowledge on the impact of different thiamethoxam concentrations on R. pedestris growth and reproduction is lacking and insufficient. The present study investigated the effects of thiamethoxam on the biological traits of R. pedestris after treatment with LC10 (19.8 mg/L), LC20 (31.6 mg/L), LC30 (44.2 mg/L), LC40 (58.9 mg/L), and LC50 (77.0 mg/L) concentrations. These five thiamethoxam concentrations (LC10~LC50) reduced adult longevity and fecundity in the F1 generation females. Thiamethoxam treatment also significantly decreased the population trend index, intrinsic rate of increase, net reproductive rate, gross reproductive rate, and finite rate of increase and increased the mean generation time. These results show that thiamethoxam hinders and suppresses the development and growth of the F1 population of R. pedestris. Thiamethoxam is recommended for spray control during peak adult emergence, as it not only has a controlling effect on the parental generation but also a negative impact on the F1 generations.

Thiamethoxam Residuality in Papaya Plant and Fruit (Carica papaya Linnaeus) Cultivated in Rotation with Watermelon (Citrullus lanatus)

There is evidence of the high use of the neonicotinoid insecticide thiamethoxam, in tropical crops, for its effectiveness in the control of soil and plant pests. The objective of this study was to know the residuality and concentration of thiamethoxam in the papaya agroecosystem, in the main papaya fruit producing zone in the central area of the Gulf of Mexico. It was carried out during a papaya growing cycle with watermelon rotation; the taking of samples was according to the technique established by the NOM -AA-103-1988 for leaves and for fruit the NMX -FF-041- 1996 by the method of quartering in papaya and watermelon, the samples were analyzed with a HPLC-UV, the data obtained were statistically analyzed by parametric and non-parametric Kruskal- Wallis tests. The presence of thiamethoxam was found in papaya and watermelon cultivation plants, the concentrations in papaya leaves reported a maximum value of 0.29 mg/kg, while for the leaves of the watermelon rotation fruit it was 0.15 mg/kg. In papaya fruit, thiamethoxam concentrations are within a range of 0.24 to 0.32 mg/kg. The concentrations and residuality of thiamethoxam mainly exceed the maximum tolerance and residuality limits of the EFSA and FAO.

Modeling temperature-dependent life-cycle toxicity of thiamethoxam in Chironomus riparius using a DEB-TKTD model

The neonicotinoid insecticide thiamethoxam (TMX) is widely used to protect crops against insect pests. Despite some desirable properties such as its low toxicity to birds and mammals, concerns have been raised about its toxicity to non-target arthropods, including freshwater insects like chironomids. Whereas multiple studies have investigated chronic effects of neonicotinoids in chironomid larvae at standardized laboratory conditions, a better understanding of their chronic toxicity under variable temperatures and exposure is needed for coherent extrapolation from the laboratory to the field. Here, we developed a quantitative mechanistic effect model for Chironomus riparius, to simulate the species’ life history under dynamic temperatures and exposure concentrations of TMX. Laboratory experiments at four different temperatures (12, 15, 20, 23 °C) and TMX concentrations between 4 and 51 µg/L were used to calibrate the model. Observed concentration-dependent effects of TMX in C. riparius included slower growth, later emergence, and higher mortality rates with increasing concentrations. Furthermore, besides a typical accelerating effect on the organisms’ growth and development, higher temperatures further increased the effects associated with TMX. With some data-informed modeling decisions, most prominently the inclusion of a size dependence that makes larger animals more sensitive to TMX, the model was parametrized to convincingly reproduce the data. Experiments at both a constant (20 °C) and a dynamically increasing temperature (15–23 °C) with pulsed exposure were used to validate the model. Finally, the model was used to simulate realistic exposure conditions using two reference exposure scenarios measured in Missouri and Nebraska, utilizing a moving time window (MTW) and either a constant temperature (20 °C) or the measured temperature profiles belonging to each respective scenario. Minimum exposure multiplication factors leading to a 10% effect (EP10) in the survival at pupation, i.e., the most sensitive endpoint found in this study, were 25.67 and 21.87 for the Missouri scenario and 38.58 and 44.64 for the Nebraska scenario, when using the respective temperature assumptions. While the results illustrate that the use of real temperature scenarios does not systematically modify the EPx in the same direction (making it either more or less conservative when used as a risk indicator), the advantage of this approach is that it increases the realism and thus reduces the uncertainty associated with the model predictions.

Three-Dimensional Electrode-Enhanced Ozone Catalytic Oxidation for Thiamethoxam Wastewater Treatment: Performance, Kinetics, and Pathway

Thiamethoxam is a second-generation neonicotinoid pesticide that is used worldwide. In this study, a three-dimensional electrode-enhanced ozone catalytic oxidation system (3DE-GAC-O3) was constructed to pretreat thiamethoxam wastewater, with granular active carbon as the particle electrode. The effects of catalytic oxidation time, current density, ozone concentration, initial thiamethoxam concentration, pH, and particle electrode dosage on thiamethoxam degradation were investigated. A response surface method based on the Box–Behnken design was employed to optimize the 3DE-GAC-O3 process. The results revealed that the 3DE-GAC-O3 system exhibited higher efficiency compared with the 3D electrode method, ozone catalytic oxidation, or 2DE-O3. The optimal operating conditions included a particle electrode dosage, ozone concentration, current density, solution pH, catalytic oxidation time, and initial thiamethoxam concentration of 18 g/dm3, 12 g/h, 25 A/m2, 7, 300 min, and 500 mg/dm3, respectively. The corresponding chemical oxygen demand removal rate reached 93.86 ± 0.95%. Thiamethoxam degradation followed a second-order reaction kinetics equation, and the rate constant decreased with increasing the initial thiamethoxam concentration. Free-radical quenching experiments indicated that both O2∙− and ∙OH were present within the 3DE-GAC-O3 system, with ∙OH being the predominant species. A GC-MS analysis revealed the formation of several intermediate products, which were characterized based on the mass fragmentation pattern. Additionally, a probable degradation pathway for thiamethoxam was proposed. Therefore, 3DE-GAC-O3 is an efficient method for the pretreatment of thiamethoxam wastewater.

Impact assessment of thiamethoxam on microbial and enzymatic activity in mango rhizosphere

Thiamethoxam is a globally used neonicotinoid insecticide in mango ecosystem which can cause hazardous impact on soil environment. The current study was carried out to assess the impact of 0.2 (T1/treament) and 2.0 g kg−1 (T2) concentrations of thiamethoxam on mango rhizospheric microbial community, enzyme activity along with its degradation. Indigenous microflora degraded thiamethoxam from 5.62 to 41.17 mg kg−1 at 0 day to 0.60 and 2.10 mg kg−1 in soil after 60 days of application of 0.2 and 2.0 g kg−1 doses, respectively. Thiamethoxam dissipated via pseudo first-order kinetics with t1/2 (half-life) values (23.00 and 14.00) days and K values (1.99–17.14) and (21.42–183.6) at T1 and T2, respectively. At bacterial count of 5.5 × 107 in soil, fluorescein diacetate (FDA) and dehydrogenase (DHA) showed that there was no change occurred in control soil after 60 days, while in thiamethoxam treated soil DHA was marginally increased from 0.164 to 0.168 µg g−1 and from 0.155 to 0.157 µg g−1 at lower and higher doses, respectively. While, FDA values were slightly decreased from 0.761 to 0.717 µg g−1 at T1 but no significant change was observed in T2. However, changes in fungal population were not significant but increase in bacterial population with the degradation of thiamethoxam was observed, which indicated the presence of thiamethoxam degrading beneficial bacteria in mango rhizosphere soil.

Thiamethoxam-Induced Intergenerational Sublethal Effects on the Life History and Feeding Behavior of Rhopalosiphum padi

Thiamethoxam, a second-generation neonicotinoid insecticide is widely used for controlling sap-sucking insect pests including Rhopalosiphum padi. The current study aimed to investigate the life-history parameters and feeding behavior of R. padi following treatments with sublethal concentrations of thiamethoxam. The lethal concentration 50 (LC50) value of thiamethoxam against adult R. padi was 11.458 mg L−1 after 48 h exposure. The sublethal concentrations of thiamethoxam (LC5 and LC10) significantly decreased the adult longevity, fecundity, and reproductive days in the directly exposed aphids (F0 generation). In the progeny R. padi (F1), the developmental durations and total prereproductive period (TPRP) were decreased while the adult longevity, fecundity, and reproductive days (RPd) were increased at both thiamethoxam concentrations. The demographic parameters including the net reproductive rate (R0), intrinsic rate of increase (r), and finite rate of increase (λ) were prolonged only at the LC5 of thiamethoxam. The EPG results indicated that the sublethal concentrations of thiamethoxam increases the total duration of non-probing (Np) while reducing the total duration of E2 in directly exposed aphids (F0). Interestingly, the E2 were significantly increased in the progeny generation (F1) descending from previously exposed parental aphids (F0). Overall, this study showed that thiamethoxam exhibited high toxicity against directly exposed individuals (F0), while inducing intergenerational hormetic effects on the progeny generation (F1) of R. padi. These findings provided crucial details about thiamethoxam-induced hormetic effects that might be useful in managing resurgences of this key pest.

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.