The dissipation and residue levels of thiamethoxam and its metabolite clothianidin in cowpea were investigated under field conditions. Samples of cowpea were analyzed using a QuEChERS technique with ...ultra-performance liquid chromatography tandem mass spectrometry. The recoveries were 86.5–118.9% for thiamethoxam and 75.6–104.1% for clothianidin, with the coefficient of variation of < 13%. The water dispersible granule formulation of thiamethoxam was applied on cowpea at 30 and 45 g active ingredient ha
−1
in accordance with good agricultural practice. The half-life of thiamethoxam in cowpea was 0.8–1.6 days. The cowpea samples were gathered at 3, 7, and 10 days after the last application, and the residues of thiamethoxam in cowpea were < 0.005–0.054 mg kg
−1
, while those of clothianidin were < 0.005–0.008 mg kg
−1
. The final residues of thiamethoxam and clothianidin were below the European Union (EU) maximum residue level (0.3 mg kg
−1
for thiamethoxam; 0.2 mg kg
−1
for clothianidin) in cowpea after a preharvest interval (PHI) of 7 days. This study provided basic data on the use and safety of thiamethoxam and clothianidin in cowpea to help the Chinese government formulate a maximum residue level for thiamethoxam in cowpea.
Forested catchments are an important part of the mercury (Hg) cycle and a link between the atmospheric and the aquatic environments. In this study, Hg input and output fluxes and its retention were ...investigated at subtropical forested catchments in southwest China. Significantly enhanced atmospheric Hg inputs were observed, and the contribution of litterfall Hg plays a more important role at these subtropical forested catchments. The ratios of Hg output fluxes from stream water to total input were 2.5% and 1.2% for
LGS and
TSP, which were markedly lower than those reported from Europe and North America. The current annual input Hg only accounted for 0.8 and 1.8 per mille to the Hg stored in the upper 90 cm of soil in
LGS and
TSP. These suggest that subtropical forested catchments are important for retention of atmospheric mercury deposition in southwest China.
The subtropical forested catchments are important for retention of atmospheric mercury deposition in southwest China.
A simple solvent microextraction method termed vortex-assisted liquid–liquid microextraction (VALLME) coupled with gas chromatography micro electron-capture detector (GC-μECD) has been developed and ...used for the pesticide residue analysis in water samples. In the VALLME method, aliquots of 30
μL toluene used as extraction solvent were directly injected into a 25
mL volumetric flask containing the water sample. The extraction solvent was dispersed into the water phase under vigorously shaking with the vortex. The parameters affecting the extraction efficiency of the proposed VALLME such as extraction solvent, vortex time, volumes of extraction solvent and salt addition were investigated. Under the optimum condition, enrichment factors (EFs) in a range of 835–1115 and limits of detection below 0.010
μg
L
−1 were obtained for the determination of target pesticides in water. The calculated calibration curves provide high levels of linearity yielding correlation coefficients (
r
2) greater than 0.9958 with the concentration level ranged from 0.05 to 2.5
μg
L
−1. Finally, the proposed method has been successfully applied to the determination of pesticides from real water samples and acceptable recoveries over the range of 72–106.3% were obtained.
Antimicrobial peptides (AMPs) from black solider flies (
, BSF) exhibiting broad-spectrum antimicrobial activity are the most promising green substitutes for preventing the infection of ...phytopathogenic fungi; therefore, AMPs have been a focal topic of research. Recently, many studies have focused on the antibacterial activities of BSF AMPs against animal pathogens; however, currently, their antifungal activities against phytopathogenic fungi remain unclear. In this study, 7 AMPs selected from 34 predicted AMPs based on BSF metagenomics were artificially synthesized. When conidia from the hemibiotrophic phytopathogenic fungi
and
were treated with the selected AMPs, three selected AMPs-CAD1, CAD5, and CAD7-showed high appressorium formation inhibited by lengthened germ tubes. Additionally, the MIC
concentrations of the inhibited appressorium formations were 40 μM, 43 μM, and 43 μM for M. oryzae, while 51 μM, 49 μM, and 44 μM were observed for
, respectively. A tandem hybrid AMP named CAD-Con comprising CAD1, CAD5, and CAD7 significantly enhanced antifungal activities, and the MIC
concentrations against
and
were 15 μM and 22 μM, respectively. In comparison with the wild type, they were both significantly reduced in terms of virulence when infection assays were performed using the treated conidia of
or
by CAD1, CAD5, CAD7, or CAD-Con. Meanwhile, their expression levels of CAD1, CAD5, and CAD7 could also be activated and significantly increased after the BSF larvae were treated with the conidia of
or
, respectively. To our knowledge, the antifungal activities of BSF AMPs against plant pathogenic fungi, which help us to seek potential AMPs with antifungal activities, provide proof of the effectiveness of green control strategies for crop production.
In this study, a microextraction method termed as ultrasound-assisted emulsification-microextraction (USAEME) has been developed for the extraction of organophosphorus pesticides (OPPs) in water and ...orange juice samples. In the USAEME method, aliquots of 50 μL chlorobenzene used as extraction solvent was added to 10 mL water sample in a conical glass centrifugal tube. Factors influencing the USAEME extraction efficiency such as sonication time, extraction solvent, extraction volume and salt addition were evaluated. Under the optimum conditions, enrichment factors ranged from 241 to 311, LOD varied from 5.3 to 10.0 ng/L and linearity with a coefficient of estimation (r²) varied from 0.9991 to 0.9998 in the concentration level range of 0.05-2.5 μg/L for the extraction of OPPs in water samples. Finally, the proposed USAEME method was used for the extraction of OPPs from water and orange juice. The recoveries were in the range of 80.0-110.0%, and the repeatability of the method expressed as RSD (n=3) varied between 1.6 and 13%. The USAEME method has the advantage of being easy to operate, low consumption of organic solvent and high extraction efficiency.
Using an intelligent plant protection machine for spraying herbicides at a real-time variable rate plays a key role in improving the utilization efficiency of herbicides and reducing environmental ...pollution. Spraying volume (SV) and nozzle size (NS) are key factors influencing droplet deposition and herbicide efficacy and safety. A three-way split-split plot design experiment was conducted in the winter wheat field, with SV 180 L·ha−1 and 150 L·ha−1 in the main plot, a turbo air induction nozzle TTI11004 and TTI11003 in the subplot, herbicide flucarbazone-Na 70% WG mixed with florasulam 50 g·L−1 SC as the recommended dose, and a 20% reduced dose in the sub-subplot. Droplet deposition and weed control efficacy treated by these three factors and their combination were evaluated. Results indicated that there was a significant influence of SV on droplet coverage and density, but no significant influence of NS and its interaction with SV. A droplet coverage and density of treatment at 180 L·ha−1 were both significantly higher than at 150 L·ha−1. The influence of SV and its interaction with NS on weed control efficacy were significant. The efficacy of treatment TTI11004 at SV 180 L·ha−1 was the highest but decreased when NS was switched to TTI11003 and the SV was decreased to 150 L·ha−1. There was no significant effect of all the treatments on winter wheat yield and its components, but the yield loss could be reduced by 2.36% when the herbicide input was reduced by 20%. We can conclude that herbicide input can be reduced by at least 20% using the intelligent machine while equipped with the right NS at the right SV, which would increase the safety of winter wheat production.
A new analytical method for the determination of organophosphorus pesticides in cereal samples was developed by combining dispersive SPE (d‐SPE) and salting‐out homogeneous liquid–liquid extraction ...(SHLLE). The pesticides were first extracted from cereal grains with acetonitrile, followed by d‐SPE cleanup. A 2 mL aliquot of the extract was then added to a centrifuge tube containing 9.2 mL water and 3.3 g NaCl for SHLLE. Analysis of the extract was carried out by gas chromatography coupled with flame photometric detection. The d‐SPE procedure effectively provides the necessary cleanup of the extract while SHLLE is used as an efficient concentration technique. Experimental parameters influencing the extraction efficiency including amounts of added water and salt were investigated. Recovery studies were carried out at three fortification levels, yielding recoveries in the range of 57.7–98.1% with the RSD from 3.7 to 10.9%. The reported limits of determination obtained from this study were 1 μg/kg, which is better than the conventional methods. In the analysis of 40 wheat and corn samples taken from Beijing suburbs, only two wheat samples have chlorpyrifos residue over the limits of determination.
Imidaclothiz is a novel and systemic neonicotinoid pesticide with excellent insecticidal efficacy. However, knowledge of its uptake, translocation, and biotransformation within plants is still ...largely unknown, restricting work on its accurate and comprehensive risk assessment. Here, we systematically investigated the behavior of imidaclothiz in three plant–water systems via hydroponic experiments. The results showed that imidaclothiz was readily taken up by plant roots and translocated upward, resulting in relative enrichment in leaves. The recoveries of imidaclothiz in plant–water systems decreased with increasing exposure time, and approximately 31.8–45.6% mass loss was measured at the end of exposure. Ultimately, imidaclothiz yielded five products in celery leaves, three products in lettuce leaves, and two products in radish leaves. Multiple metabolic reactions including hydroxylation, hydrolysis of nitrate ester, and methylation occurred within plants. This is the first report on the fate of imidaclothiz within plants and suggests increasing concerns about the risk assessment of imidaclothiz.
•Wheat fields in Beijing contained multiple pesticides among 37 analytes in 2018–2020.•Carbendazim and triazoles were frequently detected in the paired wheat and soil samples.•Historically used HCHs ...and DDTs were detected at high frequencies in wheat soil.•Four pesticides existed residue correlation between the paired wheat and soil samples.•Levels of 8 pesticides exceeded their MRLs, and all except one of their RQs were <1.
The co-occurrence of multiple pesticides in wheat fields adversely affects human health and the environment. Herein, 206 pairs of wheat and soil samples were collected from wheat fields in Beijing, China from 2018 to 2020. One or multiple pesticide residues were detected, and carbendazim (maximum: 38511.5 μg/kg) and tebuconazole (maximum: 45.4 μg/kg) had heavy occurrence in the wheat samples. Carbendazim, triazoles, and neonicotinoids were frequently detected in the soil samples. HCHs and DDTs were detected, with p,p’-DDE in 100.0% of the soil samples at a maximum concentration of 546.0 μg/kg in 2020. Concentrations of carbendazim, tebuconazole, hexaconazole, and cyhalothrin in the paired soil and wheat samples exhibited significant positive correlations. Pesticides that exceeded the maximum residue limits do not pose non-carcinogenic risks, with one exception. The results provide important references towards risk monitoring and control in wheat fields, as well as facilitating the scientific and reasonable use of these pesticides.
In order to study the dissipation rates and final residues of kresoxim-methyl in strawberry and soil, two independent filed trials were performed in Beijing China. The application rates are set at ...195 g of active gradient per hectare. A simple analytical method has been developed for the determination of kresoxim-methyl in strawberry and soil. Kresoxim-methyl residues were extracted with acetonitrile from strawberry and soil samples which is determined by gas chromatography coupled with mass spectrometry detection (GC–MSD). The recoveries of kresoxim-methyl in strawberry and soil were observed from 78.9 % to 104.5 % at fortification levels of 0.01–0.5 mg/kg with relative standard deviations of 4.3 %–7.3 %. The reported limits of detection were 0.05 and 0.01 mg/kg for strawberry and soil, respectively. The results showed that kresoxim-methyl dissipation in strawberry could be described as first-order equation with the half-life time of 6.24 and 6.91 days. 14 days later, the dissipation rate is 84.9 % and 83.3 %, respectively. The final residues of kresoxim-methly in the strawberry were in the range of 2.7–4.8 mg/kg at pre-harvest intervals of 1, 3, 5, 7 days which is below the Japan maximum residue limits (MRLs) standards (5 mg/kg in strawberry).
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