| Pesticides play an indispensable role in agricultural production,but traditional pesticides have caused a series of food safety and environmental pollution problems due to the shortcomings of using organic solvents,poor dispersibility,and low utilization.As a new and efficient pesticide product,nano-pesticide has broad prospects in improving pesticide bioavailability and ensuring food safety.In this paper,porous nano-silica particles were synthesized by the sol-gel method,and acetamiprid was loaded on the porous nano-silica particles by the impregnation method to obtain nano-pesticides.To determine the toxic effects of nano-pesticides on target organisms(tea aphids);use hydroponic tea seedlings to study the differences in absorption,transport and metabolic behavior of nano-pesticides and traditional chemical pesticides in tea plants;quantitative analysis was performed on acetamiprid and its main metabolites;non-target metabolomics analysis was used to analyze the differences in metabolites in tea plants under nano-pesticide and traditional pesticide stress.The specific research results are as follows:1.The sol-gel method was used to synthesize porous nano-silica particles.The optimal adsorption conditions were obtained by comparing the adsorption amount of acetamiprid by the silica carrier under different solvents,times and initial acetamiprid concentrations.The fitting process fits the pseudo-second-order kinetic model and the Freundlich adsorption isotherm model.The pesticide release of nano-pesticides under different release media and temperature was measured,and there was no obvious slow-release behavior of nano-pesticides.The insecticidal activity of nano-pesticides and common commercial pesticides on tea aphids was compared.The LC50 value of the nano-pesticide was 4.687 mg/L,and the commercial preparation was 14.080 mg/L.The absorption and metabolism of nano-pesticides and commercial pesticides in hydroponic tea seedlings were studied.The pesticide absorption time was set to 10 days and the excretion metabolism time was 20 days.The contents of acetamiprid and its main metabolite,dimethyl-acetamiprid,in different parts of tea trees were measured at different times.The results showed that at 14 and 21 days,the concentration of acetamiprid in the young leaves of tea seedlings in the commercial pesticide treatment group was lower than that in the nano-pesticide treatment group,and there were significant differences.At 30 d,the retention concentrations of acetamiprid in tea young leaves and old leaves of the two treatment groups were:commercial pesticide treatment group(21.89 μg/g and 22.12 μg/g),nano pesticide treatment group(17.00 μg/g and 17.34 μg/g);the residual concentrations of dimethyl-acetamiprid are: commercial pesticide treatment group(1.51 μg/g and 1.21μg/g),nano pesticide treatment group(1.27 μg/g and 1.12 μg/g).The retention of acetamiprid and desmethyl acetamiprid in the nano pesticide treatment group was lower than that in the commercial pesticide treatment group.3.The non-targeted metabolomics method was used to analyze the changes of metabolites in the young leaves of tea seedlings under the stress of nano-pesticides and commercial pesticides.The number of differential metabolites(P <0.05 and VIP>1)identified between the nano-pesticide treatment group and the commercial preparation treatment group by LC-MS negative ion mode were: 196(2 h),200(7 d),207(21 d),201(30 d),and the number of differential metabolites(P < 0.05 and VIP > 1)were: 294(2 h),356(7 d),and 286(30 d)when detected in positive ion mode.Preliminary identification by reference,some of the differential compounds are:organic acids,amino acids,alkaloids,flavonoid glycosides,sugars,proanthocyanidins,theaflavins,catechins,esters. |
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