Construction And Performance Study Of Functionalized Pesticide Formulation Based On Cellulose/Calcium Carbonate As Carrier

Conventional pesticides formulations are easy to be lost in the environment through drift,rolling,volatilization,and sedimentation after being sprayed into the field.In order to arrive at ideal control effect,multiple and repeated pesticides need to be applied,resulting in the accumulation of large amounts of pesticides in the environment,causing potential environmental pollution and health risks.Environmentally responsive pesticide controlled release formulations can respond to biotic or abiotic stimuli and release pesticides on demand,thus having a long effective duration,good control effect,low toxicity to non-target organisms.Therefore,it is of great significance to improve the effective utilization of pesticides and reduce environmental risks.This paper addresses the current problems of conventional pesticide formulations with high application and low efficacy,high toxicity to non-target organisms,and high environmental risk,and explores the preparation of functionalized pesticide carriers from natural materials,cellulose and calcium carbonate,to carry out research on new environmentally friendly pesticide formulations.In order to provide theoretical guidance for the development of pesticide formulations and to provide reference solutions for improving the compatibility of pesticides with the environment.The following results were achieved in this thesis:(1)A new formulation of fipronil based on modified cellulose can improve the effective utilization rate of pesticide and significantly reduce the acute contact toxicity to honey bees:By chemical cross-linking method,ethylenediamine was grafted onto carboxymethyl cellulose skeleton to prepare aminated carboxymethyl cellulose carriers.Fipronil,a highly toxic phenyl pyrazole insecticide for honey bees,was encapsulated in a modified cellulose carrier by solvent volatilization to make a new environmentally friendly and safe formulation ACMCF.ACMCF has good wetting and spreading properties and high foliage retention on cucumber and peanut leaves,and its acute contact toxicity to Apis mellifera L.(LD₅₀=0.151?g a.i./bee)is much lower than that of fipronil EW(LD₅₀=0.00204?g a.i./bee),and the stomach toxicity against Plutellidae xylostella was slightly worse than that of fipronil EW.In addition,ACMCF was less mobile in soil than fipronil EW,indicating that the potential hazard of fipronil to aquatic organisms could be reduced.Thus,functional carriers based on modified cellulose can not only improve the effective utilization of pesticides,but also reduce the toxicity to non-target organisms,demonstrating potential application prospects.(2)Temperature-responsive chlorpyrifos microcapsules with hexadecane as a temperature-controlled trigger for sustained pest control and reduced toxicity to aquatic organisms:Based on the relationship between temperature and pest growth and development period,temperature-responsive microcapsules loaded with chlopyrifos were prepared by interfacial polymerization with n-hexadecane as the core.The loading rate and particle size distribution of the microcapsules were investigated,the pesticide release performance and the control effect against Plutellidae xylostella at different temperatures were examined,and acute toxicity to zebrafish were analyzed.It was found that the optimal preparation conditions resulted in 33.1%pesticide loading rate in microcapsules with a particle size of 3.99±0.55?m.The 24 h cumulative release rate of chlorpyrifos from CPF@CM was 2.34 times higher at 35°C than at 15°C,and the stomach toxicity of the microcapsules against third instar larvae of P.xylostella was1.71 times higher at 35°C than at 15°C.Based on the release kinetic fitting results,it was hypothesized that the release of chlorpyrifos was controlled by two processes:core dissolution and capsule wall dissolution swelling.The contact angles of CPF@CM on cucumber and peanut leaves were 46°and 60°,while those of the control chlorpyrifos EW on both leaves were 55°and 104°,indicating that CPF@CM has good wetting and spreading properties.In anti-UV degradation experiment,the degradation rate of chlorpyrifos for 72 hours was twice that of CPF@CM,indicating that the microcapsules could delay the degradation of chlorpyrifos under UV light irradiation and improve the stability of the pesticide.In addition,the acute toxicity of CPF@CM to zebrafish was reduced by 5.6 times compared with that of chlorpyrifos,indicating that it can reduce the potential hazard of chlorpyrifos to aquatic organisms.This work initially established a temperature-responsive pesticide controlled release theory with phase change materials as the switch,which provides a solid theoretical basis and effective technical support for the development of controlled release pesticide formulations.(3)pH-responsive prochloraz microspheres with metal-polyphenol coated calcium carbonate as a carrier can improve foliage retention and provided a long protection window against Sclerotinia disease:Based on the principle of acid release during the infestation of oilseed rape by Sclerotinia sclerotiorum,the pH-responsive controlled release formulation PC@TA/Cu was prepared by using the excellent adsorption and acid disintegration properties of porous calcium carbonate and the adhesion property of metal polyphenol complex film as the carrier loaded with prochloraz.Release experiments showed that the 48 h release rate of prochloraz from PC@TA/Cu at pH=3 was 1.63 times higher than that under neutral conditions.Leaf retention experiments showed that PC@TA/Cu retained 1.50 times and 1.49 times than Pro@Ca CO₃ on oilseed rape and cucumber leaves,respectively.These results indicated that there was an interaction force between the metal-phenolic film and the functional groups on the surface of the leaves,resulting in good resistance to rainwater flushing.Finally,the biological activity and acute toxicity of PC@TA/Cu to non-target organisms were verified by mycelial growth rate method,in vivo potting and static toxicological method.The results showed that after seven days of spraying PC@TA/Cu,it was 10.9%more effective than prochloraz EW against Sclerotinia disease.In addition,PC@TA/Cu could effectively reduce the acute toxicity of prochloraz to zebrafish,and the 96 h LC₅₀for zebrafish was about 4 times lower than that of prochloraz.This study provides the first time to load pesticides through calcium carbonate and metal polyphenol composite carriers,which provides ideas to construct new pesticide dosage forms with release time and dose that meet the actual prevention and control needs,and improve the compatibility of pesticides with the environment,which is important for the green development of agriculture and ecological safety.