Bioavailability Of Pyrethroid Pesticides By Water Factors Study On The Law And Mechanism Of Influence

Pyrethroid pesticides are widely used in agriculture,forestry,environmental health andother fields.They can enter environmental water through surface runoff,produce toxicity to aquatic organisms and accumulate in organisms,and cause harm to human health through the food chain.Water properties（such as p H,ionic strength,dissolved organic matter（DOM）,etc.）have potential influence on the morphology and effectiveness of pesticides in water,which makes it difficult to evaluate the bioeffectiveness of pesticides in environmental water.Based on PCB chrysanthemum ester,CFC’s armor cyanogen chrysanthemum ester,efficient cyanide deltamethrin,permethrin,fenvalerate,cypermethrin,fluorine,fenvalerate and deltamethrin eight kinds of pyrethroid pesticides as the research object,using silicone rubber（SR）method for passive sampling method to determine the water strain concentration of pesticide free state,to characterize target biological effectiveness of pesticides in water,The effects of p H,ionic strength,DOM and other factors on the bioavailability of pyrethroids in water were investigated.The main results are as follows:1.In alkaline environment of water with p H greater than 7,pyrethroid pesticides produce co-metabolites and 3-phenoxybenzyl alcohol（3-PBOH）through hydrolysis,thus reducing the C_free of pyrethroid pesticides,and the stronger the alkalinity,the more obvious the C_freedecrease.The correlation model between p H and C_freeof pyrethroid pesticides was established,which can roughly predict the bioavailability of pyrethroid pesticides in water.2.The cations Na⁺,K⁺,Ca²⁺,Mg²⁺had no significant effect on the C_free of eight pyrethroids in water.The presence of anions Cl^-,SO₄^2-,HCO₃^-and NO₃^-reduced the target pesticide C_freeto a certain extent,and the influence degree was in the order of HCO₃^->NO₃^->SO₄^2->Cl^-.HCO₃^-promotes the degradation of pesticides to produce the metabolite 3-phenoxybenzaldehyde（3-PBCHO）by increasing the p H of water,thus reducing the C_free of pesticides.Different concentrations of Na Cl in water had no effect on C_free of target pesticide.3.The adsorption of humic acid（HA）,fulvic acid（FA）and humic acid/fulvic acid mixture on pyrethroid pesticides can significantly reduce the C_free of pyrethroid pesticides,and the decreasing trend is in accordance with the first-order kinetic equation.The higher the DOM concentration was,the more obvious the reduction of C_free of pesticides was,and the reduction of humic acid on target pesticides was greater than that of fulvic acid.The decreasing degree of C_free of pyrethroid pesticide in different humic acid and fulvic acid mixed aqueous solution was in the order of humic acid>humic acid:fulvic acid（5:1）>humic acid:fulvic acid（2:1）>humic acid:fulvic acid（1:1）>humic acid:fulvic acid（1:2）>humic acid:fulvic acid（1:5）>fulvic acid.A correlation model between DOM and pyrethroid pesticide C_free was established to predict the bioavailability of pyrethroids in water.4.The adsorption of humic acid on the target pesticide conforms to the pseudo-first-order kinetic model;The adsorption of fulvic acid on the target pesticide conforms to the pseudo-second-order kinetic model.The adsorption thermodynamics of humic acid and fulvic acid were consistent with Langmuir equation,which indicated that the adsorption of humic acid and fulvic acid on target pesticide was spontaneous,endothermic and entropic process.Humic acid and fulvic acid interact with the target pesticide mainly through hydrogen bond,dipole moment force or coordination bond exchange.5.Under different water conditions,permethrin and deltamethrin C_free showed a good linear positive correlation with the 96 h mortality rate of zebrafish,which verified the reliability and rationality of the correlation model of the influence of various water factors on the bioavailability of pyrethroid pesticides.