Dietary Risk Assessment Of Haloxyfop-p-methyl On Rape And Its Removal In Water

In order to find out the final residue of 48%haloxyfop-p-methyl emulsifia ble concentrate and its metabolite haloxyfop-p in rapeseed,understand its envir onmental impact,scientifically assess its dietary risk,and study the removal me chanism of haloxyfop-p-methyl wastewater with bioaccumulation and reproducti ve toxicity.This paper first established the residue detection method of haloxyf op-p-methyl and its metabolite haloxyfop-p in rapeseed by recovery test.On th is basis,a field experiment was conducted to study the residual amount of the active ingredients of haloxyfop-p-methyl after applying 48%haloxyfop-p-methy l emulsifiable concentrates on rapeseed.Then the dietary risk was assessed.Fin ally,photocatalytic degradation technology was used to study the removal of h aloxyfop-p-methyl in water.The research contents include:（1）A method for the determination of haloxyfop-p-methyl and haloxyfop-p residues in rapeseed samples was established by high performance liquid chromatography（HPLC）and high performance liquid chromatography-tandem mass spectrometry（HPLC-MS/MS）.To determine the haloxyfop-p-methyl residue,its rapeseed sample was extracted with acetonitrile,purified with florisil column.To determine the residue of haloxyfop-p,its rapeseed sample was extracted with Na OH-methanol mixed solution,purified with n-propyl ethylenediamine（PSA）.In the range of 0.03-9.00 mg/L,there was a good linear relationship between the mass concentration（x）and peak area（y）of haloxyfop-p-methyl and haloxyfop-p,and the correlation coefficients were greater than 0.999.The average recoveries of haloxyfop-p-methyl and haloxyfop-p in rapeseed were 77%～100%at three spiked concentration levels of 0.05,0.30 and 3.00 mg/kg,with the relative standard deviations（RSD）ranged from 1%to 13%.The limit of quantitation（LOQ）of haloxyfop-p-methyl or haloxyfop-p in rapeseed samples was 0.05 mg/kg,which met the requirements of pesticide residue analysis.（2）The final residue test of 48%haloxyfop-p-methyl emulsifiable concentrates on rape was carried out in eight places one year.It was shown that the total residues of haloxyfop-p-methyl was less than 0.1 mg/kg in the rapeseed collected at the mature stage by applying 50.4 g a.i./ha（preparation dosage was 7 g/mu）.According to the pesticide registration and the per capita dietary structure of the residents in China,the dietary risk of haloxyfop-p-methyl was assessed.The results showed that the national estimated daily intake of haloxyfop-p-methyl for the general population was 0.04656mg,accounting for 105.58%of the daily allowable intake,indicating that it may have an unacceptable risk to the health of the general population,and 0.1 mg/kg was recommended as the MRL value of haloxyfop-p-methyl in rapeseed.（3）Reed was selected as the raw material for the preparation of biochar,and Zn Fe₂O₄/BC photocatalysis composite was prepared by simple coprecipitation method.The removal of haloxyfop-p-methyl from water by Zn Fe₂O₄/BC activated persulfate（PMS）under visible light was studied and evaluated.The degradation process was studied by SEM,XRD,XPS,FTIR and BET.The results show that Zn Fe₂O₄/BC has high photocatalytic activity,and the removal rate of Zn Fe₂O₄/BC/PMS/Vis can reach 92.3%in 90 min.In addition,batch experiments were conducted to explore the effects of material dosage,PMS concentration,p H value and inorganic anions on the removal efficiency;the quenching experiment confirmed that both SO₄^·-and·OH participated in the reaction process of Zn Fe₂O₄/BC/PMS/Vis system,and·OH was the main component.（4）The removal rate of haloxyfop-p-methyl in the actual water（tap water and Liuyang River）is lower than that of the simulated study in laboratory,which may be related to the influence of many interference factors（inorganic ions,organic matter,microorganism,etc.）in the actual water;the reason why the removal rate of the metabolite haloxyfop-p is lower than haloxyfop-p-methyl may be related to some special groups of the intermediate products of haloxyfop-p;in addition,batch experiments show that the degradation process of them is different.