Study On The Absorption Law Of Heavy Metal And Pesticide And Their Residues In Edible Fungi

The problem of excessive heavy metals and pesticide residues in the edible fungi fruit body is not only the main problem in the quality and safety assure of edible fungi production, but also the key measure to control the quality and safety of edible fungi.The research study the heavy metals variation of cultivation substract in different periods, the heavy metals absorption regulation of edible fungi and the build-up effect of the absorption regulation using mathematical model via adding different concentration of heavy metals to the cultivation substract. The results showed that the existence of heavy metals in the cultivation material was quite steady, high-temperature sterilization of the cultivation had almost no effect on heavy metals, the heavy metals content in the cultivation substract increased after fruit body collection, and the heavy metal abortion increased as the heavy metal content we added increased. The absorption capacity was different between different edible fungi and heavy metals. The accumulation ability of the four heavy metals was as follows: Hg> Cd> Pb> As; the heavy metals content within the edible fungi fruit body was significantly relative with the heavy metal addition to the culture media. The background value and the possible maximum accumulation of all kinds of edible fungis were calculated through the accumulation equation: y = c / (1 + ea-bx). According to the international standard of the safety limited value on the edible fungi products security, we predict the heavy metal's safety limited value in the edible fungi cultivated substract by using the inverse function of accumulation equation to control the heavy metal pollution.In the article, 9 kinds of pesticides such as dichlorvos were selected to carry on the residues experiment on 6 kinds of edible fungi. The impact of pesticides on the stage of growth, the degradation law of pesticides on the growth process of mycelium and fruiting body and the final residue in fruiting body because of different application methods were separately studied. Then results showed that 9 pesticides'application can have different effects on mycelium and fruit body, (I) all strains no growth at 0.1% dichlorvos and 0.1% chlorpyrifos; (II)100% inhibition of the mycelium of Hericium erinaceus at 0.1% thiophanate methyl, but pyrethroid pesticide no significant impact; (III) Pleurotus ostreatus and agrocybechaxinggu no fruiting if spraying dichlorvos at fruiting stage and most of abnormal fruiting body if spraying chlorpyrifos. After pesticides added to the cultivating materials, 100% of dichlorvos can be all degraded, thiophanate-methy into deltamethrin, chlorothalonil almost all over. What's more, pesticides can be degraded at the growth of mycelium, almost in fruit body no or few residue, but only chlorpyrifos and fenpropathrin out of standard. Then, after pesticides'application, results also showed lentinulaedodes had the fastest degradation rate. bifenthrin or chlorothalonil with the largest half-time all was 1.65d and at the same time thiophanate-methyl with the smallest was 0.25d. During the the final experiment about residue in lentinulaedodes, spraying 150mL/667m2 dose of dichlorvos when bags were opened, spraying 112.5g/667m2 dose of Chlorpyrifos when bags were opened,spraying pesticides after fruiting, Pesticide residues were quite low by using bifenthrin. spraying 45mL/667m2 dose of fenpropathrin before friuting, Cypermethrin could not surpass 35mL/667m2 after friuting, spraying 112.5g/667m2 dose of Chlorpyrifos after fruiting. Carbendazim, Thiophanate methyl and chlorothalonil can only be sprayed when the bags were opened,with maxium dose reaching 300g/667m2, 215.5g/667m2, 405g/667m2 respectively, Will not lead to fruiting body residues exceeding. In this article,other five kinds of edible fungi also get different results.