Studies On The Degradation Of Three Organophosphorous Pesticides In Leafy Vegetables By Potassium Ferrate

With the globalization of agricultural products trade and requirement of protecting consumption safety, pesticide residue as a technical barrier plays increasingly prominent role in international trade of agricultural products. Maximum residue limit (MRL) of pesticide residues in agricultural products has become more and more strict, and the quality and safety of agricultural products have attracted much of attention around the world. Leafy vegetables are often planted in high temperature season in our country, and often attacked by pests and diseases. The production of leafy vegetables can not be without pesticides, but the improper use of pesticides makes pesticide residues in leafy vegetables severely over. Studies on pesticide residues will have a very important significance to improve vegetables' edible safety and competitive power in export.Potassium ferrate is a strong oxidant, which can effectively degrade the chloroform pre-product in water, a large number of organic and inorganic pollutants, and no secondary pollution, studies have confirmed that potassium ferrate can degradate organophosphorous pesticides in water such as dichlorvos, chlorpyrifos, dimethoate. In this paper, the degradation of organophosphorous pesticides in leafy vegetables by potassium ferrate were studied, spinach and Chinese cabbage as the test materials, dichlorvos, chlorpyrifos and dimethoate as the test pesticides. This research refers to following aspects:1. Under the open-field condition, it was investigated that potassium ferrate degraded organophosphorous pesticides in spinach. Pesticide residues were detected by using GC-NPD. The results showed that dichlorvos, chlorpyrifos and dimethoate residues in spinach were reduced obviously by spraying potassium ferrate. The effect of degradation was the best by 600mg/L concentration of potassium ferrate. Dimethoate residue in spinach was descended clearly along with the concentration of potassium ferrate ascending, for dichlorvos and chlorpyrifos, the trend was not clear. Peroxidase (POD) and catalase (CAT) activities, malondialdehyde (MDA), chlorophyll, protein, soluble sugar and Vc contents of spinach were determined, after spinach was treated by spraying potassium ferrate. The test confirmed that potassium ferrate did not alter the basic physiological and biochemical indication of spinach.2. The concentration of potassium ferrate was taken 600mg/L, as to study effects of potassium ferrate on low-dose and high-dose pesticide, chlorpyrifos as an example. It found that potassium ferrate could degradate low-dose and high-dose chlorpyrifos, but had fast degradation for low-dose. It also found that spinach was treated by spraying chlorpyrifos, compared with untreated spinach, its POD and CAT activities, MDA and protein contents increased, while soluble sugar and Vc contents decreased, which could cause by pesticides stress, but it would recover after a period of time. Therefore, finding a technique of reducing pesticide residues in vegetables to alleviate pesticides stress on plants and to improve edible safety of vegetables is very meaningful.3. 600mg/L potassium ferrate was applyed on pakchoi, also found potassium ferrate could clearly degradate dichlorvos, chlorpyrifos and dimethoate residues in pakchoi. POD and CAT activities, MDA, chlorophyll, protein, soluble sugar and Vc contents of pakchoi were measured. The results showed that the basic physiological and biochemical level of pakchoi did not varied after spraying potassium ferrate.4. Potassium ferrate was compared with several chemical agents of degradating pesticide residues. The results indicated that degradation effects of potassium ferrate on dichlorvos, chlorpyrifos and dimethoate were significantly better than that of H2O2 and agricultural rare earth.5. Potassium ferrate as detergent could also effectively remove dichlorvos, dimethoate, chlorpyrifos residues in spinach, and the orthogonal test confirmed that, the reductions of chlorpyrifos and dimethoate were increased with concentration and time increasing, concentration was the bigger factors in removal of dichlorvos. In addition, potassium ferrate did not basically change the physiological level of spinach, and did not have bad effects on the quality of spinach.6. Potassium ferrate could obviously degrade organophosphorous pesticides, and the order of degradation rate: dichlorvos > chlorpyrifos > dimethoate. That potassium ferrate could degrade dichlorvos, chlorpyrifos and dimethoate was verified by GC-MS, and without producing more toxic organic compounds, safety feasible, but the degradation pathway has yet to be studied.The results confirme that potassium ferrate is applied in vegetables growth to degrade organophosphorous pesticides is feasible. It is advantageous in enhancing the edible security of vegetables and the international competitive power in vegetables export.