| China has become the main country for ginseng producing and exporting in the world. Jilin and Heilongjiang Province are the main production bases of ginseng in China, which ginseng production accounted for more than90%of the country’s total output, export output outputs accounted for80%of the total country export output. However, China’s ginseng production and value were out of proportion, the output value was very low. The first reason was the low quality of ginseng products in China, more importantly, pesticide residues in ginseng products in China was seriously overweight. The reasons leading to excessive pesticide residues in ginseng, were mainly due to the unreasonable use of pesticides, particularly use of pesticides being of highly toxic and uneasible degradation in a large-scale. Several countries including the European Union, the United States of America, South Korea, Japan and other countries have established detection methods of most of pesticides and pesticide maxium residue limits on ginseng, and the standards are getting higher and higher, but in China detection methods of residues on ginseng were established for only two kinds of pesticides, the standards of pesticide residue limits were also limited to organochlorine pesticides. Therefore, pesticide detect limits of exported ginseng were enacted by the importing countries and we had to accept passively the results of residue detection, the phenomenon were common that ginseng exports due to excessive pesticide residues had been repeatedly returned. Mancozeb(MZ) as the largest fungicide used on ginseng, belongs to ethylene-bis dithiocarbamate (EBDCs) fungicides, has better control effect to Alternaria black spot caused by Alternaria panax, gray mold disease caused by Botrytis cinerea, Phytophthora blight caused Phytophthora cactorum and seedling diseases of ginseng by Pythium sp.. However, ethylene thiourea (ETU), as the metabolite of Mancozeb in ginseng plants and environment could induce teratogenic, carcinogenic and mutagenic effect. Triflumizole as one of systemic fungicides with high efficiency, low toxicity, low-residue and both protective and therapeutic effect is widely used in prevention and treatment of gray mold, Alternaria black spot and other diseases on ginseng and difficult to produce resistance. Therefore, researchs on residue detection methods and residue degradation of Mancozeb, ETU and Triflumizole were carried out to regulate the application of Mancozeb and Triflumizole on ginseng, which has important significance to establish their residue limit standards and propose maximum residue limits (MRLs), and it is of great significance also for promoting China’s participation in the formulation of ginseng pesticide standards and pesticide residue standards, changing from passive detection for active control, and breaking through lhe barriers in international trade. The contents and results of this dissertation are as follows:1. Residual analysis techniques were established with headspace gas liquid chromatography (HS-GLC) for mancozeb (MZ) detection and high performance liquid chromatography (HPLC) for ethylene thiourea(ETU) detection in ginseng.Residue analysis method with HS-GLC for MZ:the results showed that concentration and peak area showed a good linear relationship(R2=0.9991)by spiking16ml of SnCl2solution and3ml of EDTA sodium salt solution into the reaction flask of the headspace in the range of0.20μg/mL to1.00μg/mL. The limits of detection (LOD) for mancozeb were1.4×10-1mg/L, the recoveries of the method for mancozeb varied from88.8%to89.9%, and the relative standard deviations (RSDs)varied from0.46%to5.71%at spiking levels of0.5～2.0mg/kg. The average recoveries and the relative standard derivations of mancozeb could meet the requirements for the detection of residues in ginseng.Residue analysis method with HPLC for ETU:the proposed solution pH, eluent, and alumina were11,175ml,5g, respectively, pre-treatment methods met the requirements of detection, there was no impurity peak in the blank sample chart, and recoveries of ETU in roots, stems, leaves. fruit of ginseng and soil varied from90.64%to97.46%, the relative standard deviations varied from1.02%to4.54%. The limits of detection of ETU were1.4x10-11g, the minimum detectable concentration of ETU was0.07mg-L-1by HPLC with chromatographic conditions: mobile phase of methanol:water=10:90(V/V), flow rate of0.5ml/min and wavelength of233nm. Therefore requirements were met for the detection.2. In view of high residues of fungicides in current ginseng and its products, residues of mancozeb and ethylene thiourea in representative ginseng products were detected based on the establishment of methods for detection of pesticide residues. The measured residue value of MZ in active ginseng, red ginseng, suncured ginseng, fresh gingseng, ginseng tea, gingeng sugar ginseng wine varied from0.37mg/kg to1.67mg/kg. the measured residue value (0.81mg/kg) of MZ in ginseng tea was higher than others and no detection in ginseng wine that maybe there was little quantity of ginseng in ginseng wine. Mancozeb residues in ginseng and its products were higher than the EU limits (0.1mg/kg), but less than the limits (1mg/kg)imposed by Japanese. Residue measured value of Ethylene thiourea (ETU) in active ginseng, red ginseng, white ginseng and the preservation varied from0.22mg/kg to0.52mg/kg. there was an average7.5 mg/kg of ETU in ginseng tea, which need to be rinsed with hot water for drink.3. Degradation dynamics and the final residues of mancozeb in root, stem, leaves and fruit of ginseng and soil were carried out by headspace gas-liquid chromatography analysis techniques.The results showed that spraying one time in one season at the highest dose of6250g a.i./hm2, original depositions of Mancozeb were0.89mg/kg in ginseng root,1.34mg/mg in ginseng stem,3.32mg/mg in leaves and1.21mg/kg in soil, respectively. Half-life were12.9d in ginseng root,14.1d in ginseng stem,12.3d in ginseng leaves and11.7d in soil, respectively; When spraying one time in one season at a dose of6250mg/kg, the final residues of MZ were0.32mg/kg in ginseng root,0.21mg/mg in ginseng stem,0.46mg/mg in leaves, ND mg/kg in fruit and0.18mg/kg in soil, respectivelly. When spraying one time in one season at a dose of3125mg/kg, the final residues of MZ were0.18mg/kg in ginseng root,0.14mg/mg in ginseng stem.0.31mg/mg in leaves. ND mg/kg in fruit and ND mg/kg in soil, respectivelly. Integrated a number of factors, in accordance with the recommended dose of3125g ai/hm2as well as according to foreign ginseng residue standards and test results by ourselves, maximum residue limits (MRLs) of mancozeb in ginseng roots, stems, leaves and fruit in China may be temporarily set at0.5mg/kg, spraying one time in one season.4. The degradation dynamics of Ethylene thiourea residues in ginseng root, stem, leaves, soil and fruit were determined with HPLC-UV analytical techniques. Spraying MZ75%WP one time in one season at dosages of3125,6250g a. i./hm2, the results showed that residues of ETU at harvest time were lower than0.3mg/kg in root, stem, fruits and soil, but residue in leaf were0.31mg/kg and0.46mg/kg higher than0.3mg/kg which shouldn’t be directly eaten and used for medicine. When spraying MZ75%WP at a dose of6250g a.i./hm2, the original depositions of ETU were0.45mg/kg in root,0.78mg/kg in stem,8.23mg/kg in leaf and0.98mg/kg in soil, respectively, the half-lives were12.93d in root,11.1d in stem,12.3d in leaf andl1.7d in soil, respectivelly. According to MRLs(0.20mg/kg) of the European union as well as test data by us, the MRLs of ETU may be temporarily set at0.25mg/kg in root and stem of ginseng, but it could not be determined in leaf.5. In order to reduce the use of mancozeb on ginseng and reduce its residues in ginseng and its products, the techniques for mixure of MZ with other fungicides were studied. The toxicity of Mancozeb, Propiconazole, Carbendazim and mixture of Mancozeb with other fungicides to ginseng gray mold and Alternaria black spot were tested by mycelium growth rate methods in laboratory. The results showed that Mancozeb75%WP et al had stronger toxicity with lower EC50values to the pathogens. and their control effects in field trial were carried out and the results showed Mancozeb75%WP had good control efficiency of72.1%～80.0%to gray mold disease and Alternaria black spot. Among them, both the co-toxicity coefficient and control effect in mixture at a ratio of Mancozeb and Propiconazole1:1were better than single agent and other mixtured agents.6. Final residue of Mancozeb and Propiconazole (1:1) mixture of mancozeb and ethylene thiourea at harvest time of ginseng were detected. Applying one time in ginseng growing season with mancozeb and propiconazole (1:1) mixture at dosages of3125,6250g ai/hm2, and collecting samples of roots, stems, fruits of ginseng and soil at harvest, all residues of MZ were lower than0.3mg/kg and lower than their reside value of MZ and ETU in single agents. It improved the efficacy and reduced residues of MZ in plants and soil that Mancozeb and propiconazole mixed with1:1used to control ginseng diseases.7. Spraying triflumizole30%WP one time in one season.at highest dose of340g a.i./hm2, the results showed that original depositions of Triflumizole were ND. ND,0.29,0.23,0.12and0.04mg/kg in ginseng root collected at Od,7d,14d,21d,28d later after spraying and harvest time, half-life was19.9d in ginseng root, and original deposition of Triflumizole in soil were0.25,0.16,0.11,0.12,0.10and0.03mg/kg at Od,7d,14d,21d28d later after spraying and harvest time and half-life was25.4d, so Triflumizole is easy to degradate. the maximum residue limits of triflumizole in ginseng have not be established in Japan, Canada, Korea and other countries, and MRLs was from0.5and5mg/kg in vegetable and herbs. According to MRLs in vegetables, herbs and the dynamic residue data of Triflumizole on ginseng in field trial, Triflumizole30%WP could be applied with other fungicides alternatively at the dose less than340g a.i./hm2and spraying one time in one growing season, the MRLs of Triflumizole in ginseng and soil were temporarily set at0.25mg/kg and it was not pemitted to apply Triflumizole28d before harvest time.In conclusion, it was suggested that MZ were applied one time in one growing season at dosage from3125g a.i./hm2to6250g a.i./hm2and could not be used28days before harvest time according to the residue dynamics of MZ, ETU in root, stem, leaf, fruit of ginseng and soil. residue in ginseng and its products, and results of MZ for control effect in ginseng field trial. The MRLs of MZ, ETU and Triflumizole in ginseng and its products were suggested to be0.5mg/kg,0.25mg/kg and0.25mg/kg, respectively. |
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