| Baichu (10％Fenoxaprop-P-ethyl.Cyhalofop-butyl EC) is an ultra-high effect,low-toxicity, and broad-spectrum herbicide, it is composed of Fenoxaprop-P-ethyl andCyhalofop-butyl. Previous studies of Fenoxaprop-P-ethyl and Cyhalofop-butylfocused mainly on the single herbicidal efficacy and mechanism, while availableinformation about Baichu's behavior and toxicity effect in paddyfield is rarely. Inorder to comprehensively evaluate environmental security of Baichu and itsreasonably application and ecological environmental restoration, the degradationbehavior of Baichu in paddyfield and their toxicity to two living things were studied.The main results were summarized as following:The residual determination of Baichu in paddyfield samples were investigated.The results showed: (1)A series of experiments were studied for establishing extractionmethod and clean-up method in preceding process. Identified that dichloromethane asthe extract in water sample; methanol as the extract, florisil and active carbon as thesorbent, ethyl acetate as the elution liquid in soil, rice plant and brown rice sampleswere determined finally. (2)The chromatographiccondition of Baichu were: themobile phase=methanol/water(V/V=77/23); velocity=(0min→3min)0.8mL/min,(3min→6min)0.8mL/min→0.6mL/min, (6min→7.5min)0.6mL/min→0.38mL/min, (7.5 min→13.5 min)0.38 mL/min;λmax=233nm; T=30℃. (3)The resultsshowed that the averaged recoveries of Fenoxaprop-P-ethyl ranged from 77.38％to105.77％, and the coefficient of variation was from 1.95％to 7.36％; the averagedrecoveries of Cyhalofop-butyl ranged from 75.08％to 99.06％, and the coefficient ofvariation was from 2.38％to 6.32％. The lowest detectable quantity ofFenoxaprop-P-ethyl was 1.1×10-9 g and the lowest detectable concentrations were0.00286 mg/L in water, 0.0143 mg/kg in soil, 0.0286 mg/kg in rice plant and brownrice; the lowest detectable quantity of Cyhalofop-butyl was 1.9×10-9 g and the lowest detectable concentrations were 0.00476 mg/L in water, 0.0238 mg/kg in soil, 0.0476mg/kg in rice plant and brown rice. The chromatographic fractionation ofFenoxaprop-P-ethyl and Cyhalofop-butyl＞1.5, which accorded with the request ofpesticide residue determination.The degradation behavior and environmental safety of Baichu in paddyfield wereinvestigated. The results indicated that: (1) the degradation of Fenoxaprop-P-ethyl andCyhalofop-butyl in rice plant, soil and paddywater were accordance with thefirst-order dynamic eqution Ct=C0e-kt; (2) the half-life of Fenoxaprop-P-ethyl inpaddy water, soil and rice plant were 3.28d, 1.60d and 2.18d; (3) the half-life ofCyhalofop-butyl in paddy water, soil and rice plant were 3.18d, 1.56d and 2.20d;(4)Baichu was applied under recommended dose, the residues of its two effectivecomponents were lower than MRL in paddyfield samples.The determination method of chlorophyll in the experiment of duckweed growthinhibiton was optimized. Moreover, a static experiment was made to probe into theunion toxicity of Fenoxaprop-P-ethyl and Cyhalofop-butyl to assess theeco-environment effect and toxicity correctly. The results indicated: (1) Soakingmethods could extract the most chlorophyll, but it was very slowly; and chlorophyllwas lost so much by Amon methods. The best method was freezing method because itwas the fastest and the most convenient. (2) IC50 of Fenoxaprop-ethyl andCyhalofop-butyl to Lemma Paucicostata for 96 h were 3.33 and 5.04 mg/Lrespectively, while the IC50 of their joint toxicity was 3.14 mg/L. The additive index(AI) was 1.566, the combined toxicities were the synergism action. The content ofchlorophyll a and chlorophyll b of Lemma Paucicostata both affected by the singleand joint toxicity of Fenoxaprop-ethyl and Cyhalofop-butyl with the concentrationincreased. (3) The toxicity of Fenoxaprop-ethyl to tadpoles was much more than thatof Cyhalofop-buty. After treatment 24h, 48h, 96h, the LC50 of Cyhalofop-butyl for thetadpole were 43.08, 40.33 and 38.20 g/L respectively; and the LC50 ofFenoxaprop-ethyl for the tadpole were 8.17, 7.40 and 6.85 mg/L respectively.According to the standard of acute immobilization toxicity to amphibians, Cyhalofop-buty was low-toxin to Bufo gargarizans tadpole and Fenoxaprop-ethyl wasmedium-toxin to them. Using the addictive index method of marking, the addictiveindex (AI) of Cyhalofop-butyl and Fenoxaprop-ethyl to tadpole were -0.39, -0.33,-0.30 in 24h, 48h, 96h respectively. The results showed their antagonistic action. Itwas suggested that the two kinds of herbicides should be strictly controlled in order toprevent hazard to the aquatic animal and the environment. |
PDF Full Text Request