| Pesticides which are used widely in agriculture played a very important role to ensure the agricultural production. As the extensive use of chemical pesticides, the serious environmental problems getting more and more serious cannot be ignored. ZJ0273, a novel pyrimidynyloxybenzoic herbicide, is a widely used in rape fields to control weed infestation with a high herbicidal activity. But the bound residue of ZJ0273in soil has been verified that it would do harm to after-reap crops as it accelerated to a certain amount. Thus, dvelopment of efficient and safe pesticide to reduce the environmental risk has always been a hot issue all-around. Polymeric materials which can be attached with pesticide compounds through package, bonding and other ways to realize control/slow release have been confirmed to be a good choice to improve the utilization of pesticide and reduce the environmental risk. Therefore, based on the theory of controlled-release, a new preparation of herbicide "hydrogel coated ZJ0273"(HGC-ZJ0273) was developed to reduce the soil residue and environmental risk.Starch grafted hydrogel which is largely functioned with hydrophilic groups is a good choice to load pesticide on to ensure controlled-release. In this study, a gel of hydrolyzed cassava starch grafted polyacrylamide was generated under EB irradiation of10MeV. FTIR and SEM a technology was applied to confirm the structure of the grafted and hydrolyzed polymers. The13C-NMR spectra of raw starch and St-g-poly(acylamide-co-methylbisacrylamide) also showed that the grafting copolymerization would occur on C6of the anhydrate glucose. Univariate analysis was employed to evaluate the effects of irradiation dose, monomer-to-starch ratio and crosslinker-to-starch ratio et al. on the grafting parameters and absorbing properties. The results showed that all the factor but crosslinker could significantly affect grafting parameters and absorption in aquatic system. The optimum conditions to get best absorption property were AM/AGU=4.5mol mol-1, D=8kGy, MB A/AM=4mmol mol-1and the St-g-poly(AM-co-MBA) hydrolyzed in5%NaOH aquatic solution at75℃for120min, and the optimum property was1452g g-1in distilled water and83g g-1in0.9%NaCl aquatic solution, respectively.Based on the above methodology of hydrogel preparation, the hydrogel coating ZJ0273preparation was carried out with the initiation of K2S2O8. A solution of novel herbicide ZJ0273in DMB with appropriate surfactant was loaded in the hydrogel in the procedure of polymerization with an emulsion form. SEM technology was applied to characterize the morphology of HGC-ZJ0273, which shows a multiparous structure to make H2O and pesticide molecules penetrating in and out of the polymeric network. The releasing tests of HGC-ZJ0273were taken in the dionized water (H2O), buffer solution (BS) and soil extraction (SE), and the order of the releasing ratio would be RsE>R H2O> RBF. HGC-ZJ0273still shows high growth inhibition on its target plant at a very low concentration, and the EC50is67.82μg g-1soil with pot incubation test.In order to clarify the environmental fate and behavior of the HGC-ZJ0273in aerobic soil, an isotope tracing method and mass balance method were employed with [B ring-4,6-14C] ZJ0273. Both of the HGC-ZJ0273and ZJ0273in traditional way was applied in3aerobic soils. At the end of incubation (80d) the mineralization of applied radioactivity in S2and S3with HGC-ZJ0273are much higher than traditional ZJ0273in the two soils, which means that the hydrogel coating process would reduce the total residue of ZJ0273and its metabolisms in soil with the range of17.1%to19.6%.The residue cut of HGC-ZJ0273in S2was reflected in bound residue (BR) reducing. The radioactivity of HGC-ZJ0273bounded in soil was43.7%, comparing with56.1%of traditional ZJ0273. At the end of incubation, the total radioactivity of BR and ER in S2which had been treated with HGC-ZJ0273reduced an average of13.3%comparing with traditional ZJ0273. The residue regulation of HGC-ZJ0273in S3showed a different way. The extractable residue of HGC-ZJ0273was reduced significantly comparing with ZJ0273, with an ER of22.1%of the former amd60.6%for the later. The treatment of hydrogel coating could cut the total residue of ZJ0273with an average of24.6%in S3.The hydrogel coating process of ZJ0273could significantly reduce the total residue of ZJ0273in S2and S3, with a reason of high organic matter ratio which would promote degradation of ZJ0273and the metabolisms by microorganisms. The addition of biodegradable hydrogel would enhance that process with microorganisms multiplying in and outside of the gel network. For S3, the hydrogel loading processing didn’t reduce the percentage of BR comparing with traditional ZJ0273. The bonding between metabolisms of ZJ0273(all with a-COOH on) and the large amount of-NH2et al. would increase the bound constituents in soil-gel system. The hydrogel coating process doesn’t make any difference on the mineralization, extractable residue (ER) and bound residue (BR) in S1comparing with ZJ0273in traditional way because of the soil acidicy and low organic matter, which would lead to the lack of microorganisms. |
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