吡虫啉在土壤中的吸附及作用机理研究

研究了吡虫啉在土壤中的吸附及作用。结果表明，吡虫啉在土壤中的吸附主要归结于土壤有机质对它的结合，其它因素影响较小，Ｆｒｅｕｎｄｌｉｃｈ常数Ｋｆ与ＯＭ（％）有较好的相关性；吡虫淋能与腐殖酸作用发生电荷转移，并能与腐殖酸羟基形成氢健。     

Time dependent sorption behavior of dinotefuran,imidacloprid and thiamethoxam

Dinetofuran (DNT), imidacloprid (IMD) and thiamethoxam (THM) are among the neonicotinoid insecticides widely used for managing insect pests of agricultural and veterinary importance. Environmental occurrence of neonicotinoid in post-application scenario poses unknown issues to human health and ecology. A sorption kinetic study provides much needed information on physico-chemical interaction of neonicotinoid with soil material. In this research study, time-dependent sorption behavior of DNT, IMD and THM in vineyard soil was studied. Sorption kinetics studies were conducted over a period of 96 hours with sampling duration varying from 0, 2, 4, 8, 12, 24, 60 and 96 hours. All three neonicotinoids exhibited very low sorption potential for the soil investigated. Overall percent sorption for all three neonicotinoids was below 20.04 ± 2.03% with highest percent sorption being observed for IMD followed by DNT and THM. All three neonicotinoids are highly soluble with solubility increasing with IMD < THM < DNT. Although, DNT has the highest solubility among all three neonicotinoids investigated, it exhibited higher percent sorption compared to THM, indicating factors other than solubility influenced the sorption kinetics. Low sorption potential of neonicotinoids indicates greater leaching potential with regard to groundwater and surface water contamination.     

藻类对大型溞抵抗农药的毒理学影响及其机制

为探究藻类对大型溞农药抗性的影响及其机制,分别将5种淡水广布的甲藻、硅藻、绿藻、隐藻、蓝藻等量培育大型溞后,再将大型溞分别暴露于2种杀虫剂吡虫啉(水溶性)和氰戊菊酯(脂溶性)中,测定大型溞的半数致死剂量、化学计量比(P/C,N/C)和脂肪酸含量.研究表明:与生源性化学元素氮磷相比,N3不饱和脂肪酸能更好揭示大型溞对藻类的捕食关系;藻类的N3不饱和脂肪酸含量是影响大型溞对水溶性农药抗性的关键因子;大型溞对脂溶性农药的抗性差异比暴露在水溶性农药中更明显.因此,藻类的N3不饱和脂肪酸是预测大型溞对水溶性农药抗性强度的最佳因子,其有助于更准确地预测以不同藻类为食的大型溞食物链对自然环境中污染物的抗性和风险.     

吡虫啉对蜜蜂幼虫的室内毒性研究

吡虫啉是目前使用最广泛的新烟碱类农药,其不合理使用破坏蜜蜂的嗅觉记忆能力,影响采集行为,导致多种亚致死效应。利用室内人工饲养蜜蜂幼虫技术,选取意大利蜜蜂幼虫为研究对象,经3 d适应性饲养后,连续3 d喂食含不同浓度的吡虫啉日粮,测定蜜蜂幼虫的存活率、化蛹率和羽化率,评估吡虫啉对蜜蜂幼虫生长发育影响。结果表明,吡虫啉处理剂量为15ng·幼虫~(-1)时,并不影响蜜蜂幼虫存活率、化蛹率和羽化率;当处理剂量达到150 ng·幼虫~(-1)时,蜜蜂幼虫羽化率下降,但不影响蜜蜂幼虫的存活率和化蛹率;幼虫7 d半数致死剂量为2 300 ng·幼虫~(-1)。高剂量吡虫啉对蜜蜂幼虫存活率、化蛹率和羽化率均存在影响,处理剂量越高,存活率、化蛹率和羽化率越低,呈高度负相关(r=-0.99,-0.94,-0.89),同时蜜蜂幼虫的羽化时间延长。研究可为吡虫啉的合理使用提供科学参考。     

Photochemistry of insecticide imidacloprid: direct and sensitized photolysis in aqueous medium

The direct and sensitized photodegradations of imidacloprid, 1-(6-chloro-3-pyridinylmethyl)-N-nitro-2-imidazolidinimine, were investigated in aqueous solution and with and without various photo-sensitizers. Results of the study revealed that the intensity of lamp-house and irradiation wavelength had significant effects on the photolysis of imidacloprid. Complete degradation of 20 mg/L imidacloprid in aqueous phase was observed in 40 min under ultraviolet(UV) irradiation system, suggesting the ultraviolet ray played significant role in direct photolysis of imidacloprid. The additions of various photo-sensitizers lead to improve the degradation efficiency of imidacloprid under the irradiation of black light fluorescent lamp. TiO2 was the most efficient in the photo-catalytic degradation of imidacloprid among other photo-sensitizers in used this study. However, addition of acetone inhibited the photolysis of imidacloprid under the irradiation of UV, indicating the occurrence of competition between acetone and imidacloprid for photos. Mineralization of the imidacloprid was examined to clarify the final photochemical degradation products of the insecticide which were CO2, CI^- and NO3^-. Complete photo-oxidation of nitrogen to NO3^- occurred very slowlyvia the intermediate formation of NH4^ and NO2^- .     

吡虫啉与脱氧核糖核酸相互作用机理及其影响因素

在荧光分光光度计上进行共振光散射测定,研究了水相介质中吡虫啉与脱氧核糖核酸间的相互作用机理,实验表明,在pH1．5—1．7的范围内,加入DNA导致吡虫啉共振光散射增强,在345nm处,存在一最强的共振光散射增强峰．这主要是由于DNA诱导吡虫啉聚集所致,本文考察了聚集的影响因素,并确定了最佳聚集条件。     

Development of controlled release formulations of imidacloprid employing novel nano-ranged amphiphilic polymers

Amphiphilic copolymers, synthesized from poly (ethylene glycols) and various aliphatic diacids, which self assemble into nano-micellar aggregates in aqueous media, were used to develop controlled release (CR) formulations of imidacloprid [1-(6 chloro-3-pyridinyl methyl)-N- nitro imidazolidin-2- ylideneamine] using encapsulation technique. High solubilisation power and low critical micelle concentration (CMC) of these amphiphilic polymers may increase the efficacy of formulations. Formulations were characterised by Infrared (IR) spectroscopy, Dynamic Light Scattering (DLS) and Transmission Electron Microscope (TEM). Encapsulation efficiency, loading capacity and stability after accelerated storage test of the developed formulations were checked. The kinetics of imidacloprid release in water from the different formulations was studied. Release from the commercial formulation was faster than the CR formulations. The diffusion exponent (n value) of imidacloprid, in water ranged from 0.22 to 0.37 in the tested formulations. While the time taken for release of 50 % of imidacloprid ranged from 2.32 to 9.31 days for the CR formulations. The developed CR formulations can be used for efficient pest management in different crops.     

Modelling the biphasic sorption of simazine,imidacloprid, and boscalid in water/soil systems

The sorption kinetics of simazine (6-chloro-N,N′-diethyl-1,3,5-triazine-2,4-diamine), imidacloprid (1-(6-chloro-3-pyridylmethyl)-N-nitroimidazolidin-2-ylideneamine), and boscalid (2-chloro-N-(4′-chlorobiphenyl-2-yl)nicotinamide), three pesticides of wide use in agriculture, was determined in five different water/soil systems over a time interval from the initial few seconds to about 1 month. In all the experiments, sorption kinetics showed a biphasic pattern characterized by an initial, relatively short phase with a high sorption rate and a later phase with much a lower sorption rate. Initial sorption capacity increased with soil organic carbon content and with sorbate hydrophobicity. We postulate that the first phase of the process involves a fast second-order sorption reaction on superficial sites of soil particles, whereas the second phase depends on diffusion-controlled migration to internal binding sites. A kinetic equation based on this hybrid model accurately fitted all data sets. Less satisfactory results were obtained employing the pseudo-first order, pseudo-second order, Elovich, two site non-equilibrium, or Weber-Morris equation. The superior performance of the hybrid model for describing boscalid sorption probably reflects the high hydrophobic character and consequent low diffusion rates of this compound. The accuracy of modelling was in any case strongly dependent on the time interval considered.     

Mathematical prediction of imidacloprid persistence in two Croatian soils with different texture,organic matter content and acidity under laboratory conditions

In the present laboratory study, persistence of imidacloprid (IMI) as a function of initial insecticide concentration and soil properties in two Croatian soils (Krk sandy clay and Istria clay soils) was studied and described mathematically. Upon fitting the obtained experimental data for the higher concentration level (5 mg/kg) to mathematical models, statistical parameters (R ², scaled root mean squared error and χ ² error) indicated that the single first-order kinetics model provided the best prediction of IMI degradation in the Krk sandy clay soil, while in the Istria clay soil biphasic degradation was observed. At the lower concentration level (0.5 mg/kg), the biphasic models Gustafson and Holden models as well as the first-order double exponential model fitted the best experimental data in both soils. The disappearance time (DT₅₀) values estimated by the single first-order double exponential model (from 50 to 132 days) proved that IMI can be categorized as a moderately persistent pesticide. In the Krk sandy clay soil, resulting DT₅₀ values tended to increase with an increase of initial IMI concentration, while in the Istria clay soil, IMI persistence did not depend on the concentration. Organic matter of both experimental soils provided an accelerating effect on the degradation rate. The logistic model demonstrated that the effect of microbial activity was not the most important parameter for the biodegradation of IMI in the Istria clay soil, where IMI degradation could be dominated by chemical processes, such as chemical hydrolysis. The results pointed that mathematical modeling could be considered as the most convenient tool for predicting IMI persistence and contributes to the establishment of adequate monitoring of IMI residues in contaminated soil. Furthermore, IMI usage should be strictly controlled, especially in soils with low organic matter content where the risk of soil and groundwater contamination is much higher due to its longer persistence and consequent leaching and/or moving from soil surface prior to its degradation.     

Seed pre-soaking with 24-epibrassinolide reduces the imidacloprid pesticide residues in green pods of Brassica juncea L.

The effect of 24-epibrassinolide seed soaking on imidacloprid residues in green pods and mature seeds of Brassica juncea L. plants was investigated. The activities of the antioxidative enzymes glutathione-S-transferase, glutathione peroxidase, glutathione reductase, ascorbate peroxidase and guaiacol peroxidase, and the content of glutathione were determined. Imidacloprid residues in green pods were analyzed and quantified by gas chromatography-mass spectrometry, revealing that 24-epibrassinolide treatment resulted in a decrease of residues by almost 30%. In mature seeds, no pesticide residues were detected. Activities of all the antioxidative enzymes and glutathione content were found to be high in plants grown in soil amended with 300 mg imidacloprid kg^?1 soil, but pre-soaking with 100 nmol L^?1 24-epibrassinolide further enhanced the activities of all these enzymes and the glutathione content.