The behaviour of cyantraniliprole was studied in a lysimetric experiment. The experiment was carried out at the lysimeters of the Soil Research Station of Moscow State University from June 2015 to December 2018. The soil of lysimeter is soddy-podzolic silt loam. The insecticide was applied at the recommended and tenfold rates in 2015 and 2016. The maximum depth of migration of cyantraniliprole in the soil profile was 35 cm in October 2015 and 40 cm in October 2016. Cyantraniliprole was found in the leachate of lysimeter water 2 weeks after its first application in 2015 and continued until the end of 2018, that is, 2 years after the last treatment. Cyantraniliprole was found in most of the water samples analyzed. The maximum concentrations of cyantraniliprole in the leachate were 12.5 and 2.6 μg L−1 in lysimeters with tenfold and recommended doses, with mean values of - 1.7 and 0.6 μg L−1, respectively.
The results of soil hydrophysical parameters modeling by neural networks are considered. Modern computing facilities using pedotransfer functions provide simplicity, speed and cheapening of obtaining soil characteristics by mathematical calculations. The initial data are the basic properties of the soil, which are stably determined. The analysis of errors in the calculation of hydrophysical parameter was conducted. Obtained neural networks most accurately reproduce hydrophysical parameters.
The sorption of the new insecticide cyantraniliprole was studied by the batch equilibrium method. The study of quantitative characteristics of cyantraniliprole sorption by the soils of different types showed that this process is well described by linear isotherms. According to obtained values of Koc, cyantraniliprole belongs to medium-mobility active substances of pesticides. The sorption value of cyantraniliprole was closely correlated with the content of organic carbon and clay. The regression equation of the dependence of Kd on soil organic carbon content was obtained.
Mobility of cyanthraniliprole, paclobutrazol and metribuzin was investigated on large lysimeters of the Experimental Soil Station of Moscow State University . Pesticides were applied in recommended and tenfold rates for cyantraniliprole and paclobuyrazol and recommended and eightfold rates for metribuzin. All three pesticides were detected in leachate. Cyantraniliprole was detected in most water samples analyzed. The maximum concentrations of cyanthraniliprole in the leachate were 2.6 and 12.5 µg L−1 in lysimeters with recommended and tenfold rates, respectively. Paclobutrazol was found 3 and 7 times during the year after application in the lysimeter with recommended and increased rates in concentrations up to 26 μg L−1. Used in accordance with the regulation, metribuzin in leachate was detected once, in eightfold rate - 73% of water samples; maximum concentration was 180 µg L−1. The migration risk into groundwater of all three studied pesticides is assessed as high, risk for people as low, risk for aquatic organisms as high. Risk and danger assessment based on simulation with model PEARL and mobility indexes showed high agreement with the assessment according to the experiment.
The water assembly of the MACRO model, making allowance regarding the double porosity of soils, was parameterized according to experimental laboratory data and tested according to the results of studying the water regime of sod-podzolic middle loamy soils of large lysimeters of MSU. Testing of pesticide migration models is necessary to improve forecast accuracy and justify their use. The analysis of the sensitivity, estimated from the data on the lysimetric runoff at the lower point (1.5 m) of the soil, showed that the WRC parameters are the main physical support of the models, which sets the forecast accuracy. These are the parameters that must be used to customize the model. The MACRO model has showed itself better at describing lysimetric runoff during the growing season by taking into account the fast flows along macropores and fissures that occur during periods of intense precipitation in the model than the models previously used.
The phenomenon of preferential migration of substances can increase the risk of pesticides. In the first year of the experiment, in 7 days after application cyantraniliprole penetrated to a depth of 25 cm in agrosoddy-podzolic soil. In the next year on the 7th day after application the pesticide was detected at a depth of 15 cm. The pesticide migrated deeper than the unconfigured PERL model took into account. The calibration of the PERL model by using experimental data (soil experimental support) allowed to reduce the error of prediction. The obtained data can be used to create new standard soil and climate scenarios for pesticide leaching models.
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