Saturated and unsaturated hydraulic conductivity as a function of a thermodynamic potential (pressure) of soil water K(P) are investigated in the sandy samples with admixtures of strongly swelling polymer hydrogels (SSPHs) in a wide concentration range from 0.01 to 0.3 %SSPHs. The author’s original centrifugation method has been used along with a kinetic model of the water removal process, which enables to determine the function of water conductivity of gel compositions operating in an unsteady state. In saturation state and within the range of low absolute values of soil water pressure |P| = 0.3-20 kPa the SSPHs significantly (2-10 up to 50 times) reduced the hydraulic conductivity in proportion to the dose of a superabsorbent. A heterogeneous layered structure with a layer of pure gel or gel composition 0.1-0.3% SSHP reduces the saturated conductivity by 10-80 times.In the range | P | = 100-3020 kPa, the K(P) function, on the contrary, strongly increased up to 10–20 times under the action of SSPHs. The calculation of K(P) using the Mualem theory disagrees with our experimental estimation, especially in a range of low water content, where such a calculation strongly (up to 100-1000 times) underestimates the values of K(P).
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.
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.
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