Quantitative Estimate of the Heterogeneity of Solute Fluxes Using the Dispersivity Length for Mathematical Models of Pesticide Migration in Soils

Mathematical models of solute movement in soils are used as management means for assessing the migration of agrochemicals and calculating environmental risks. In these models, the soil block includes the soil values of dispersivity length or solute diffusivity as one of the main parameters. Under laboratory conditions, this parameter was determined experimentally in soil columns by recording the dynamics of the effluent concentration and solving inverse problems. A direct experimental method of field determination based on the movement of marker solution was tested. For the prediction, risk calculation, and management of pesticide application using physically based mathematical models, the following stepwise procedure is recommended: (1) model parameterization based on experimental soil properties; (2) use of the field dispersivity length, which was 3–11 cm for the 0- to 40-cm layer, exceeded 12 cm for deeper fissured BEL and BT (40- to 60-cm) horizons with prismatic structure, and had a median value of 21 cm in layers below 60 cm in experiments on an agrosoddy-podzolic soil (Eutric Albic Glossic Retisol (Abruptic, Loamic, Aric) (WRB, 2014) from Moscow oblast.     

Sensitivity assessment,adjustment, and comparison of mathematical models describing the migration of pesticides in soil using lysimetric data

The water block of physically founded models of different levels (chromatographic PEARL models and dual-porosity MACRO models) was parameterized using laboratory experimental data and tested using the results of studying the water regime of loamy soddy-podzolic soil in large lysimeters of the Experimental Soil Station of Moscow State University. The models were adapted using a stepwise approach, which involved the sequential assessment and adjustment of each submodel. The models unadjusted for the water block underestimated the lysimeter flow and overestimated the soil water content. The theoretical necessity of the model adjustment was explained by the different scales of the experimental objects (soil samples) and simulated phenomenon (soil profile). The adjustment of the models by selecting the most sensitive hydrophysical parameters of the soils (the approximation parameters of the soil water retention curve (SWRC)) gave good agreement between the predicted moisture profiles and their actual values. In distinction from the PEARL model, the MARCO model reliably described the migration of a pesticide through the soil profile, which confirmed the necessity of physically founded models accounting for the separation of preferential flows in the pore space for the prediction, analysis, optimization, and management of modern agricultural technologies.     

Hydrosorption and Microstructural Characteristics of Soil Horizons of Different Geneses and Their Change in Constructozems

Eurasian Soil Science - Soil substrates used in model constructozems (artificially constructed soils) of different fabrics created on the territory of Lomonosov Moscow State University in 2012 were...