Chlororganic pesticides migration in groundwater of southern Bahmutskyi basin

Abstract

Migration of organochlorine pesticides in groundwater, occurring in the process of general mass transfer in the area of hypergenesis in Bahmutskiy basin has been considered. Some of the main parameters of pesticide distribution system "soil - water" (water chemistry, particle size and mineral composition of soil, etc.) have been determined as well as their accumulation on geochemical barriers.

During field studies of pesticides migration in loamy-sandy soils a stable pattern of their increasing concentrations with the temperature growth in groundwater has been established.

It is established that the intensity of molecular diffusion of pesticides increases with increasing porosity of the soil system, soil moisture, temperature increase. It is noted that the significance of molecular diffusion for agricultural chemicals migration, including pesticides in the underground hydrosphere and, as a result - contamination of groundwater - should be considered only at short distances from the source of contamination.

It has been found out that the role of molecular diffusion can be very significant when calculating the pollution front moving on long distances calculated in kilometers. It is envisaged that diffusion mechanisms provide mass transfer between the cross-cutting and dead end pores in soils and between permeable and impermeable layers of mineral matter. Thus, in the first case diffusion slows the spread of pesticide pollution, and in the second case - on the contrary - it accelerates it. This is a universal model for heterogeneous (fractured-porous and layered) soils. It has been noted that in some soils homogeneous by structure and texture water migration of pesticides occurs according to a certain scheme of convection-diffusion mass transfer, but in the case of large filtration speeds the priority are hydro dispersion processes that by external signs resemble diffuse scattering.

Cyclical migration of organochlorine pesticides in groundwater has been established conditioned by physical and chemical properties of the soil, organochlorine pesticides themselves and sorption-desorption processes that take place in the system "soil - water".