RESULTS OF FIELD STUDIES ON NITROGEN AND PHOSPHORUS INPUT FROM AGRICULTURAL PRODUCTION TO SELECTED WATER BODIES IN WESTERN DVINA

In 2017 a field study of water bodies in Nevel and Usvyatsky Districts of Pskov Region was aimed to give qualitative and quantity estimation of the impact of local large-scale pig enterprises on the status of water bodies in the Western Dvina river basin. Water samples were taken and the flow was measured on the vulnerable areas and outside the farm impact area in accordance with an elaborated programme and methods of field measurements. Soil samples were collected from the fields, where liquid pig manure was applied. The results showed that on the local level, in the vicinity of these fields, the water bodies featured high levels of main manure pollution indicators - ammonium nitrogen and phosphorous. The concentration of ammonium varied from 4.4 to 32.7 mg.l(-1) at these points that was several hundred times higher than that in water bodies in natural areas; the concentration of dissolved phosphorus varied from 0.11 to 0.23 mg.l(-1) that was several times higher than the background values. The concentration of these elements was dropping down to the background level with the distance from the fields as the result of self-purification and dilution processes owing to natural conditions, associated mainly with the presence of wetlands.