Dynamics of the Chemical Composition of Precipitation and Input of Elements in an Agricultural Area in Southern Bulgaria

The study of the chemical composition of precipitation is an important factor in determining the input of elements and the total anthropogenic load in agroecosystems. The study presents the results of a 4-year monitoring of the chemical composition of precipitation from the area of the experimental field Tsalapitsa, Plovdiv on Alluvial-meadow soil (Fluvisol). The effects of chemical elements imported with the atmospheric deposition on vulnerable soils in an intensive agricultural practice were evaluated. The data showed that the investigated precipitations are characterized by a slightly acidic to neutral reaction. A significant seasonal and annual variation of the elements in them was observed, with a higher coefficient of variation reported for cations and nitrogen (61- 68%). As a result of the conducted research, the following order of change in the concentrations of cations - Ca2+>NH4 + >Mg2+>K+ >Na+ and of anions - SO4 2- > HCO3 - >Cl- >NO3 -N in precipitation was established. The significant correlation found between Ca2+ and Mg2+ (r=0.92; 0.97) and the weak one between NH4 + , NO3 -N and SO4 2- suggest a buffer factor against precipitation acidity, and anions concentrations did not represent a risk for a direct negative impact on the soil and the crops grown in the area.