Diffuse pollution sources of groundwater in an intensive agricultural area in Southern Bulgaria

The monitoring was conducted of groundwater and surface water in the period of 2018-2019 year, on Tsalapitsa village, near city of Plovdiv on Аlluvial-meadow soil (Fluvisol). In the scheme of study were included different land use, which reflect the great variety from loading in agroecosystems under agricultural activities - orchards, vineyards, rice fields, fields, where are grown cereals and intensive crops (diffuse or nonpoint sources). Water samples from wells in the pilot survey site were taken twice a year. It was found that the waters from wells under arable lands were characterized in most cases by alkaline reaction and content of chemical elements under or near to the maximum permissible concentration for drinking water. It was established that most of the studied elements are influenced by anthropogenic load and different land use, especially when growing vegetables. Data show that the nitrate nitrogen content in the shallow groundwater varies in a wide range, depending on the location of the studied wells. It was found that change in the nitrate concentrations depending on the land use is in the following order - vegetable crops > rice fields > arable fields > orchards etc. It‘s necessary conducting long-term monitoring to understand the dynamics and transformation of nitrogen in waters and the ongoing complex biochemical processes in the agro-ecosystem, especially in vulnerable areas with soils that are light in mechanical composition, shallow groundwater and with intensive agricultural activity.