Impact of Urea and Ammoniacal Nitrogen Wastewaters on Soil: Field Study in a Fertilizer Industry (Bahía Blanca, Argentina)

Abstract

Nitrogen compounds in industrial effluents are considered a serious threat to the environment. The aim of this work is to identify the effect produced by nitrogen-rich wastewater on alkaline soils from industrial land. Two plots were irrigated with wastewater as ammoniacal nitrogen (31 to 53 g N m−2) and urea (167–301 g N m−2) sources named P1 and P2, respectively. Inorganic nitrogen (N) concentrations (N-NH3 + N-NH4, N-NO2, N-NO3), soil pH, and N-NH3 volatilization were monitored during a 2-year period. Variations in the fate of N compounds were distinguished according to the quantity and source of N applied to the soil. A higher N input in the form of urea was related to a greater concentration of nitrates and soil acidification in the topsoil (0–30 cm). Otherwise, ammoniacal N wastewater showed greater relative ammonia losses due to volatilization. Ammonia losses were estimated as 24.2% and 7.43% of the total N applied in P1 and P2, respectively. Besides, in P1 ammoniacal N predominated over nitrate, unlike results obtained in P2. The correct management of nitrogen-rich wastewaters in fertilizer industries could greatly reduce soil and groundwater degradation.