Abstract

Agricultural practices and long-term application of phosphate and nitrogene fertilizers causes the accumulation of U and some heavy metals in the surface soil of agricultural fields. We investigated the soil constituents that contribute to the accumulation of U and some trace heavy metals. For this purpose, the concentrations of some rare earth element (REE) and trace elements collected from 17 sampling sites in the Çumra Basin were determined. The mean concentrations of La and Ce in surface soils was 33.8 and 65.4 mg/kg, respectively; in sediment, they were 32.7 and 61.8 mg/kg, respectively. The mean values of Mo, Cu, Pb, Zn, Co, Ni, Mn, As, Cd, U and Th were 0.69, 24.2, 19.4, 64.6, 16.2, 76.9, 593, 11.4, 0.24, 11.0 and 0.19 mg/kg, respectively, all of which were within the permitted levels according to national  Soil Pollution Control Regulation. High concentrations of Pb and Ni were observed in the soil compared to these sediments. The intensive N fertilization and agriculture activities have caused enrichment and slight environmental pollution for Ni (76.9 mg/kg) and Pb (19.4 mg/kg) in Çarsamba fan soils. Cultivated topsoil showed the same contents of U (2.0 mg/kg) and Cd (0.24 mg/kg) as in sediments. The results showed that successive application of phosphate fertilizer did not increase the concentrations of U and Cd in topsoil.

Key words: Çumra soil, enrichment/depletion, heavy metal, pollution, rare earth element.