| Popis: |
Soil contamination with potentially toxic metals (PTMs) in the agricultural areas developed on open aquifer systems can be an environmental problem. The subject of this study is Gleysol and Fluvisol in the area of Podravina region, NE Croatia. The aim of this research was to determine the geochemical and mineralogical soil properties and accumulation or mobilisation of PTMs in Gleysol and Fluvisol under agricultural activities, and their possible influence on the shallow groundwater developed at the locations Kalinovac-Hrastova Greda and Podravske Sesvete. Within each of the soil types samples were collected to a depth of 200 cm with an Eijkelkamp auger set for soils. Samples were obtained from 0-20 cm, 20-40 cm, 40-70 cm, and 70-100 cm depth in Gleysol ; and from 0-40 cm, 40-70 cm, 70-100 cm, 100-140 cm, 140-170 cm, and 170-200 cm depth in Fluvisol, based on visible macrofeatures and field estimation of the granulometric and mineralogical changes along sampling depth of each soil type. The laboratory analysis of soil samples includes: pH, electrical conductivity (EC), soil texture, cation exchange capacity (CEC), sequential extraction analysis (BCR) of: As, Cu, Zn and Cd, and mineralogical analysis using X-ray diffraction (XRD). The sequential extraction analysis was performed according to the BCR procedure and proportions of elements were determined in four fractions: (1) carbonate (CARB), (2) the fraction of Fe-Mn oxyhydroxides (FEMN), (3) organic-sulphide (OR/SUL), and (4) residual fraction (RES). The Gleysol is slightly acidic in the upper 70 cm soil, while it is considerably acidic at the 70-100 cm depth. In the case of Fluvisol, pH is slightly acidic throughout the entire thickness of soil. Soil texture in Gleysol is silt loam, while in Fluvisol it is sandy silty loam. CEC is in line with soil texture for both analyzed soils. XRD analysis on fraction less than 2 μm showed that major mineral phases in Gleysol are goethite and vermiculites, smectites, while Fluvisol mostly consists of chlorites, kaolinites, vermiculites and smectites. The maximum As concentration in Gleysol is 526 mg/kg, which is determined in the topsoil (0-20 cm) in RES fraction. After RES, the OR/SUL fraction is the next most represented. The same trend is found for Zn and Cu in Gleysols. The maximum As concentration in Fluvisol is 75 mg/kg, which is determined in the topsoil (0-40 cm) in RES fraction, while FEMN fraction is the next most represented. The concentration of other analysed metals (Zn and Cu) increase with soil depths for all fractions. Cadmium is not detected in investigated soils. It can be concluded that in the case of Gleysol, influence of agricultural activities is recognized, with the effect decreasing PTMs concentration after approximately 70 cm depth, which is not similar for Fluvisol except for As. |
