Total and extractable nickel and cadmium contents in natural soils
2005
Caridad-Cancela, R. | Paz-Gonzalez, A. | Abreu, C.A de
Trace element analysis in natural soil provides information on background levels, which may be also useful to detect anthropogenic inputs. The main objective of this study was to provide background levels of Cd and Ni for natural soils in Galicia (Spain). Ten natural soil profiles, representative of different parent material with a wide range of elemental composition, including ultramafic rocks such as serpentine, were selected in this region. All samples were digested with nitric acid in a microwave oven (U.S. EPA-SW 846 305 1 method) to assess "total" Cd and Ni contents. Trace element extractions were carried out with diethylenetriaminepentaacetic acid (DTPA) and Mehlich-3. All analyses were performed by ICP-AES. Soil Cd concentrations obtained by the U.S. EPA method ranged from <0.01 to 4.42 mg kg(-1), with an average of 2.03 mg kg(-1), and Ni concentrations ranged from 12.66 to 2066 mg kg(-1) with an average of 156 mg kg(-1). The mean Ni content was higher, because the used sample included a soil that was developed over serpentine. The DTPA-and Mehlich-3-extractable Cd and Ni average levels were 0.06 and 8.78 mg kg(-1) and 0.16 and 3.57 mg kg(-1), respectively. Nickel levels obtained by both extractants were highly correlated (r2 = 0.91). A correlation analysis between total and extractable Cd and Ni form, and soil general properties showed that the highest significant dependence was for Cd(DTPA) vs. organic matter content and CEC.
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