Comparison of three methods for measuring heavy metals in calcareous soils of Iran

The exact estimation of the heavy metals concentration in different soils is very important for determining the degree of soil contamination. This study was designed to determine the ability to extract heavy metals (As, Cd, Co, Cr, Cu, Mn, Ni, Pb, V and Zn) in calcareous soils using standard methods of digestion (ISO 14869-1, ISO 11466 and EPA 3050B) and the effect of lime on their extraction. In this study, 15 different soils with a wide range of chemical and physical properties and heavy metal concentrations and two reference materials were used. The results showed the percentage recovery in the reference material analyzed for the ISO 14869-1 method is between 94 and 107.8%, for the ISO 11466 method is between 90.3 and 101.7% and for the EPA 3050B method varied between 84.6 and 105.9%. The results showed that the recovery rate in the ISO 14869-1 method is better than the other methods (5% average for all elements). The results of natural soils were compared with total digestion method ISO 14869-1, and the efficiency of Cd extraction by ISO 11466 was between 61.25 and 97.12%. The extraction efficiency for As varied between 60.39 and 96.64%. The extraction efficiency for the Co, Cr, Cu, Mn, Ni, Pb, V and Zn elements was, respectively, between 71.2-96, 64.53-97.8, 66.07-96.3, 76.54-99.25, 79.3-100, 79.3-97.69, 73.43-95.30, and 73.7-99.9%. The extraction efficiency of Cd by the EPA 3050B method was between 60.25 and 96.34%. The extraction efficiency for As varied between 37.61 and 97.72%. The extraction efficiency for the Co, Cr, Cu, Mn, Ni, Pb, V and Zn elements varied between 46.32-72.46, 47.61-71.66, 44.84-86.55, 49.21-76.64, 76.95-96.73, 43.38-99.9, 43.17-81.12, and 45.83-72.69%, respectively. Based on the results, the ISO 11466 (Aqua regia) method is suggested as a suitable method for environmental studies in calcareous soils. The results showed that lime percentage has no effect on the recovery of the elements in calcareous soils.