Evaluation of trace elements contamination in agricultural soils in southwest of Guanajuato, Mexico

The aim of this study was to evaluate the contamination index of 18 agricultural soil samples in the southwest of Guanajuato by carrying out an analysis of the total trace element concentrations (arsenic [As], cadmium [Cd], chrome [Cr], copper [Cu], lead [Pb] and zinc [Zn]) with the use of Inductively Coupled Plasma Optical Emission Spectrometry and the geoaccumulation index (I geo ). The trace element concentration ranges of As (<0.009 mg kg -1 - 14.97 mg kg -1 ), Cd (0.06 mg kg -1 - 0.76 mg kg -1 ), Cr (11.31 mg kg -1 - 33.85 mg kg -1 ), Cu (<0.004 mg kg -1 - 99.98 mg kg -1 ), Pb (4.87 mg kg -1 - 41.79 mg kg -1 ) and Zn (21.98 mg kg -1 - 109.44 mg kg -1 ) were below the total reference concentration compared to the Mexican Official Norm NOM-147-SEMARNAT/SSA1-2004 (DOF, 2007). In regard to the I geo , As, Cu, Pb and Zn presented concentrations ranging from uncontaminated to moderately contaminated categories (Class 0, 1 and 2) while the soils were uncontaminated by Cr (Class 0). On the other hand, the Cd showed the highest I geo (Class 3: moderately to heavily contaminated).