Heavy metals in soils and sediments in the sugarcane area of southern Quintana Roo, Mexico

Abstract

In order to determine the heavy metals content and distribution in an area cultivated with sugarcane in the Río Hondo basin, southern Quintana Roo, Mexico, 10 samples of surficial sediments were collected from the main agricultural drain and 18 samples from soils developed on a karst aquifer. The samples were obtained on february 2016, during the dry season. Concentrations of Hg, Cd, Cu, and Fe and physicochemical parameters such pH, organic matter and cation exchange capacity were measured. In order to understand the distribution of the heavy metals, we performed descriptive statistics, Pearson correlation, analysis of variance, t test, principal component analysis and hierarchical clustering analysis. The mean concentration of heavy metals in soil, in descending order were: Fe > Cu > Cd > Hg with soil values of 25,334.13 mg∙kg-1, 10.56 mg∙kg-1, 0.55 mg∙kg-1 and 0.02 mg∙kg-1, respectively; the sediment values found were 19,952.68 mg∙kg-1, 8.00 mg∙kg-1, 0.54 mg∙kg-1 and 0.06 mg∙kg-1, respectively. The physical and chemical parameters were homogeneous within the study area. The origin of Hg, Cd and Cu concentrations could be anthropogenic. Although Fe is naturally found in the study area, it is possible that the current distribution of this metal is also due to agricultural activity. The main factor in the distribution of heavy metals in the agricultural soils of the sugarcane zone is the carrying of soil particulates caused by runoff, and the greater contribution of these pollutants to the agricultural drain occurs mainly by the entrainment of particulates from gleysol type soils.