Isotherms of Adsorption of Heavy Metals in Soils and Sediments of the La Villa River Basin-Panamá

Abstract

The study was carried out within the La Villa river basin (Herrera and Los Santos provinces). In these lands, great agricultural activity is developed, highlighting the production of corn, tomatoes, melons, watermelon, beans, peppers, sugarcane, meat and milk livestock. They are subjected to intensive use of agrochemicals and influenced by discharges of by-products from some industrial and agro-industrial companies located within the basin. The objective of the study was to determine by means of Langmuir isotherms the maximum adsorption of Mn, Zn, Cu, Pb and Cd in soils and sediments of areas with intensive agricultural activity within the La Villa river basin. Five soil and sediment samples were taken from producer´s farms in the rainy season (June-November 2016) and five samples in the dry season (January-April 2017). The total concentration of the heavy metal was determined. The isotherms of the trace metals in soils and sediments were determined in the samples taken at both times of the year by applying different concentrations of the metal in a CaCl2 0.01 M solution. High levels of Cu were found in soils and Cu, Mn, Cr and As in sediments. The Mn isotherm showed low values ​​and low adsorption force, Cu and Zn showed high adsorption values, but with low retention force. For Pb, high adsorption values ​​were observed, but very low retention force in the dry season, contrary to Cd, which obtained low adsorption values, but with a higher force. This behavior is closely related to the texture of the soils. The Cu, Zn and Mn showed high significant correlations with the clay content in the soil, contrary to the pH and the organic matter did not obtain a good correlation with the adsorption of the metals.