Assessment of Heavy Metal Contamination in Agricultural Soils with Organic and Inorganic Production Systems in Cunduacán, Tabasco, Mexico

Cocoa cultivation is the main economic source for small and large farmers in Tabasco. However, cocoa production has decreased recently due to financial, edaphic, and nutritional factors. Therefore, this study aimed to measure the concentration of heavy metals (HM) in agricultural soil. To achieve this, two polygons (P1 and P2) were selected to evaluate the environmental impact of the agricultural production system used in each polygon. The pH (hydrogen potential), OM (organic matter), apparent density (AD), real density (RD), porosity (PO), clay (C), silt (ST), sand (S), and field capacity (FC) of the examined regions were also determined. In addition, a solid waste landfill (SWLF) was included as a third sampling site (P3). This is because it is a source of contamination of the surrounding cocoa-growing areas (P1 and P2). According to Mexican standards NOM-147-SEMARNAT and NOM-021-SEMARNAT-2000, the heavy metals that exceeded the permissible limits were Cd > Ni > V for P1, Cd for P2, and Cd for P3, with significant dif ferences between polygons. The highest level of Cd was determined in P3; therefore, the concentration of Cd in P1 and P2 is associated with the use of agrochemicals and the dragging of soil particles due to the topographic position of P3.