Concentración de metales pesados en suelos de cacao a dos profundidades en 4 fincas del cantón santa rosa, 2023

Abstract

In Ecuador, the presence of heavy metal contamination in the soils of cocoa plantations has been confirmed by analysis, showing high levels of these elements in land used for cocoa cultivation in various provinces of the country. Heavy metals, such as Cd, Pb, As and Hg, are naturally occurring or anthropogenic compounds. However, one of the main causes of soil contamination in cocoa plantations lies in mining activities and the excessive use of pesticides, which triggers the presence of these metals in harmful concentrations that lead to soil degradation. The main objective of this titration work was to evaluate the levels of heavy metals in two different soil depths. This study involved the collection of samples composed of 12 subsamples following a zigzag pattern at depths of 0-30 cm and 30-60 cm in four farms that use water from rivers for irrigation contaminated by mining and a reference point that is far from the sources of mining contamination. The PM analysis was performed in duplicate to minimize random error, the samples were subjected to a pretreatment process, which included drying at 25°C for 72 hours, crushing and passing through a sieve at 2 mm, preparing them for subsequent atomic absorption analysis. In addition, the maximum allowable limits according to national (TULSMA) and international (European Communities and U.S. Standard) regulations were compared. The results obtained in the laboratory revealed that the predominant metal was As in farm 3, both at a depth of 0-30 cm (20.3 mg/kg soil) and at a depth of 30-60 cm (16.7 mg/kg soil). Similarly, elevated As concentrations were found on farm 4, with 19.3 mg/kg soil at a depth of 0-30 cm and 17.2 mg/kg soil at a depth of 30-60 cm. Also, it was observed that soil pH in farm 2 recorded values of 5.23 at a depth of 0-30 cm and 5.13 at a depth of 30-60 cm, indicating significant soil acidity. Therefore, it is essential to continue conducting analyses on farms 3 and 4, given the alarming presence of elevated As levels. This raises the possibility that the cocoa plantation soils are experiencing degradation and inhibition of normal plant growth and development, which could negatively affect future harvests. Based on these findings, the importance of constant monitoring and evaluation of soil quality on these farms is emphasized in order to implement appropriate mitigation and preservation measures.