Evaluation of heavy metal toxicity in two Colombian agricultural soils using
2017
Luis E. Cortés | Francisco J. Martin | Margarita M. Sarria
This study aimed to determine the toxicity of Cu, Cd, Ni, Pb and Zn in two Colombian agricultural soils, Andisol and Vertisol, by bioassays with Lactuca Sativa and Vibrio fischeri. The metals were individually added to soils exceeding the intervention level of Andalusia. Subsequently, they were incubated at 25 °C and 60% humidity for 60 and 90 days, respectively. The experimental design was completely randomized with three replicates. After each incubation, the concentration of the metals in aqueous extracts was determined, and bioassays were carried out with Lactuca Sativa and Vibrio fischeri. Statistical analysis of results, post hoc comparisons (Tukey), correlations and principal component analysis were performed to find the factors that affected the organisms under study. It was found that Vertisol showed a higher immobilization capacity of all metals, based on their clay content and neutral pH, which was reflected in less toxicity on the organisms tested, indicating that this soil acted as a protection against mobility of pollutants in soil solution. The V. fischeri test presented greater sensitivity to contaminants, allowing a better discrimination of toxicity levels. The ability of both soils to inhibit toxicity increased over time, possibly through the interaction of metals with the different soil components, and the decrease in their mobility by mechanisms such as the formation of stable complexes, and was related to the increase of pH.
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