Assessment of the potential toxicity of metals in soil near the Tungurahua volcano, Ecuador

Abstract

The activity of the Tungurahua volcano in 2016 caused ashfall and lava episodes, primarily concentrated in Quero. The total metal content and their bioavailability were assessed in an agricultural soil near this volcano. The total metal content was estimated using microwave-assisted acid digestion, and the bioavailable metals were determined by EDTA extraction. The major metals were measured using flame atomic absorption, while the trace metals were measured with graphite furnace atomic absorption. The total content of Cd (0.13-0.22 mg/kg), Pb (1.3-2.5 mg/kg), Co (2.1-5 mg/kg), Ni (9.4-15.4 mg/kg), Cu (15.5-20.5 mg/kg), and Zn (27-36 mg/kg) were below the values established in Ecuadorian regulations. In contrast, Sr (5.1-11.3 mg/kg), Mn (138-216 mg/kg), Fe (5537-9426 mg/kg), Mg (1065-3128 mg/kg), and K (79-147 mg/kg) were comparable to other volcanic soils. In conclusion, the studied soils are not potentially toxic for agricultural practices concerning metal content.