Biochemical evaluation of the remediation of weathered and contaminated soil with heavy metals

Mining has been carried out in San Luis Potosi, Mexico, since 1592, which has led to severe pollution issues affecting both the environment and human health. To address this, remediation projects have been initiated to restore the soil and its ecosystem services. These efforts involve removing the contaminants and restoring the soil’s health and quality. This study aims to assess the biochemical impact of soil remediation carried out in the field, on areas that have been heavily contaminated with heavy metals over a prolonged period.

The enzymatic activity, physiological profile, structure, and microbial diversity were used as bioindicators to assess the remediation of soil and two reference soils.

The results indicated that Pb and As decreased, but not at levels indicated by Mexican regulations, Cd concentrations decreased to be below Mexican regulations, the enzymatic activity between the soil with and without remediation did not present significant differences, both with low activity, arylsulfatase was the one with the highest inhibition, and urease the most activated. The evolution of the physiological activity of the microorganisms was greater in the remediated soil. Normal values of evenness and diversity were observed in soils with and without remediation, likewise, the consumption of substrates initially was towards carbohydrates and amines/amides, but in the end, carboxylic acids and polymers were consumed.

The remediation process shows positive results; the recovery of soil health is in progress. It was demonstrated that the bioindicators used were adequate to evaluate the soil remediation process.