Determinação de espécies metálicas em solo

Abstract

Soil is an extremely important natural resource, but its quality can be compromised by contamination from metallic species, which have both natural and anthropogenic origins. Almost all metallic species have the potential for toxicity and can easily accumulate in the soil due to their non-biodegradability. However, soil is a complex matrix influenced by factors such as organic matter content, ionic exchange, pH, and granulometry. In this context, it is necessary to find experimental methodologies for sample preparation, as well as calibration methods that provide results close to reality. The objective of this work was to determine the most efficient digestion method between conventional digestion using a heating plate and digestion using microwave assistance, as well as to compare external calibration methods and standard addition in the assessment of metallic species in soil. The metals studied were cobalt, nickel, and lead. The soil sample from the Assentamento Contestado, located in the city of Lapa/PR, was dried, sieved, and subjected to organic matter combustion following EMBRAPA 1979. Extraction was performed in two ways: (i) using a heating plate and (ii) sing a microwave, with quantification by ICP-OES. For the addition/recovery study, a standard solution of metallic species was added. Both conventional and microwave digestion methods were efficient, but the use of microwaves was faster and more economical. The recovery study presented unsatisfactory results, likely due to external calibration, which is not suitable for complex matrices. The next step was to compare external calibration methods and standard addition, using certified soil LGCQC3004. Extraction was performed using microwaves, due to its previous performance. The calibration curves showed matrix effects, indicating that the appropriate method is standard addition calibration. The addition/recovery study was compatible with the expected range of 90% to 120% for all metals in the certified soil. It concludes that soil is a complex sample that influences calibration methodology.