Ocorrência de Pesticidas no Solo Cultivado com Cebola no Vale do Submédio São Francisco – Brasil

Resumo

The extensive and disorderly use of pesticides in agricultural production raises concerns about food and
environmental security. A multi-residue method was validated to detect and quantify pesticide residues
used in onion cultivation in the Submédio São Francisco Valley using the QuEChERS method and
quadrupole UPLC/MS analysis. The method was validated with good linearity (R² > 0.9991), recoveries
ranging from 77 to 120%, and with a relative standard deviation (RSD) of up to 8%. The limits of
detection (LOD) ranged from 0.12 to 39 µg kg^-1 while the limits of quantification (LOQ) ranged from
0.40 to 1.32 µg kg^-1. This method is capable of quantifying pesticide residues of acetamiprid, carbofuran,
dimethoate, fenarimol, imidacloprid, metalaxyl, methomyl, tebuconazole, and thiamethoxam. The method
was applied to 90 samples of onion growing soils collected in different periods. The fungicide fenarimol
represents the highest occurrence, being quantified in 88 samples analyzed with concentrations ranging
from 0.30 to 4.30 µg kg^-1. The insecticide thiamethoxam was the compound that presented the highest
levels, being found in thirteen samples with concentrations ranging from 0.60 to 65.60 µg kg^-1. Results of high concentrations of substances were obtained in soil samples from Juazeiro, Bahia. Bartlett’s sphericity
test ruled out the null hypothesis of the correlation between the physicochemical characteristics of the
soil and the concentration of the compounds. Principal component analysis (PCA) was applied to explain
the variability of the results, being possible to affirm that the persistence of the compounds in the soils
is directly related to its fraction of clay and silt.