Characterisation of floriculture soil contaminated by the frequent use of organophosphorus pesticides and quantification of pesticide methamidophos

In this study, an analysis of floriculture soil was made in Villa Guerrero, State of Mexico, to evaluate which parameters could be modified by the constant use of organophosphorus pesticides and other agrochemicals; also the concentration of methamidophos, an organophosphate pesticide widely used in the area for insect control, was determined. Sampling was taken from sown and non-sown soil at a depth of 20 cm. The parameters analysed were texture, bulk density, surface area, pore size, conductivity, nitrogen, carbon, metals, pH, organic matter and C/N ratio. The surface area and pore size were determined by the BET (Brunauer, Emmett and Teller) equation, metal and methamidophos concentration were quantified by atomic absorption spectrometry (AAS) and high-performance liquid chromatography (HPLC), respectively. The rest of the measurements were made based on the Mexican norm NOM-021-SEMARNAT-2000. The soil was classified as the organic-volcanic loam type according to the texture and the bulk density analysis. In addition, BET analysis results showed a surface area of 79.74 m2 g−1 and an average diameter pore size of 4.13 nm. Compared to the non-sown soil, some sown soil parameters changed; there were increments in conductivity from 3.73 to 105.30 dS m−1, total nitrogen from 0.17% to 0.22%, carbon total from 2.09% to 3.71%, and Cu from 19.23 to 23.22 mg kg−1; and decrement of values was observed in pH from 5.33 to 4.60 pH units, organic carbon from 2.06% to 1.84%, C/N ratio from 12.12 to 8.36 and Zn from 75.34 to 63.02 mg kg−1. Finally, methamidophos pesticide was found only in sown soil at a concentration of 80 ± 11 mg kg−1. Results show that values were modified in most evaluated parameters by the frequency of agrochemicals use.