Evaluación de la degradación del plaguicida metamidofos por por cepas bacterianas aisladas de suelo florícola del Estado de México.

Abstract

Methamidophos, considered one of the most toxic insecticides, is used to control insects and mites in intensive crops such as floriculture. Given the indiscriminate use of this and other organophosphorus pesticides in the floricultural zone of the State of Mexico, its accumulation can cause environmental deterioration, and consequently, affect the survival of species that are not target organisms. In this project, it was proposed to degrade methamidophos by means of bacterial strains isolated from the floricultural soil of Villa Guerrero. Additionally, it was evaluated which parameters are modified in the soil by the constant use of organophosphorus pesticides and other agrochemicals. The quantification of methamidophos was performed by HPLC, sampling and soil analysis according to the NOM-021-SEMARNAT-2000. Five Gram negative bacterial strains were isolated from a Gerbera jamesonii greenhouse, capable of degrading a concentration of 200 mg L-1 of methamidophos. A máximum removal percentage of 58.05% was obtained using the bacterial consortium, in ten days of testing, at a pH of 7.0 and a temperature of 35 ° C. When dextrose was used as an additional source of carbon, the percentage of degradation of the pesticide increased to 92.03% under the same conditions.The isolated strains were identified by PCR of end point as belonging to Enterobacter, Pseudomonas, Shinella, Pseudochrobactrum and Brevundimonas. The results of the parameters of soil that is currently being cultivated with respect to the one that has not been sown were contrasted, it was observed that increase values of conductivity (3.73 to 105.30 dS m-1), total nitrogen (0.17 to 0.22 %), total carbon (2.09 to 3.71 %), and decrease pH (5.33 to 4.60 pH units), organic carbon (2.06 a 1.84 %) and the C / N ratio (12.12 to 8.36). The pesticide methamidophos was found in soil grown at a concentration of 80 ± 11 mg Kg-1. The results show that the values are modified in most of the parameters evaluated by the frequent use of agrochemicals, and that the degradation of methamidophos with the bacterial consortium is favored if an additional source of carbon is used.