Determinação do pesticida 2,4-D e produtos de degradação de herbicidas ácidos em águas superficiais e subterrâneas : desenvolvimento, validação e aplicação

• Ano de defesa: 2020
• Autor(a) principal: Tessaro, Leticia Louize Gonçalves
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Mato Grosso; Brasil; Instituto de Ciências Exatas e da Terra (ICET); UFMT CUC - Cuiabá; Programa de Pós-Graduação em Química
• Palavras-chave em Português: 2,4-D; SPE; CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA
• Link de acesso: http://ri.ufmt.br/handle/1/2690

Mato Grosso is the second Brazilian state that most uses pesticides, due to its high agricultural production, mainly of soybean, corn and cotton crops. The second most used pesticide in the country is 2,4-dichlorophenoxyacetic acid (2,4-D). The World Health Organization (WHO) classifies the herbicide 2,4-D as low toxic, being harmful if ingested or inhaled, however, the degradation products of acidic pesticides such as 2,4-dichlorophenol (2,4-DCF), 4-chlorophenol (4-CF), 4-chloro-2-methoxybenzene (2,4-DCA) and 4-chloro-2- methylphenol (4C2MF), from microbial degradation or photolysis, are considered to be highly toxic, and may possibly cause cancer, have a mutagenic effect and affect development. In view of the above, an analytical method was developed, using extraction in solid dispersive phase (D-SPE) and liquid chromatographic coupled to mass spectrometry in sequence to determine and quantify these analytes in surface and ground water samples. Grab sampling was used to monitor the presence of these analytes in waters close to farms with intense agricultural cultivation and which are highly vulnerable to contamination. Two points were selected for surface water sampling and 2 points for samples of the phreatic aquifer, in three micro-basins located in the municipalities of Rondonópolis, Jaciara and Campo Verde and also 7 points for surface water sampling, 2 points for ground water collection and 3 points for samples of the water table in the municipality of Diamantino. For grab samples, the D SPE method was validated, obtaining recoveries between 49 and 116% and precision with relative standard deviation (DPR) below 20%, method detection limits (LDm) for the analytes 2,4- D and 4C2MF of 0.13 and 0.20 µg L-1 , respectively, below the maximum value established by current legislation for 2,4-D. The monitoring period for the grab samples was from September / 2019 to June / 2020, totaling 10 months and 110 samples collected. During the entire monitored period the analytes were not detected in the surface and groundwater samples. In order to verify the possibility of using passive sampling to monitor these analytes, different adsorbent phases and extraction methods were tested. The best results were obtained using C18 as the adsorbent phase and 10 mL of methanol as the extractor solvent. The extraction of the analytes from the passive sampler solid phase using the D-SPE method for 2,4-D, 4-CF and 4C2MF showed recoveries between 40 and 91% and precision with DPR <20%. The period of 7 days for exposure of the passive samplers in the field proved not to be long enough, since there was no detectable retention of any of the validated analytes, with the need for a study with a longer exposure time in order to analyze the viability of the POCIS sampler for environmental matrices. The use of the passive sampling technique is a great ally to the monitoring work because it acts more completely when compared to the grab sampling, since it allows to estimate the concentration of the analytes during its exposure period. Therefore, the method can be used to determine 2,4-D and 4C2MF in surface and groundwater samples using grab sampling and additional studies shall be carried out in order to determine the appropriate exposure time for passive samplers.