Avaliação da presença de agrotóxicos por cromatografia líquida acoplada à espectrometria de massas em águas subterrâneas utilizadas para abastecimento público

Abstract

Due to contamination of waters by pesticides, especially the ones used for human consumption, the present work aimed to assess the presence of pesticides through liquid chromatography coupled to mass spectrometry (LC-MS) in groundwater used for public supply in a city of the Missões region in the State of Rio Grande do Sul. Therefore, water samples of twelve wells used for public supply in ten rural communities were evaluated, in which a water quality analysis was carried out through the physical-chemical parameters absorbance (λ - 254 nm), electric conductivity (μS cm-1), apparent color (uH), dissolved oxygen (mg L-1), pH, sedimentable solids (mg L-1), temperature (°C) and turbidity (uT), performing a comparison between the results and the values established by Portaria de Consolidação (PRC) N° 5/2017 of Ministério da Saúde (MS). In order to verify the seasonal variation of the water quality, four samples were made, one at each season of the year, and further the physical-chemical parameters were assessed, followed by a detection and quantification analysis, in two wells, of the pesticides: Atrazine; Azoxystrobin; Cyproconazole; Clomazone; Difenoconazole; Epoxiconazole; Fipronil; Imazethapyr; Malathion; Metsulfuron-methyl; Penoxsulam; Pyraclostrobin; Pirimicarb; Profenofos; Propanil; Propiconazole; Simazine and Tiabendazole in water samples via LC-MS. The results indicated a variability in the quality of the water for human consumption when the different seasons of the year were considered. The minimum and maximum values identified for the physical-chemical parameters were: temperature (18,8 to 25.6 º C), pH (7.63 to 9.52), turbidity (0.22 to 12 uT), apparent color (0 to 6.2 uH), electric conductivity (58.5 to 185 μS cm-1), dissolved oxygen (1.8 to 7.3 mg L-1), absorbance (0,001 to 0,064 λ - 254 nm) and sedimentable solids (0 to <0.1 mg L-1). Regarding to the pesticides, in the well A1 were identified: Malathion (0.207 μg L-1), Penoxsulam (1.665 μg L-1), Profenofos (2.114 μg L-1) and Propanil (1.138 μg L-1) in summer season, Azoxystrobin (0.067 μg L-1), Penoxsulam (1.189 μg L-1) and Propanil (2.113 μg L-1) in autumn, Atrazine (0.045 μg L-1), Azoxystrobin (0.141 μg L-1), Cyproconazole (0.009 μg L-1), Penoxsulam (0.682 μg L-1) and Propanil (2.107 μg L-1) in winter, and Atrazine (0.035 μg L-1), Azoxystrobin (0.111 μg L-1), Penoxsulam (0.774 μg L-1) and Propanil (1.445 μg L-1) in spring. In the well A2 were identified: Penoxsulam (0.357 μg L-1), Profenofos (1,765 μg L-1) and Propanil (0,46 μg L-1) in summer season, Cyproconazole (0.21 μg L-1) and Propanil (0.619 μg L-1) in autumn, and Cyproconazole (0.19 μg L-1), Fipronil (0.093 μg L-1), Penoxsulam (0.273 μg L-1) and Propanil (0.637 μg L-1) in winter, and Cyproconazole (0.014 μg L-1) and Pyraclostrobin (0.011 μg L-1) in spring. Although they were present, none of the pesticides presented concentration above the maximum limit established in PRC N° 5/2017 of MS.