Nowadays, several researchers have been warning about the problems caused by the use of agrochemicals in Brazil and worldwide. However, the usage of these compounds are increasing in order to control the integrity of plantations. In this context, the objective of this work is to evaluate the presence of pesticides by liquid chromatography coupled to mass spectrometry in rural water supply wells in Cerro Largo state of Rio Grande do Sul. Samples from twelve artesian wells were analyzed and the water quality was evaluated by considering the following physical-chemical parameters: absorbance (? - 254 nm), electrical conductivity (mg L-1), apparent color (uH), dissolved oxygen (mg L-1), pH, sedimentable solids (mg L-1), temperature (?C) and turbidity (uT). The results obtained were compared to a regulatory system, Portaria da Consolida??o (PRC) No 5/2017 in Ministry of Health (MS). Four collections were carried out, one in each season of the year, the physical-chemical parameters were analyzed followed by analysis in two detection wells and quantification of the presence of pesticides. The agrochemicals monitored in water samples using CLAF-EM were: Atrazine, Azoxystrobin, Cyproconazole, Clomazone, Diphenoconazole, Epoxiconazole, Fipronil, Imazapyr, Malathion, Metsulfuron-methyl, Penoxsulam, Pyraclostrobin, Pirimicarb, Profenofos, Propanil, Propiconazole, Simazine and Tiabendazole. Concentrations varied between 0.013 to 8.864 ?g L-1. The agrochemicals detected in well 1 in summer season were: Azoxystrobin (0.030 ?g L-1), Fipronil (0.211 ?g L-1), Metsulfuron-methyl (0.374 ?g L- 1), Penoxsulam (1.729 ?g L-1), Profenofos ( 1.958 ?g L-1) and Propanil (8.864 ?g L-1); in fall season: Atrazine (0.040 ?g L-1), Azoxystrobin (0.396 ?g L-1), Penoxsulam (0.648 ?g L-1) and Propanil (0.881 ?g L-1); in winter season: Metsulfuron-methyl (0.557 ?g L-1) and Propanil (1.602 ?g L-1); and in spring season: Atrazine (0.050 ?g L-1), Azoxystrobin (0.170 ?g L- 1), Fipronil (0.085 ?g L- 1), Penoxsulam (0.866 ?g L-1) and Propanil (0.679 ?g L-1). The substances found in well 2 during summer were: Cyproconazole (0.110 ?g L-1), Epoxiconazole (0.006 ?g L-1), Malathion (0.649 ?g L- 1), Penoxsulam (0.374 ?g L-1) and Pyraclostrobin (0.157 ?g L-1); in fall season: Atrazine (0.031 ?g L-1), Azoxystrobin (0.143 ?g L-1), Fipronil (0.085 ?g L-1), Metsulfuron-methyl (0.150 ?g L-1) and Penoxsulam (0.063 ?g L-1); in winter: Atrazine (0.015 ?g L-1), Azoxystrobin (0.068 ?g L- 1), Fipronil (0.085 ?g L-1), Imazapyr (0.027 ?g L-1) and Penoxsulam (0.063 ?g L-1); and in spring: Azoxystrobin (0.170 ?g L-1), Diphenoconazole (0.029 ?g L-1), Fipronil (0.085 ?g L- 1) and Penoxsulam (1.231 ?g L-1). Even though detected, the quantities of agrochemicals did not surpassed the regulatory system stablished in PRC N? 5/2017.Hoje em dia, diversos pesquisadores v?m alertando sobre os problemas causados pelo uso de agrot?xicos no Brasil e no mundo. No entanto, cada vez mais estes compostos s?o utilizados para o controle da integridade das planta??es, sendo assim o objetivo do trabalho ? avaliar a presen?a de agrot?xico por cromatografia l?quida acoplada ? espectrometria de massas em po?os de abastecimento de ?gua rural, no munic?pio de Cerro Largo no Estado do Rio Grande do Sul. Foram analisados amostras de ?gua de doze po?os artesianos que s?o utilizados para o abastecimento p?blico, e avaliado a qualidade da ?gua em rela??o aos par?metros f?sico-qu?micos: absorv?ncia (? - 254 nm), condutividade el?trica (?S cm-1), cor aparente (uH), oxig?nio dissolvido (mg L-1), pH, s?lidos sediment?veis (mg L-1), temperatura (?C) e turbidez (uT), realizado a compara??o entre os resultados obtidos e os valores estabelecidos na Portaria de Consolida??o (PRC) N? 5/2017 do Minist?rio da Sa?de (MS). Foram realizadas quatro coletas, um em cada esta??o do ano, analisou-se os par?metros f?sico-qu?micos seguido de an?lise em dois po?os de detec??o e quantifica??o da presen?a dos agrot?xicos. Para tanto foram monitorados 18 agrot?xicos: Atrazina, Azoxistrobina, Ciproconazol, Clomazona, Difenoconazol, Epoxiconazol, Fipronil, Imazepir, Malationa, Metsulfuron- metilico, Penoxsulam, Pirasclostrobina, Pirimicarbe, Profenofos, Propanil, Propiconazol, Simazina e Tiabendazol em amostra de ?guas, por meio de (CLAF-EM). Com concentra??es que variaram de 0,013 a 8,864 ?g L-1. Em rela??o aos agrot?xicos identificou-se a presen?a no po?o 1 de Azoxistrobina (0,030 ?g L-1), Fipronil (0,211 ?g L-1), Metsulfurin-metilico (0,374 ?g L-1), Penoxsulam (1,729 ?g L-1), Profenofos ( 1,958 ?g L-1), Propanil (8,864 ?g L-1) referente a esta??o do ver?o, Atrazina (0,040 ?g L-1), Azoxistrobina (0,396 ?g L-1), Penoxsulam (0,648 ?g L-1), Propanil (0,881 ?g L-1) referente a esta??o do outono, Metsulfuron-metilico (0,557 ?g L-1), Propanil (1,602 ?g L-1) referente a esta??o do inverno, Atrazina (0,050 ?g L-1), Azoxistrona (0,170 ?g L-1), Fipronil (0,085 ?g L-1), Penoxsulam (0,866 ?g L-1), Propanil (0,679 ?g L-1) referente a esta??o da primavera. No po?o 2 Ciproconazol (0,110 ?g L-1), Epoxiconazol (0,006 ?g L-1), Malationa (0,649 ?g L-1), Penoxsulam (0,374 ?g L-1), Piraclostrobina (0,157 ?g L-1) referente a esta??o do ver?o, Atrazina (0,031 ?g L-1), Azoxistrobina (0,143 ?g L-1), Fipronil (0,085 ?g L-1), Metsulfuron-metilico (0,150 ?g L-1), Penoxsulam (0,063 ?g L-1), referente a esta??o do outono, Atrazina (0,015 ?g L-1), Azoxistrobina (0,068 ?g L-1), Fipronil (0,085 ?g L-1), Imazepir (0,027 ?g L-1), Penoxsulam (0,063 ?g L-1) referente a esta??o do inverno, Azoxistrona (0,170 ?g L-1), Difenoconazol (0,029 ?g L-1), Fipronil (0,085 ?g L-1), Penoxsulam (1,231 ?g L-1). A avalia??o da contamina??o por agrot?xicos nos po?os de abastecimentos escolhidos ? um trabalho pioneiro, visto que n?o h? na regi?o dados de monitoramentos dispon?veis at? o presente momento. Embora presentes nenhum dos agrot?xicos apresentou concentra??o acima do limite m?ximo estabelecido na PRC N? 5/2017 do MS
