ABSTRACT The Morroa aquifer, which is an essential source of water supply in Sucre, Colombia, with more than 500,000 users, may be at risk because of pesticide contamination that comes from different agricultural activities. The aim of this research was to evaluate the relationship between the presence of pesticides and the physicochemical properties of soils in the most vulnerable areas of the Morroa aquifer. Therefore, farmers were surveyed about pesticide usage and soil samples which were taken for analysis of pesticide and physicochemical properties. The results demonstrated that soils in these areas were relatively homogeneous in terms of texture, pH, cation exchange capacity and organic matter content. Pesticides detected in these soils were malathion, β-BCH, p-p’DDE, m-p’DDD, p-p’DDT, endosulfan, endrincetone, chlorpyrifos, dieldrin, endosulfan-sulfate, heptachlor-epoxide, and parathion. Physicochemical properties such as pH and texture of soils and intrinsic characteristics of the pesticide were found as the most influential variables according to statistical results. This study also presents a map of the spatial distribution of pesticide concentration according to the concentration of pesticides, which constitutes an important tool for the planning of agricultural activities that supports decision-making and the implementation of measures to mitigate potential impacts caused by pesticide pollution.

RESUMO O aquífero de Morroa é uma fonte essencial para o abastecimento de água em Sucre, Colômbia, com mais de 500.000 usuários que podem estar em risco devido à contaminação por pesticidas que provêm de diferentes atividades agrícolas. O objetivo desta pesquisa foi avaliar a relação entre a presença de pesticidas e as propriedades físico-químicas dos solos nas áreas mais vulneráveis do Aquífero Morroa. Para isso foi aplicado um inquérito sobre a utilização de pesticidas aos agricultores e foram coletadas amostras de solo para análise de pesticidas e propriedades físico-químicas. Os resultados mostraram que os solos nestas áreas são relativamente homogéneos em termos de textura, pH, Capacidade de Troca Catiônica e Matéria Orgânica. Os pesticidas detectados nestes solos foram Malathion, β-BCH, p-p’DDE, m-p’DDD, p-p’DDT, Endosulfan, Endrincetone, Chlorpyrifos, Dieldrin, Endosulfan-Sulfate, Heptachlor-epóxido e Parathion. O pH, a textura do solo e as características intrínsecas do pesticida são as variáveis mais influentes de acordo com os resultados estatísticos. Este estudo também mostra a distribuição espacial da concentração de pesticidas em toda a área do aquífero. O mapa elaborado constitui uma ferramenta para o planeamento de atividades agrícolas que subsidia a tomada de decisões e a implementação de medidas para mitigar os potenciais impactos causados pela poluição causada pelos pesticidas.

Objective Determining the magnitude of mercury exposure in the population living in the municipality of San Marcos due to eating contaminate drice (Oryza sativa). Methods Twenty people (representative of the population) were selected, as were food (raw rice) and hair samples for determining total mercury and methyl mercury by cold vapour atomic absorption spectrophotometry. Student's t-test was used for comparing different samples (p<0.05 significance level) and correlation was analysed for determining the relationship between consumption habits and mercury concentration in humans. Results Rice sold loose (i.e. unpackaged San Marcos white rice) was the only sample having 0.021 mg/g minimum total mercury concentration, whilst rice sold in packaged form yielded no measurable value. Only 5% of the population sample exceeded the US Environmental Protection Agency's (EPA) 0.1 mg/kg bw/day reference dose (RfD) for Me Hg ingestion (RfD). Conclusions The HgT exposure of people living in and around San Marcos concerning rice consumption was low and did not involve great risks to their health. However, frequent consumption of other types of contaminated food could pose a potential threat to the consumers' health, meaning that ongoing environmental monitoring is necessary.

Objetivo Determinar la magnitud de la exposición a mercurio en los habitantes del municipio de San Marcos debida a la ingesta de arroz (Oryza sativa) contaminado. Métodos Se seleccionaron 20 personas representativas de la población y se tomaron muestras del alimento (arroz crudo) y muestras de cabello para determinar mercurio total y metilmercurio mediante la técnica de espectrofotometría de absorción atómica por vapor frio. Para realizar comparaciones entre las distintas muestras se realizaron t-test, tomando un grado de significancia P<0.05 y para determinar la relación entre los hábitos de consumo y la concentración de mercurio en humanos se realizó un análisis de correlación. Resultados El arroz comercializado de forma suelta (arroz blanco de San Marcos) fue el único que mostró una mínima concentración de mercurio total de 0,021 μg/g, mientras que los que se comercializan de forma empacada no arrojaron un valor cuantificable. Solo el 5 % de la muestra poblacional excedió la dosis de referencia de Ingestión de MeHg (RfD) establecida por la EPA,de 0,1 μg/Kg de peso corporal/día. Conclusiones La exposición a HgT de los habitantes del municipio de San Marcos por consumo de arroz es baja y no implica grandes riesgos para su salud. No obstante, el consumo frecuente de otros alimentos contaminados podría representar una amenaza potencial para la salud de los consumidores, lo cual hace necesario su permanente monitoreo ambiental.

Objetivo Determinar la magnitud de la exposición a mercurio en los habitantes del municipio de San Marcos debida a la ingesta de arroz (Oryza sativa) contaminado. Métodos Se seleccionaron 20 personas representativas de la población y se tomaron muestras del alimento (arroz crudo) y muestras de cabello para determinar mercurio total y metilmercurio mediante la técnica de espectrofotometría de absorción atómica por vapor frio. Para realizar comparaciones entre las distintas muestras se realizaron t-test, tomando un grado de significancia P<0.05 y para determinar la relación entre los hábitos de consumo y la concentración de mercurio en humanos se realizó un análisis de correlación. Resultados El arroz comercializado de forma suelta (arroz blanco de San Marcos) fue el único que mostró una mínima concentración de mercurio total de 0,021 μg/g, mientras que los que se comercializan de forma empacada no arrojaron un valor cuantificable. Solo el 5 % de la muestra poblacional excedió la dosis de referencia de Ingestión de MeHg (RfD) establecida por la EPA,de 0,1 μg/Kg de peso corporal/día. Conclusiones La exposición a HgT de los habitantes del municipio de San Marcos por consumo de arroz es baja y no implica grandes riesgos para su salud. No obstante, el consumo frecuente de otros alimentos contaminados podría representar una amenaza potencial para la salud de los consumidores, lo cual hace necesario su permanente monitoreo ambiental.

Objective Determining the magnitude of mercury exposure in the population living in the municipality of San Marcos due to eating contaminate drice (Oryza sativa). Methods Twenty people (representative of the population) were selected, as were food (raw rice) and hair samples for determining total mercury and methyl mercury by cold vapour atomic absorption spectrophotometry. Student's t-test was used for comparing different samples (p<0.05 significance level) and correlation was analysed for determining the relationship between consumption habits and mercury concentration in humans. Results Rice sold loose (i.e. unpackaged San Marcos white rice) was the only sample having 0.021 mg/g minimum total mercury concentration, whilst rice sold in packaged form yielded no measurable value. Only 5% of the population sample exceeded the US Environmental Protection Agency's (EPA) 0.1 mg/kg bw/day reference dose (RfD) for Me Hg ingestion (RfD). Conclusions The HgT exposure of people living in and around San Marcos concerning rice consumption was low and did not involve great risks to their health. However, frequent consumption of other types of contaminated food could pose a potential threat to the consumers' health, meaning that ongoing environmental monitoring is necessary.