Concentración de metales pesados en suelos agrícolas bajo diferentes sistemas de labranza

Heavy metals are mineral elements whose accumulation in soils, water, and vegetal tissues constitutes a public health risk. High concentrations of these elements are associated with cancer and kidney and liver diseases. The accumulation of such metals is the consequence of industrial activities, but also agricultural production due to the excessive use of agrochemicals. Therefore, this study assessed the heavy metals contamination risk in Turen, in the northwest of Venezuela. Cd, Cu, Co, Zn, Fe, Mn, Ni, As, and Se were found in soils under two tillage systems (conventional and direct sowing) at two physiographic positions: high and low napa by X- ray fluorescence. The samples were taken at two depths, i.e., 0–10 and 10–20 cm, with nine samples per position in each tillage system. The results show that the content of Co, Cu, Ni, Cd, and Zn was higher in direct sowing due to the extended use of phosphate fertilizers. The greatest accumulation was observed at the low napa, which is associated with higher clay content and cation exchange capacity. The values of Co, Cu, and Cd were higher than the maximum allowable levels in most international environmental regulations. The accumulation of heavy metals in Turén soils, both in the conventional tillage system and in the direct sowing system, are the result of the continuous use of agrochemicals, in particular phosphate fertilization, so it is recommended to reduce the use of agrochemicals, in addition to carrying out bioremediation actions to eliminate them from the soil and avoid long-term contamination problems and health problems associated with their presence in soils and waters.Los metales pesados son elementos minerales cuya acumulación en el suelo, el agua y los tejidos vegetales constituyen un riesgo para la salud pública. Enfermedades cancerígenas, renales y hepáticas están asociadas a altas concentraciones de estos elementos. De igual forma, la acumulación de metales pesados está relacionada con actividades industriales, pero también a la producción agrícola, producto del uso excesivo de agroquímicos. Para evaluar los riesgos de contaminación por metales pesados en suelos agrícolas de la localidad de Turén al noroccidente de Venezuela, se midió el contenido de Cd, Cu, Co, Zn, Fe, Mn, Ni, Ar y Se en suelos bajo dos sistemas de labranza - convencional y siembra directa - en dos posiciones fisiográficas: napa alta y napa baja, mediante fluorescencia de rayos X. Las muestras fueron tomadas a dos profundidades: 0-10 y 10-20 cm, con 9 muestras por posición dentro de cada sistema de labranza. Los resultados mostraron que el contenido de Co, Cu, Ni, Cd y Zn fue mayor en el sistema de siembra directa debido al uso prolongado de abonos fosfatados Asimismo, la mayor acumulación se observó en la napa baja, lo cual estuvo relacionado a un mayor contenido de arcilla y a la capacidad de intercambio catiónico. Finalmente, se determinó que los valores de Co, Cu y Cd estuvieron por encima de los valores máximos permitidos por las normas ambientales internacionales La acumulación de metales pesados en suelos de Turén, tanto en el sistema de labranza convencional como en el de siembra directa, son producto del uso continuo de agroquímicos, en particular de la fertilización fosfatada, por lo que se recomienda reducir el uso de agroquímicos, además de llevar cabo acciones de biorremediación para su eliminación del suelo y evitar los problemas de contaminación que a largo plazo y problemas de salud asociada a la presencia de los mismos en suelos y aguas

Additional file 1: of Evidence of suppression of onchocerciasis transmission in the Venezuelan Amazonian focus

Detailed description of study area, criteria for elimination, calculation of infection indices and additional entomological data. Text S1. Geographical and environmental characteristics of the Venezuelan part of the Amazonian onchocerciasis focus. Text S2. Endemic communities, mapping and geographical information system. Text S3. World Health Organization (WHO) criteria for onchocerciasis elimination. Text S4. Calculation of parasitological indices. Text S5. Calculation of transmission indices. Table S1. Number of ivermectin rounds for twice yearly (6-monthly) and quarterly (3-monthly) treatments that reached a therapeutic coverage ≥85 %, by geographical sub-area in the Venezuelan part of the Amazonian focus. Figure S1. Monthly biting rates of Simulium guianense s.l. recorded in Orinoquito and Parima B during baseline (1982–2000) entomological evaluations. Figure S2. Infectivity rates and mean nos. of L3 larvae per fly for S. guianense s.l. in Orinoquito and Parima B during baseline (1982–2000) entomological evaluations. Figure S3. Monthly infective biting rates and monthly transmission potentials for S. guianense s.l. in Orinoquito and Parima B during baseline (1982–2000) entomological evaluations. Figure S4. Relationship between the proportion of infective flies and the mean number of infective larvae per fly in S. guianense s.l. at baseline. Table S2. Comparison of manual dissection and PCR (using PoolScreen™) for estimation of infectivity rates in S. guianense s.l., Koyowë, May 2000. (DOCX 129 kb