RESUMEN
The dairy basin of the Mantaro River located in the centre of Peru faces serious anthropogenic disturbances as it receives emissions and discharges from the metallurgical mining activity located in the headwaters of the basin and milk contaminated with lead (Pb) and cadmium (Cd) endangers the environmental and human health, especially children. To measure the concentrations of Pb and Cd in milk and the dangers of their consumption in the Peruvian population, 40 milk samples were collected and quantified by atomic absorption spectrometry. The mean concentration of Pb in milk was 15 ± 2.6 µg/kg, which represented 75% of the Maximum Limit (ML), and that of Cd was 505 ± 123 µg/kg, which exceeded the ML by more than 194 times. The estimated weekly intake of Pb for people aged 2−85 years was below the Provisional Tolerable Weekly Intake (PTWI) references, determining risk coefficients (CRD) < 1. Weekly Cd intake was much higher than the PTWIs and CRDs were between 14 and 34, indicating that consumers would experience carcinogenic health effects, with children being at higher risk than adults, therefore, milk from the area is not safe for consumption. Cd would be transferred mainly through the soil (water)-grass-milk pathway, due to its presence in irrigation water and in fertilizers that contain Cd. The main pathway for Pb entry would be air-soil (water)-milk grass, from the fine particles emitted into the air by the mining-metallurgical activity, developed approximately 90 km from the study area.
RESUMEN
Se determinó el efecto de la fertilización orgánica sobre las poblaciones bacterianas del suelo en cultivos de papa y maíz durante la campaña agrícola 2008-2009 en terrenos de cuatro localidades del Valle del Mantaro: INIA Santa Ana (Huancayo), en la EEA El Mantaro (Jauja), Vista Alegre y Huayao (ambos en Chupaca). En estos lugares se instalaron parcelas experimentales de papa (Solanum tuberosum L. Var. Canchan) y maíz (Zea maíz L. Var. Cusco mejorado) bajo abonamiento orgánico (vacuno, ovino, cuy), fertilización química y sin fertilización alguna (testigo). Para dicho efecto se empleó las técnicas de la Electroforesis en Gel de Gradiente Desnaturalizante (DGGE) con amplificación de la región 968 1401 del rDNA 16S. Los resultados obtenidos muestran que la variabilidad de las poblaciones bacterianas en los suelos está afectado directamente por el tipo de cultivo mas no por el tipo de fertilización ya que el efecto de este último resulta variable para cada zona experimental y cultivo encontrándose solo en la zona experimental de Chupaca - Maíz una segregación de los tratamientos con fertilización orgánica de los tratamientos químicos. También se ha encontrado que la variación de las comunidades microbianas no sufre variaciones significativas en los suelos con cultivos de maíz obteniéndose coeficientes de similaridad para todos los tratamientos por encima del 80% mientras que para los tratamientos en los cultivos de papa dicho coeficiente fue de tan solo del 60%.
The effect of organic fertilization on soil bacterial populations in potato and corn crops during the crop season 2008-2009 at four sites in the Mantaro Valley locations: INIA Santa Ana (Huancayo), the EEA El Mantaro (Jauja), Vista Alegre and Huayao (both in Chupaca). In these places were set up experimental plots of potato (Solanum tuberosum L. var. Canchan) and corn (Zea maize L. Var. Cusco enhanced) under organic manure (cattle, sheep, guinea pig), chemical fertilizer and no fertilizer at all (control) . To do this we used the techniques of electrophoresis Denaturing Gradient Gel (DGGE) with amplification of the region from 968 to 1401 of 16S rDNA. The results show that the variability of bacterial populations in soil is directly affected by crop type but not by the type of fertilization and the effect of the latter is variable for each experimental area and culture found only in the experimental area of Chupaca - Corn segregation of treatments with organic fertilization of chemical treatments. We have also found that the variation of the microbial communities did not suffer significant variations in soils with maize similarity coefficients obtained for all treatments above 80% while for the treatments in potato crops that rate was only 60%.