Antonio Trinidad Santos

Heavy metals contamination in soils around tailing heaps with various degrees of weathering in Zimapán, Mexico

Dispersion of mine tailings is the main cause of heavy metal (HM) contamination in soils in Zimapán, Mexico; however, the extent of this problem has not been assessed. Therefore, the aims of this study were to determine the degree of contamination and to assess the influence of mine tailings with different degrees of weathering on the spatial distribution of HM in soils. Soil and mine tailing sampling was carried out. The HM concentration was determined by atomic absorption spectrophotometry; spatial analysis and the size of the contaminated areas were calculated using GIS software; the mine tailings were characterized physically, chemically and mineralogically. The results suggest that all the tailing heaps have contributed to the HM dispersion. High HM concentrations were founded in soils around mine tailings (9402 mg kg−1 Pb and 52 mg kg−1 Cd). Surface area contaminated with Pb and Cd was estimated at 6.2 and 2.7 km2, in urban soils, respectively.

CARACTERIZACIÓN Y SELECCIÓN DE RIZOBACTERIAS PROMOTORAS DE CRECIMIENTO EN PLÁNTULAS DE CHILE POBLANO (Capsicum annuum L.)

En el cultivo de chile se usan altas dosis de fertilizantes que al no ser aprovechadas totalmente por las plantas ejercen efectos negativos en el ambiente. El uso de microorganismos beneficos puede ser una alternativa para disminuir las dosis de fertilizantes. En el presente trabajo se aislaron cepas de rizobacterias de la region de la Sierra Nevada, Puebla, Mexico, con el objetivo de evaluar su potencial para promover el crecimiento de plantulas en chile poblano. Las cepas se caracterizaron por su capacidad de solubilizar fosfatos, fijar nitrogeno y producir auxinas. Las diez mejores cepas se evaluaron por su capacidad de promover el crecimiento en plantulas de chile poblano y finalmente estas se identificaron a nivel molecular. Se aislaron un total de 215 cepas, de las cuales 74 fueron solubilizadoras de fosfatos que liberaron entre 10 y 881 μg/mL de fosfato soluble, 70 cepas tuvieron habilidad de crecer en medio libre de nitrogeno y 71 cepas produjeron entre 20 y 27 μg/mL de indoles. Las cepas inoculadas causaron efecto significativo en el crecimiento (Tukey, p < 0.05), siendo las mejores Serratia plymuthica CPPC55 y Rhizobium nepotum CPAC35, que incrementaron el peso de la parte aerea en mas de 20 %. Ambas cepas pueden ser usadas para aumentar la calidad de plantulas de chile poblano, lo cual podria garantizar un mejor establecimiento y sanidad de estas en campo. Las areas cultivadas de chile poblano son una fuente de microorganismos que pueden ser utilizados como promotores del crecimiento en especies de importancia agricola.

Generación de un inoculante acelerador del compostaje

Composting was performed using a mixture of ovine manure and straw. Inoculum was extracted at five different phases of the composting process (18, 23, 28, 33 and 38 days after the start of the composting process) and its effect on reducing biotransformation time was evaluated in the composted ovine manure. The samples were preserved in a deep freezer, then lyophilized to obtain the inoculum, 50g of which was added to each treatment in the second experimental phase. Six treatments were established; C=straw (P)+ovine manure (E), T1=P+ E+inoculum 18 days after the start of the composting process (I18), T2=P+E+I23, T3=P+E+I28, T4=P+E+I33, T5=P+E+I38, with three replications. Treatments were placed in a controlled-environment chamber at 45% relative humidity and 30°C along with flasks containing 50g of material to measure daily production, CO2 accumulation, temperature, pH, electric conductivity (dS/m), organic matter (%), total nitrogen (%), total carbon (%), C: N ratio, particle size (Tp) and bulk density (g/l). CO2 production (mg) showed a significant difference (p ≤.05) of treatments T2 and T5 with respect to the others, which demonstrated that the inoculum of these treatments accelerated the dynamics of microorganisms and the composting process. The quality and maturity of the compost are guaranteed as the amount of CO2 decreases.