Metales pesados en sedimentos riverinos de cuencas hidrográficas impactadas por minería en la región sur del Ecuador

The Southern Region of Ecuador is nationally known for mining, specifically the one held in the basins of Puyango and Zamora rivers. The Puyango River basin has been impacted by mining activities since pre-colonial times mainly by the Portovelo-Zaruma mining district. Currently, in the upper Puyango basin are more than 110 processing plants, which drain their heavy metal rich effluents to the Calera and Yellow rivers, which are the major tributaries of the Puyango River. Similarly, in the Zamora River basin the small - scale gold mining activities are carried out in the mining area of Chinapintza - La Herradura. The more impacted water channels in this basin are La Herradura stream and the Conguime River. Thus this research is aimed at identifying and quantifying the effects of gold mining in the chemical composition of river bottom sediments adjacent to mining areas in the Southern Region of Ecuador. The element determinations were carried out by atomic absorption spectroscopy in order to know the normalized enrichment factors of the measured elements in the riverine sediments. Sediment samples for the determination of Al, Fe, Mn, Zn, Cr, Pb, Cr, Co and Ni were subjected to acid digestion using the EPA 3050B method. Then, the extracts of sediments were analyzed by atomic absorption spectrophotometry. However, in the case of Hg analysis, the sediment samples were digested with a mixture of nitric acid, hydrochloric acid and potassium permanganate, and then analyzed using the cold vapor technique. According to the results, the highest heavy metals concentrations in the Puyango basin were observed in the sediments collected after the confluence between the Calera and Amarillo rivers. The high concentrations of heavy metals and the low levels of Al found in the sediments of this sector indicate that these sediments are composed mainly of polymetallic mineral, which has been discharged by the mineral processing plants after the gold extraction process. The sediments of the middle and lower sections of the Puyango River showed a high enrichment factors for the elements Hg, Cu, Pb and Zn, whereas the elements Co, Fe and Mn were found to be slightly enriched. In the case of the Zamora River basin, the highest concentrations of Mn, Zn, Pb and Cu were found in the suspended matter of the La Herradura mining effluent and in the bottom sediments of the Conguime River. By contrast, the Nanagaritza river had low levels of heavy metals in sediments. However, after the confluence with the Conguime River, the concentrations of Mn, Cu, Pb, Cr and Co in sediments of the Nangaritza River were increased considerably. The suspended sediments of the Chinapintza mining effluent (CHI) showed high levels of Mn, Zn, Pb, Ni, Cr, Co and Cu in comparison with the suspended sediments of the Nambija mining effluent (NAM 1). This fact was probably due to the geology of the area and the form of extraction and processing of the mineral. The Conguime and Nambija rivers had the highest enrichment factors of elements of the Zamora basin, mainly due to the impact caused by the mining effluent coming from the Chinapintza - La Herradura and Nambija sectors, locations where artisanal mining and small-scale gold mining activities are performed. The high concentrations of Hg, Cu, Pb, Zn, Mn and Fe in river sediments of both basins may have adverse effects on aquatic biota, according to the criteria established by national and international guidelines. Similarly, the high content of heavy metals in sediments of these river systems may cause severe damage to the health of people who use these river waters for human consumption.

• Autore principale: Jumbo Flores, Diana Carolina (author)
• Natura: bachelorThesis
• Lingua: spa
• Pubblicazione: 2015
• Soggetti: METALES PESADOS; CUENCAS HIDROGRÁFICAS; MINERÍA; SEDIMENTOS RIVERINOS
• Accesso online: http://dspace.unl.edu.ec/jspui/handle/123456789/11022