Determinación de elementos mayores en sedimentos provenientes de zonas afectadas por actividades petroleras en Ecuador

Abstract

* g −1 . Mientras que las concentraciones en el bulk de los sedimentos fueron , Na: 3-24 y Mn: 0.43-1.28 mg g −1 . En las muestras analizadas, el 43 % del Na, el 93 % del Fe, el 70 % de Mg, el 62 % de Mn y el 94 % de K están asociados con la fracción fina de los sedimentos. Las concentraciones de Mg, Na y Mn están influenciadas por las actividades petroleras mientras que el contenido de Fe, K y Al está relacionado con el origen natural de los sedimentos. Sin embargo, aguas abajo, hasta la frontera con Perú, no se observa un incremento significativo en las concentraciones de elementos mayores en relación a los puntos de control, aguas arriba de la ZIL, Zona de Influencia Local de las actividades petroleras. Palabras Analisis of major cations in bottom sediments from oil impacted Rivers, in the Ecuadorian Amazon AbstractHeavy metal pollution is one of the biggest problems of great concern at the global, regional and local levels due to mining and oil activities, because those elements constitute a threat to aquatic biota and human health. The major elements and heavy metals tend to accumulate in sediments, which act as secondary sources of contamination, and this process is closely related to the redox conditions, the particle size distribution of the sediments and the amount of sedimentary organic matter. Therefore, the aim of this work conducted in the frame of the MONOIL Research Program between France and Ecuador, is to determine the concentration of major elements (K, Mg, Na, Fe, Mn and Al) in the fine fraction of sediments, particles <4 µm, collected in the basins of the Aguarico, Napo and Esmeraldas Rivers, which are areas affected by the oil industry in Ecuador. Concentrations of major elements in the fine fraction are then compared to concentrations in the bulk, which was determined in the same sampling points in a previous work. Environmental parameters in surface waters such as temperature, dissolved oxygen (DO), pH, conductivity and oxide reduction potential (ORP) were determined in situ in each sampling point. The isolation of the fine fraction was carried out based on Stokes' law after a homogenization, quartering and dissolution of the sediment in distilled water. Mineralization in sediments was performed by a triacid attack with HCl, HNO3 and HF. The major elements were determined by atomic absorption spectrophotometry (AAS). The ranges of major elements in the fine fraction of sediments were: Fe: 18-49, Al: 26-59, K: 3-15, Mg: 3-13, Na: 1-11 and Mn: 0.38-0.89 mg g −1 ; while concentrations in the bulk sediment concentrations were: Fe: 25-49, Al: 45-82, K: 5-20, Mg: 4-16, Na: 3-24 and Mn: 0.43-1.28 mg g −1 . In the sediment samples of the Northern Ecuadorian Amazon rivers, 43 % Na, 93 % Fe, 70 % Mg, 62 % Mn and 94 % K are associated with the fine fraction. The concentrations of Mg, Na and Mn in bottom sediments are influenced by oil activities, while Fe, K and Al concentrations depend on the natural origin of sediments. However, downstream up to the border with Peru, no significant increase in the...

Determination of the Microbial and Chemical Loads in Rivers from the Quito Capital Province of Ecuador (Pichincha)—A Preliminary Analysis of Microbial and Chemical Quality of the Main Rivers

“…Conductivity values ranged from 19.87 μS/cm in the Caoní River to 616.00 μS/cm in the Monjas River. According to the US Environment Protection Agency (EPA), the suggested range of conductivity for surface waters is 150–500 μS/cm, meaning that the obtained values in this study are lower and higher than the suggested ones [ 19 ]. Half of the analyzed rivers evidenced conductivity values lower than the minimum value (150 μS/cm), more exactly, the Caoní, Mashpi, Pachijal, Chiche, Blanco, Alambi, Pilatón, Mindo and Guachalá Rivers.…”

“…Although the contamination of Pichincha’s rivers is visible nowadays, few studies have been published regarding their microbial and chemical quality [ 19 , 20 , 21 ]. The last study conducted by the municipal water service of Quito (EPMAPS) revealed that most of the rivers in the south part of the capital exceeded the authorized microbial limits of potable water by 3000% [ 22 ].…”

“…[ 25 , 26 , 27 , 28 ]. Water quality can also be evaluated in terms of physico-chemical properties and parameters [ 19 , 29 ], such as metals, which can reach the hydrosystem through natural or anthropogenic sources. The natural causes for the presence of metals in rivers can be attributed to rock erosion or soil weathering, while the ones for anthropogenic sources include industrial, mining, and agricultural discharges or untreated sewage [ 5 , 19 , 29 ].…”

Determining the microbial and chemical contamination in Ecuador’s main rivers

“…High values of conductivity were found in Guayas (4137.33 µS cm −1 ), Esmeraldas (938.53 μS cm −1 ), and Machángara (501.10 µS cm −1 ) Rivers. The Environmental Protection Agency (EPA) suggests a range of conductivity between 150 and 500 μS cm −1 , and therefore the conductivity values found in the river basins are higher than the recommended values 18 . In addition, the ORP values found in this study were between 62.44 and 412.77 mV, in which Coca River showed the highest value of ORP.…”

“…These contaminants cause variations of the physicochemical properties of water resources, which directly influence microbial proliferation, and therefore physicochemical analysis is also an indispensable feature for the water quality assessment. Finally, high levels of heavy metals (such as Pb, Cr, Cu, and Zn) represent a serious public health risk because they are not biodegradable 18 .…”