MACNBR   00242
MUSEO ARGENTINO DE CIENCIAS NATURALES "BERNARDINO RIVADAVIA"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Study on Zn sorption in Pilcomayo River surface water (South America)
Autor/es:
RAFAEL S. SEOANE; MARÍA VICTORIA CASARES; LAURA DE CABO; OSCAR E. NATALE
Lugar:
Provincia de Buenos Aires
Reunión:
Simposio; The fifth International Symposium on Environmental Biotechnology and Engineering; 2016
Institución organizadora:
UNSAM
Resumen:
Contamination of aquatic sediments is a major concern worldwide. In reference to metals, aquatic organisms can take up metals through multiple pathways, with possible chronic and acute adverse effects.The Pilcomayo River (South America) is unique for its features. It presents a marked interseasonal variability in water discharge and is also one of the rivers with highest suspended solids transportation in the world. With its headwaters in the Bolivian Andes, Pilcomayo River tributaries have been historically impacted by wastewater discharges from the mining district in the Cerro Rico de Potosí. In the last 20 years some tailing dams have colapsed releasing thousands of kilograms of wastes. During the rainy season, these wastes reach the tributaries and ultimately Pilcomayo River, potentially threatening the lower basin floodplains and wetlands where solids are naturally deposited. To determine the environmental impact of these releases, it is important to predict the partitioning of metals to suspended particulate matter, speciation and its fate to establish potencial short and long-term hazards to aquatic life. Batch experiments were carried out to study the sorption kinetics of zinc (main metal extracted) onto natural suspended solids in Pilcomayo River surface water (collected in Misión La Paz, Salta). Zinc dissolved and total concentrations in Pilcomayo River surface water were 0.05±0.01 and 3.60±0.03 mg/L, respectively. Suspended solids concentration yielded 55.1±3.41 gr/L. Experimental containers with 250 ml of Pilcomayo River water were spicked to reach a 1 mg/L nominal zinc concentration, sealed and placed on a rotating rack that provided (800rpm) end-over-end mixing. Samples were taken at 5, 15, 30, 60, 360 (6 h) and 1440 (24 h) minutes from the control and treatment groups in triplicate and the dissolved and total concentrations of zinc were determined. Under constant ambient temperature and pH condictions, batch experiments results showed that 100 % of the added zinc was sorbed to suspended solids within the first 5 minutes. No significant modifications were observed in the dissolved and total zinc concentrations in subsequent time extractions. Grain size analysis of sediments showed 100 % silt and clay sizes. These results reflect the important role of the very high load of suspended solids in determining zinc partitioning in Pilcomayo River waters. However, further research is needed in order to determine metal speciation in the sediments and their possible mobility under dynamic redox conditions, since the floodplains are subjected to flood and drought during the summer and winter seasons, respectively.