Effect of pollution on the physicochemical, structural and surface characteristics of the sediments of the Reconquista River, Argentina

ANA TUFO; NATALIA PORZIONATO; AGUSTINA ZILIANI; CELESTE GRIMOLIZZI; CURUTCHET GUSTAVO

Simposio; The Sixth International Symposium on Environmental Biotechnology and Engineering; 2018

The Reconquista river basin (located in the province of Buenos Aires) represents one of the most polluted areas of Argentina. In previous ISEBE conferences, we presented a bioremediation technique for the treatment of sediments with high contents of heavy metals1 and the study of how the physicochemical and structural parameters of the treated sediments were modified during the process 2. In line with these investigations, in this work we have analyze the influence of the contamination on some physicochemical, structural and superficial characteristics of the sediments. To fulfill this aim, two sites from the river basin were sampled: Km 2 of Autopista Camino del Buen Ayre (CBA) (a highly contaminated site) and Dique Ing. Roggero (DR) (a non-contaminated location). The dissolved oxygen (DO), the oxidation reduction potential (ORP), the pH and other parameters of the water were determined in situ. Cores of 30 cm deep of sediment were extracted with a specially designed device. The pH, ORP, organic matter (MO) and volatile acid sulfides (AVS) were determined every 5 cm depth at the extracted cores. A sequential extraction of metals was carried out at samples and implemented the BCR method. The sediments were characterized by means of XRD, BET, porosity and particle size techniques. We found that the pH is slightly more alkaline for the contaminated site and remains constant along the depth at both sites (9.5-9 for CBA and 8-8.5 for DR). The CBA samples shown typical parameters of strong contamination and pollutants accumulation: ORP values of approximately -300 mV, OM values from 13 to 6 % with respect to the depth, and concentration of AVS from 3500 to 2500 mg/kg. On the contrary, the sediments of the DR shown values around +200 mV, the OM was less than 5% and AVS concentration was negligible. Regarding the accumulation of metals in the sediments, it should be remarked that in contaminated places the metal concentration at surface is generally higher than at 30 cm depth, suggesting continuous input from water column. For example, for Zn , we found at CBA 280 mg/kg surfce, decreasing to ~150 mg/kg at 30 cm depth. DR shown superficial concentration of 7 mg/Kg. The increase of Zn concentration en CBA site due to contamination is dramatic. XRD and surface area analysis shown changes in the whole sediment and in it´s clay fraction that could have strong influence on the fate of pollutants in the sediments. The whole set of results will allow us to understand how the degree of contamination, the accumulation of metals and the rest of examined parameters affect the intrinsic characteristics of the sediments and it´s role in regulating pollutants processes.