Avaliação espacial de metais pseudo-totais e disponíveis em sedimento de fundo do Rio Alegria – PR

Abstract

Sediments are fundamental components in the water course. In addition to serving as a source of nutrients for various aquatic organisms, they are also present as reservoirs of environmental contaminants, such as metals. The present work evaluated spatially the concentration of pseudo-total and environmentally available metals in the bottom sediment of the Alegria River, which is located in the municipality of Medianeira, Paraná. Two sampling campaigns were carried out at four different points along the river, during the winter and spring periods corresponding to the year 2017. A Petersen dredger was used to collect sediment from the river bottom and was characterized by physico- (Al), chromium (Cr), copper (Cu), zinc (Zn) and potassium (K) were determined by the following parameters: pH, total organic carbon, organic matter, total phosphorus and aluminum in the available and pseudo-total plots, using the technique called Atomic Absorption Spectroscopy (FAAS). Subsequently, the contents of the metals were determined and the results obtained in the analyzes were compared with the guiding values stipulated in the US National Oceanic and Atmospheric Administration (NOAA) Sediment Quality Guide (SQG), as well as the concentrations limits established by CONAMA Resolution No. 454 of 2012, a standard based on the Canadian Sediment Quality Guide. As for the characterization of the collection points, point 1 was located in a rural area, near the source of the sanga Magnolia (affluent of the Alegria river), with agricultural and agricultural activities. Point 2 was located downstream of point 1, at the water catchment dam for public water supply in the municipality. Point 3 was located in the region where the Alegria river leaves the urban area, passing through precarious houses where several point sources of pollution have been identified. Point 4 was delimited near the mouth of the river Alegria near the Ocoí River, in the São Bernardo community in the rural area, predominantly agricultural area. From the results, it was found that Al was the metal found in the highest proportions in the pseudo-total plot in the bottom sediment of the Alegria river, due to the fact that this element is one of the main metals found in rocky material and consequently, in soils and sediments, due to erosion caused by abiotic factors such as wind and precipitation. All concentrations related to the pseudo-total plot of Al were above the highest limit, which is found in the ARCS guide. The metals Al and Cr, in their available plots, did not exceed their respective minimum background values of NOAA. As for Zn, only in P3, during the spring, a value above which no toxic effect was known was known (Level 1/TEL). Cu was the only metal in which the available portion resulted in thresholds that overlapped Level 1/TEL. Correlating only the organic matter, the total organic carbon and the pH values of this study, it can be inferred that the points P2 and P3 contain conditions more favorable to the retention of the metals and other contaminants in the background sediment phase, causing such components do not harm aquatic biota or even water quality and do not endanger human health.