SEDIMENTOLOGICAL EVALUATION OF BENCHES IN FLUVIAL REACH WITH DICHARGE OF DOMESTIC EFFLUENT: MANDACARU STREAM, PR

Abstract

The discharge of domestic effluent may deteriorate the water quality of rivers and potentially affect the fluvial landscape. In this study, we evaluated the sedimentological characteristics of benches and potential alterations resulting from the discharge of domestic effluent. The benches are located at the upstream and downstream of the effluent discharge and composed the final reach of the Mandacaru Stream, Southern Region of Brazil. Sedimentological samplings to  grain size and organic matter were performed at 10 cm depth from the surface of the benches. The average mud (silt and clay) content was approximately 47%. The average organic matter content was approximately 2.7%. Statistical analyzes showed that there is no significant variation in the content of mud and organic matter in the surface layer of the levels between the upstream and downstream samplings of the effluent discharge. The results also indicated that there is a strong correlation between the concentration of mud and organic matter. The application of a statistical test with the residues of this correlation also evidences that, even without the influence of the mud concentration, there is no significant difference in organic matter between the upstream and downstream of the effluent discharge. The benches, in the evaluated geomorphological context, do not store organic matter. This characteristic can be explained by the occurrence of high magnitude flows from urbanization in the watershed.

Keywords: Grain Size. Organic Carbon. Mandacaru Stream.