Spatial distribution characteristics of granulometric, morphoscopic and compositional sediments of the beaches of Aracaju, Sergipe

Abstract

The aim of this study is to analyze spatially the granulometric, morphoscopic and compositional characteristics of sediments present along Aracaju beaches in the northeastern Brazilian state of Sergipe. The methodology included analysis of 24 samples of superficial sediments from the intermediate beach face, collected each 1 km along the shoreline. The collection points were georeferenced with GPS Garmin Colorado 400t. In the laboratory, sediment particle size analysis was made by the dry sieving method. The data were entered in the "Sistemas de Análises Granulométricas" (SYSGRAN), which provided the grain size, sorting, skewness and kurtosis. About 300 grains of coarsest fractions were separated for morphoscopic and compositional analysis under a binocular loupe. Subsequently, the data were spatialized in the ArcGis 9.3.1. The beach sediments of the study area are predominantly very fine sand, moderately to very well sorted, with symmetric, negative skewness and platykurtic distribution curves. The grains are sub-rounded, with high sphericity and composed essentially of quartz. However, near the Sergipe river mouth, sediments exhibit mixed characteristics of fluvial and beach environments, indicating the importance of this river as a source of sediment to these beaches. The characterization of sediments aid in beach recovery programs and in determining the environmental sensitivity to oil spill, among other applications. Therefore, it is of great importance to environmental planning.