Geochemical Markers of Metal and Organic Contamination in Brackish Sediments

The Holocene shallow sediments of brackish pond Lake Ganzirri, north-eastern Sicily (Italy) were examined to detect eventual exceedances of selected pollutants and their relationships with the textural, mineralogical/petrographic sediment features. The organic content of sediments, made up of humic and fluvic acid derivatives, was relatively low, with concentration increasing with depth and distance from the sea. The distribution of metals and organic matter allowed for relating some higher concentrations to critical issues near the surrounding urban fabric and influenced by the local water circulation. Different Metal Pollution Indices were used to evaluate the potential anthropogenic effects on the sediments, and by using a synthetic model for seawater, the distribution of some toxic metal cations was simulated in real conditions (i.e., pH, salinity and temperature). The multivariate analysis evidenced weak spatial trends, although statistically supported, in the metal contaminant distribution and relationship with the organic content, as a result of a complex interaction of natural and anthropogenic constraints. Lake Ganzirri, is thus proposed as an available case study of a brackish environment submitted to anthropogenic pressure.