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A forensic approach was used to evaluate sediments from Portão Stream, including analysis of metals, carbon (C) and nitrogen (N) stable isotopes, and C:N ratios. Samples collected at various points located along the stream were tested in order to investigate a possible illegal leachate input. The studied stream is heavily impacted by sewage and industrial discharges from two cities along its course. Among the metals analyzed, chromium (Cr) was noticeably the main pollutant, showing the highest levels, above regulatory limits, downstream from some potential sources of effluents enriched with this metal. Isotope analyses revealed a general trend of depletion in the heavier isotope along the stream for C and N. The exception was one point near a hazardous waste landfill, where relatively more enriched δ13C and δ15N values were found. The isotope and metal analysis results indicated that this site was affected by a particular source, demonstrating the combination of these parameters could be used for the discrimination of sources in a heavily polluted stream. Nevertheless, further investigations are necessary to provide a comprehensive evaluation of the biogeochemical processes involved in the incorporation of leachate in sediments to use this analysis as evidence for the illegal leachate discharge. [ABSTRACT FROM PUBLISHER]

In order to identify the ontogenetic changes in the food items assimilated by the larvae of Plagioscion squamosissimus and Hypophthalmus edentatus, we analyzed the stomach content and the nitrogen isotopic value (δ15N) from the larvae. Samplings were performed monthly, from October 2002 to March 2003, and October 2003 to March 2004 in the subbasin of the Ivinheima River (Upper Paraná River floodplain), Mato Grosso do Sul State, Brazil. The food items assimilated by the larvae of P. squamosissimus changed with respect to the developmental stages. In the preflexion stage, we found a large contribution of phytoplankton, followed by zooplankton. During the flexion and post-flexion stages, we recorded a decrease in phytoplankton contribution, an increase in zooplankton contribution, and the presence of zoobenthos. In H. edentatus, phytoplankton made the greatest contribution, followed by zooplankton. Ontogenetic changes in δ15N for this species were not detected. For both species, the food item predominantly ingested was not the assimilated one, except for the last two developmental stages of P. squamosissimus. [ABSTRACT FROM AUTHOR]