Abstract

Coastal ecosystems are subject to the discharge of contaminants via sewage, industrial effluents, storm water runoff, dredged material and accidental chemical spills. The majority of contaminants reaching the ocean tend to be adsorbed to particulate matter and eventually settle on the ocean floor, where they can deleteriously affect the sediment-associated community. The degree to which a receiving body is impacted is usually assessed by the analysis of the sediments from the area of concern. If chemical data generated by monitoring programs are available, they can be compared to Sediment Quality Guidelines to help identify a potential problem. A more cost-effective approach involves the use of a sensitive toxicity test to identify areas of concern, with comprehensive chemical analyses conducted at a later stage and focusing on the toxic sites identified in the initial screening survey. More complex studies involve the assessment of the benthic communities, in addition to toxicity tests and chemical analyses can be conducted. While methodologies for chemical and benthic community assessments are relatively well established, several approaches can be used to determine sediment toxicity, including acute or chronic tests, conducted in the laboratory or in situ, on the whole sediment or the liquid phase. Several factors should be considered when interpreting toxicity test results, such as the enhancement of toxicity by the photo-oxidation of organic chemicals by ultraviolet light (UV), and confounding factors such as salinity, ammonia, sulfides, particle size distribution, organic matter content, and acid volatile sulfides (AVS). Once an impact has been identified, toxicity identification evaluation (TIE) procedures can be applied to help establish the chemical or classes of chemicals responsible for the observed adverse effects. The international and Brazilian scientific literatures are reviewed to illustrate these approaches.

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