Key issues on sediment quality assessment: A review of South American research with emphasis on Brazil

Abstract

Conventional approaches to pollution prevention in South American countries have traditionally relied on scientists identifying potentially harmful substances and practices, and advising regulators concerning exposures and effects. Since the 1990s scientific knowledge and skills have contributed to the creation of pollution control legislation. However the extent, to which the legislation is effectively applied, is determined by government policies. To be effective, strategies for environmental protection must be firmly supported by political commitment. Sediment is recognized worldwide as a major repository for persistent contaminants in aquatic ecosystems. Contaminant dynamics promote changes in the overlying water quality, as well as in porewater and can affect the biota even though the overlying water may meet water quality criteria. It is recognized that traditional water quality-based controls are not enough to protect the aquatic environments in which sediment quality assessment is also required. Although chemical analysis of sediment provides information, which may allow for the estimation of potential biological effects, contaminant concentrations are not accurate predictors of biological responses. Sediment Quality Values can only be derived from a database of biological effects verified for different organisms by a variety of methods that show the relationship between effects and contaminants. Given the difficulties in establishing this database, Brazil, like other countries in South America, still does not have Sediment Quality Criteria (SQC) despite the existence of quality criteria for water. Although effluents are often controlled according to normalized standards, high levels of contamination in reservoirs, rivers, estuaries and coastal areas have been found; consequently sediments are receiving greater attention in South America. The principles and techniques globally accepted for sediment toxicity assessment are already in use in many South American countries, in an attempt to solve localized problems of environmental contamination. Most of the countries have chosen local test-species according to required criteria, and have already standardized protocols to establish the relationship between contamination and toxicity. Several integrative approaches for sediment quality evaluation such as; Apparent Effects Threshold (AET), Equilibrium Partitioning (EqP) and Sediment Quality Triad (SQT) are also being applied to hotspots to promote political measures for conservation and remediation.