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Os protocolos de avaliação rápida de rios, no âmbito da conservação e preservação dos recursos hídricos, podem ser utilizados como instrumentos complementares nos programas de monitoramento da qualidade dos ecossistemas fluviais e, portanto, como ferramenta útil para os órgãos gestores e controladores dos recursos naturais. Este trabalho traz ao leitor uma visão panorâmica do monitoramento da qualidade da água no Brasil, uma visão holística sobre os ecossistemas fluviais e, além disso, apresenta os protocolos existentes e aponta algumas razões pelas quais esses protocolos podem ser utilizados como instrumentos complementares no monitoramento dos recursos hídricos.

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The establishment of background geochemical values as a relative measure to distinguish anthropogenic input from natural (geogenic and/or biogenic) concentrations of elements in different environmental samples, is one of the most important subjects in recent environmental sciences. The relationship between natural and anthropogenically altered concentrations of chemical species is a question that involves many implications in the geological, toxicological, biological and other areas of knowledge. This is especially important when geochemical interpretations of toxic elements are required. Thus, the principal objective of this article is to present and discuss the reasons for which the establishment of background geochemical values has implications in environmental studies. Throughout this article some concepts of the geochemical background used by various authors is presented and the main methods used for assessing background concentration of elements (direct and indirect methods). In addition, some examples of studies developed in Brazil are presented. Studies involving the establishment of background geochemical values are important because they allow the evaluation of potential contamination risks and the identification of natural trace-element concentrations in a determined area.