Valores de background geoquímico e suas implicações em estudos ambientais

Abstract

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.

Heavy metal distribution in recent sediments along the Tiet^|^ecirc; River basin (S^|^atilde;o Pauro, Brazil)

“…Use of regional or local background levels has been often discussed in literature involving heavy metal concentrations in soils, rocks and sediment profiles (Ferrand et al, 1999;Robaina et al, 2002;Marins et al, 2004;Rodrigues and Nalini, 2009). …”

Ecotoxicology of Pig Slaughterhouse Waste Using Lactuca sativa L., Raphanus sativus L., and Oryza sativa L.

“…This may result in the contamination of soil and water sources by heavy metals such as copper (Cu) and zinc (Zn), which are important components of feed dietary supplement and antibiotic formulations (Santos, 2010). Also, although some metals are necessary nutrients for plants and living organisms, they represent a risk if they exceed tolerable concentrations and may negatively impact the ecosystem and human health (Rodrigues et al, 2009). Moreover, slaughterhouse waste often contains pathogenic organisms, mainly coliform bacteria (total and fecal) and intestinal parasites (helminth eggs and larvae), which also make it impossible to use them directly for fertilization in food production areas (Pedrosa et al, 2013).…”

Distribuição dos metais pesados em sedimentos de fundo na bacia do alto Tietê: Fatores de enriquecimento e Classes de poluição

“…A poluição de metais também pode ser avaliada com o emprego do índice de geoacumulação (Müller, 1969), a partir da comparação das concentrações totais de metais pesados com o fundo geoquímico natural, dentro de classes de poluição. A importância da utilização de valores de referência regionais ou locais como fundo geoquímico natural tem sido bastante discutido na literatura envolvendo concentrações de metais pesados em solos e rochas da região de estudo e perfis de sedimentos, considerando as variabilidades das espécies químicas em questão numa determinada matriz, sendo ilusória a idéia de background geoquímico global (RODRIGUES & NALINI JUNIOR, 2009;ROBAINA et al, 2002;MARINS et al, 2004;MATSCHULLAT et al, 2000). De acordo com Mozeto et al (2001), os valores de referência regionais ou locais (background) podem ser obtidos por meio de testemunhos de sedimentos fluviais antigos, que antecedem o período industrial, ou ainda, concentrações obtidas para testemunhos coletados próximo às nascentes dos ambientes aquáticos em estudo, desde que não tenham sido atingidos pela ação antrópica.…”