Use of a chemometric tool to establish the regional background and assess trace metal enrichment at Baixada Santista - southeastern Brazil.

The trace metals in sediments consist of two components, anthropogenic and lithogenic or natural, which can cause misinterpretations for what actually exists in sediments. Normally, to investigate trace metal background levels, indices are applied in order to normalize the values and reduce natural variability, but it is well known that using the average shale or crust content is not the best choice and vertical sediment profiles are not always available. The purpose of this study is to use a prediction interval to assess metal enrichment without a reference level and to assess a regional background level using the same tool. The levels of eight elements were submitted to a partial digestion technique and analyzed by ICP-OES. The enrichment factor results suggested that using background values from the prediction interval and using values from vertical sediment profiles yield statistically similar results. Furthermore, the background equations present more realistic data than other methods because they consider the mud content of the samples. Thus, a prediction interval can be a useful tool to establish a regional background and assess trace metal enrichment.