Critical evaluation of different methods to calculate the Geoaccumulation Index for environmental studies: A new approach for Baixada Santista - Southeastern Brazil

Although the Igeo is widely used in heavy metal contamination studies, its application differs in each study in terms of the mathematical equation used, the chosen background, and whether the fine fraction or whole sediment matrix is used. This study aims to assess these different methods, propose a new equation to calculate this index and use the index to evaluate the environmental quality of Baixada Santista. The levels of heavy metals were quantified in fifty sediment samples using both in the whole sediment sample and only in the fine fraction. The index was calculated in both fractions and in the normalized levels. Using the fine fraction of the sample was more suitable to the classification. The ratio of the levels in the whole sediment to the fine content did not present a significant statistical difference compared to the levels obtained from the fine fraction. Based on this study, a new equation is proposed for use in future environmental studies.