From univariate background (baseline) values towards the concept of compositional background (baseline) values

• Autores: Antonella Buccianti, B. Nisini, B. Raco
• Localización: Proceedings of the 6th International Workshop on Compositional Data Analysis: Girona, 1-7 de juny de 2015 / coord. por Santiago Thió Fernández de Henestrosa, Josep Antoni Martín Fernández, 2015, ISBN 978-84-8458-451-3
• Idioma: inglés
• Enlaces
  • Texto Completo Libro
• Resumen

  • Water geochemistry is often investigated by considering a large number of variables, including major, minor and trace elements. Some of these are usually highly correlated due to coherent geochemical behaviour, but the effect of anthropic factors tends to increase data variability, sometimes obscuring the natural laws governing their relationships. In this framework it may be difficult to identify geochemical features linked to natural phenomena as well as to separate geogenic anomalies from the anthropogenic ones or to define background or baseline concentrations for single chemical elements. This is particularly true at regional level where numerous phenomena may interact and mix together, forming a complex pattern not easy to interpret. The identification of background or baseline values is also complicated due to the compositional nature of chemical variables, so that under the Compositional Data Analysis Theory (CoDA) single background or baseline values lose their meaning. However they are fundamental references for public institutions and government policies. In this contribution a new approach is proposed aimed at investigating the regionalised structure of the geochemical data by considering the joint behaviour of several chemical elements or compositions. The approach is based on the robust CoDA theory so that the proportionality features of abundance data are fully taken into account, enhancing their relative multivariate behaviour, as well as the influence of outliers. An application example is presented for the water compositions sampled in Tuscany Region, a surface of about 23,000 km2 , a project sponsored by the regional government.