The relevance of the use of ionic chromatography for the quantification of soluble salts in the analysis of built heritage: Improving the European norms

Abstract

A soluble salt analysis is crucial in the evaluation of the conservation state of the built heritage. In this sense, there are European norms that indicate the way to measure them and the levels that are hazardous. However, in those norms, only a few anions are included, the cations are undervalued, and the required analysis is not simultaneous. All of these could lead to incorrect conclusions because of the lack of representativeness of the real situation. Moreover, there are incongruences observed in the norms, because although the levels of some anions are established the quantitative analysis is only recommended. In this work it is demonstrated how the quantitative analysis of anions and cations is crucial for the correct understanding of the conservation state of a historical building under conservation works. For that, a specific ionic chromatographic system has been designed that provides the analysis of anions, cations and carbonate/bicarbonate in a simultaneous way and it was applied in brick and mortar samples for the study of Punta Begoña Galleries. In this way, it was possible to identify the affection depending on the studied materials, being the atmospheric acid gases the main problems to the mortar and the rainwater and marine aerosol for bricks. Moreover, the damage level of the analysed areas was quantified and the most critical points to be restored were identified. This work demonstrates the need of a change of mind in the soluble salt analysis regarding the ions included in the norms and the way to measure them.