Comparative Study of Deterioration in Built Heritage in a Coastal Area: Barbanza Peninsula (Galicia, NW Spain)

Abstract

The Barbanza Peninsula (Galicia, NW Spain) is located on the west coast of Galicia. It is a narrow tongue of terrain with an area of 416 km2 and a high altitudinal gradient, with the top having a maximum height of more than 600 m at a distance of less than 5 Km from the sea. As a result of this, there is a significant rainfall gradient (from 900 to more than 3300 mm per year). In the peninsula, there are valuable historical buildings built with granite rock that show variable decay patterns. In this work, we have considered 14 of them, located in several parts of the peninsula, and we have studied their deterioration patterns. Some of them are close to the sea, with sea salt being a possible cause of decay, while for those located far from the sea, the high humidity and rainfall can be the most important cause of decay. A macroscopic study was carried out to determine the deterioration patterns. We have also analyzed the possible role of salts in the decay by using X-ray fluorescence as a screening technique to assess the presence of salts and the possible correlation of salts with the distance to the sea and using scanning electron microscopy to directly identify salts in some of the buildings. The most frequently reported decay is due to lichen growth (biological colonization). Depending on the proximity to the coast, the study area was divided into two zones: zone 1, closer to the sea (<1 km), with an important influence of sea salts and wind, and zone 2, further from the sea, with higher altitudes (center of the peninsula) and important rainfall, humidity, and therefore, biological colonization of stone surfaces. Crusts (to a lesser degree, because it is a mainly rural area) are more frequent in zone 1, but the state of conservation of stone in zone 1 is better than that in zone 2, possibly due to the concentration of urban centers in this zone and more interventions for cleaning stone surfaces. Finally, although we did not observe clear patterns in the appearance of salts in the buildings in agreement with the distance to the sea, we observed different patterns of salts in two of the buildings, one in each zone, which clearly show that, to some extent, salts are involved in decay.