Integration of georeferenced informed system and digital image analysis to asses the effect of cars pollution on historical buildings R. Ortiz a,⇑ , P. Ortiz a , M.A. Vázquez b , J.M. Martín a a Universidad Pablo de Olavide, Department of Physical, Chemical and Natural Systems, Carretera de Utrera Km 1, ES-41013 Sevilla, Spain b Department of Crystallography, Mineralogy and Q.A., Calle Profesor García González, S/N, ES- 41072 Sevilla, Spain highlights  Risk analysis for decision making for traffic control measures in historical cities.  A new multidisciplinary approach based on SIG, modeling maps and digital image.  A cost-effective methodology to analyse pollution in cities to improve building conservation. article info Article history: Received 4 August 2016 Received in revised form 26 January 2017 Accepted 8 February 2017 Keywords: Pollution Blackening Traffic Georeferenced system Digital image analysis Monuments abstract The blackening of buildings in historic cities due to air pollution is common. In historic urban centres, pollution from traffic negatively affects the preservation of monuments and results in the appearance of black crusts and/or deposits. The cleaning procedures for restoring or rehabilitating these building to remove these deposits are expensive and require continuous effort. Thus, it is necessary to monitor and control the effects of traffic on buildings. The objective of this study was to develop a new analytical methodology to assess and evaluate the continued risk of traffic pollution due to the circulation of vehi- cles near monument facades. This methodology combines geographic information systems (GIS) and dig- ital image analysis (DIA) to evaluate the effect of traffic on the facades of stone buildings, which will enable more informed decisions regarding the reorganisation of traffic and the pedestrianisation of streets near monuments. Ó 2017 Elsevier Ltd. All rights reserved. 1. Introduction The current developmental model of society has resulted in large cities with increasing numbers of vehicles and industrial zones. Due to air pollution, many monuments and historic build- ings have begun to deteriorate [1,2]. Motor vehicles are the largest source of air pollution in urban areas. Carbon monoxide (CO) is the most common pollutant emit- ted by vehicles. Vehicles are also a significant source of particulate emissions, NO x , and SO 2 . The negative effects of air pollution on the building materials of monuments are well-known; particles may accumulate on the building surface, affecting its outward aspect, in addition to chemical reactions of pollutants with building mate- rials [3]. Deposits and crusts on buildings are basically generated by two phenomena: dry and wet deposition. In dry deposition, pol- lutants adhere directly to the stone surface. In wet deposition, blackening is produced by oxidation of gas, such as SO 2 or NO x , in the presence of catalysers resulting in the formation of different acids (principally H 2 SO 4 and HNO 3 ) that begin to dissolve the stone surface. This phenomenon occurs extensively with materials com- posed of carbonates, such as marble, limestone, and calcarenite. Several investigations have been completed on the impact of air pollution on cultural heritage [4–6] and the appearance of mechanical damage [7] or black crust due to traffic and atmo- spheric SO 2 [8,9]. These studies demonstrate that walls directly exposed to traffic have higher concentrations of sulphate, nitrate, and organic carbon. The damage layers in blackening and black crust [6] are a record of the environmental changes over time, and some differences in thickness exist [10] from different exposures to vehicular traffic. Black crusts generated by pollution should be periodically removed from buildings using lasers, superficial cleaning, pressure washing, or chemical products, which may tangibly or intangibly damage these sites of historical significance. The expense associ- ated with these restoration projects varies based on the costs of http://dx.doi.org/10.1016/j.conbuildmat.2017.02.030 0950-0618/Ó 2017 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: rortcal@upo.es (R. Ortiz). Construction and Building Materials 139 (2017) 320–333 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat