Analysis of hazardous PAHs in black crusts deposited on the façades of three ancient monuments of Morocco

H. HASSOUN¹ | S. FOUDEIL¹ | T. LAMHASNI¹ | S. AIT LYAZIDI¹ | M. HADDAD¹ | A. BEN-NCER² | A. BONAZZA³ | N. GHEDINI³ | C. SABBIONI³
(¹LASMAR, URAC11, Faculté des Sciences, Université Moulay Ismail, Zitoune, Meknès | 2INSAP, Ministère de la Culture, Institut National des Sciences de l’Archéologie et du Patrimoine, Rabat, Morocco | ³Institute of Atmospheric Sciences and Climate, ISAC-CNR, Bologna, Italy)

Application of constant wavelength synchronous fluorescence

Abstract:
Air pollution accelerates the deterioration of buildings’ façades of monuments located in urban areas. The dry and wet deposition of air pollutants is demonstrated to be the most important damage factor in building material deterioration. The present work focuses on the analysis of PAHs mixture adsorbed in black crusts deposited on the façades of three ancient Mediterranean monuments built in calcarenite. They are:

1. the Burg al-klab tower and the surrounding ramparts of Salé dating back to the end of the 12th century and constructed during the Almohad period embodying Moroccan-Andalusian cross-influences, and
2. ii) Alqods Mosque of Casablanca dating back to the beginning of the 20th century.

Black crusts were taken at different points on the surfaces of the buildings; PAHs were extracted by dissolving the crusts samples in acetonitrile. Constant wavelength synchronous fluorescence spectra were carried out at many ∆ λ offsets, from 7 to 200 nm varied by 1 nm step. The sixteen most hazardous PAHs were identified in the black crusts sampled; they are classified in seven groups according to their fluorescence peaks positions: i) Fluorene and Naphthalene, ii) Acenaphthene, iii) Pyrene, Phenanthrene and Chrysene, iv) Anthracene, Benzo (a) anthracene, and Dibenzo (a,h) anthracene, v) Benzo (a) pyrene, Benzo (b) fluoranthene, Benzo (k) fluoranthene, Benzo (g, h, i) perylene and Fluoranthene, vi) Perylene and vii) Indeno (1, 2, 3 – cd) pyrene appearing respectively in the emission wavelength ranges 300 – 325 nm, 325 – 350 nm, 350 – 375 nm, 375 – 400 nm, 400 – 435 nm, 435 – 455 nm and 455-485 nm.
The origin of these hazardous PAHs is very likely the same; the edifices are located near high traffics zones. Furthermore, PAHs content of black crusts deposited on monument facades must be taken into account to establish intervention procedures and design security measures for workers protection during cleaning and restoration operations.

Keywords: air pollution, deterioration of buildings’ façades of monuments, urban areas