Luciana Randazzo

Natural and anthropogenic sources of total suspended particulate and their contribution to the formation of black crusts on building stone materials of Catania (Sicily)

Blackening and disaggregation of exposed surfaces of stone monuments are well-known effects of stone decay taking place in polluted urban environments all over the world. This paper aims to assess the contribution of natural and anthropogenic sources of total suspended particulate (TSP) causing permanent damage (black crusts) to the stone monuments of Catania (Sicily), one of the most popular “cities of art” of southern Italy. Atmospheric pollution of Catania, a typical Mediterranean coastal town, is mainly contributed by vehicle exhaust emissions rather than industrial ones. Episodically, the city also suffers gaseous and ash emissions (plumes) from the nearby Mount Etna volcano. Thus, to discriminate between natural and anthropogenic contributions to stone decay on Catania monuments, black crusts and TSP were sampled within the urban area and subjected to specific analytical procedures (optical microscopy, X-ray powder diffraction, Fourier transformed infrared spectroscopy, scanning electron microscopy equipped with energy dispersive spectrometry, ionic chromatography and dual inlet mass spectrometry). Mineralogical, chemical and isotopic characterization of black crusts and TSP provided new insights concerning the partition of sulfate sources in this particular urban context. The influence of Mount Etna emissions on both TSP and black crusts compositions was shown. Nevertheless, the key role of anthropogenic sources in the total sulfate budget was confirmed, while sea spray and volcanic emissions were found to make subordinate contributions. Quantitative data useful for the identification of the threshold pollution levels for preventive conservation of Catania monuments were obtained.

Geomaterials in green building practices: comparative characterization of commercially available clay-based plasters

Three pre-mixed powdered clay-based (earthen) plasters produced in Europe and specifically designed for wall undercoating were analyzed in this paper. These materials are commercially available and successfully employed in green building practices all over the world. Their compositional and textural characteristics, as well as plastic behaviour were investigated through a multi-analytical approach: X-ray powder diffraction (XRPD), polarized light microscopy (PLM), X-ray fluorescence spectrometry (XRFS), scanning electron microscopy equipped with an energy dispersive spectrometer (SEM-EDS), mercury intrusion porosimetry (MIP), grain-size distribution (GSD) and semi-empirical tests (Atterberg Limits, Linear Shrinkage). In addition, a natural earth (a terra rossa red soil sampled in north-western Sicily), theoretically appropriate for the production of earthen plaster, was subjected to the same analytical routine and compared with the three commercially available pre-mixed products. The achieved results allowed to individuate the compositional and textural features that primarily influence the performances of the studied earthen plasters. The obtained data are expected to be also useful in directing the selection of raw materials for local manufacture of specifically designed innovative products.

Archaeometric evidence attesting production of indigenous archaic pottery at Monte Polizzo (Western Sicily)

Excavations at the proto-urban indigenous settlement of Monte Polizzo (western Sicily) have not yielded so far any evidence of in-situ ceramic production (i.e. kiln structures). However several archaeological concerns put forward to consider it as a likely production centre of pottery during the Archaic age. In this paper a first attempt to check the compositional correspondence between ceramic fabrics and local clay sources has been made. A comprehensive archaeometric investigation of native pottery, mainly composed of matte-painted table ware dated from the 7th to the 4th century BC, recovered from the Acropolis of Monte Polizzo has allowed the identification of five distinct ‘Paste Compositional Reference Units’ (PCRUs). The five PCRUs were independently identified and confirmed through textural and mineralogical characteristics (petrographic observations) and chemical characterization (XRF analysis). A parallel investigation of clayey raw material of Monte Polizzo’s natural resources revealed two geologic formations the Terravecchia and Marnoso-Areacea del Belice (MAB). Experimental ceramic briquettes were created and mineralogically and petrographically characterized. A comparison between the native and experimental ceramics revealed that the native ceramists preferred clays from the Terravecchia Formation. The mineralogical, textural and chemical composition of the raw clays of the Terravecchia Formation resulted to be well correlated with the 92% of the native ceramic artefacts recovered from Monte Polizzo. The remaining 8% are interpreted to be imported from the Sicani Mounts area.

The production of traditional building materials in Oristano (Sardinia, Italy)

The study of ceramic-making communities which employ traditional practices can provide insights into the raw materials and techniques used over the centuries in a particular territory. The archaeometric study of ceramic products and of the raw materials used in their production is an effective complement to the existing ethnographic information. This paper focuses on the brick and tile making tradition of Oristano, a town in Central-Western Sardinia (Italy). Applying a combination of techniques, it includes an extensive analysis of traditional handmade and early industrial bricks and tiles, and a study of the local clays that may have been used as raw materials. Although we were unable to study workshops in operation, we had access to the oral testimonies of local workers regarding traditional production processes. In this sense, this is an ethnographic case study that can be considered as a semiarchaeological situation. Studies of this kind, in conjunction with ethnoarchaeometric analyses, are also useful to test some of the theoretical and methodological approaches used in archaeometric research. In this regard, the present study also explores the compositional variability of the ceramic production within the same territory.

An original experimental approach to study the alteration and/or contamination of archaeological ceramics originated by seawater burial

This paper deals with the proposal of an original experimental equipment specifically designed for appraising any compositional alteration of archaeological ceramics after the protracted contact with seawater. A series of ceramic test-pieces (briquettes and cylinders) were purposely manufactured by mixing selected calcareous or non-calcareous clays with different varieties of sieved sand temper. The aim was to reasonably simulate the ceramic pastes most frequently found in the shipwrecks recovered in the coastal areas of western Mediterranean. The used raw materials were previously characterized in terms of mineralogical and chemical composition (XRPD, XRF). The obtained test-pieces were fired under oxidizing conditions at predetermined temperatures (800 and 950°C) in a traditional ceramic kiln and their chemical composition was analyzed by XRF spectrometry. Briquettes were firstly fixed into customized Ertacetal® holders and then placed in open sea-bed environment under monitored oxidizing or reducing conditions by the Italian CNR-IAMC dockside at Granitola, north-western Sicily. At the same time, two customized glass containers for working in a confined system under continuous seawater flow were designed and realized. They were filled with bottom sediments rather different in size in order to produce either reducing or oxidizing microenvironments below the water-sediment interface. Cylinder shaped test-pieces were placed in the sediment of both the glass containers. Weekly monitoring of temperature, salinity, conductivity, pH, Eh, dissolved oxygen was carried out in both the above-described experimental settings. Comparative (before/after) XRF analyses, after 3 months of exposure to seawater, were performed on the experimental ceramic briquettes and cylinders. The obtained results provided preliminary evidences that the proposed experimental apparatus is efficiently working and a number of not negligible changes concerning major and trace elements were pointed out just after such a restricted time of exposure to seawater.