Ancient coins: cluster analysis applied to find a correlation between corrosion process and burial soil characteristics

Although it is well known that any material degrades faster when exposed to an aggressive environment as well as that "aggressive" cannot be univocally defined as depending also on the chemical-physical characteristics of material, few researches on the identification of the most significant parameters influencing the corrosion of metallic object are available

Atmospheric bronze and copper corrosion as an environmental indicator. A study based on chemical and sulphur isotope data

Corrosion products have been taken from 130 copper or bronze outdoor objects all over Europe. Their chemical composition and crystal symmetry have been determined by means of scanning electron microscopy (SEM/EDS) and X-ray powder diffraction. Data on location, sampling, object characteristics, general environment and air pollution level; type, colour and chemical composition of the corrosion layers have been obtained and evaluated by multivariate statistical analysis. The results verify that the highest air pollution levels are usually associated with the occurrence of thick, black or dark grey corrosion layers on copper or bronze objects, preferentially containing soot, iron oxide hydroxides, and antlerite, Cu- 3(SO4)(OH)(4). Pale green corrosion usually contains brochantite, Cu-4(SO4)(OH)(6), and is rather associated with less polluted areas. Atacamite, a copper hydroxide chloride with the chemical formula Cu2Cl(OH)(3), is preferentially observed in coastal regions. In addition, sulphur isotope analyses have been performed on eleven corrosion samples from city centers. The delta S-34 values are typically in the region from +4 to +6 parts per thousand relative to the sulphur isotope standard CDT (Canyon Diablo Troilite) with a mean value of 4.7 +/-1.2 (1 sigma), thereby indicating that the sulphur in the corrosion layers, in the form of brochantite or antlerite, mainly originates from a similar source despite geographic variation, most likely sulphur contained in air pollutants

Deterioration of archaeological bone - a statistical approach.

The degradation of archaeological bone material in Sweden was studied (i) by examinating bone specimens, the surrounding soil and the local environment at excavations in progress, and (ii) by studying the reports of earlier excavations. Conventional and multivariate statistical methods applied to the data sets show that the degradation increases with time in the soil, and that the recent soil acidification is disastrous for the inorganic fraction of bone material. It is also observed that calcareous soil, the presence of organic matter in the soil, a deep grave, or a coffin of wood usually has a preserving effect. The empirical fact that bones of children deteriorate more than those of adults is confirmed, but no clear relation can be established between bone deterioration and soil type. The deterioration of the organic content and the histological microstructure is to a large degree dependent on microbial attack and unknown factors such as diseases, living conditions, or burial traditions