학술논문
Stable isotopes as tracers of copper corrosion in the atmosphere and soil environment : a geographic study on brochantite and malachite formations on historic and archaeological material using δ18O, δ13C and δ2H
Document Type
Electronic Thesis or Dissertation
Author
Source
Subject
Language
English
Abstract
A refined methodology using light stable isotopes in precipitation to determine the formation location of copper minerals is tested, for the eventual use on archaeological bronzes that corroded in the soil environment. To do this, δ18 O in historic brochantite and archaeological malachite is used to determine whether the region in which these common minerals formed may be identified when the δ18 O is a function of the δ18 O in meteoric water and temperature. The waters in each phase of the hydrologic cycle have distinct isotopic compositions and can yield information on climate or water provenance. The possibility that this δ18 O study can be supplemented by including the hydroxyl-δ2 H in brochantite or δ13 C in malachite is explored as sub-studies. This study shows no significant difference between the δ18 OSO4 in brochantite, and the δ18 OSO4 variances are about equal among the cities considered. Furthermore, there is no statistically significant correlation between δ18 OSO4 or hydroxyl-2H and the δ18 O in precipitation, precipitation amount, pH, surface temperature, latitude, or age of deposit. About 50% of brochantite’s δ18 OSO4 is sourced from local meteoric water. Of the three SO2 → SO4 pathways that contribute oxygen in brochantite, oxygen percentages can be calculated for two pathways at a time. The malachite data shows significant difference between the geographic groups surveyed, but does not suggest a statistically significant relationship between the δ18 O or δ13 C in malachite and the δ18 O in local precipitation or surface temperature. A significant relationship is apparent between δ18 O and δ13 C with some clustering within sample sites. Therefore, a comprehensive study into the δ13 C of malachite would be worthwhile. Climate-focused research also shows potential. This work can be used to advise on authenticity issues or guide in provenance studies when choosing between suspected sites. Further refinement is necessary before it may be adopted for cases without suspected formation sites.