Comensoli Lucrezia, Maillard Julien, Albini Monica, Sandoz Frederic, Junier Pilar, Joseph Edith
Laboratory of Microbiology, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland.
Laboratory of Technologies for Heritage Materials, Institute of Chemistry, University of Neuchâtel, Neuchâtel, Switzerland.
Appl Environ Microbiol. 2017 Apr 17;83(9). doi: 10.1128/AEM.03478-16. Print 2017 May 1.
Iron artifacts are common among the findings of archaeological excavations. The corrosion layer formed on these objects requires stabilization after their recovery, without which the destruction of the item due to physicochemical damage is likely. Current technologies for stabilizing the corrosion layer are lengthy and generate hazardous waste products. Therefore, there is a pressing need for an alternative method for stabilizing the corrosion layer on iron objects. The aim of this study was to evaluate an alternative conservation-restoration method using bacteria. For this, anaerobic iron reduction leading to the formation of stable iron minerals in the presence of chlorine was investigated for two strains of (strains TCE1 and LBE). Iron reduction was observed for soluble Fe(III) phases as well as for akaganeite, the most troublesome iron compound in the corrosion layer of archaeological iron objects. In terms of biogenic mineral production, differential efficiencies were observed in assays performed on corroded iron coupons. Strain TCE1 produced a homogeneous layer of vivianite covering 80% of the corroded surface, while on the coupons treated with strain LBE, only 10% of the surface was covered by the same mineral. Finally, an attempt to reduce iron on archaeological objects was performed with strain TCE1, which led to the formation of both biogenic vivianite and magnetite on the surface of the artifacts. These results demonstrate the potential of this biological treatment for stabilizing archaeological iron as a promising alternative to traditional conservation-restoration methods. Since the Iron Age, iron has been a fundamental material for the building of objects used in everyday life. However, due to its reactivity, iron can be easily corroded, and the physical stability of the object built is at risk. This is particularly true for archaeological objects on which a potentially unstable corrosion layer is formed during the time the object is buried. After excavation, changes in environmental conditions (e.g., higher oxygen concentration or lower humidity) alter the stability of the corrosion layer and can lead to the total destruction of the object. In this study, we demonstrate the feasibility of an innovative treatment based on bacterial iron reduction and biogenic mineral formation to stabilize the corrosion layer and protect these objects.
铁器文物在考古发掘的发现中很常见。这些物品上形成的腐蚀层在其被发掘后需要进行稳定处理，否则该物品很可能因物理化学损伤而遭到破坏。目前用于稳定腐蚀层的技术耗时较长且会产生有害废弃物。因此，迫切需要一种替代方法来稳定铁器文物上的腐蚀层。本研究的目的是评估一种使用细菌的替代性保护修复方法。为此，针对两株[具体细菌名称未给出]（菌株TCE1和LBE），研究了在有氯存在的情况下导致形成稳定铁矿物的厌氧铁还原过程。观察到可溶性Fe(III)相以及考古铁器文物腐蚀层中最麻烦的铁化合物——针铁矿发生了铁还原。在对腐蚀铁试片进行的试验中，就生物成因矿物的生成而言，观察到了不同的效率。菌株TCE1产生了一层覆盖80%腐蚀表面的均匀蓝铁矿层，而在用菌株LBE处理的试片上，只有10%的表面被相同矿物覆盖。最后，用菌株TCE1对考古文物上的铁进行还原尝试，并在文物表面形成了生物成因蓝铁矿和磁铁矿。这些结果证明了这种生物处理方法在稳定考古铁器方面的潜力，是传统保护修复方法的一种有前景的替代方案。自铁器时代以来，铁一直是制造日常生活用品的基本材料。然而，由于其反应活性，铁很容易被腐蚀，所制造物品的物理稳定性面临风险。对于考古文物来说尤其如此，在其被埋藏期间会形成潜在不稳定的腐蚀层。发掘后，环境条件的变化（例如，较高的氧气浓度或较低的湿度）会改变腐蚀层的稳定性，并可能导致文物的完全破坏。在本研究中，我们证明了基于细菌铁还原和生物成因矿物形成的创新处理方法在稳定腐蚀层和保护这些文物方面的可行性。
