“南海Ⅰ号”沉船木材的微束XRF面扫描分析

Mapping Analysis byμ-X-Ray Fluorescence for Waterlogged Archaeological Wood From“Nanhai No.1”Shipwreck

“南海Ⅰ号”是一艘南宋时期的木质商船,沉没于我国广东省阳江市东平港以南约20海里处,发现于1987年,经多次水下考古调查后,于2007年严格按照水下考古规范,成功地将其整体打捞出水,迄今为止中国境内发现的年代最早、船体最大、保存最完整的古沉船。由于在海底埋藏达800年之久,因此船体和及其所承载的木质文物,在海水中盐份以及各种微生物的协同作用下,发生了严重的物理化学和生物降解作用,使得原有的木材成分大量降解流失,木质纤维间的支撑力减少,导致强度降低,结构糟朽。硫铁化合物是海洋出水木材的重要病害来源,因此铁、硫元素的含量、分布以及赋存状态,对海底出水有机质材料的研究和保护具有重要的学术价值。由于制样和传统方法限制,难以对出水木材中的铁和硫进行原位无损分析,同时分析速度和测量成本亦是难以克服的困难。微束X射线荧光技术,特别是基于常规X光管的微聚焦技术,为该问题提供了便捷、快速、可靠、无损和低成本的解决方案。基于此,选择“南海Ⅰ号”出水船体为研究对象,应用最新的多导毛细管微聚焦X射线荧光光谱技术,并结合拉曼光谱分析,对出水木材中的铁、硫含量和分布进行了面扫描分析。结果指出,样品中的铁、硫元素分布不均,存在多种赋存形态,揭示了元素分布特点和规律为研究水木材中硫、铁的来源、富集以及耦合关系等提供了线索。研究表明,微束XRF技术可有效分析不规则、不均匀的饱水木材中不同部位铁、硫丰度,在二维尺度上揭示元素的分布情况以及其相关性。研究结果可为探讨海洋出水木材中的硫、铁及其化合物的沉积和循环机制以及相关文物保护和修复工作,提供重要的科学支持和有益借鉴。

“Nanhai No.1”is a wooden merchant ship from the Southern Song Dynasty of China.It sank about 20 nautical miles south of Dongping Port in Yangjiang City,Guangdong Province.It was discovered in 1987.After several underwater archaeological investigations,it was strictly followed in 2007.Under the archaeological regulations,it was successfully salvaged out of the water.So far,the oldest,largest and most intact ancient sunken ship has been discovered in China.During longtime in seabed and damaged by seawater,the waterlogged archaeological wood have undergone serious physical,chemical and biodegradation effect by salt in the seawater and various microorganisms.It is give rise to wood components are degraded and eroded,and the supporting force between wood fibers is reduced,resulting in reduced strength and decayed structure.The accumulation of sulfur and iron considered to be associated with bacterial degradation of the wood.Iron sulfides can be oxidized to form sulfuric acid,which damages the wood cellulose and results in the degradation of organic materials.Thus,the content,distribution,and occurrence of iron and sulfur elements have important academic value for the research and protection of organic materials under sea.Due to sample preparation and method limitations,traditional methods make it difficult to perform in-situ and non-destructive analysis of iron/sulfur in waterlogged wood.Also,analysis speed and cost are also hard to overcome.μ-X-ray fluorescence,especially micro-focusing technology based on commercial X-ray tubes,provides a more convenient,fast,reliable,non-destructive and low-cost solution to this problem.Based on the opinion,selected the samples of the“Nanhai No.1”shipwreck hull,applied the latest multi-capillaryμ-X-ray fluorescence spectroscopy technology,combined with Raman spectroscopy analysis,and conducted a surface scan analysis of the iron and sulfur content and distribution in the waterlogged archaeological wood.The results indicate that the distribution of iron and sulfur elements in the sample is heterogeneous,and there are multiple occurrence forms.The characteristics and rules of element distribution provide clues to reveal the sources,enrichment and coupling relationships of sulfur and iron in waterlogged wood.Studies have shown thatμ-XRF technology can effectively analyze the iron and sulfur abundance in different parts of irregular and uneven waterlogged wood and reveal the distribution of elements and their correlation on a two-dimensional scale.