Atacamite discolouration under the influence of arsenates in wall paintings in the Kizil Grottoes, Xinjiang, China

IF 2.6 1区艺术学 Q2 CHEMISTRY, ANALYTICAL

Heritage Science Pub Date : 2024-08-13 DOI:10.1186/s40494-024-01406-y

Ling Shen, Jie Yang, Jiakun Wang, Shaoping Lin, Hui Zhang, Zhaozhao Liu, Zhibo Zhou

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Abstract

This study was focused on a specific blue‒green pigment applied on the edges of the green blocks of wall paintings in the Kizil Grottoes, the earliest Buddhist cave complex in China containing many wall paintings. Based on in situ portable XRF analyses, μ-Raman spectroscope, elemental analysis (SEM–EDS and EPMA-WDS) and μ-XRPD analyses, the pigment was proven to be lavendulan [NaCaCu₅(AsO₄)₄Cl·5H₂O], which has not been reported in ancient wall painting studies before. Lavendulan was found to coexist with atacamite [Cu₂(OH)₃Cl] in some of the samples in the study and showed a nanoneedle-like morphology. Further investigations of lavendulan revealed that it was probably not originally used as a pigment but was generated by the transformation of atacamite under the influence of arsenates [As(V)] and Na⁺. This phenomenon and the related mechanism were discovered in this study and are discussed in this paper. As an important cultural heritage site in the Silk Road, the Route Network of the Chang’an-Tianshan Corridor and the Kizil Grottoes are listed as UNESCO World and Natural Heritage sites. The pigment types and preservation conditions of wall paintings are similar to those of many wall paintings found along the Silk Road, and further attention should be given to this discolouration mechanism for heritage site conservation.

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中国新疆克孜尔石窟壁画中砷酸盐影响下的阿托孔石变色现象

这项研究的重点是中国最早的佛教石窟群--克孜尔石窟（包含许多壁画）中涂抹在壁画绿色块边缘的一种特殊蓝绿色颜料。根据原位便携式 XRF 分析、μ-拉曼光谱、元素分析（SEM-EDS 和 EPMA-WDS）和μ-XRPD 分析，该颜料被证实为熏杜兰[NaCaCu5(AsO4)4Cl-5H2O]，这在以前的古代壁画研究中从未报道过。研究发现，在一些样本中，拉芬杜兰与阿塔卡明石[Cu2(OH)3Cl]共存，并呈现出纳米针状形态。对拉文杜兰的进一步研究发现，它最初可能并不是用作颜料，而是在砷酸盐[As(V)]和 Na+ 的影响下，由阿塔卡明石转化生成的。本研究发现了这一现象及其相关机理，并在本文中进行了讨论。作为丝绸之路的重要文化遗产地，长安-天山廊道路网和克孜尔石窟被联合国教科文组织列为世界遗产和自然遗产。壁画的颜料类型和保存条件与丝绸之路沿线发现的许多壁画相似，在遗产地保护中应进一步关注这种变色机制。

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来源期刊

Heritage Science Arts and Humanities-Conservation

CiteScore

4.00

自引率

20.00%

发文量

183

审稿时长

19 weeks

期刊介绍： Heritage Science is an open access journal publishing original peer-reviewed research covering: Understanding of the manufacturing processes, provenances, and environmental contexts of material types, objects, and buildings, of cultural significance including their historical significance. Understanding and prediction of physico-chemical and biological degradation processes of cultural artefacts, including climate change, and predictive heritage studies. Development and application of analytical and imaging methods or equipments for non-invasive, non-destructive or portable analysis of artwork and objects of cultural significance to identify component materials, degradation products and deterioration markers. Development and application of invasive and destructive methods for understanding the provenance of objects of cultural significance. Development and critical assessment of treatment materials and methods for artwork and objects of cultural significance. Development and application of statistical methods and algorithms for data analysis to further understanding of culturally significant objects. Publication of reference and corpus datasets as supplementary information to the statistical and analytical studies above. Description of novel technologies that can assist in the understanding of cultural heritage.