敦煌莫高窟壁画地仗层可溶盐迁移过程模拟研究

钱玲; 吕功煊; 胡红岩; 陈港泉

doi:10.16495/j.1006-3757.2023.02.003

敦煌莫高窟壁画地仗层可溶盐迁移过程模拟研究

doi: 10.16495/j.1006-3757.2023.02.003

1.
中国科学院兰州化学物理研究所，羰基合成与选择氧化国家重点实验室，甘肃兰州　730000
2.
敦煌研究院，甘肃敦煌　736200

基金项目: 国家自然科学基金重点项目（51732008），甘肃省自然科学基金创新基地和人才计划项目（20JR5RA565）

详细信息

作者简介:
钱玲（1979−），女，高级工程师，主要从事文物保护与环境催化工作，E-mail：qianl@licp.cas.cn

通讯作者:
吕功煊（1964−），男，研究员，主要从事能源与环境催化工作，E-mail：gxlu@licp.cas.cn

中图分类号: O657; O793
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- 被引次数: 0
出版历程
- 收稿日期: 2023-01-18
- 录用日期: 2023-02-27
- 修回日期: 2023-02-27
- 刊出日期: 2023-06-30

Simulation Study on Salt Migration Process of Fresco Floor Layer in Dunhuang Mogao Grottoes

1.
State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China
2.
Dunhuang Academy, Dunhuang 736200, Gansu China

Funds: National Natural Science Foundation of China (51732008), Natural Science Foundation of Gansu (20JR5RA565)

摘要

摘要: 采用莫高窟壁画的地仗层制作材料与工艺制备了不同盐分含量及组成的模拟土柱，并在柱体不同位置加入氧化铝小球作为盐分迁移的探针，以考察硫酸钠与氯化钠两种盐分在土柱内部的分布、迁移及在柱体表面的结晶行为. 为了探查壁画的地仗层组分差异和孔体性能的不同对盐分迁移与结晶过程的影响，对放置在不同位置的探针小球和同一位置土体进行采样，利用比表面积/孔隙度分析（BET）和扫描电子显微镜-能谱（SEM-EDS）等方法考察不同孔结构及性能对水盐运移与分布的影响，及不同盐分在模拟柱表层的探针小球和土体表面结晶表现的差异. 离子色谱（IC）法用来分析在模拟柱的不同高度处所含盐离子浓度，以考察其在柱体中的迁移性能和分布特征，进而得到壁画地仗层的组分不同对水盐运移及盐分结晶的影响. 结果表明：水盐运移介质的孔道性能与结构对盐害的产生与发展有较大影响，当地仗层中麦草含量较多时有利于水盐溶液向地仗表层迁移，而细麻的存在增加了土体中介孔数量，两者均促使了盐分在更接近地仗表层的位置成核结晶，对表层壁画的存在造成威胁. 盐分的结晶表现与盐害机理也有所不同，硫酸钠更易在模拟土柱表层土质中结晶，而氯化钠则主要在氧化铝小球表层结晶，当两种盐分同时存在时，主要表现为氯化钠在土柱表面氧化铝小球的结晶，土体表层的盐分结晶反而减弱.
- 莫高窟 /
- 壁画 /
- 遗址土 /
- 水盐运移 /
- 硫酸钠 /
- 氯化钠 /
- 盐害
Abstract: The simulated earthen columns with different salt contents and compositions were prepared with the aid of materials and techniques used to produce the fresco floor layer of the Mogao Caves murals. The alumina spheres were placed at different locations of the column as the salt migration probes to investigate the distribution and migration of sodium sulfate and sodium chloride and their crystallization behavior on the surface of the column. In order to investigate the effect of differences in components and pore properties of the fresco floor layer of the Mogao Caves murals on salt migration and crystallization processes, probe pellets placed at different locations and soil at the same location were sampled. The effects of different pore structures and properties on water-salt transport and distribution, and the differences in the crystalline behavior of probe pellets and soil surfaces on the surface of the simulated earthen columns for different salts were investigated by Brunner-Emmet-Teller measurements (BET), scanning electron microscopy-energy spectroscopy (SEM-EDS), and other methods. The ion chromatographic (IC) method was used to analyze the salt ion concentration at different heights of the simulated earthen column to detect its migration properties and distribution characteristics, so as to obtain the effect of different components of the fresco floor layer of the Mogao Caves murals on water-salt transport and salt crystallization. The results showed that the pore properties and structure of the water-salt transport medium have a great effect on the generation and development of the salt damage. The high content of wheatgrass in the fresco layer is conducive to the migration of water and salt solution to the surface of the fresco layer, while the presence of fine linen enables the increases of the number of soil mesoporous in the soil, both of which promote the nucleation and crystallization of the salt closer to the surface of the fresco layer, posing a threat to the existence of surface murals. The crystallization behavior of salts and mechanism of salt damage are also different. Sodium sulfate is more likely to crystallize on the surface soil layer of the simulated earthen column, while sodium chloride mainly crystallizes on the surface layer of alumina pellets. When the two salts are exist simultaneously, the crystallization of sodium chloride mainly occurs on the surface of alumina pellets on the simulated earthen column, but the crystallization of salt on the surface layer of the soil is weakened.
- Mogao Caves /
- murals /
- earthen site soil /
- migration of water and salt solution /
- sodium sulfate /
- sodium chloride /
- salt damage

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图 1 模拟土柱示意图

Figure 1. Schematic diagram of simulated earthen column

下载: 全尺寸图片幻灯片

图 2 盐分在土柱表面土层及探针小球上结晶形貌

（a）D①含Na₂SO₄，（b）D②含NaCl，（c）D③含Na₂SO₄&NaCl

Figure 2. Crystal morphology of salt on soil layer and probe pellets on surface of simulated earthen column

(a) D① containing Na₂SO₄, (b) D② containing NaCl, (c) D③ containing Na₂SO₄&NaCl

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图 3 小球的（a）N₂吸附-脱附等温线和（b）孔径分布图

Figure 3. (a) N₂ adsorption-desorption isotherms and (b) pore size distribution of pellets in simulated earthen column

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图 4 模拟柱土样的（a）N₂吸附-脱附等温线和（b）孔径分布图

Figure 4. (a) N₂ adsorption-desorption isotherms and (b) pore size distribution of soil sample in simulated earthen column

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图 5 土柱含盐试块SEM形貌及元素分析

Figure 5. SEM images and elemental analysis of soil samples containing salt in simulated earthen column

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图 6 小球表面及内部盐分形貌

表面：（a）NaCl，（b）Na₂SO₄. 内部：（c）NaCl，（d）Na₂SO₄

Figure 6. SEM images of surface of pellets and internal salt morphology

surface of pellets : (a) NaCl, (b) Na₂SO₄. pellets inside: (c) NaCl, (d) Na₂SO₄

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图 7 （a）Na₂SO₄及（b）NaCl在各组模拟柱的土层及探针小球中运移及分布情况

Figure 7. Migration and distribution of (a) Na₂SO₄ and (b) NaCl in soil layer and probe pellets of each simulated earthen column

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图 8 NaCl & Na₂SO₄在（a）A、（b）B、（c）C和（d）D模拟柱中的各取样层离子分布

Figure 8. Ion distribution of NaCl & Na₂SO₄ in each sample layer in simulated earthen column of (a) groups A, (b) B, (c) C and (d) D

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表 1 模拟土柱各组分及盐分含量

Table 1. Composition and salt content of simulated earthen columns /g

	土	沙	水	细麻	粗麦	Na₂SO₄		NaCl
	土	沙	水	细麻	粗麦	序号	质量	序号	质量
A	360	180	150	0	0	①	54	①	0
						②	0	②	54
						③	27	③	27
B	360	180	150	15	0	①	54	①	0
						②	0	②	54
						③	27	③	27
C	360	180	150	0	15	①	54	①	0
						②	0	②	54
						③	27	③	27
D	360	180	150	7.5	7.5	①	54	①	0
						②	0	②	54
						③	27	③	27

下载: 导出CSV

表 2 土柱土体样品的XRF表征结果

Table 2. XRF analysis of soil in simulated earthen column /%

	Na₂O	MgO	Al₂O₃	SiO₂	K₂O	CaO	Fe₂O₃	所归属可能矿物
土	2.325	7.936	13.553	54.563	2.680	12.136	5.504	伊利石、绿泥石
细沙	3.624	4.335	9.751	67.744	1.798	9.475	2.596	石英、长石、方解石

下载: 导出CSV

表 3 样品的结构表征分析

Table 3. Structural analysis of pellets and soil in simulated earthen column

Sample	S_BET/ (m²/g)	Pore volume/ (cm³/g)	Average pore size/nm
空白小球	160.16	0.471	11.35
含Na₂SO₄小球	108.10	0.337	11.26
含NaCl小球	116.41	0.455	13.84
含Na₂SO₄+NaCl小球	106.40	0.359	12.94
土柱模拟土	6.03	0.022	11.13
土柱模拟土（含麻）	5.78	0.020	15.01
土柱模拟土（含麻+麦）	4.65	0.019	16.78

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