金沙土遗址盐害分布与演化特征

Distribution and evolution of the salt damage at Jinsha earthen site

金沙土遗址表面存在泛盐、粉化、空鼓等盐害。对这些盐害的分布特征与演化过程的研究是科学保护金沙土遗址的第一步,也是进一步探讨盐害致病机理的前提条件。本工作收集整理了2010~2020年金沙土遗址病害调查资料,通过现场调查和图像处理技术对盐害的类型、分布特征与演化过程进行定性和定量分析;采用X射线衍射、离子色谱和扫描电镜等测定了不同高度土样的成分、盐分含量以及微观结构。结果显示金沙土遗址主要的盐害类型为表面泛盐、粉化、空鼓、片状剥蚀和掏蚀;主要分布区域是西北向走廊和古河道附近,机挖坑侧壁最为严重;在探方侧壁上盐害由上到下依次由表面泛盐过渡到单独粉化,再到空鼓和片状剥蚀,最底层为掏蚀。金沙土遗址盐害的发育过程可以概括为四个阶段,每个阶段主要发育的盐害类型不同,依次为表面泛盐、粉化、片状剥蚀和掏蚀。越到后期,各类盐害分布范围越大,发展速度越快,对土遗址破坏性越大。离子浓度沿高度的分布与毛细上升作用有关,也与病害的劣化程度和发育进程有关。硫酸钙类是导致土遗址泛盐、粉化和脱落的主要盐分之一。

The salt damage is a common problem at earthen sites.There are serious phenomena of the salt damage on the surface of Jinsha earthen site.Research on the distribution and evolution of the salt damage is the first step toward a science-based strategy to protect Jinsha earthen site,and also a prerequisite for further exploring the pathogenic mechanisms of the salt damage.In this study,we collected the existing investigation data of Jinsha earthen site from 2010 to 2020 and conducted qualitative and quantitative analyses of the type,distribution characteristics and evolution process of the salt damage at the site using the on-site investigation and image processing technology.The results show that the main types of the salt damage at Jinsha earthen site include salt efflorescence,crisp powdering,hollowing,peeling and erosion.The main distribution areas are near the northwest corridor and ancient river channels,and the sidewalls of machine-dug pits present the most serious damages.From top to bottom,the salt damage transition from salt efflorescence to single crisp powdering,then hollowing and peeling and finally erosion at the bottom layer.In later stages of all types of the salt damage,distribution ranges become larger,development rates become faster and damage degrees of earthen sites become greater.Distributions of soluble salt contents along the height are not only related to the capillary rise,but also related to the development process of the salt damage.