Preminary Research on Salinity and Moisture content inside the Rock Structure of Cave 98,Mogao Grottoes

摘要

Cave 98 of Mogao Grottoes,Dunhuang is located at the lower level,in the middle of the southern section.It was constructed in the Five Dynasties,when Cao Yijin was the Commander (AD914～AD935),and it is the most valuable and representative cave of the period.Like all other caves in Mogao Grottoes,it has been affected by the natural environment and there are deteriorations,such as flaking,detachment and disruption.From the bole drilled at the lower portion of the western wall,where there is no painting,samples have been obtained for salinity analysis.Temperature and humidity have also been measured inside the hole.Analysis of the electrical resistivity data from south to north of the lower portion of the western wall indicates that the soluble salt contents of the rock structure are mainly vitriolic and chloride,and mainly concentrated between the surface and the depth of 35 cm.The average salinity is 3928mg/kg.Water condensation occurs in the rock structure at depth of 125 cm.Insider the rock structure,there is close correlation between temperature,humidity and salinity.When moisture content rises,salinity drops.Due to the high humidity and abundant supply of salt,the salinity of the western wall,which backed by the main cliff structure,is higher than the other walls,and is more sensitive to changes in the environment.This explains the more serious deterioration of the western wall.