SO_(2)与水分综合影响下的云冈石窟砂岩劣化研究

Deterioration of sandstone from Yungang Grottoes under the influences of SO_(2)and moisture

气体污染物SO_(2)是造成云冈石窟文物本体劣化的重要因素之一。为厘清SO_(2)与水分耦合作用下的云冈砂岩劣化规律,开展不同SO_(2)浓度、相对湿度以及降水条件下的室内模拟风化试验,测定试样质量、表面特征和化学成分变化。结果表明:SO_(2)易与砂岩中的碳酸盐矿物(如方解石)和长石发生化学反应,产物包括CaSO_(4)·2H_(2)O、MgSO_(4)·7H_(2)O和高岭石等,且随着相对湿度增加,反应程度增大,造成试样的质量、色差值、可溶盐含量上升及硅铝比下降;液态水的参与能显著加快SO_(2)与砂岩的相互作用过程,不但增加了各项指标的变化幅度,还加大了SO_(2)入侵深度。研究成果可为砂岩质文物的科学认知和预防性保护提供参考。

The gas pollutant SO_(2)is one of the important factors causing the deterioration of cultural relics in Yungang Grottoes.In order to clarify the deterioration of Yungang sandstone in the presence of SO_(2)and moisture,indoor simulated weathering tests under different SO_(2)concentrations,relative humidity and precipitation conditions were carried out to measure the mass,surface characteristics and chemical composition changes of samples.The results show that 1)SO_(2)easily reacts with carbonate minerals(such as calcite)and feldspar in sandstone,giving rise to products including CaSO_(4)·2H_(2)O,MgSO_(4)·7H_(2)O and kaolinite,etc.,and that with an increase of relative humidity,the degree of reaction increases,resulting in an increase of sample mass,color difference,soluble salt content and a decrease of the Si/Al ratio;2)the participation of liquid water can accelerate the interaction between SO_(2)and sandstone significantly,which not only increases the variation range of various indexes,but also increases the invasion depth of SO_(2).These research results could provide a reference for scientific understanding and preventive conservation of sandstone cultural relics.