Abstract Monitoring surface moisture content (MC)is a required activity and a topic of current interest in conservation studies. The present work examines the possibility of using the spectral reflectance factor at 970 nm (Rλ970) for the noninvasive quantitative determination of surface MC in building materials. Indeed, the quantification of surface liquid water by optical measurements is poorly exploited on porous media despite it is well documented in many remote sensing technologies such as in agriculture, soil science and some industrial application. The measurements apparatus is tested in a laboratory experiment on different specimens of building materials. The custom-made detector is a Si-core Avalanche Photo Diode (APD) operating in Geiger mode which satisfy the requirements of non-invasiveness and ease of use with the additional opportunity for developing economic, automated and reliable solutions. The results obtained for six representative cultural heritage building materials clearly show the dependence between Rλ970 and surface SMC: Rλ970 increases as surface MC decrease following the drying process of an unsaturated porous matrix i.e. evaporative flux supported by capillary pumping. This work reports the possibility to use the reflectance value at a specific wavelength for an alternative and non-invasive measurements of MC.

中文翻译：

---

用于测定多孔介质中水分含量的光学反射仪

摘要 监测地表含水量 (MC) 是一项必要的活动，也是当前保护研究中的一个热点。目前的工作研究了使用 970 nm (Rλ970) 的光谱反射系数对建筑材料中的表面 MC 进行无创定量测定的可能性。事实上，尽管在农业、土壤科学和一些工业应用等许多遥感技术中都有很好的记录，但通过光学测量对地表液态水的量化在多孔介质上的利用很少。测量仪器在不同建筑材料样本的实验室实验中进行测试。定制的探测器是在盖革模式下运行的硅芯雪崩光电二极管 (APD)，它满足非侵入性和易用性的要求，并为开发经济、自动化和可靠的解决方案提供了额外的机会。六种代表性文化遗产建筑材料的结果清楚地表明了 Rλ970 与表面 SMC 之间的相关性：Rλ970 随不饱和多孔基质干燥过程后表面 MC 的减少而增加，即毛细管泵支持的蒸发通量。这项工作报告了使用特定波长的反射率值进行 MC 的替代和非侵入性测量的可能性。六种代表性文化遗产建筑材料的结果清楚地表明了 Rλ970 与表面 SMC 之间的相关性：Rλ970 随不饱和多孔基质干燥过程后表面 MC 的减少而增加，即毛细管泵支持的蒸发通量。这项工作报告了使用特定波长的反射率值进行 MC 的替代和非侵入性测量的可能性。六种代表性文化遗产建筑材料的结果清楚地表明了 Rλ970 与表面 SMC 之间的相关性：Rλ970 随不饱和多孔基质干燥过程后表面 MC 的减少而增加，即毛细管泵支持的蒸发通量。这项工作报告了使用特定波长的反射率值进行 MC 的替代和非侵入性测量的可能性。