Study On The Air Environment And Preventive Protection Of Underground Culture Relics During Burial And Collection Stage

Underground buried cultural relics can survive in the long history due to their invisibility,which is almost the only witness to ancient civilization and appear to be invaluable.Its"life"track consists of three main stages:closed underground buried stage,unsealed burial stage,and unearthed collection preservation stage(artificial environment regulation period).To provide a better environment for the preservation of cultural relics.the methods of field measurement and numerical simulation were used to study the ambient air characteristics in the life cycle of cultural relics.The main contents are as follows:(1)For the closed underground burial stage,the numerical method was used to calculate the variation of the hot-humid environment after the closure of a typical underground burial chamber located in the constant temperature layer of soil in Xi’an.The results show that the thermal and humid environment therein quickly reached a stable state after the closure of the tomb,with the temperature and humidity stabilizing at 13.7℃(the average annual local temperature)and 90.2%,respectively.The temperature and humidity inside the burial chamber will remain constant until the exhumation reappears.This means that the indoor temperature of the museum collection storage room after excavation should be taken as the local average annual temperature,which provides a reference for the scientific design of the preservation temperature of excavated artifacts.(2)For the unsealed burial stage,the variation of the hot-humid environment of the tomb due to the creation of rob holes was investigated.When a single robber hole exists,it is difficult for the outside airflow in the hottest month to enter the underground chamber with 9.0 m depth;while in the coldest month,The incoming airflow exerts little effect on the environment inside the chamber due to the heating and humidifying effect of the passage.When double robber holes exist,the external climate in the coldest month has a significant influence on the thermal and humid environment inside the chamber,causing the temperature to decrease significantly and the relative humidity rises.After 300 s of internal and external penetration,the temperature and humidity almost reached stability,with the temperature stabilizing at 8～11℃and the relative humidity stabilizing at92%～94%.The external climate in the hottest month had little effect on the burial chamber.The result indicates in the process of establishing a site museum,airflow disturbances should be minimized to create a stable thermal and humid environment for underground artifacts.(3)The field test was performed to measure the air temperature,humidity,and microbial distribution in the underground chambers of different depths.The results show that the temperature and humidity are uniformly distributed in deeply buried underground chambers,and there are almost no differences in both height direction and horizontal direction.For shallowly buried underground chambers,the temperature can be maintained stable and the relative humidity fluctuates widely under natural ventilation.While the mechanical ventilation system operates,both air temperature and relative humidity vary greatly.The average concentrations of airborne fungal(852 CFU/m~3)and bacterial particles(334 CFU/m~3)in the shallow buried underground chamber,and the number of airborne fungal particles is more than that of bacteria.The dominant fungal genera are Aspergillus and Cladosporium,which is consistent with the findings of the prevalence of fungal genera in underground burial chambers.Therefore,in the underground burial space,due attention should be paid to the impact of fungi fostered on smaller particle size particles on artifacts.(4)For the unearthed collection preservation stage,the impact of artificial control measures on the ambient air of cultural relics were analyzed.A typical collection museum was selected to investigate the hot-humid environment and microbial distribution in its ventilation and air conditioning system.The results showed that the average temperature and humidity in winter(16.8℃,44.1%)were lower than those in summer(22.8℃,78.9%).The air bacterial concentration in summer was higher than that in winter and the fungal concentration was less affected by the season.Fungal concentrations were higher than bacterial concentrations in both winter and summer:for example,the air fungal concentration was about 1～6.4 times higher than the air bacterial concentration,and the dust-associated fungal concentration was about 2.5～200 times higher than the dust-associated bacterial concentration.The distribution of fungal species is not affected by climate and has a high degree of consistency.The dominant fungal genera are Penicillium,Aspergillus and Cladosporium.Airborne fungi and dust accumulation associated fungi migrate with each other,and the species genera are basically identical.To effectively reduce the concentration of airborne fungi which harmful to cultural relics,a proposal was put forward to install at least a middle efficiency filter in the air outlet terminal of the air conditioning system regulating the preservation environment of cultural relics in museums.This study reveals the variation of hot-humid environment and microbial distribution in different life stages of cultural relics,providing first-hand information and a basis for the scientific protection of excavated cultural relics.