Characterization Of Atmospheric Pollutants Inside Emperor Qin’s Terra-cotta Museum And Their Adverse Effects

In this study,a comprehensive atmospheric pollutant monitoring was adopted for 2 years, including gaseous air pollutants(SO2, NOx, O3, and NH3), PM2.5, and dustfall inside and outside on-site archeological Pit 1 in the Emperor Qin’s Terra-cotta Museum. The objectives were to characterize the temporal and spatial variation of compositions in PM2.5 and dustfall, to analyze the particle morphologies and number concentrations of various chemical components in dustfall, to explore the source and sink of different pollutants and their relationship with tourists through comparison with past work. The potential hazards from indoor atmospheric pollutants were evaluated as followed:In 2010~2011, the indoor and ourdoor annually- averaged PM2.5 mass concentrations were 88.5±53.8 μg·m-3 and 118.2±73.1 μg·m-3,which were 29.7 μg·m-3 and 26.6 μg·m-3 lower than those in 2006~2007, respectively. The seasonally–averaged PM2.5 mass concentrations were 69.4±50.1 μg·m-3 in spring, 65.7±31.1 μg·m-3 in summer,113.8±61.6 μg·m-3 in autumn, and 106.5±58.2 μg·m-3 in winter, 26.6 μg·m-3, 31.2 μg·m-3, 21.5 μg·m-3, and 41.8 μg·m-3 lower than the respective seasons in 2006~2007. Furthermore, the summer and winter PM2.5 mass concentrations were 42.7μg·m-3 and 135.8 μg·m-3 lower than those in 2006~2007, respectively. The results implied a continueous decrease of airborne particulate matters both inside and outside the museum. This trend was also consistent with the ambient monitoring record in Xi’an city.The main chemical components of indoor PM2.5 were organic materials(28.7%), sulfate(24.8%), geological materials(20.6%), nitrate(12.9%), ammonium(7.0%), and elemental carbon(4.7%), and the predominate components of indoor dustfall were geological materials(54.1%), organic materials(13.3%), sulfate(4.4%), nitrate(2.9%), elemental carbon(1.7%), and ammonium(<0.1%), respectively. By comparing the material balance of PM2.5 and dustfall, secondary soluble salt dominated in PM2.5(44.6%)and geological materials dominated in dustfall(54.1%). Sulfate and nitrate were summed up to only 7.3% with neglectable ammonium in dustfall, implying chemical transformation of soluble salt before deposition or the existence of soluble salt as submicron particles which were hardly deposit indoors. Therefore, the short-term(days and months) potential adverse effects in museum was physical hazard as covering, soiling and abrasion by particles, and those long-term(>10 years) ones were chemical hazard as acidic erosion and salt weathering.In this study, it is the first time indoor PM2.5 and dustfall were monitored comprehensively inside an on-site museum in China. By collecting dustfall using quartz and polycarbonate filters simultaneously, number concentrations based on individual particle analysis and mass concentrations based on bulk chemical analytical techniques were incorporated to provide basic database for protective conservation and improvement of environment in museums. The methodology in this study may also be used in other researches to indoor particulate matters.