key: cord-0786209-afesq2ka authors: Deng, Jialin; Jiang, Luman; Miao, Wenwen; Zhang, Junke; Dong, Guiming; Liu, Ke; Chen, Juncheng; Peng, Tong; Fu, Yao; Zhou, Yunpei; Huang, Xue; Hu, Mengqian; Wang, Fang; Xiao, Lin title: Characteristics of fine particulate matter (PM(2.5)) at Jinsha Site Museum, Chengdu, China date: 2021-08-04 journal: Environ Sci Pollut Res Int DOI: 10.1007/s11356-021-15743-z sha: e3e4b5f4e446ca0d1eb20837da7e7d1bf9fedae2 doc_id: 786209 cord_uid: afesq2ka Air pollution is a serious threat to ancient sites and cultural relicts. In this study, we collected indoor and outdoor PM(2.5) samples and individual particles at the Exhibition Hall of Jinsha Site Museum in June 2020, and then the chemical components, sources, morphology, and mixing state of the fine particulate matter were analyzed. Our results show that the indoor and outdoor PM(2.5) concentrations at the Exhibition Hall were 33.3±6.6 and 39.4±11.4 μg m(−3), respectively. Although the indoor and outdoor concentrations of OC and EC were close, the proportion of secondary organic carbon in OC outdoor (33%) was higher than that indoor (27%). The PM(2.5) was alkaline both indoors and outdoors, and the outdoor alkalinity was stronger than the indoor alkalinity. SNA (SO(4)(2−), NO(3)(−), and NH(4)(+)) was the dominant component in the water-soluble inorganic ions; Na(+), Mg(2+), and Ca(2+) were well correlated (R(2)> 0.9), and Cl(−) and K(+) were also highly correlated (R(2)> 0.8). Enrichment factor analysis showed that Cu (indoor) and Cd were the main anthropogenic elements and that Cd was heavily enriched. Principal components analysis showed that the main sources of PM(2.5) at Jinsha Site Museum were motor vehicles, dust, secondary sources, and combustion sources. The individual particles were classified as organic matter, S-rich, soot, mineral, and fly ash/metal particles, and most of these particles were internally mixed with each other. At last, we proposed pollution control measures to improve the air quality of museums and the preservation of cultural relicts. Particulate matter (PM) in the atmosphere is of widespread concern as a result of its impact on the Earth's climate, the environment, and human health (Jan et al. 2017; Lee et al. 2017; Martins and da Graça 2018) . Meanwhile, the chemical species present in PM can also damage ancient buildings, cultural relicts, and archeological sites (Cao et al. 2005; Hu et al. 2015; Spezzano 2021) . High concentrations of PM can cause cultural relicts to peel, corrode, break, and twist and may cause damage to buildings (Lazaridis et al. 2018; Zorpas and Skouroupatis 2016) . There have been many studies on the sources of PM and the danger posed by its pollution to different types of museum. Hanapi and Din (2012) measured the concentrations of PM in several museums in Malaysia and found that the mass concentration of PM exceeded the indoor air quality limit and the standard for total suspended particles and PM 10 in Malaysia, threatening both human health and the country's cultural heritage. Kontozova Deutsch et al. (2008) found that the presence of tourists led to the accumulation of suspended PM inside some European churches and museums. Chianese et al. (2012) compared the mass concentrations of PM inside and outside the Museum of Capodimonte and found that dust and organic matter were transferred from the surrounding park into the museum by both the wind and the movement of tourists. Santis et al. (1992) measured the concentrations of indoor and outdoor air pollutants in the Uffizi Gallery in Florence and found that the indoor concentrations of HONO far exceeded the outdoor concentrations, which may be a result of a heterogeneous reaction between the walls and the exposed surfaces of the cultural relicts. According to previous studies, compared with PM 10 (particles with the aerodynamic diameter smaller than 10 μm), PM 2.5 (particles with the aerodynamic diameter smaller than 2.5 μm) is easier to enter display cases, deposit on objects, and thus soil the surface of cultural relicts (Wang et al. 2015; Janssen et al. 2013) . At the same time, the fact that PM 2.5 is more harmful to human health than PM 10 has been reported by many studies (Lyu et al. 2017; Li et al. 2017a ). In addition, most of the chemical components in PM are mainly distributed in PM 2.5 (Huang et al. 2016) . Therefore, PM 2.5 was usually taken as the key research target in many previous studies on the characteristics of air pollution in museums. For example, Zorpas and Skouroupatis (2016) found that the PM 2.5 mass concentrations in the Cypriot Archeological Museum and the Byzantine Museum in Cyprus were high both outdoors and indoors and that the presence of tourists increased the mass concentration of indoor PM 2.5 . Yang et al. (2009) showed that both indoor and outdoor PM 2.5 concentrations in Han Yangling Museum were mainly secondary ions, such as sulfate, nitrate, and ammonium. The monitoring conducted in Plantin-Moretus Museum, Belgium, found that sulfur-rich particles were frequently observed indoors during summer, while calcium-rich and calcium-and silicon-rich particles were dominating during winter months (Gysels et al. 2002) .The study on single particle analysis showed that the relative abundance of carbonrich particles inside the Royal Museum of Fine Arts, Belgium, was greater than outside (Krupińska et al. 2012) . These results are of great value in understanding and evaluating the impact of atmospheric PM on cultural relicts in museums and on human health. The Jinsha Site was announced as a National Key Cultural Relicts Protection Unit by the State Council of China in 2006, and Jinsha Site Museum is built on the original site. Unexplored cultural relicts-such as excavated and backfilled ivory, wild boar fangs, antlers, sunken wood, pottery, and jade-are all preserved at this site. The efficient preservation of these cultural relicts is important to studies of the ancient Shu civilization. However, Jinsha Site is located in Chengdu, one of the most polluted cities in China with an average annual PM 2.5 concentration of 43 μg m −3 in 2019. This PM 2.5 concentration exceeded the first-level standard (35 μg m −3 ) of the GB3095-2012 ambient air quality standard for China by >20% and was several times the World Health Organization guidelines (10 μg m −3 ) for PM 2.5 . Therefore, the impact of this high level of PM 2.5 pollution on the indoor air quality of Jinsha Site Exhibition Hall deserves attention because it affects both the preservation of relicts and the site and the health of visitors. In addition, the chemical composition of PM is complex, and different components have different effects on different cultural relicts and human health. However, most previous studies have focused on just one type of particle or one class of PM, and few studies have reported a comprehensive determination of the overall chemical composition of PM. In this study, we collected PM 2.5 and individual aerosol particles both indoor and outdoor of the Jinsha Site Exhibition Hall and analyzed the chemical components, sources, morphology, and mixing state of the particles. This information is important if we are to provide a better environment for the preservation of cultural relicts and a better visitor experience for tourists. An indoor observation site was set up at the ivory site of Pit No. 1 at Jinsha Site Exhibition Hall. The outdoor site was located in the square outside the east gate of the Exhibition Hall, about 100 m from Chengdu's middle ring road. Two TH-150C samplers (Wuhan Tianhong, China) were used to continuously collect indoor and outdoor PM 2.5 in June, 2020. The samplers used a Pall quartz fiber filter membrane (d = 90 mm) and a flow rate of 100 L min −1 . The sampling periods were 08:30-20:00 h and 20:30-08:00 h, respectively, for daytime and night-time sampling. Each sample was collected over a 11.5-h period. Four field blanks were also collected before and after the sampling period and analyzed at the same time as the PM 2.5 samples. After sampling, the quartz filters were placed in individual petri dishes and stored at −20°C before weighing and subsequent PM 2.5 chemical composition (including carbonaceous components, water-soluble inorganic ions, and trace elements) analysis. The air flow rate of the sampler was calibrated before the start of the collection period to ensure that the PM 2.5 sampler worked at the specified flow rate. Individual particles were collected on copper (Cu) transmission electron microscopy (TEM) grids coated with carbon film (carbon type-B, 300-mesh copper; Tianld Co., China) by a DKL-2 sampler (Genstar Electronic Technology, China). The sampler had a cascade impactor with 0.5 mm diameter jet nozzles at a flow rate of 1.0 L min −1 (Li et al. 2016 (Li et al. , 2020 . The sampling duration varied from 45 to 300 s depending on the particle loading estimated from the pollution levels. The copper grids were placed in sealed, dry plastic capsules and stored in a desiccator at 25°C and 20 ± 3% relative humidity for subsequent TEM analysis. Sample analysis and data processing PM 2.5 chemical and individual particle analysis The two carbonaceous components-namely, organic carbon (OC) and elemental carbon (EC)-were determined according to the EPA/NIOSH (TOT) method using a Sunset Labs thermal/optical carbon aerosol analyzer. A Dionex ICS-90 ion chromatography system was used to determine eight water-soluble inorganic ions (SO 4 2− , NO 3 − , NH 4 + , K + , Mg 2+ , Ca 2+ , Na + , and Cl − ). The concentrations of trace elements (Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, and Pb) were determined using an Agilent 7500a inductively coupled plasma mass spectrometer. More detailed information about the sample pretreatment, instrument optimization, and quality control methods are reported by Huang et al. (2021) . The individual particles were analyzed by TEM at an accelerating voltage of 200 kV using a JEOL JEM-2100 microscope coupled with an energy-dispersive X-ray spectrometer. Energy-dispersive X-ray spectrometry can detect elements with atomic weights heavier than C (such as C, O, Al, S, K, Ca, Fe, Si). The distribution of aerosol particles on the TEM grids was not uniform, with coarser particles occurring near the center and finer particles occurring on the periphery. Therefore, to make sure that the analyzed particles were representative of the entire size range, four areas were chosen from the center to the periphery of the sampling spot on each grid. A total of 950 and 1106 aerosol particles were collected indoors and outdoors, respectively. Secondary organic carbon (SOC) SOC is formed by the photochemical reactions of volatile hydrocarbons (Wang et al. 2019a ). The concentration of SOC can be obtained by: where OC is the concentration of OC (μg m −3 ), EC is the concentration of EC (μg m −3 ), and (OC/EC) min is the lowest observed OC/EC ratio (Han et al. 2015) . The EF method is an analytical technique proposed by Zoller et al. (1974) to express the degree of enrichment of an element in atmospheric particulates. The EF calculation can be used characterize the degree to which the concentration of an element is affected by human activity and therefore to determine whether the element is from a crustal, anthropogenic, or mixed source (Reimann and De Caritat 2000) . The formula is: where (Ci/C reference ) sample is the ratio of the trace element to the reference element in PM 2.5 and (Ci/C reference ) crust is the ratio of the trace element to the reference element in the Earth's crust (Nayebare et al. 2018 ). An EF < 10 is indicative of a significant crustal source with a negligible influence from anthropogenic source; if 10 < EF < 100, then this element is mainly from mixed source (crustal and anthropogenic source), whereas EF > 100 indicates that all of this element is derived from human activity-that is, it has an anthropogenic source (Chan et al. 1997; Sutherand 2000) . The average mass concentration of PM 2.5 was slightly higher outdoors than indoors during the whole study period, with average values of 39.4±11.4 and 33.3±6.6 μg m −3 , respectively (Fig. 1) . The outdoor sources of PM 2.5 are complex and include contributions from motor vehicles, biomass burning, coal combustion, cooking, road dust, industrial sources, and pollutants transported from the areas surrounding Chengdu (Li et al. 2017b; Tao et al. 2014 ). There is no obvious source of indoor PM 2.5 emissions, and therefore this PM 2.5 was mainly sourced from outside, although the semi-closed structure of the Exhibition Hall (especially during the closed period at night) reduced the transmission of pollutants to the interior. These results are similar to those found in previous studies of the five great civilization museums of the Yangtze River . The difference between the indoor and outdoor concentrations of PM 2.5 in our study was much lower than that reported by Li et al. (2014a) indoors. The difference in PM 2.5 mass concentrations between indoors and outdoors was significantly increased on days when the Exhibition Hall was closed, with differences of 17.0±5.1 μg m −3 when it was closed and 3.5±6.0 μg m −3 when it was open. This further illustrates the important role of air exchange between indoors and outdoors in the transmission of air pollution at Jinsha Site Exhibition Hall. The outdoor PM 2.5 mass concentration during the daytime (40.9±6.3 μg m −3 ) was slightly higher than that at night (38.0 ±14.8 μg m −3 ). By contrast, the indoor PM 2.5 mass concentrations during the daytime (33.7±5.7 μg m −3 ) and night-time (32.9±7.3 μg m −3 ) were similar. A comparative study found that when the museum was closed during the daytime, the average indoor PM 2.5 mass concentration was 29.8±3.0μg m −3 , which is lower than the average PM 2.5 mass concentration of 34.6±5.8 μg m −3 when the museum was open during the day and also lower than that at night (32.6±7.3 μg m −3 ). Human activity during the days when the museum was open may be an important reason for the increase in PM 2.5 mass concentrations. This difference in the PM 2.5 mass concentration between day and night was also seen at the Emperor Qin's Terra-cotta Museum ). It must been noted that our study was carried out during the coronavirus disease 2019 pandemic period, when the museum adopted a single-day flow limit of 1000 people. The number of visitors was therefore significantly less than before the pandemic, and the impact of human activities on the indoor air quality was greatly reduced. Chemical composition of PM 2.5 The OC in the atmosphere can be divided into primary OC emitted directly by primary emission sources (including natural and anthropogenic sources) and SOC formed through oxidation of reactive organic gases followed by gas-to-particle conversion processes in the atmosphere (Bozzetti et al. 2016; Huang et al. 2014; Gelencsér 2004 ). The EC is mainly derived from the incomplete burning of fossil fuels and biomass (Luo et al. 2021) . The difference between the indoor and outdoor concentrations of OC was 0.6±2.4 μg m −3 throughout the observation period, whereas the difference in EC was 0.1 ±0.4 μg m −3 (Fig. 2) . The concentrations of carbonaceous components were similar in the two environments as a result of the frequent air exchange between indoors and outdoors. The OC/EC ratio is generally considered to be an important indicator of the source of PM 2.5 . SOC is considered to be present when the OC/EC ratio is >2 (Chatterjee et al. 2021 ). In our study, the outdoor and indoor OC/EC ratios at the Exhibition Hall were 5.9 and 5.7, respectively, clearly indicating the presence of SOC. Meanwhile, the proportion of outdoor SOC in OC (33%) was higher than that of indoor (27%). In addition, the indoor concentrations of OC, EC, and SOC were similar during the night (7.7±1.2, 1.5±0.3, and 1.6 ±0.8 μg m −3 , respectively) and during the day (7.3±0.7, 1.2 ±0.2, and 1.5±0.9 μg m −3 , respectively). The outdoor concentrations of EC were similar during the day and night (1.4±0.5 vs. 1.3±0.3 μg m −3 ), whereas OC was lower during the night (7.1±1.7 μg m −3 ) than during the day (9.2±2.7 μg m −3 ). Water-soluble inorganic ions (WSIIs) are important components of PM 2.5 and can contribute to haze pollution (Wu et al. 2018) . The indoor and outdoor average mass concentrations of WSIIs were 13.2±5.5 and 13.2±6.0 μg m −3 , accounting for 39.3 and 33.5%, respectively, of the total PM 2.5 . Among the WSIIs, SO 4 2− , NO 3 − , and NH 4 + (SNA) were the dominant ion components, accounting for 69.9 and 59.2% of the total indoor and outdoor WSIIs, respectively (Fig. 3) . The SNA components were mainly derived from the secondary conversion of their gaseous precursors (e.g., SO 2 , NO x , and NH 3 ) (Xie et al. 2020) . The concentrations of SO 4 2− , NO 3 − , and NH 4 + were as follows: indoor, 5.3±2.4, 0.7±0.7, and 3.2±2.4 μg m −3 , respectively, and outdoor, 4.5±2.1, 0.6±0.5, and 2.8 ±1.7 μg m −3 , respectively. Ca 2+ is a typical tracer of soil and construction dust , and its indoor concentration (1.3±0.7μg m −3 ) was lower than the outdoor concentration (2.3±2.1 μg m −3 ). This is because the outdoor sampling site was located in the center of a square with a much higher contribution from soil dust. In addition, the indoor (0. PM 2.5 acidity We used the ratio of the anion and cation equivalents to calculate the acidity of the indoor and outdoor PM 2.5 (Cheng and Zhang 2017): where AE represents the anion equivalent in the sample and CE represents the cation equivalent in the sample. The calculation shows that the indoor and outdoor ratios of AE/CE were 0.53 and 0.38, respectively, indicating that both the indoor and outdoor PM 2.5 were alkaline. The outdoor PM 2.5 was more alkaline than the indoor PM 2.5 , consistent with the higher alkaline ions concentrations in the observations and the differences between the indoor and outdoor concentrations. These results are also consistent with those at the Qianhu Campus of Nanchang University (Huang et al. 2012) . Previous studies have shown that both alkaline or acidic particles could cause serious damage to cultural relicts and affect their color Mašková et al. 2017) . Moreover, these particles could cause serious harm to human skin and respiratory system (Nowatzki 2008) . The existing forms of SNA The main component of WSIIs is SNA, and the existing form of SNA is important in the analyses of the formation of PM 2.5 pollution. Previous studies have shown that NH 4 + usually preferentially combines with SO 4 2− to form (NH 4 ) 2 SO 4 or NH 4 HSO 4 , and then the remaining NH 4 + will combine with NO 3 − to form NH 4 NO 3 Wang et al. 2019b ). The regression equations for NH 4 + and SO 4 2− at the indoor and outdoor monitoring points were y = 3.5641x − 0.0201 and y = 3.2919x + 0.002, respectively. The slopes were both >2, indicating that the SO 4 2− in both the indoor and outdoor atmosphere combined with NH 4 + to generate (NH 4 ) 2 SO 4 , and there was some excess NH 4 + remaining. The further linear fitting of the indoor and outdoor NH 4 + and NO 3 − + 2SO 4 2− concentrations showed that the slopes of the indoor and outdoor regression equations were both >1 (1.8 and 1.6, respectively), indicating that the NH 4 + combined with SO 4 2− and NO 3 − and there was some excess NH 4 + remaining. Both the indoor and outdoor NH 4 + mainly existed as (NH 4 ) 2 SO 4 and NH 4 NO 3 , and the excess NH 4 + was available to combine with other anions (such as Cl − ). Ion correlation The Pearson correlation analysis was carried out on the WSIIs in the indoor and outdoor PM 2.5 , and the results were very similar. We therefore use the results for the outdoor PM 2.5 in further discussions. Table 1 shows that the correlation coefficients (R 2 ) between the SNA components were >0.5, consistent with their similar mechanisms of formation (secondary reactions). The correlation coefficients (R 2 ) between Na + , Mg 2+ , and Ca 2+ were all >0.9, indicating that these three ions have a high homology, closely related to their sources in soil and construction dust Liu et al. 2017; Yu et al. 2020) . Cl − and K + also showed a strong correlation (R 2 > 0.8), which may be related to contributions from combustion sources, such as coal combustion and biomass burning. The total outdoor concentration of trace elements was slightly higher than the indoor concentration throughout the study period, with average values of 4.0±1.7 and 2.7±0.5 μg m −3 , respectively. The total contribution of Al and Fe accounted for 85.9 and 86.8% of the outdoor and indoor trace elements, respectively (Fig. 4) . We used Al as a reference element to calculate the EF of trace elements in PM 2.5 (Table 2) . Apart from Cu, which had a mixed source outdoors and an anthropogenic source indoors, there was no difference in the degree of enrichment of other trace elements, and they had the same level of enrichment both indoors and outdoors. Al, V, Mn, Fe, and Co had a crustal source; Cr, Ni, Cu (outdoor), Zn, As, and Pb had a mixed source; and Cu (indoor) and Cd had an anthropogenic source. The EF value of Cd both indoors and outdoors was >100, and almost all the Cd was from human activity. PCA was performed with the chemical components quantified in the PM 2.5 filters to identify the main sources of PM 2.5 at the Jinsha Site. We used the outdoor observations for source analysis because there is no unique indoor emission source in the Jinsha Site Exhibition Hall, and the indoor PM 2.5 is mainly from the transmission of outdoor air pollutants. Table 3 shows that the cumulative contribution rate of the four principal components reached 82.1%, and we therefore assume that these components represent the main sources of PM 2.5 . In factor 1, the OC, EC, Al, Mn, Fe, Ni, Cu, Zn, As, Cd, and Pb had higher loading values, and the variance explanation ratio reached 36.4%. The OC mainly comes from combustion sources such as fossil fuels (Cao et al. 2006 ). The EC mainly comes from tailpipe exhaust fumes and is attributed to poor vehicle maintenance (Song et al. 2006) . Zn, Cu, and Pb come from the mechanical wear of motor vehicles, gasoline combustion, and tire wear (Hou et al. 2019) , whereas Ni is characteristic of fuel combustion (Fan et al. 2021) . Factor 1 can therefore be comprehensively identified as sourced from motor vehicles. The loading values of Ca 2+ , Mg 2+ , Na + , V, Cr, and Co were higher in factor 2, and the variance explanation ratio was 22.1%. Ca 2+ generally comes from soil dust or building construction. Mg 2+ mainly comes from soil (Cao et al. 2006) . Na + can come from dust or industrial smelting, such as steelmaking (Han et al. 2007; Silva et al. 2000) . V may be derived from soil, wind, or sand (López et al. 2011) . Cr may be derived from cement production dust or the metallurgical industry (Li et al. 2021) . Co is characteristic of the metallurgical chemical industry (Hsu et al. 2021) . V, Cr, and Co may originate from the formation of industrial dust, indicating that the dust sources are mixed with soil, sand, construction, and industrial dust. Liang et al. (2018) reached a similar conclusion in the analysis of PM 2.5 fugitive dust sources in Guiyang. Factor 2 can therefore be identified as a source of dust. Factor 3 was dominated by SNA components, and the variance explanation ratio was 14.4%. The main source of SNA is the secondary conversion of gaseous pollutants (SO 2 , NO x , and NH 3 ) . This is consistent with the results of Huang et al. (2021) that secondary sources are related to SNA. Factor 3 can therefore be identified as a secondary source. The characteristic elements in factor 4 were K + and Cl − , and the variance explanation ratio was 9.3%. K + and Cl − are indicators of biomass combustion and coal combustion, respectively . Therefore this factor can be identified as a combustion source. Boman et al. (2004) analyzed PM from the residential combustion of pelletized biomass fuels and found that KCl was the dominant inorganic phase, consistent with our results. In our study, all the individual particles measured by TEM were classified as five major aerosol components based on their morphology and elemental composition (Li and Shao 2009) : organic matter (OM); S-rich, soot, mineral, and fly ash/metal particles (Fig. 5) . The morphology of the OM particles was stable under irradiation from the TEM electron beam. The OM particles were mainly composed of C and O, and their morphology was either regular spherical and irregular. In addition, there were semi-dome-like OM particles, mainly in the form of organic coatings. The S-rich particles were more sensitive to the TEM electron beam and were prone to sublimation. Therefore the S-rich particles had a foam-like structure, and the main elements were C, O and S. Soot particles, derived from the incomplete combustion of fuels and other sources, were composed of C and O, mainly chains or clusters of carbon spheres. The mineral particles were regular rectangular or angular irregular in shape. Because they mainly come from construction and ground dust, the particles were mainly composed of C, O, S, and Ca and also contained small amounts of crustal elements such as Fe and Al. The fly ash/ metal particles had a very small particle size and smooth surfaces and mainly came from industrial activities. The main elements were C, O, and Si and metals such as Fe and Zn. Pósfai and Buseck (2010) described the mixing state of an aerosol particle including externally mixed (separated in the air) and internally mixed (an aggregate of different phases). Through the analysis of the mixing state of particles, the sources and formation mechanism of them can be analyzed (Li et al. 2014b) . In this study, most of the particles existed in the form of internal mixing and presented a variety of mixed forms (Fig. 6) . According to the mixing state of particles, we can infer their sources and formation mechanism in the atmosphere. For example, the pre-existing OM particles in the atmosphere can provide a reaction interface for the condensation of gaseous precursors, such as SO 2 , and heterogeneous reactions, which favors the formation of OM-S particles (Fig. 6a, b) . Mineral particles are rich in alkaline substances, and their surface is an important interface for secondary reactions of acidic gaseous pollutants (SO 2 , NO x ) to form mixed particles of mineral dust and sulfate (Fig. 6i) . Although the contribution of metal particles in PM 2.5 was low, it has been the focus of previous studies. This is because metals present a serious threat to human health and involved in the formation of some PM 2.5 species, such as OM and sulfate. Fig. 6 c, d, e, and g show that the fly ash/metal particles were widely mixed with other types of particle. In order to investigate the characteristics of atmospheric particulate pollution in Jinsha Site Museum, we collected indoor and outdoor PM 2.5 samples and individual particles at the Exhibition Hall of Jinsha Site Museum in June 2020, and then the chemical components, sources, morphology, and mixing state of the fine PM were analyzed. The results show that the indoor and outdoor PM 2.5 mass concentrations at Jinsha Site Exhibition Hall were 33.3±6.6 and 39.4±11.4 μg m −3 , respectively. The opening and closing of the museum had an important impact on indoor and outdoor PM 2.5 concentration levels. The indoor and outdoor OC/EC ratios were both >2, and their PM 2.5 were both alkaline. SO 4 2− , NO 3 − , and NH 4 + (SNA) were the dominant ion components, accounting for 69.9 and 59.2% of the total indoor and outdoor WSIIs, respectively. The main sources of PM 2.5 at Jinsha Site Museum were motor vehicles, dust, secondary sources, and combustion sources. All individual particles were classified as OM, S-rich, soot, mineral, and fly ash/metal particles. Most of these particles were internally mixed with each other, which is crucial in analyzing the sources and mechanism of formation of particles in the atmosphere. In order to improve the air quality of Jinsha Site Museum and provide better preservation and sightseeing environment for cultural relicts and tourists, we put forward the following suggestions for improving the air quality based on the results of this study. Firstly, to reduce the outdoor pollution sources, the dust on the bare ground around the Exhibition Hall should be reduced by spraying with water, and the area of greening around the Exhibition Hall could be further improved by planting taller trees to block the transfer of pollutants from the surrounding areas. Secondly, to reduce indoor pollution, the air tightness of the Exhibition Hall should be improved and the air exchange between indoors and outdoors reduced by a curtain system at the entrance and exit. Air purification equipment should be installed to remove the existing indoor pollutants. Green building materials should be used for secondary decoration to reduce potential sources of indoor pollutants. Availability of data and materials The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request. 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regional transport pollution in a megacity of southwest China: source apportionment and implication Characterizing particulate pollutants in an enclosed museum in Shanghai Chemical characteristics, sources, and formation mechanisms of PM 2.5 before and during the Spring Festival in a coastal city in Southeast China Characteristics of PM 2.5 and SNA components and meteorological factors impact on air pollution through 2013-2017 in Beijing Characteristics and formation mechanisms of autumn haze pollution in Chengdu based on high time-resolved water-soluble ion analysis Characterization and source analysis of water-soluble ions in PM 2.5 at a background site in Central China Physicochemical characteristics of soil, atmosphere, and weathered crust in the underground museum of the Hanyang Mausoleum Chemical characteristics of road dust PM 2.5 fraction in oasis cities at the margin of Tarim Basin Atmospheric concentrations and sources of trace metals at the South Pole Indoor air quality evaluation of two museums in a subtropical climate conditions Publisher's note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations Ethics approval and consent to participate Not applicable Competing interests The authors declare no competing interests.