Characteristics of fine particulate matter (PM_2.5) at Jinsha Site Museum, Chengdu, China

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 (SO₄^2-, NO₃^-, and NH₄⁺) was the dominant component in the water-soluble inorganic ions; Na⁺, Mg²⁺, and Ca²⁺ were well correlated (R²> 0.9), and Cl^- and K⁺ were also highly correlated (R²> 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.