Source analysis of heavy metal elements of PM2.5 in canteen in a university in winter

Indoor air particulate samples were collected in the first floor of the Xingyuan canteen of Nanjing University of Science and Technology (NJUST) in Nanjing during the winter season. Meanwhile, outdoor air particulate samples were collected on the roof of a building that is 28 m away from the canteen. The mean PM2.5 (fine particulate matter) concentrations of the indoor and outdoor samples were found to be 99.43 and 103.09 mu g/m(3), respectively. Through correlation analysis, it was found that more than half of the PM2.5 penetrates from the adjacent outdoor area into the canteen. Inductively coupled plasma optical emission spectrometry (ICP-OES) was used to determine the concentration of heavy metals (As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn) in the PM2.5, revealing that the concentration of As, Mn and Cd in the canteen exceeded health standards. Positive Matrix Factorization (PMF) was used to identify the pollution sources of the PM2.5-related heavy metals in the canteen, revealing the following sources in descending order: cooking (34.7%), fuel combustion (28.9%), canteen kitchenware (14.4%), transportation (9.6%), indoor building materials (8%) and the Earth's crust (4.4%). Enrichment factor analysis revealed the source of the excessive As in the canteen to be the outdoor air and the cooking of a large amount of meat in the canteen. The outdoor air contained excessive As and infiltrated the canteen. In addition, the Earth's crust was found to be the source of excessive Mn in the canteen, while transportation was the cause of excessive Cd.

Automated summary

Indoor and outdoor air particulate samples were collected in a canteen at NJUST, with findings showing over half of PM2.5 penetrating from outdoors. Analysis revealed elevated levels of As, Mn, and Cd in the canteen, originating from sources like cooking, fuel combustion, and transportation. Enrichment factor analysis linked excessive As in the canteen to outdoor air infiltration and cooking practices.