Assessment of traffic-related metal pollution in Cluj-Napoca using moss bag biomonitoring

Traffic-related emissions are among the main contributors to urban air pollution, leading to the accumulation of potentially toxic elements in airborne particulate matter. Biomonitoring using moss bags emerged as a cost-effective and reliable method for assessing atmospheric metal deposition at high spatial resolution in cities. This study evaluated the accumulation of potentially toxic elements in moss bags exposed in different areas of Cluj-Napoca, Romania. Moss bags were exposed in two locations in areas with intense traffic and two locations in residential areas with low to moderate traffic. After 10 weeks of exposure, concentrations of several metals were determined and compared with those measured in unexposed moss samples, and enrichment factors were calculated to identify the dominant sources of pollution. The results showed that potentially toxic element concentrations increased in all exposed moss samples compared with the unexposed control, with Cu and Zn showing the most pronounced increases. The highest concentrations of potentially toxic elements were detected in areas with intense traffic, whereas the lowest concentrations were observed in residential areas with reduced traffic. Enrichment factor analysis indicated strong enrichment for Cu, moderate enrichment for Zn, Cd, and Ni, and no enrichment for Pb and Cr. These findings suggest that non-exhaust traffic emissions associated with vehicle wear (particularly Cu and Zn) contribute more substantially to urban air pollution than exhaust emissions. This study confirms the effectiveness of moss bags as a reliable and scalable biomonitoring tool for assessing urban air pollution and identifying spatial differences in metal deposition. Traffic intensity strongly influenced metal accumulation patterns in Cluj-Napoca, highlighting the growing importance of non-exhaust emissions as a major source of urban atmospheric contamination.

Acknowledgement: This research was carried out through the Core Program within the National Research Development and Innovation Plan 2022–2027, with the support of MCID, project PN no. 23 05.