Source apportionment of trace elements in urban atmospheric particulates using tree bark biomonitoring with receptor...

To investigate the characteristics and sources of elemental pollution in atmospheric particulate matter (PM) in Hangzhou City, bark samples of Cinnamomum camphora (n = 172) were collected as a biomonitoring medium. Concentrations of 28 elements were determined using inductively coupled plasma mass spectrometry (ICP-MS). Enrichment factors (EF) and geospatial analysis were applied to assess elemental enrichment and spatial patterns, while absolute principal component scores-multiple linear regression (APCS-MLR) and positive matrix factorization (PMF) were employed for quantitative source apportionment. Results showed that, except for Na, which primarily originated from natural sources, all elements were influenced by anthropogenic activities, with Ca and Cd exhibiting high enrichment, indicating significant anthropogenic impact. Cross-regional comparisons revealed that bark elemental concentrations in the study area were intermediate between those of heavily industrialized cities and low-pollution regions, confirming the element enrichment characteristics in bark serves as a reliable indicator of regional pollution conditions. APCS-MLR identified six major sources: mixed natural-combustion sources (44.4 %), traffic emissions (17.8 %), mixed industrial activities (10.4 %), natural source (11.4 %), metallurgical dust (8.4 %), and construction dust (7.7 %). PMF yielded broadly consistent results but separated the mixed natural-combustion source into distinct sources: natural source (20.4 %), construction dust (18.8 %), mixed industrial activities (4.9 %), metallurgical dust (24.4 %), traffic emissions (14.3 %), and combustion sources (17.3 %). The agreement between models demonstrates the robustness of combining receptor models for quantitative source identification. By integrating single-species bark biomonitoring with multi-receptor modeling, this study achieved high spatial resolution source apportionment of PM elements, providing a scientific basis for enhancing urban monitoring networks and formulating targeted pollution control strategies.