One century of change: Monitoring heavy metal pollution through herbarium bryophytes in Bratislava (Slovakia)

This study provides the first historical reconstruction of metal and metalloid deposition in Slovakia using bryophyte herbarium specimens. By integrating archival and contemporary data, we established a dataset for Bratislava spanning 1912-2023, enabling evaluation of temporal and spatial pollution trends, emission sources, and comparisons with European patterns. The investigation covers three major periods (1900-1945, 1946-1989, 1990-2023), reflecting key stages in industrial and transportation development. Concentrations of 22 elements, measured by inductively coupled plasma-mass spectrometry (ICP-MS), revealed distinct temporal trends. Metal and metalloid levels were generally low before 1945, followed by increases in As, Cd, Bi, and Pb during World War II and peak accumulation during the industrialization of 1946-1989. A marked decline in Pb, Cd, As, Tl, and Ba after 1990 indicates industrial downturn and the effectiveness of environmental regulations, consistent with European trends. In contrast, recent samples showed elevated Cr, Ni, Mo, and Cu, linked to traffic and ongoing industrial emissions. Statistical analyses identified six groups of elements associated with distinct anthropogenic sources. Spatial patterns indicated that the highest concentrations occurred near historical and current point sources, with proximity to emissions and prevailing wind direction significantly influencing distributions. The use of herbarium specimens allowed reconstruction of the long-term environmental impacts of industrialization and urbanization in a Central European capital. The results establish a historical baseline for assessing ecosystem recovery and provide valuable data to support future environmental management and public health policies.