Metal Uptake in Moss Under Controlled Conditions and Spatial Visualization of Atmospheric Deposition in Sweden : Laboratory Exposure of As, Cu, Zn, and Pb in Sphagnum girgensohnii, Pleurozium schreberi, and Ptilium crista-castrensi

Sammanfattning

Atmospheric deposition of heavy metals presents a significant threat to both ecosystems and human health, largely due to limited control over long-range atmospheric transport and emissions from local industrial sources. Moss has been widely proven to effectively accumulate atmospheric deposition, as moss absorbs airborne pollution directly across its surface without the influence of root uptake, therefore acting as an effective biomonitor. This study provides a short-term accumulation capacity of three moss species Sphagnum girgensohnii, Pleurozium schreberi, and Ptilium crista-castrensis under controlled laboratory conditions analyzing arsenic (As), copper (Cu), zinc (Zn), and lead (Pb). The laboratory experiment was conducted over 30 days, in which mosses were exposed to low and high metal solution every 48 hours, while control samples were exposed to MilliQ water. Metals were applied individually with pipettes in the form of solutions of sodium arsenite (NaAsO2), copper sulfate, (CuSO4), zinc sulfate (ZnSO4), and lead (II) nitrate (Pb(NO3)2). After the exposure period, the samples were analyzed using inductively coupled plasma mass spectrometry (ICP-SFMS), and uptake efficiency was evaluated relative to control samples. In parallel with the laboratory experiment, national monitoring data from IVL Swedish Environmental Research Institute were analyzed to assess long-term trends and spatial distribution of metal accumulation in moss across Sweden between 2010 and 2020. Spatial patterns were analyzed using interpolation methods in QGIS-LTR, to identify potential contamination sources and regional hotspots. Atmospheric deposition data from the Swedish Meteorological and Hydrological Institute (SMHI) were also included to compare the possible correlation between metals in moss, precipitation, and air. The results showed a clear difference in relative metal uptake among the metals analyzed. The general sorption pattern was As > Cu > Pb > Zn. Arsenic indicated the highest uptake among the metals analyzed, with an uptake up to 6270% compared to controls. This indicates that As(III) has high mobility, bioavailability, and slower excretion rate. Pb and Cu showed considerable uptake aligning with the previous studies showing sorption capacities. Zn was observed to have the lowest sorption efficiency, possibly due to physiological regulation limiting the accumulation of metals. The highest accumulation efficiency was observed for Sphagnum girgensohnii, for As, Zn, and Pb. Pleurozium schreberi showed notable uptake of Cu which aligns with previous studies. The spatial analysis of interpolated maps showed that Pb has had a significant decrease over the last decades, reflecting the regulation of emissions and use of Pb in products. In contrast As, Cu, and Zn showed persistent hotspots, particularly in regions near mines, landfills, and shooting ranges. Pb indicated the strongest correlation between metals in moss and atmospheric deposition, especially for wet deposition. In contrast, As increased in moss samples despite a decrease in both wet and dry deposition, indicating local sources dominating the spread of the metal. Weaker relationships were observed for Cu and Zn and could be influenced by biological uptake mechanisms and bioavailability. The study demonstrates that mosses can effectively accumulate metals under a short period under controlled conditions with metal speciation influencing the accumulation pattern. Spatial analysis across Sweden confirms that moss is an effective biomonitor for atmospheric deposition and responds well to regulatory changes. These overall findings support that moss is a reliable biomonitor for air quality and pollution assessments.