Mosses (Bryophyta) are well-established biomonitors of atmospheric deposition. The determination of more than 120 organic contaminants in moss surveys from 2015 to 2020 in Germany revealed their widespread atmospheric distribution, particularly with regard to polycyclic aromatic hydrocarbons (PAH), polychlorinated dibenzodioxins/furans (PCDD/F), and certain halogenated flame retardants. The absence of perfluoroalkyl substances (PFAS) and polybrominated biphenyls (PBB) indicated very low deposition levels and/or limited suitability of moss as bioindicator for these compounds. Pollutant concentrations were generally lower at background or rural sites and partly higher in urban regions and conurbations. For some pollutants (e.g., several flame retardants), a west-east concentration gradient was observed with the highest values in the west of Germany, whereas other contaminants were homogeneously distributed. The comparisons of the results from the 2015 and 2020 surveys showed overall significantly decreasing concentrations for certain PCDD/F and hexabromocyclododecane (HBCD) (up to -78 %). Significantly increasing concentrations were found for pentabromotoluene (PBT; +235 %). These results demonstrate that temporal trend investigations should be continuously performed, not be limited to legacy compounds, and extended to a broader spectrum of pollutants of emerging environmental concern.

Persistent organic pollutants (POPs) are globally distributed toxic contaminants. Since 1990, mosses have been used in the UNECE European Moss Survey as cost-effective biomonitors of atmospheric deposition. This study provides the first predictive maps of POP concentrations in mosses, revealing nationwide contamination patterns across Germany. As a case study within the Moss Survey, predictive models were built from POP concentrations measured at 21 sites in 2020 and combined with environmental and land-use data. Random Forest analyses explained more than 20% of the variance for seven of eleven POP groups, yielding robust spatial estimates, particularly for PAH, BDE 209, and DBDPE, despite moderate systematic differences. Explanatory power was limited for PCDD/F, PCDD/F TEQ values, DPTE, and HBBz, while HBCD, PBDE, DP, and PBT showed a moderate performance. A comparison with geostatistical reference maps indicated moderate to good concordance, though regional uncertainties persisted. Industrialized regions such as North Rhine-Westphalia, Rhine Neckar, Halle/Leipzig, and Saarland emerged as consistent hotspots, whereas rural and forested areas showed lower contamination. The findings highlight the value of moss surveys for spatial POP assessment and underscore the need for additional predictors, especially atmospheric deposition, and for integrating Random Forest models with geostatistical approaches such as regression kriging to enhance predictive accuracy.

Mosses (Bryophyta) are well-established biomonitors of atmospheric deposition, including persistent organic pollutants (POPs) and microplastics (MPs). Using German Moss Survey 2020 data, this study identified factors influencing POPs and MPs in mosses through correlation and random forest analyses. For 10 of 11 POP groups, the models explained a variance of more than 20%. Key predictors included atmospheric deposition and the density of urban-industrial and agricultural land uses within 100-300 km. Population density and the density of extraction and dump sites within radii of <5 km (PCDD/Fs, PCDD/F TEQ values, HBCD, 23 PBDEs, BDE-209, DBDPE, PBT, and HBBz), as well as distances to residential areas and transport infrastructure (PCDD/Fs, HBCD, PBDEs, DP, and DBDPE), also proved to be highly relevant, although a direct causal relationship seems unlikely for flame retardants. These findings indicate that POP concentrations in mosses are influenced not only by large-scale atmospheric deposition but also by local emission sources near sampling sites. Vegetation parameters, particularly the leaf area index, showed additional effects. For MP, only two polymer groups (SBR and PE) yielded models with sufficient predictive strength, again dominated by proximity to local sources. Minimum sample size analysis demonstrated that a denser sampling network is required to achieve a 20% tolerance error in future monitoring campaigns.

The 2020 moss survey in Germany was designed as a pilot study and aimed to 1. validate the analysis of various organic contaminants developed in the previous moss survey; 2. develop the microplastic analysis methodology; 3. analyse the spatial distribution of persistent organic pollutants as well as polycyclic aromatic hydrocarbons in moss samples collected in Germany in 2020; and 4. compare the spatial deposition patterns with the results of current atmospheric deposition models. This article describes the latter objective The collection of mosses at 21 sites within Germany and the chemical analysis of organic pollutants was carried out according to ICP Vegetation (Heavy metals, nitrogen and POPs in European mosses. Monitoring manual survey 2020. Bangor (United Kingdom) and Dubna (Russian Federation), 2020). Geostatistical methods were used to analyse the spatial structure of the discrete measurement data and to produce maps based on this. The mapped concentrations in the mosses were compared with the modelled total annual deposition. The spatial distribution of the substances often shows a concentration gradient with higher values in densely populated and industrialised areas in western Germany and lower concentrations in eastern areas. A triangle with comparatively higher values in central Germany is recognisable. No correlations were found between the concentration of benzo[a]pyrene (B[a]P) in the mosses and the modelled B[a]P deposition. However, the direct comparison at the moss sampling sites shows better agreement between the measured and modelled data in the north-western half of Germany than in the other regions. Medium correlations were found between the concentrations of polychlorinated dibenzo-p-dioxins and furans (PCDD/F) in the mosses and the modelled PCDD/F deposition, and strong and very strong correlations were found with the geostatistical surface estimates. The most obvious similarities in the spatial patterns of the measured PCDD/F and modelled data were found in southern Bavaria, in a strip from North Rhine-Westphalia via northern Hesse to Thuringia and in the triangle between Mecklenburg-Western Pomerania, northern Brandenburg and eastern Lower Saxony. The study made it possible to describe the spatial distribution of persistent organic substances and polycyclic aromatic hydrocarbons in Germany and, at least in the case of PCDD/F, produced a good agreement between the modelled deposition and the measured concentrations in mosses. The moss data should be analysed in greater depth and statistically validated.

Background The accumulation of trace elements in mosses is used as an indirect measure of atmospheric deposition and an important complement to the techniques used to monitor the Geneva Air Pollution Convention. The aim of this paper is to quantify and map temporal and spatial trends of metal enrichment in mosses collected in Germany in 1990, 1995, 2000, 2005, 2015 and 2020. Collection and chemical analysis of the moss samples were carried out according to international guidelines. Results The analysis shows that since 1990, the median concentrations of As, Cd, Cu, Ni, Pb and Sb in the mosses have been decreasing significantly, with the with the highest decline of Pb (− 86%). This trend reversed in 2000 and 2005 and between 2015 and 2020 by increases in the concentrations of some trace elements. In the 2000 Moss Survey, higher concentrations were measured for Cd, Cu, Ni and Sb than in 2015, ranging from + 26% (Cu) to + 165% (Ni). For As and Pb, no significant changes can be observed in 2020 compared to 2015. The increase in metal concentrations in the mosses over the last five years does not correspond to the corresponding trends in reported metal emissions in Germany (2015–2020). In contrast, the long-term trends of the As, Cd, Cu, Ni and Pb concentrations measured in the mosses showed good overall correspondence with the emission trends in Germany (1990–2020). The long-term trends of the moss data are mostly weaker than those of the emission data. The spatial patterns of the temporal trends were mapped and discussed for As, Cd, Cu, Ni, Pb and Sb. Conclusions The study shows that for valid monitoring of atmospheric deposition, it is not enough to consider only emission data or the modelled deposition derived from these data. In this respect, the study provides one of many necessary contributions to the discussion on the extent to which analytes of current monitoring programmes are still relevant and up-to-date and whether there are new substances that are also relevant or even more relevant than existing analytes and to what extent this should be taken into account in designing future environmental monitoring.

Background Standardized methods for sampling and detection of atmospherically deposited microplastics are lacking. Contrary to that, the use of moss as a biomonitoring system was established concerning other atmospheric pollutants, such as heavy metals and persistent organic pollutants. Only a few research groups actually focus on detecting atmospherically deposited microplastics in moss. In general, the determination of microplastics in environmental samples is commonly performed using a particle-based or mass-based analytical approach. However, a dearth of mass-based investigations is noticeable, especially for atmospherically deposited microplastics. Given this background, this study shows the determination of atmospherically deposited microplastics in moss utilizing thermal extraction desorption gas chromatography-mass spectrometry (TED-GC-MS) and Raman microspectroscopy (µRaman) to acquire both information. The moss samples analyzed were collected as part of the German moss survey 2020/2021, supported by the German Environment Agency. Three distinct sampling sites were investigated, which could be categorized based on their distances from potential emission sources. Results Concerning µRaman analysis, most microplastic particles could be determined within a 10 to 100 µm size range. Further, most microplastic aspect ratios were determined in a range of 0.25 to 1.00, indicating a fragmental shape. Additionally, a correlation between the number of microplastic particles determined and the distance of the potential emission source was observable. It was determined to be 688, 474, and 248 particles per sampling site with a distance of 150 m, 225 m, and 360 m. Both analytical approaches (TED-GC-MS & µRaman) concurred in identifying the polymer types (polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET)) in the moss samples. Concerning TED-GC-MS, 7 to 111 µg/g could be determined, depending on the polymer types and distance to the potential emission source. Conclusion µRaman and TED-GC-MS investigations demonstrated correlations between microplastic particle numbers, size, types, and mass concentrations with the distance of the potential emission source. The investigation corroborates the mutual complementarity of both analytical approaches, enabling more comprehensive information on samples.

PCDD/Fs (17 congeners and Σ tetra -to octachloro homologues) and 209 PCBs were investigated in monthly samples of ambient air (gas + particle phase) and atmospheric deposition at two background monitoring sites in Germany in 2018/19. In atmospheric deposition samples, PCDD/F congeners as well as certain PCBs were frequently below the method quantification limits whereas values for PCDD/F homologue groups could be quantified more often. Annual deposition averages for individual PCDD/Fs were between <0.1 μg/m2d and 6.7 μg/m2d. Averages for Σ TeCDD/F to OCDD/F homologue totals in deposition were about 11 pg/m2d and 19 pg/m2d. Total PCB deposition rates were about 1900 pg/m2d and 1550 pg/m2d. PCDD/F + PCB-deposition rates were below 1 pg WHO2005-TEQ/m2d on average. In ambient air, both substance groups were frequently observed. Annual concentration averages for individual PCDD/F were between 0.1 fg/m³ and 50 fg/m³. Average values for Σ TeCDD/F to OCDD/F homologue totals in ambient air were 283 fg/m³ and 162 fg/m³. Total PCB concentrations were about 50 pg/m³ at both sites. PCDD/F + PCB-TEQ values were lower than 5 fg WHO2005-TEQ/m³ on average. Besides the frequently studied dioxin-like PCBs and six indicator PCBs, the analysis of the 209 PCBs (166 separated PCB-peaks) enabled the identification and evaluation of additional PCBs that might be of environmental concern. Of 166 PCBs or PCB-coelutions, up to 144 were quantified in air samples and up to 94 in atmospheric deposition samples. In ambient air, some of these PCBs were observed at levels similar to or exceeding those of the six indicator PCBs. Important additional PCBs in ambient air were PCB 5 + 8, PCB 11, PCB 17, PCB 18, PCB 20 + 33, PCB 31, PCB 43 + 49, PCB 44, PCB 47 + 48 + 65 + 75, PCB 93 + 95 + 98 + 102, PCB 139 + 149, and PCB 151. The presence of these PCBs in atmospheric samples implies that by analysing only selected PCBs potentially important contaminants are overlooked.

Mosses are particularly suitable for recording the accumulation of atmospheric substance inputs in large areas at relatively many locations. In Europe, this has been done every five years since 1990 as part of the European Moss Survey. In this framework, mosses were collected at up to 7312 sites in up to 34 countries and chemically analyzed for metals (since 1990), nitrogen (since 2005), persistent organic pollutants (since 2010) and microplastic (since 2015). The present investigation aimed at determining the nitrogen accumulated in three-year-old shoots from mosses collected in Germany in 2020 by quality-controlled sampling and chemical analysis according to the European Moss Survey Protocol (ICP Vegetation 2020). The spatial structure of the measurement values was analyzed by means of Variogram Analysis, and the respective function was used for Kriging-Interpolation. In addition to mapping the nitrogen values according to the international classification, maps based on 10 percentile classes were calculated. Maps for the Moss Survey 2020 data were compared with respective maps produced from the 2005 and 2015 Moss Survey data. Trends in Germany-wide nitrogen medians over the past three campaigns (2005, 2015 and 2020) show that nitrogen medians decreased by -2 % between 2005 and 2015 and increased by +8 % between 2015 and 2020. These differences are not significant and do not match the emission trends. Therefore, emission register data needs to be controlled by monitoring nitrogen deposition with technical and biological samplers and deposition modelling.

Die Anreicherung von chemischen Elementen in Moosen ist ein indirektes Maß für die atmosphärische Deposition und damit eine wichtige Ergänzung der zur Überwachung der Genfer Luftreinhaltekonvention verwendeten Techniken. Ziel des Beitrages ist die Quantifizierung und Kartierung der zeitlichen und räumlichen Trends der Metallanreicherung in Moosen, die in Deutschland 1990, 1995, 2000, 2005, 2010, 2015 und 2020 gesammelt wurden. Sammlung und chemische Analytik der Moosproben erfolgten nach internationalen Richtlinien und beinhalteten Qualitätskontrollen. Für die räumliche Statistik und die Kartierung wurden Variogrammanalyse und Kriging‐Interpolation verwendet. Zur Qualitätskontrolle diente die Kreuzvalidierung. Die im Zeitraum zwischen dem MM 2005 und MM 2015 bei allen Schwermetallen festgestellten Rückgänge setzen sich im Moosmonitoring 2020 (MM 2020) nicht fort. Vielmehr wurden im MM 2020 bei vier der sechs untersuchten Metalle (Cd, Cu, Ni und Sb) höhere Konzentrationen in den Moosproben gemessen als im MM 2015. Die Spannweite reicht von +26 % (Cu) bis +165 % (Ni). Bei As und Pb sind dagegen keine signifikanten Veränderungen im Vergleich zu 2015 festzustellen. Ein zwischenzeitlicher Anstieg wurde auch zwischen 2000 und 2005 für Cr, Sb und Zn ermittelt. Anders verhält sich der langfristige Trend im Vergleich der aktuellen Medianwerte mit denen des Basisjahres (= Jahr der Erstbeprobung): Seit 1990 nehmen die Mediane der Gehalte von As, Cd, Cu, Ni, Pb und Sb in den Moosen signifikant ab, wobei der stärkste Rückgang bei Pb zu verzeichnen ist (−86 %). Auch aus anderen Teilnehmerstaaten des European Moss Survey wird zwischen den Surveys 2015 und 2020 von zunehmenden Metallkonzentrationen in Moosen berichtet. Die in den letzten fünf Jahren gestiegenen Metallgehalte in den Moosen korrespondieren nicht mit den entsprechenden Trends der berichteten Schwermetallemissionen in Deutschland (2015–2020; NaSE 2022). Vielmehr ergeben sich gegenläufige Entwicklungen, d. h., während die Metallemissionen durchweg rückläufig sind, nehmen die gemessenen Konzentrationen in den Moosen zwischen 2015 und 2020 zu. Die größten Diskrepanzen ergeben sich bei Ni. Zum Vergleich wird ähnlich auch von Frankreich eine Zunahme der Pb‐Konzentration in den Moosen zwischen 2015 und 2020 berichtet, obwohl der im französischen Emissionskataster abgebildete Trend abnehmend ist. Die Langfristtrends der in den Moosen gemessenen As‐, Cd‐, Cu‐, Ni‐ und Pb‐Konzentrationen zeigen dagegen insgesamt gute Übereinstimmungen zu den entsprechenden Emissionstrends in Deutschland (1990–2020), wobei auffällt, dass die Langfristtrends in den Moosdaten zumeist schwächer ausgeprägt sind als in den Emissionsdaten. Zu bedenken ist, dass in Deutschland bei nur 26 Orten, an denen Moosproben gesammelt wurden, die Mindestprobenzahlen im MM 2020 für die Metalle nicht erreicht werden. Es kann nicht beurteilt werden, ob die im MM 2015 beobachteten deutlichen Rückgänge der Schwermetallgehalte in den Moosen (n = 397 bis 400) oder der im MM 2020 festgestellte deutliche Anstieg (n = 26) jeweils Ausnahmen im Langfristtrend darstellen. Dies könnte erst im MM 2025 auf Basis einer größeren Stichprobe geklärt werden. Ebenso wäre ein eingehenderer Vergleich mit den aus anderen europäischen Teilnehmerstaaten berichteten Trends der HM‐Gehalte in den Moosen zu empfehlen. Der Vergleich der Trends der Schwermetallemissionen mit den Werten des Moos‐Monitorings legt sehr nachdrücklich nahe, dass es nicht ausreicht, nur Emissionsdaten oder die aus diesen Daten abgeleitete modellierte Deposition zu betrachten. Vielmehr ist deren Ergänzung durch technisch gemessene Immissions‐ bzw. Depositionsdaten unabdingbar. Dies gilt erst recht, weil Emissionsdaten i. d. R. nur unvollständig vorliegen und vielfach nicht auf direkten Messungen (wie bei Hausfeuerungsanlagen) beruhen, sondern auf semiquantitativen Schätzungen. Für eine Analyse der zeitlichen Trends atmosphärischer Schwermetalldeposition durch Vergleich zwischen technisch gemessener Deposition und in Moosen gemessener Bioakkumulation stünden nach derzeitigem Stand in Deutschland mindestens 56 Standorte mit Abständen von weniger als 5 km zwischen den Stationen des Luftgütemessnetzes des Bundes/der Länder und den Standorten des seit 1990 beprobten Moos‐Messnetzes als gepaarte Stichprobe zur Verfügung. Eine darauf aufbauende integrative Trendanalyse würde auch zur Klärung der Frage beitragen, ob und inwieweit die Jahre 2015 oder 2020 als Ausnahmejahre hinsichtlich der Schwermetallgehalte in den Moosen zu einzustufen sind.

Mosses are suitable for recording the bioaccumulation of atmospheric deposition over large areas at many sites. In Europe, such monitoring has been carried out every five years since 1990. Mosses have been collected and chemically analysed for metals (since 1990), nitrogen (since 2005), persistent organic pollutants (since 2010) and microplastics (2020). The aims of this study were the following: (1) to analyse the temporal trends of metal and nitrogen accumulation in mosses between 1990 or 2005, respectively, and 2020 in Germany; (2) to compare the accumulation trends with emission data; and (3) to determine the effect of tree canopy drip on metal and nitrogen accumulation in mosses. For the temporal trend analysis, the minimum sample number required for a reliable estimation of arithmetic mean values and statistical parameters based on it was calculated. It was only achieved for nitrogen, but not for metals. Therefore, the temporal trends of the bioaccumulation of metals and nitrogen were calculated on the basis of median values. For the analysis of tree canopy effects on element accumulation in mosses, 14 vegetation structure measures were used, which together with 80 other descriptors characterise each moss collection site and its environment. The comparison of the data obtained during the first monitoring campaign with those of the 2020 survey showed a significant decrease in metal bioaccumulation. However, in contrast to the emission data, an increase in the accumulation of some metals was observed between 2000 and 2005 and of all metals from 2015 to 2020. Trends in Germany-wide nitrogen medians over the last three campaigns (2005, 2015 and 2020) show that nitrogen medians decreased by −2% between 2005 and 2015 and increased by +8% between 2015 and 2020. These differences are not significant and do not match the emission trends. Inferential statistics confirmed significantly higher metals and nitrogen accumulation in mosses collected under tree canopies compared to adjacent open areas. Measured concentrations of metals and nitrogen were significantly higher under tree canopies than outside of them, by 18–150%.

Ziel der hier vorgestellten Untersuchungen war es, die Trends der Metall- und Stickstoffakkumulation in Moosen zwischen 1990 bzw. 2005 und 2020 in Deutschland sowie die Auswirkung der Baumkronentraufe auf die Elementanreicherung zu ermitteln. Für die Trendanalyse wurde die Mindeststichprobenanzahl berechnet, die für eine zuverlässige Schätzung arithmetischer Mittelwerte und darauf beruhender statistischer Kennwerte erforderlich ist. Die Mindestprobenzahl wurde nur bei den Stickstoffmessungen erreicht. Daher wurden die Trends der Bioakkumulation von Metallen und Stickstoff anhand der Medianwerte berechnet. Für die Analysen der Baumkronentraufeffekte auf die Elementgehalte in Moosen wurden 14 Vegetationsstrukturmaße verwendet. Der Vergleich der bei der ersten Monitoring-Kampagne ermittelten Daten mit denen der Erhebung von 2020 zeigte einen deutlichen Rückgang der Bioakkumulation von Metallen. Im Gegensatz zu den Daten für die deutsche Berichterstattung atmosphärischer Metallemissionen stiegen zwischen 2000 und 2005 die Gehalte einiger sowie von 2015 bis 2020 die Gehalte aller Metalle in Moosen an. Die Konzentrationen von Metallen und Stickstoff waren unter Baumkronen signifikant höher als im Freiland. Die Stickstoffmediane sind zwischen 2005 und 2015 um –2 % gesunken und zwischen 2015 und 2020 um 8 % gestiegen. Diese Unterschiede sind nicht signifikant und stimmen nicht mit den Daten für die deutsche Berichterstattung atmosphärischer Stickstoffemissionen überein.

Introduction: Following their transport, atmospheric pollutants are deposited on the ground, on plants or on water. Depending on the substances involved, ecosystems can be adversely affected by the deposition of nutrients or pollutants. In order to be able to counteract the potential ecological risks through environmental policy measures, it is necessary to measure the atmospheric inputs of potentially harmful substances. For this reason, heavy metal concentrations in mosses used as accumulators of atmospherically deposited substances have been determined since 1990 for every five years at up to 7300 locations in up to 34 European countries. In 2005 nitrogen was added. Persistent organic compounds were determined for the first time in the European Moss Survey in 2010, in Germany firstly in the Moss Survey of 2015/2016. Microplastics were added to this group of substances for the 2020/2021 survey. Here, we are presenting results for microplastic and a variety of persistent organic pollutants (POP) from the 2020/2021 moss survey in Germany. Materials and Methods: Sampling was performed at 20 sites according to the recommendations of the Moss Survey Manual. Afterwards a sample preparation method was established for Thermo-Extraction-Desorption-GC-MS and RAMAN spectroscopy to analyze the microplastic concentration as well as number in the moss samples. Analyses for POPs were performed as described by Dreyer et al. 2018 with slight modifications. Overall, about 120 compounds (PAH, PCDD/F, PCB, PFAS, HBCD, PBB, PBDE, alternative halogenated flame retardants (HFR)) were analysed. Results: In all Moss samples microplastic were detected. The highest concentration in all samples was observed for polyethylene, followed by polyethylene terephthalate, polypropylene and styrene-butadiene and in one sample polystyrene. At the two sampling sites near the sea the highest microplastic concentrations were indicated, whereas no correlation with the other sampling location (urban, agriculture, forest) could be detected. PBB and indicator PCB were not observed above the LOQ in any sample. PFAS and dioxin-like PCBs were very rarely found above the LOQ. In contrast, certain PCDD/F, PAH, HBCD, PBDE and HFR were frequently observed. Current concentrations at sampling sites compared to those of sites that have also been investigated in 2015/2016 were in the same order of magnitude or declined. For HBCD, concentrations declined distinctly by a factor of up to 9. Conclusions: Microplastics and many POPs were observed in moss samples indicating their suitability to monitor atmospheric deposition of these substance groups by this bioindicator. Challenges exist for PBB, PCB or PFAS either because environmental concentrations are too low with respect to the LOQ or the pollutants’ environmental behavior limit accumulation in moss. Within the past five years, most POPs concentrations in moss samples from Germany stayed more or less the same or decreased.Acknowledgements:We are thankful to the German Environment Agency (Umweltbundesamt) for funding this study (FKZ 3720632010). References: UNECE ICP VEGETATION (2020) Heavy metals, nitrogen and POP in European mosses: 2020 survey monitoring manual. https://icpvegetation.ceh.ac.uk/sites/default/files/ICP%20Vegetation%20moss% 20monitoring %20manual %202020.pdf Dreyer A, Nickel S, Schröder W. et al. (2018). Environ. Sci. Eur. 30 (43): 1-14.

&lt;p&gt;Mosses are suitable for recording the bioaccumulation of atmospheric deposition over large areas at many sites. In Europe, such monitoring has been carried out every five years since 1990. Mosses have been collected and chemically analysed for metals (since 1990), nitrogen (since 2005), persistent organic pollutants (since 2010) and microplastics (2020). The aims of this study were: 1. To analyse the temporal trends of metal and nitrogen accumulation in mosses between 1990 or 2005, respectively, and 2020 in Germany; 2. To compare the accumulation trends with emission data; and 3. To determine the effect of tree canopy drip on metal and nitrogen accumulation in mosses. For the temporal trend analysis, the minimum sample number required for a reliable estimation of arithmetic mean values and statistical parameters based on it was calculated. It was only achieved for nitrogen, but not for metals. Therefore, the temporal trends of bioaccumulation of metals and nitrogen were calculated on the basis of median values. For the analyses of tree canopy effects on elements accumulation in mosses, 14 vegetation structure measures were used, which together with 80 other descriptors characterise each moss collection site and its environment. The comparison of the data obtained during the first monitoring campaign with those of the 2020 survey showed a significant decrease in metals bioaccumulation. However, in contrast to the emission data, an increase in accumulation of some metals was observed between 2000 and 2005 and of all metals from 2015 to 2020. Trends in Germany-wide nitrogen medians over the last three campaigns (2005, 2015, 2020) show that nitrogen medians decreased by -2% between 2005 and 2015 and increased by +8% between 2015 and 2020. These differences are not significant and do not match the emission trends. Inferential statistics confirmed significantly higher metal and nitrogen accumulation in mosses collected under tree canopies compared to adjacent open areas. Measured concentrations of metals and nitrogen were significantly higher under tree canopies than outside of them, by 18-150 %.&lt;/p&gt; &lt;p&gt;Keywords: Bioaccumulation; regression analysis; trend analysis&lt;/p&gt;

The aim was to determine 1st the trends in metal and nitrogen accumulation in mosses between 1990 and 2005 and 2020 in Germany, respectively, and 2nd the effect of tree canopy cover on element accumulation. For the trend analysis, the minimum sample number required for a reliable estimation of arithmetic mean values and statistical parameters based on them was calculated. The minimum sample number was only achieved for the nitrogen measurements. Therefore, the trends of bioaccumulation of metals and nitrogen were calculated using the median values. For the analyses of tree canopy effects on element contents in mosses, 14 vegetation structure measures were used. The comparison of the data determined during the first monitoring campaign with those of the 2020 survey showed a clear decrease in the bioaccumula- tions of metals. In contrast to the emission data, levels of some metals in mosses increased between 2000 and 2005, and those of all metals between 2015 and 2020. The concentrations of metals and nitrogen were significantly higher under tree canopies than in the open. The nitrogen medians decreased by -2 % between 2005 and 2015 and increased by +8 % between 2015 and 2020. These differences are not significant and are not consistent with emission trends.

PCDD/Fs and 209 PCBs were investigated in ambient air and atmospheric deposition at two background monitoring sites in Germany over a period of 12 months in 2018/19. Both substance groups have been frequently found in ambient air, principally with the expected seasonal variations. In deposition, PCDD/Fs as well as PCBs were frequently below the method quantification limits. Besides the frequently investigated dioxin-like PCBs and six indicator PCBs, the analysis of the 209 PCBs (166 separated PCB-peaks) enabled the identification and evaluation of additional PCBs that might be of environmental concern. Of 166 PCBs or PCB-coelutions, up to 144 were quantified in air samples and up to 94 in atmospheric deposition samples. Some of these PCBs were observed at levels similar to or exceeding those of the frequently investigated six indicator PCBs. Important additional PCBs in ambient air were PCB 5/8, PCB 11, PCB 17, PCB 18, PCB 20/33, PCB 31, PCB 43/49, PCB 44, PCB 47/48/65/75, PCB 93/95/98/102, PCB 139/149, and PCB 151. The presence of these PCBs in atmospheric samples implies that routine analysis oversees potentially important contaminants.

In Europe, mosses are used as bio-accumulators of atmospheric deposition of various substances. Using Germany as an example, measurement results on the accumulation of heavy metals and nitrogen between 1990 and 2015 are summarised. Furthermore, results of the determination of persistent organic compounds in mosses collected in 2015 are presented. Finally, the method development for monitoring microplastics with mosses collected in 2021 is explained and preliminary results are presented. Heavy metal accumulation in mosses decreased significantly during the years 1990 to 2015. This trend is not continuous for every element but for some elements it is associated with an intermittent standstill or increase. The nitrogen contents of mosses remained high between 2005 and 2015. Apart from polybrominated biphenyls (PBBs) and perfluoroalkyl substances (PFASs), persistent organic pollutants (POP) of all substance groups were quantified in the 2015 moss monitoring, albeit to varying degrees. Micro plastics could be found in all moss samples examined so far in the Moss Survey 2020/2021 indicating that moss seems to be suitable for the detection of microplastics originating from atmospheric deposition.

Wet, dry, and occult atmospheric deposition may be modified by vegetation canopies. The aim of this study was to verify canopy drip effect studies conducted in 2012, in 2013, and in 2015/2016. For this purpose, 26 moss samples were taken at each of eight monitoring sites of the European Moss Survey 2020/2021 in Germany from a corresponding number of subplots, each representing the site categories "under tree canopy" and adjacent "open land". The sampling, as well as the chemical analyses, of 12 metals (Al, As, Cd, Cr, Cu, Fe, Hg, Pb, Ni, Sb, V, Zn) and nitrogen (N) and the recording of sample- and site-describing metadata were conducted according to the ICP Vegetation experimental protocol. The results demonstrate an overall higher metal and nitrogen accumulation in moss samples of "canopy" sites compared to neighboring "open land sites" (grassland, heath). The ratios between the "canopy" and "open land" sites of 1.18 to 1.69 and significant correlations of r > 0.8 in case of five elements agree well with corresponding values from samplings in 2012, 2013, and 2015/2016. These results should be used for modeling atmospheric deposition aiming at more realistic results. With regard to the question of whether, and to what extent, moss samples should preferably be taken from "open land" or "canopy" sites, the following can be concluded: The recommendations of ICP Vegetation with regard to the minimum distance to be maintained from trees and shrubs should not be interpreted to mean that "open" sites are fundamentally more suitable for moss sampling in Germany than, for example, clearings in forests. The mostly higher variability of the measured values compared to the "canopy" sites rather suggests that in the open country a much higher number of influencing factors could be significant for the element accumulation in mosses in addition to the background pollution through atmospheric deposition. This is also supported by the fact that the metal contents in the moss samples of the "open" sites can clearly exceed those of the neighboring "canopy" sites in individual cases. With regard to "open" land, grassland sites seem to be less suitable for moss sampling than bog and heathland sites. In grassland, moss occurrences are often sparser and/or cut short by meadow mowing, so that the removal of three-year shoots on grassland, as recommended by ICP Vegetation, must be replaced in places by one-year shoots. The comparatively higher state dynamics of grassland sites also make the resampling of moss at previously sampled sites more difficult.

Hintergrund und Ziel. Nasse, trockene und okkulte atmosphärische Deposition kann durch Vegetation beeinflusst werden. Ziel dieser Studie war es, entsprechende Canopy Drip-Effektstudien aus den Jahren 2012, 2013 und 2015/2016 (Kluge et al. 2013; Meyer et al. 2015a, 2015b; Meyer 2017; Nickel & Schröder 2018; Schröder & Nickel 2018; Schröder et al. 2019) zu verifizieren. Materialien und Methoden. An acht Monitoringstandorten des European Moss Survey in Deutschland wurden 25 Moosproben aus einer entsprechenden Anzahl von Teilflächen entnommen, die jeweils die Standortkategorien „unter Baumkronen“ und angrenzendes „Offenland“ repräsentieren. Die Probenentnahme sowie die chemischen Analysen und die Erfassung von proben- und standortbeschreibenden Metadaten erfolgten gemäß ICP Vegetation (2020). Ergebnisse. Die Ergebnisse zeigen erneut eine insgesamt höhere HM- und N-Akkumulation in Moosproben von „Kronendach“-Standorten im Vergleich zu benachbarten „Offenland-Standorten“ (Grünland, Heide). Die Verhältnisse zwischen „Kronendach“- und „Offenland“-Standorten von 1,18 bis 1,69 und signifikante Korrelationen von r > 0,8 bei fünf Elementen stimmen gut mit entsprechenden Werten aus Beprobungen in den Jahren 2012, 2013 und 2015/2016 (Kluge et al. 2013; Meyer et al. 2015a, 2015b; Meyer 2017; Nickel & Schröder 2018; Schröder & Nickel 2018; Schröder et al. 2019) überein. Schlussfolgerungen. Hinsichtlich der Frage, ob und in welchem Umfang Moosproben vorzugsweise von „Offenland“- oder „Kronendach“-Standorten entnommen werden sollten, kann folgendes Fazit gezogen werden: Die Empfehlungen des ICP Vegetation (2020) hinsichtlich des einzuhaltenden Mindestabstandes zu Bäumen und Sträuchern sollten nicht dahingehend interpretiert werden, dass „Offenland“-Standorte für die Moosbeprobung in Deutschland grundsätzlich besser geeignet sind als z. B. Lichtungen im Wald. Die meist höhere Variabilität der Messwerte im Vergleich zu den „Kronendach“-Standorten deutet vielmehr darauf hin, dass im Offenland neben der Hintergrundbelastung durch atmosphärische Deposition eine viel größere Anzahl von Einflussfaktoren für die Elementanreicherung in Moosen bedeutsam sein könnte. Dafür spricht auch, dass die HM-Gehalte in den Moosproben der „Offenland“-Standorte in Einzelfällen deutlich über denen der benachbarten „Kronendach“-Standorte liegen können. Was die „offenen“ Flächen betrifft, so scheinen Grünlandflächen für Moosproben weniger geeignet zu sein als Moor- und Heideflächen. Im Grünland sind die Moosvorkommen oft spärlicher und/oder durch Wiesenmahd verkürzt, sodass die von ICP Vegetation (2020) empfohlene Entfernung von dreijährigen Trieben auf Grünland stellenweise durch einjährige Triebe ersetzt werden muss. Die vergleichsweise höhere Zustandsdynamik von Grünlandflächen erschwert zudem die erneute Beprobung von Moosen an zuvor beprobten Standorten. Background and Aim. Wet, dry and occult atmospheric deposition may be modified by vegetation canopies. The aim of this study was to verify canopy drip effect studies conducted in 2012, 2013 and 2015/2016 (Kluge et al. 2013; Meyer et al. 2015a, 2015b; Meyer 2017; Nickel & Schröder 2018; Schröder & Nickel 2018; Schröder et al. 2019). Materials and Methods. At eight monitoring sites of the European Moss Survey in Germany, 25 moss samples were collected from the respective number of sub-plots, each representing the location categories “under-tree canopies” and neighbouring “open land”. The sampling as well as the chemical analyses and the recording of sample- and site-describing metadata were conducted according to ICP Vegetation (2020). Results. The results again demonstrate an overall higher HM and N accumulation in moss samples of “canopy” sites compared to neighbouring “open land” sites (grassland, heath). The ratios between the “canopy” and “open land” sites of 1.18 to 1.69 and significant correlations of r > 0.8 in case of five elements agree well with the corresponding values from samplings in 2012, 2013 and 2015/2016 (Kluge et al. 2013; Meyer et al. 2015a, 2015b; Meyer 2017; Nickel & Schröder 2018; Schröder & Nickel 2018; Schröder et al. 2019). Conclusions. With regard to the question of whether, and to what extent, moss samples should preferably be taken from “open land” or “canopy” sites, the following can be concluded: The recommendations of ICP Vegetation (2020) with regard to the minimum distance to be maintained from trees and shrubs should not be interpreted to mean that “open” sites are fundamentally more suitable for moss sampling in Germany than, for example, clearings in forests. The mostly higher variability of the measured values compared to the “canopy” sites rather suggests that in the open country a much higher number of influencing factors could be significant for the element accumulation in mosses, in addition to the background pollution through atmospheric deposition. This is also supported by the fact that the HM contents in the moss samples of the “open” sites can clearly exceed those of the neighbouring “canopy” sites in individual cases. With regard to “open” land, grassland areas seem to be less suitable for moss sampling than bog and heathland sites. In grassland, moss occurrences are often sparser and/or cut short by meadow mowing, so that the removal of three-year-old shoots on grassland, as recommended by ICP Vegetation (2020), must be replaced in parts by the removal of one-year-old shoots. The comparatively higher state dynamics of grassland areas also make the resampling of moss at previously sampled sites more difficult.

Polyurethane foam passive air samplers (PUF-PAS) are the most common type of passive air sampler used for a range of semi-volatile organic compounds (SVOCs), including regulated persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAHs), and emerging contaminants (e.g., novel flame retardants, phthalates, current-use pesticides). Data from PUF-PAS are key indicators of effectiveness of global regulatory actions on SVOCs, such as the Global Monitoring Plan of the Stockholm Convention on Persistent Organic Pollutants. While most PUF-PAS use similar double-dome metal shielding, there is no standardized dome size, shape, or deployment configuration, with many different PUF-PAS designs used in regional and global monitoring. Yet, no information is available on the comparability of data from studies using different PUF-PAS designs. We brought together 12 types of PUF-PAS used by different research groups around the world and deployed them in a multi-part intercomparison to evaluate the variability in reported concentrations introduced by different elements of PAS monitoring. PUF-PAS were deployed for 3 months in outdoor air in Kjeller, Norway in 2015-2016 in three phases to capture (1) the influence of sampler design on data comparability, (2) the influence of analytical variability when samplers are analyzed at different laboratories, and (3) the overall variability in global monitoring data introduced by differences in sampler configurations and analytical methods. Results indicate that while differences in sampler design (in particular, the spacing between the upper and lower sampler bowls) account for up to 50 % differences in masses collected by samplers, the variability introduced by analysis in different laboratories far exceeds this amount, resulting in differences spanning orders of magnitude for POPs and PAHs. The high level of variability due to analysis in different laboratories indicates that current SVOC air sampling data (i.e., not just for PUF-PAS but likely also for active air sampling) are not directly comparable between laboratories/monitoring programs. To support on-going efforts to mobilize more SVOC data to contribute to effectiveness evaluation, intercalibration exercises to account for uncertainties in air sampling, repeated at regular intervals, must be established to ensure analytical comparability and avoid biases in global-scale assessments of SVOCs in air caused by differences in laboratory performance.

The historical air pollution with halogenated flame retardants (HFRs) in Germany was assessed by investigating tree leaf and shoot samples which have been archived in the German environmental specimen bank. Samples covered the period from 1985 to 2016. 43 HFRs comprising polybrominated diphenyl ethers as well as emerging brominated and chlorinated compounds such as Dechlorane Plus, DBDPE, or DPTE, were analysed in 115 samples from ten sub sites originating from six areas characterised by different land uses, including urban as well as a background site. HFRs were observed in each sample showing the widespread distribution of HFRs in Germany in tree leaves and shoots as bioindicators of past and present atmospheric pollution. Analytes observed at elevated concentrations were BDE 209, DBDPE and DPTE. Observed HFR-levels differed between analytes as well as sampling locations, particularly prior to the year 2000. They were typically highest at conurbation areas. Concentrations at the background site often belonged to the lowest ones observed, however, lowest values were not exclusively found there. The quantification frequencies appeared to decrease from the past to most recent samples. With few exceptions, atmospheric pollution of both, legacy and emerging HFRs, decreased significantly.