The Arctic terrestrial environment harbors a complex mosaic of mercury (Hg) and carbon (C) reservoirs, some of which are rapidly destabilizing in response to climate warming. The sources of riverine Hg across the Mackenzie River basin (MRB) are uncertain, which leads to a poor understanding of potential future release. Measurements of dissolved and particulate mercury (DHg, PHg) and carbon (DOC, POC) concentration were performed, along with analyses of Hg stable isotope ratios (incl. ∆199Hg, d202Hg), radiocarbon content (∆14C) and optical properties of DOC of river water. Isotopic ratios of Hg revealed a closer association to terrestrial Hg reservoirs for the particulate fraction, while the dissolved fraction was more closely associated with atmospheric deposition sources of shorter turnover time. There was a positive correlation between the ∆14C-OC and riverine Hg concentration for both particulate and dissolved fractions, indicating that waters transporting older-OC (14C-depleted) also contained higher levels of Hg. In the dissolved fraction, older DOC was also associated with higher molecular weight, aromaticity and humic content, which are likely associated with higher Hg-binding potential. Riverine PHg concentration increased with turbidity and SO4 concentration. There were large contrasts in Hg concentration and OC age and quality among the mountain and lowland sectors of the MRB, which likely reflect the spatial distribution of various terrestrial Hg and OC reservoirs, including weathering of sulfate minerals, erosion and extraction of coal deposits, thawing permafrost, forest fires, peatlands, and forests. Results revealed major differences in the sources of particulate and dissolved riverine Hg, but nonetheless a common positive association with older riverine OC. These findings reveal that a complex mixture of Hg sources, supplied across the MRB, will contribute to future trends in Hg export to the Arctic Ocean under rapid environmental changes.

The study is aimed at determining the potential spatiotemporal risk of the co-occurrence of airborne pollen and fungal spores high concentrations in different bio-climatic zones in Europe. Birch, grass, mugwort, ragweed, olive pollen and Alternaria and Cladosporium fungal spores were investigated at 16 sites in Europe, in 2005–2019. In Central and northern Europe, pollen and fungal spore seasons mainly overlap in June and July, while in South Europe, the highest pollen concentrations occur frequently outside of the spore seasons. In the coldest climate, no allergy thresholds were exceeded simultaneously by two spore or pollen taxa, while in the warmest climate most of the days with at least two pollen taxa exceeding threshold values were observed. The annual air temperature amplitude seems to be the main bioclimatic factor influencing the accumulation of days in which Alternaria and Cladosporium spores simultaneously exceed allergy thresholds. The phenomenon of co-occurrence of airborne allergen concentrations gets increasingly common in Europe and is proposed to be present on other continents, especially in temperate climate.

Forty-four unhatched eggs from white-tailed sea eagle (Haliaeetus albicilla), collected in four regions inSweden in 1992–2005, were analysed for contents of polybrominated diphenyl ethers (PBDEs),polybrominated biphenyl (PBB), hexabromocyclododecane (HBCD) and naturally occurring methoxylatedpolybrominated diphenyl ethers (MeO-PBDEs). Two freshwater areas—Lapland in the arctic zone (LAP) andinland lakes in central and southern Sweden (INL), and two brackish marine areas in the Baltic Sea—thesouth Bothnian Sea (SB) and the Baltic Proper (BP)—were chosen for comparison of the concentrations andcongener distributions in white-tailed sea eagles with different diet and migratory patterns. The geometricmean (GM) concentrations (ng/g lipid weight (l.w.)) of ∑5PBDE (BDE-47, -99, -100, -153, and -154) were720 (LAP), 1500 (INL), 4 100 (SB) and 4 300 (BP), whereas BDE-209 was not detectable in any of the samples.The GM concentrations for HBCD content in LAP, INL, SB and BP were 60, 90, 150 and 140 ng/g l.w.,respectively, whereas the corresponding values for BB-153 were 20, 30, 100 and 120 ng/g l.w. In general, theeggs from all four regions demonstrated similar patterns of PBDE congeners, with concentrations indescending order of BDE-47, -100, -99, -153 and -154. The ∑3-MeO-BDEs (6-MeO-BDE47, 2′-MeO-BDE68,5-Cl-6-MeO-BDE47) for these same regions (as above) were 80, 40, 340 and 240 ng/g l.w., respectively.∑3-MeO-BDEs for LAP and INL (freshwaters) were significantly different, whereas those for SB and BP were not.The presence of MeO-PBDEs in all of the inland samples indicates that there is an as-yet-unidentified sourceof these compounds in the freshwater ecosystem. Between the two more contaminated subpopulationsfrom the Baltic Sea coast, SB showed significantly lower productivity than BP, but no correlation was foundbetween productivity and PBDE, PBB and HBCD at the concentrations found in this study.

Concentrations of polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated dibenzofurans (PCDF), and dioxin-like non-ortho-PCBs were measured in white-tailed sea eagle (WTSE) eagle eggs collected along the Swedish coast of the Baltic Sea during the period 1992–2004. The eggs represent two different subpopulations with significantly different nestling brood sizes; the Baltic Proper (BP) with an approximately normal nestling brood size (1.62), and the south Bothnian Sea (sBS) with reduced nestling brood size (1.22) combined with asigni ficantly higher rate of dead eggs. The aim was to investigate if this difference in reproductive outcome was linked to differences in exposure to dioxin-like compounds. Three eggs collected in Greenland in 200 were included in the study to provide a reference sea eagle population outside of the Baltic Sea region. The concentrations of ΣPCDD, ΣPCDF and Σnon-ortho-PCB in the two subpopulations from the Baltic Sea (BS) region ranged from 0.41–4.1, 1.2–5.3 and 180–970 ng/g lipids, respectively, while in the Greenland population the ranges were 0.11–0.16, 0.22–0.33 and 57–83 ng/g lipid, respectively. 2,3,4,7,8-PCDF was the predominant congener in all areas and accounted for on average 31–49% of the total ΣPCDD/F concentrations. The total toxic equivalents (TEQ) in sBS WTSEs were higher (approximately 39 ng TEQ/g lipid) than reported in eggs for many other birds, and the major contributors to the TEQ in the Baltic Sea were the non-ortho-PCBs. A principal component analysis (PCA) showed a difference in congener pattern between the two Baltic regions that was statistically significant (Hotelling's T2 test). Wefound no significant differencesin the total TEQ between the two populations (sBS–BP) and thus no evidence was found linking the reproductive impairment in WTSE in sBS to the concentrations of PCDD/Fs or non-ortho-PCBs in the eggs.

Concentrations of polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated dibenzofurans (PCDF), and dioxin-like non-ortho-PCBs were measured in white-tailed sea eagle (WTSE) eagle eggs collected along the Swedish coast of the Baltic Sea during the period 1992-2004. The eggs represent two different subpopulations with significantly different nestling brood sizes; the Baltic Proper (BP) with an approximately normal nestling brood size (1.62), and the south Bothnian Sea (sBS) with reduced nestling brood size (1.22) combined with a significantly higher rate of dead eggs. The aim was to investigate if this difference in reproductive outcome was linked to differences in exposure to dioxin-like compounds. Three eggs collected in Greenland in 2000 were included in the study to provide a reference sea eagle population outside of the Baltic Sea region. The concentrations of ∑PCDD, ∑PCDF and ∑non-ortho-PCB in the two subpopulations from the Baltic Sea (BS) region ranged from 0.41-4.1, 1.2-5.3 and 180-970 ng/g lipids, respectively, while in the Greenland population the ranges were 0.11-0.16, 0.22-0.33 and 57-83 ng/g lipid, respectively. 2,3,4,7,8-PCDF was the predominant congener in all areas and accounted for on average 31-49% of the total ∑PCDD/F concentrations. The total toxic equivalents (TEQ) in sBS WTSEs were higher (approximately 39 ng TEQ/g lipid) than reported in eggs for many other birds, and the major contributors to the TEQ in the Baltic Sea were the non-ortho-PCBs. A principal component analysis (PCA) showed a difference in congener pattern between the two Baltic regions that was statistically significant (Hotelling's T(2) test). We found no significant differences in the total TEQ between the two populations (sBS-BP) and thus no evidence was found linking the reproductive impairment in WTSE in sBS to the concentrations of PCDD/Fs or non-ortho-PCBs in the eggs.

Ecological communities are structured by several mechanisms, including temporal, spatial and environmental factors. However, the simultaneous effects of these factors have rarely been studied. Here, we investigated their role on water beetle assemblages sampled over a period of 18 years. Water beetles were sampled in the spring of each year in lotic and lentic water bodies from mainland region of Kalmar and Öland Island in southeastern Sweden. We assessed how past assemblage structure, environmental factors and spatial variables correlated with current assemblage structure using a variation partitioning approach. We also tested for correlates of temporal beta diversity of water beetle assemblages with multiple regressions. We found that past water beetle assemblage structure explained current water beetle assemblage structure better than the environmental and spatial correlates. We also observed that temporal beta diversity of water beetle assemblages was mainly due to species gain rather than to species loss. Finally, environmental variables (e.g., hydroperiod, habitat size and hydrology) and timespan between sampling events explained part of temporal beta diversity and contribution of species loss to total assemblage dissimilarity variation. Despite the fact that most variation remained unexplained, we found that ecological factors that have been thought to be important for water beetle richness and abundance in past studies (e.g. water body size, water permanence, shore slope, and whether the water body is lentic or lotic) were also correlated to temporal beta diversity. From a conservation point of view, our study suggest that temporal variability of assemblage structure should be included in biological monitoring because of its potential to predict current assemblage structure.

Rapid biodiversity loss has emphasized the need to understand how biodiversity affects the provisioning of ecological functions. Of particular interest are species and communities with versatile impacts on multiple parts of the environment, linking processes in the biosphere, lithosphere, and atmosphere to human interests in the anthroposphere (in this case, cattle farming). In this study, we examine the role of a specific group of insects - beetles feeding on cattle dung - on multiple ecological functions spanning these spheres (dung removal, soil nutrient content and greenhouse gas emissions). We ask whether the same traits which make species prone to extinction (i.e. response traits) may also affect their functional efficiency (as effect traits). To establish the link between response and effect traits, we first evaluated whether two traits (body mass and nesting strategy, the latter categorized as tunnelers or dwellers) affected the probability of a species being threatened. We then tested for a relationship between these traits and ecosystem functioning. Across Scandinavian dung beetle species, 75% of tunnelers and 30% of dwellers are classified as threatened. Hence, nesting strategy significantly affects the probability of a species being threatened, and constitutes a response trait. Effect traits varied with the ecological function investigated: density-specific dung removal was influenced by both nesting strategy and body mass, whereas methane emissions varied with body mass and nutrient recycling with nesting strategy. Our findings suggest that among Scandinavian dung beetles, nesting strategy is both a response and an effect trait, with tunnelers being more efficient in providing several ecological functions and also being more sensitive to extinction. Consequently, functionally important tunneler species have suffered disproportionate declines, and species not threatened today may be at risk of becoming so in the near future. This linkage between effect and response traits aggravates the consequences of ongoing biodiversity loss.

The paper suggests amethodology for predicting next-year seasonal pollen index (SPI, a sumof daily-mean pollen concentrations)over large regions and demonstrates its performance for birch in Northern andNorth-Eastern Europe. Astatistical model is constructed using meteorological, geophysical and biological characteristics of the previous year).A cluster analysis of multi-annual data of European Aeroallergen Network (EAN) revealed several large regions inEurope, where the observed SPI exhibits similar patterns of the multi-annual variability.We built the model for thenorthern cluster of stations, which covers Finland, Sweden, Baltic States, part of Belarus, and, probably, Russia andNorway,where the lack of data did not allow for conclusive analysis. The constructed modelwas capable of predictingthe SPI with correlation coefficient reaching up to 0.9 for somestations, odds ratio is infinitely high for 50% of sites insidethe region and the fraction of prediction fallingwithin factor of 2 from observations, stays within 40–70%. In particular,model successfully reproduced both the bi-annual cycle of the SPI and years when this cycle breaks down.

Arctic mercury (Hg) concentrations respond to changes in anthropogenic Hg emissions and environmental change. This manuscript, prepared for the 2021 Arctic Monitoring and Assessment Programme Mercury Assessment, explores the response of Arctic Ocean Hg concentrations to changing primary Hg emissions and to changing sea-ice cover, river inputs, and net primary production. To do this, we conduct a model analysis using a 2015 Hg inventory and future anthropogenic Hg emission scenarios. We model future atmospheric Hg deposition to the surface ocean as a flux to the surface water or sea ice using three scenarios: No Action, New Policy (NP), and Maximum Feasible Reduction (MFR). We then force a five-compartment box model of Hg cycling in the Arctic Ocean with these scenarios and literature-derived climate variables to simulate environmental change. No Action results in a 51% higher Hg deposition rate by 2050 while increasing Hg concentrations in the surface water by 22% and <9% at depth. Both “action” scenarios (NP and MFR), implemented in 2020 or 2035, result in lower Hg deposition ranging from 7% (NP delayed to 2035) to 30% (MFR implemented in 2020) by 2050. Under this last scenario, ocean Hg concentrations decline by 14% in the surface and 4% at depth. We find that the sea-ice cover decline exerts the strongest Hg reducing forcing on the Arctic Ocean while increasing river discharge increases Hg concentrations. When modified together the climate scenarios result in a ≤5% Hg decline by 2050 in the Arctic Ocean. Thus, we show that the magnitude of emissions-induced future changes in the Arctic Ocean is likely to be substantial compared to climate-induced effects. Furthermore, this study underscores the need for prompt and ambitious action for changing Hg concentrations in the Arctic, since delaying less ambitious reduction measures–like NP–until 2035 may become offset by Hg accumulated from pre-2035 emissions.

Fish tissue levels have to comply with environmental quality standards (EQSs) within the European Water Framework Directive. However, within monitoring, contaminants are sometimes measured in a different tissue than the tissue for which the environmental (whole fish) or human (fillet (equivalent to muscle tissue)) quality standard is set. Tissue conversion factors (k), describing the relationship between concentrations in different tissues, can be used to obtain a quality standard for the appropriate tissue. Several different approaches have been suggested for the calculation of k. For monitoring purposes, we propose the use of a simple, easy reproducible approach that assumes proportionality between two tissue, or tissue and whole fish, concentrations. This allows for an easy comparison of studies and adoption of ks into independent monitoring programs. Here, we determined ks for three metals (mercury (Hg), lead (Pb), cadmium (Cd)) and nine per- and polyfluoroalkyl substances (PFAS) including perfluorooctanesulfonic acid (PFOS) across six marine and freshwater fish species from Northern European lakes and the Baltic Sea. We found significant species differences for Hg for k_muscle/whole fish, for Cd and Pb for k_{liver/whole fish} and for Cd for kliver/muscle. For perfluoroalkyl carboxylic acids (PFCA), we found a chain length dependence with lowest kliver/muscle at low and high chain lengths (C₈, C₁₃) and highest for median chain lengths (C₉-C₁₂). Further, there were differences between fish species with k_liver/muscle for PFOS almost doubling from eelpout (10.3) to herring (19.2) and increasing up to a factor 4 between eelpout and herring for other PFASs. FOSA had two distinctive groups, herring with a k_liver/muscle of 48.7 and a second group with ks of 2.3 to 5.9 for all other fish species. Our results suggest that differences in the tissue somatic index, and contaminant uptake, tissue transfer and metabolism result in the need for species-specific ks within monitoring

The spatiotemporal trends of mercury (Hg) are crucial for the understanding of this ubiquitous and toxic contaminant. However, uncertainties often arise from comparison among studies using different species, analytical and statisticalmethods. The long-termtemporal trends of Hg exposurewere reconstructed for a key sentinel species, the white-tailed eagle (Haliaeetus albicilla). Body feathers were sampled from museum collections covering 150 years in time (from 1866 to 2015) from West Greenland (n = 124), Norway (n = 102), and Sweden (n= 87). A significant non-linear trend was observed in the Norwegian subpopulation, with a 60% increase in exposure occurring from1866 to 1957 followed by a 40% decline until 2015. In the Swedish subpopulation, studied at a later period, the Hg exposure showed a drastic decline of 70% from 1967 to 2011. In contrast, no significant trend could be observed in the Greenland subpopulation. The additional analysis of dietary proxies (δ13C and δ15N) in general increased performance of the temporal trend models, but this was dependent on the subpopulation and study period. The downward trend of Hg coincided with the decreasing δ13C and δ15N in the Norwegian subpopulation, suggesting a potential dietary mitigation of Hg contamination. Hg exposure in both the Greenland andNorwegian subpopulationswas consistently belowthe suggested threshold for adverse health effects (40.0 μg g−1),while the maximumexposure in the Swedish subpopulationwas distinctively elevated (median: 46.0 μg g−1) and still remains well above natural background concentrations (maximum 5.0 μg g−1).

The environmental and human health concerns for organohalogen contaminants (OHCs) extend beyond the 23 persistent organic pollutants (POPs) regulated by the Stockholm Convention. The current, intense industrial production and use of chemicals in China and their bioaccumulation makes Chinese wildlife highly suitable for the assessment of legacy, novel and emerging environmental pollutants. In the present study, six species of amphibians, fish and birds were sampled from paddy fields in the Yangtze River Delta (YRD) were screened for OHCs. Some extensive contamination was found, both regarding number and concentrations of the analytes, among the species assessed. High concentrations of chlorinated paraffins were found in the snake, Short-tailed mamushi (range of 200-340 μg g(-)(1)lw), Peregrine falcon (8-59 μg g(-1)lw) and Asiatic toad (97 μg g(-)(1)lw). Novel contaminants and patterns were observed; octaCBs to decaCB made up 20% of the total polychlorinated biphenyls (PCBs) content in the samples and new OHCs, substituted with 5-8 chlorines, were found but are not yet structurally confirmed. In addition, Dechlorane 602 (DDC-DBF) and numerous other OHCs (DDTs, hexachlorocyclohexanes (HCHs), polybrominated diphenyl ethers (PBDEs), hexbromocyclododecane (HBCDD), chlordane, heptachlor, endosulfan and Mirex) were found in all species analyzed. These data show extensive chemical contamination of wildlife in the YRD with a suite of OHCs with both known and unknown toxicities, calling for further in-depth studies.

Arctic rivers deliver~40 t yr⁻¹ of mercury (Hg) to the Arctic Ocean, ~6%of which is from the Mackenzie River Basin(MRB), a region warming at ~3 times the mean hemispheric rate. How this will affect Hg transfer to ecosystems of theBeaufort Sea is a worrying issue. To help address this question, we analyzed >500 measurements ofHg and other waterproperties from 22 rivers collected in 2012–2018 by communities of the MRB. This new dataset provides a more comprehensiveview of riverine Hg variations across the basin than was previously available. We find that rivers issuedfrom mountains in the western MRB contribute the largest share of Hg in the Mackenzie River, 60–95 % of it beingcarried as fine suspended solids and probably sourced from riverbank erosion and thaw slumps. In contrast, lowlandrivers of the central and eastern MRB contribute larger shares of dissolved Hg (up to 78 %), likely from recent atmosphericdeposition through precipitation. Using load modelling constrained by the new water quality dataset, we estimatethat the three largest western tributaries (Liard, Peel and Arctic Red rivers) of the Mackenzie contribute 60 % ofthe annual MRB THg export and DHg export to the Beaufort Sea during freshet, as well as 51 % of DHg export, whilesupplying 60% of freshet discharge. Load modelling also reveals a sustained decline in DHg loads of ~13 kg yr⁻¹ between2001 and 2016 in the lower Mackenzie River, which likely reflect a decreasing trend in atmospheric Hg depositionover most of northwestern Canada during this period. This study highlights the value of community-based waterquality monitoring in helping to support assessments of riverine Hg in theMRB in support of the Minamata Conventionon Mercury.