This study evaluates the influence of digestion methods on metal concentrations and results of isotopic analysis of dusts generated during electronic waste processing. E-waste dusts were collected from processing units such as photovoltaic panels, LCD and CRT monitors, and mixed e-waste. Following methods were used for digestion: i) aqua regia with a temperature pretreatment at 110 degrees C, ii) concentrated acids (HClO4, HF, HNO3) with a temperature pretreatment at 550 degrees C. Results showed that concentrated acids with 550 degrees C pretreatment generally yielded significantly higher recoveries for most elements (e.g., Ag, Al, Ba, K, Na, Pb). Conversely, aqua regia was more efficient for Sn recovery, as the higher temperature used with concentrated acids led to the formation of volatile SnCl4 and subsequent Sn loss. A significant Pb isotopic shift was observed between the two methods in glass-rich samples, indicating that aqua regia leached readily available Pb, while concentrated acids (mostly HF) released Pb (of different origin) incorporated within the glass. The isotopic analyses revealed consistent S66/64Zn (-0.078 to 0.052) and S65/63Cu values (0.170 to 0.313) across both methods. Slight changes in S66/64Zn and S114/ 110Cd values were attributed to sample heterogeneity, origin or phase changes after higher temperature treatment at 550 degrees C. A distinct Cu isotopic signature (S65/63Cu 0.067 and 0.078) in CRT dust suggests a different historical origin of Cu in older devices. These findings highlight the crucial role of selecting a digestion method that is appropriate for the specific e-waste dust, to ensure accurate elemental and isotopic analysis.

Estimates of atmospheric inputs of reactive nitrogen (Nr) into ecosystems are often based on vertical deposition. We investigated to what extent horizontal deposition affects total atmospheric deposition of Nr in two sparsely populated mountain regions near the Czech-German-Polish borders in an era of easing pollution. Among three scenarios of horizontal-water contribution to rainfall (additional 5, 10 and 20%), the 10% scenario was considered the most realistic. Between 2023 and 2025, wet horizontal deposition of NH4+-N plus NO3--N constituted as much as 66-77% of total wet inorganic Nr deposition. Because condensation of rain and fog droplets occurs at different altitudes, we hypothesized that the Nr-source mix in horizontal and vertical deposition would differ. N-isotope analyses and Bayesian modeling indicated larger dominance (up to 75%) of vehicle-exhaust derived NH4+-N in fog than in rain. In contrast, the mix of NO3--N sources for fog and rain was nearly identical, with average contributions of six sources making up 9-24% each. Remote large NOx sources originating in coal-burning powerplants and natural-gas burning industries played similarly weak roles as more local and/or diffuse sources related to residential coal and wood burning, traffic and biogenic/soil emissions.

This study combines Cd, Pb, and Zn isotopes and BCR extraction to evaluate trace metal mobility and environmental risks in dust from e-waste facilities. Eight samples were collected by active aspiration from units processing: photovoltaic panels, liquid crystal display (LCD), cathode ray tube (CRT) monitors, and mixed e-waste. One storage facility (SF) floor dust was swept. Trace element concentrations were determined and maximum concentrations reached 1095 mg kg⁻¹ Cd, 23107 mg kg⁻¹ Cu, 25454 mg kg⁻¹ Pb, 31082 mg kg⁻¹ Zn, 806 mg kg⁻¹ Sb, and 9365 mg kg⁻¹ Ba. A modified BCR sequential extraction procedure characterized five fractions: exchangeable (F1), reducible (F2), organic-bound (F3), and two residual (F4, F5). Zinc showed the highest mobility (71-98% in F1 and F2 fractions), while copper showed variable behavior depending on e-waste type. Cadmium and lead mobility strongly depended on e-waste type: 93-95% of Cd and 64-85% of Pb were highly mobile in mixed e-waste dusts, but remained predominantly in residual fractions for CRT, LCD, and SF dusts. Less mobile elements (Ba, Sb, As, Cr) remained in least accessible fractions. Isotopic analysis identified three distinct Pb source clusters. Zinc and cadmium isotopes ranged from light isotope enrichment in early fractions to heavy isotope enrichment in residual phases, reflecting both primary source signatures and extraction-induced fractionation. Mixed e-waste dusts pose the highest environmental concern due to high Zn, Cu, Cd, and Li concentrations and mobility. CRT, SF, and LCD dusts present lower immediate risk due to glass/ceramic matrix incorporation, but long-term monitoring remains essential.

In many countries worldwide, NOx emissions currently decrease as a result of pollution control, while NH3 emissions stagnate or continue to increase. Little is known about horizontal deposition of NO3− and NH4+, the oxidation/neutralization products of these primary pollutants. To close the knowledge gap, we studied atmospheric inputs of NO3− and NH4+ at two mountain-top sites near the Czech–German–Polish borders during winter. Horizontal deposition via ice accretions (rime) made up 26–30 % of total atmospheric input of reactive nitrogen (Nr). Such high horizontal depositions should not be neglected in ecosystem N studies which currently often consider only vertical deposition via snow. Snow nitrate N was the largest type of Nr deposition (40–52 %), with snow ammonium N being the second largest (20–30 %). Rime ammonium N contributed a similar amount to total Nr input as rime nitrate N (12–16 %). The total inorganic Nr deposition was 4–6 kg ha−1 winter−1. Across the sites, the mean δ15NNH4+ and δ15NNO3− values fell in a relatively narrow range from −3.1 to −7.3 ‰. Three systematic isotope patterns were observed: (i) NH4+-N was always heavier in rime than in snow, (ii) NO3−-N was always heavier in rime than in snow, and (iii) NO3−-N was always heavier than NH4+-N. For source apportionment, the Bayesian isotope mixing model SIMMR was used. Counter-intuitively, vehicles were larger sources of NH3 in rime than volatilation from animal waste plus fertilizers (46 vs. 19 %). The largest NO3− contributions to rime were derived from vehicles and biomass burning, followed by natural gas combustion and coal burning in power plants and households. Natural gas represented the largest source of nitrate in snow. Nitrate sources appeared to be better-mixed than ammonium sources. Our isotope-based source apportionment differed from national emission inventories, offering original insights into local atmospheric Nr inputs.

The selection of decomposition method and processing of samples are crucial for precise analytical measurements. We selected three waste samples originating from different industrial activities and one raw material (ewaste dust, fly ash, slag, coal). Especially e-waste dust is a unique material with very distinctive composition that requires a specific approach in terms of sample preparation and decomposition. Samples were thermally treated at 110, 550, 1050 degrees C and subsequently decomposed using different methods: i) aqua regia, ii) concentrated acids (HNO3, HClO4, HF), iii) alkaline fusion. Temperature treatment at 1050 degrees C resulted in the formation of difficultto-decompose phases in samples with high organic matter content (e-waste dust, coal) associated with incomplete decomposition by aqua regia and changes in isotopic composition (e-waste dust: Delta 114/110Cd1050-110 degrees C = -0.110, Delta 65/63Cu1050-110 degrees C = -0.776, Delta 66/64Zn1050-110 degrees C = -0.089; coal: Delta 114/110Cd1050-110 degrees C = 0.672, Delta 65/ 63Cu1050-110 degrees C = 0.558, Delta 66/64Zn1050-110 degrees C = -0.110). Another effect observed after temperature treatment at 1050 degrees C was the analytical loss caused by the thermal decomposition of volatile components present in the fly ash. The analytical loss (up to 98.5 % Cd, 98.7 % Cu, 99.7 % Pb, 57.4 % Zn) was linked with significant Cd and Zn isotopic changes (Delta 114/110Cd1050-110 degrees C up to 0.873, Delta 66/64Zn1050-110 degrees C up to 0.238). The changes in Cu isotopic composition in fly ash caused by thermal decomposition were also recorded after processing at 550 degrees C (Delta 65/ 63Cu550-110 degrees C was 0.154). The results clearly show that the origin of the sample and different decomposition methods, together with temperature pretreatment, have a significant effect on results of concentration and isotopic measurements.

Knowledge of relative importance of Pb sources is a prerequisite of developing strategies that would decrease atmospheric pollution by this highly toxic metal. In the industrial city of Ostrava (Czech Republic, Central Europe), we identified nine major Pb pollution sources and isotopically studied air-borne Pb at five sites along a SW-NE transect. Site 3 in the central city, situated close to a Fe-metallurgical operation, was characterized by six times higher winter-time Pb content in PM10, compared to less industrial sites 1, 2, 4 and 5. The Bayesian model MixSIAR estimated decreasing contributions of sources to air-borne Pb in the order: unleaded fuel plus tire wear > Mississippi-Valley type ores > Variscan ores > stone coal > soft coal > Fe-ore > brake wear > legacy leaded gasoline. Individual contributions decreased from ∼29 % to ∼5 %. Winter-time coal incineration in households and thermal power plants resulted in a seasonality in Pb emission rates. We infer that the model may underestimate the role of stone coal burning, possibly due to its time-dependent 206Pb/207Pb and 208Pb/207Pb isotope signatures. Also, the isotope signatures of Pb released into the air during coke production and its consumption during the Fe metallurgy process may have varied over time. Reducing coal incineration in households using obsolete boilers becomes a priority among measures to improve air quality in the Ostrava conurbation.

This study presents an integrated hydrological-hydrochemical approach to quantify reactive nitrogen (N-R) cycling in temperate mountain catchments. It employs stable isotope analyses (delta H-2, delta O-18 in water, delta N-15 in NH4+, and NO3- and delta O-18 in NO3-) to resolve interactions between water flow and N transformations. A two-component runoff model reveals groundwater as the dominant discharge contribution (75%-90%), with 10%-25% derived from rapidly infiltrating soil water-highlighting a swift hydrological response to precipitation. In addition, this work quantifies all N mineralization in vadose zone and denitrification in groundwater and their seasonal variation within a well-studied network of N-saturated temperate forests (i.e., the Czech GEOMON Network). Our results show that increased precipitation infiltration diminishes microbial N production and N-2 losses, but maximizes catchment N-R exports. Direct input of atmospheric N-R to runoff was recorded during a short period of spring snow melting only. Denitrification calculated from N-15 fractionation of NO3- in soil and groundwater accounts for 15%-24% of total mineralized N (N loss is 0.6-1.6 kg N ha(-1) year(-1)), with precipitation shifts markedly influencing N-R outflows. This framework enhances predictions of climate change impacts on nutrient transport and water quality in mountain catchments, which are critical water sources for ecosystems and human use. Overall, application of this approach can offer key insights for mitigating ecological risks from increased N-R mobilization, especially under rising atmospheric N deposition and global warming effects.

Quantification of geogenic inputs of magnesium (Mg) and calcium (Ca) as essential nutrients, and strontium (Sr) as a Ca proxy, into biomass and catchment runoff is indispensable for studies of forest sustainability in an era of persisting acidification and climatic change. Supergene processes control the isotope composition of base cations released from bedrock into solution. Isotope signatures of dissolved Mg2+, Ca2+ and Sr2+ are complementary to the isotope composition of weathered rock because both are derived from the same parent material. We investigated shifts in S26Mg, S44Ca, and 87Sr/86Sr isotope ratios from fresh bedrock toward the weathering front in six common crystalline lithologies, including leucocratic granite, quartz diorite, melasyenite, melagranite, augen gneiss and amphibolite. About 20 cm below the deepest soil horizon, the isotopic composition of Mg, Ca and Sr in weathered rock differed significantly from that of fresh rock in nine out of 18 cases. Bulk-rock S26Mg and S44Ca values were less sensitive to partial dissolution of minerals than 87Sr/86Sr ratios. Statistically significant shifts in 87Sr/86Sr were observed in all six lithologies. Weathered rock had higher 87Sr/86Sr ratios than fresh rock in three cases, and lower 87Sr/86Sr ratios in another three cases. The site-specific 87Sr/86Sr shift was explained by contrasting weathering rates of Rb-rich and Rb-poor minerals in most rocks. Both lower S26Mg and higher S44Ca values of weathered amphibolite were likely related to isotope fractionations accompanying in-situ formation of secondary smectite. Continuing mineral dissolution in overlaying soils may cause additional Mg, Ca and Sr isotope effects.

Changes in organic matter accumulation in wetlands are critical for climate dynamics. Different nitrogen (N) inputs in Sphagnum-dominated peat bogs can lead to varying rates of carbon (C) and N accumulation, influencing greenhouse gas emissions. We investigated how contrasting N deposition shapes microbial communities in two Czech peat bogs, focusing on biological N2 fixation (BNF) as a key N input in pristine wetlands. Higher N deposition resulted in a more active microbial community with increased enzyme activity and C acquisition, potentially accelerating decomposition and reducing C storage. Enhanced denitrification, indicated by active nosZ Clade I genes, suggests that higher N inputs may increase N losses through denitrification. In contrast, the lower N site showed a less active microbial community with slower decomposition, beneficial for C sequestration, though potentially less adaptable to future N increases. Experimental BNF rates were 70 times higher at the high N site, consistent with elevated diazotroph activity indicated by active nifH gene. Phosphorus (P) availability and NH4+/NO3− ratios appeared to drive BNF differences, emphasizing the need for managed N inputs to maintain peatland ecological functions.

Microbial N2-fixation helps to sustain carbon accumulation in pristine peatlands and to remove CO2 from the atmosphere. Recent work has provided evidence that this energetically costly process is not completely downregulated at sites with higher availability of reactive nitrogen (Nr). We studied nitrogen (N) cycling at three high-elevation, mainly rain-fed, Sphagnum-dominated peat bogs in the northern Czech Republic receiving medium to high amounts of reactive nitrogen (Nr) via atmospheric deposition. 15N/14N isotope ratios were determined in Nr deposition, along vertical peat profiles, and in a laboratory incubation study using fresh Sphagnum and 15N-enriched atmospheric N2. Our objective was to assess the potential for biological N2-fixation at the selected study sites in light of various biogeochemical parameters. Historically, all the peat bogs experienced similar changes in atmospheric Nr (mainly NO3--N and NH4-N) inputs. Nr depositions at all three sites peaked between 1980 and 1990. During that time period, the highest annual depositions were close to 10 kg ha-1 yr-1 at the slightly more polluted site Uhlirska (UHL) than at Male mechove jezirko (MMJ) and Brumiste (BRU). Since ca. 1990, atmospheric deposition of Nr has been steadily decreasing. Living Sphagnum had variable N concentrations with similar means for all three sites (1.1, 1.0 and 0.9 wt. % at MMJ, BRU and UHL, respectively). Downcore, peat density remained nearly constant at MMJ but increased at BRU and UHL. Ash contents were below 10 wt. % at least to the depth of 20 cm. With an increasing peat depth, both N concentration and δ15N values generally increased, while C/N ratios tended to decrease. At depths > 10 cm, N/P ratio was lower at UHL than at the other two sites and remained nearly constant downcore. N/P ratio at MMJ increased from ~10 to ~20 with an increasing depth, whereas the N/P ratio exhibited a zigzag vertical pattern at BRU, reaching a value of 40 in deeper segments. The potential for biological N2-fixation was investigated using a replicated laboratory incubation of fresh Sphagnum in a closed system following an application of 98 % enriched atmospheric N2. The experiment lasted for 7 days. The control Sphagnum samples had δ15N values of -4.0 ‰ (BRU and UHL) and -3.7 ‰ (MMJ). At the end of the incubation, the δ15N significantly increased only in MMJ moss reaching + 70 ‰, while it remained unchanged in BRU and UHL moss. Biological N2 fixation was thus recorded at only at MMJ, a site with the lowest N/P ratio in the topmost 2-cm thick sections. Potential N2 fixation rates at MMJ were similar to values previously reported for Finland (Leppänen et al. 2015) but ~7 times lower than at sites located in Patagonia, Chile (Knorr et al. 2016). References Leppänen et al., 2015. Plant and Soil, 389, 185-196. Knorr et al., 2016, Global Change Biology 21, 2357–2365.

The city of Ostrava, NE Czech Republic, is known for its industrial pollution. It has well-characterized emission sources and stable air movement patterns. These features are conveniently used to generalize on atmospheric NOx and SO2 oxidation processes. In 2021, we conducted a series of sampling campaigns to assess the isotopic fractionation conducive to NO3and SO42aerosols in PM10. These sampling campaigns were timed to capture varying atmospheric conditions, including climatic inversion periods, providing also insights into urban emission dynamics over the course of the year. Gaseous NOx and SO2 were collected on passive filters, while their oxidized forms, NO3and SO42, were captured on PM10 particle filters, enabling us to analyze the transformation dynamics of these pollutants. Isotopic analyses distinguished the sources of NOx emissions-coal combustion (delta 15N =3 parts per thousand) and vehicular emissions (delta 15N = 7 parts per thousand)-and allowed quantifying isotope fractionation during their conversion to NO3(epsilon NOx-NO3- =11.5 +/- 1.15 parts per thousand). This fractionation, however, was influenced by seasonal vari-ations, and appears to be notably affected by NH4NO3 decomposition during warmer months. The correlation of the NO3to NOx ratio with PM10 and atmospheric moisture highlighted the interplay between particulate matter and humidity in relevant atmospheric transformations. Similarly, for SO2, primarily emitted from coal com-bustion (delta 34S =2 parts per thousand), we identified distinct fractionation patterns during oxidation to SO42encompassing both kinetic (epsilon SO2-H2O =1.3 +/- 0.5 parts per thousand) and equilibrium (epsilon SO2- SO42- =2.24 +/- 0.67 parts per thousand) effects. The SO42/SO2 ratio was correlated with PM10 but showed no dependence on humidity. Significantly, atmospheric inversion conditions accelerated oxidation, modifying the fractionation patterns for both NOx (epsilon NOx-NO3- =7 parts per thousand) and SO2 (epsilon SO2- SO42-=0.9 +/- 0.3 parts per thousand). Our methodology elucidates pivotal mechanisms in atmospheric pollution transformation, underlined by the tracing of NOx and SO2 to aerosol conversions via delta 15N and delta 34S isotopic analyses. The isotope fractionation underscores equilibrium processes in oxidation reactions, while the effect of PM10 and humidity reveals the complexity of these atmospheric oxidative transformations. The role of wet deposition in removing SO2 highlights an essential pathway in the atmospheric sulfur cycle

A Central European catchment underlain by base-poor orthogneiss was studied using mass budgets and Mg–Ca–Sr isotope systematics. For 50 years, the catchment received large amounts of partly soluble dust from a nearby cluster of coal-burning power plants, while suffering from acid rain and severe spruce die-back. Our objective was to investigate to what extent anthropogenic dust contributes to Mg and Ca in runoff and to identify fractionations affecting Mg and Ca isotope composition of 13 ecosystem pools and fluxes. We hypothesized that if Mg and Ca runoff fluxes were significantly larger than their atmospheric inputs, Mg and Ca isotope ratios in runoff would converge to those of bedrock Mg and Ca. This relationship could be obscured by isotope fractionations. Strontium characterized by negligible isotope fractionations served as a Ca proxy. There was a strong positive correlation between Mg and Ca fluxes via spruce throughfall and catchment runoff. Monitoring of rainfall, canopy throughfall and runoff fluxes revealed a 20-, 15- and 15-fold excess of Mg, Ca and Sr in runoff, respectively, compared to atmospheric deposition fluxes. This sizeable excess per se would indicate predominance of geogenic base cations in runoff. The behavior of Mg and Ca isotopes was de-coupled. Petrographic study indicated that 92

Nutrient imbalances may negatively affect the health status of forests exposed to multiple stress factors, including drought and bark beetle calamities. We studied the origin of base cations in runoff from a small Carpathian catchment underlain by base-poor flysch turbidites using magnesium (Mg), calcium (Ca) and strontium (Sr) isotope composition of 10 ecosystem compartments. Our objective was to constrain conclusions drawn from long-term hydrochemical monitoring of inputs and outputs. Annual export of Mg, Ca and Sr exceeds 5-to-15 times their atmospheric input. Mass budgets per se thus indicate sizeable net leaching of Mg, Ca and Sr from bedrock sandstones and claystones. Surprisingly, δ26Mg, δ44Ca and 87Sr/86Sr isotope ratios of runoff were practically identical to those of atmospheric deposition and soil water but significantly different from bedrock isotope ratios. We did not find any carbonates in the studied area as a hypothetical, easily dissolvable source of base cations whose isotope composition might corroborate the predominance of geogenic base cations in the runoff. Marine carbonates typically have lower δ26 Mg and 87Sr/86Sr ratios, and silicate sediments often have higher δ26Mg and 87Sr/86Sr ratios than runoff at the study site. Mixing of these two sources, if confirmed, could reconcile the flux and isotope data.

In many countries worldwide, NOx emissions currently decrease as a result of pollution control, while NH3 emissions stagnate or continue to increase. Little is known about horizontal deposition of NO3- and NH4+, the oxidation/neutralization products of these primary pollutants. To close the knowledge gap, we studied atmospheric inputs of NO3- and NH4+ at two mountain-top sites near the Czech-German-Polish borders during winter. Horizontal deposition via ice accretions (rime) made up 26-30 % of total atmospheric input of reactive nitrogen (Nr). Such high horizontal depositions should not be neglected in ecosystem N studies which currently often consider only vertical deposition via snow. Snow nitrate N was the largest type of Nr deposition (40-52 %), with snow ammonium N being the second largest (20-30 %). Rime ammonium N contributed a similar amount to total Nr input as rime nitrate N (12-16 %). The total inorganic Nr deposition was 4-6 kg ha-1 winter-1. Across the sites, the mean δ15 N NH 4 + and δ15 N NO 3 − values fell in a relatively narrow range from -3.1 to -7.3 ‰. Three systematic isotope patterns were observed: (i) NH4+-N was always heavier in rime than in snow, (ii) NO3--N was always heavier in rime than in snow, and (iii) NO3--N was always heavier than NH4+-N. For source apportionment, the Bayesian isotope mixing model SIMMR was used. Counter-intuitively, vehicles were larger sources of NH3 in rime than volatilation from animal waste plus fertilizers (46 vs. 19 %). The largest NO3- contributions to rime were derived from vehicles and biomass burning, followed by natural gas combustion and coal burning in power plants and households. Natural gas represented the largest source of nitrate in snow. Nitrate sources appeared to be better-mixed than ammonium sources. Our isotope-based source apportionment differed from national emission inventories, offering original insights into local atmospheric Nr inputs.

Knowledge of the origin of magnesium (Mg) and calcium (Ca) in soil solutions and catchment runoff helps to predict forest ecosystems’ vulnerability to deficiencies in essential nutrients in an era of climate change, environmental pollution and bark-beetle calamities. Here we discuss isotope aspects of Mg, Ca and strontium (Sr) cycling in a spruce-forested headwater catchment in a relatively unpolluted part of Central Europe. We investigated to what extent Mg and Ca isotope signatures of runoff reflect the isotope compositions of specific Mg- and Ca-rich minerals that easily dissolve during the weathering of paragneiss, and compared the isotope variability of Mg and Ca in fresh bedrock minerals, soils and other ecosystem reservoirs. We also compared conclusions from Mg and Ca isotope systematics with inferences from catchment input–output mass budgets. Long-term input–output monitoring in the studied catchment situated near the Czech–German border (Central Europe) revealed 3.5–7 times higher outputs of Mg, Ca, and Sr via surface runoff relative to their present-day atmospheric inputs. It follows that hydrological exports of recent atmospheric Mg, Ca and Sr are minor. Release of geogenic base cations into the runoff results from the interplay between mineral abundances, concentrations of the studied elements in the minerals, and their dissolution rates. Chemical depletion fractions for the studied elements from bedrock to the soil were 50–70 %, and the losses of dominant soluble minerals in the soil were 30–80 %. Exports of residual Mg, Ca and Sr following partial incorporation of these elements into secondary phyllosilicates are probably low because newly-formed clay minerals are not abundant in the soil. Residual Ca following preferential incorporation of isotopically light Ca into growing tree biomass may contribute to the isotopically heavy runoff Ca. Isotope ratios of base cations were obtained for six minerals (plagioclase, orthoclase, biotite, muscovite, apatite, and ilmenite). Mineral fractions differ greatly in δ26Mg and δ44Ca values and 87Sr/86Sr ratios. 80–97 % of each of the three studied base cations are present in the bedrock in a single relatively easily dissolvable mineral: Mg in biotite, and Ca and Sr in plagioclase. The isotope composition of Mg in biotite was similar to the isotope composition of Mg in runoff. The isotope compositions of Ca and Sr in plagioclase were also similar to Ca and Sr isotope compositions in runoff. Thus, the dominant geogenic source of each of the studied elements (Mg, Ca and Sr) in the investigated paragneiss catchment can be represented by one relatively soluble mineral.

Rime is an under-researched pathway of the atmospheric deposition of ecological and environmental relevance, in particular in mountain regions. Rime alongside with snow were sampled and assessed for S-SO42- and N-NO3- at ten border mountaintop sites across the Czech Republic (CR) in the three consecutive winters of 2009–2011. Our observations indicated significantly higher sulphur (S) and nitrogen (N) contents in rime as compared to snow at all sites. Whereas the highest S contamination was found in the industrial North, the highest N contamination was found unexpectedly in the relatively unpolluted South. The measurements were put in context with data driven geo-spatial modeling results (Hůnová et al., 2016) of annual wet vertical (rain and snow) and horizontal (fog and rime) deposition. Despite relatively low hydrological input of rime, it contributed significantly to annual atmospheric deposition. At nine out of ten sites, the winter-time deposition of S via rime corresponded to 5–13% of annual wet-only S deposition, while it reached full 25% at the most S-polluted TET site in the Orlicke hory Mts., a region bordering Poland (Hůnová et al., 2022). Modelled results showed that mean winter rime deposition corresponded to about 6–25%, and mean winter snow deposition made up 25–72.5% of mean annual N-NO3- wet-only deposition (Hůnová et al., submitted). Model N-NO3-occult deposition estimated from throughfall and total (wet and dry) deposition is highly uncertain, however: N throughfall is not a relevant proxy for estimation of realistic total N deposition due to N exchange between the tree canopy and atmosphere. Considering the fact that wet-only deposition is a year-long phenomenon, whereas rime forms under the climatological conditions of the Czech middle elevated mountains during only a few (2–3) months a year, we can conclude that the rime deposition pathway should not be neglected in quantifying the real atmospheric deposition flux in mountain regions as it might contribute to the real deposition flux substantially even in mountains of medium elevation, as was observed in the CR.References:Hůnová I., Kurfürst P., Vlček O., Stráník V., Stoklasová P., Schovánková J., Srbová D., 2016. Towards a Better Spatial Quantification of Nitrogen Deposition: A Case Study for Czech Forests. Environmental Pollution 213, 1028–1041. doi: 10.1016/j.envpol.2016.01.061.Hůnová I., Novák M., Kurfürst P., et al., 2022. Contribution of rime to atmospheric sulphur deposition in Central Europe: A combined empirical and modelling approach. Atmospheric Environment 270, 118877. https://doi.org/10.1016/j.atmosenv.2021.118877.Hůnová I., Novák M., Kurfürst P., et al., submitted. Comparison of vertical and horizontal atmospheric deposition of nitrate at Central European mountain-top sites during three consecutive winters.

The sources of airborne particulate matter (PM10) emissions in Ostrava, Czech Republic, were investigated. Emphasis was placed on their organic carbon (OC) and elemental carbon (EC) contents, and their carbon stable isotope composition, 813C. Emission sources were identified using OC-613C and concentration values. To track the extent of long-term deposition, these sources were also identified using the black carbon (BC) 613C values of soil samples. At all sampling sites, wind flow is predominantly (65-80%) bidirectional in either SW-NE or NE-SW trajectories. Source apportionment along these dominant airflow trajectories was calculated from an isotopic 13C mass balance, and according to differences in the OC content and 613C values of PM10. Determined emission sources are: (i) combustion of Silesian hard coal (813C =-24.5%o); (ii) local Ostrava coal combustion (613C =-25.5 to-26%o), automotive emissions (613C =-26.5%o), and biogenic particles (613C =-28 to-28.5%o). Winter emissions (mean OC concentrations from 12 to 25 mu gm- 3) originated mostly from coal combustion (80%) in domestic and industrial point sources. Differences were ascribed to automotive emissions. Ostrava is located near the Czech-Polish border, transboundary emissions are transported under a southbound wind flow that transported from 40 to 80% of the collected PM10. Summer emissions were lower (mean OC concentration from 6 to 8 mu g m-3). Automotive emissions accounted for up to 40%, whilst biogenic production accounted for 60%. Absence of 13C isotope data of secondary OC (SOC 1.2-1.5 mu gm- 3) increases uncertainty in our source apportionment in summer; when SOC could comprise >20% of total OC. Contribution of SOC to the winter-measured OC is much lower (5-10%), and has no significant effect on mass balances. The upper soil layer analyses revealed long-term deposition of the same emissions sources. We conclude that the stable delta 13C isotope values of OC and EC are useful for discriminating against local sources of PM10 pollution in relatively small urban areas, containing discrete polluting sources. Such a simplified approach can be easily standardized and implemented to manage regulatory compliances in the increasingly commoditized carbon offset market.