We studied the key geochemical and mineralogical factors that could affect the fractionation of stable thallium (Tl) isotopes in soil. A set of grassland soil samples enriched in geogenic Tl in ...combination with selected Tl-containing mineral materials from the Czech Republic (Kluky) were investigated for this purpose. The results demonstrate significant incorporation of Tl in pedogenic (specific) Mn-oxide, which led to a large accumulation of the heavy 205Tl isotope (∼+14 ε205Tl units), presumably resulting from oxidative Tl sorption. Consequently, we concluded that the Mn-oxide-controlled Tl uptake is the primary cause of the observed 205Tl enrichment in the middle profile zone, at the A/B soil horizon interface, with up to +4 of ε205Tl. Furthermore, our results displayed a clear relationship between the Tl isotopic fractionation degree and the Mn-oxide soil concentration (R2 = 0.6), as derived from the oxalate-extractable data. A combination of soil and mineralogical considerations suggests that 205Tl enrichment in respective soil samples is also partly due to the Tl present in micaceous clay minerals, mainly illite, which is the predominant pedogenic Tl host phase. In line with our previous results, this Tl behavior can be inferred from systematic Mn-oxide degradation and the associated Tl (enriched in 205Tl) cycling in the studied soils and thus, presumably in the redoximorphic soils in general.
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•Manganese-oxide was found to be the key control for Tl isotopic fractionation.•We identified up to +14 ε205Tl units in pedogenic Mn-oxide nodules.•The soil Mn-oxide concentration affected the Tl isotopic fractionation degree.•Heavy 205Tl isotope enrichment was present at the soil A/B horizon interface.•The heavy 205Tl isotope was probably enriched in illite as well.
Manganese (III,IV)-oxides represent the key control for Tl isotopic fractionation in soil.
Aims
Bacterial communities inhabiting seeds may interact not only with the plant host, but also with seed predators. The study compared the bacterial communities associated with seeds of seven weeds
...Crepis biennis
,
Taraxacum officinale
,
Tripleurospermum inodorum
,
Plantago lanceolata
,
Thlaspi arvense
,
Silene latifolia
and
Leonurus cardiaca
, after burial in soil for two years, and demonstrated how these changes relate to seed mass, viability and attractiveness for a seed predator,
Pseudoophonus rufipes
(DeGeer) (Coleoptera: Carabidae).
Results
Bacterial diversity, assessed by Illumina MiSeq sequencing of the 16S rRNA amplicon, increased 5–10 times, while seed viability and mass decreased with burial time. Mostly, the seed species differed in their microbiomes and changes in seed properties together with their attractiveness to the beetle. Seed microbiomes remained specific after burial and contained taxa characteristic for both plant endophytes but also insect guts. In all seeds, 5 zero radius OTUs (ZOTU) were common after one year of burial, while only one common ZOTU remained after the second year. Seeds of
T. officinale
and
T. inodorum
lost attractiveness for the beetle approx. by 90 and 80% resp., while seeds of
T. arvense
improved their attractiveness by 80% after soil exposure. Changes in seed consumption were partially explained by bacterial communities and seed properties, namely the C/N ratio and seed viability.
Conclusions
Seed mass, viability, C/N and beetle predation were related to the bacterial community. These relationships also changed after seed burial in soil, which may impact seed survival and consequently influence plant population dynamics and weed management.
Here, for the first time, we report the concentrations and isotopic data of Ag in a variety of ore and metallurgical samples and forest soils that have been polluted due to Ag–Pb smelter emissions. ...Similar to the Ag concentrations, we identified a large range of δ109Ag values (from −0.8 to +2.4‰), a ∼3‰ spread, within the primary and secondary materials (i.e., galena, fly ash, slag and matte). This phenomenon, however, is evidently unrelated to Ag isotopic fractionation during the smelting process, but it reflects the starting 109Ag/107Ag signal in ore mineral and/or the specific type of ore genesis. The two studied soil profiles differed in Ag isotopic composition, but on the other hand, they consistently showed significantly lighter Ag (≤+0.8‰) of metallurgical origin in the upper horizons compared to the bottom horizons and bedrocks, with low Ag amounts depleted of 107Ag (≤+2.9‰). This isotopic pattern can be attributed to a ternary mixing relationship involving two major anthropogenic Ag components and a minor contribution from geogenic Ag. Accordingly, we did not observe any post-depositional isotopic fractionation in our soils, since Ag was geochemically stable and it was not subjected to leaching. In summary, the Ag isotopes have a potential to trace variations in anthropogenic phases, to monitor specific geochemical processes, and are clearly applicable as anthropogenic Ag source and Ag load proxies.
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•Silver isotopes are applicable for anthropogenic Ag source/load tracing.•Silver isotopes have a potential to trace variations in anthropogenic phases.•Silver of metallurgical origin is geochemically stable in soils.
The study aimed to estimate and characterise soil organic matter under different land uses (cropland, grassland, and forest) and soil depths. The soil organic matter composition of the soil was ...assessed by diffuse reflectance infrared spectroscopy (DRIFT). Humic and fulvic acids (HAs, FAs) were extracted from soils and their compositions were evaluated by DRIFT. Low molecular mass organic acids content was also measured. Our result revealed that the largest differences of the spectra in the composition of organic matter were observed in the upper parts of the soil profile. The forest soil spectra had more intense aliphatic bands, carboxylic, and CH bands than spectra of grassland and cropland soils. The difference of HAs spectra was at 3 010 to 2 800/cm where the most intensive aliphatic bands were in forest soil HAs, followed by grassland and cropland soil HAs. The grassland topsoil FAs spectrum differs most from the other land uses. It has lower peaks around 1 660–1 600/cm and 1 200/cm than cropland and forest. The concentration of low molecular mass organic acid (LMMOA) was the highest in the forest soil and the most abundant acid was citrate.
Soil organic carbon (SOC) distribution and interaction with light is influenced by soil texture parameters (clay, silt and sand), which makes SOC prediction complicated, especially in samples with ...considerable pedological variability. Hence, understanding the relationship between SOC and soil texture is important within the context of SOC prediction using remote sensing data. The main objective of this study was to find the impact of soil texture on the performance of local SOC prediction models that were developed on Sentinel-2 (S2) multispectral and CASI/SASI (CS) hyperspectral airborne data as the main predictor variables. One approach to that objective was to lowering the texture variance by stratification of the samples. Therefore, soil samples collected from four agricultural sites in the Czech Republic were segregated based on the i) site-based and ii) texture-based stratification strategies. Random forest (RF) models were then developed on all stratified classes with and without considering the soil texture parameters as predictor variables and results were compared with those obtained by the RF models developed on the non-stratified (NS) samples. Both stratification strategies provided more homogeneous classes, which enhanced the accuracy of SOC prediction, compared to using the NS samples. In addition, the texture-based RF models yielded higher accuracy predictions than the site-based ones. Except sand, adding texture parameters to the main predictors improved accuracy of the models, so that the highest prediction performance was obtained by a texture-based model developed on clay added CS data. Overall, texture-based stratification could significantly enhance the SOC prediction, when the texture parameters were added to the S2 and CS data as the main predictor variables.
•Adding texture parameters to remote sensing data was tested on SOC quantification.•Models developed on CS outperformed those developed on S2 data.•Stratification of samples yielded better predictions than using non-stratified ones.•Models developed on texture-based stratified samples were more successful.•Among all texture parameters, adding clay led the best prediction results.
In this study, we report combined Tl isotopic and Tl mineralogical and speciation data from a set of Tl-rich sulfide concentrates and technological wastes from hydrometallurgical Zn extraction. We ...also present the first evaluation of Tl isotopic ratios over a cycle of sulfide processing, from the ore flotation to pyro- and hydrometallurgical stages. The results demonstrate that the prevailing Tl form in all samples is Tl(I), without any preferential incorporation into sulfides or Tl-containing secondary phases, indicating an absence of Tl redox reactions. Although the Tl concentrations varied significantly in the studied samples (~9–280 mg/kg), the overall Tl isotopic variability was small, in the range of −3.1 to −4.4 ± 0.7 (2σ) ε205Tl units. By combining present ε205Tl results with the trends first found for a local roasting plant, it is possible to infer minimum Tl isotopic effects throughout the studied industrial process. As a result, the use of Tl isotopic ratios as a source proxy may be complicated or even impossible in areas with naturally high/extreme Tl background contents. On the other hand, areas with two or more isotopically contrasting Tl sources allow for relatively easy tracing, i.e., in compartments which do not suffer from post-depositional isotopic redistributions.
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•Thallium(I) – a major form in sulfide concentrates and metallurgical wastes.•No redox Tl reactions during sulfide processing, as revealed by XANES.•Overall small Tl isotopic variability (~1 ε205Tl) in the studied samples.•Minimum Tl isotopic effects throughout the industrial process.
Allchar (North Macedonia) mining area is known for anomalous background Tl concentrations. In this study, we combine accurate detection of Tl stable isotope ratios with data on mineralogy/speciation ...and chemical extraction of Tl in Tl-contaminated Technosol profiles. We demonstrate that Tl in the studied soils varies significantly in both concentration (500 mg/kg-18 g/kg) and isotopic composition (−1.6 and +3.2 of ε205Tl, a ∼0.5‰ spread), which is due to changes in the phase chemistry and/or mineralogy of Tl. Moreover, the observed 205Tl/203Tl ratios do not reflect the extent to which individual soils undergo Tl isotopic fractionation during mineral weathering and soil formation. Clearly, they reflect the initial isotopic signal(s) of the primary ore or ore minerals, and thus, the general history or type of their genesis. As the Tl carriers, various types of Tl–Me-arsenates, mixtures of jarosite and dorallcharite and minor Mn-oxides predominated. We revealed intense adsorption of Tl by the identified Mn-oxides (≤6.7 at.%). It is hypothesized that these phases are of key importance in the fractionation of Tl isotopes, meaning at this type of secondary oxide-soil solution interface. However, model studies involving primary/secondary components (sulfides, sulfates, oxides and arsenates) are required to understand the mechanisms that may lead to post-depositional Tl isotopic redistribution in soils, as well as Tl isotope systematics in mining wastes in general.
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•Thallium concentrations in soils are between 500 mg/kg and 18 g/kg.•205Tl/203Tl soil data reflect changes in phase chemistry/mineralogy.•205Tl/203Tl soil data reflect initial isotopic signals related to ore genesis.•205Tl/203Tl soil data do not show post-depositional isotopic fractionation.•Intense Tl uptake by Mn-oxides (≤6.7 at.%).
Vertical profiles of Tl, Pb and Zn concentrations and Tl and Pb isotopic ratios in a contaminated peatland/fen (Wolbrom, Poland) were studied to address questions regarding (i) potential long-term ...immobility of Tl in a peat profile, and (ii) a possible link in Tl isotopic signatures between a Tl source and a peat sample. Both prerequisites are required for using peatlands as archives of atmospheric Tl deposition and Tl isotopic ratios as a source proxy. We demonstrate that Tl is an immobile element in peat with a conservative pattern synonymous to that of Pb, and in contrast to Zn. However, the peat Tl record was more affected by geogenic source(s), as inferred from the calculated element enrichments. The finding further implies that Tl was largely absent from the pre-industrial emissions (>~250 years BP). The measured variations in Tl isotopic ratios in respective peat samples suggest a consistency with anthropogenic Tl (ε205Tl between ~ -3 and −4), as well as with background Tl isotopic values in the study area (ε205Tl between ~0 and −1), in line with detected 206Pb/207Pb ratios (1.16–1.19). Therefore, we propose that peatlands can be used for monitoring trends in Tl deposition and that Tl isotopic ratios can serve to distinguish its origin(s). However, given that the studied fen has a particularly complicated geochemistry (attributed to significant environmental changes in its history), it seems that ombrotrophic peatlands could be better suited for this type of Tl research.
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•Thallium is immobile in peat, comparable to Pb.•The thallium record in a peat column reflects historical Tl deposition.•Thallium isotopic signatures are applicable for tracing Tl sources in peatlands.
This study focuses on the effect of agricultural soil management on soil organic matter (SOM) composition. The addition of manure and crop residues was tested under different pedoclimatic conditions. ...The quality of SOM was assessed using diffuse reflectance infrared spectroscopy. The following parameters were calculated from the spectra: sum of aliphatic bands (ΣAL), aromatic bands at wave numbers 1 620 and 1 520 cm-1 (AR1620 and AR1520), potential wettability (PWI), organic matter quality (OMQ), and decomposability (DI) indexes. The addition of manure or crop residues may not cause fundamental changes in the qualitative composition of SOM. Rather, pedoclimatic conditions determine which components are fixed in the soil on a long-term scale. A dominant effect of soil type was found in the distribution of all spectral parameters studied using main effect ANOVA. The main differences between the soil types concern the aromatic, oxygen and nitrogen groups contained in the SOM. Chernozems are soils with higher OMQ and DI, whereas Cambisols are soils with low OMQ and DI and the highest PWI. The stabilisation of SOM in soils can thus be based on the biochemical persistence of organic molecules, their specific affinity for minerals and the formation of aggregates that protect enclosed SOM.
Weathering of Tl-containing sulfides in a model (12-week) peat pot trial was studied to better understand their geochemical stability, dissolution kinetics, alteration products and the associated ...release and mobility of anthropogenic Tl in organic environments. We also present the effect of industrial acid rainwater on sulfide degradation and Tl migration in naturally acidic peat. Sphalerite (ZnS) was much less stable in peat than other Tl-containing sulfides (galena and pyrite), and thus acted as a major phase responsible for Tl mobilization. Furthermore, Tl incongruently leached out over Zn from ZnS, and accumulated considerably more in the peat solutions (≤5 μg Tl/L) and the peat samples (≤0.4 mg Tl/kg) that were subjected to acid rain watering compared to a deionized H2O regime. This finding was in good agreement with the absence of secondary Tl-containing phases, which could potentially control the Tl flux into the peat. The behavior of Tl was not as conservative as Pb throughout the trial, since a higher peat mobility and migration potential of Tl was observed compared to Pb. In conclusion, industrial acid precipitations can significantly affect the stability of ZnS even in acidic peat/organic environments, making it susceptible to enhanced weathering and Tl release in the long term.
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•Sphalerite is less stable in peat as compared to other sulfides.•Sphalerite, a major phase controlling the Tl flux into peat.•Thallium showed a higher mobility and migration potential than Pb.•Industrial acid precipitations can accelerate ZnS weathering and Tl release.
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