Uticaj različitih redoks uslova na (i)mobilizaciju talijuma u zemljište (Srbija)

Thallium (Tl) is a highly toxic element, even in small concentrations, to a range of organisms and in different environments. Therefore, our aim was to study (i) Tl geochemical fractionation by the means of the modified BCR sequential extraction procedure and (ii) the impact of redox potential (EH) alteration and principal factors such as iron (Fe), manganese (Mn), dissolved organic carbon (DOC), chlorides (Cl) and sulfates (SO4 2) on Tl (im)mobilization in periodically flooded arable soil (Serbia). Flooding was simulated using an automated biogeochemical microcosm system that allows systematical control of pre-defined redox-windows. Afterwards, EH was increased stepwise for approximately 100 mV from reducing (-205 mV) to oxidizing (530 mV) conditions. EH was automatically monitored at 10 minutes intervals. Total duration of the experiment was 914 hours. The sequential extraction revealed majority of pseudo-total soil Tl (0.15 mg kg-1 ) in the residual fraction (85.5 %), following by reducible (10.2 %), oxidable (3.8 %) and acid soluble (exchangeable) (0.5 %) fraction. The soluble Tl concentrations (0.024-0.116 μg l-1 ) were significantly affected by EH, having an increase with EH increase (r=0.75, p lt 0.01, n=30). Concentrations of soluble Fe, Mn, and Doc showed significant negative correlations with soluble Tl (r=-0.78, r=-0.73 and r=-0.91, respectively, p lt 0.01, n=30), whereas Tl correlated significant positive with SO42and Cl(r=0.89, r=0.81, respectively, p lt 0.01, n=30). Thallium mobilization was attributed to several simultaneous processes, involving the reductive dissolution of Fe-Mn oxides and gradual oxidation of Tl-bearing metallic sulfides. Our results imply that soluble Tl concentrations might increase when soil redox status evolves from reducing to oxidizing conditions. Due to high Tl toxicity at low doses, and increasing flooding events, our findings suggest that Tl should be included in future monitoring of plants and groundwater on the site or on similar sites.Talijum je veoma toksičan element i u niskim koncentracijama za razne organizme u okviru različitih delova životne sredine. Cilj rada bio je da se ispita (i) sadržaj talijuma u hemijskim frakcijama u zemljištu po modifikovanoj BCR proceduri i (ii) uticaj redoks potencijala (EH) i glavnih faktora, kao što su gvožđe (Fe), mangan (Mn), rastvorljiv organski ugljenik (DOC), hloridi (Cl -) i sulfati (SO4 2-) na (i)mobilizaciju talijuma u povremeno plavljenom obradivom zemljište (Srbija). Plavljenje zemljište je simulirano u laboratorijskim uslovima, uz korišćenje automatskog biogeohemijskog zatvorenog sistema koji dozvoljava sistematsku kontrolu definisanih redoks uslova. Nakon toga, redoks potencijal zemljište je postepeno povećavan u okvirima od po 100 mV od redukcionih (-205 mV) do oksidacionih (530 mV) uslova. Redoks potencijal je automatski meren u intervalima od 10 minuta. Ukupno vreme trajanja ogleda je bilo 914 sati. Hemijska frakcionacija je pokazala da se najveći deo ukupnog talijuma (0,15 mg kg -1) nalazi u rezidualnoj frakciji (85,5 %), a zatim u redukujućoj (10,2 %), oksidujućoj (3,8 %) i frakciji izmenljivo adsorbovanih elemenata (0,5 %). Redoks potencijal je značajno uticao na sadržaj rastvorljivog talijuma (0.024-0.116 μg l -1), koji se povećavao sa njegovim povećanjem (r=0.75, p lt 0.01, n=30). Rastvorljivi sadržaji Fe, Mn, i Doc su pokazali značajnu negativnu korelaciju sa rastvorljivim sadržajem Tl (r=-0.78, r=-0.73 i r=-0.91, redom, p lt 0.01, n=30), dok su utvržene značajne pozitivne korelacije između Tl i sulfata i hlorida (r=0.89, r=0.81, p lt 0.01, n=30). Mobilizacija talijuma može se dovesti u vezu sa nekoliko procesa koji se istovremeno odvijaju, a to su, između ostalih, rastvaranje Fe-i Mn-oksida u oksidacionim uslovima i postepena oksidacija metalnih sulfida koji sadrže Tl. Naša istraživanja ukazuju da sadržaji rastvorljivog Tl mogu da se povećavaju u kada se redoks potencijal menja od redukcionih ka oksidacionim uslovima. Naša istraživanja upućuju na neophodnost sistematskog praćenja sadržaja Tl u biljkama i podzemnim vodama, s obzirom na njegovu visoku toksičnost u niskim dozama, kao i učestalu pojavu plavljenja obradivih zemljišta

Metal uptake and distribution in the zebrafish (Danio rerio) embryo: differences between nanoparticles and metal ions

Quantitative data on nanoparticle and cation uptake are compared in a compartment-specific way and distinct differences between metals were identified

Microbial and Chemical Characterization of Underwater Fresh Water Springs in the Dead Sea

Due to its extreme salinity and high Mg concentration the Dead Sea is characterized by a very low density of cells most of which are Archaea. We discovered several underwater fresh to brackish water springs in the Dead Sea harboring dense microbial communities. We provide the first characterization of these communities, discuss their possible origin, hydrochemical environment, energetic resources and the putative biogeochemical pathways they are mediating. Pyrosequencing of the 16S rRNA gene and community fingerprinting methods showed that the spring community originates from the Dead Sea sediments and not from the aquifer. Furthermore, it suggested that there is a dense Archaeal community in the shoreline pore water of the lake. Sequences of bacterial sulfate reducers, nitrifiers iron oxidizers and iron reducers were identified as well. Analysis of white and green biofilms suggested that sulfide oxidation through chemolitotrophy and phototrophy is highly significant. Hyperspectral analysis showed a tight association between abundant green sulfur bacteria and cyanobacteria in the green biofilms. Together, our findings show that the Dead Sea floor harbors diverse microbial communities, part of which is not known from other hypersaline environments. Analysis of the water’s chemistry shows evidence of microbial activity along the path and suggests that the springs supply nitrogen, phosphorus and organic matter to the microbial communities in the Dead Sea. The underwater springs are a newly recognized water source for the Dead Sea. Their input of microorganisms and nutrients needs to be considered in the assessment of possible impact of dilution events of the lake surface waters, such as those that will occur in the future due to the intended establishment of the Red Sea−Dead Sea water conduit

A different sequence of events than previously reported leads to arsenic-induced damage in Ceratophyllum demersum L.

Arsenic (As) is a common pollutant, and still many questions remain concerning As toxicity mechanisms under environmentally relevant conditions in plants. Here we investigated thresholds and interactions of various proposed As toxicity mechanisms. Experiments were done under environmentally pertinent conditions in the rootless aquatic macrophyte Ceratophyllum demersum L., a model for plant shoots. Arsenic (provided as As(V)) inhibited plant metabolism at much lower concentrations and with a different sequence of events than previously reported. The first observed effect of toxicity was a decrease in pigment concentration, it started even at 0.5 μM As. In contrast to toxic metals, no inhibition of the photosystem II reaction centre (PSIIRC; measured as Fv/Fm) was found at sublethal As concentrations. Instead, the decrease in light harvesting pigments caused a less efficient exciton transfer towards the PSIIRC. At higher As concentrations this led to increased non-photochemical quenching (NPQ) by light harvesting complex II (LHCII). Afterwards, photosynthetic electron transport decreased, but the increase in starch content indicated stronger inhibition of starch consumption than production. At lethal As concentration, photosynthesis was completely inhibited, its malfunction caused oxidative stress and not the other way round as reported previously. Photosynthesis was inhibited before any sign of oxidative stress was observed. Elevated phosphate drastically shifted thresholds of lethal As effects, not only by the known uptake competition but also by modifying uptake regulation and intracellular processes

Exploring the Extent of Phosphorus and Heavy Metal Uptake by Single Cells of Saccharomyces cerevisiae and Their Effects on Intrinsic Elements by SC-ICP-TOF-MS

The effect of six heavy metals, namely, silver (Ag), lead (Pb), palladium (Pd), copper (Cu), nickel (Ni), and chromium (Cr), on phosphorus (P) uptake by yeast was investigated by single-cell analysis using inductively coupled plasma time-of-flight mass spectrometry (SC-ICP-TOF-MS). It was found that the P content in cells with 1.55 g L1 P feeding after P starvation was increased by 70% compared to control cells. Heavy metals at 10 ppm, except Cu, had a negative impact on P accumulation by cells. Pd reduced the P content by 26% in single cells compared to control cells. Metal uptake was strongest for Ag and Pd (0.7 1012 L cell1) and weakest for Cr (0.05 1012 L cell1). Exposure to Cr markedly reduced (50%) Mg in cells and had the greatest impact on the intrinsic element composition. The SC-ICP-TOF-MS shows the diversity of elemental content in single cells: for example, the P content under standard conditions varied between 12.4 and 890 fg cell1. This technique allows studying both the uptake of elements and sublethal effects on physiology at a single-cell level

Speciation and Distribution of Arsenic in the Nonhyperaccumulator Macrophyte Ceratophyllum demersum

Although arsenic (As) is a common pollutant worldwide, many questions about As metabolism in nonhyperaccumulator plants remain. Concentration- and tissue-dependent speciation and distribution of As was analyzed in the aquatic plant Ceratophyllum demersum to understand As metabolism in nonhyperaccumulator plants. Speciation was analyzed chromatographically (high-performance liquid chromatography-[inductively coupled plasma-mass spectrometry]-[electrospray ionization-mass spectrometry]) in whole-plant extracts and by tissue-resolution confocal x-ray absorption near-edge spectroscopy in intact shock-frozen hydrated leaves, which were also used for analyzing cellular element distribution through x-ray fluorescence. Chromatography revealed up to 20 As-containing species binding more than 60% of accumulated As. Of these, eight were identified as thiol-bound (phytochelatins [PCs], glutathione, and cysteine) species, including three newly identified complexes: Cys-As(III)-PC2, Cys-As-(GS)2, and GS-As(III)-desgly-PC2. Confocal x-ray absorption near-edge spectroscopy showed arsenate, arsenite, As-(GS)3, and As-PCs with varying ratios in various tissues. The epidermis of mature leaves contained the highest proportion of thiol (mostly PC)-bound As, while in younger leaves, a lower proportion of As was thiol bound. At higher As concentrations, the percentage of unbound arsenite increased in the vein and mesophyll of young mature leaves. At the same time, x-ray fluorescence showed an increase of total As in the vein and mesophyll but not in the epidermis of young mature leaves, while this was reversed for zinc distribution. Thus, As toxicity was correlated with a change in As distribution pattern and As species rather than a general increase in many tissues

Mass Cytometry for Detection of Silver at the Bacterial Single Cell Level

Background: Mass cytometry (Cytometry by Time of Flight, CyTOF) allows single-cell characterization on the basis of specific metal-based cell markers. In addition, other metals in the mass range such as silver can be detected per cell. Bacteria are known to be sensible to silver and a protocol was developed to measure both the number of affected cells per population and the quantities of silver per cell.Methods: For mass cytometry ruthenium red was used as a marker for all cells of a population while parallel application of cisplatin discriminated live from dead cells. Silver quantities per cell and frequencies of silver containing cells in a population were measured by mass cytometry. In addition, live/dead subpopulations were analyzed by flow cytometry and distinguished by cell sorting based on ruthenium red and propidium iodide double staining. Verification of the cells’ silver load was performed on the bulk level by using ICP-MS in combination with cell sorting. The protocol was developed by conveying both, fast and non-growing Pseudomonas putida cells as test organisms.Results: A workflow for labeling bacteria in order to be analyzed by mass cytometry was developed. Three different parameters were tested: ruthenium red provided counts for all bacterial cells in a population while consecutively applied cisplatin marked the frequency of dead cells. Apparent population heterogeneity was detected by different frequencies of silver containing cells. Silver quantities per cell were also well measurable. Generally, AgNP-10 treatment caused higher frequencies of dead cells, higher frequencies of silver containing cells and higher per-cell silver quantities. Due to an assumed chemical equilibrium of free and bound silver ions live and dead cells were associated with silver in equal quantities and this preferably during exponential growth. With ICP-MS up to 1.5 fg silver per bacterial cell were detected.Conclusion: An effective mass cytometry protocol was developed for the detection and quantification of silver in single bacterial cells of different physiological states. The silver quantities were generally heterogeneously distributed among cells in a population, the degree of which was dependent on micro-environmental conditions and on silver applied either in ion or nanoparticle-aggregated form

Rare earth elements in two luvisols developed from loess under arable and forest land use in Bavaria, Germany: concentrations, stocks, and potential mobilities

Rare earth elements (REE) are of increasing interest in many industrial key technologies and in animal/plant production. Their environmental impacts cannot be forecasted because of knowledge gaps concerning the presence and the mobility of REE in soils and critical concentrations with respect to health effects on humans and other biota. In this study, the soil's chemical and physical characteristics were compared to REE concentrations and REE mobilities, as determined by ammonium nitrate/aqua regia ratio, in Luvisols developed from loess under arable and forest land according to genetic horizons in complete soil profiles in Germany. Single REE concentrations varied from 0.17 mg kg(-1) (Lu) to 77.3 mg kg(-1) (Ce). We detected the highest REE concentrations in illuvial B-horizons and found a significant correlation between REE and clay content/Fe-Mn oxides. This is probably because REE adsorb onto clay minerals and Fe-Mn oxides (found as coatings on clay minerals) and migrate with the colloids. Aqua regia-extractable REE concentrations ranged from 166 to 211 mg kg(-1) in the soil profile under forest land and from 176 to 230 mg kg(-1) under arable land. Stocks of REE in the top 100 cm are significantly higher under arable land use (277 g m(-2)) than under forest land use (252 g m(-2)), which might be caused by phosphorous fertilization and a significantly higher bulk density of the arable topsoil. The higher pH of the arable land leads to a lower potential mobility of REE in comparison with the soil under forest land