Publications by authors named "Hans-Joachim Stärk"

30 Publications

  • Page 1 of 1

Ruthenium red: a highly efficient and versatile cell staining agent for single-cell analysis using inductively coupled plasma time-of-flight mass spectrometry.

Analyst 2021 Oct 13. Epub 2021 Oct 13.

Department of Analytical Chemistry, Helmholtz Centre for Environmental Research - UFZ, Permoserstrasse 15, 04318, Leipzig, Germany.

Staining of biological cells with heavy metals can increase their visibility in mass spectrometry. In this study, the potential of ruthenium red (RR) as a staining agent for single-cell analysis by inductively coupled plasma time-of-flight mass spectrometry (SC-ICP-TOF-MS) is explored using two different yeast strains and one algal species. Time-of-flight mass spectrometry allows the simultaneous detection of Ru and multiple intrinsic elements in single cells. Ru has a better correlation with Mg than with P in () cells. For the three tested strains, the staining efficiency of RR exceeded 96%; the staining strengths were 30-32 ag μm for the yeast cells and 59 ag μm for the algal cells. By deriving the cell volume of single cells from their Ru mass, the concentration of Mg and P in individual cells of can be calculated. Elemental concentrations of Mg and P were highly variable in the cell individuals, with their 25-75 percentile values of 0.10-0.19 and 0.76-2.07 fg μm, respectively. RR staining has several advantages: it is fast, does not affect cell viability and is highly efficient. Provided that the shape of the individual cells of a culture is similar, Ru staining allows the elemental content to be directly correlated with the cell volume to accurately calculate the intracellular concentration of target elements in single cells. Therefore, RR can be a promising cell staining agent for future application in SC-ICP-TOF-MS research.
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http://dx.doi.org/10.1039/d1an01143jDOI Listing
October 2021

Determination of elemental distribution and evaluation of elemental concentration in single Saccharomyces cerevisiae cells using single cell-inductively coupled plasma mass spectrometry.

Metallomics 2021 06;13(6)

Department of Analytical Chemistry, Helmholtz Centre for Environmental Research-UFZ, Permoserstrasse 15, 04318 Leipzig, Germany.

Single-cell analysis using inductively coupled plasma mass spectrometry (SC-ICP-MS) is a method to obtain qualitative and quantitative information of the elemental content and distribution of single cells. Six intrinsic target elements were analyzed in yeast cells at different cell growth phases cultured in medium with different phosphorus concentrations (0, 7, 14 mM) to study its effect on cell growth and composition. SC-ICP-MS results were compared with those obtained by the acid digestion and the average ratio was 0.81. The limits of detection of this method were 0.08, 2.54, 12.5, 0.02, 0.02, and 0.08 fg cell-1 for Mg, P, K, Mn, Cu, and Zn, respectively. During the exponential growth phase, the cells exhibited higher elemental contents, wider distribution for most elements, and larger cell size in comparison to the stationary growth phase. Phosphorus-free conditions reduced the average P content in single cells of stationary growth phase from 650 to 80 fg. Phosphorus deficiency led to decreasing intracellular concentrations not only of P but also of K and Cu, and to increasing Zn concentration after 48 h. Mg maintained its concentration at ∼0.11 fg µm-3 and did not change significantly under the three investigated conditions after 48 h. Accordingly, Mg content was successfully used to estimate the intracellular concentration of other intrinsic elements in single yeast cells. SC-ICP-MS is suited to determine target elements in single yeast cells, and allows the study of heterogeneity of cell composition and effects of stressors on the elemental content, distribution, and concentrations of intrinsic elements.
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http://dx.doi.org/10.1093/mtomcs/mfab032DOI Listing
June 2021

Phytoremediation potential of twelve wild plant species for toxic elements in a contaminated soil.

Environ Int 2021 01 12;146:106233. Epub 2020 Nov 12.

University of Wuppertal, School of Architecture and Civil Engineering, Institute of Foundation Engineering, Water- and Waste Management, Laboratory of Soil- and Groundwater-Management, Pauluskirchstraße 7, 42285 Wuppertal, Germany; Department of Environment, Energy and Geoinformatics, Sejong University, Seoul 05006, Republic of Korea. Electronic address:

Green remediation of soils highly contaminated with potentially toxic elements (PTEs) can be achieved using suitable plants. Such phytoremediation procedure often takes into consideration PTE concentrations in plants only, but not produced biomass. Phytoremediation potential of certain species of wild plants for PTEs in contaminated floodplain soils has not been assessed yet. Therefore, in this work 12 native species were tested, 3 of which (Poa angustifolia, Galium mollugo, and Stellaria holostea) to our knowledge have never been used before, in a two-year pot experiment and assessed their potential as phytoremediation species. The results showed that plant PTE concentrations were dramatically elevated for Cd and Zn in Alopecurus pratensis, Arrhenatherum elatius, Bromus inermis, Artemisia vulgaris, Achillea millefolium, Galium mollugo, Stellaria holostea, and Silene vulgaris. A. vulgaris was by far the most highly PTE absorbing plant among the 12 tested in this work, especially concerning Zn, Cd, and to a lesser degree Cu and Ni. Also, among species non-studied-before, G. mollugo and S. holostea were characterized by high Zn and Cd uptake, while P. angustifolia did not. Assessing the number of harvests necessary to decrease soil PTE to half of the initial concentrations, it was found that for Cd plants would achieve site phytoremediation within 8 (A. vulgaris) to 28 (S. holostea) and 51 (G. mollugo) harvests, while for Zn, harvests ranged from 104 (A. vulgaris) to 209 (S. holostea), and 251 (A. millefolium). A clear grouping of the tested species according to their functional type was evident. Herbaceous species were collectively more efficient than grasses in PTE uptake combined by high biomass accumulation; thus, they may act as key-species in a phytoremediation-related concept. Our approach puts phytoremediation into a practical perspective as to whether the process can be achieved within a measureable amount of time. In conclusion, A. vulgaris behaved as a hyperaccumulator plant species in our heavily contaminated soil, while never-studied-before G. mollugo and S. holostea also had a hyperaccumulator behavior, especially for Cd and Zn. Although more research is necessary for conclusive results, our study is pivotal in that it would help in assessing plant species as potential phytoremediation species in heavily contaminated soils.
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http://dx.doi.org/10.1016/j.envint.2020.106233DOI Listing
January 2021

Surfactant assisted extraction of incidental nanoparticles from road runoff sediment and their characterization by single particle-ICP-MS.

Chemosphere 2020 May 28;246:125765. Epub 2019 Dec 28.

Department of Analytical Chemistry, Helmholtz Centre for Environmental Research GmbH - UFZ, Permoserstrasse 15, 04318, Leipzig, Germany. Electronic address:

A surfactant assisted extraction (SAE) method was developed to extract incidental nanoparticles (INPs) in the <300 nm particle size fraction from road runoff sediments and applied to a road runoff sediment. The method was evaluated by spiking experiments of road runoff sediment with engineered nanoparticle (ENP) suspensions of gold (Au-ENPs) between 30 nm and 200 nm and platinum (Pt-ENPs) between 30 nm and 70 nm with content ranging from 40 to 800 ng/g. Suspensions were analyzed by single particle (sp-)ICP-MS. In the presence of a road runoff matrix, an increase in ENP sizes by a maximum of 8% for Au-ENPs and 9% for Pt-ENPs was observed. ENPs mass recovery was >50% for all Au-ENPs with content higher than 200 ng/g and for 30 and 50 nm Pt-ENPs at content of 160 ng/g while for lower content the recovery was 0%. For 70 nm Pt-ENPs, recovery was always >80% and increased with increasing Pt content up to 100% in the presence of road runoff matrix. Metal content of INPs in the road runoff sediment in the fraction <300 nm decreased from copper (Cu; μg/g)> zinc (Zn)> zirconium (Zr)> cerium (Ce)> lead (Pb)> cadmium (Cd) > platinum (Pt; μg/g). Over 90% of Pt-, Zn-, Cd-, Pb- and Ce-INPs are composed of particles with less than 20 fg, while Zr- and Cu-INPs are dominated by masses higher than 20 fg. The tested SAE may be applicable to determine environmental contents of INPs in sediments and possibly in soils.
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http://dx.doi.org/10.1016/j.chemosphere.2019.125765DOI Listing
May 2020

The class II benzoyl-coenzyme A reductase complex from the sulfate-reducing Desulfosarcina cetonica.

Environ Microbiol 2019 11 1;21(11):4241-4252. Epub 2019 Sep 1.

Faculty of Biology - Microbiology, University of Freiburg, 79104, Freiburg, Germany.

Benzoyl-CoA reductases (BCRs) catalyse a key reaction in the anaerobic degradation pathways of monocyclic aromatic substrates, the dearomatization of benzoyl-CoA (BzCoA) to cyclohexa-1,5-diene-1-carboxyl-CoA (1,5-dienoyl-CoA) at the negative redox potential limit of diffusible enzymatic substrate/product couples (E°' = -622 mV). A 1-MDa class II BCR complex composed of the BamBCDEGHI subunits has so far only been isolated from the Fe(III)-respiring Geobacter metallireducens. It is supposed to drive endergonic benzene ring reduction at an active site W-pterin cofactor by flavin-based electron bifurcation. Here, we identified multiple copies of putative genes encoding the structural components of a class II BCR in sulfate reducing, Fe(III)-respiring and syntrophic bacteria. A soluble 950 kDa Bam[(BC) DEFGHI] complex was isolated from extracts of Desulfosarcina cetonica cells grown with benzoate/sulfate. Metal and cofactor analyses together with the identification of conserved binding motifs gave rise to 4 W-pterins, two selenocysteines, six flavin adenine dinucleotides, four Zn, and 48 FeS clusters. The complex exhibited 1,5-dienoyl-CoA-, NADPH- and ferredoxin-dependent oxidoreductase activities. Our results indicate that high-molecular class II BCR metalloenzyme machineries are remarkably conserved in strictly anaerobic bacteria with regard to subunit architecture and cofactor content, but their subcellular localization and electron acceptor preference may differ as a result of adaptations to variable energy metabolisms.
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http://dx.doi.org/10.1111/1462-2920.14784DOI Listing
November 2019

One-megadalton metalloenzyme complex in involved in benzene ring reduction beyond the biological redox window.

Proc Natl Acad Sci U S A 2019 02 23;116(6):2259-2264. Epub 2019 Jan 23.

Department of Microbiology, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany;

Reversible biological electron transfer usually occurs between redox couples at standard redox potentials ranging from +0.8 to -0.5 V. Dearomatizing benzoyl-CoA reductases (BCRs), key enzymes of the globally relevant microbial degradation of aromatic compounds at anoxic sites, catalyze a biological Birch reduction beyond the negative limit of this redox window. The structurally characterized BamBC subunits of class II BCRs accomplish benzene ring reduction at an active-site tungsten cofactor; however, the mechanism and components involved in the energetic coupling of endergonic benzene ring reduction have remained hypothetical. We present a 1-MDa, membrane-associated, Bam[(BC)DEFGHI] complex from the anaerobic bacterium harboring 4 tungsten, 4 zinc, 2 selenocysteines, 6 FAD, and >50 FeS cofactors. The results suggest that class II BCRs catalyze electron transfer to the aromatic ring, yielding a cyclic 1,5-dienoyl-CoA via two flavin-based electron bifurcation events. This work expands our knowledge of energetic couplings in biology by high-molecular-mass electron bifurcating machineries.
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http://dx.doi.org/10.1073/pnas.1819636116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6369795PMC
February 2019

Four Molybdenum-Dependent Steroid C-25 Hydroxylases: Heterologous Overproduction, Role in Steroid Degradation, and Application for 25-Hydroxyvitamin D Synthesis.

mBio 2018 06 19;9(3). Epub 2018 Jun 19.

Faculty of Biology-Microbiology, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany

Side chain-containing steroids are ubiquitous constituents of biological membranes that are persistent to biodegradation. Aerobic, steroid-degrading bacteria employ oxygenases for isoprenoid side chain and tetracyclic steran ring cleavage. In contrast, a Mo-containing steroid C-25 dehydrogenase (S25DH) of the dimethyl sulfoxide (DMSO) reductase family catalyzes the oxygen-independent hydroxylation of tertiary C-25 in the anaerobic, cholesterol-degrading bacterium Its genome contains eight paralogous genes encoding active site α-subunits of putative S25DH-like proteins. The difficult enrichment of labile, oxygen-sensitive S25DH from the wild-type bacteria and the inability of its active heterologous production have largely hampered the study of S25DH-like gene products. Here we established a heterologous expression platform for the three structural genes of S25DH subunits together with an essential chaperone in the denitrifying betaproteobacterium K172. Using this system, S25DH and three isoenzymes (S25DH, S25DH, and S25DH) were overproduced in a soluble, active form allowing a straightforward purification of nontagged αβγ complexes. All S25DHs contained molybdenum, four [4Fe-4S] clusters, one [3Fe-4S] cluster, and heme B and catalyzed the specific, water-dependent C-25 hydroxylations of various 4-en-3-one forms of phytosterols and zoosterols. Crude extracts from expressing genes encoding S25DH catalyzed the hydroxylation of vitamin D (VD) to the clinically relevant 25-OH-VD with >95% yield at a rate 6.5-fold higher than that of wild-type bacterial extracts; the specific activity of recombinant S25DH was twofold higher than that of wild-type enzyme. These results demonstrate the potential application of the established expression platform for 25-OH-VD synthesis and pave the way for the characterization of previously genetically inaccessible S25DH-like Mo enzymes of the DMSO reductase family. Steroids are ubiquitous bioactive compounds, some of which are considered an emerging class of micropollutants. Their degradation by microorganisms is the major process of steroid elimination from the environment. While oxygenase-dependent steroid degradation in aerobes has been studied for more than 40 years, initial insights into the anoxic steroid degradation have only recently been obtained. Molybdenum-dependent steroid C dehydrogenases (S25DHs) have been proposed to catalyze oxygen-independent side chain hydroxylations of globally abundant zoo-, phyto-, and mycosterols; however, so far, their lability has allowed only the initial characterization of a single S25DH. Here we report on a heterologous gene expression platform that allowed for easy isolation and characterization of four highly active S25DH isoenzymes. The results obtained demonstrate the key role of S25DHs during anoxic degradation of various steroids. Moreover, the platform is valuable for the efficient enzymatic hydroxylation of vitamin D to its clinically relevant C-25-OH form.
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http://dx.doi.org/10.1128/mBio.00694-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6016249PMC
June 2018

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

Front Microbiol 2017 17;8:1326. Epub 2017 Jul 17.

Department of Environmental Microbiology, Helmholtz Centre for Environmental ResearchLeipzig, Germany.

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. 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 cells as test organisms. 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. 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.
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http://dx.doi.org/10.3389/fmicb.2017.01326DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5511850PMC
July 2017

Phthaloyl-coenzyme A decarboxylase from Thauera chlorobenzoica: the prenylated flavin-, K - and Fe -dependent key enzyme of anaerobic phthalate degradation.

Environ Microbiol 2017 09 14;19(9):3734-3744. Epub 2017 Aug 14.

Faculty of Biology, Department of Microbiology, University of Freiburg, Freiburg, Germany.

The degradation of the industrially produced and environmentally relevant phthalate esters by microorganisms is initiated by the hydrolysis to alcohols and phthalate (1,2-dicarboxybenzene). In the absence of oxygen the further degradation of phthalate proceeds via activation to phthaloyl-CoA followed by decarboxylation to benzoyl-CoA. Here, we report on the first purification and characterization of a phthaloyl-CoA decarboxylase (PCD) from the denitrifying Thauera chlorobenzoica. Hexameric PCD belongs to the UbiD-family of (de)carboxylases and contains prenylated FMN (prFMN), K and, unlike other UbiD-like enzymes, Fe as cofactors. The latter is suggested to be involved in oxygen-independent electron-transfer during oxidative prFMN maturation. Either oxidation to the Fe -state in air or removal of K by desalting resulted in >92% loss of both, prFMN and decarboxylation activity suggesting the presence of an active site prFMN/Fe /K -complex in PCD. The PCD-catalysed reaction was essentially irreversible: neither carboxylation of benzoyl-CoA in the presence of 2 M bicarbonate, nor an isotope exchange of phthaloyl-CoA with C-bicarbonate was observed. PCD differs in many aspects from prFMN-containing UbiD-like decarboxylases and serves as a biochemically accessible model for the large number of UbiD-like (de)carboxylases that play key roles in the anaerobic degradation of environmentally relevant aromatic pollutants.
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http://dx.doi.org/10.1111/1462-2920.13875DOI Listing
September 2017

Rare earth elements and their release dynamics under pre-definite redox conditions in a floodplain soil.

Chemosphere 2017 Aug 15;181:313-319. Epub 2017 Apr 15.

University of Wuppertal, School of Architecture and Civil Engineering, Soil- and Groundwater-Management, Pauluskirchstraße 7, D-42285, Wuppertal, Germany; Sejong University, Department of Environment and Energy, 98 Gunja-Dong, Guangjin-Gu, Seoul, South Korea. Electronic address:

For the first time, the impact of pre-definite redox conditions on the release dynamics of rare earth elements (REEs) and the determining factors pH, iron (Fe), manganese (Mn), aluminum (Al), dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and sulfate (SO) in a floodplain soil was elucidated using an advanced, highly sophisticated automatic biogeochemical microcosm apparatus. The redox potential (E) ranged between +82 and + 498 mV during the experiment. The systematic increase of E caused a decreasing pH from 6.6 to 4.6 which resulted in an enhanced mobilization and release of REEs along with Fe, Al, and Mn under oxic and acidic conditions. Also, organic matter seems to contribute to the mobilization of REEs under changing redox conditions. A factor analysis identified that the REEs form one group with E, Fe, Al, and Mn what indicates that REEs and sesquioxides have a similar geochemical behavior. The pH, DOC, and DIC are together in another cluster which demonstrates that their behavior substantially differs from the other group. The sequential extraction procedure revealed that the majority of the REEs were bound in the residual fraction, followed by the reducible, the oxidisable and the water soluble/exchangeable/carbonate bound fraction. Future studies should further elucidate the specific release kinetics of REEs, the controlling factors on the release dynamics and the underlying mobilization processes in highly dynamic wetland soils around the globe.
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http://dx.doi.org/10.1016/j.chemosphere.2017.04.036DOI Listing
August 2017

Redox-controlled release dynamics of thallium in periodically flooded arable soil.

Chemosphere 2017 Jul 16;178:268-276. Epub 2017 Mar 16.

University of Wuppertal, School of Architecture and Civil Engineering, Institute of Foundation Engineering, Water- and Waste-Management, Soil- and Groundwater-Management, Pauluskirchstraße 7, 42285, Wuppertal, Germany; Sejong University, Department of Environment and Energy, 98 Gunja-Dong, Guangjin-Gu, Seoul, South Korea. Electronic address:

To our knowledge, this is the first work to mechanistically study the impact of the redox potential (E) and principal factors, such as pH, iron (Fe), manganese (Mn), dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), chlorides (Cl) and sulfates (SO), on the release dynamics of thallium (Tl) in periodically flooded soil. We simulated flooding using an automated biogeochemical microcosm system that allows for systematical control of pre-defined redox windows. The E value was increased mechanistically at intervals of approximately 100 mV from reducing (-211 mV) to oxidizing (475 mV) conditions. Soluble Tl levels (0.02-0.28 μg L) increased significantly with increases in E (r = 0.80, p < 0.01, n = 30). Thallium mobilization was found to be related to several simultaneous processes involving the gradual oxidation of Tl-bearing sulfides, reductive dissolution of Fe-Mn oxides and desorption from mineral sorbents. Manganese oxides did not appear to have a considerable effect on Tl retention under oxidizing conditions. Before conducting the microcosm experiment, Tl geochemical fractionation was assessed using the modified BCR sequential extraction procedure. The BCR revealed a majority of Tl in the residual fraction (77.7%), followed by reducible (13.3%) and oxidizable fractions (5.9%). By generating high levels of Tl toxicity at low doses, Tl released under oxidizing conditions may pose an environmental threat. In the future, similar studies should be conducted on various soils along with a determination of the Tl species and monitoring of the Tl content in plants to achieve more detailed insight into soluble Tl behavior.
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http://dx.doi.org/10.1016/j.chemosphere.2017.03.060DOI Listing
July 2017

Biogeochemistry of Ni and Pb in a periodically flooded arable soil: Fractionation and redox-induced (im)mobilization.

J Environ Manage 2017 Jan 16;186(Pt 2):141-150. Epub 2016 Jun 16.

University of Wuppertal, Soil- and Groundwater-Management, Pauluskirchstraße 7, 42285 Wuppertal, Germany.

The redox-induced (im)mobilization of nickel (Ni) and lead (Pb) under pre-definite redox conditions and their binding forms were studied in a periodically flooded, slightly acidic arable soil enriched with serpentine minerals at the Velika Morava River valley, Serbia. The total contents of Ni and Pb were 152 and 109 mg kg, respectively. Geochemical fractionation of Ni, combined with mineralogical analysis, confirmed its geogenic origin in the soil. Potentially mobile fractions were the dominating binding forms of Pb; thus, indicating anthropogenic sources as prevailing. Risk assessment indicated a low risk of Ni and Pb transfer from soil to other environmental constituents. However, the results imply that geogenic metals might pose higher environmental risk than those from anthropogenic origin, in dependence of their total concentrations and contents in the specific solid-phase fractions. Flooding of the soil was simulated in an automated biogeochemical microcosm system, which allows a control and a continuous measurements of redox potential (E) and pH. Subsequently, the E was increased in steps of approximately 100 mV from anoxic to oxic conditions. Concurrently, the concentrations of soluble Ni, Pb, iron (Fe), manganese (Mn), dissolved organic carbon (DOC), and sulfates were measured. The E was brought from low to high values (-220 to 520 mV) and correlated negative with soluble Ni, Pb, Fe, Mn and DOC. Soluble Ni ranged from 125 to 228 μg l while Pb ranged from 3.0 to 21.4 μg l. Concentrations of both metals in solution were high at low E and decreased with increasing E. Nickel immobilization may be attributed to sorption to or co-precipitation with re-oxidized Fe-Mn (hydr)oxides, whereas Pb, in addition, might be immobilized via precipitation with inorganic ligands, such as carbonates and phosphates. The results imply that Ni and Pb solubility might also be related to the formation of metal-DOC complexes. The detected dynamic and mechanisms might be useful in providing critical information for assessing the potential environmental risk and creating appropriate environmental management strategies for agricultural areas enriched with Ni and Pb.
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http://dx.doi.org/10.1016/j.jenvman.2016.06.005DOI Listing
January 2017

Cadmium toxicity investigated at the physiological and biophysical levels under environmentally relevant conditions using the aquatic model plant Ceratophyllum demersum.

New Phytol 2016 06 3;210(4):1244-58. Epub 2016 Feb 3.

Department of Plant Biophysics and Biochemistry, Institute of Plant Molecular Biology, Biology Centre of the CAS, Branišovská 31/1160, České Budějovice, CZ-37005, Czech Republic.

Cadmium (Cd) is an important environmental pollutant and is poisonous to most organisms. We aimed to unravel the mechanisms of Cd toxicity in the model water plant Ceratophyllum demersum exposed to low (nM) concentrations of Cd as are present in nature. Experiments were conducted under environmentally relevant conditions, including nature-like light and temperature cycles, and a low biomass to water ratio. We measured chlorophyll (Chl) fluorescence kinetics, oxygen exchange, the concentrations of reactive oxygen species and pigments, metal binding to proteins, and the accumulation of starch and metals. The inhibition threshold concentration for most parameters was 20 nM. Below this concentration, hardly any stress symptoms were observed. The first site of inhibition was photosynthetic light reactions (the maximal quantum yield of photosystem II (PSII) reaction centre measured as Fv /Fm , light-acclimated PSII activity ΦPSII , and total Chl). Trimers of the PSII light-harvesting complexes (LHCIIs) decreased more than LHC monomers and detection of Cd in the monomers suggested replacement of magnesium (Mg) by Cd in the Chl molecules. As a consequence of dysfunctional photosynthesis and energy dissipation, reactive oxygen species (superoxide and hydrogen peroxide) appeared. Cadmium had negative effects on macrophytes at much lower concentrations than reported previously, emphasizing the importance of studies applying environmentally relevant conditions. A chain of inhibition events could be established.
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http://dx.doi.org/10.1111/nph.13840DOI Listing
June 2016

Determination of moderately polar arsenolipids and mercury speciation in freshwater fish of the River Elbe (Saxony, Germany).

Environ Pollut 2016 Jan 6;208(Pt B):458-66. Epub 2015 Nov 6.

Helmholtz Centre for Environmental Research - UFZ, Department of Analytical Chemistry, Permoserstrasse 15, 04318 Leipzig, Germany.

Arsenic and mercury are frequent contaminants in the environment and care must be taken to limit their entrance into the food chain. The toxicity of both elements strongly depends upon their speciation. Total amounts of As and Hg as well as their species were analyzed in muscle and liver of 26 fishes of seven freshwater fish species caught in the River Elbe. The median concentrations of As were 162 μg kg(-1) w.w. in liver and 92 μg kg(-1) w.w. in muscle. The median concentrations of total Hg were 241 μg kg(-1) w.w. in liver and 256 μg kg(-1) w.w. in muscle. While this level of Hg contamination of the freshwater fish in the River Elbe is significantly lower than 20 years ago, it exceeds the recommended environmental quality standard of 20 μg Hg kg(-1) w.w. by a factor of 5-50. However, the European maximum level of 500 μg Hg kg(-1) for fish for human consumption is rarely exceeded. Arsenic-containing fatty acids and hydrocarbons were determined and partially identified in methanolic extracts of the fish by HPLC coupled in parallel to ICP-MS (element specific detection) and ESI-Q-TOF-MS (molecular structure detection). While arsenobetaine was the dominant As species in the fish, six arsenolipids were detected and identified in the extracts of liver tissue in common bream (Abramis brama), ide (Leuciscus idus), asp (Aspius aspius) and northern pike (Esox lucius). Four arsenic-containing fatty acids (AsFA) and two arsenic-containing hydrocarbons (AsHC) are reported in freshwater fish for the first time. With respect to mercury the more toxic MeHg(+) was the major species in muscle tissue (>90% of total Hg) while in liver Hg(2+) and MeHg(+) were of equal importance. The results show the high relevance of element speciation in addition to the determination of total element concentrations to correctly assess the burden of these two elements in fish.
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http://dx.doi.org/10.1016/j.envpol.2015.10.015DOI Listing
January 2016

Structural basis of enzymatic benzene ring reduction.

Nat Chem Biol 2015 Aug 29;11(8):586-91. Epub 2015 Jun 29.

Microbiology, Faculty of Biology, University of Freiburg, Freiburg, Germany.

In chemical synthesis, the widely used Birch reduction of aromatic compounds to cyclic dienes requires alkali metals in ammonia as extremely low-potential electron donors. An analogous reaction is catalyzed by benzoyl-coenzyme A reductases (BCRs) that have a key role in the globally important bacterial degradation of aromatic compounds at anoxic sites. Because of the lack of structural information, the catalytic mechanism of enzymatic benzene ring reduction remained obscure. Here, we present the structural characterization of a dearomatizing BCR containing an unprecedented tungsten cofactor that transfers electrons to the benzene ring in an aprotic cavity. Substrate binding induces proton transfer from the bulk solvent to the active site by expelling a Zn(2+) that is crucial for active site encapsulation. Our results shed light on the structural basis of an electron transfer process at the negative redox potential limit in biology. They open the door for biological or biomimetic alternatives to a basic chemical synthetic tool.
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http://dx.doi.org/10.1038/nchembio.1849DOI Listing
August 2015

Exploring LA-ICP-MS as a quantitative imaging technique to study nanoparticle uptake in Daphnia magna and zebrafish (Danio rerio) embryos.

Anal Bioanal Chem 2015 Jul 6;407(18):5477-85. Epub 2015 May 6.

Department of Bioanalytical Ecotoxicology, Helmholtz Centre for Environmental Research - UFZ, Permoserstrasse 15, 04318, Leipzig, Germany.

The extent and the mechanisms by which engineered nanoparticles (ENPs) are incorporated into biological tissues are a matter of intensive research. Therefore, laser ablation coupled to inductively coupled plasma mass spectrometry (LA-ICP-MS) is presented for the detection and visualization of engineered nanoparticles (Al2O3, Ag, and Au) in ecotoxicological test organisms (Danio rerio and Daphnia magna). While ENPs are not taken up by the zebrafish embryo but attach to its chorion, incorporation into the gut of D. magna is clearly visible by a 50-μm spot ablation of 40-μm-thick organism sections. During laser ablation of the soft organic matrix, the hard ENPs are mobilized without a significant change in their size, leading to decreasing sensitivity with increasing size of ENPs. To compensate for these effects, a matrix-matched calibration with ENPs of the same size embedded in agarose gels is proposed. Based on such a calibration, the mass of ENPs within one organism section was calculated and used to estimate the total mass of ENPs per organism. Compared to the amount determined after acid digestion of the test organisms, recoveries of 20-100% (zebrafish embryo (ZFE)) and of 4-230% (D. magna) were obtained with LODs in the low ppm range. It is likely that these differences are primarily due to an inhomogeneous particle distribution in the organisms and to shifts in the particle size distribution from the initial ENPs to those present in the organism. It appears that quantitative imaging of ENPs with LA-ICP-MS requires knowledge of the particle sizes in the biological tissue under study.
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http://dx.doi.org/10.1007/s00216-015-8720-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4477941PMC
July 2015

Quantification of AlO nanoparticles in human cell lines applying inductively coupled plasma mass spectrometry (neb-ICP-MS, LA-ICP-MS) and flow cytometry-based methods.

J Nanopart Res 2014 8;16(9):2592. Epub 2014 Aug 8.

Department of Bioanalytical Ecotoxicology, Helmholtz Centre for Environmental Research - UFZ, Permoserstr. 15, 04318 Leipzig, Germany.

In order to quantify and compare the uptake of aluminum oxide nanoparticles of three different sizes into two human cell lines (skin keratinocytes (HaCaT) and lung epithelial cells (A549)), three analytical methods were applied: digestion followed by nebulization inductively coupled plasma mass spectrometry (neb-ICP-MS), direct laser ablation ICP-MS (LA-ICP-MS), and flow cytometry. Light and electron microscopy revealed an accumulation and agglomeration of all particle types within the cell cytoplasm, whereas no particles were detected in the cell nuclei. The internalized AlO particles exerted no toxicity in the two cell lines after 24 h of exposure. The smallest particles with a primary particle size () of 14 nm (Alu1) showed the lowest sedimentation velocity within the cell culture media, but were calculated to have settled completely after 20 h. Alu2 ( = 111 nm) and Alu3 ( = 750 nm) were calculated to reach the cell surface after 7 h and 3 min, respectively. The internal concentrations determined with the different methods lay in a comparable range of 2-8 µg AlO/cm cell layer, indicating the suitability of all methods to quantify the nanoparticle uptake. Nevertheless, particle size limitations of analytical methods using optical devices were demonstrated for LA-ICP-MS and flow cytometry. Furthermore, the consideration and comparison of particle properties as parameters for particle internalization revealed the particle size and the exposure concentration as determining factors for particle uptake.
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http://dx.doi.org/10.1007/s11051-014-2592-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4176630PMC
August 2014

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

Metallomics 2014 Mar 2;6(3):444-54. Epub 2014 Jan 2.

University of Konstanz, Department of Biology, Postbox M631, D-78457 Konstanz, Germany.

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.
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http://dx.doi.org/10.1039/c3mt00317eDOI Listing
March 2014

Effects of Cd & Ni toxicity to Ceratophyllum demersum under environmentally relevant conditions in soft & hard water including a German lake.

Aquat Toxicol 2013 Oct 21;142-143:387-402. Epub 2013 Sep 21.

University of Konstanz, Department of Biology, D-78457 Konstanz, Germany. Electronic address:

Even essential trace elements are phytotoxic over a certain threshold. In this study, we investigated whether heavy metal concentrations were responsible for the nearly complete lack of submerged macrophytes in an oligotrophic lake in Germany. We cultivated the rootless aquatic model plant Ceratophyllum demersum under environmentally relevant conditions like sinusoidal light and temperature cycles and a low plant biomass to water volume ratio. Experiments lasted for six weeks and were analysed by detailed measurements of photosynthetic biophysics, pigment content and hydrogen peroxide production. We established that individually non-toxic cadmium (3 nM) and slightly toxic nickel (300 nM) concentrations became highly toxic when applied together in soft water, severely inhibiting photosynthetic light reactions. Toxicity was further enhanced by phosphate limitation (75 nM) in soft water as present in many freshwater habitats. In the investigated lake, however, high water hardness limited the toxicity of these metal concentrations, thus the inhibition of macrophytic growth in the lake must have additional reasons. The results showed that synergistic heavy metal toxicity may change ecosystems in many more cases than estimated so far.
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http://dx.doi.org/10.1016/j.aquatox.2013.09.016DOI Listing
October 2013

Speciation and distribution of arsenic in the nonhyperaccumulator macrophyte Ceratophyllum demersum.

Plant Physiol 2013 Nov 20;163(3):1396-408. Epub 2013 Sep 20.

Universität Konstanz, Mathematisch-Naturwissenschaftliche Sektion, Fachbereich Biologie, D-78457 Konstanz, Germany.

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.
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http://dx.doi.org/10.1104/pp.113.224303DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3813659PMC
November 2013

Effects of nanomolar copper on water plants--comparison of biochemical and biophysical mechanisms of deficiency and sublethal toxicity under environmentally relevant conditions.

Aquat Toxicol 2013 Sep 18;140-141:27-36. Epub 2013 May 18.

Universität Konstanz, Mathematisch-Naturwissenschaftliche Sektion, Fachbereich Biologie, D-78457 Konstanz, Germany.

Toxicity and deficiency of essential trace elements like Cu are major global problems. Here, environmentally relevant sub-micromolar concentrations of Cu (supplied as CuSO4) and simulations of natural light- and temperature cycles were applied to the aquatic macrophyte Ceratophyllum demersum. Growth was optimal at 10nM Cu, while PSII activity (Fv/Fm) was maximal around 2 nM Cu. Damage to the PSII reaction centre was the first target of Cu toxicity, followed by disturbed regulation of heat dissipation (NPQ). Only after that, electron transport through PSII (ΦPSII) was inhibited, and finally chlorophylls decreased. Copper accumulation in the plants was stable until 10nM Cu in solution, but strongly increased at higher concentrations. The vein was the main storage site for Cu up to physiological concentrations (10nM). At toxic levels it was also sequestered to the epidermis and mesophyll until export from the vein became inhibited, accompanied by inhibition of Zn uptake. Copper deficiency led to a complete stop of growth at "0"nM Cu after 6 weeks. This was accompanied by high starch accumulation although electron flow through PSII (ΦPSII) decreased from 2 weeks, followed by decrease in pigments and increase of non photochemical quenching (NPQ). Release of Cu from the plants below 10nM Cu supply in the nutrient solution indicated lack of high-affinity Cu transporters, and on the tissue level copper deficiency led to a re-distribution of zinc.
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http://dx.doi.org/10.1016/j.aquatox.2013.05.008DOI Listing
September 2013

Microbial and chemical characterization of underwater fresh water springs in the Dead Sea.

PLoS One 2012 5;7(6):e38319. Epub 2012 Jun 5.

Max Planck Institute for Marine Microbiology, Bremen, Germany.

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.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0038319PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3367964PMC
October 2012

Behaviour of metalloids and metals from highly polluted soil samples when mobilized by water--evaluation of static versus dynamic leaching.

Environ Pollut 2012 Jun 8;165:59-66. Epub 2012 Mar 8.

Department of Analytical Chemistry, UFZ - Helmholtz Centre for Environmental Research, Permoserstrasse 15, 04318 Leipzig, Germany.

The mobilization behaviour of metalloids and metals when leached by water from highly polluted soil/sediment samples was studied using static and dynamic approaches employing batch methodology and rotating coiled columns (RCC), respectively. Increasing the solution-to-solid ratios during batch leaching resulted in different enhanced mobilization rates, which are element-specific and matrix-specific. When dynamic leaching is employed with continuous replacement of the eluent, a higher portion is mobilized than when using batch elution with an identical solid-to-water ratio. Using RCC the time-resolved leaching of the elements was monitored to demonstrate the leaching patterns. For the majority of elements a significant decrease could be shown in the mobilized portion of the elements with ongoing leaching process. The data were discussed targeted at solid liquid partitioning coefficients of the metal(loid)s. The capabilities in application of K(d) values was demonstrated for dynamic leaching which is relevant for environmental processes.
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http://dx.doi.org/10.1016/j.envpol.2012.02.006DOI Listing
June 2012

Dynamics of mercury fluxes and their controlling factors in large Hg-polluted floodplain areas.

Environ Pollut 2010 Jan 30;158(1):308-18. Epub 2009 Jul 30.

Soil- and Groundwater-Management, Department D, University of Wuppertal, Pauluskirchstrasse 7, D-42285 Wuppertal, Germany.

Environmental pollution by mercury (Hg) is a considerable environmental problem world-wide. Due to the occurrence of Hg volatilization from their soils, floodplains can function as an important source of volatile Hg. Soil temperature and soil water content related to flood dynamics are considered as important factors affecting seasonal dynamics of total gaseous mercury (TGM) fluxes. We quantified seasonal variations of TGM fluxes and conducted a laboratory microcosm experiment to assess the effect of temperature and moisture on TGM fluxes in heavily polluted floodplain soils. Observed TGM emissions ranged from 10 to 850 ng m(-2) h(-1) and extremely exceeded the emissions of non-polluted sites. TGM emissions increased exponentially with raised air and soil temperatures in both field (R(2): 0.49-0.70) and laboratory (R(2): 0.99) experiments. Wet soil material showed higher TGM fluxes, whereas the role of soil water content was affected by sampling time during the microcosm experiments.
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http://dx.doi.org/10.1016/j.envpol.2009.07.001DOI Listing
January 2010

Simultaneous determination of inorganic and organic antimony species by using anion exchange phases for HPLC-ICP-MS and their application to plant extracts of Pteris vittata.

Talanta 2009 May 15;78(3):820-6. Epub 2009 Jan 15.

UFZ Helmholtz Centre for Environmental Research, Department of Analytical Chemistry, Permoserstrasse 15, 04318 Leipzig, Germany.

Antimony is a common contaminant at abandoned sites for non-ferrous ore mining and processing. Because of the possible risk of antimony by transfer to plants growing on contaminated sites, it is of importance to analyze antimony and its species in such biota. A method based on high performance liquid chromatographic separation and inductively coupled plasma mass spectrometric detection (HPLC-ICP-MS) was developed to determine inorganic antimony species such as Sb(III) and Sb(V) as well as possible antimony-organic metabolisation products of the antimony transferred into plant material within one chromatographic run. The separation is performed using anion chromatography on a strong anion exchange column (IonPac AS15/AG 15). Based on isocratic optimizations for the separation of Sb(III) and Sb(V) as well as Sb(V) and trimenthylated Sb(V) (TMSb(V)), a chromatographic method with an eluent gradient was developed. The suggested analytical method was applied to aqueous extracts of Chinese break fern Pteris vittata samples. The transfer of antimony from spiked soil composites into the fern, which is known as a hyperaccumulator for arsenic, was investigated under greenhouse conditions. Remarkable amounts of antimony were transferred into roots and leaves of P. vittata growing on spiked soil composites. Generally, P. vittata accumulates not only arsenic (as shown in a multiplicity of studies in the last decade), but also antimony to a lower extent. The main contaminant in the extracts was Sb(V), but also elevated concentrations of Sb(III) and TMSb(V) (all in microg L(-1) range). An unidentified Sb compound in the plant extracts was detected, which slightly differ in elution time from TMSb(V).
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http://dx.doi.org/10.1016/j.talanta.2008.12.059DOI Listing
May 2009

Determination of gadolinium in river water by SPE preconcentration and ICP-MS.

Talanta 2004 May;63(2):309-16

Umweltforschungszentrum Leipzig-Halle, Department of Analytical Chemistry, Permoserstrasse 15, 04318 Leipzig, Germany; Institute of Analytical Chemistry, University of Leipzig, Linnèstr. 3, 04103 Leipzig, Germany.

An analytical scheme was developed for the determination of Gd-diethylenetriaminepentaacetate (Gd-DTPA), Gd and the other rare earth elements (REE) in river water by inductively coupled plasma (quadrupole) mass spectrometry (ICP-Q-MS). The preconcentration step was essential, since the limits of detection of this multielemental analytical technique are higher than the trace concentrations of the interesting elements in river water. Solid phase extraction (SPE) with different commercially available complexing agents (Chelex 100, Toyopearl and ethylhexylphosphates) was employed for the preconcentration of REE. The investigations revealed that complex stability (varying in dependence of the pH value) has a strong influence on the degree of the enrichment of Gd-DTPA. Based on acidified water samples (pH<3) a procedure using ethylhexylphosphates was proposed for the preconcentration of Gd and REE from surface water samples. For this purpose C(18)-cartridges loaded with ethylhexylphosphates were used, resulting in an enrichment factor of 40.
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http://dx.doi.org/10.1016/j.talanta.2003.10.053DOI Listing
May 2004

Evidence for declining levels of heavy-metals in the Severn Estuary and Bristol Channel, U.K. and their spatial distribution in sediments.

Environ Pollut 2006 Sep 7;143(2):187-96. Epub 2006 Feb 7.

Department of Chemical Ecotoxicology, UFZ Centre for Environmental Research, D-04318 Leipzig, Germany.

Levels of heavy-metals (Cd, Cu, Cr, Ni, Pb and Zn) in suspended particulate and in surface and subsurface sediments were determined at seven locations in the Severn Estuary and Bristol Channel. Sediment metal concentrations were highest at sites close to industrial centres but levels have decreased significantly over the last 30 years so that they are now close to, or meet, environmental quality guidelines. The greatest metal concentrations in deposited sediments were usually associated with the finest particulates at locations with muddy sediments, but this was not always true at sites with predominantly sandy sediments. The metals bound to suspended particulates at all sites were remarkably consistent, presumably reflecting the mixing capacity of this macro-tidal estuary. The re-exposure of older, more contaminated sediments could explain the observed differences between deposited and suspended material. Sediment redistribution due to strong seasonal currents might also explain the differences between winter and summer samples.
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http://dx.doi.org/10.1016/j.envpol.2005.12.002DOI Listing
September 2006

A simple field method to determine mercury volatilization from soils.

Environ Sci Pollut Res Int 2005 ;12(3):133-5

UFZ Centre for Environmental Research Leipzig-Halle, Department of Soil Science, Theodor-Lieser-Strasse 4, 06120 Halle/Saale, Germany.

Background: Estimations of gaseous mercury volatilization from soils are often complex, stationary and expensive. Our objective was to develop a mobile and more simple, easy to handle and more cost-effective field method allowing rapid estimates of potential Hg emissions from soils.

Methods: The study site is located in Germany, about 100 kilometers south-westerly of Berlin and influenced by the river Elbe and its tributary Saale river. The site is representative for a lot of other floodplain locations at the river Elbe and highly polluted with Hg and other heavy metals. For our study we developed a system consisting of a glass chamber gas, two gold traps, a battery operated pump and a gas meter. Adsorbed total gaseous mercury (TGM) in the gold traps was determined by use of atomic absorption spectrometry (AAS).

Results And Discussion: In contrast to the common used flux chambers we designed a chamber without inlet and named it gas suck up chamber (GSC). TGM fluxes determined with the GSC showed a very close linear correlation (r = 0.993) between the TGM content in the gold traps and the corresponding pumped gas volume. The TGM adsorbed, increased proportional with increasing gas volume indicating homogenous concentrations of gaseous mercury in the soil air sucked. In contrast to the commonly used dynamic flux chamber with the aim of precisely measuring actual fluxes of Hg from a defined soil area, we focused on developing of a measurement system which will allow rapid estimates of potential Hg emissions of a site. Earlier research at the study site indicated a high potential for releasing volatile Hg from the soil to the atmosphere. Indeed, due to the high Hg content of the soil significant amounts of TGM could be detected and no shortage was reached.

Conclusion: Our initial measurements are still too few in number neither to generalize the achieved results nor discuss controlling factors and processes. However, we are pleased to communicate that the developed GSC is well suited to become an effective sampling set up to rapidly estimate the magnitude of Hg volatilization from soils.

Outlook: Further measurements at other polluted locations are necessary to verify the GSC method. In addition the use of a mercury analyzer instead of gold traps is planned for faster risk assessments.
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http://dx.doi.org/10.1065/espr2005.05.251DOI Listing
July 2005
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