Pichler, Thomas
Lade...
Preferred name
Pichler, Thomas
Official Name
Pichler, Thomas
Alternative Name
Pichler, T.
ORCID
GND
57 Ergebnisse
Gerade angezeigt 1 - 10 von 57
- Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Energy sources for chemolithotrophs in an arsenic- and iron-rich shallow-sea hydrothermal systemThe hydrothermally influenced sediments of Tutum Bay, Ambitle Island, Papua New Guinea, are ideal for investigating the chemolithotrophic activities of micro-organisms involved in arsenic cycling because hydrothermal vents there expel fluids with arsenite (AsIII) concentrations as high as 950 μg L−1. These hot (99 °C), slightly acidic (pH ∼6), chemically reduced, shallow-sea vent fluids mix with colder, oxidized seawater to create steep gradients in temperature, pH, and concentrations of As, N, Fe, and S redox species. Near the vents, iron oxyhydroxides precipitate with up to 6.2 wt% arsenate (AsV). Here, chemical analyses of sediment porewaters from 10 sites along a 300-m transect were combined with standard Gibbs energies to evaluate the energy yields (−ΔGr) from 19 potential chemolithotrophic metabolisms, including AsV reduction, AsIII oxidation, FeIII reduction, and FeII oxidation reactions. The 19 reactions yielded 2–94 kJ mol−1 e−, with aerobic oxidation of sulphide and arsenite the two most exergonic reactions. Although anaerobic AsV reduction and FeIII reduction were among the least exergonic reactions investigated, they are still potential net metabolisms. Gibbs energies of the arsenic redox reactions generally correlate linearly with pH, increasing with increasing pH for AsIII oxidation and decreasing with increasing pH for AsV reduction. The calculated exergonic energy yields suggest that micro-organisms could exploit diverse energy sources in Tutum Bay, and examples of micro-organisms known to use these chemolithotrophic metabolic strategies are discussed. Energy modeling of redox reactions can help target sampling sites for future microbial collection and cultivation studies.Wissenschaftlicher ArtikelBand:9Heft:571 180 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Stable and radiogenic isotopes as tracers for the origin, mixing and subsurface history of fluids in submarine shallow-water hydrothermal systemsThe shallow-water hydrothermal system in Tutum Bay on the west side of Ambitle Island, Papua New Guinea provides us with an exceptional opportunity to study isotope systematics in a near shore setting. Compared to seawater, the hydrothermal fluids in Tutum Bay have lower values for δD, δ18O, δ13C, and 87Sr and higher values for 3H, δ34S(SO4) and δ18O(SO4). The δ18O and δD records for vents 1 and 4 indicate that fluid compositions remained stable over an extended period. Interpretation of isotope data clearly demonstrates the predominantly meteoric origin of Tutum Bay hydrothermal fluids, despite their location in a marine environment. δ18O and δD values are identical to mean average annual precipitation in eastern Papua New Guinea. The hypothesis that these fluids are a simple product of mixing between seawater and onshore hydrothermal fluids from the Waramung (W-1) and Kapkai (W-2) thermal areas has been rejected, because the observed δ37Cl, 3H, δ34S(SO4) and δ18O(SO4) values cannot be explained by a simple mixing model. The application of δ18O(SO4) and δ13C thermometers in combination with 3H values corroborates the three-step model of Pichler et al. [Pichler, T., Veizer, J., Hall, G.E.M., 1999. The chemical composition of shallow-water hydrothermal fluids in Tutum Bay, Ambitle Island, Papua New Guinea and their effect on ambient seawater. Marine Chemistry 64 (3) 229–252], where (1) phase separation in the deep reservoir beneath Ambitle Island produces a high temperature vapor that rises upward and subsequently reacts with cooler ground water to form a low pH, CO2-rich water of approximately 150–160 °C, (2) caused by the steep topography, this CO2-rich fluid moves laterally towards the margin of the hydrothermal system where it mixes with the marginal upflow of the deep reservoir fluid. This produces a dilute chloride water of approximately 165 °C, and (3) possibly the entrainment of minor amounts of ground or seawater during its final ascent.Wissenschaftlicher ArtikelBand:139Heft:3-4429 63 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Boron isotope variations in geothermal systems on Java, IndonesiaThis paper presents δ11B data for hot springs, hot acid crater lakes, geothermal brines and a steam vent from Java, Indonesia. The processes that produce a large range of the δ11B values were investigated, including the possible input of seawater as well as the contrast δ11B compositions of acid sulfate and acid chloride crater lakes. The δ11B values of hot springs ranged from − 2.4 to + 28.7‰ and acid crater lakes ranged from + 0.6 to + 34.9‰. The δ11B and Cl/B values in waters from the Parangtritis and Krakal geothermal systems confirmed seawater input. The δ11B values of acid sulfate crater lakes ranged from + 5.5 to + 34.9‰ and were higher than the δ11B of + 0.6‰ of the acid chloride crater lake. The heavier δ11B in the acid sulfate crater lakes was caused by a combination of vapor phase addition and further enrichment due to evaporation and B adsorption onto clay minerals. In contrast, the light δ11B of the acid chloride crater lake was a result of acid water-rocks interaction. The correlations of δ11B composition with δ18O and δ2H indicated that the B isotope corresponded to their groundwater mixing sources, but not for J21 (Segaran) and J48 (Cikundul) that underwent 11B isotope enrichment by B adsorption into minerals.Wissenschaftlicher ArtikelBand:31175 120 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Mercury in the hydrothermal fluids and gases in Paleochori Bay, Milos, Greece(Elsevier Science, 2021-06-20); ; ; Seafloor hydrothermal activity may constitute a considerable mercury (Hg) source to the oceans, but the flux from marine shallow-water hydrothermal systems (MSWHS) remains poorly constrained to date. To study the presence of Hg in MSWHS in Paleochori Bay (Milos Island, Greece), sea surface, bottom, pore fluid and hydrothermal gas samples were collected in June of 2017, October of 2018 and July of 2020, and analyzed for Cl, Br, SO4, As, Ca, Fe, K, Mg, Mn, Na, Si, Sr, H2S, unfiltered total Hg (THg), and filtered Hg (Hgdiss). Specific sites were selected for the analysis of volatile elemental Hg (Hgo), dimethylmercury (DMHg), monomethylmercury (MMHg), and Hg in the gas phase (Hggas). Concentrations of THg observed in samples collected from the sea surface were elevated compared to surface samples taken outside Paleochori Bay. The highest surface water concentrations (~10 to 15 pM) were measured in samples collected directly above shallow-water hydrothermal discharge areas. Pore fluids outside Paleochori Bay were significantly lower in THg (0.8 to 8.6 pM) than those taken inside (17.4 to 1511 pM). Porewaters collected from areas with visible gaseous or fluid emission were highly variable but generally elevated in THg concentrations (185 to 5066 pM). Concentrations within gases ranged from 0.7 to 2791 nmol/m3. The vast majority of samples with highly elevated THg (> 100 pM) had low Na/K ratios (< 15), indicative of rapidly rising fluid. Concentrations of Hg0, DMHg, and MMHg were below detection limits in all samples. Bottom substrate type (e.g., rocky vs. sediment covered) likely affected infiltration rates of oxygenated seawater below the sediment-water interface, thereby affecting Hg speciation and removal by precipitation. Flux rates from porewaters compared to those with gaseous emission were high (12.56 to 1088 mol THg/year and 0.37 to 1.85 mol THg/year). Sites with slow gaseous emission rates are hypothesized to have extended subsurface reaction times, resulting in lower Hg concentrations emitted to bottom waters. However, increasing rates of gas emission did not necessarily indicate higher Hg concentrations. The scavenging of Hg in the sediments and advective flux out of Paleochori Bay likely prevent significant accumulations of THg in the water column of Paleochori Bay. The total atmospheric flux from Paleochori Bay using average flux calculations over the entire surface area would contribute 6 mmol Hg/year to the atmosphere. We hypothesize that Hg concentrations within the pore fluids of Paleochori Bay reflect a balance between mixing and precipitation in the subsurface. A three-component mixing system of vapor, brine and seawater determines THg concentrations; however, precipitation due to sulfur cycling, changes in redox conditions and temperature, all play a crucial role in removing Hg from emitted fluids and gases.Wissenschaftlicher ArtikelBand:23367 73 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Geogenic As and Mo groundwater contamination caused by an abundance of domestic supply wellsLacking a connection to a municipal water supply, each household in the municipality of Lithia, approximately 30 km southeast of Tampa, Florida (USA), is responsible for its own supply of drinking water, causing a high-density of private domestic supply wells (DSW) in this area. There, a multilayered aquifer system exists, which can be subdivided into three distinct hydro stratigraphic units, which are, from the top down: the Surficial Aquifer System (SAS), the Intermediate Aquifer System (IAS), and the Upper Floridan Aquifer System (UFA). Despite the relatively small area, the geochemical and hydrogeological setting in Lithia is complex, consisting of: i) extensive cyclical pumping in a municipal well field to the west, ii) large seasonal changes in hydraulic head, ii) multiple aquifers with different hydraulic heads, and iv) a large density of domestic supply wells (DSW). Within the zone of highest As concentrations, there are approximately 100 wells in an area of 2.5 km × 1.5 km. Most of these wells have large open screened intervals, often open to all three aquifers, allowing the downward flow of oxygenated and upward flow of anoxic groundwater. A survey of groundwater quality found that As and Mo concentrations in the DSW were up to 371 μg/L and 4740 μg/L, respectively. To obtain information about the individual aquifers, 5 well clusters with 4 monitoring intervals (approximately 50 m, 65 m, 80 m and 95 m below surface) and 8 push core wells (approximately 9 m below surface) were installed and sampled. In those wells, As and Mo were only elevated in a permeable layer within the IAS at a depth of 50 m. Values were up to 195 μg/L for As and up to 5050 μg/L for Mo. Using the tritium-helium (3H–3He) method, the ages of those samples high in As and Mo were determined to be 40, 30 and 30 years, respectively, while all other samples had ages older than 50 years. This indicated that mixing between young and old groundwater could be responsible for the high As and Mo concentrations. A good negative correlation for the whole data set was also observed between the concentration 3H and δ18O values, which together with hydrogeological modeling confirmed that the increased permeability created by the high density of DSW resulted in flow paths that permitted the perpetual mixing of shallow and deep groundwater. The release of the As and Mo appeared to be a consequence of changes to the physicochemical conditions in the aquifer, either via the introduction of oxygen-rich fluids into the IAS or the mixing of different fluids in the IAS or the introduction of oxygen-depleted fluids into the IAS. While the mobilization of geogenic trace metals is often associated with pumping-induced hydraulic gradient changes, we found that a certain density of multi-aquifer wells can be sufficient to alter hydrologic flow paths and induce the mobilization of geogenic trace metals even in the absence of significant pumping. In Lithia, the DSW effectively increased the local scale permeability of the aquifer, causing the mixing of oxygen-rich surface and deeper anoxic groundwater across a confining unit. Because the alteration to the hydrologic flow paths was a consequence of changes to the physical structure of the aquifer system rather than due to pumping, the alteration is not easily reversible, thus significantly complicating site remediation. Our results provide a cautionary warning of the risks of undue private DSW development in rapidly growing communities.Wissenschaftlicher ArtikelBand:7768 92 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Geochemistry of Champagne Hot Springs shallow hydrothermal vent field and associated sediments, Dominica, Lesser AntillesThe Champagne Hot Springs (CHS) shallow submarine hydrothermal system is located along the submerged flank of the Plat Pays volcanic system on the southwest section of the island of Dominica, Lesser Antilles. We have conducted a detailed geochemical study of the hydrothermal system, with the objectives to investigate the source of the hydrothermal fluids and gases, their effect on sediment and precipitate chemistry, as well as comparing the submarine vent chemistry with nearby on-land hydrothermal vents. Finally, we compare our findings to previous preliminary data from CHS, and compare sediment chemistry to that of average Caribbean sediments. We also report on a newly discovered area of submarine hydrothermal venting, located approximately 40 m to the north of CHS. This area consists of hydrothermally altered areas of sand that contain abundant coatings of hydrous ferric oxides (HFO) on sediment grains. Geochemical and mineralogical analyses of vent waters, pore waters, gases, sediments and precipitates reveal that the vent fluids consist of a mixture of entrained seawater and meteorically derived hydrothermal fluid in varying proportions. Vent fluids are depleted in Br−, SO42−, Cl−, Na+, K+, and Sr2+ relative to ambient seawater. These species are all positively correlated with Mg2+, which is also depleted relative to seawater. Boron, Fe, As, Sb, Mn, Si and Li are all enriched relative to ambient seawater. Pore waters in the hydrothermally altered sand patches have essentially the same chemistry. Mixing between Fe2+ rich vent fluids and seawater causes rapid oxidation of Fe2+ to insoluble Fe3+ and leads to precipitation of HFO at the vent site and subsequent formation of hydrothermally altered sand patches. The elevated concentrations of As and Sb in the precipitates and sediments relative to average Caribbean seafloor sediments reflect adsorption by HFO. Gas samples from the vent site are typical arc-type gases and have both meteoric and magmatic signatures.Wissenschaftlicher ArtikelBand:224Heft:1-361 58 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Arsenic bioaccumulation and biotransformation in deep-sea hydrothermal vent organisms from the PACMANUS hydrothermal field, Manus Basin, Papua New Guinea(Elsevier Science, 2016-11); ; ; ; Hydrothermal vents are often enriched in arsenic, and organisms living in these environments may accumulate high concentrations of this and other trace elements. However, very little research to date has focused on understanding arsenic bioaccumulation and biotransformation in marine organisms at deep-sea vent areas; none to date have focused organisms from back-arc spreading centers. We present for the first time concentration and speciation data for As in vent biota from several hydrothermal vent fields in the eastern Manus basin, a back-arc basin vent field located in the Bismark Sea, western Pacific Ocean. The gastropods Alviniconcha hessleri and Ifremeria nautilei, and the mussel Bathymodiolus manusensis were collected from diffuse venting areas where pH was slightly lower (6.2–6.8), and temperature (26.8–10.5 °C) and arsenic concentrations (169.5–44.0 nM) were higher than seawater. In the tissues of these organisms, the highest total measured As concentrations were in the gills of A. hessleri (5580 mg kg−1), with 721 mg kg−1 and 43 mg kg−1 in digestive gland and muscle, respectively. I. nautilei contained 118 mg kg−1 in the gill, 108 mg kg−1 in the digestive gland and 22 mg kg−1 in the muscle. B. manusensis contained 15.7 mg kg−1 in the digestive gland, followed by 9.8 mg kg-1 and 4.5 mg kg-1 in its gill and muscle tissue, respectively. We interpret the decreasing overall total concentrations in each organism as a function of distance from the source of hydrothermally derived As. The high concentration of arsenic in A. hessleri gills may be associated with elemental sulfur known to occur in this organism as a result of symbiotic microorganisms. Arsenic extracted from freeze-dried A. hessleri tissue was dominated by AsIII and AsV in the digestive gland (82% and 16%, respectively) and gills (97% AsIII, 2.3% AsV), with only 1.8% and 0.2% arsenobetaine (As-Bet) in the digestive gland and gills, respectively. However, the muscle contained substantial amounts of As-Bet (42% As-Bet compared to 48% AsIII and 10% AsV), suggesting As-Bet is a metabolite. Trace arsenosugar (SO4-sug) was observed in digestive gland and gills only. The other snail, I. nautilei, was also dominated by AsIII and AsV in digestive glands (82, 10%) and gills (80, 10%), with 6–9% As-Bet, but its muscle contained 62% As-Bet and 32% AsIII, with 7% trimethylarsoniopropionate (TMAP). Trace dimethylarsinic acid (DMAV) was observed in its gills, and trace TMAP and arsenocholine (AC) was observed in digestive glands. The mussel B. manusensis was dominated by As-Bet in all three tissue types. Digestive gland and gills contained ~22% AsIII, 5–10% AsV, 20–25% DMAV, along with some TMAP and tetramethylarsonium ion (TETRA). However, the muscle contained significantly more As-Bet (91.6%), with the only other species being AsIII (8.4%). Unfortunately, as is often the case in bioaccumulation and biotransformation studies, extraction efficiencies were low, limiting any rigorous interpretation of arsenic biotransformation patterns. Through process of elimination, we suggest that arsenosugars may be synthesized by H2S-oxidizing chemotrophic microbial mats, ultimately leading to the syntheses of As-Bet within vent organisms. However, because As-sugs rarely occur in deep-sea vent organisms, As-Bet, as well as TMAP, AC, and TETRA could also potentially be synthesized directly by the “Edmonds” pathway, the proposed arseno-analog to amino acid formation, without the necessity for arsenosugar formation as an intermediate. Future research should endeavor for more comprehensive extraction of organoarsenicals.Wissenschaftlicher ArtikelBand:11748 80 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Low-temperature alteration of dredged volcanics from the Southern Chile Ridge: additional information about early stages of seafloor weatheringA suite of submarine volcanic rocks from the Southern Chile Ridge has been examined in order to investigate the early stages of low temperature alteration. Alteration in these samples proceeded as follows: (1) Fe-staining on sample surface and along fractures, (2) filling of vesicles with secondary material, (3) breakdown of glassy matrix, (4) breakdown of microcrystalline matrix, and (5) breakdown and replacement of olivine. Plagioclase and pyroxene were sometimes found to be slightly altered along internal fissures. Secondary or alteration phases generally showed high K (3–5 wt.%), Fe (30–70 wt.%) and low Al (<2 wt.%) contents. The most common secondary minerals were Fe-oxyhydroxides, celadonite/Fe-oxyhydroxide (a mixture between celadonite and Fe-oxyhydroxide) and saponite. The formation of secondary minerals is controlled by the oxidation state which is a direct result of seawater to rock ratio. Fe-oxyhydroxides and celadonite/Fe-oxyhydroxide form during oxidative diagenesis, whereas saponite forms during non-oxidative diagenesis. The final alteration products, however, are controlled by external factors, e.g., sedimentation rate or formation of a manganese crust. Ca has been consistently removed, Mg has been added to some rocks and lost from others, and Si has either been removed or remained unaffected. Fe and H2O increases are accompanied by an increase in Fe3+/Fe2+. Wherever increases in K, Rb and Cs were documented, the enrichments are consistently in the order Cs>Rb>K. During initial stages of alteration the behavior of some trace elements such as rare-earth elements (REE), Ba, Zr, Hf, Ta, Nb, and Mo are solely controlled by the precipitation of Mn-rich Fe-oxyhydroxides. The preferred incorporation of Ce into Mn-rich Fe-oxyhydroxides may be a principal factor explaining the Ce depletion in seawater. We conclude that the earliest stages of submarine weathering are controlled by Eh and pH gradients between the rock and seawater. In the absence of a buffer, oxidation of ferrous iron causes a decrease in solution pH.Wissenschaftlicher ArtikelBand:159Heft:1-468 47 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Cadmium in soils and groundwater: A reviewCadmium (Cd) is a non-essential trace element that is widely distributed in the environment. Both geogenic and anthropogenic sources can elevate Cd concentrations in soils and groundwater, which are important for maintaining healthy supplies of food and safe drinking water. Elevated Cd doses are carcinogenic to humans. The WHO Guidelines for Drinking-Water Quality recommend a guideline value for Cd of 3 μg/L. Important anthropogenic Cd sources include mining, atmospheric deposition of combustion emissions, and the use of Cd-containing fertilizers. We document several cases of Cd pollution in soil and groundwater based on worldwide accounts. Besides anthropogenic Cd sources, Cd is also incorporated into sulfides, carbonates, and phosphorites resulting in elevated Cd concentrations in associated rock types. The crustal median Cd content is 0.2 mg/kg. In soils, Cd occurs at concentrations of 0.01 to 1 mg/kg with a worldwide mean of 0.36 mg/kg. Weathering can lead to Cd concentrations up to 5 μg/L in soil water and up to 1 μg/L in groundwater. In aqueous solutions, Cd generally occurs as the divalent Cd2+ and it is mobilized mainly in oxic, acidic conditions. Cadmium sorption is enhanced by the presence of high amounts of hydrous oxides, clay minerals, and organic matter, and its mobility is further influenced by pH, the redox state, and ionic strength of the solution. However, Cd can remain in solution as water-soluble complexes with anions, such as CdCl+ and Cd(SO4)22-, and dissolved organic matter while sorption and precipitation decrease the aqueous concentration of most other heavy metals. As a consequence, Cd is one of the most mobile heavy metals in the environment. The elevated mobilization potential, e.g., through competition and ligand induced desorption, is the reason for faster Cd release from soil into groundwater than other heavy metals. The goal of this study was to present a broad overview of the origin and concentration of Cd in groundwater, and its reaction pathways in aquatic environments. To gain an overview of the hydrochemical behavior of Cd, cases of Cd pollution in soil and groundwater, studies investigating Cd release, and information about the legal framework were compiled.Wissenschaftlicher ArtikelBand:108166 520 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Precipitation of Fe(III) oxyhydroxide deposits from shallow-water hydrothermal fluids in Tutum Bay, Ambitle Island, Papua New GuineaPrevious research on sea floor Fe(III) oxyhydroxide deposits has focused primarily on deep-sea, hydrothermal systems found along volcanically active portions of the mid-ocean ridges and on hydrogenetic deposits formed in deep basins and along continental shelves. There is, however, not much known about their formation in shallow-water settings associated with volcanic islands. The hydrothermal system at Ambitle Island, Papua New Guinea provides an excellent opportunity to study the formation of Fe(III) oxyhydroxides in a shallow-water setting. Precipitation from the hydrothermal solution is caused by mixing with seawater. Based on a 87Sr/86Sr mixing model, the calculated minimum and maximum seawater fractions are approximately 11 and 57%, respectively. Thus, precipitation of Tutum Bay Fe(III) oxyhydroxides takes place at a temperature range between approximately 60 and 93°C. The chemical composition shows low Mn contents (Fe/Mn>600), and elements that are usually enriched in Fe(III) oxyhydroxides, such as Co and V are below crustal abundance and well below their concentrations in island-arc volcanics. Arsenic concentrations, on the other hand, are by two orders of magnitude higher than those in other marine deposits. Rare earth element (REE) concentrations reflect their concentration in the hydrothermal fluids rather than seawater. The crystallinity of the deposits increases with age, as protoferrihydrite is apparently altered to Fe-smectite and hematite, and As-bearing minerals are formed. Contact with seawater, and therefore oxidizing conditions, seems to be the factor increasing the crystallinity.Wissenschaftlicher ArtikelBand:162Heft:180 60