scholarly journals Temporally and spatially dynamic redox conditions on an upwelling margin: the impact on coupled sedimentary Mo and U isotope systematics, and implications for the Mo-U paleoredox proxy

2021 ◽  
Author(s):  
Zhiwei He ◽  
M.O. Clarkson ◽  
M.B. Andersen ◽  
Corey Archer ◽  
Tim C. Sweere ◽  
...  
Keyword(s):  
Redox Conditions ◽  
The Impact ◽  
Isotope Systematics

Mobilization, release and speciation of arsenic in an As-contaminated gold mine spoil under varied soil redox conditions

2020 ◽  
Author(s):  
Albert Kobina Mensah ◽  
Bernd Marschner ◽  
Jianxu Wang ◽  
Sabry M. Shaheen ◽  
Jörg Rinklebe
Keyword(s):  
Extraction Procedure ◽  
Mineralogical Composition ◽  
Redox Conditions ◽  
Mine Spoil ◽  
Residual Fraction ◽  
Reductive Dissolution ◽  
Gold Mine ◽  
Soil Redox ◽  
Reducing Conditions ◽  
The Impact

<p>Redox-induced release dynamics of arsenic (As) in an abandoned geogenic arsenic-contaminated gold mine spoil in Ghana has never been studied. Therefore, our aim was to investigate the effects of varied soil redox conditions on mobilisation and speciation of As from an abandoned highly contaminated gold mine spoil (with 4,283 mg As/kg soil) using an automated biogeochemical microcosm set-up. We also studied the impact of redox potential (E<sub>H</sub>)-dependent changes of pH, Fe, Mn, Al, S, Cl<sup>-</sup>, SO<sub>4</sub><sup>2-</sup>, DOC, DIC, DC, DN and SUVA on the release dynamics of As. As mineralogical composition and speciation were further determined using a synchrotron-based X-ray absorption spectroscopy (XANES). Linear combination fits of XANES results indicated that scorodite (FeAsSO<sub>4</sub>) and arsenopyrite (FeAsS) are the two major As-containing minerals in the studied mine spoil. Geochemical fractionation using sequential extraction procedure indicated greater proportions of the extracted As in the amorphous iron oxide fraction III (1390.13 mg kg<sup>-1</sup>, 32.5% of the total As) and residual fraction V (2591.67 mg kg<sup>-1</sup>, 60.5% of the total As). Concentrations of dissolved Fe and SUVA were higher during reducing conditions and decreased under oxidising conditions and both showed negative significant relationships with E<sub>H</sub> (E<sub>H </sub>and SUVA: r = -0.76, <em>P <</em> 0.01; E<sub>H</sub> and Fe: r = -0.75). Mobilisation of As was greater under reducing conditions (dissolved As = 136.68 mg/L) than in oxidising environments (dissolved As = 8.06 mg/L). The release of As under low E<sub>H</sub> can be explained by the associated reductive dissolution of Fe oxides, as demonstrated by the high positive significant relationship between Fe and As (r = +0.97, <em>P <</em> 0.01). Dissolved As release dynamics can also be linked to desorption of aromatic carbon compounds on the surfaces of dissolved organic carbon, as demonstrated by the high positive significant correlation between SUVA and As (r = +0.573, <em>P <</em> 0.01). Further, the release dynamics of dissolved As was also affected by changes in pH (r = -0.4, <em>P <</em> 0.05), but were not affected by redox-induced dynamics of Mn, Al, S, Cl<sup>-</sup>, SO<sub>4</sub><sup>2-</sup>, DOC, DIC, DC, DN. We conclude that conditions such as flooding and high rainfall in this contaminated mine spoil could create reducing conditions, leading to reductive dissolution of the arsenopyrite As-bearing primary mineral and may lead to higher As release into the groundwater, translocation into the food chain with potential impacts on human health.</p><p><strong>Keywords</strong>: Arsenopyrite, redox chemistry, arsenic mobilisation, gold mine spoil, reductive and oxidative dissolution.</p>

scholarly journals Understanding preservation of primary signatures in apatite by comparing matrix and zircon-hosted crystals from the Eoarchean Acasta Gneiss Complex (Canada)

2020 ◽  
Author(s):  
Emilie Bruand ◽  
Clementine Antoine ◽  
Martin Guitreau ◽  
Jean-Luc Devidal
Keyword(s):  
Pb Isotope ◽  
Crustal Rocks ◽  
Discriminating Power ◽  
Gneiss Complex ◽  
Apatite Crystals ◽  
Chemical Signatures ◽  
The Matrix ◽  
The Impact ◽  
Isotope Systematics ◽  
Melt Evolution

<p>A novel way to investigate the petrogenesis of ancient poly-metamorphosed terranes is to use zircon as a vessel and study protected mineral inclusions which are sensitive to melt evolution such as apatite. Recent contributions have shown that zircon-hosted apatite inclusions of unmetamorphosed granitoids can provide valuable petrogenetic information about a given pluton and, in turn, represent a way to circumvent effects of metamorphism. Yet, the impact of metamorphism on apatite inclusion has never been studied in detail. To address the issue of chemical and isotopic preservation of primary signals in apatite crystals both in the matrix and armored within zircons, we have studied apatite crystals from four 3.6-4.0 Ga orthogneisses of TTG affinity from the Acasta Gneiss Complex (Canada). Our results demonstrate that U-Th-Pb isotope systematics in matrix apatite crystals are reset at the time of the Wopmay orogen (1.8-1.7 Ga) whereas primary REE signatures were preserved in many crystals. On the contrary, zircon-hosted apatite inclusions all preserved primary REE signatures despite U-Th-Pb isotope systematics giving ages between 1.7 and 4.0 Ga. We interpret the variable resetting of these ages as a consequence of radiation damage accumulation in zircon lattice. Only the most pristine zircon has an apatite inclusion with a concordant age consistent with the magmatic age of the zircon (4.0 Ga). In addition, our results show that apatite crystals from TTG have distinct REE composition from post-Archean granitoids apatites, and that even apatites with reset ages preserved some of the chemical signatures characterizing TTG compositions (e.g. HREE). This capacity to retain primary information together with its discriminating power for granitoids makes apatite a very valuable tool for reconstructing the nature and evolution of ancient crustal rocks through the use of either detrital minerals or detrital-zircon hosting inclusions.</p>

The impact of redox conditions on the rare earth element signature of redoximorphic features in a soil sequence developed from limestone

Geoderma ◽  
2012 ◽  
Vol 170 ◽  
pp. 25-38 ◽  
Author(s):  
Cédric Laveuf ◽  
Sophie Cornu ◽  
Luiz Roberto G. Guilherme ◽  
Annie Guerin ◽  
Farid Juillot
Keyword(s):  
Rare Earth ◽  
Rare Earth Element ◽  
Earth Element ◽  
Redox Conditions ◽  
Redoximorphic Features ◽  
The Impact ◽  
The Rare Earth

The impact of oscillating redox conditions: Arsenic immobilisation in contaminated calcareous floodplain soils

2013 ◽  
Vol 178 ◽  
pp. 254-263 ◽  
Author(s):  
Christopher T. Parsons ◽  
Raoul-Marie Couture ◽  
Enoma O. Omoregie ◽  
Fabrizio Bardelli ◽  
Jean-Marc Greneche ◽  
...  
Keyword(s):  
Redox Conditions ◽  
Floodplain Soils ◽  
The Impact

scholarly journals Versatile soil gas concentration and isotope monitoring: optimization and integration of novel soil gas probes with online trace gas detection

2022 ◽  
Vol 19 (1) ◽  
pp. 165-185
Author(s):  
Juliana Gil-Loaiza ◽  
Joseph R. Roscioli ◽  
Joanne H. Shorter ◽  
Till H. M. Volkmann ◽  
Wei-Ren Ng ◽  
...  
Keyword(s):  
Real Time ◽  
Trace Gases ◽  
Soil Gas ◽  
Redox Conditions ◽  
Trace Gas ◽  
Soil System ◽  
Isotopic Signatures ◽  
Gas Measurements ◽  
The Impact

Abstract. Gas concentrations and isotopic signatures can unveil microbial metabolisms and their responses to environmental changes in soil. Currently, few methods measure in situ soil trace gases such as the products of nitrogen and carbon cycling or volatile organic compounds (VOCs) that constrain microbial biochemical processes like nitrification, methanogenesis, respiration, and microbial communication. Versatile trace gas sampling systems that integrate soil probes with sensitive trace gas analyzers could fill this gap with in situ soil gas measurements that resolve spatial (centimeters) and temporal (minutes) patterns. We developed a system that integrates new porous and hydrophobic sintered polytetrafluoroethylene (sPTFE) diffusive soil gas probes that non-disruptively collect soil gas samples with a transfer system to direct gas from multiple probes to one or more central gas analyzer(s) such as laser and mass spectrometers. Here, we demonstrate the feasibility and versatility of this automated multiprobe system for soil gas measurements of isotopic ratios of nitrous oxide (δ18O, δ15N, and the 15N site preference of N2O), methane, carbon dioxide (δ13C), and VOCs. First, we used an inert silica matrix to challenge probe measurements under controlled gas conditions. By changing and controlling system flow parameters, including the probe flow rate, we optimized recovery of representative soil gas samples while reducing sampling artifacts on subsurface concentrations. Second, we used this system to provide a real-time window into the impact of environmental manipulation of irrigation and soil redox conditions on in situ N2O and VOC concentrations. Moreover, to reveal the dynamics in the stable isotope ratios of N2O (i.e., 14N14N16O, 14N15N16O, 15N14N16O, and 14N14N18O), we developed a new high-precision laser spectrometer with a reduced sample volume demand. Our integrated system – a tunable infrared laser direct absorption spectrometry (TILDAS) in parallel with Vocus proton transfer reaction mass spectrometry (PTR-MS), in line with sPTFE soil gas probes – successfully quantified isotopic signatures for N2O, CO2, and VOCs in real time as responses to changes in the dry–wetting cycle and redox conditions. Broadening the collection of trace gases that can be monitored in the subsurface is critical for monitoring biogeochemical cycles, ecosystem health, and management practices at scales relevant to the soil system.

The impact of variable temperatures on the redox conditions and the behaviour of pharmaceutical residues during artificial recharge

2006 ◽  
Vol 328 (1-2) ◽  
pp. 141-156 ◽  
Author(s):  
G. Massmann ◽  
J. Greskowiak ◽  
U. Dünnbier ◽  
S. Zuehlke ◽  
A. Knappe ◽  
...  
Keyword(s):  
Artificial Recharge ◽  
Redox Conditions ◽  
Pharmaceutical Residues ◽  
The Impact

scholarly journals EMP and SIMS studies on Mn/Ca and Fe/Ca systematics in benthic foraminifera from the Peruvian OMZ: a contribution to the identification of potential redox proxies and the impact of cleaning protocols

2012 ◽  
Vol 9 (1) ◽  
pp. 341-359 ◽  
Author(s):  
N. Glock ◽  
A. Eisenhauer ◽  
V. Liebetrau ◽  
M. Wiedenbeck ◽  
C. Hensen ◽  
...  
Keyword(s):  
Water Depth ◽  
Benthic Foraminifera ◽  
Sampling Site ◽  
Redox Conditions ◽  
Sediment Surface ◽  
Test Surface ◽  
Pore Waters ◽  
Rich Phase ◽  
Icp Ms ◽  
The Impact

Abstract. In this study we present an initial dataset of Mn/Ca and Fe/Ca ratios in tests of benthic foraminifera from the Peruvian oxygen minimum zone (OMZ) determined with SIMS. These results are a contribution to a better understanding of the proxy potential of these elemental ratios for ambient redox conditions. Foraminiferal tests are often contaminated by diagenetic coatings, like Mn rich carbonate- or Fe and Mn rich (oxyhydr)oxide coatings. Thus, it is substantial to assure that the cleaning protocols are efficient or that spots chosen for microanalyses are free of contaminants. Prior to the determination of the element/Ca ratios, the distributions of several elements (Ca, Mn, Fe, Mg, Ba, Al, Si, P and S) in tests of the shallow infaunal species Uvigerina peregrina and Bolivina spissa were mapped with an electron microprobe (EMP). To visualize the effects of cleaning protocols uncleaned and cleaned specimens were compared. The cleaning protocol included an oxidative cleaning step. An Fe rich phase was found on the inner test surface of uncleaned U. peregrina specimens. This phase was also enriched in Al, Si, P and S. A similar Fe rich phase was found at the inner test surface of B. spissa. Specimens of both species treated with oxidative cleaning show the absence of this phase. Neither in B. spissa nor in U. peregrina were any hints found for diagenetic (oxyhydr)oxide or carbonate coatings. Mn/Ca and Fe/Ca ratios of single specimens of B. spissa from different locations have been determined by secondary ion mass spectrometry (SIMS). Bulk analyses using solution ICP-MS of several samples were compared to the SIMS data. The difference between SIMS analyses and ICP-MS bulk analyses from the same sampling sites was 14.0–134.8 μmol mol−1 for the Fe/Ca and 1.68(±0.41) μmol mol−1 for the Mn/Ca ratios. This is in the same order of magnitude as the variability inside single specimens determined with SIMS at these sampling sites (1σ[Mn/Ca] = 0.35–2.07 μmol mol−1; 1σ[Fe/Ca] = 93.9–188.4 μmol mol−1). The Mn/Ca ratios in the calcite were generally relatively low (2.21–9.93 μmol mol−1) but in the same magnitude and proportional to the surrounding pore waters (1.37–6.67 μmol mol−1). However, the Fe/Ca ratios in B. spissa show a negative correlation to the concentrations in the surrounding pore waters. Lowest foraminiferal Fe/Ca ratios (87.0–101.0 μmol mol−1) were found at 465 m water depth, a location with a strong sharp Fe peak in the pore water next to the sediment surface and respectively, high Fe concentrations in the surrounding pore waters. Previous studies found no living specimens of B. spissa at this location. All these facts hint that the analysed specimens already were dead before the Fe flux started and the sampling site just recently turned anoxic due to fluctuations of the lower boundary of the OMZ near the sampling site (465 m water depth). Summarized Mn/Ca and Fe/Ca ratios are potential proxies for redox conditions, if cleaning protocols are carefully applied. The data presented here may be rated as base for the still pending detailed calibration.

Sorption and Degradation of Selected Pharmaceuticals in Controlled Laboratory Column Experiments

2020 ◽  
Author(s):  
Marleen Schübl ◽  
Aleksandra Kiecak ◽  
Christine Stumpp
Keyword(s):  
Dissolved Oxygen ◽  
Microbial Activity ◽  
Reactive Transport ◽  
Sandy Loam ◽  
Redox Conditions ◽  
Column Experiments ◽  
Pharmaceutically Active Compounds ◽  
Active Compounds ◽  
Transport Behavior ◽  
The Impact

<p>Pharmaceutically active compounds have increasingly been detected in groundwater worldwide. Despite constituting a major risk for ecosystems and human health, their fate in the environment has still not been thoroughly investigated. This study characterizes the transport behavior of five selected pharmaceutically active compounds (antipyrine, atenolol, caffeine, carbamazepine and sulfamethoxazole) in two sediments (coarse quartzsand and sandy loam) using column experiments with long-term injection of spiked groundwater accompanied by monitoring of microbial activity in the columns. Transport parameters were estimated using an analytical reactive transport model. When five selected compounds were injected simultaneously, transport behavior of antipyrine, carbamazepine and the antibiotic sulfamethoxazole were similar to the conservative tracer in both sediments and under varying redox conditions. During the entire duration of the experiments of about two months no degradation was observed, thus showing the low potential for natural attenuation. Atenolol and caffeine were subject to retardation which was significantly stronger in the sandy loam sediment compared to the coarse quartzsand. This was attributed to higher contents in clay and organic carbon in sandy loam. Biodegradation of caffeine was observed in three out of four non-sterilized settings after an adaption period of 120 to 420 hours and was dependent on the presence of dissolved oxygen. Atenolol was biologically degraded in the coarse quartzsand while the type of degradation remained unclear in the sandy loam sediment. The identification of biodegradation processes was supported by monitoring of intracellular adenosine triphosphate (ATP<sub>itc</sub>) as a measure for microbial activity. ATP<sub>itc</sub> was present in varying concentrations in all sediments with higher concentrations when degradation of pharmaceuticals, especially caffeine, was observed. When only caffeine and sulfamethoxazole were injected simultaneously, sulfamethoxazole was degraded while caffeine was not. The latter seems to be influenced by low concentrations in dissolved oxygen rather than the presence of the antibiotic sulfamethoxazole. Results of these experiments emphasize the impact of sediment type and redox conditions on pharmaceutical transport as well as the effect of combination and variety of pharmaceuticals that are released together into the environment.</p>

Sign in / Sign up

Export Citation Format

Share Document