| 1. |
- Herbert, Roger B., 1966-, et al.
(författare)
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Iron isotope fractionation by biogeochemical processes in mine tailings
- 2008
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 42:4, s. 1117-1122
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Tidskriftsartikel (refereegranskat)abstract
- Iron isotope ratios were determined for the pore water, the 1M HCl / 1M hydroxylamine hydrochloride (HAH) – extractable solid phase, and the total extractable solid phase from sulfidic mine tailings in Impoundment 1, Kristineberg mine, northern Sweden. Within the tailings, pyrite oxidation occurs in a distinct Fe – depleted oxidation zone, and the greatest number of Fe(II)-oxidizing bacteria in the profile occur close to the boundary between oxidized and unoxidized tailings. Above the oxidation front in the oxidized tailings, a large iron isotope fractionation (‑1.3‰ to ‑2.4‰) is measured between the pore water and the HAH-extractable solid phase. This isotope fractionation is explained by aqueous Fe(II) – Fe(III) equilibrium, microbial Fe(II) oxidation, and Fe(III) oxyhydroxide precipitation. The data suggests that pyrite in the tailings is enriched in 56Fe relative to Fe-rich silicates in the same material, such that pyrite oxidation results in a decrease in the mean d56Fe value for the bulk tailings in the oxidized zone: a change in isotope composition that is not attributable to isotope fractionation. Iron isotope analyses yield valuable information on iron cycling in mine wastes, and have the potential for becoming a tool for the prediction and control of acid mine drainage.
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| 2. |
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| 3. |
- Mangold, Stefanie, 1981-
(författare)
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Growth and survival of Acidithiobacilli in Acidic, metal rich environments
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Acidithiobacilli are acidophilic microorganisms that play important roles in many natural processes such as acidification of the environment, influencing metal mobility, and impacting on global sulfur and iron cycles. Due to their distinct metabolic properties they can be applied in the industrial extraction of valuable metals. Acidithiobacilli thrive in an environment which is extremely acidic and usually low in organic carbon but highly polluted with metals. In the quest to gain insight into how these microorganisms can thrive in their extreme environment, relevant facets of metabolism, metal resistance, and pH homeostasis were exploredwith the focus on two model organisms,Acidithiobacillus caldus and Acidithiobacillus ferrooxidans. Understanding these fundamental aspects of an acidophilic lifestyle will help to eventually control detrimental effects on the environment due to acidification and metal pollution as well as improving metal extraction utilizing acidophilic microorganisms.Bioinformatics can give information about the genetic capacity of an organism. Likewise, ‘omics’ techniques, such as transcriptomics and proteomics to study gene transcription profiles and differentially expressed proteins canyield insights into general responses as well as giving clues regarding specific mechanisms for adaptation to life in extreme environments. This approach was used to investigate the sulfur metabolism ofAt. caldus which is an important sulfur oxidizer for industrial metal extraction. It was found that sulfur oxidation pathways were diverse within acidithiobacilli and a model of At. caldus sulfur oxidation was proposed. Furthermore, At. ferrooxidans anaerobic sulfur oxidation coupled to ferric iron reduction was studied which can be of importance for industrial processes. It was shown that anaerobic sulfur oxidation was, at least in part, indirectly coupled to ferric iron reduction via sulfide generation. Moreover, metal toxicity and resistance mechanisms in acidophiles are of major interest. Thus, zinc toxicity in three model organisms, At. caldus, Acidimicrobium ferrooxidans, and ‘Ferroplasma acidarmanus’, was explored. An important finding was that the speciation of metals and other chemical influences were of great importance for zinc toxicity in acidophiles. Additionally, the three organisms showed distinct responses to elevated zinc levels. Finally, the response of At. caldus to various suboptimal growth pH was evaluated to gain insights into pH homeostasis mechanisms. The results indicated that At. caldus used acid resistance mechanisms similar to those described for neutrophilic microorganisms. Analysis of fatty acid profiles demonstrated an active modulation of the cyctoplasmic membrane in response to proton concentration, likely resulting in a more rigid membrane at lower pH.
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| 4. |
- Schippers, Axel, et al.
(författare)
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Geomicrobiological and geochemical investigation of pyrite – containing tailings from Kristineberg, Northern Sweden
- 2005
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Ingår i: Proceedings, Securing the Future. Skellefteå, Sweden. ; , s. 866-875
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Konferensbidrag (populärvet., debatt m.m.)abstract
- Pyrite - containing tailings in Impoundment 1 in Kristineberg, northern Sweden were covered in 1996 with a soil cover consisting of 0.3 m compacted till and 1.5 m unspecified till. From the 1940s until 1996, the impoundment was unremediated and sulfide oxidation occurred to depths of 1 m in the tailings. This study focuses on the importance of microorganisms for pyrite oxidation and the release of oxidation products in the remediated tailings. Three cores containing material from the sealing layer and the zones of oxidized and unoxidized tailings were taken in September 2003 and geomicrobiologically and geochemically analyzed. Most-probable-number (MPN) numbers of pyrite-oxidizing, acidophilic Fe(II)-oxidizing microorganisms of the type Acidithiobacillus ferrooxidans were highest with up to 106 cells g-1 dw at the interface between the oxidized and unoxidized tailings, which correlates with maximum metal and sulfate pore water concentrations, a shift of pH and pe, as well as with high potential biological pyrite oxidation rates measured by microcalorimetry at atmospheric oxygen content. The mean proportion of biological pyrite oxidation was 80 % for the oxidized tailings. The potential pyrite oxidation rate for an assumed 0.3 m thick oxidation zone within the oxidized tailings was 4.7 x10-6 mol m-2 s-1 tailings surface (18 kg FeS2 m-2 year-1). The potential chemical pyrite oxidation rate was highest for the unoxidized tailings where Fe(II)-oxidizing microorganisms could not be detected and where the pyrite content was much higher than in the oxidized tailings. The results show that pyrite is biologically oxidized in particular zones of the mine tailings.
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| 5. |
- Turner, Stephanie, et al.
(författare)
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Distinct pattern of nitrogen functional gene abundances in top- and subsoils along a 120,000-year ecosystem development gradient
- 2019
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Ingår i: Soil Biology and Biochemistry. - : Elsevier. - 0038-0717 .- 1879-3428. ; 132, s. 111-119
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Tidskriftsartikel (refereegranskat)abstract
- Soil microorganisms are key players of the nitrogen cycle and relevant for soil development. While the community structure of nitrogen-cycling microorganisms during initial soil development is already well investigated, knowledge about the patterns during long-term ecosystem development is limited. In this study, nitrogen functional genes of ammonia-oxidizers (amoA), nitrate-reducers (narG), and chitin-degraders (chiA) were determined via quantitative PCR and the functional community composition of archaeal ammonia-oxidizers was analyzed via clone libraries and DNA sequencing (amoA) in soil depth profiles along the 120,000-year Franz Josef chronosequence (New Zealand). The results show that absolute nitrogen functional gene abundances change significantly during long-term soil development. In organic layers, narG and chiA gene abundances were highest in young to intermediate-aged soils and then decreased following progressive and retrogressive development of the vegetation. While relative archaeal amoA gene abundance (proportional to total cell counts) decreased in the oldest phosphorus-limited topsoils, relative narG and chiA gene abundances remained constant. In subsoils, archaeal amoA and narG gene abundances also decreased with ecosystem retrogression that coincided with the increasing content of iron and aluminum oxides as well as other clay-sized minerals. In contrast, subsoil chiA gene abundances were hardly affected by soil age. The analysis of the archaeal amoA community revealed a compositional shift during long-term ecosystem development. Our study provides evidence that the community structure of nitrogen-cycling microorganisms in top- and subsoils is significantly affected by long-term ecosystem development and suggests an important role of the mineral phase in subsoils.
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| 6. |
- Turner, Stephanie, et al.
(författare)
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Microbial utilization of mineral-associated nitrogen in soils
- 2017
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Ingår i: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717 .- 1879-3428. ; 104, s. 185-196
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Tidskriftsartikel (refereegranskat)abstract
- In soils, a large portion of organic nitrogen (ON) is associated with minerals and thus, possibly stabilized against biological decay. We therefore tested if mineral-associated N is an important N source for soil microorganisms, and which soil parameters control its bioavailability. Microcosm experiments with mineral-associated organic matter, obtained as heavy fraction (HF) via density fractionation, and bulk soil from mineral topsoil of the Franz Josef chronosequence were conducted for 125 days. We examined the effects of O2 status, soil age (differences in mineralogical properties), as well as cellulose and phosphate additions on the turnover of mineral-associated N. Using a combination of activity measurements and quantitative PCR, microbial N transformation rates and abundances of N-related functional genes (amoA, narG, chiA) were determined. Similar or higher values for microbial N cycling rates and N-related functional abundances in the HF compared to bulk soil indicated that mineral-associated N provides an important bioavailable N source for soil microorganism. The turnover of mineral-associated N was mainly controlled by the O2 status. Besides, soil mineralogical properties significantly affected microbial N cycling and related gene abundances with the effect depending on the N substrate type (ON, NH4+ or NO3−). In contrast, cellulose or phosphate addition hardly enhanced microbial utilization of mineral-associated N. The results of our microcosm study indicate that mineral-associated N is highly bioavailable in mineral topsoils, but effects of the mineral phase differ between N cycling processes.
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