Geochemical Transactions最新文献

{"title":"Accelerated mineral bio-carbonation of coarse residue kimberlite material by inoculation with photosynthetic microbial mats","authors":"Thomas Ray Jones,&nbsp;Jordan Poitras,&nbsp;Emma Gagen,&nbsp;David John Paterson,&nbsp;Gordon Southam","doi":"10.1186/s12932-023-00082-4","DOIUrl":"10.1186/s12932-023-00082-4","url":null,"abstract":"<div><p>Microbiological weathering of coarse residue deposit (CRD) kimberlite produced by the Venetia Diamond Mine, Limpopo, South Africa enhanced mineral carbonation relative to untreated material. Cultures of photosynthetically enriched biofilm produced maximal carbonation conditions when mixed with kimberlite and incubated under near surface conditions. Interestingly, mineral carbonation also occurred in the dark, under water-saturated conditions. The examination of mineralized biofilms in ca. 150 µm-thick-sections using light microscopy, X-ray fluorescence microscopy (XFM) and backscatter electron—scanning electron microscopy-energy dispersive x-ray spectrometry demonstrated that microbiological weathering aided in producing secondary calcium/magnesium carbonates on silicate grain boundaries. Calcium/magnesium sulphate(s) precipitated under vadose conditions demonstrating that evaporites formed upon drying. In this system, mineral carbonation was only observed in regions possessing bacteria, preserved within carbonate as cemented microcolonies. 16S rDNA molecular diversity of bacteria in kimberlite and in natural biofilms growing on kimberlite were dominated by Proteobacteria that are active in nitrogen, phosphorus and sulphur cycling. Cyanobacteria based enrichment cultures provided with nitrogen &amp; phosphorus (nutrients) to enhance growth, possessed increased diversity of bacteria, with Proteobacteria re-establishing themselves as the dominant bacterial lineage when incubated under dark, vadose conditions consistent with natural kimberlite. Overall, 16S rDNA analyses revealed that weathered kimberlite hosts a diverse microbiome consistent with soils, metal cycling and hydrocarbon degradation. Enhanced weathering and carbonate-cemented microcolonies demonstrate that microorganisms are key to mineral carbonation of kimberlite.</p></div>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":"24 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2023-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://geochemicaltransactions.biomedcentral.com/counter/pdf/10.1186/s12932-023-00082-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4650137","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of Ni2+, Zn2+, and Co2+ on green rust transformation to magnetite","authors":"Orion Farr,&nbsp;Evert J. Elzinga,&nbsp;Nathan Yee","doi":"10.1186/s12932-022-00080-y","DOIUrl":"10.1186/s12932-022-00080-y","url":null,"abstract":"<div><p>In this study, we investigated Ni²⁺, Zn²⁺, and Co²⁺ mineralogical incorporation and its effect on green rust transformation to magnetite. Mineral transformation experiments were conducted by heating green rust suspensions at 85 °C in the presence of Ni²⁺, Zn²⁺, or Co²⁺ under strict anoxic conditions. Transmission electron microscopy and powder X-ray diffraction showed the conversion of hexagonal green rust platelets to fine grained cubic magnetite crystals. The addition of Ni²⁺, Zn²⁺, and Co²⁺ resulted in faster rates of mineral transformation. The conversion of green rust to magnetite was concurrent to significant increases in metal uptake, demonstrating a strong affinity for metal sorption/co-precipitation by magnetite. Dissolution ratio curves showed that Ni²⁺, Zn²⁺, and Co²⁺ cations were incorporated into the mineral structure during magnetite crystal growth. The results indicate that the transformation of green rust to magnetite is accelerated by metal impurities, and that magnetite is a highly effective scavenger of trace metals during mineral transformation. The implications for using diagenetic magnetite from green rust precursors as paleo-proxies of Precambrian ocean chemistry are discussed.</p><h3>Graphical Abstract</h3>\u0000 <div><figure><div><div><picture><source><img></source></picture></div></div></figure></div>\u0000 </div>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":"23 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2022-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9798576/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10511929","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemistry and microbiology of tropical serpentine soils in the Santa Elena Ophiolite, a landscape-biogeographical approach","authors":"Agustín F. Solano-Arguedas,&nbsp;Christopher Boothman,&nbsp;Laura Newsome,&nbsp;Richard A. D. Pattrick,&nbsp;Daniel Arguedas-Quesada,&nbsp;Clare H. Robinson,&nbsp;Jonathan R. Lloyd","doi":"10.1186/s12932-022-00079-5","DOIUrl":"10.1186/s12932-022-00079-5","url":null,"abstract":"<div><p>The Santa Elena Ophiolite is a well-studied ultramafic system in Costa Rica mainly comprised of peridotites. Here, tropical climatic conditions promote active laterite formation processes, but the biogeochemistry of the resulting serpentine soils is still poorly understood. The aim of this study was to characterize the soil geochemical composition and microbial community of contrasting landscapes in the area, as the foundation to start exploring the biogeochemistry of metals occurring there. The soils were confirmed as Ni-rich serpentine soils but differed depending on their geographical location within the ophiolite area, showing three serpentine soil types. Weathering processes resulted in <i>mountain</i> soils rich in trace metals such as cobalt, manganese and nickel. The lowlands showed geochemical variations despite sharing similar landscapes: the <i>inner ophiolite lowland</i> soils were more like the surrounding mountain soils rather than the <i>north lowland</i> soils at the border of the ophiolite area, and within the same riparian basin, concentrations of trace metals were higher downstream towards the mangrove area. Microbial community composition reflected the differences in geochemical composition of soils and revealed potential geomicrobiological inputs to local metal biogeochemistry: iron redox cycling bacteria were more abundant in the mountain soils, while more manganese-oxidizing bacteria were found in the lowlands, with the highest relative abundance in the mangrove areas. The fundamental ecological associations recorded in the serpentine soils of the Santa Elena Peninsula, and its potential as a serpentinization endemism hotspot, demonstrate that is a model site to study the biogeochemistry, geomicrobiology and ecology of tropical serpentine areas.</p><h3>Graphical Abstract</h3>\u0000 <div><figure><div><div><picture><source><img></source></picture></div></div></figure></div>\u0000 </div>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":"23 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2022-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9516835/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"40378575","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Improved volume variable cluster model method for crystal-lattice optimization: effect on isotope fractionation factor","authors":"Yan-Fang Wang,&nbsp;Xin-Yue Ji,&nbsp;Le-Cai Xing,&nbsp;Peng-Dong Wang,&nbsp;Jian Liu,&nbsp;Tian-Di Zhang,&nbsp;Hao-Nan Zhao,&nbsp;Hong-Tao He","doi":"10.1186/s12932-022-00078-6","DOIUrl":"10.1186/s12932-022-00078-6","url":null,"abstract":"<div><p>The isotopic fractionation factor and element partition coefficient can be calculated only after the geometric optimization of the molecular clusters is completed. Optimization directly affects the accuracy of some parameters, such as the average bond length, molecular volume, harmonic vibrational frequency, and other thermodynamic parameters. Here, we used the improved volume variable cluster model (VVCM) method to optimize the molecular clusters of a typical oxide, quartz. We documented the average bond length and relative volume change. Finally, we extracted the harmonic vibrational frequencies and calculated the equilibrium fractionation factor of the silicon and oxygen isotopes. Given its performance in geometrical optimization and isotope fractionation factor calculation, we further applied the improved VVCM method to calculate isotope equilibrium fractionation factors of Cd and Zn between the hydroxide (Zn–Al layered double hydroxide), carbonate (cadmium-containing calcite) and their aqueous solutions under superficial conditions. We summarized a detailed procedure and used it to re-evaluate published theoretical results for cadmium-containing hydroxyapatite, emphasizing the relative volume change for all clusters and confirming the optimal point charge arrangement (PCA). The results showed that the average bond length and isotope fractionation factor are consistent with those published in previous studies, and the relative volume changes are considerably lower than the results calculated using the periodic boundary method. Specifically, the average Si–O bond length of quartz was 1.63 Å, and the relative volume change of quartz centered on silicon atoms was  − 0.39%. The average Zn–O bond length in the Zn–Al-layered double hydroxide was 2.10 Å, with a relative volume change of 1.96%. Cadmium-containing calcite had an average Cd–O bond length of 2.28 Å, with a relative volume change of 0.45%. At 298 K, the equilibrium fractionation factors between quartz, Zn–Al-layered double hydroxide, cadmium-containing calcite, and their corresponding aqueous solutions were <span>(Delta ^{30/28} {text{Si}}_{{{text{Qtz-H}}_{4} {text{SiO}}_{4} }} = 2.20{permil} )</span>, <span>(Delta^{18/16} {text{O}}_{ {text{Qtz}}{-} ( {text{H}}_{2} {text{O}} )_{text{n}}} = 36.05{permil})</span>, <span>(Delta^{66/64} {text{Zn}}_{ {text{Zn}} {-} {text{Al LDH-Zn}} ( {text{H}}_{2} {text{O}} )_{text{n}}^{2+}} = 1.12{permil})</span> and <span>(Delta^{114/110} {text{Cd}}_{ {text{(Cd--Cal)-Cd}} ( {text{H}}_{2} {text{O}} )_ {text{n}}^{2 +} } = - 0.26{permil})</span> respectively. These results strongly support the reliability of the improved VVCM method for geometric optimization of molecular clusters.</p></div>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":"23 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2022-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://geochemicaltransactions.biomedcentral.com/counter/pdf/10.1186/s12932-022-00078-6","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4868609","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A single column separation method for barium isotope analysis of geologic and hydrologic materials with complex matrices","authors":"R. M. Matecha,&nbsp;R. C. Capo,&nbsp;B. W. Stewart,&nbsp;R. L. Thompson,&nbsp;J. A. Hakala","doi":"10.1186/s12932-021-00077-z","DOIUrl":"10.1186/s12932-021-00077-z","url":null,"abstract":"<div><p>The increasing significance of barium (Ba) in environmental and geologic research in recent years has led to interest in the application of the Ba isotopic composition as a tracer for natural materials with complex matrices. Most Ba isotope measurement techniques require separation of Ba from the rest of sample prior to analysis. This paper presents a method using readily available materials and disposable columns that effectively separates Ba from a range of geologic and hydrologic materials, including carbonate minerals, silicate rocks, barite, river water, and fluids with high total dissolved solids and organic content such as oil and gas brines, rapidly and without need for an additional cleanup column. The technique involves off-the-shelf columns and cation exchange resin and a two-reagent elution that uses 2.5 N HCl followed by addition of 2.0 N HNO₃. We present data to show that major matrix elements from almost any natural material are separated from Ba in a single column pass, and that the method also effectively reduces or eliminates isobaric interferences from lanthanum and cerium.</p>\u0000 <div><figure><div><div><picture><source><img></source></picture></div></div></figure></div>\u0000 </div>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":"22 1","pages":""},"PeriodicalIF":0.9,"publicationDate":"2021-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8359043/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"39302685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A density functional theory study of Fe(II)/Fe(III) distribution in single layer green rust: a cluster approach","authors":"Weichao Sun,&nbsp;Dominique J. Tobler,&nbsp;Martin P. Andersson","doi":"10.1186/s12932-021-00076-0","DOIUrl":"https://doi.org/10.1186/s12932-021-00076-0","url":null,"abstract":"<p>Green rust (GR) is a potentially important compound for the reduction of heavy metal and organic pollutants in subsurface environment because of its high Fe(II) content, but many details of the actual reaction mechanism are lacking. The reductive capacity distribution within GR is a key to understand how and where the redox reaction occurs and computational chemistry can provide more details about the electronic properties of green rust. We constructed three sizes of cluster models of single layer GR (i.e., without interlayer molecules or ions) and calculated the charge distribution of these structures using density functional theory. We found that the Fe(II) and Fe(III) are distributed unevenly in the single layer GR. Within a certain range of Fe(II)/Fe(III) ratios, the outer iron atoms behave more like Fe(III) and the inner iron atoms behave more like Fe(II). These findings indicate that the interior of GR is more reductive than the outer parts and will provide new information to understand the GR redox interactions.</p>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":"22 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2021-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/s12932-021-00076-0","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4462605","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influences on tidal channel and aquaculture shrimp pond water chemical composition in Southwest Bangladesh","authors":"Matthew Dietrich,&nbsp;John C. Ayers","doi":"10.1186/s12932-021-00074-2","DOIUrl":"https://doi.org/10.1186/s12932-021-00074-2","url":null,"abstract":"<p>Detailed geochemical studies of both major and minor elements in Bangladesh surface waters are sparse, particularly in shrimp aquaculture pond environments. Therefore, water samples from shrimp aquaculture ponds and tidal channels were collected in high precipitation (July) and low precipitation (May) months from 2018–2019 in Southwest Bangladesh and analyzed for complete water chemistry. Selenium (Se) and arsenic (As) were elevated above WHO guidelines in 50% and?~?87% of samples, respectively, but do not show any recognizable spatial patterns. Shrimp pond and tidal channel water compositions in the dry season (May) are similar, illustrating their connectivity and minimal endogenous effects within shrimp ponds. Tidal channels are less saline in July than shrimp ponds still irrigated by tidal channels, suggesting that either farmers limit irrigation to continue farming saltwater shrimp, or the irrigation flux is low and leads to a lag in aquaculture-tidal channel compositional homogenization. δ¹⁸O and δ²H isotopic compositions from samples in May of 2019 reveal tidal channel samples are closer to the local meteoric water line (LMWL) than shrimp pond samples, because of less evaporation. However, evaporation in May shrimp ponds has a minimal effect on water composition, likely because of regular drainage/exchange of pond waters. Dissolved organic carbon (DOC) is positively correlated with both δ¹⁸O and δ²H in shrimp ponds, suggesting that as evaporation increases, DOC becomes enriched. Multiple linear regression reveals that As and Se can be moderately predicted (adjusted R² values between 0.4 and 0.7, p?&lt;?0.01) in surface waters of our study with only 3–4 independent predictor variables (e.g., Ni, V and DOC for Se prediction; Cu, V, Ni and P for As prediction). Thus, this general approach should be followed in other regions throughout the world when measurements for certain hazardous trace elements such as Se and As may be lacking in several samples from a dataset.</p>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":"22 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2021-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/s12932-021-00074-2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5092654","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dissolution and solubility of calcite-rhodochrosite solid solutions [(Ca1-xMnx)CO3] at 25 °C","authors":"Yinian Zhu,&nbsp;Peijie Nong,&nbsp;Nan Mo,&nbsp;Zongqiang Zhu,&nbsp;Huan Deng,&nbsp;Shen Tang,&nbsp;Hongqu Yang,&nbsp;Lihao Zhang,&nbsp;Xingxing Wang","doi":"10.1186/s12932-021-00075-1","DOIUrl":"https://doi.org/10.1186/s12932-021-00075-1","url":null,"abstract":"<p>A complete series of calcite-rhodochrosite solid solutions [(Ca_1-xMn_x)CO₃] are prepared, and their dissolution processes in various water samples are experimentally investigated. The crystal morphologies of the solid solutions vary from blocky spherical crystal aggregates to smaller spheres with an increasing incorporation of Mn in the solids. Regarding dissolution in N₂-degassed water, air-saturated water and CO₂-saturated water at 25?°C, the aqueous Ca and Mn concentrations reach their highest values after 1240–2400?h, 6–12?h and?&lt;?1?h, respectively, and then decrease gradually to a steady state; additionally, the ion activity products (log_IAP) at the final steady state (≈ solubility products in log_<i>K</i>_sp) are estimated to be ??8.46?±?0.06, ??8.44?±?0.10 and ??8.59?±?0.10 for calcite [CaCO₃], respectively, and ??10.25?±?0.08, ??10.26?±?0.10 and ??10.28?±?0.03, for rhodochrosite [MnCO₃], respectively. As X_Mn increases, the log_IAP values decrease from ??8.44?~???8.59 for calcite to ??10.25?~???10.28 for rhodochrosite. The aqueous Mn concentrations increase with an increasing Mn/(Ca?+?Mn) molar ratio (X_Mn) of the (Ca_1-xMn_x)CO₃ solid solutions, while the aqueous Ca concentrations show the highest values at X_Mn?=?0.53–0.63. In the constructed Lippmann diagram of subregular (Ca_1-xMn_x)CO₃ solid solutions, the solids dissolve incongruently, and the data points of the aqueous solutions move progressively up to the Lippmann <i>solutus</i> curve and then along the <i>solutus</i> curve or saturation curve of pure MnCO₃ to the Mn-poor side. The microcrystalline cores of the spherical crystal aggregates are preferentially dissolved to form core hollows while simultaneously precipitating Mn-rich hexagonal prisms.</p>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":"22 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2021-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/s12932-021-00075-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5019604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Trace element partitioning between pyrochlore, microlite, fersmite and silicate melts","authors":"Stephan Klemme,&nbsp;Jasper Berndt","doi":"10.1186/s12932-020-00072-w","DOIUrl":"https://doi.org/10.1186/s12932-020-00072-w","url":null,"abstract":"<p>We present experimentally determined trace element partition coefficients (D) between pyrochlore-group minerals (Ca₂(Nb,Ta)₂O₆(O,F)), Ca fersmite (CaNb₂O₆), and silicate melts. Our data indicate that pyrochlores and fersmite are able to strongly fractionate trace elements during the evolution of SiO₂-undersaturated magmas. Pyrochlore efficiently fractionates Zr and Hf from Nb and Ta, with D_Zr and D_Hf below or equal to unity, and D_Nb and D_Ta significantly above unity. We find that D_Ta pyrochlore-group mineral/silicate melt is always higher than D_Nb, which agrees with the HFSE partitioning of?all other Ti–rich minerals such as perovskite, rutile, ilmenite or Fe-Ti spinel. Our experimental partition coefficients also show that, under oxidizing conditions, D_Th is higher than corresponding D_U and this implies that pyrochlore-group minerals may fractionate U and Th in silicate magmas. The rare earth element (REE) partition coefficients are around unity, only the light REE are compatible in pyrochlore-group minerals, which explains the high?rare earth element concentrations in naturally occurring magmatic pyrochlores.</p>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":"21 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2020-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/s12932-020-00072-w","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4923129","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Immobilization of Cr(VI) by sulphate green rust and sulphidized nanoscale zerovalent iron in sand media: batch and column studies","authors":"Flavia Digiacomo,&nbsp;Dominique J. Tobler,&nbsp;Thomas Held,&nbsp;Thomas Neumann","doi":"10.1186/s12932-020-00073-9","DOIUrl":"https://doi.org/10.1186/s12932-020-00073-9","url":null,"abstract":"<p>Chromate, Cr(VI), contamination in soil and groundwater poses serious threat to living organisms and environmental health worldwide. Sulphate green rust (GR_SO4), a naturally occurring mixed-valent iron layered double hydroxide has shown to be highly effective in the reduction of Cr(VI) to poorly soluble Cr(III), giving promise for its use as reactant for in situ remedial applications. However, little is known about its immobilization efficiency inside porous geological media, such as soils and sediments, where this reactant would ultimately be applied. In this study, we tested the removal of Cr(VI) by GR_SO4 in quartz sand fixed-bed column systems (diameter?×?length?=?1.4?cm?×?11?cm), under anoxic conditions. Cr(VI) removal efficiency (relative to the available reducing equivalents in the added GR_SO4) was determined by evaluating breakthrough curves performed at different inlet Cr(VI) concentrations (0.125–1?mM) which are representative of Cr(VI) concentrations found at contaminated sites, different flow rates (0.25–3?ml/min) and solution pH (4.5, 7 and 9.5). Results showed that (i) increasing Cr(VI) inlet concentration substantially decreased Cr(VI) removal efficiency of GR_SO4, (ii) flow rates had a lower impact on removal efficiencies, although values tended to be lower at higher flow rates, and (iii) Cr(VI) removal was enhanced at acidic pH conditions compared to neutral and alkaline conditions. For comparison, Cr(VI) removal by sulphidized nanoscale zerovalent iron (S-nZVI) in identical column experiments was substantially lower, indicating that S-nZVI reactivity with Cr(VI) is much slower compared to GR_SO4. Overall, GR_SO4 performed reasonably well, even at the highest tested flow rate, showing its versatility and suitability for Cr(VI) remediation applications in high flow environments.</p>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":"21 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2020-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/s12932-020-00073-9","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4563608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}