Pub Date : 2020-08-14DOI: 10.1186/s12932-020-00073-9
Flavia Digiacomo, Dominique J. Tobler, Thomas Held, Thomas Neumann
Chromate, Cr(VI), contamination in soil and groundwater poses serious threat to living organisms and environmental health worldwide. Sulphate green rust (GRSO4), 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 GRSO4 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 GRSO4) 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 GRSO4, (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 GRSO4. Overall, GRSO4 performed reasonably well, even at the highest tested flow rate, showing its versatility and suitability for Cr(VI) remediation applications in high flow environments.
{"title":"Immobilization of Cr(VI) by sulphate green rust and sulphidized nanoscale zerovalent iron in sand media: batch and column studies","authors":"Flavia Digiacomo, Dominique J. Tobler, Thomas Held, 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<sub>SO4</sub>), 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<sub>SO4</sub> 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<sub>SO4</sub>) 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<sub>SO4</sub>, (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<sub>SO4</sub>. Overall, GR<sub>SO4</sub> 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":null,"pages":null},"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}
Pub Date : 2020-04-22DOI: 10.1186/s12932-020-00071-x
Sima Bargrizan, Ronald J. Smernik, Luke M. Mosley
{"title":"Correction to: Constraining the carbonate system in soils via testing the internal consistency of pH, pCO2 and alkalinity measurements","authors":"Sima Bargrizan, Ronald J. Smernik, Luke M. Mosley","doi":"10.1186/s12932-020-00071-x","DOIUrl":"https://doi.org/10.1186/s12932-020-00071-x","url":null,"abstract":"","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2020-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/s12932-020-00071-x","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4844648","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}
Pub Date : 2020-04-17DOI: 10.1186/s12932-020-00070-y
Young-Shin Jun, Mengqiang Zhu, Derek Peak
{"title":"Frontiers and advances in environmental soil chemistry: a special issue in honor of Prof. Donald L. Sparks","authors":"Young-Shin Jun, Mengqiang Zhu, Derek Peak","doi":"10.1186/s12932-020-00070-y","DOIUrl":"https://doi.org/10.1186/s12932-020-00070-y","url":null,"abstract":"","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2020-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/s12932-020-00070-y","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4669083","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}
Pub Date : 2020-04-01DOI: 10.1186/s12932-020-00068-6
Donald L. Sparks
{"title":"A golden period for environmental soil chemistry","authors":"Donald L. Sparks","doi":"10.1186/s12932-020-00068-6","DOIUrl":"https://doi.org/10.1186/s12932-020-00068-6","url":null,"abstract":"","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2020-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/s12932-020-00068-6","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4000653","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}
Pub Date : 2020-03-30DOI: 10.1186/s12932-020-00069-5
Sima Bargrizan, Ronald J. Smernik, Luke M. Mosley
Inorganic carbon exists in various dissolved, gaseous and solid phase forms in natural waters and soils. It is important to accurately measure and model these forms to understand system responses to global climate change. The carbonate system can, in theory, be fully constrained and modelled by measuring at least two out of the following four parameters: partial pressure (pCO2), total alkalinity (TA), pH and dissolved inorganic carbon (DIC) but this has not been demonstrated in soils. In this study, this “internal consistency” of the soil carbonate system was examined by predicting pH of soil extracts from laboratory measurement of TA through alkalinity titration for solutions in which pCO2 was fixed through equilibrating the soil solution with air with a known pCO2. This predicted pH (pHCO2) was compared with pH measured on the same soil extracts using spectrophotometric and glass electrode methods (pHspec and pHelec). Discrepancy between measured and calculated pH was within 0.00–0.1 pH unit for most samples. However, more deviation was observed for those sample with low alkalinity (≤?0.5?meq L?1). This is likely attributable to an effect of dissolved organic matter, which can contribute alkalinity not considered in the thermodynamic carbonate model calculations; further research is required to resolve this problem. The effects of increasing soil pCO2 was modelled to illustrate how internally consistent models can be used to predict risks of pH declines and carbonate mineral dissolution in some soils.
{"title":"Constraining the carbonate system in soils via testing the internal consistency of pH, pCO2 and alkalinity measurements","authors":"Sima Bargrizan, Ronald J. Smernik, Luke M. Mosley","doi":"10.1186/s12932-020-00069-5","DOIUrl":"https://doi.org/10.1186/s12932-020-00069-5","url":null,"abstract":"<p>Inorganic carbon exists in various dissolved, gaseous and solid phase forms in natural waters and soils. It is important to accurately measure and model these forms to understand system responses to global climate change. The carbonate system can, in theory, be fully constrained and modelled by measuring at least two out of the following four parameters: partial pressure (pCO<sub>2</sub>), total alkalinity (TA), pH and dissolved inorganic carbon (DIC) but this has not been demonstrated in soils. In this study, this “internal consistency” of the soil carbonate system was examined by predicting pH of soil extracts from laboratory measurement of TA through alkalinity titration for solutions in which pCO<sub>2</sub> was fixed through equilibrating the soil solution with air with a known pCO<sub>2</sub>. This predicted pH (pH<sub>CO2</sub>) was compared with pH measured on the same soil extracts using spectrophotometric and glass electrode methods (pH<sub>spec and</sub> pH<sub>elec</sub>). Discrepancy between measured and calculated pH was within 0.00–0.1 pH unit for most samples. However, more deviation was observed for those sample with low alkalinity (≤?0.5?meq L<sup>?1</sup>). This is likely attributable to an effect of dissolved organic matter, which can contribute alkalinity not considered in the thermodynamic carbonate model calculations; further research is required to resolve this problem. The effects of increasing soil pCO<sub>2</sub> was modelled to illustrate how internally consistent models can be used to predict risks of pH declines and carbonate mineral dissolution in some soils.</p>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2020-03-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/s12932-020-00069-5","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5162614","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}
Pub Date : 2020-02-17DOI: 10.1186/s12932-020-00067-7
Yunbin Jiang, Fengmin Zhang, Chao Ren, Wei Li
Solution 31P nuclear magnetic resonance (NMR) spectroscopy has been widely applied to analyze the speciation of soil organic P; however, this time-consuming technique suffers from a low analytical efficiency, because of the lack of fundamental information such as the spin–lattice relaxation (T1) of 31P nucleus for model P compounds. In this study, we for the first time determined the T1 values of twelve typical soil organic P compounds using the inversion recovery method. Furthermore, we examined the effect of co-existing paramagnetic ions (e.g., Fe3+ and Mn2+) on the reduction of the T1 values of these compounds. Without the addition of paramagnetic ions, the T1 values of twelve model P compounds ranged from 0.61?s for phytic acid to 9.65?s for orthophosphate. In contrast, the presence of paramagnetic ion significantly shortened the T1 values of orthophosphate, pyrophosphate, and phytic acid to 1.29, 1.26, and 0.07?s, respectively, except that of deoxyribonucleic acid (DNA) remaining unchanged. Additionally, we evaluated the feasibility of improving the efficiency of quantitative 31P NMR analysis via addition of paramagnetic ion. Results show that, after an addition of 50?mg L?1 paramagnetic ions, 31P NMR measurement can be 3 times more efficient, attributed to the reduced T1 and the corresponding recycle delay.
溶液31P核磁共振(NMR)谱已广泛应用于分析土壤有机P的形态;然而,由于缺乏模型P化合物31P核的自旋晶格弛豫(T1)等基本信息,这种耗时的技术存在分析效率低的问题。本研究首次利用反演恢复方法测定了12种典型土壤有机磷化合物的T1值。此外,我们还研究了共存的顺磁离子(如Fe3+和Mn2+)对这些化合物T1值降低的影响。在未加入顺磁离子的情况下,12种模型P化合物的T1值在0.61?S表示植酸到9.65?S代表正磷酸盐。顺磁离子的存在显著缩短了正磷酸盐、焦磷酸盐和植酸的T1值,分别为1.29、1.26和0.07?除脱氧核糖核酸(DNA)保持不变外,其余分别为s。此外,我们还评估了通过添加顺磁离子来提高31P核磁共振定量分析效率的可行性。结果表明,加50?mg L ?1顺磁离子时,31P的核磁共振测量效率可提高3倍,这归功于T1的降低和相应的循环延迟。
{"title":"Improvement of quantitative solution 31P NMR analysis of soil organic P: a study of spin–lattice relaxation responding to paramagnetic ions","authors":"Yunbin Jiang, Fengmin Zhang, Chao Ren, Wei Li","doi":"10.1186/s12932-020-00067-7","DOIUrl":"https://doi.org/10.1186/s12932-020-00067-7","url":null,"abstract":"<p>Solution <sup>31</sup>P nuclear magnetic resonance (NMR) spectroscopy has been widely applied to analyze the speciation of soil organic P; however, this time-consuming technique suffers from a low analytical efficiency, because of the lack of fundamental information such as the spin–lattice relaxation (<i>T</i><sub>1</sub>) of <sup>31</sup>P nucleus for model P compounds. In this study, we for the first time determined the <i>T</i><sub>1</sub> values of twelve typical soil organic P compounds using the inversion recovery method. Furthermore, we examined the effect of co-existing paramagnetic ions (e.g., Fe<sup>3+</sup> and Mn<sup>2+</sup>) on the reduction of the <i>T</i><sub>1</sub> values of these compounds. Without the addition of paramagnetic ions, the <i>T</i><sub>1</sub> values of twelve model P compounds ranged from 0.61?s for phytic acid to 9.65?s for orthophosphate. In contrast, the presence of paramagnetic ion significantly shortened the <i>T</i><sub>1</sub> values of orthophosphate, pyrophosphate, and phytic acid to 1.29, 1.26, and 0.07?s, respectively, except that of deoxyribonucleic acid (DNA) remaining unchanged. Additionally, we evaluated the feasibility of improving the efficiency of quantitative <sup>31</sup>P NMR analysis via addition of paramagnetic ion. Results show that, after an addition of 50?mg L<sup>?1</sup> paramagnetic ions, <sup>31</sup>P NMR measurement can be 3 times more efficient, attributed to the reduced <i>T</i><sub>1</sub> and the corresponding recycle delay.</p>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2020-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/s12932-020-00067-7","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4678134","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}
Pub Date : 2020-02-14DOI: 10.1186/s12932-020-00066-8
Andrew N. Thomas, Elisabeth Eiche, Jörg Göttlicher, Ralph Steininger, Liane G. Benning, Helen M. Freeman, Dominique J. Tobler, Marco Mangayayam, Knud Dideriksen, Thomas Neumann
Chromium contamination is a serious environmental issue in areas affected by leather tanning and metal plating, and green rust sulfate has been tested extensively as a potential material for in situ chemical reduction of hexavalent chromium in groundwater. Reported products and mechanisms for the reaction have varied, most likely because of green rust’s layered structure, as reduction at outer and interlayer surfaces might produce different reaction products with variable stabilities. Based on studies of Cr(III) oxidation by biogenic Mn (IV) oxides, Cr mobility in oxic soils is controlled by the solubility of the Cr(III)-bearing phase. Therefore, careful engineering of green rust properties, i.e., crystal/particle size, morphology, structure, and electron availability, is essential for its optimization as a remediation reagent. In the present study, pure green rust sulfate and green rust sulfate with Al, Mg and Zn substitutions were synthesized and reacted with identical chromate (CrO42?) solutions. The reaction products were characterized by X-ray diffraction, pair distribution function analysis, X-ray absorption spectroscopy and transmission electron microscopy and treated with synthetic δ-MnO2 to assess how easily Cr(III) in the products could be oxidized. It was found that Mg substitution had the most beneficial effect on Cr lability in the product. Less than 2.5% of the Cr(III) present in the reacted Mg-GR was reoxidized by δ-MnO2 within 14?days, and the particle structure and Cr speciation observed during X-ray scattering and absorption analyses of this product suggested that Cr(VI) was reduced in its interlayer. Reduction in the interlayer lead to the linkage of newly-formed Cr(III) to hydroxyl groups in the adjacent octahedral layers, which resulted in increased structural coherency between these layers, distinctive rim domains, sequestration of Cr(III) in insoluble Fe oxide bonding environments resistant to reoxidation and partial transformation to Cr(III)-substituted feroxyhyte. Based on the results of this study of hexavalent chromium reduction by green rust sulfate and other studies, further improvements can also be made to this remediation technique by reacting chromate with a large excess of green rust sulfate, which provides excess Fe(II) that can catalyze transformation to more crystalline iron oxides, and synthesis of the reactant under alkaline conditions, which has been shown to favor chromium reduction in the interlayer of Fe(II)-bearing phyllosilicates.
{"title":"Effects of metal cation substitution on hexavalent chromium reduction by green rust","authors":"Andrew N. Thomas, Elisabeth Eiche, Jörg Göttlicher, Ralph Steininger, Liane G. Benning, Helen M. Freeman, Dominique J. Tobler, Marco Mangayayam, Knud Dideriksen, Thomas Neumann","doi":"10.1186/s12932-020-00066-8","DOIUrl":"https://doi.org/10.1186/s12932-020-00066-8","url":null,"abstract":"<p>Chromium contamination is a serious environmental issue in areas affected by leather tanning and metal plating, and green rust sulfate has been tested extensively as a potential material for in situ chemical reduction of hexavalent chromium in groundwater. Reported products and mechanisms for the reaction have varied, most likely because of green rust’s layered structure, as reduction at outer and interlayer surfaces might produce different reaction products with variable stabilities. Based on studies of Cr(III) oxidation by biogenic Mn (IV) oxides, Cr mobility in oxic soils is controlled by the solubility of the Cr(III)-bearing phase. Therefore, careful engineering of green rust properties, i.e., crystal/particle size, morphology, structure, and electron availability, is essential for its optimization as a remediation reagent. In the present study, pure green rust sulfate and green rust sulfate with Al, Mg and Zn substitutions were synthesized and reacted with identical chromate (CrO<sub>4</sub><sup>2?</sup>) solutions. The reaction products were characterized by X-ray diffraction, pair distribution function analysis, X-ray absorption spectroscopy and transmission electron microscopy and treated with synthetic δ-MnO<sub>2</sub> to assess how easily Cr(III) in the products could be oxidized. It was found that Mg substitution had the most beneficial effect on Cr lability in the product. Less than 2.5% of the Cr(III) present in the reacted Mg-GR was reoxidized by δ-MnO<sub>2</sub> within 14?days, and the particle structure and Cr speciation observed during X-ray scattering and absorption analyses of this product suggested that Cr(VI) was reduced in its interlayer. Reduction in the interlayer lead to the linkage of newly-formed Cr(III) to hydroxyl groups in the adjacent octahedral layers, which resulted in increased structural coherency between these layers, distinctive rim domains, sequestration of Cr(III) in insoluble Fe oxide bonding environments resistant to reoxidation and partial transformation to Cr(III)-substituted feroxyhyte. Based on the results of this study of hexavalent chromium reduction by green rust sulfate and other studies, further improvements can also be made to this remediation technique by reacting chromate with a large excess of green rust sulfate, which provides excess Fe(II) that can catalyze transformation to more crystalline iron oxides, and synthesis of the reactant under alkaline conditions, which has been shown to favor chromium reduction in the interlayer of Fe(II)-bearing phyllosilicates.</p>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2020-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/s12932-020-00066-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4570760","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}
Pub Date : 2020-01-04DOI: 10.1186/s12932-019-0065-z
Ozren Hasan, Slobodan Miko, Nikolina Ilijanić, Dea Brunović, Željko Dedić, Martina Šparica Miko, Zoran Peh
The study presented in this work emerged as a result of a multiyear regional geochemical survey based on low-density topsoil sampling and the ensuing geochemical atlas of Croatia. This study focuses on the Dinaric part of Croatia to expound the underlying mechanisms controlling the mobilities and variations in distribution of potentially harmful elements as observed from different environmental angles. Although serious environmental degradation of the vulnerable karst soil landscapes was expected to occur chiefly through the accumulation of various heavy metals, the most acute threat materialized through the soil acidification (Al-toxicity) affecting the entire Dinaric karst area. This picture surfaced from the analysis of all three investigated discriminant function models employing the abovementioned environmental criteria selected autonomously with respect to the evaluated soil geochemistry, namely, geologic setting, regional placement and land use. These models are presented by not only the characteristic discriminant-function diagrams but also a set of appropriate mathematically derived geochemical maps disclosing the allocations of potential threats to the karst soil landscapes posed by soil acidity.
{"title":"Discrimination of topsoil environments in a karst landscape: an outcome of a geochemical mapping campaign","authors":"Ozren Hasan, Slobodan Miko, Nikolina Ilijanić, Dea Brunović, Željko Dedić, Martina Šparica Miko, Zoran Peh","doi":"10.1186/s12932-019-0065-z","DOIUrl":"https://doi.org/10.1186/s12932-019-0065-z","url":null,"abstract":"<p>The study presented in this work emerged as a result of a multiyear regional geochemical survey based on low-density topsoil sampling and the ensuing geochemical atlas of Croatia. This study focuses on the Dinaric part of Croatia to expound the underlying mechanisms controlling the mobilities and variations in distribution of potentially harmful elements as observed from different environmental angles. Although serious environmental degradation of the vulnerable karst soil landscapes was expected to occur chiefly through the accumulation of various heavy metals, the most acute threat materialized through the soil acidification (Al-toxicity) affecting the entire Dinaric karst area. This picture surfaced from the analysis of all three investigated discriminant function models employing the abovementioned environmental criteria selected autonomously with respect to the evaluated soil geochemistry, namely, geologic setting, regional placement and land use. These models are presented by not only the characteristic discriminant-function diagrams but also a set of appropriate mathematically derived geochemical maps disclosing the allocations of potential threats to the karst soil landscapes posed by soil acidity.</p>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2020-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/s12932-019-0065-z","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4161058","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}
Pub Date : 2019-09-05DOI: 10.1186/s12932-019-0064-0
Mark Rollog, Nigel J. Cook, Paul Guagliardo, Kathy Ehrig, Sarah E. Gilbert, Matt Kilburn
Production of radionuclide-free copper concentrates is dependent on understanding and controlling the deportment of daughter radionuclides (RNs) produced from 238U decay, specifically 226Ra, 210Pb, and 210Po. Sulfuric acid leaching is currently employed in the Olympic Dam processing plant (South Australia) to remove U and fluorine from copper concentrates prior to smelting but does not adequately remove the aforementioned RN. Due to chemical similarities between lead and alkaline earth metals (including Ra), two sets of experiments were designed to understand solution interactions between Sr, Ba, and Pb at various conditions. Nanoscale secondary ion mass spectrometry (NanoSIMS) isotopic spatial distribution maps and laser ablation inductively coupled-plasma mass spectrometry transects were performed on laboratory-grown crystals of baryte, celestite, and anglesite which had been exposed to different solutions under different pH and reaction time conditions. Analysis of experimental products reveals three uptake mechanisms: overgrowth of nearly pure SrSO4 and PbSO4 on baryte; incorporation of minor of Pb and Ba into celestite due to diffusion; and extensive replacement of Pb by Sr (and less extensive replacement of Pb by Ba) in anglesite via coupled dissolution-reprecipitation reactions. The presence of H2SO4 either enhanced or inhibited these reactions. Kinetic modelling supports the experimental results, showing potential for extrapolating the (Sr, Ba, Pb)SO4 system to encompass RaSO4. Direct observation of grain-scale element distributions by nanoSIMS aids understanding of the controlling conditions and mechanisms of replacement that may be critical steps for Pb and Ra removal from concentrates by allowing construction of a cationic replacement scenario targeting Pb or Ra, or ideally all insoluble sulfates. Experimental results provide a foundation for further investigation of RN uptake during minerals processing, especially during acid leaching. The new evidence enhances understanding of micro- to nanoscale chemical interactions and not only aids determination of where radionuclides reside during each processing stage but also guides development of flowsheets targeting their removal.
{"title":"Intermobility of barium, strontium, and lead in chloride and sulfate leach solutions","authors":"Mark Rollog, Nigel J. Cook, Paul Guagliardo, Kathy Ehrig, Sarah E. Gilbert, Matt Kilburn","doi":"10.1186/s12932-019-0064-0","DOIUrl":"https://doi.org/10.1186/s12932-019-0064-0","url":null,"abstract":"<p>Production of radionuclide-free copper concentrates is dependent on understanding and controlling the deportment of daughter radionuclides (RNs) produced from <sup>238</sup>U decay, specifically <sup>226</sup>Ra, <sup>210</sup>Pb, and <sup>210</sup>Po. Sulfuric acid leaching is currently employed in the Olympic Dam processing plant (South Australia) to remove U and fluorine from copper concentrates prior to smelting but does not adequately remove the aforementioned RN. Due to chemical similarities between lead and alkaline earth metals (including Ra), two sets of experiments were designed to understand solution interactions between Sr, Ba, and Pb at various conditions. Nanoscale secondary ion mass spectrometry (NanoSIMS) isotopic spatial distribution maps and laser ablation inductively coupled-plasma mass spectrometry transects were performed on laboratory-grown crystals of baryte, celestite, and anglesite which had been exposed to different solutions under different pH and reaction time conditions. Analysis of experimental products reveals three uptake mechanisms: overgrowth of nearly pure SrSO<sub>4</sub> and PbSO<sub>4</sub> on baryte; incorporation of minor of Pb and Ba into celestite due to diffusion; and extensive replacement of Pb by Sr (and less extensive replacement of Pb by Ba) in anglesite via coupled dissolution-reprecipitation reactions. The presence of H<sub>2</sub>SO<sub>4</sub> either enhanced or inhibited these reactions. Kinetic modelling supports the experimental results, showing potential for extrapolating the (Sr, Ba, Pb)SO<sub>4</sub> system to encompass RaSO<sub>4</sub>. Direct observation of grain-scale element distributions by nanoSIMS aids understanding of the controlling conditions and mechanisms of replacement that may be critical steps for Pb and Ra removal from concentrates by allowing construction of a cationic replacement scenario targeting Pb or Ra, or ideally all insoluble sulfates. Experimental results provide a foundation for further investigation of RN uptake during minerals processing, especially during acid leaching. The new evidence enhances understanding of micro- to nanoscale chemical interactions and not only aids determination of where radionuclides reside during each processing stage but also guides development of flowsheets targeting their removal.</p>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2019-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/s12932-019-0064-0","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4230495","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}
Pub Date : 2019-05-24DOI: 10.1186/s12932-019-0063-1
Rodrigo C. Pereira, Pedro R. Anizelli, Eduardo Di Mauro, Daniel F. Valezi, Antonio Carlos S. da Costa, Cássia Thaïs B. V. Zaia, Dimas A. M. Zaia
Although, glyphosate (N-(phosphonomethyl) glycine) is one of the most widely used herbicides in the world, its interaction with poorly crystalline iron oxides, such as ferrihydrite, is not well studied. In this research, we examined the adsorption of glyphosate onto ferrihydrite using infrared spectroscopy (FT-IR), electron paramagnetic resonance spectroscopy (EPR), adsorption kinetic models and adsorption isotherm models. The effect of pH and sodium chloride concentration on the adsorption of glyphosate onto ferrihydrite as well as the effect of extractors (CaCl2 0.010?mol?L?1 and Mehlich) on the desorption of glyphosate were also evaluated. There are two important findings described in this work. First, 84% of adsorbed glyphosate strongly interacted to ferrihydrite as an inner-sphere complex and phosphate and amine groups are involved in this interaction. Second, an increase of sodium chloride salt concentration increased the adsorption of glyphosate onto ferrihydrite. The non-linear Langmuir model and pseudo second order model showed a good agreement of theoretical limit of glyphosate adsorbed onto ferrihydrite, 54.88?μg?mg?1 and 48.8?μg?mg?1, respectively. The adsorption of glyphosate onto ferrihydrite decreased when the pH increased. Under the conditions used in this work, EPR spectra did not show dissolution of ferrihydrite. Surface area, pore volume and pHpzc of ferrihydrite decreased after adsorption of glyphosate.
{"title":"The effect of pH and ionic strength on the adsorption of glyphosate onto ferrihydrite","authors":"Rodrigo C. Pereira, Pedro R. Anizelli, Eduardo Di Mauro, Daniel F. Valezi, Antonio Carlos S. da Costa, Cássia Thaïs B. V. Zaia, Dimas A. M. Zaia","doi":"10.1186/s12932-019-0063-1","DOIUrl":"https://doi.org/10.1186/s12932-019-0063-1","url":null,"abstract":"<p>Although, glyphosate (<i>N</i>-(phosphonomethyl) glycine) is one of the most widely used herbicides in the world, its interaction with poorly crystalline iron oxides, such as ferrihydrite, is not well studied. In this research, we examined the adsorption of glyphosate onto ferrihydrite using infrared spectroscopy (FT-IR), electron paramagnetic resonance spectroscopy (EPR), adsorption kinetic models and adsorption isotherm models. The effect of pH and sodium chloride concentration on the adsorption of glyphosate onto ferrihydrite as well as the effect of extractors (CaCl<sub>2</sub> 0.010?mol?L<sup>?1</sup> and Mehlich) on the desorption of glyphosate were also evaluated. There are two important findings described in this work. First, 84% of adsorbed glyphosate strongly interacted to ferrihydrite as an inner-sphere complex and phosphate and amine groups are involved in this interaction. Second, an increase of sodium chloride salt concentration increased the adsorption of glyphosate onto ferrihydrite. The non-linear Langmuir model and pseudo second order model showed a good agreement of theoretical limit of glyphosate adsorbed onto ferrihydrite, 54.88?μg?mg<sup>?1</sup> and 48.8?μg?mg<sup>?1</sup>, respectively. The adsorption of glyphosate onto ferrihydrite decreased when the pH increased. Under the conditions used in this work, EPR spectra did not show dissolution of ferrihydrite. Surface area, pore volume and pH<sub>pzc</sub> of ferrihydrite decreased after adsorption of glyphosate.</p>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2019-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/s12932-019-0063-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4948912","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}