Geochemical Transactions最新文献

{"title":"Stable isotope evidence for the Bottom Convective Layer homogeneity in the Black Sea","authors":"Alexander V Dubinin,&nbsp;Elena O Dubinina,&nbsp;Tatyana P Demidova,&nbsp;Nataliya M Kokryatskaya,&nbsp;Maria N Rimskaya-Korsakova,&nbsp;Sofia A Kosova,&nbsp;Evgeniy V Yakushev","doi":"10.1186/1467-4866-15-3","DOIUrl":"https://doi.org/10.1186/1467-4866-15-3","url":null,"abstract":"<p>The Black Sea is the largest euxinic basin on the Earth. The anoxic zone consists of the upper part water mass stratified by density, and the lower water mass homogenized relative to density (depth &gt;1750 m), named the Bottom Convective Layer. To assess homogeneity and possible exchange of matter across the upper and lower boundaries of the Bottom Convective Layer, new data on stable isotope composition of S, O and H were obtained. Samples were collected in August 2008 and March 2009 from two stations located in the eastern central part of the Black Sea.</p><p>Distribution of δ¹⁸O and δD values of water for the entire water column did not vary seasonally. Appreciable differences were marked for δD value variation in the picnocline area (water depth 200-400 m) and in the BCL 5 m above the bottom that might be caused by penetration of intrusions with elevated portion of shelf modified Mediterranean Water. Observed linear relationship between δ¹⁸O (or δD) and salinity indicates that mixing water and salt occurs at the same time, and the deep water of the Black Sea has two end members: the high-salinity Mediterranean seawater and freshwater input.</p><p>In the Bottom Convective Layer, the average δ³⁴S (H₂S) was -40.6 ± 0.5‰ and did not vary seasonally. At the bottom (depth &gt; 2000 m), ³⁴S depletion down to –41.0‰ was observed. Our δ³⁴S (SO₄) data are by 2-3‰ higher than those measured previously for the Bottom Convective Layer. Sulfate from the aerobic zone with δ³⁴S (SO₄) = +21‰ corresponds to ocean water sulfate and that has not been subjected to sulfate reduction. Average δ³⁴S (SO₄) values for depths &gt; 1250 m were found to be +23.0 ± 0.2‰ (1σ). Sulfur isotope composition of sulfate does not change in the Bottom Convective Layer and on its upper and lower boundaries, and does not depend on the season of observation.</p>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":"15 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2014-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/1467-4866-15-3","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4666436","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":"Concentrations and sources of polycyclic aromatic hydrocarbons in surface coastal sediments of the northern Gulf of Mexico","authors":"Zucheng Wang,&nbsp;Zhanfei Liu,&nbsp;Kehui Xu,&nbsp;Lawrence M Mayer,&nbsp;Zulin Zhang,&nbsp;Alexander S Kolker,&nbsp;Wei Wu","doi":"10.1186/1467-4866-15-2","DOIUrl":"https://doi.org/10.1186/1467-4866-15-2","url":null,"abstract":"<p>Coastal sediments in the northern Gulf of Mexico have a high potential of being contaminated by petroleum hydrocarbons, such as polycyclic aromatic hydrocarbons (PAHs), due to extensive petroleum exploration and transportation activities. In this study we evaluated the spatial distribution and contamination sources of PAHs, as well as the bioavailable fraction in the bulk PAH pool, in surface marsh and shelf sediments (top 5?cm) of the northern Gulf of Mexico.</p><p>PAH concentrations in this region ranged from 100 to 856?ng?g^?1, with the highest concentrations in Mississippi River mouth sediments followed by marsh sediments and then the lowest concentrations in shelf sediments. The PAH concentrations correlated positively with atomic C/N ratios of sedimentary organic matter (OM), suggesting that terrestrial OM preferentially sorbs PAHs relative to marine OM. PAHs with 2 rings were more abundant than those with 5–6 rings in continental shelf sediments, while the opposite was found in marsh sediments. This distribution pattern suggests different contamination sources between shelf and marsh sediments. Based on diagnostic ratios of PAH isomers and principal component analysis, shelf sediment PAHs were petrogenic and those from marsh sediments were pyrogenic. The proportions of bioavailable PAHs in total PAHs were low, ranging from 0.02% to 0.06%, with higher fractions found in marsh than shelf sediments.</p><p>PAH distribution and composition differences between marsh and shelf sediments were influenced by grain size, contamination sources, and the types of organic matter associated with PAHs. Concentrations of PAHs in the study area were below effects low-range, suggesting a low risk to organisms and limited transfer of PAHs into food web. From the source analysis, PAHs in shelf sediments mainly originated from direct petroleum contamination, while those in marsh sediments were from combustion of fossil fuels.</p>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":"15 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2014-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/1467-4866-15-2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4756554","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 organic matter on estuarine flocculation: a laboratory study using montmorillonite, humic acid, xanthan gum, guar gum and natural estuarine flocs","authors":"Yoko Furukawa,&nbsp;Allen H Reed,&nbsp;Guoping Zhang","doi":"10.1186/1467-4866-15-1","DOIUrl":"https://doi.org/10.1186/1467-4866-15-1","url":null,"abstract":"<p>Riverine particles undergo a rapid transformation when they reach estuaries. The rapid succession of hydrodynamic and biogeochemical regimes forces the particles to flocculate, settle and enter the sediment pool. The rates and magnitudes of flocculation depend on the nature of the particles which are primarily affected by the types and quantities of organic matter (OM). Meanwhile, the OM characteristics vary widely between environments, as well as within a single environment due to seasonal climate and land use variability. We investigated the effect of the OM types and quantities through laboratory experiments using natural estuarine particles from the Mississippi Sound and Atchafalaya Bay as well as model mixtures of montmorillonite and organic molecules (i.e., biopolymers (guar/xanthan gums) and humic acid).</p><p>Biopolymers promote flocculation but the magnitude depends on the types and quantities. Nonionic guar gum yields much larger flocs than anionic xanthan gum, while both of them exhibit a nonlinear behavior in which the flocculation is the most pronounced at the intermediate OM loading. Moreover, the effect of guar gum is independent of salinity whereas the effect of xanthan gum is pronounced at higher salinity. Meanwhile, humic acid does not affect flocculation at all salinity values tested in this study. These results are echoed in the laboratory manipulation of the natural estuarine particles. Flocculation of the humic acid-rich Mississippi Sound particles is unaffected by the OM, whereas that of biopolymer-rich Atchafalaya Bay particles is enhanced by the OM.</p><p>Flocculation is positively influenced by the presence of biopolymers that are produced as the result of marine primary production. Meanwhile, humic acid, which is abundant in the rivers that drain the agricultural soils of Southeastern United States, has little influence on flocculation. Thus, it is expected that humic acid-poor riverine particles (e.g., Mississippi River, and Atchafalaya River, to a lesser degree) may be prone to rapid flocculation and settling in the immediate vicinity of the river mouths when mixed with biopolymer-rich coastal waters. It is also expected that humic acid-rich riverine particles (e.g., Pearl River) may resist immediate flocculation and be transported further away from the river mouth.</p>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":"15 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2014-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/1467-4866-15-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4119552","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":"Methane and carbon at equilibrium in source rocks","authors":"Frank D Mango","doi":"10.1186/1467-4866-14-5","DOIUrl":"https://doi.org/10.1186/1467-4866-14-5","url":null,"abstract":"<p>Methane in source rocks may not exist exclusively as free gas. It could exist in equilibrium with carbon and higher hydrocarbons: CH₄?+?C?&lt;?=?&gt;?Hydrocarbon. Three lines of evidence support this possibility. 1) Shales ingest gas in amounts and selectivities consistent with gas-carbon equilibrium. There is a 50% increase in solid hydrocarbon mass when Fayetteville Shale is exposed to methane (450?psi) under moderate conditions (100°C): Rock-Eval S2 (mg?g^-1) 8.5 =?&gt;?12.5. All light hydrocarbons are ingested, but with high selectivity, consistent with competitive addition to receptor sites in a growing polymer. Mowry Shale ingests butane vigorously from argon, for example, but not from methane under the same conditions. 2) Production data for a well producing from Fayetteville Shale declines along the theoretical curve for withdrawing gas from higher hydrocarbons in equilibrium with carbon. 3) A new general gas-solid equilibrium model accounts for natural gas at thermodynamic equilibrium, and C₆-C₇ hydrocarbons constrained to invariant compositions. The results make a strong case for methane in equilibrium with carbon and higher hydrocarbons. If correct, the higher hydrocarbons in source rocks are gas reservoirs, raising the possibility of substantially more gas in shales than analytically apparent, and far more gas in shale deposits than currently recognized.</p>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":"14 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2013-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/1467-4866-14-5","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4489001","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 new model for the biodegradation kinetics of oil droplets: application to the Deepwater Horizon oil spill in the Gulf of Mexico","authors":"Javier Vilcáez,&nbsp;Li Li,&nbsp;Susan S Hubbard","doi":"10.1186/1467-4866-14-4","DOIUrl":"https://doi.org/10.1186/1467-4866-14-4","url":null,"abstract":"<p>Oil biodegradation by native bacteria is one of the most important natural processes that can attenuate the environmental impacts of marine oil spills. Existing models for oil biodegradation kinetics are mostly for dissolved oil. This work developed a new mathematical model for the biodegradation of oil droplets and applied the model to estimate the time scale for oil biodegradation under conditions relevant to the Deepwater Horizon oil spill in the Gulf of Mexico. In the model, oil is composed of droplets of various sizes following the gamma function distribution. Each oil droplet shrinks during the microbe-mediated degradation at the oil-water interface. Using our developed model, we find that the degradation of oil droplets typically goes through two stages. The first stage is characterized by microbial activity unlimited by oil-water interface with higher biodegradation rates than that of the dissolved oil. The second stage is governed by the availability of the oil-water interface, which results in much slower rates than that of soluble oil. As a result, compared to that of the dissolved oil, the degradation of oil droplets typically starts faster and then quickly slows down, ultimately reaching a smaller percentage of degraded oil in longer time. The availability of the water-oil interface plays a key role in determining the rates and extent of degradation. We find that several parameters control biodegradation rates, including size distribution of oil droplets, initial microbial concentrations, initial oil concentration and composition. Under conditions relevant to the Deepwater Horizon spill, we find that the size distribution of oil droplets (mean and coefficient of variance) is the most important parameter because it determines the availability of the oil-water interface. Smaller oil droplets with larger variance leads to faster and larger extent of degradation. The developed model will be useful for evaluating transport and fate of spilled oil, different remediation strategies, and risk assessment.</p>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":"14 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2013-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/1467-4866-14-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4807516","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":"The surface properties of Shewanella putrefaciens 200 and S. oneidensis MR-1: the effect of pH and terminal electron acceptors","authors":"Yoko Furukawa,&nbsp;Jason R Dale","doi":"10.1186/1467-4866-14-3","DOIUrl":"https://doi.org/10.1186/1467-4866-14-3","url":null,"abstract":"<p>We investigated the surface characteristics of two strains of <i>Shewanella sp</i>., <i>S</i>. <i>oneidensis</i> MR-1 and <i>S</i>. <i>putrefaciens</i> 200, that were grown under aerobic conditions as well as under anaerobic conditions with trimethylamine oxide (TMAO) as the electron acceptor. The investigation focused on the experimental determination of electrophoretic mobility (EPM) under a range of pH and ionic strength, as well as by subsequent modeling in which <i>Shewanella</i> cells were considered to be soft particles with water- and ion-permeable outermost layers.</p><p>The soft layer of <i>p</i>200 is significantly more highly charged (i.e., more negative) than that of MR-1. The effect of electron acceptor on the soft particle characteristics of <i>Shewanella sp</i>. is complex. The fixed charge density, which is a measure of the deionized and deprotonated functional groups in the soft layer polymers, is slightly greater (i.e., more negative) for aerobically grown <i>p</i>200 than for <i>p</i>200 grown with TMAO. On the other hand, the fixed charge density of aerobically grown MR1 is slightly less than that of <i>p</i>200 grown with TMAO. The effect of pH on the soft particle characteristics is also complex, and does not exhibit a clear pH-dependent trend.</p><p>The <i>Shewanella</i> surface characteristics were attributed to the nature of the outermost soft layer, the extracellular polymeric substances (EPS) in case of <i>p</i>200 and lypopolysaccharides (LPS) in case of MR1 which generally lacks EPS. The growth conditions (i.e., aerobic vs. anaerobic TMAO) have an influence on the soft layer characteristics of <i>Shewanella sp</i>. cells. Meanwhile, the clear pH dependency of the mechanical and morphological characteristics of EPS and LPS layers, observed in previous studies through atomic force microscopy, adhesion tests and spectroscopies, cannot be corroborated by the electrohydrodynamics-based soft particle characteristics which does not exhibited a clear pH dependency in this study. While the electrohydrodynamics-based soft-particle model is a useful tool in understanding bacteria’s surface properties, it needs to be supplemented with other characterization methods and models (e.g., chemical and micromechanical) in order to comprehensively address all of the surface-related characteristics important in environmental and other aqueous processes.</p>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":"14 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2013-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/1467-4866-14-3","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4326438","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":"Alkaline decomposition of synthetic jarosite with arsenic","authors":"Francisco Patiño,&nbsp;Mizraim U Flores,&nbsp;Iván A Reyes,&nbsp;Martín Reyes,&nbsp;Juan Hernández,&nbsp;Isauro Rivera,&nbsp;Julio C Juárez","doi":"10.1186/1467-4866-14-2","DOIUrl":"https://doi.org/10.1186/1467-4866-14-2","url":null,"abstract":"<p>The widespread use of jarosite-type compounds to eliminate impurities in the hydrometallurgical industry is due to their capability to incorporate several elements into their structures. Some of these elements are of environmental importance (Pb²⁺, Cr⁶⁺, As⁵⁺, Cd²⁺, Hg²⁺). For the present paper, AsO₄^3- was incorporated into the lattice of synthetic jarosite in order to carry out a reactivity study. Alkaline decomposition is characterized by removal of sulfate and potassium ions from the lattice and formation of a gel consisting of iron hydroxides with absorbed arsenate. Decomposition curves show an induction period followed by a conversion period. The induction period is independent of particle size and exponentially decreases with temperature. The conversion period is characterized by formation of a hydroxide halo that surrounds an unreacted jarosite core. During the conversion period in NaOH media for [OH^-]?&gt;?8?×?10^-3?mol?L^-1, the process showed a reaction order of 1.86, and an apparent activation energy of 60.3?kJ?mol^-1 was obtained. On the other hand, during the conversion period in Ca(OH)₂ media for [OH^-]?&gt;?1.90?×?10^-2?mol?L^-1, the reaction order was 1.15, and an apparent activation energy of 74.4?kJ?mol^-1 was obtained. The results are consistent with the spherical particle model with decreasing core and chemical control.</p>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":"14 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2013-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/1467-4866-14-2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4321980","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":"Evaluating ion exchange resin efficiency and oxidative capacity for the separation of uranium(IV) and uranium(VI)","authors":"Deborah L Stoliker,&nbsp;Nazila Kaviani,&nbsp;Douglas B Kent,&nbsp;James A Davis","doi":"10.1186/1467-4866-14-1","DOIUrl":"https://doi.org/10.1186/1467-4866-14-1","url":null,"abstract":"<p>Previously described methods to separate dissolved U(IV) from dissolved U(VI) under acidic anoxic conditions prior to laboratory analysis were ineffective with materials currently available commercially. Three strong anion exchange resins were examined for their efficiency in separating, recovering, and preserving both redox states during separation.</p><p>Under oxic conditions, recovery of U(VI) from three exchange resins (Bio-Rad AG? 1x8 Poly-Prep? prefilled columns, Bio-Rad AG? 1x8 powder, and Dowex? 1x8 powder) ranged from 72% to 100% depending on the dosed mass, eluent volume, and resin selected. Dowex? 1x8 resin was the only resin found to provide 100% recovery of U(VI) with fewer than 5 bed volumes of eluent. Under anoxic conditions, all three resins oxidized U(IV) in aqueous solutions with relatively low U(IV) concentrations (&lt;3x10^-6 M). Resin-induced oxidation was observed visually using a leuco dye, safranin-o. Oxidants associated with the resin were irreversibly reduced by the addition of Ti(III). After anoxic resin pre-treatment, a series of U(IV)/U(VI) mixtures at micro-molar levels were prepared and separated using the Dowex? 1x8 resin with 100% recovery of both U(IV) and U(VI) with no resin-induced changes in oxidation state.</p><p>Currently available anion exchange resins with apparently identical physical properties were found to have significantly different recoveries for hexavalent uranium at micro-molar concentrations. A novel qualitative technique was developed to visually assess oxidative capacities of anion exchange resins under acidic anoxic conditions. A protocol was developed for pre-treatment and use of currently available anion exchange resins to achieve quantitative separation of U(IV) and U(VI) in aqueous solutions with low U(IV) concentrations. This method can be applied to future work to quantitatively assess dissolved U(IV) and U(VI) concentrations in both laboratory and field samples.</p>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":"14 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2013-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/1467-4866-14-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5174628","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":"Characterisation of dissolved organic compounds in hydrothermal fluids by stir bar sorptive extraction - gas chomatography - mass spectrometry. Case study: the Rainbow field (36°N, Mid-Atlantic Ridge)","authors":"Cecile Konn,&nbsp;Jean-Luc Charlou,&nbsp;Jean-Pierre Donval,&nbsp;Nils G Holm","doi":"10.1186/1467-4866-13-8","DOIUrl":"https://doi.org/10.1186/1467-4866-13-8","url":null,"abstract":"<p>The analysis of the dissolved organic fraction of hydrothermal fluids has been considered a real challenge due to sampling difficulties, complexity of the matrix, numerous interferences and the assumed ppb concentration levels. The present study shows, in a qualitative approach, that Stir Bar Sorptive Extraction (SBSE) followed by Thermal Desorption – Gas Chromatography – Mass Spectrometry (TD-GC-MS) is suitable for extraction of small sample volumes and detection of a wide range of volatile and semivolatile organic compounds dissolved in hydrothermal fluids. In a case study, the technique was successfully applied to fluids from the Rainbow ultramafic-hosted hydrothermal field located at 36°14’N on the Mid-Atlantic Ridge (MAR). We show that n-alkanes, mono- and poly- aromatic hydrocarbons as well as fatty acids can be easily identified and their retention times determined. Our results demonstrate the excellent repeatability of the method as well as the possibility of storing stir bars for at least three years without significant changes in the composition of the recovered organic matter. A preliminary comparative investigation of the organic composition of the Rainbow fluids showed the great potential of the method to be used for assessing intrafield variations and carrying out time series studies. All together our results demonstrate that SBSE-TD-GC-MS analyses of hydrothermal fluids will make important contributions to the understanding of geochemical processes, geomicrobiological interactions and formation of mineral deposits.</p>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":"13 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2012-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/1467-4866-13-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4314194","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":"Ordovician ash geochemistry and the establishment of land plants","authors":"John Parnell,&nbsp;Sorcha Foster","doi":"10.1186/1467-4866-13-7","DOIUrl":"https://doi.org/10.1186/1467-4866-13-7","url":null,"abstract":"<p>The colonization of the terrestrial environment by land plants transformed the planetary surface and its biota, and shifted the balance of Earth’s biomass from the subsurface towards the surface. However there was a long delay between the formation of palaeosols (soils) on the land surface and the key stage of plant colonization. The record of palaeosols, and their colonization by fungi and lichens extends well back into the Precambrian. While these early soils provided a potential substrate, they were generally leached of nutrients as part of the weathering process. In contrast, volcanic ash falls provide a geochemically favourable substrate that is both nutrient-rich and has high water retention, making them good hosts to land plants. An anomalously extensive system of volcanic arcs generated unprecedented volumes of lava and volcanic ash (tuff) during the Ordovician. The earliest, mid-Ordovician, records of plant spores coincide with these widespread volcanic deposits, suggesting the possibility of a genetic relationship. The ash constituted a global environment of nutrient-laden, water-saturated soil that could be exploited to maximum advantage by the evolving anchoring systems of land plants. The rapid and pervasive inoculation of modern volcanic ash by plant spores, and symbiotic nitrogen-fixing fungi, suggests that the Ordovician ash must have received a substantial load of the earliest spores and their chemistry favoured plant development. In particular, high phosphorus levels in ash were favourable to plant growth. This may have allowed photosynthesizers to diversify and enlarge, and transform the surface of the planet.</p>","PeriodicalId":12694,"journal":{"name":"Geochemical Transactions","volume":"13 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2012-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1186/1467-4866-13-7","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5065093","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}