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Geochemistry

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https://www.readbyqxmd.com/read/28096405/selenium-isotopes-record-extensive-marine-suboxia-during-the-great-oxidation-event
#1
Michael A Kipp, Eva E Stüeken, Andrey Bekker, Roger Buick
It has been proposed that an "oxygen overshoot" occurred during the early Paleoproterozoic Great Oxidation Event (GOE) in association with the extreme positive carbon isotopic excursion known as the Lomagundi Event. Moreover, it has also been suggested that environmental oxygen levels then crashed to very low levels during the subsequent extremely negative Shunga-Francevillian carbon isotopic anomaly. These redox fluctuations could have profoundly influenced the course of eukaryotic evolution, as eukaryotes have several metabolic processes that are obligately aerobic...
January 17, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28088549/redistribution-of-elements-between-wastes-and-organic-bearing-material-in-the-dispersion-train-of-gold-bearing-sulfide-tailings-part-i-geochemistry-and-mineralogy
#2
B Yu Saryg-Ool, I N Myagkaya, I S Kirichenko, M A Gustaytis, O V Shuvaeva, S M Zhmodik, E V Lazareva
Migration and redistribution of elements during prolonged interaction of cyanide wastes with the underlying natural organic-bearing material have been studied in two ~40cm deep cores that sample primary ores and their weathering profile (wastes I and II, respectively) in the dispersion train of gold-bearing sulfide tailings in Siberia. Analytical results of SR-XRF, whole-rock XRF, AAS, CHNS, and SEM measurements of core samples show high K, Sr, Ti, and Fe enrichments and correlation of P2O5 and Mn with LOI and Corg...
January 11, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/28076393/alder-nitrogen-and-lake-ecology-terrestrial-aquatic-linkages-in-the-postglacial-history-of-lone-spruce-pond-southwestern-alaska
#3
Bianca B Perren, Yarrow Axford, Darrell S Kaufman
Diatoms, combined with a multiproxy study of lake sediments (organic matter, N, δ15N, δ13C, biogenic silica, grain size, Cladocera and chironomids, Alnus pollen) from Lone Spruce Pond, Alaska detail the late-glacial to Holocene history of the lake and its response to regional climate and landscape change over the last 14.5 cal ka BP. We show that the immigration of alder (Alnus viridis) in the early Holocene marks the rise of available reactive nitrogen (Nr) in the lake as well as the establishment of a primarily planktonic diatom community...
2017: PloS One
https://www.readbyqxmd.com/read/28063656/effect-of-cyclic-redox-oscillations-on-water-quality-in-freshwater-acid-sulfate-soil-wetlands
#4
Niloofar Karimian, Scott G Johnston, Edward D Burton
Restoration of acid sulfate soil (ASS) wetlands by freshwater re-flooding can lead to the reformation of various Fe(II) and reduced inorganic sulfur (RIS) species in surface soil layers. However, in many locations, wetland water levels undergo large seasonal fluctuations that drive extreme redox oscillations. Newly formed RIS species [e.g. greigite, mackinawite, nano-pyrite and S(0)] and Fe(II) are vulnerable to rapid oxidation during dry periods and may generate substantial acidity. Rainfall following a dry period may then mobilise acidity and metal cations in surface waters prior to eventual recovery in pH by re-establishment of reducing conditions...
January 4, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/28045509/metal-ion-modeling-using-classical-mechanics
#5
Pengfei Li, Kenneth M Merz
Metal ions play significant roles in numerous fields including chemistry, geochemistry, biochemistry, and materials science. With computational tools increasingly becoming important in chemical research, methods have emerged to effectively face the challenge of modeling metal ions in the gas, aqueous, and solid phases. Herein, we review both quantum and classical modeling strategies for metal ion-containing systems that have been developed over the past few decades. This Review focuses on classical metal ion modeling based on unpolarized models (including the nonbonded, bonded, cationic dummy atom, and combined models), polarizable models (e...
January 3, 2017: Chemical Reviews
https://www.readbyqxmd.com/read/28040254/source-distribution-and-ecotoxicological-assessment-of-multielements-in-superficial-sediments-of-a-tropical-turbid-estuarine-environment-a-multivariate-approach
#6
M J Watts, S Mitra, A L Marriott, S K Sarkar
The work examined the distribution, possible sources and ecotoxicological assessment of 51 trace elements covering 13 sampling stations in surface sediments of coastal regions of Sundarban mangrove wetland and adjacent Hugli river estuary. The element concentrations exhibited an increasing trend towards downstream of the estuary (except lanthanides) with maximum enrichment for 22 elements at Gangadharpur (Sundarban region). According to Sediment Quality Guidelines (SQGs), the concentrations of Cu, As, Cr and Cd exceeded the Effects-Range-Low values, while Ni at certain stations exceeded the Effects-Range-Medium suggesting adverse effects on the sediment-dwelling organisms...
December 28, 2016: Marine Pollution Bulletin
https://www.readbyqxmd.com/read/28034542/shifts-in-microbial-community-structure-and-function-in-surface-waters-impacted-by-unconventional-oil-and-gas-wastewater-revealed-by-metagenomics
#7
N L Fahrenfeld, Hannah Delos Reyes, Alessia Eramo, Denise M Akob, Adam C Mumford, Isabelle M Cozzarelli
Unconventional oil and gas (UOG) production produces large quantities of wastewater with complex geochemistry and largely uncharacterized impacts on surface waters. In this study, we assessed shifts in microbial community structure and function in sediments and waters upstream and downstream from a UOG wastewater disposal facility. To do this, quantitative PCR for 16S rRNA and antibiotic resistance genes along with metagenomic sequencing were performed. Elevated conductivity and markers of UOG wastewater characterized sites sampled downstream from the disposal facility compared to background sites...
December 26, 2016: Science of the Total Environment
https://www.readbyqxmd.com/read/28004913/geochemical-parameters-and-reductive-dechlorination-determine-aerobic-cometabolic-vs-aerobic-metabolic-vinyl-chloride-biodegradation-at-oxic-anoxic-interface-of-hyporheic-zones
#8
Siavash Atashgahi, Yue Lu, Javier Ramiro-Garcia, Peng Peng, Farai Maphosa, Detmer Sipkema, Winnie Dejonghe, Hauke Smidt, Dirk Springael
Hyporheic zones mediate vinyl chloride (VC) biodegradation in groundwater discharging into surface waters. At the oxic/anoxic interface (OAI) of hyporheic zones subjected to redox oscillations, VC is degraded via co-existing aerobic ethenotrophic and anaerobic reductive dechlorination pathways. However, the identity of aerobic VC degradation pathways (cometabolic vs metabolic) and their interactions with reductive dechlorination in relation to riverbed sediment geochemistry remain ill-defined. We addressed this using microcosms containing OAI sediments incubated under fluctuating oxic/anoxic atmosphere...
December 22, 2016: Environmental Science & Technology
https://www.readbyqxmd.com/read/27995953/anthropogenic-and-natural-sources-of-dust-in-peatland-during-the-anthropocene
#9
B Fiałkiewicz-Kozieł, B Smieja-Król, M Frontasyeva, M Słowiński, K Marcisz, E Lapshina, D Gilbert, A Buttler, V E J Jassey, K Kaliszan, F Laggoun-Défarge, P Kołaczek, M Lamentowicz
As human impact have been increasing strongly over the last decades, it is crucial to distinguish human-induced dust sources from natural ones in order to define the boundary of a newly proposed epoch - the Anthropocene. Here, we track anthropogenic signatures and natural geochemical anomalies in the Mukhrino peatland, Western Siberia. Human activity was recorded there from cal AD 1958 (±6). Anthropogenic spheroidal aluminosilicates clearly identify the beginning of industrial development and are proposed as a new indicator of the Anthropocene...
December 20, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27960117/factors-controlling-groundwater-salinization-and-hydrogeochemical-processes-in-coastal-aquifers-from-southern-spain
#10
M Argamasilla, J A Barberá, B Andreo
In detrital coastal aquifers, seawater and surface water may interact with groundwater in multiple ways. Understanding the interference of water fluxes in this type of environment is essential to effectively manage the groundwater resources in water-stressed regions, such as the Mediterranean coastal fringe. In this research, the characterization of the main hydrogeochemical processes and the interaction between surface water and groundwater in the Marbella-Estepona coastal aquifers (southern Spain) have been carried out by means of the combined use of different hydrogeochemical indicators along with isotope data...
December 9, 2016: Science of the Total Environment
https://www.readbyqxmd.com/read/27960056/chemical-identification-at-the-solid-liquid-interface
#11
Hagen Söngen, Christoph Marutschke, Peter Spijker, Eric Holmgren, Ilka Hermes, Ralf Bechstein, Stefanie Klassen, John Tracey, Adam S Foster, Angelika Kühnle
Solid-liquid interfaces are decisive for a wide range of natural and technological processes, including fields as diverse as geochemistry and environmental science as well as catalysis and corrosion protection. Dynamic atomic force microscopy nowadays provides unparalleled structural insights into solid-liquid interfaces, including the solvation structure above the surface. In contrast, chemical identification of individual interfacial atoms still remains a considerable challenge. So far, an identification of chemically alike atoms in a surface alloy has only been demonstrated under well-controlled ultrahigh vacuum conditions...
December 22, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/27941864/sulfur-geochemistry-of-a-lacustrine-record-from-taiwan-reveals-enhanced-marine-aerosol-input-during-the-early-holocene
#12
Xiaodong Ding, Dawei Li, Liwei Zheng, Hongyan Bao, Huei-Fen Chen, Shuh-Ji Kao
Lacustrine record of marine aerosol input has rarely been documented. Here, we present the sulfur geochemistry during the last deglaciation and early Holocene of a sediment core retrieved from the Dongyuan Lake in southern Taiwan. An unusually high sulfur peak accompanying pyrite presence is observed at 10.5 ka BP. Such high sulfur content in lacustrine record is unusual. The δ(34)S of sulfur varied from +9.5 to + 17.1‰ with two significant positive shifts at 10.5 and 9.4 ka BP. The sources of sulfur and potential processes involving the sulfur isotope variation including bacterial sulfate reduction, volcanic emissions, in-catchment sulfide oxidation and marine aerosol input are discussed...
December 12, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27934262/long-term-trends-in-acid-neutralizing-capacity-under-increasing-acidic-deposition-a-special-example-of-eutrophic-taihu-lake-china
#13
Tao Yu, Qiujin Xu, Chengda He, Haibing Cong, Dan Dai, Fengchang Wu, Wei Meng
While North America and Europe have been recovering from acidification, China is experiencing impacts of acid deposition. The Taihu region is a seriously impacted area by acid rain in China, with the average rainfall pH < 5. However, the acid neutralizing capacity (ANC) and pH of Taihu Lake have significantly increased over the past 60 years (p < 0.05). Analyses showed that watershed neutralization by carbonates and in-lake alkalinization by algae activities were the two major reactions responsible for the increase...
December 6, 2016: Environmental Science & Technology
https://www.readbyqxmd.com/read/27890409/geochemistry-of-arsenic-in-low-sulfide-high-carbonate-coal-waste-rock-elk-valley-british-columbia-canada
#14
Ashis Biswas, M Jim Hendry, Joseph Essilfie-Dughan
This study investigated the geochemistry of arsenic (As) in low sulfide-high carbonate coal waste rock of the Elk Valley, British Columbia, Canada. Its abundance and mineralogical associations in waste rock of different placement periods were determined in addition to its mobilization into porewater and rock-drain effluent. The mean (5.34mg/kg; 95% confidence interval: 4.95-5.73mg/kg) As concentration in the waste rock was typical of sedimentary rock. Electron microprobe and As K-edge X-ray absorption near-edge spectroscopic analyses showed the As is predominantly associated with primary pyrites in both source and freshly blasted waste rock...
February 1, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/27890403/isoelectric-points-and-points-of-zero-charge-of-metal-hydr-oxides-50years-after-parks-review
#15
REVIEW
Marek Kosmulski
The pH-dependent surface charging of metal (hydr)oxides is reviewed on the occasion of the 50th anniversary of the publication by G.A. Parks: "Isoelectric points of solid oxides, solid hydroxides, and aqueous hydroxo complex systems" in Chemical Reviews. The point of zero charge (PZC) and isoelectric point (IEP) became standard parameters to characterize metal oxides in aqueous dispersions, and they define adsorption (surface excess) of ions, stability against coagulation, rheological properties of dispersions, etc...
December 2016: Advances in Colloid and Interface Science
https://www.readbyqxmd.com/read/27888479/use-of-major-ions-to-evaluate-the-hydrogeochemistry-of-groundwater-influenced-by-reclamation-and-seawater-intrusion-west-nile-delta-egypt
#16
Zenhom El-Said Salem, Osman M Osman
The aim of this research is to evaluate the groundwater geochemistry in western Nile Delta area as an example of an aquifer influenced by reclamation and seawater intrusion. To conduct this study, 63 groundwater samples and one surface water sample from El Nubaria Canal were collected. To estimate the origin of dissolved ions and the geochemical processes influencing this groundwater, integration between land use change, pedological, hydrogeological, hydrogeochemical, and statistical approaches was considered...
November 25, 2016: Environmental Science and Pollution Research International
https://www.readbyqxmd.com/read/27885397/assessment-of-indexes-for-heavy-metal-contamination-in-remote-areas-a-case-study-in-a-pyrenean-forest-navarra-spain
#17
Delia Rodríguez-Oroz, Esther Lasheras, David Elustondo, Jordi Garrigó
The objective of the present work was to verify and compare the performance of different geochemical indices employed to identify the anthropogenic origin of selected heavy metals and other trace elements in soils. To that end, two background values, the upper continental crust and the metal content in the bed rock, were used and obtained from a forested basin of the western Pyrenees. The enrichment factor (EF), geo-accumulation index (Igeo), and contamination factor (C(i)f) were finally evaluated for their ability to determine anthropogenic contamination: Results indicate that an in-depth knowledge of the bed rock geochemistry and the geological background content is essential to distinguish between the natural variability of soils and any anthropogenic contribution of heavy metals...
November 24, 2016: Bulletin of Environmental Contamination and Toxicology
https://www.readbyqxmd.com/read/27867799/the-puck-energetic-charged-particle-detector-design-heritage-and-advancements
#18
G Clark, I Cohen, J H Westlake, G B Andrews, P Brandt, R E Gold, M A Gkioulidou, R Hacala, D Haggerty, M E Hill, G C Ho, S E Jaskulek, P Kollmann, B H Mauk, R L McNutt, D G Mitchell, K S Nelson, C Paranicas, N Paschalidis, C E Schlemm
Energetic charged particle detectors characterize a portion of the plasma distribution function that plays critical roles in some physical processes, from carrying the currents in planetary ring currents to weathering the surfaces of planetary objects. For several low-resource missions in the past, the need was recognized for a low-resource but highly capable, mass-species-discriminating energetic particle sensor that could also obtain angular distributions without motors or mechanical articulation. This need led to the development of a compact Energetic Particle Detector (EPD), known as the "Puck" EPD (short for hockey puck), that is capable of determining the flux, angular distribution, and composition of incident ions between an energy range of ~10 keV to several MeV...
August 2016: Journal of Geophysical Research. Space Physics
https://www.readbyqxmd.com/read/27866372/input-behaviour-and-distribution-of-multiple-elements-in-abiotic-matrices-along-a-transect-within-the-okavango-delta-northern-botswana
#19
Jörg Schaller, Jonas Schoelynck, Mike Murray-Hudson, Patrick J Frings, Dimitri van Pelt, Tilo Hegewald, Keotshephile Mosimane, Mangaliso Gondwe, Piotr Wolski, Patrick Meire, Eric Struyf
Wetlands fed by rivers can be a sink for elements depending on elemental concentrations, wetland hydrology, geochemistry, vegetation and climate. In the case of the Okavango Delta, northern Botswana, the outflow discharge is a small fraction (2-5%) of the inflow. This has strong potential consequences for the Delta, as it strongly affects element cycling and storage within the Delta. We estimated the inputs, behaviour and distribution of multiple elements along a longitudinal transect within the Okavango Delta, to show potential effects of retention mechanisms of different elements...
December 2016: Environmental Monitoring and Assessment
https://www.readbyqxmd.com/read/27866361/hydrogeochemical-characterization-of-the-thermal-springs-in-northeastern-of-los-cabos-block-baja-california-sur-m%C3%A3-xico
#20
Pablo Hernández-Morales, Jobst Wurl
The existence of hot springs in the northeastern part of Los Cabos Baja California Sur (BCS), is known from pre-Hispanic times, but their hydrochemical composition had not been previously described. Several springs are located within the watershed of Santiago, and the objective of this study was to define the hydrogeochemical composition of the thermal springs and to characterize the geothermal reservoir. A total of 16 water samples were taken in 11 geothermal manifestations under dry (June 2014) and humid (March 2015) conditions...
November 19, 2016: Environmental Science and Pollution Research International
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