Iron Oxides: An Example of Structural Versatility

Metal Oxide Nanostructures Chemistry ◽

10.1093/oso/9780190928117.003.0010 ◽

2019 ◽

Author(s):

Jean-Pierre Jolivet

Keyword(s):

Iron Oxides ◽

Natural Waters ◽

Active Centers ◽

Large Variability ◽

Oxygenated Compounds ◽

Crystal Structural ◽

Living Organisms ◽

Inorganic Ligands ◽

And Storage ◽

Microbial Mediation

Iron is Earth’s fourth most widespread element (6.2% in mass), behind oxygen, silicon, and aluminum. It exists mostly as ferric oxide and oxyhydroxide (Fig. 7.1a) and to a lesser extent as sulfide (pyrite), carbonate (siderite), and silicate (fayalite). Iron oxides are largely used in technological areas such as metallurgy, colored pigments, magnetic materials, and catalysts. They also play an important role in the environment because the dissolution of ferric oxides in natural waters, promoted by acid–base, redox, photochemical phenomena, and also microbial mediation, allows iron to be involved in many biogeochemical processes. Iron is present in many living organisms such as plants, bacteria, mollusks, animals, and humans in various forms: . . . Porphyrinic complexes of iron, which are active centers of hemoglobin and several ferredoxins involved in biological functions, especially respiration mechanism and photosynthesis. Nanoparticles of amorphous ferric oxyhydroxides in animal and human organisms as ferritin, which allows regulation and storage of iron and in various nanophases present in plants as phytoferritin. Crystalline iron oxy(hydroxi)des produced by biomineralization processes. Goethite, lepidocrocite, and magnetite are the main constituents of radulas and the teeth of mollusks (limpets, chitons). Magnetite nanoparticles produced by magnetotactic bacteria (Fig. 7.1b), as well as by bees and pigeons, are used for purposes of orientation and guiding along the lines of force of the Earth’s magnetic field. Green rusts are also ferric- ferrous compounds belonging to the biogeochemical cycle of iron. . . . The crystal chemistry of iron oxy(hydroxi)des is very rich. The ferric, ferrous, and mixed ferric- ferrous oxygenated compounds correspond to around a dozen crystal structural types (Fig. 7.2). Most of these crystal phases can be synthesized from solutions in the laboratory, giving rise to a most diversified chemistry. They are also formed in nature because of the large variability of physicochemical conditions: an acidity range from around pH 0 to 13; redox conditions from oxic to totally anoxic media; bacterial activity that can be extremely intense; salinity largely varying from almost pure waters to real brines; presence of many organic and inorganic ligands; and various photochemical processes.

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Determination of Glyphosate Herbicide and (Aminomethyl)phosphonic Acid in Natural Waters by Liquid Chromatography Using Pre-Column Fluorogenic Labeling with 9-Fluorenylmethyl Chloroformate

Journal of AOAC INTERNATIONAL ◽

10.1093/jaoac/69.3.458 ◽

1986 ◽

Vol 69 (3) ◽

pp. 458-461 ◽

Cited By ~ 2

Author(s):

Carl J Miles ◽

Louis R Wallace ◽

H Anson Moye

Keyword(s):

Liquid Chromatography ◽

Phosphonic Acid ◽

Natural Waters ◽

Sample Pretreatment ◽

Fluorescence Detector ◽

Rotary Evaporation ◽

Glyphosate Herbicide ◽

And Storage ◽

Aminomethyl Phosphonic Acid

Abstract An analytical method has been developed for determination of glyphosate herbicide and its major metabolite, (aminomethyl)phosphonic acid (AMFA), in natural waters. Sample pretreatment consisted of filtration, addition of phosphate buffer, concentration by rotary evaporation, and a final filtration before derivatization with 9-fluorenylmethyl chloroformate. The derivatives were separated by anion exchange liquid chromatography and measured with a fluorescence detector. Standard curves were linear over 3 orders of magnitude and minimal detectable quantities were 10 ng/mL for glyphosate and 5 ng/mL for AMPA. The 20-fold concentration factor realized in sample preparation corresponds to ppb method detection limits for glyphosate and AMPA in natural waters. Recovery and storage studies were performed and are discussed.

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Uranium Speciation and Bioavailability in Aquatic Systems: An Overview

The Scientific World JOURNAL ◽

10.1100/tsw.2002.130 ◽

2002 ◽

Vol 2 ◽

pp. 707-729 ◽

Cited By ~ 117

Author(s):

Scott J. Markich

Keyword(s):

Surface Waters ◽

Metal Ion ◽

Natural Waters ◽

Analytical Techniques ◽

Time Resolved ◽

Analytical Technique ◽

Major Form ◽

Uranyl Carbonate ◽

Inorganic Ligands ◽

The Relationship

The speciation of uranium (U) in relation to its bioavailability is reviewed for surface waters (fresh- and seawater) and their sediments. A summary of available analytical and modeling techniques for determining U speciation is also presented. U(VI) is the major form of U in oxic surface waters, while U(IV) is the major form in anoxic waters. The bioavailability of U (i.e., its ability to bind to or traverse the cell surface of an organism) is dependent on its speciation, or physicochemical form. U occurs in surface waters in a variety of physicochemical forms, including the free metal ion (U4+or UO22+) and complexes with inorganic ligands (e.g., uranyl carbonate or uranyl phosphate), and humic substances (HS) (e.g., uranyl fulvate) in dissolved, colloidal, and/or particulate forms. Although the relationship between U speciation and bioavailability is complex, there is reasonable evidence to indicate that UO22+and UO2OH+are the major forms of U(VI) available to organisms, rather than U in strong complexes (e.g., uranyl fulvate) or adsorbed to colloidal and/or particulate matter. U(VI) complexes with inorganic ligands (e.g., carbonate or phosphate) and HS apparently reduce the bioavailability of U by reducing the activity of UO22+and UO2OH+. The majority of studies have used the results from thermodynamic speciation modeling to support these conclusions. Time-resolved laser-induced fluorescence spectroscopy is the only analytical technique able to directly determine specific U species, but is limited in use to freshwaters of low pH and ionic strength. Nearly all of the available information relating the speciation of U to its bioavailability has been derived using simple, chemically defined experimental freshwaters, rather than natural waters. No data are available for estuarine or seawater. Furthermore, there are no available data on the relationship between U speciation and bioavailability in sediments. An understanding of this relationship has been hindered due to the lack of direct quantitative U speciation techniques for particulate phases. More robust analytical techniques for determining the speciation of U in natural surface waters are needed before the relationship between U speciation and bioavailability can be clarified.

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Trace Elements in the Mainstem Amazon River

The Biogeochemistry of the Amazon Basin ◽

10.1093/oso/9780195114317.003.0019 ◽

2001 ◽

Author(s):

Patrick T. Seyler ◽

Gerald R. Boaventura

Keyword(s):

Trace Metals ◽

Amazon Basin ◽

Natural Waters ◽

River System ◽

Scientific Basis ◽

Essential Elements ◽

Amazon River ◽

Industrialized Countries ◽

Control Evaluation ◽

Living Organisms

Measurements of trace metals in rivers are of substantial interest for researchers examining basic scientific questions related to geochemical weathering and transport and to scientists involved in pollution control evaluation. Trace metals in natural waters include essential elements such as cobalt, copper, zinc, manganese, iron, molybdenum, nickel, which may also be toxic at higher concentrations, and nonessential elements, which are toxic, such as cadmium, mercury and lead. Recent findings indicate that iron and, to a lesser extent, zinc and manganese play an important role in regulating the growth and ecology of phytoplankton (Martin et al. 1991), while in contrast, cadmium, arsenic, and mercury have long been recognized as poisonous to living organisms (see Pfeiffer et al. 1993, for a description of mercury problem in the Amazon basin). The release of potentially large quantities of these toxic metals, particularly in the river systems of industrialized countries, but also in tropical rivers, is an acute problem of great environmental concern. An understanding of the weathering and transport processes controlling the fate and flux of trace metals in pristine environments is important in evaluating the capacity of receiving waters to accommodate wastes without detrimental effects. The Amazon River system, which is relatively free of industrial and agricultural interference, represents an ideal case for the investigation of the origin and transport of trace metals. This understanding may also provide a scientific basis for the anticipated development of the Amazon basin. With regard to trace metals, Amazon River is still poorly documented. Martin and Meybeck (1979) and Martin and Gordeev (1986) presented a global tabulation of trace metal concentrations in particulate matter of major rivers including the Amazon, and Palmer and Edmond (1992) measured dissolved Fe, Al, and Sr concentrations in the Amazon mainstream and a number of its tributaries. Boyle et al. (1982) and Gordeev et al. (1990) published some data on Cu, Ni, Cd, and Ag dissolved concentrations at the mouth of the Amazon River and in its oceanic plume. Konhauser et al. (1994) reported the trace and rare earth elemental composition of sediments, soils and waters, mainly in the region of Manaus.

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Comparative assessment of drinking water quality of individual settlements of Mogils-Podilsky district of Vinnitsa region

Biological Systems: Theory and Innovation ◽

10.31548/biologiya2020.03.007 ◽

2020 ◽

Vol 11 (3) ◽

Author(s):

О.О. Kravchenko ◽

◽

В.М. Galimova ◽

V.A. Kopilevich ◽

А.М. Churilov ◽

...

Keyword(s):

Water Quality ◽

Water Supply ◽

Natural Waters ◽

Environmental Safety ◽

Cellular Level ◽

Nitrogen Fertilizers ◽

Actual Problem ◽

Cadmium Lead ◽

Living Organisms

The work is devoted to the actual problem of environmental safety and quality assessment of various water sources Mohyliv-Podilsky district of Vinnitsa region. It has been carried out hydrochemical analysis and calculated an index of pollution of natural waters, biological testing performed using a battery of test organisms, given recommendations to improve the water quality of the study area.It has been established that the most indicative parameters of pollution of water supply sources are hardness indicators, concentration of cadmium, lead, nitrates. None of the investigated sources have corresponded to the “clean water” indicator. Water samples that as a result of hydro-chemical analysis had been characterized by relatively safe, exhibited chronic toxicity for invertebrates. It has been found that water from a centralized source is characterized by the acute toxicity and leads to changes in living organisms at the cellular level. It is recommended to carry out quarterly water sampling in the indicated sources; minimization of the use of nitrogen fertilizers in settlements, in particular, near water supply sources.

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Chemical Speciation of Hg(II) with Environmental Inorganic Ligands

Australian Journal of Chemistry ◽

10.1071/ch04063 ◽

2004 ◽

Vol 57 (10) ◽

pp. 993 ◽

Cited By ~ 19

Author(s):

Kipton J. Powell ◽

Paul L. Brown ◽

Robert H. Byrne ◽

Tamas Gajda ◽

Glenn Hefter ◽

...

Keyword(s):

Organic Matter ◽

Complex Formation ◽

Numerical Modelling ◽

Thermodynamic Data ◽

Natural Waters ◽

Chemical Speciation ◽

Interaction Coefficients ◽

Low Concentrations ◽

The Common ◽

Inorganic Ligands

Abstract Complex formation between Hg(ii) and the common environmental ligands Cl−, OH−, CO32−, SO42−, and PO43− can have profound effects on Hg(ii) speciation in natural waters with low concentrations of organic matter. Hg(ii) is labile, so its distribution among these inorganic ligands can be estimated by numerical modelling if reliable values for the relevant stability constants are available. A summary of critically reviewed constants and related thermodynamic data is presented. Recommended values of log10βp,q,r° and the associated reaction enthalpies, ΔrHm°, valid at Im = 0 mol kg−1 and 25°C, along with the equations and specific ion interaction coefficients required to calculate log10βp,q,r values at higher ionic strengths and other temperatures are also presented. Under typical environmental conditions Hg(ii) speciation is dominated by the reactions Hg2+ + 2Cl− ↔ HgCl2(aq) (log10β2° = 14.00 ± 0.07), Hg2+ + Cl− + H2O ↔ Hg(OH)Cl(aq) + H+ (log10β° = 4.27 ± 0.35), and Hg2+ + 2H2O ↔ Hg(OH)2(aq) + 2H+ (log10*β2° = −5.98 ± 0.06).

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Toxicity of Heavy Metals to the Marine Diatom Ditylum Brightwellii (West) Grunow: Correlation between Toxicity and Metal Speciation

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315400024280 ◽

1980 ◽

Vol 60 (1) ◽

pp. 227-242 ◽

Cited By ~ 72

Author(s):

G. S. Canterford ◽

D. R. Canterford

Keyword(s):

Heavy Metals ◽

Organic Matter ◽

Dissolved Organic Matter ◽

Natural Waters ◽

Chelating Agents ◽

Sea Water ◽

Metal Speciation ◽

Marine Diatom ◽

Dissolved Organic Compounds ◽

Inorganic Ligands

The possibility of dissolved organic compounds acting as complexing or chelating agents in natural waters has received considerable attention in the last two to three decades. Stumm & Morgan (1970) have expressed doubts about the existence of humicmetal ion complexes in natural waters. Strickland (1972) has also stated that although the addition of chelating agents to sea water often improved the growth of phytoplankton, there was little evidence that the function of dissolved organic matter in oceans and lakes was to complex metals so as to increase or decrease their availability to phytoplankton. Strickland argued that even if all dissolved organic carbon were present as a compound of strong complexing ability it would not be able to compete for most metals with inorganic ligands such as chloride, sulphate and hydroxide. However, there is an increasing amount of data indicating that metals in natural waters may exist in chelated forms with dissolved organic matter (see, for example, Davey, Morgan & Erickson, 1973; Chau & Lum-Shue-Chan, 1974).

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Dissection and prediction of RNA-binding sites on proteins

BioMolecular Concepts ◽

10.1515/bmc.2010.037 ◽

2010 ◽

Vol 1 (5-6) ◽

pp. 345-355 ◽

Cited By ~ 4

Author(s):

Laura Pérez-Cano ◽

Juan Fernández-Recio

Keyword(s):

Binding Sites ◽

Binding Proteins ◽

Rna Binding ◽

Rna Binding Proteins ◽

Large Variability ◽

Regulatory Processes ◽

Points Of View ◽

Living Organisms ◽

Positively Charged ◽

Rna Binding Sites

AbstractRNA-binding proteins are involved in many important regulatory processes in cells and their study is essential for a complete understanding of living organisms. They show a large variability from both structural and functional points of view. However, several recent studies performed on protein-RNA crystal structures have revealed interesting common properties. RNA-binding sites usually constitute patches of positively charged or polar residues that make most of the specific and non-specific contacts with RNA. Negatively charged or aliphatic residues are less frequent at protein-RNA interfaces, although they can also be found either forming aliphatic and positive-negative pairs in protein RNA-binding sites or contacting RNA through their main chains. Aromatic residues found within these interfaces are usually involved in specific base recognition at RNA single-strand regions. This specific recognition, in combination with structural complementarity, represents the key source for specificity in protein-RNA association. From all this knowledge, a variety of computational methods for prediction of RNA-binding sites have been developed based either on protein sequence or on protein structure. Some reported methods are really successful in the identification of RNA-binding proteins or the prediction of RNA-binding sites. Given the growing interest in the field, all these studies and prediction methods will undoubtedly contribute to the identification and comprehension of protein-RNA interactions.

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Photoreductive dissolution of colloidal iron oxides in natural waters

Environmental Science & Technology ◽

10.1021/es00129a010 ◽

1984 ◽

Vol 18 (11) ◽

pp. 860-868 ◽

Cited By ~ 189

Author(s):

T. David. Waite ◽

Francois M. M. Morel

Keyword(s):

Iron Oxides ◽

Natural Waters ◽

Colloidal Iron

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Chemical speciation of environmentally significant metals with inorganic ligands Part 2: The Cu2+-OH-, Cl-, CO32-, SO42-, and PO43- systems (IUPAC Technical Report)

Pure and Applied Chemistry ◽

10.1351/pac200779050895 ◽

2007 ◽

Vol 79 (5) ◽

pp. 895-950 ◽

Cited By ~ 114

Author(s):

Kipton J. Powell ◽

Paul L. Brown ◽

Robert H. Byrne ◽

Tamás Gajda ◽

Glenn Hefter ◽

...

Keyword(s):

Natural Waters ◽

Chemical Speciation ◽

Formation Constants ◽

Water Systems ◽

Interaction Coefficients ◽

Low Concentrations ◽

Technical Report ◽

The Common ◽

A Minor ◽

Inorganic Ligands

Complex formation between CuII and the common environmental ligands Cl-, OH-, CO32-, SO42-, and PO43- can have a significant effect on CuII speciation in natural waters with low concentrations of organic matter. Copper(II) complexes are labile, so the CuII distribution amongst these inorganic ligands can be estimated by numerical modeling if reliable values for the relevant stability (formation) constants are available. This paper provides a critical review of such constants and related thermodynamic data. It recommends values of log10βp,q,r° valid at Im = 0 mol kg-1 and 25 °C (298.15 K), along with the equations and specific ion interaction coefficients required to calculate log10βp,q,r values at higher ionic strengths. Some values for reaction enthalpies, ΔrHm, are also reported where available. In weakly acidic fresh water systems, in the absence of organic ligands, CuII speciation is dominated by the species Cu2+(aq), with CuSO4(aq) as a minor species. In seawater, it is dominated by CuCO3(aq), with Cu(OH)+, Cu2+(aq), CuCl+, Cu(CO3)OH-, Cu(OH)2(aq), and Cu(CO3)22- as minor species. In weakly acidic saline systems, it is dominated by Cu2+(aq) and CuCl+, with CuSO4(aq) and CuCl2(aq) as minor species.

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