THE EFFECTS OF ORGANIC MATTER, IRON OXIDES AND MOISTURE ON THE COLOR OF TWO AGRICULTURAL SOILS OF QUEBEC

1979 ◽  
Vol 59 (2) ◽  
pp. 191-202 ◽  
Author(s):  
S. CHOMCHAN ◽  
R. G. LEGER ◽  
G. J. F. MILLETTE
Keyword(s):  
Organic Matter ◽  
Iron Oxide ◽  
Iron Oxides ◽  
Agricultural Soils ◽  
Area Ratio ◽  
Oxide Coatings ◽  
Soil Color ◽  
Amorphous Iron ◽  
Reflectance Curve ◽  
Iron Oxide Coatings

A new spectrophotometric interpretation of the influence of organic matter, iron oxides and moisture on the soil color of the Ste-Sophie sand and the Ste-Rosalie clay is reported. The method is based on calculation of the area ratio of the reflected (area under the reflectance curve) against the absorbed (area over the reflectance curve). The higher the ratio the lighter is the soil. After treatment to remove organic matter and iron oxide coatings, both soils presented colors significantly lighter than those observed in untreated soils. Organic matter and amorphous iron oxide contributed for 78% and 64% of the color in the Ste-Sophie sand and in the Ste-Rosalie clay, respectively. Moisture tends to mask the effects of organic matter and iron oxides on soil color. Air-dried soils when compared to moistened soils were lighter in color.

Photodegradation, interaction with iron oxides and bioavailability of dissolved organic matter from forested floodplain sources

2008 ◽  
Vol 59 (9) ◽  
pp. 780 ◽  
Author(s):  
Julia A. Howitt ◽  
Darren S. Baldwin ◽  
Gavin N. Rees ◽  
Barry T. Hart
Keyword(s):  
Organic Matter ◽  
Iron Oxide ◽  
Dissolved Organic Matter ◽  
Iron Oxides ◽  
Photochemical Reactions ◽  
Oxbow Lake ◽  
Photochemical Degradation ◽  
Fluorescence Excitation ◽  
Amorphous Iron ◽  
Leaf Leachate

Photochemical degradation of dissolved organic matter (DOM) can influence food webs by altering the availability of carbon to microbial communities, and may be particularly important following periods of high DOM input (e.g. flooding of forested floodplains). Iron oxides can facilitate these reactions, but their influence on subsequent organic products is poorly understood. Degradation experiments with billabong (= oxbow lake) water and river red gum (Eucalyptus camaldulensis) leaf leachate were conducted to assess the importance of these reactions in floodplain systems. Photochemical degradation of DOM in sunlight-irradiated quartz tubes (with and without amorphous iron oxide) was studied using gas chromatography and UV-visible spectroscopy. Photochemical reactions generated gaseous products and small organic acids. Bioavailability of billabong DOM increased following irradiation, whereas that of leaf leachate was not significantly altered. Fluorescence excitation-emission spectra suggested that the humic component of billabong organic matter was particularly susceptible to degradation, and the source of DOM influenced the changes observed. The addition of amorphous iron oxide increased rates of photochemical degradation of leachate and billabong DOM. The importance of photochemical reactions to aquatic systems will depend on the source of the DOM and its starting bioavailability, whereas inputs of freshly formed iron oxides will accelerate the processes.

Facilitated Heterogeneous Photodegradation of Dissolved Organic Matter by Particulate Iron

2004 ◽  
Vol 1 (3) ◽  
pp. 197 ◽  
Author(s):  
Julia A. Howitt ◽  
Darren S. Baldwin ◽  
Gavin N. Rees ◽  
Barry T. Hart
Keyword(s):  
Organic Matter ◽  
Iron Oxide ◽  
Dissolved Organic Matter ◽  
Iron Oxides ◽  
Aquatic Ecosystems ◽  
Photochemical Reactions ◽  
Freshwater Systems ◽  
Particulate Iron ◽  
Presence And Absence ◽  
Australian Freshwater

Environmental Context. Iron oxides, as suspended minerals or as a colloidal phase, are common in Australian freshwater systems. Freshwater systems are also loaded with carbon-based substances, ‘dissolved organic matter’, but not all is biologically available as food to freshwater organisms. However, photochemical interactions between these iron oxides and dissolved organic matter provide a mechanism for biologically resistant carbon to re-enter the food web. Suspended iron oxides thus need to be considered in carbon cycles in aquatic ecosystems. Abstract. The photochemical degradation of dissolved organic matter (DOM) derived from the leaves of River Red Gum (Eucalyptus camaldulensis) was examined, with a particular focus on the photochemical generation of CO2, consumption of O2, and the effect of particulate iron minerals on these photochemical reactions. Solutions of leaf leachate were irradiated with ultraviolet and visible light in the presence and absence of amorphous iron oxides. Addition of fresh iron oxide was found to increase the rate of photodegradation of the organic matter by up to an order of magnitude compared to the reactions without added iron oxide. The ratio of CO2 produced to O2 consumed was ~1:1 in both the presence and absence of iron oxyhydroxide. The reactivity of the iron oxides was dependent on the preparation method and decreased with increased storage time. These results suggest that photochemical reactions on particle surfaces should be considered when examining carbon transformation in aquatic ecosystems, especially at sites with potential for the production of iron oxyhydroxides.

scholarly journals Friction and Wear Characteristics of Iron Oxide coatings

2003 ◽  
Vol 2003.41 (0) ◽  
pp. 281-282
Author(s):  
Yoshiki YAMAMOTO ◽  
Yasuo KONDO ◽  
Fumio OBATA ◽  
Kouitsu MIYACHIKA ◽  
Takao KOIDE ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Friction And Wear ◽  
Oxide Coatings ◽  
Wear Characteristics ◽  
Iron Oxide Coatings ◽  
Friction And Wear Characteristics

Characterization of iron oxide coatings prepared by MOCVD method from Fe(CO)5

2020 ◽  
Vol 30 ◽  
pp. 434-438 ◽  
Author(s):  
Polina G. Bespalova ◽  
Alexandr A. Vorobyev ◽  
Tatyana S. Kunkel ◽  
Alexandr L. Shakhmin ◽  
Maxim V. Mishin
Keyword(s):  
Iron Oxide ◽  
Oxide Coatings ◽  
Iron Oxide Coatings

Tritium exchange studies on metal oxide colloidal dispersions

1977 ◽  
Vol 30 (8) ◽  
pp. 1655 ◽  
Author(s):  
DE Yates ◽  
F Grieser ◽  
R Cooper ◽  
TW Healy
Keyword(s):  
Crystal Structure ◽  
Heat Treatment ◽  
Iron Oxide ◽  
Metal Oxide ◽  
Iron Oxides ◽  
Colloidal Dispersions ◽  
Water Interface ◽  
Amorphous Iron ◽  
Tio2 Rutile ◽  
Exchange Technique

The tritium exchange technique has been used to detemine the maximum number of surface protons at the oxide-water interface for oxide colloids including silicas, TiO2 (rutile) and the iron oxides goethite, hematite and amorphous iron oxide. The effects of heat treatment, crystal structure and exchange conditions are considered and tritium exchange values for the number of surface protons are compared with values calculated from crystal structures.

Carbonate rocks in the Mojave Desert as an analogue for Martian carbonates

2011 ◽  
Vol 10 (4) ◽  
pp. 349-358 ◽  
Author(s):  
Janice L. Bishop ◽  
Rachel T. Schelble ◽  
Christopher P. McKay ◽  
Adrian J. Brown ◽  
Kaysea A. Perry
Keyword(s):  
Iron Oxide ◽  
Mojave Desert ◽  
Carbonate Rocks ◽  
Thermal Emission ◽  
Soil Environment ◽  
X Ray Diffraction ◽  
Oxide Coatings ◽  
Imaging Spectrometer ◽  
Iron Oxide Coatings ◽  
Rock Coatings

AbstractCarbonate rocks in the Mojave Desert are presented as potential analogues for the carbonates on Mars. Rocks collected from the Little Red Hill site contain iron oxide-bearing coatings that greatly suppress the spectral features due to carbonate of the underlying material and impart a spectral slope. The Mojave Desert was formerly a lush pedogenic soil environment that, over time, transformed into the current arid climate with abundant rock varnish. One niche for microbes in the current desolate environment is inside and underneath the rocks where the microbes profit from solar protection by the iron oxide rock coatings. Carbonates were long predicted to be present on Mars and have recently been detected by instruments on Phoenix and MER and using hyperspectral orbiters such as the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), the Planetary Fourier Spectrometer (PFS) and the Thermal Emission Spectrometer (TES). We describe here the results of a study of carbonate rocks from the Little Red Hill site of the Mojave Desert that includes X-ray diffraction (XRD), chemistry and visible-infrared reflectance spectroscopy. Coatings on the carbonate rocks greatly reduced the strength of the carbonate bands and caused changes in the shape of some bands. We compare these data with a carbonate outcrop at Nili Fossae, Mars. If microbes once inhabited Mars, similar carbonate rocks with iron oxide coatings could have provided a UV-protected niche there as well. Thus, analysis of carbonate-bearing regions on Mars by future landers would be useful sites to search for biosignatures.

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