Moisture Effects on Visible Spectral Characteristics of Lateritic Soils

Bedidi, Ali; Cervelle, Bernard; Madeira, José Valdo; Pouget, Marcel

doi:10.1097/00010694-199202000-00007

Cited by 64 publications

(34 citation statements)

References 13 publications

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“…Thereby, soil water content cannot generally be obtained from visible-NIR spectral data. However, in the case of red soils from Brazil, Bedidi et al (1992) have recently found that spectra of wetted soils are not homothetic with the ones of die same soils in dry condition. These iron-rich soils present a spectral 'shift' of the inflexion point of the reflectance curve when the water content increases (figure 6).…”

Section: Potential Of Spectrometry For Soil Organic Carbonmentioning

confidence: 98%

“…With the help of an integrating sphere and of a calibrated white standard, the spectral reflectance of small samples can be easily computed with a spectrophotometer. Soil samples may be scanned after a simple air drying and sieving, but a more rigorous approach requires grinding down to a standard size (see Fernandez and Schulze, 1987;Bedidi et al, 1992 for more details).…”

Section: Laboratory Measurementsmentioning

confidence: 99%

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Soil Spectral Properties and Their Relationships with Environmental Parameters - Examples from Arid Regions

Escadafal

1994

Eurocourses: Remote Sensing

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ABSTRACT. The development of global studies on terrestrial environments has led to a renewed interest in soils. In addition to supporting and nourishing the biomass, soils play a very important interface and buffer function in the ecosystems. For instance, large parts of the carbon, water and gases fluxes are controlled by soils which can be referred as the 'skin' of terrestrial ecosystems. Remote sensing techniques are essential in the global approach and links between soil properties and spectral features have been investigated. New instruments currently enable to measure these features with high resolution. In this paper we will first summarise the techniques used to measure soil spectra in the laboratory, in the field and remotely. Then, we will discuss the relationships between the shapes of the spectral reflectance curves observed and the soil composition (organic carbon, iron oxides, and hydrous minerals, particularly). The spectral characteristics of aridic soils and their use as 'desertification' indicators will illustrate the potential of imaging spectrometry for the assessment of environmental changes through the detection of soil surface spectral variations. Finally, the example of simulated impact of soils on the remote measurement of vegetation parameters will enable to conclude on the necessity of giving more consideration to soils and their spectral variability.

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Section: Potential Of Spectrometry For Soil Organic Carbonmentioning

confidence: 98%

Section: Laboratory Measurementsmentioning

confidence: 99%

Soil Spectral Properties and Their Relationships with Environmental Parameters - Examples from Arid Regions

Escadafal

1994

Eurocourses: Remote Sensing

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“…These were converted into polar coordinates of three color spaces: (1) hue, chroma, and value of the Munsell system (Fernandez and Schulze, 1987), (2) hue, chroma, and lightness (equivalent to value) of the CIE-L*a*b* system (Melville and Atkinson, 1985), and (3) the dominant wavelength (equivalent to hue), the excitation purity (equivalent to chroma), and the lightness of the basic, non-uniform chromaticity system (Bedidi et al, 1992). Because the observed trends of color were identical in all three systems, results are shown for the Munsell system only.…”

Section: Spectral Measurements and Color Calculationsmentioning

confidence: 99%

Diffuse Reflectance Spectra of Al Substituted Goethite: A Ligand Field Approach

Scheinost

Schulze

Schwertmann

1999

Clays and clay miner.

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Abstract--Previous investigations of goethite revealed a substantial variation of color and diffuse reflectance spectxa (DRS) in the extended visible range (350-2200 nm). To better understand the causes of this variability and to assess the potential of DRS as a mineralogical tool, we investigated the DRS of pure and Al-substituted goethite, c~-Fej_~AI~OOH with x from 0 to 0.33, and mean crystal lengths (MCL) from 170 to 1800 nm. The strongly overlapping ligand field bands were extracted by fitting the single-electron transitions 6A l --~ 4Tt, 6A 1 ----) 4T2, 6A 1 ~ (4E; hA1), and 6A I --~ 4E(~D) as functions of the ligand field splitting energy, 10 Dq, and the interelectronic repulsion parameters, Racah-B and -C. With x increasing from 0 to 0.33, 6A 1 ---)' aT / decreased from 10,590 to 10,150 cm -1 (944 to 958 nm), and 6A l ~ 4T 2 decreased from 15,310 to 14,880 cm 1 (653 to 672 nm), while 10 Dq increased from 15,770 to 16,220 cm -1. From the change of 10 Dq we calculated a decrease of the Fe-(O,OH) distances from 202.0 to 200.9 pm (-0.5%). This decrease is smaller than the average decrease of all (A1,Fe)-(O,OH) distances (-1.8%) calculated from the change of the unit-cell lengths (UCL). That is, there remains a substantial difference in size between the larger Fe-and the smaller Al-occupied octahedra in the solid solution which may indicate the existence of diaspore clusters within the goethite structure. The increasing strain in the crystal structure due to the size mismatch and limited contractibility of the oxygen cage around Fe may be the primary reason for AI substitution being restricted to x < 0.33. The bands 6A l ~ (4E; 4Aa) and 6A 1 ~ 4E(4D) did not shift, indicating a constant covalency of the Fe-(O,OH) bonds with B = 628 cm ~ and C = 5.5B. Whereas variation of band energies could be explained in terms of the Fe-(O,OH) ligand field, the variation of color and band intensities was mainly determined by crystal size. Although our study confirmed the potential of DRS for mineralogical investigations, there is still a gap between the fundamental theory and the explanation of some spectral features.

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“…This was observed in the present study (Figures 2 and 3) and is likely due to the presence of minerals having different spectral properties, variations in organic matter content, and the substitution of foreign ions (e.g., aluminum) in iron oxides. Moisture effects on soil color are negligible since only dry colors were determined (Bedidi et al 1992).…”

Section: Discussionmentioning

confidence: 99%

Soil color variations along an iron oxide gradient in a mine drainage treatment wetland

Tarutis

Unz

1994

Wetlands

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The relationship between soil color and iron oxide content in a surface-flow constructed wetland that successfully treats acid mine drainage (AMD) is examined with regard to its potential importance to wetland treatment of AMD. Twenty-one oxidized surficial soil samples (< 5 cm depth) were collected along a 100-meter wetland transect and were characterized for Munsell color and iron oxide content. Soil color, expressed in terms of both a redness index as well as dominant wavelength, was found to be significantly correlated Lo < 0.001) with iron oxide content. In addition, an apparent red-shift in soil color was observed from the wetland effluent toward the influent in response to increasing concentrations of iron in both the soil and the drainage water. If this relationship between soil color-iron oxide content-iron removal is shown to exist for other surface-flow AMD wetlands, evaluation of soil color can give a relatively quick and inexpensive estimate of iron retention for a given influent iron concentration entering a wetland.

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Moisture Effects on Visible Spectral Characteristics of Lateritic Soils

Cited by 64 publications

References 13 publications

Soil Spectral Properties and Their Relationships with Environmental Parameters - Examples from Arid Regions

Soil Spectral Properties and Their Relationships with Environmental Parameters - Examples from Arid Regions

Diffuse Reflectance Spectra of Al Substituted Goethite: A Ligand Field Approach

Soil color variations along an iron oxide gradient in a mine drainage treatment wetland

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