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5 – Soil Color Presentation

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Important/significant foundation soil
physical properties
Color
Redoximorphic features
Texture
Structure
Consistence
Coarse fragments
Reaction
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Important/significant foundation soil
physical properties
• Color – not an influence, but an indicator and
diagnostic resource
• Texture – the composition (sand, silt, clay),
the feel, the classification (triangle) micropores
• Structure – how the particles are aggregated,
bound together – macropores
• Consistence – how the soil holds together,
feels, can be worked when wet; assessing
texture
• Coarse fragments – rocks don’t hold water!
• Soil reaction – acid or base, leached or not
leached, saturated or not saturated
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• Color reflects physical, chemical and/or
biological composition and processes
• Dark brown-black = organic matter
• Bright-light = leached or bleached zones
• Subsoil color reflects parent material
• Subsoil color reflects redox status
oxidation = aerated
reduction = anaerobic, lacking oxygen
Carbonates, sulfates, chlorides affect color
Mottles, speckles, blotches – alternating wet
and dry conditions.
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Pop Quiz Question:
Direction of water flow?
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Soil color as a diagnostic tool
Color reflects the parent material, the soil formation
process, and the hydraulic properties of the soil
• There are two ways to �look at’ soil color –
• 1) as a diagnostic tool – what happened!
• 2) as a characterization/classification tool –
what will happen!
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Soil Color
Coloring agents in the soil Effect/expression of
Organic matter
darkens the soil
Iron (Fe):primary coloring
agent in the subsoil
orange brown colors associated
with well drained soils are the
result of Fe oxide stains coating
individual particles.
Manganese (Mn) is common very dark black or purplish black
in some soils
color
Matrix color
the dominant color in the soil
Mottling
spots or blotches of color in the soil
that differ from the matrix color
Redoximorphic features
mottles that relate to the aeration,
drainage, and alterations between
aerobic and anaerobic of the soil
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Redoximorphic features
mottles that relate to the aeration and drainage
status of the soil, and alterations between aerobic
and anaerobic conditions of the soil
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A
B
C
D
Deal or No Deal!
As a generalization – soils of fine, very uniform texture and very limited
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particle size distribution often have �internal drainage’ limitations.
Alisol – poorly drained clay loam
soil due to dense sub-surface
horizon rich in clay and
aluminum
Poorly drained silty clay
loam derived from alluvial
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deposits on a modern-day
flood plain
Deep, poorly drained fine
sandy loam formed in
sandy marine deposits,
flood-plains and depressions.
Shallow water table
Moderately well drained, slow
permeability, deep to water
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table. Smectite clay; high
shrink-swell properties
Soil colors associated with soil attributes.
Soil color
Soil
attributes
Environmental conditions
Brown to
black
(surface
horizon)
accumulation
of organic
matter (OM),
humus
low temperature, high annual precipitation
amounts, soils high in soil moisture, and/or litter
from coniferous trees favor an accumulation of OM
Black
(subsurface
horizon)
Accumulation
of manganese
Parent
material (e.g.
basalt)
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Bright-lightnearly white
Elluvial
horizon (E
horizon)
In environments where precipitation >
evapotranspiration there is leaching of sequioxides,
carbonates, and silicate clays. The elluviated
horizon consists mainly of silica
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Brown to black
(surface horizon);
surface well-drained,
good aeration.
Darker vertical soil
deposits are
remnants of
burrowing animals.
The technical term is
krotovina
(crotovina): an
animal burrow that
has been filled with
organic or mineral
material from another
soil horizon.
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Reddish brown
subsoil, suggesting
good drainage,
aeration. Note the
buried A horizon, with
additional subsoil
material above –
suggesting colluvial
deposition or some
form of mass action
in recent past. Zone
of elluviation below
the buried A horizon
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Bright-light; eluvial zone
below the relatively
shallow organic horizon
near surface; the lightcolored soils, the abundance
of red and yellow suggest
a well-drained soil. Considering that elluviation has also
occurred, one would conclude
that this would be a suitable
site – good internal drainage,
appears to have good water
holding capacity.
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Redox – reduction-oxidation status
• Reduction – oxygen is
depleted from the soil,
the soil may be
anaerobic, iron and
manganese chemistry
change, resulting in
color changes.
• Mottles/Gleying
• Oxidation – oxygen is
present in the soil, the
soil is aerobic, leaching
is likely occurring, light
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color of soil.
Yellow to
reddish
Fe
Well-aerated soils
Gray,
bluishgreen
Fe
Poorly drained soils (e.g.
subsurface layer with a
high bulk density causes
waterlogging, or a very fine
textured soil where
permeability is very low),
anaerobic environmental
conditions
White to
gray
In arid or subhumid
environments where the
Accumulation evapotranspiration >
of salts
precipitation there is an
upward movement of water
and soluble salts in the soil
White to
gray
Parent
material:
marl, quartz
(oxidized
iron)
3+
2+
(reduced
iron)
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An explanation of the Munsell color wheel and Munsell color charts
Hue: It is the dominant spectral
color, i.e., whether the hue is
pure color such as yellow, red,
green, or a mixture of pure
colors.
Value: It describes the degree of
lightness or brightness of the hue
reflected in the property of the
gray color that is being added to
the hue.
Chroma: It is the amount of a
particular hue added to a gray or
the relative purity of the hue.
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Standardizing Color – the Munsell Color Chart
• Munsell Color System
• Hue refers to the dominant
wavelength of light (color)
(red, yellow, green, etc.).
• Value refers to the lightness
and darkness of a color in
relation to a neutral gray
scale.
• Chroma is the relative purity
or strength of the Hue.
• Notation
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Hue = 5YR
Value = 2.5 – 8
Chroma = 1-8
So, for example: a soil
horizon with a Munsell
color description of 5YR
5/4 =
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Questions
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