Muhammad Fahad Ansari 12IEEM14

1. Terrestrial Environment
Muhammad Fahad Ansari
12IEEM14

2. surface soil, the vadose
zone, and the saturated
zone

3. Spontaneous
water
movement
Saturated zone
Capillary fringe (nearly saturated)
Vadose zone (unsaturated)
Surface soil (unsaturated)
Scale
can
range
from
10
to
100’s
of
meters Water table
X
Surface soils
Vadose zone
Saturated zone
shallow aquifers
intermediate aquifers
deep aquifers

4. 1) 45% mineral (Si, Fe, Al, Ca, K, Mg, Na)
The two most abundant elements in the earth’s crust are Si
(47%) and O (27%)
Quartz = SiO2
Clay minerals are aluminum silicates
Nonsilicates = NaCl, CaSO4 (gypsum), CaCO3 (calcite)
Pore space
Mineral
OM
Components of a typical soil
2) 50% pore space
3) 1 to 5% organic matter

5. Soil texture – this defines the mineral particle sizes that make
up a particular soil.
particle diameter Surface to volume ratio
range (mm) (cm2/g)
Sand: 0.05 – 2 mm 50
Silt: 0.002 – 0.05 mm 450
Clay: 0.0002 – 0.002 mm 10,000

6. Pore size distribution is important when one considers movement of fluids and
of microbes through a porous medium. Protozoa and bacteria will have
difficulty moving through even sandy porous media.
Similarly fluids like water move more easily through large pores, not because
the water molecules are too large, but because there is less resistance to
water movement through larger spaces.
Fine Coarse
Number
of
pores
Fine Coarse
Number
of
pores Fine Coarse
Number
of
pores
Clay texture Loam texture Sand texture
The amount of clay and organic matter in a soil influence the reactivity of that soil
because they both add surface area and charge. Because large amounts of clay
make the texture of the soil much finer, the average pore size is smaller.
Texture and pore size distribution

7. Filtration is important when the size of
the bacterium is greater than 5% of the
mean diameter of the soil particles
20 um 0.6-20 um 0.02–0.6 um
Pore size
5% of the
mean pore
diameter

8. Water movement and soil water potential
Soil water potential depends on
how tightly water is held to a soil
surface. This in turn depends on
how much water is present.
Surface forces have water
potentials ranging from –
10,000 to –31 atm.
Capillary forces have water
potentials ranging from –31 to
–0.1 atm. Optimal microbial
activity occurs at
approximately -0.1 atm.
At greater distances there is
little force holding water to the
surface. This is considered
free water and moves
downward due to the force of
gravity.
Soil air
FREE WATER
Gravitational
forces
Capillary
forces
Surface
forces
Soil
particles
% Saturation of
the soil pore
100%
0%
A m
Soil air
Increasing distance from particle surface
Soil air
FREE WATER
Gravitational
forces
Capillary
forces
Surface
forces
Soil
particles
% Saturation of
the soil pore
100%
0%
A m
Soil air
Increasing distance from particle surface
Soil air
FREE WATER
Gravitational
forces
Capillary
forces
Surface
forces
Soil
particles
% Saturation of
the soil pore
100%
0%
A m
Soil air
Increasing distance from particle surface
Soil air
FREE WATER
Gravitational
forces
Capillary
forces
Surface
forces
Soil
particles
% Saturation of
the soil pore
100%
0%
A m
Soil air
Increasing distance from particle surface

9. Soil atmosphere
The composition of the earth’s atmosphere is approximately 79%
nitrogen, 21% oxygen, and 0.03% carbon dioxide. Microbial activity in
the soil can change the local concentration of these gases especially in
saturated areas.
0.03
0.3 – 3
Up to 10
20.9
18 - 20.5
0 - 10
78.1
78.1
>79
Atmosphere
Well-aerated surface soil
Fine clay/saturated soil
Carbon Dioxide (CO2)
Oxygen (O2)
Nitrogen (N2)
Location
Composition (% volume basis)

10. Microorganisms in soil – an overview
• minor role as primary producers
• major role in cycling of nutrients
• role in soil formation
• role in pollution abatement

11. Bacteria
Culturable counts 106 – 108 CFU/g soil
Direct counts 107 – 1010 cells/g soil
Estimated to be up to 10,000 species of bacteria/g soil
Actinomycetes
Culturable counts 106 – 107 CFU/g soil
Gram Positive with high G+C content
Produce geosmin (earthy smell) and antibiotics
Fungi
Culturable counts 105 – 106/g soil
Obligate aerobes
Produce extensive mycelia (filaments) that can cover large areas.
Mycorrhizae are associated with plant roots.
White rot fungus, Phanerochaete chrysosporium is known for its ability to
degrade contaminants.
Highest
numbers
Highest
biomass
Numbers and types of microbes in typical surface soils

12. Comparison of bacteria, actinomycetes, and fungi
Bacteria Actinomycetes Fungi
Numbers highest intermediate lowest
Biomass --- similar biomass --- largest
Cell wall --- PEP, teichoic acid, LPS --- chitin/cellulose
Competitiveness most least intermediate
for simple organics
Fix N2 Yes Yes No
Aerobic/Anaerobic both mostly aerobic aerobic
Moisture stress least tolerant intermediate most tolerant
Optimum pH 6-8 6-8 6-7
Competitive pH 6-8 >8 <5
Competitiveness all soils dominate dry, dominate
high pH soils low pH soils

13. The Aquatic Environment
Outline:
– Water cycle
– Properties of water
– Light and temperature in aquatic environments
– Oxygen and carbon dioxide in water
– Water movement in streams
– Tides and estuaries

14. Water or hydrologic cycle

15. Water storages and fluxes

16. •High specific heat:
•Specific heat: number of calories necessary to raise 1
gram of water 1 degree Celsius
•Peculiar density-temperature relationship:
pure water most dense when at 4 degrees
Celsius.
Physical properties of water

17. Physical conditions in the aquatic environment
– Light
–Temperature
–Oxygen
–Salinity
–Acidity

18. Physical conditions:
1. Light
• Some incident sunlight is
reflected from the water’s
surface
• The lower the angle of the
sun, the greater the
reflectance
 The amount of light that
penetrates the water’s
surface varies with latitude,
season
• Light that does penetrate is
absorbed by water
molecules…

19. Fig. 4.6

20. • Different wavelengths penetrate to different
depths
• E.g. for visible light:
– Red: most rapidly absorbed
– Blue: least rapidly absorbed --> greatest
penetration
• Suspended particles in the water also absorb
and scatter light --> reduces penetration even
further

21. Physical conditions
2. Temperature
• Water is most dense at 4oC
• Lake in summer:
– temperature drops with increasing depth
– Stratification of water column
•Epilimnion: warm surface water
•Thermocline: rapid decline in temperature
•Hypolimnion: cold, dense water (~4oC)

23. Temperature
• Tropical lakes: thermocline all year
• Temperate lakes: only in summer
– Autumn: surface cools --> temperature becomes
uniform throughout (~4oC)
Mixing of all parts = fall turnover
– Increased nutrient levels at the surface

24. Fig. 4.7

25. Temperature
• Temperate lakes in winter
– surface colder than 4oC
– Bottom near 4oC
• Temperate lakes in spring
– Ice melts --> surface warms --> ~4oC throughout
Spring turnover

26. Temperature
• Oceans: never undergo complete turnover
• Winter: thermocline rises
• Summer: thermocline descends
Bottom never mixes with top

27. Temperature
• Flowing waters: temperature variable
• Shallow waters: follow air temperature
– Track changes slowly

29. Physical conditions:
3. Oxygen
• Diffuses from air through surface
• Solubility decreases as water temperature
increases
• Solubility decreases as salinity increases
• Diffusion: 10,000 times slower than in air
Mixing of water by winds and currents is
critical
• Temperature stratification --> oxygen
stratification

31. Oxygen
Oceans: Highest conc. near surface (upper 10-
20m)
– Photosynthesis
– Wind mixing
• Decreases to minimum at 500-1,000 m
– Oxygen minimum zone
– No turnover --> water never reoxygenated
• Below 1,000 m : conc. increases again
– Polar regions: surface (high conc.) waters cool,
sink --> currents --> highly oxygenated deep
waters carried to lower latitudes

33. Physical conditions:
4. Salinity
• Flow of rivers into ocean: dissolved materials
increase over time
• Concentrations can’t increase beyond
maximum solubility limit.
– e.g. Ca2+ forms CaCO3 (limestone)
– e.g. Cl- - highly soluble (max. 360 g/L)
• Maximum not yet reached (today 19 g/L)
• Total concentration of all salt in ocean: 3.5%
or 35 ppt
• Fresh water 0.065 to 0.3 ppt

34. Physical conditions:
5. Acidity

36. Factors affecting pH
• Fresh water: underlying rock is important
– Limestone:
• raises pH
• buffers against changes
– Sandstone, granite
• Lowers pH
• Oceans: Na+, K+, Ca2+ raise pH
– pH ~ 7.5-8.4

37. Effect of pH on living organisms
• Direct effects: interference with physiological
processes
• Indirect effects: effect on other dissolved
substances
– E.g. Al3+: concentration increases below pH 5
• Insoluble at higher pH

38. Water Movement
Fast flow --> rocky bottom Slow flow --> silty bottom
Increase in water volume  increase flow rate

39. The Terrestrial Environment
Outline:
• Life on land
• Light and vegetation
• Soils
– formation
– horizons
– moisture holding
capacity
– ion exchange
Readings: Ch. 5

40. …is a hostile environment
• Living cells 75-95% water; must remain
hydrated to survive
• Water availability fluctuates with
precipitation patterns
Constraints:
1. Desiccation
• Terrestrial organisms have adaptations that
reduce water loss, and/or replace lost water

41. 2. Structural support
• Trees invest > 80% of their mass in supportive woody tissue
• Animals: skeletons

42. Terrestrial env’t - constraints
3. Temperature variations on land >> those in
the water

43. Physical conditions
1. Light availability

44. Leaf area index

45. Orientation of leaves

46. Daily distribution of light

47. Seasonal distribution of light

48. Soil
1. Formation
• Begins with weathering of rocks
• Types of weathering:
i. Mechanical --> breakup
• Freezing / thawing
• Erosion
• Roots
ii. Chemical
• Oxidation
• Acids
• Rainwater acts as medium for reactions

49. Factors affecting soil formation
I. Parent material
• Bedrock, glacial till, eolian (wind-deposited),
fluvial (water-deposited)
II. Biotic factors
• Roots
– Increase mechanical weathering
– Reduce erosion
– Reduce leaching
– Increase organic material (affects pH)

50. Factors affecting soil formation
III. Climate
• Direct effects: temperature, winds, pptn
• Leaching = movement of solutes
• Indirect effects: via plant growth
IV. Topography
• Steep slope --> increased erosion, “soil creep”
V. Time
• From bedrock to soil: ~ 2,000-20,000 yrs

51. 2. Soil types
• Colour reflects chemical composition
– Black: high organic matter
– Yellow-brown or red: Fe oxides
– Dark purple: Mn oxides
– White / gray: CaCO3, MgCO3, quartz, gypsum

52. Soil types
• Texture reflects particle size
– Components of soil:
• Sand: 0.05 - 2.0 mm
• Silt: 0.002 - 0.05 mm
• Clay: < 0.002 mm

53. “Texture” = %, by
weight, of sand, silt
and clay
Size: 0.002 - 0.05 mm
Size: 0.05 - 2.0 mm
Size: < 0.002 mm

54. Soil texture
• Affects pore space --> air, water movement
• Coarse texture (high sand, low clay):
– Large pores
– Rapid water infiltration, drainage
• Fine texture (low sand, high clay):
– Small pores
– Poor aeration
– High surface area
– High compactability

55. Soil layers (“horizons”)

57. Moisture retention
• When all the pore spaces between soil particles are
completely filled with water, the soil is at field
capacity
• Clay soil:
– small pores --> slow drainage
– Total pore space actually > than sandy soil! (higher field
capacity)
• Capillary water = water held by capillary action
– Difficulty of extraction increases as moisture content
decreases
– wilting point: no further extraction

58. Available water capacity (AWC) = field
capacity - wilting point
• Pure sand: 30-40%
of volume = pores
• Pure clay: up to
60% of volume =
pores
– Higher field
capacity and higher
wilting point
• AWC highest in soils
of intermediate
texture (loams)

59. Ion exchange capacity = total # of charged sites on soil particles
within a volume of soil
Al3+ > H+ > Ca2+ > Mg2+ > K+ = NH4
+ > Na+
Ion exchange capacity