wastewater and soil due today
Babygirl90
soilwetness2016-2.pptSoil Wetness,
Site Instrumentation, and
Water Table Interpretations
Soil and Site. Lindbo et al. DRAFT
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This chapter and presentation should serve as an example as to how to put materials together from Chapters 1-5 in order to present a course on a specific subject. It should be noted that this presentation was developed specifically for North Carolina and may not be 100% applicable to other areas. As such it should only be taught and modified by those individuals that have a strong background in morphology of wet soils and in data interpretations of hydrographs etc.
Citation
Modified from: Lindbo, D.L., M. H. Stolt, R. Miles, and D. L. Mokma. 2005. 6. Soil Wetness and Monitoring – Power Point Presentation. in (D.L. Lindbo and N. E. Deal eds.) Model Decentralized Wastewater Practitioner Curriculum. National Decentralized Water Resources Capacity Development Project. North Carolina State University, Raleigh, NC.
Overview
- Soil chemistry and morphology
- Rules/regulations and morphology
- Soil morphology-hydrology relationships
- Need for site instrumentation
- Monitoring principles and procedures
- Data interpretation
- Field installation
Review of Soil Chemistry
and Morphology
Redox Reactions
- Redox reactions control
- Soil Color
- Organic matter contents
- Soil water chemistry
O2
NO3
Fe
SO4
Oxidation-Reduction Principles
- Electrons taken from one substance and given to another
- Electrons come from OM as it decomposes
- Oxidation = the production (loss) of electrons
- Reduction = the consumption (gain) of electrons
LEO says GER
Loss of Electrons is Oxidation
Gain of Electrons is Reduction
Respiration
O2
CO2
H2O
Aerobic soil reactions
- If air (O2) is in the soil the soil is Aerobic
4e- + O2 + 4H+ 2H2O
- If all O2 is removed soil becomes anaerobic
Anaerobic soil reactions
- Denitrification
10e- + 12H+ + 2NO3 N2 + 6H2O
- Iron (Manganese) Reduction
2e- + 6H+ + Fe2O3 2Fe(II) + 3H2O
- Sulfate Reduction
8e- + 10H+ + SO4 H2S + 4H2O
Iron Reduction
Fe2+
Fe3+
H2O
Redox Transformations
Coating of Fe2O3
Remove
Fe
Brown Soil
Fe3+
Fe2+
Gray Soil
Redoximorphic Features
Formed by changes in redox conditions in seasonally saturated soil
Reduction and oxidation of C, Fe, Mn, and S compounds
Translocation of C, Fe, Mn, and S compounds
In order to form features:
- must have anaerobic conditions (reduced and saturated)
- must have Fe and/or Mn (electron acceptor)
- must have microbes (bugs)
- must have carbon (food for the bugs)
Other factors that effect redox reactions
- Type of organic matter
- Slope and water movement
- Temperature – Biological zero
Types of organic matter
GOOD
- Fresh litter
- Dissolved organic carbon
- Root exudates
- Dead roots
- Dead organisms
POOR
- Resistant OM (i.e. peat)
- Extremely coarse OM
Aerobic or Anaerobic?
Aerobic or Anaerobic?
Temperature
- Bacterial activity decreases or stops at 5o C (40o F)
- Soils in eastern NC rarely drop below 5o C (40o F)
Effects of Reduction on Color
- Gray colors usually mean “no iron” on particle surface
- Sometimes gray colors mean there was never any iron present
- High (rust) and low (gray) colors are evidence of soil wetness (redox reactions)
- Soils with gray colors produced by reduction often have some Fe concentrations within the profile
Fe-Based Features
- Features formed by the reduction, translocation, and oxidation of Fe-oxides
- Types
- Redox concentrations (Fe masses, Fe pore linings)
- Redox depletions (Fe depletions)
- Reduced matrix
Fe depletion
Reduced matrix
Reduced matrix
Use these to assess the saturation and aeration status of the soil
- These features indicate reduction and saturation has occurred
- Influence land use decisions
Inconclusive Morphology
Inconclusive morphology
- E horizons
- Little to no Fe
- Low organic matter
- Oxyaquic conditions
E horizon with a low chroma (< 2) matrix in a well drained soil
Oxyaquic conditions on slope with sandy soils
Relict Features
Relict features
- Occur when soil colors are not in equilibrium with the soil conditions
- Colors generally take years to form
- Colors can be in error due to:
- a change in hydrology (draining or flooding)
- addition of soil material (fill)
- both can result in an estimation of higher or lower ESHW
Relict Features
- How do you know a feature is relict?
- Look at multiple profiles – especially with fill
- Site history
- Monitoring
Lithochromic Features
Gray parent material
Red color in flood plain inherited from up slope soils
Red colors from parent material hard to reduce
Drainage ditches may alter the water table and result in relict features
Soil Color and Water Table Monitoring Research
NC Separation Distance Requirements
30 cm Washed Stone
30 cm Soil Cover
Separation Distance Requirements for Other East Coast States
Virginia- 60 cm South Carolina- 15 cm New York- 60 cm
Florida- 60 cm Georgia- 60 cm Maryland- 60 cm
45 cm Group I
Treatment
30 cm Group II-IV
Treatment
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- SHWT typically occurs during winter/early spring
- On-site wastewater systems permitted year round
- Soil colors (chroma 2 or less) used as indicators of SHWT
- Well aerated soils contain oxidized iron (Fe3+) and bright yellow, orange, red colors
Seasonal High Water Table Indicators
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- Saturated, anaerobic soils with organic matter produce conditions that lead to Fe reduction/leaching and grey/white soil colors
- 14 days of continuous saturation deemed SHWT for on-site wastewater system design
- Research (He, 2003; Severson, 2008) indicated averages of 21 and 15 days of continuous saturation at chroma 2 depths
Seasonal High Water Table Indicators
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< 30 cm separation
> 30 cm separation
30 cm separation
(1) If SHWT above soil color indicators, systems will not meet separation distance requirements during SHWT; if SHWT below soil color indicators there will be more than the required separation (2)
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2
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Frequency of Inundation = 7
Cumulative Saturation = (sum of
time above chroma 2 colors)
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+30 cm?
+45 cm?
+60 cm?
Cumulative Saturation &
Frequency
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Group I Soils –8 sites
Mandarin (1) and Baymeade (2) Newport;
Fripp (2) and Newhan (3)
AB and PKS
Group II Soils - 4 sites (Goldsboro) Newport
Group III Soils- 4 sites (Altavista) Smyrna
Research Site Selections
Pine Knoll Shores
Smyrna
Newport
Atlantic Beach
Pine Knoll Shores
Smyrna
Newport
Atlantic Beach
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Soil Profile Descriptions
Well Installations
and Manual Readings
Water Level
Loggers
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Chroma 2
SHWT
Cumulative Saturation
WT Range (L-H)
WT Average
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Baymeade
WT Max (87 cm)
SHWT (116 cm)
WT Min (165 cm)
Chroma 2 (140 cm)
AVG (150 cm)
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Newhan
Chroma 2 = 0 cm
Max WT = 137 cm
SHWT = 198 cm
Avg WT = 218 cm
Min WT = > 270 cm
Chroma 2
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Goldsboro
Avg WT = 106 cm
Min WT = 173 cm
Chroma 2 = 56cm
SHWT = 73 cm
Max WT = 9 cm
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Altavista
Max WT = 2 cm
SHWT = 77 cm
Chroma 2 = 84 cm
Avg WT = 94 cm
Min WT = 135 cm
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Soil Series Summary
Excluding barrier islands, chroma 2 colors were 2 + 20 cm deeper than SHWT
USDA 45-105 122-152 >183 >183 60-90 45-75
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Continuous Saturation Duration
| Soil Series | Depth (cm) to Chroma 2 | Chroma 2 Continuous Saturation (d) | Comments | |
| Mandarin | 86 | 6 | Short continuous saturation and highest humic matter% | |
| Baymeade | 140 | 93 | ||
| Baymeade | 140 | 66 | Deepest to chroma 2 and longest continuous saturation | |
| Avg | 140 | 79 | ||
| Goldsboro | 58 | 2 | ||
| Goldsboro | 56 | 17 | Shallowest to Chroma 2 and shortest continuous saturation | |
| Goldsboro | 56 | 1 | ||
| Goldsboro | 58 | 4 | ||
| Avg | 57 | 6 | ||
| Altavista | 91 | 49 | ||
| Altavista | 79 | 51 | Intermediate depth to chroma 2 and continuous saturation | |
| Altavista | 84 | 18 | ||
| Altavista | 89 | 10 | ||
| Avg | 86 | 32 | ||
| Overall Avg | 29 | |||
| Average sites < 1m to chroma 2 | Less time to produce chroma 2 colors in shallower soils | |||
| 18 |
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Frequency of Saturation at Chroma 2 Depth
and 30-60 cm Above
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Cumulative Saturation of Chroma 2 Depth and
30-60 cm Above
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Mandarin Baymeade
Goldsboro Altavista
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Morehead City, NC Long Term Precipitation
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Conclusions
- Soil colors not effective predictors of SHWT on barrier island soil series: Newhan and Fripp
- Chroma 2 and SHWT within 22 cm for 8 of 11 non-barrier island sites
- 6 of 11 sites SHWT shallower than chroma 2 by avg of 18 cm
- Almost order of magnitude difference in cumulative saturation for each 15 cm above chroma 2 colors; frequency of saturation also decreases
- 15+ cm increase in required separation from chroma 2 colors would reduce frequency of saturation and cumulative saturation of OSWS drainfield trenches
- More research needed with different soil series and longer term experiments
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Seasonal High Water Table Monitoring Methods
1) Direct monitoring- monitor daily water levels and rainfall from December to April (wet season) if rainfall is sufficient, can use 14-d high as depth to SHWT
2) Monitoring and modeling- if rainfall is less than normal, can use water level responses to rainfall, soil data to calibrate DRAINMOD to predict SHWT
- Use 40 year rainfall data to compute hydrographs
- Compute annual saturation (frequency and duration) parameters
Why is there a need for site instrumentation and monitoring?
- Inconclusive morphology
- Relict features
- Lithochromic colors
Lithochromic Features
- Colors or structures inherited from the parent material
- Flood plains-can be grayer or redder than actual site conditions would suggest
- Saprolite-rock controlled structure vs soil structure
Low chroma colors from minerals in parent material not reduction
Wells and Piezometers
Measurement Methods
- Water level meters (dippers)
- Chalked Tape
- Recording
- Electronic
- Pressure transducers
Dye for measuring redox
- Alpha – Alpha’ – Dipyridyl (AADP)
- Normally colorless
- Turns pink if reduced Fe (Fe2+) is present
Soil and Site. Lindbo et al. DRAFT
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Positive reaction to AADP
