Environmental Study Group

November 30, 2004

Soil Characterization & Sampling for Effective

Surface Reclamation of Saltwater-Impaired Soils

Soil Characterization & Sampling for Effective

Surface Reclamation of Saltwater-Impaired Soils

Gilbert J. Van Deventer, PG, NMCS, REM

gil@trident-environmental.com

Trident Environmental, PO Box 7624, Midland TX 79708

Office: 432-682-0808

Fax: 432-682-0727

Mobile: 432-638-3106

Website Address: www.trident-environmental.com

Sources of information:

Remediation of Salt-Affected Soils at Oil and Gas Production Facilities, API Publication No. 4663, Oct. 1997

The Nature and Properties of Soils, by Nyle C. Brady, 1990, 10th Edition, McMillan Publishing Co.

Seeding Rangeland, by Tommy C. Welch, et al, April 1994, Texas Agricultural Experiment Station

Soil Characterization

Sampling for Effective Surface Reclamation of Saltwater-Impaired Soils

•Onsite Assessment and Sampling

•Physical Components

•Important Soil Properties

•Soil Horizons

•Slope and Erosion Susceptibility

•Drainage

•Soil Chemistry

•Water

•Climate

Very important to characterize the soil because we need to know the health,

maturity, properties of the soil, and other site conditions if we are to be able to

improve or restore the surface.

Soil Characterization

Soil has four physical components.

A typical soil consists of approximately

Physical Components

45%25%25%5% Organic Mat t er

Inorganic SolidsWat erAir

Therefore, about 50% of a soil is pore space is occupied by either water or air.

Important Soil Properties

Texture - relates to the size of individual soil particles (gravel, sand, silt, clay) and how they

are apportioned.

loam - mixture of sand, silt and clay

–clay soils (low permeability);–sandy soils (high permeability);–loams have good drainage–Hard horizon may result in perched water conditions

Soil Texture Triangle

Important Soil Properties

Color -- depends on

• organic content -- makes soil dark

• Fe-oxide content -- makes soil red

• Greenish, dark gray, bluish colors or mottles (splotches of light color in dark soil) indicate prolonged wetness.

• Al-oxides, CaCO3 -- light colors

Structure -- shape of aggregates in soil; may influence

direction of percolation through soil

• Soil particles bound in stable aggregates are resistant to erosion and indicative of relatively large and beneficial macropores in the soil. These macropores help the soil efficiently take in rainwater and air which are essential to the survival of most plants and animals.

Soil Horizons

Soil Profile and Horizons

O horizon -- abundant organic matter (OM); dark colored. OM >50% by weight.

A horizon -- considered “topsoil” or primary root zone. Has the greatest biological activity and richest in plant nutrients. Internal biotic activities, including plant growth, help bind soil particles together into stable structural units called aggregates. Region from which materials (esp. calcite, iron oxide, clays) are removed (eluviation); lighter color than O, but still contains OM.

B horizon -- subsoil material moved from A horizon may accumulate here (illuviation); color depends on presence of iron oxide, calcite, or clay (any of these may be abundant); lighter color than A. Little OM, fewer plant roots, and much less biological activity than topsoil. Usually has the highest proportion of clay which greatly restricts downward migration of water.C horizon -- partially altered parent material, but looks similar to parent material. Contains esentially no OM or illuviation of clay material from above. Has been subjected to chemical weathering by water percolating through the soil. Soil salts, carbonates, and reprecipitated silicates often concentrate and become cemented, further decreasing porosity.

R horizon -- (regolith) consolidated geologic bedrock material such as sandstone or limestone. Not considered to have been sufficiently weathered to be described as part of the soil.

Eluviation - or washing out of carbonates from A horizon to B horizon

Illuviation or washing in of material and calcification (CaCO3)

from A and C horizon to B horizon

Decalcification - removal of calcium from C horizon to B horizon by chemical transformation

OA1

A2

A3

B1

B2

C

Example of translocation

(movement of materials within the soil profile)

The 12 soil orders (soil types) are listed below in thesequence in which they key out in Soil Taxonomy

Gelisols - soils with permafrost within 2 m of the surface

Histosols - organic soils

Spodosols - acid forest soils with a subsurface accumulation of metal-humus complexes

Andisols - soils formed in volcanic ash

Oxisols - intensely weathered soils of tropical and subtropical environments

Vertisols - clayey soils with high shrink/swell capacity

Aridisols - CaCO3-containing soils of arid environments with subsurface horizon development

Ultisols - strongly leached soils with a subsurface zone of clay

accumulation and <35% base saturation

Mollisols - grassland soils with high base status

Alfisols - moderately leached soils with a subsurface zone of clay accumulation and >35% base saturation

Inceptisols - soils with weakly developed subsurface horizons

Entisols - soils with little or no morphological development

Characteristics of Aridisols

•Of the twelve soil orders for soil types, Aridisols are probably the most common in west Texas and southeast New Mexico.

•They are characterized as dry soils generally light in color and low in organic matter.

•They have a horizon of accumulation of calcium carbonate (calcic), gypsum (gypsic), soluble salts (salic), or sodium (sodic).

•Except where there is groundwater or irrigation, the soil layers are moist only for short periods of the year.

•These short moist periods may be sufficient for drought-adapted desert shrubs and annual plants, but much less so for many varieties of perennial grasses or conventional crops.

•If groundwater is present near the surface, soluble salts often accumulate to levels that most crop plants cannot tolerate.

• The major land use for Aridisols are for rangeland. They are not generally suitable for cropland as they have a naturally low fertility.

•Where irrigation water is available, Aridisols can be highly productive however,they must be carefully managed to prevent the accumulation of soluble salts.

Aridisols are further broken down into suborders below:

Map of Aridisols in the United States

Aridisols have a limited availability of soil moisture for sustained plant growth. The redistribution and accumulation of soluble

materials in some layers of the soils are common.

Calcid Aridisol with a calcic horizon. The parent materials have a high carbonate (caliche) content.

Slope and Erosion Susceptibility

Erosion is problematic where sloping occurs and potentially severe with slopes > 8% because it results in loss of topsoil

Erosion and Slope Controls

•Rapid establishment of vegetation

•Berming

•Terracing

•Prevention of runon and runoff

•Leveling

•Erosion-control fabrics

•Mulching

•Contour tillage

•Hydromulching

•Biodegradable nets

Drainage

The ability of a soil to drain is very important especially because salts must be able to move out of the soil root zone in order to remediate the soil.

Soil internal drainage is affected by soil texture, pore size distribution, and low permeability layers.

Drainage categories as created by the USDA-NRCS are described as:

•Excessively Drained - Water drains so rapidly that the soil retains relatively little water and plants are frequently in drought stress.

•Well Drained - Water drains readily but not rapidly allowing for sufficient water to be available for mesophytic plants (plants which require a moderate amount of water) during most of the growing season.

•Moderately Drained - Water is removed somewhat slowly during some periods of the year. Growth of mesophytic plants is limited.

•Poorly Drained - Water is removed very slowly and soil is usually wet. Without drainage enhancements, excessive wetness is growth limiting to mesophytic plants. One or more of the following factors: substantial rainfall, minimal slope or depression area, high water table, fine soil texture or low permeability layer, or minimal macropores.

Soil Chemistry

Name Symbol Nutrient Form Ion Name

Non-Minerals (from air and water)Carbon C - - -Hydrogen H - - -Oxygen O - - -

Primary Macronutrients (needed in large amounts)Nitrogen N NO3- , NH4+ Nitrate, ammoniumPhosphorus P HPO4- 2, H2PO4- , OrthophosphatesPotassium K K+ - - -

Secondary Macronutrients (needed in small amounts)Calcium Ca Ca+2 - - -Magnesium Mg Mg+2 - - -Sulfer S SO4- 2 Sulfate

Micronutrients (needed in very small amounts)Boron B H3BO3, B(OH)4, Boric acid, hydrated borateCopper Cu Cu+2 - - -Chlorine Cl Cl- ChlorideIron Fe Fe+2, Fe+3 Ferrous, ferricManganese Mn Mn+2 ManganousMolybdenum Mo MoO4- 2 MolybdateZinc Zn Zn+2 - - -

Plant Nutrients

The soil solution (liquid phase of a soil) dissolves and allows other plant nutrients to move toward plant roots. In order for a plant to survive it must have an appropriate amount of each of the plant nutrients as listed below.

Soil Chemistry

Sources of Nutrients in the Soil

Organic matter Most soil nutrients are contained in the soil organic matter. To make these nutrients available the organic matter must be decomposed..

Adsorbed nutrients These are the nutrients that are held on the soil colloid. This is the major source of nutrients for the plants, and is the source that is most easily controlled by man.

Soil minerals (includes clay minerals) These are the nutrients that are in the parent materials. These nutrients may become available through weathering, however this is a very slow process.

Soil Chemistry

The salts in saline soils are primarily chloride (Cl-) and sulfate (SO4

-2) anions that pair with calcium (Ca+), magnesium (Mg+2), sodium (Na+), and potassium (K+) cations.

Once deposited or released in the soil whether by by natural or man-made means, the salts are brought to or near the surface through micropores by upward-moving water, which then evaporates, leaving the salts behind.

Unfortunately, high levels of these salts cannot be tolerated by most crop plants.

Detrimental effects on plants stem not only from the high salt contents but also from the level of sodium in the soil, especially in relation to levels of calcium and magnesium.

High exchangeable sodium levels are detrimental both physically and chemically.

Because of the situations outlined above four primary chemical properties should be measured to characterize salt-affected soils:

1: pH2: Electrical Conductivity (EC)3: Exchangeable Sodium Percentage (ESP)4: Sodium Absorption Ratio (SAR)

Chemical Properties

pH - is a measure of the degree of soil acidity

(H+ dominant) and alkalinity (OH- dominant).

The soil pH controls many chemical and biological functions of soils and plants, especially in relation to nutrient availability for plant growth.

4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 ACID ALKALINE

Nitrogen . . Phosphorus . . Potassium . . Sulphur . . Calcium . . Magn esium . . I ron . . Manganese . . Bor on . . Copper Zinc . . Molyb denum

In the above diagram the denser the band shade, the greater the availability for that particular plant nutrient, as the shading diminishes nutrient availability decreases.

Chemical Properties

Electrical Conductivity (EC) - measures the ability of the salt in the soil solution to conduct electricity which correlates indirectly to the concentration of salt in soil. Units are commonly expressed in decisiemens per meter (dS/m).

Traditionally, the pH and EC measurements are made in a suspension of soil in water (usually a ratio of 1:1 or 1:2). Although this method is suitable for quick screening in the field, for saline soils it is better to determine pH and EC on a saturated paste of the soil because the moisture content of the paste is sufficiently near that of the soil to make the measured pH more meaningful.

Normal (non-saline and non-sodic) soils typically have a pH ranging from 6.5-7.2 pH units and an EC value of 2-6 dS/m.

Chemical Properties

Exchangeable Sodium Percentage (ESP) - identifies the degree to which the exchange complex is saturated with sodium.

Exchangeable sodium - amount of sodium on cation exchange sites or in the soil solution that can participate in the cation exchange process in soil.

Cation exchange capacity (CEC) - The number of cation positive charges retained by 100 grams of soil. The CEC is a measurement of the total amount of exchangeable cations that can be held by the soil. Soil clays and organic matter have a relatively large number of negative charge sites which retain cations in dynamic equilibrium with the soil solution. CEC gives an indication of the soils potential to hold plant nutrients.

exchangeable sodium (meq/100 gm soil)cation exchange capacity (meq/100 gm soil)

ESP =

Normal soils typically have an ESP between 13-15

Chemical Properties

Sodium Adsorption Ratio (SAR) - is a measure of the relative competitiveness of sodium versus calcium plus magnesium for adsorption onto clay cation exchange sites. It is calculated as follows:

[Na]

[Ca] + [Mg]2

SAR =

Normal soils typically have a SAR between 13-15

One problem with the overdependence on using SAR is that it is merely a ratio of dissolved cations, and is completely unrelated to the total amount of sodium in the soil or the CEC of the soil. This is important because we want to know the total amount of sodium in the soil when calculating the quantity of chemical amendments required to remediate the soil. For this reason, ESP is the preferred over SAR in order to calculate required chemical amendments.

ESP ~ SAR when either are <40 (soil at equilibrium)

Chemical Properties

Saline Soils and Osmotic Potential

Soil Dispersion - is the reverse process of aggregation. Dispersion is a detrimental electrochemical process in which soil clay particles repel each other, that is physically move apart, and clog soil pores. Unless soil salinity is also high dispersion will occur in soils having excess sodium.

Osmotic Potential - The force which causes dissolved constituents to retain water molecules. Highly saline soil water competes with the plants for water molecules because of the high osmotic potential it creates.

Sodic Soils and Soil Dispersion

Soil Propert ies

Common pH

Elect rical Conduct iv it y

(EC) (dS/ m)

Sodium Adsorpt ion

Rat io

(SAR) a

Soil and Plant Response

Normal 6.5- 7.2 <4 <13- 15 Well aggregat ed, good nut rient availabilit yAc id <6.5 <4 <13- 15 Well aggregat ed, nut rient availabilit y inhibit edSaline <8.5 >4 <13- 15 Osmot ic st ress, well aggregat edSaline- Sodic <8.5 >4 >13- 15 Osmot ic st ress, pot ent ial dispersion af t er rainSodic >8.5 <4 >13- 15 No osmot ic st ress, disperseda Exchangeable sodium percentage (ESP) and sodium adsorption ratio (SAR) are closely related in m ost soils

Soil Propert ies

Climate

To a great extent, climate determines the type of soil present as it dictates the frequency, duration, and quantity of precipitation and evaporation, as well as the extremes and duration of temperature and wind.

After a rainfall, a portion of the rainwater percolates downward through the soil dissolving and carrying soluble salts. During evaporative periods, soil-pore water reverses course and moves back upward through the soil bringing dissolved salts back to the surface. Since salts do not evaporate, they continue to concentrate at the soil surface during evaporation of soil water.

These factors have a major impact on the fate and transport of salts in the soil. Most chemical reactions occur at a faster rate with increasing temperature.

WaterWater is critical to plant growth because it provides the transportation medium in which nutrients are delivered to plants. As stated earlier, a typical soil contains about 25% water in its pore spaces. The pore spaces can be full of water, but rarely contain less than 10% water, even when very dry.

Mean Annual Total Precipitation in Texas

Salt and Drought Tolerance of Native Grass Plants Common to west Texas

Source: Seeding Rangeland, Tommy Welch, et al, April 1994, Texas Agricultural Experiment Station

The traditionally accepted objective criteria for remediation of saline and/or sodic soils for all plants has been to decrease the salinity and ESP to <4 dS/m and 15, respectively. However, the presence of naturally saline and sodic environments and the halophytic plants which thrive naturally in these soils indicates that more elevated levels of salts can be an acceptable remediation goal.

Common Name (Nat ive Grasses)

Salt Tolerance

Drought Tolerance

Alkali Sacat on Good FairBig Bluest em Fair FairBlue Gramma Fair GoodBuf falograss Fair GoodCalifornia Cot t ont op Fair FairFourw ing Salt brush Good FairLehmann Lovegrass Fair GoodPlains Brist legrass Fair GoodSalt grass Good GoodSideoat s Gramma Fair Fair

Law of the Minimum

Stave Concept

Whether a primary or secondary macronutrient or, a micronutrient, the Law of the Minimum holds: the most growth-limiting nutrient will limit growth, no matter how favorable the nutrient supply of other elements.

For example, a deficiency of Fe or Mn (most common in soils containing calcium carbonate) can severely limit plant growth in spite of adequate N, P, and K.

This concept also applies to other requirements for active plant growth.

Assessment and Sampling Activities

• Compile pertinent information

concerning release

• Draw site map that includes

pertinent features, structures, and

affected area

• Collect Soil Samples

• Test and observe soil sample

characteristics

Assessment and Sampling Activities

Compile pertinent information concerning release

Site identification (Lease No.) and legal location (section, township, range,latitude, longitude, etc.)

- Land use (agricultural, grazing, industrial, etc.)

- Date of Release (if known)

Amount of release (if known)

Cause of release (if known)

Assessment and Sampling Activities

Draw site map that includes pertinent features, structures, and affected area__

Features: roads, fence line, surface water bodies, property lines, etc.

Structures: tank batteries, pipelines, etc.

Horizontal and vertical extent of the salt-affected area

- Topography, drainage, and slope characteristics

- Native vegetation types (and crops if applicable)

- Sample locations and field measured values (pH, EC, chloride, soil type, etc)

Source: Remediation of Salt-Affected Soils at Oil and Gas Production Facilities, API Publication No. 4663, Oct. 1997

Useful Forms

Assessment and Sampling Activities

Collect Soil Samples for bothField Measurements and Lab Analysis

Hot spot composites (0-1 ft and 1-2 ft) (Deeper samples may be required)

Avg condition composite (0-1 ft and 1-2 ft)

Background (0-1 ft and 1-2 ft)

$$ PRICELESS $$

Assessment and Sampling Activities

Test and observe soil sample characteristics

Determine depth of saltwater penetration

Identify soil horizons and note thickness (particularly topsoil and A horizon.

Identify soil texture, color, structure and quantify sand, silt, clay content

- Measure pH, EC, and chloride concentration in the field from samples comprised of a suspension of soil in water (usually a ratio of 1:1 or 1:2). These quick “screening” measurements will be useful in choosing which and how many samples will be submitted for laboratory analysis.

- Submit samples for laboratory analysis of CEC, SAR, ESP, OM, cations(Ca, Mg, Na, K, S) and anions (SO4, Cl), moisture content, pH, and EC.

Sample No. (E)

Horizon Desig.

(H)

Sample Dept h

(E)pH (E)

EC (dS/ m)

(E)

Chloride (mg/ L)

(H)

TPH (ppm)

( I )

Text ure Class (E)

Topsoil Thickness

( in) (E)

Imperm. Layer (Y/ N)

(E)

Perm. Class (E)

Degree of

Wet ness (E)

1a A 0'- 1' 7.5 16 750 - - - sand 1.0 N rapid dry1b B 1'- 2' 8.0 24 1200 - - - sand 1.0 N m oderate moist2a A 0'- 1' 8.5 32 1500 - - - sandy CL 1.0 N m oderate moist2b B 1'- 2' 8.5 44 2100 - - - sandy CL 1.0 N slow saturated

2c B 4'5' 8 16 250 - - - sandy CL 1.0 N v slow saturated

SAMPLE LOCATIONS AND FIELD DATA

Sit e Name (C) :Locat ion (C) :Spill ID No. (C) :

GW Bush # 1Sec 1 T19S, R40E

Dat e (E) :Technic ian (E) : GJV

11/ 30/ 04

N/ A

FIELD INFORMATION TO BE COLLECTED WHILE SAMPLING

(C) = Convenient informat ion

Notes:(E) = Essent ial informat ion( I ) = Import ant informat ion(H) = Helpful informat ion

The moisture content (weight of soil moisture divided by dry weight of soil) at which pH, EC, SAR, ESP values are measured is very important because the ratio of less soluble salts (Ca and Mg) to more soluble salts (Na) increases with increasing moisture content.

The saturated percentage represents the maximum moisture content at which dissolved nutrients are available to plants. The saturated percentage is achieved when all soil pores are completely filled with water, but there is no water in excess of that amount. For this reason the method of preparing a saturated paste is recommended to allow measurements of pH, EC, SAR, ESP, and soluble ions.

Fortunately, if this is too time consuming and burdensome to do in the field it may be more convenient to have an experienced laboratory do this work for you since they will be performing the analyses anyway.

Preparing a saturated paste extract requires allowing the water to equilibrate with the soil for at least an hour and extraction by inducing a vacuum or positive pressure.

Saturated Paste Extract

Soil Testing Laboratories

Texas Plant & Soil Lab, Inc. 5115 W. Monte CristoEdinburg, TX 78539

956-383-0739http://www.txplant-soillab.com

Texas A&M University Soil, Water and Forage Testing Laboratory

345 Heep CenterCollege Station, TX 77843-2474

979-845-4816http://soiltesting.tamu.edu/

Texas A&M University Soil & Crop Sciences Department

College Station, TX 77843-2474979-845-7295

http://soildata.tamu.edu/

Source: Remediation of Salt-Affected Soils at Oil and Gas Production Facilities, API Publication No. 4663, Oct. 1997

Source: Remediation of Salt-Affected Soils at Oil and Gas Production Facilities, API Publication No. 4663, Oct. 1997

Source: Remediation of Salt-Affected Soils at Oil and Gas Production Facilities, API Publication No. 4663, Oct. 1997

THE END

Cow manure showing proper fiber and

moisture content indicating balanced feed.

QUESTIONS?