Comparison of Various Extraction Methods for Petroleum ... · % Recovery SoxhletSoxtec Shake Tumble...

Comparison of Various Extraction Methods for

Petroleum Hydrocarbons (PHC) in Soils and in

Drilling Waste

John Ashworth1 & Ron Minks2

1. Director, Soil Science; ETL

2. Director of Calgary Operations; ETL

• Alberta’s drilling waste disposal guidelines (G-50, 1996) are currently being revised

• After drilling waste disposal, parameters must fall within scientifically determined, risk-based “end-point” soil quality values

• The end-points for petroleum hydrocarbons (PHCs) are geared to the Canada-Wide Standard Method of soil analysis (CCME)

Upstream Petroleum Guidelines (Hydrocarbons)CCME method. Fine, surface, agricultural soil

Fraction 1 0.026 % 260 mg/kgC6-C10

Fraction 2 0.09 % 900 mg/kgC10-C16

Fraction 3 0.08 % 800 mg/kgC16-C34

Fraction 4 0.40 % 4,000 mg/kgC34-C50

Treatability Test #2 (Fertilized) - Results to Feb. 2003

0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

0 2 4 6 8 10 12

Months

Co

nce

ntr

atio

n (

mg

/kg

)

PHC F2 (mg/kg)

PHC F3 (mg/kg)

PHC F4 (mg/kg)

Soils Used in the CCME Validation Study

Soil % sand % clay % moisture texture organic matterA 42 32 0 clay loam 1 %B 91 5 0 sand 2 % approx.C 34 25 0 loam 12 % approx.D1 38 31 0 clay loam 9 %D2 38 31 20 clay loam 9 %

Two Extraction Studies

• CCME CWS PHC extraction of soilsü5 methodsü5 soil typesü7 spikes eachü= a lot of data!

Two Extraction Studies

• Drilling waste comparison using CCME benchmark extraction vs cold shake extractionüUse shake method to pre-determine

hydrocarbon loading for G-50 purposes

Soil Extraction Techniques:

Ø SoxhletØ SoxtecØ Cold shakeØ TumblerØ Sonic bath

Soxhlet Soxhlet -- EPA 3540EPA 3540• CCME PHC benchmark • Named after Franz Soxhlet

(1848 - 1913), a German food analyst

• Series of distillations/cycles• Total extraction time: 16-24

hours

SoxtecSoxtec -- EPA 3541EPA 3541• Rapid extraction by

Soxtec is the 21st century, automated version of Soxhlet extraction

• Total extraction time: 1-2 hours

Cold ShakeCold Shake

• Wrist-action shaker• Total extraction time: 1 hour

TumblerTumbler• TCLP-type

extraction (EPA 1331) using solvent

• End-over-end rotation/tumble

• Total extraction time: 2 hours

Sonic Bath Sonic Bath -- EPA 3550EPA 3550

• Extract with ultrasonic waves in a water bath

• Total extraction time: 10 minutes

GC/FID SystemGC/FID System• Carrier gas flows into the

injector, through the column and then into the detector

• Sample extract is injected into the heated injection port and vaporized

• Hydrocarbons are separated through a column based upon boiling points

• Each compound is detected by the FID

Comparison to Benchmark

• Soxhlet defined as benchmark extraction for CCME PHCs

• Each soil type spiked with diesel and SAE 30 motor oil - 7 replicates

• Recoveries measured are relative to Soxhlet

F2 (C10-C16)

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40

60

80

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140

Clay Loam,9%OM

Clay Loam,9% OM 20% H2O

Clay Loam, < 2 %OM

Sand Loam

% R

eco

very

SoxhletSoxtecShakeTumbleSonic bath

F3 (C16-C34)

0

20

40

60

80

100

120

140

Clay Loam,9%OM

Clay Loam, 9%OM 20% H2O

Clay Loam, < 2 %OM

Sand Loam

% R

eco

very Soxhlet

SoxtecShakeTumbleSonic bath

F4 (C34-C50)

0

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40

60

80

100

120

140

Clay Loam,9%OM

Clay Loam, 9%OM

20% H2O

Clay Loam, < 2 %OM

Sand Loam

% R

eco

very Soxhlet

SoxtecShakeTumbleSonic bath

Recovery Summary -Compared to Soxhlet Recovery

• Soxtec within 10%• Cold shake method recovery ranges from

42%-111%• Tumble method recovery ranges from

66%-107%• Sonic bath method recovery ranges from

56%-100%• No data available for ASE or microwave

Bio-availability(aging; sequestration)

• Effect of organic matter (a form of partitioning)

• Effect of texture, especially sorption on clays

• Other suggested factors: encapsulation in precipitates; pH; temperature

Comparison Using Real-World Samples

• Random sample selection (approx. 200)• Extract duplicate sample using Soxhlet

and Soxtec• Regression of data onto chart (Lloyd

Hodgins)

F2 (C10 to C16)

y = 1.0015x + 53.204R 2 = 0.907

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Soxtec

Soxh

let

F3 (C16 to C34)

y = 0.912x + 29.802R2 = 0.9859

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Soxtec

Soxh

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F4 (C34-C50)

y = 0.9406x + 13.035R2 = 0.9333

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3500

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Soxtec

Soxh

let

We also analyzed two drilling wastes for total extractable hydrocarbons (TEH) using the cold shake method

and compared recoveries to the CCME benchmark method

Drilling Waste % Moisture“DWA” 28%“DWB” 58%

Diesel spike ranged from 2,000 – 4,000 mg/kg

% TEH Recovery

0%

20%

40%

60%

80%

100%

120%

140%

CCME PHC Cold shake w/hexane/acetone

Cold shake w/ hexane

% R

ecov

ery

DW-A

DW-B

Summary - Soils

• Soxtec is equivalent to CCME benchmark Soxhlet method

• Other alternative methods have various challenges to meet equivalency

• Bioavailability of PHCs in soil an issue for recovery

• Ensure ongoing equivalency using PT samples (CAEAL) and real-world samples

Summary - Drilling Wastes

• Cold shake extraction works well for drilling wastes compared to CCME benchmark soxhlet method

• Hexane alone works well• Drilling wastes do not display the

bioavailabiltiy issues found in soils• Receiving soils will require CCME PHC

method

Thank you!