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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)
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
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
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
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
0
2000
4000
6000
8000
10000
0 2000 4000 6000 8000 10000
Soxtec
Soxh
let
F3 (C16 to C34)
y = 0.912x + 29.802R2 = 0.9859
0
2000
4000
6000
8000
10000
12000
0 2000 4000 6000 8000 10000 12000 14000
Soxtec
Soxh
let
F4 (C34-C50)
y = 0.9406x + 13.035R2 = 0.9333
0
500
1000
1500
2000
2500
3000
3500
0 500 1000 1500 2000 2500 3000 3500 4000
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!