Effectiveness of microbe application to petroleum spills at crash sites

              Effectiveness of Microbe
Application to Petroleum Spills
at Crash Sites
Final Report 600
March 2012
Arizona Department of Transportation
Research Center
Effectiveness of Microbe Application
to Petroleum Spills at Crash Sites
Final Report 600
March 2012
Prepared by:
N. Weiss Associates, Inc.
P.O. Box 71790
Phoenix, AZ 85050
and
Arizona State University
College of Technology and Innovation
Environmental Technology Management
Mesa, AZ 85212
Prepared for:
Arizona Department of Transportation
In cooperation with
U.S. Department of Transportation
Federal Highway Administration
The contents of this report reflect the views of the authors who are responsible for the
facts and the accuracy of the data presented herein. The contents do not necessarily
reflect the official views or policies of the Arizona Department of Transportation or the
Federal Highway Administration. This report does not constitute a standard,
specification, or regulation. Trade or manufacturers’ names that may appear herein are
cited only because they are considered essential to the objectives of the report. The US
government and the State of Arizona do not endorse products or manufacturers.
TECHNICAL REPORT DOCUMENTATION PAGE
1. Report No.
FHWA-AZ-12-600
2. Government Accession No.
3. Recipient's Catalog No.
5. Report Date
March 2012
4. Title and Subtitle
Effectiveness of Microbe Application to Petroleum Spills at
Crash Sites
6. Performing Organization Code
7. Author
Norm Weiss, Dr. Larry Olson, Dr. Kiril Hristovski, Sabina
Podversich, Al Brown,
8. Performing Organization Report No.
10. Work Unit No.
9. Performing Organization Name and Address
N. Weiss Associates, Inc. - and - Arizona State University
P.O. Box 71790 College of Technology and Innovation
Phoenix, AZ 85050 Environmental Technology Management
Mesa, AZ 85212
11. Contract or Grant No.
SPR-PL 1 (67/175) 600
13. Type of Report & Period Covered
Final Report
12. Sponsoring Agency Name and Address
Arizona Department of Transportation
206 S. 17th Avenue
Phoenix, AZ 85007
ADOT Project Manager: Dr. Estomih Kombe
14. Sponsoring Agency Code
15. Supplementary Notes
Prepared in cooperation with the U.S. Department of Transportation, Federal Highway Administration
16. Abstract
Each year vehicular accidents cause gasoline and diesel spills on Arizona roadways. ADOT currently uses
Micro-Blaze®, a commercially available microbial solution, as a supplement to natural degradation of vehicular
petroleum spills in soils. With an emphasis on minimizing or eliminating environmental and public health
hazard, ADOT is interested in determining cost-effective methods to address spills involving petroleum products
from roadway vehicular accidents. This study investigated whether Micro-Blaze, Hydro Clean®, Miracle-Gro®,
or water accelerated the degradation process significantly over natural processes and that it will help to
determine their effectiveness in accelerating the remediation of petroleum products (diesel No. 2 and unleaded
gasoline) on predominant Arizona soil types from roadway vehicular accidents. The soil types evaluated were
aridisols from Burro Creek, alfisols from Show Low, and entisols from Mesa. All three soil types contaminated
with gasoline showed a reduction in BTEX levels to below ADEQ’s SRLs within 21 days, even in the absence of
added microorganisms or nutrients. In none of the sample treatments was the diesel (total petroleum
hydrocarbon) concentration below either residential or non-residential SRLs by day 83. The results are discussed
referencing ADEQ’s SRL in effect for 2006; ADEQ changed SRLs in 2007. When compared to the new 2007
levels, BTEX are below SRL and there is no longer an ADEQ SRL for total petroleum hydrocarbon.
17. Key Words
Petroleum, Remediation, Bioremediation,
Microbial, Vehicular Crash Site
18. Distribution Statement
Document is available to the U.S.
public through the National
Technical Information Service,
Springfield, Virginia, 22161
19. Security Classification
Unclassified
20. Security Classification
Unclassified
21. No. of Pages
59
22. Price
23. Registrant's Seal
SI* (MODERN METRIC) CONVERSION FACTORS
APPROXIMATE CONVERSIONS TO SI UNITS
Symbol When You Know Multiply By To Find Symbol
LENGTH
in inches 25.4 millimeters mm
ft feet 0.305 meters m
yd yards 0.914 meters m
mi miles 1.61 kilometers km
AREA
in2 square inches 645.2 square millimeters mm2
ft2 square feet 0.093 square meters m2
yd2 square yard 0.836 square meters m2
ac acres 0.405 hectares ha
mi2 square miles 2.59 square kilometers km2
VOLUME
fl oz fluid ounces 29.57 milliliters mL
gal gallons 3.785 liters L
ft3 cubic feet 0.028 cubic meters m3
yd3 cubic yards 0.765 cubic meters m3
NOTE: volumes greater than 1000 L shall be shown in m3
MASS
oz ounces 28.35 grams g
lb pounds 0.454 kilograms kg
T short tons (2000 lb) 0.907 megagrams (or "metric ton") Mg (or "t")
TEMPERATURE (exact degrees)
oF Fahrenheit 5 (F-32)/9 Celsius oC
or (F-32)/1.8
ILLUMINATION
fc foot-candles 10.76 lux lx
fl foot-Lamberts 3.426 candela/m2 cd/m2
FORCE and PRESSURE or STRESS
lbf poundforce 4.45 newtons N
lbf/in2 poundforce per square inch 6.89 kilopascals kPa
APPROXIMATE CONVERSIONS FROM SI UNITS
Symbol When You Know Multiply By To Find Symbol
LENGTH
mm millimeters 0.039 inches in
m meters 3.28 feet ft
m meters 1.09 yards yd
km kilometers 0.621 miles mi
AREA
mm2 square millimeters 0.0016 square inches in2
m2 square meters 10.764 square feet ft2
m2 square meters 1.195 square yards yd2
ha hectares 2.47 acres ac
km2 square kilometers 0.386 square miles mi2
VOLUME
mL milliliters 0.034 fluid ounces fl oz
L liters 0.264 gallons gal
m3 cubic meters 35.314 cubic feet ft3
m3 cubic meters 1.307 cubic yards yd3
MASS
g grams 0.035 ounces oz
kg kilograms 2.202 pounds lb
Mg (or "t") megagrams (or "metric ton") 1.103 short tons (2000 lb) T
TEMPERATURE (exact degrees)
oC Celsius 1.8C+32 Fahrenheit oF
ILLUMINATION
lx lux 0.0929 foot-candles fc
cd/m2 candela/m2 0.2919 foot-Lamberts fl
FORCE and PRESSURE or STRESS
N newtons 0.225 poundforce lbf
kPa kilopascals 0.145 poundforce per square inch lbf/in2
*SI is the symbol for th International System of Units. Appropriate rounding should be made to e comply with Section 4 of ASTM E380.
(Revised March 2003)
METRIC CONVERSION FACTORS PAGE (FURNISHED BY ATRC)
TABLE OF CONTENTS
EXECUTIVE SUMMARY.......................................................................................................1
1.0 INTRODUCTION..........................................................................................................5
2.0 BACKGROUND............................................................................................................7
3.0 METHODOLOGY.........................................................................................................9
3.1 SOILS PREPARATION ............................................................................................9
3.2 PREPARATION OF SAMPLES .............................................................................10
Soil Sample Procedures for Soil-Gasoline-Water Blanks ...............................................11
Soil Sample Procedures for Soil-Diesel-Water Blanks ...................................................11
Soil Sample Procedures for Soil-Treatment Product Blanks ..........................................11
Soil Sample Procedures for Soil-Gasoline-Treatment Product Blanks...........................11
Soil Sample Procedures for Soil-Diesel-Treatment Product Blanks...............................11
3.3 EXTRACTION AND ANALYSIS ..........................................................................13
Diesel Extraction .............................................................................................................13
Diesel Analysis................................................................................................................14
Quality Assurance and Quality Control ..........................................................................15
Gasoline Extraction .........................................................................................................16
Gasoline Analysis............................................................................................................16
Quality Assurance and Quality Control ..........................................................................18
3.4 RANKING METHODOLOGY................................................................................18
Gasoline Ranking Methodology......................................................................................19
Diesel Ranking Methodology..........................................................................................19
4.0 RESULTS ....................................................................................................................21
4.1 PHYSICAL PROPERTIES OF THE SOILS USED IN THE PROJECT................21
4.2 QUALITATIVE ANALYSIS ..................................................................................21
Gasoline..........................................................................................................................21
Diesel..............................................................................................................................22
4.3 QUANTITATIVE ANALYSIS................................................................................23
Gasoline Calibration Curves ...........................................................................................23
Diesel Calibration Curve .................................................................................................26
4.4 ANALYSIS OF SOIL AND MICROORGANISMS...............................................26
Soil Blanks Purge and Trap Analysis..............................................................................26
Soil-Treatment Product Blanks Purge and Trap Analysis...............................................26
Soil Blanks Diesel Range Organic Analysis ...................................................................27
Soil-Treatment Product Blanks Diesel Range Organic Analysis ....................................27
4.5 GASOLINE-CONTAMINATED SOIL...................................................................27
Soil-Gasoline-Water Blanks............................................................................................28
Soil-Gasoline Blanks.......................................................................................................31
Soil-Gasoline-Treatment Product Blanks........................................................................33
4.6 DIESEL-CONTAMINATED SOIL.........................................................................40
Soil-Diesel Blanks...........................................................................................................40
Soil-Diesel-Treatment Product Blanks............................................................................40
5.0 CONCLUSIONS..........................................................................................................45
5.1 GASOLINE..............................................................................................................45
5.2 DIESEL ....................................................................................................................48
6.0 RECOMMENDATIONS AND SUGGESTIONS .......................................................51
7.0 REFERENCES.............................................................................................................53
LIST OF FIGURES
Figure A: Location of Soil Samples .................................................................................. 2
Figure 1: Location of Soil Samples. ...................................................................................1
Figure 2: BTEX Chromatogram. ......................................................................................22
Figure 3: Chromatogram of n-Decane and n-Docosane. ..................................................23
Figure 4: Benzene Calibration Curve. ..............................................................................24
Figure 5: Toluene Calibration Curve. ...............................................................................24
Figure 6: Ethylbenzene Calibration Curve. ......................................................................25
Figure 7: m- and p-Xylene Calibration Curve. .................................................................25
Figure 8: o-Xylene Calibration Curve. .............................................................................25
Figure 9: C10 – C22 Calibration Curve...............................................................................26
Figure 10: Show Low Soil Contaminated with Gasoline and Treated with Micro-
Blaze. Note the Rapid Disappearance of the Benzene Peak..........................28
Figure 11: Toluene Levels in Soils Treated with Gasoline and Water. ............................31
Figure 12: Toluene Levels in Soils Contaminated with Gasoline. ...................................33
Figure 13: Toluene Levels in Mesa Soil. ..........................................................................35
Figure 14: Toluene Levels in Burro Creek Soil................................................................37
Figure 15: Toluene Levels in Show Low Soil. .................................................................39
Figure 16: Mesa Soil Contaminated with Diesel. .............................................................41
Figure 17: Burro Creek Soil Contaminated with Diesel...................................................42
Figure 18: Show Low Soil Contaminated with Diesel. ....................................................43
LIST OF TABLES
Table 1: Old Soil Remediation Levels................................................................................7
Table 2: New Soil Remediation Levels. .............................................................................7
Table 3: Soil Blank Sample Denomination. .....................................................................12
Table 4: Soil Gasoline Sample Denomination..................................................................12
Table 5: Soil Diesel Sample Denomination......................................................................13
Table 6: Operating Conditions for Diesel Analysis..........................................................14
Table 7: Purge and Trap Temperature Profile. .................................................................16
Table 8: Purge and Trap Unit Event Program. .................................................................17
Table 9: Physical Properties of the Soils. .........................................................................21
Table 10: BTEX Retention Times in Minutes. .................................................................22
Table 11: n-Decane and n-Docosane Retention Times.....................................................23
Table 12: BTEX Correlation Coefficients. .......................................................................24
Table 13: ADEQ's Soil Remediation Levels for BTEX and DRO Petroleum
Hydrocarbons....................................................................................................29
Table 14: Soil Types Contaminated with Gasoline and Treated with Water. ..................30
Table 15: Gasoline-Contaminated Soil Samples. .............................................................32
Table 16: Gasoline-Contaminated Mesa Soil Treated with Different Products. ..............34
Table 17: Gasoline-Contaminated Burro Creek Soil Treated with Different
Products. ...........................................................................................................36
Table 18: Gasoline-Contaminated Show Low Soil Treated with Different Products. .....38
Table 19: Diesel Blank Samples. ......................................................................................40
Table 20: Mesa Soil Treated with Different Products. .....................................................41
Table 21: Burro Creek Soil Treated with Different Products. ..........................................42
Table 22: Show Low Soil Treated with Different Products. ............................................43
Table 23: Normalized Initial Rates (5 Days) of Decay for Gasoline-Contaminated
Soils. .................................................................................................................46
Table 24: BTEX Scores; Lower Scores Indicate Greater Effectiveness...........................47
Table 25: BTEX Scores According to Soil Type..............................................................48
Table 26: Normalized Diesel Scores According to Soil Type After 83 Days. ................49
ACRONYMS
ADEQ Arizona Department of Environmental Quality
ADHS Arizona Department of Health Services
ADOT Arizona Department of Transportation
BTEX benzene, toluene, ethylbenzene, and xylene
CCV continuing calibration verification standard
DRO diesel range organics
EPA Environmental Protection Agency
FID flame ionization detector
GC/MS gas chromatography/mass spectrometry
HPLC high performance liquid chromatography
PAHs polycyclic aromatic hydrocarbons
PID photo ionization detector
QA/QC quality assurance/quality control
RPD relative percent difference
SRLs Arizona soil remediation levels
VOCs volatile organic compounds
1
EXECUTIVE SUMMARY
Each year vehicular accidents cause gasoline and diesel spills on Arizona roadways.
Reduction of petroleum products in soils occurs naturally through degradation from
physical and biological processes; it is of interest that an increase in the degradation rate
of petroleum products may occur with the application of bioremediation products.
Arizona Department of Transportation (ADOT) currently uses Micro-Blaze®, a
commercially available microbial solution, as a supplement to natural degradation of
vehicular petroleum spills in soils. However, its effectiveness in accelerating the
biodegradation of gasoline- or diesel-contaminated soils in Arizona has never been tested.
ADOT contracted with N. Weiss Associates, Inc., to determine the effectiveness of
Micro-Blaze as a commercial bioremediation product to remediate native soils
contaminated with gasoline or diesel fuels from vehicular accidents. With an emphasis
on minimizing or eliminating environmental and public health hazards, ADOT is
interested in determining cost-effective methods to address petroleum product spills from
roadway vehicular accidents. For this report, the specific issue investigated was whether
Micro-Blaze accelerated the degradation process significantly over natural processes.
During research for this project, other commercially available degradation products
(Hydro Clean® and Miracle-Gro®) were found and they, as well as water, were included
in the study. Micro-Blaze, Hydro Clean, Miracle-Gro, and water were studied to
determine their effectiveness in accelerating the remediation of petroleum products
(diesel No. 2 and unleaded gasoline) from roadway vehicular accidents on predominant
Arizona soil types.
ADOT responds to spills throughout the state of Arizona, encountering different soil and
climates. Arizona has three predominant soil types: aridisols, alfisols, and entisols. To
ensure that each soil type was represented, soil samples were taken from three
geographical areas (see Figure A for locations). The soils considered for the purpose of
this study are representative of soils found in Arizona.
 Burro Creek is representative of aridisols. Aridisols have relatively low organic
matter and low moisture storage capacity; they are common in dry regions.
 Show Low has alfisol soils. Alfisols have relatively low organic matter with high
base saturation; they are common in high elevations in semiarid and subhumid
regions.
 Mesa has significant entisols. Entisols have a thin surface with some accumulation
of organic matter and variable moisture content.
Show Low soil is the most porous, while the Mesa soil sample has the highest bulk and
particle density. Samples’ soil orders were distinguished using the dominant soil order
distribution maps of the United States Department of Agriculture (2008).
2
Figure A: Location of Soil Samples.
METHODOLOGY
The soils considered for the purpose of this study are considered representative of soils
found in Arizona. To obtain a consistent soil sample, each soil type was mixed
thoroughly and screened to remove larger particles, such as rocks and plant materials. To
determine the surface area and the water saturation capacity of the soil samples, a
picnometer was then used to measure the samples’ density, percent of dry mass, and
porosity.
The homogenized and mixed soil samples were contaminated with diesel No. 2 or
unleaded gasoline to create petroleum-spiked samples. The diesel and gasoline were
purchased on April 15, 2008, from a local retailer in Mesa, Arizona, and were used
without modifications. Solutions of the bioremediation products Micro-Blaze, Hydro
Clean, or Miracle-Gro fertilizer mixed with water were then added to the spiked samples.
Ultrapure water was used in place of bioremediation products for blank samples.
To represent physical degradation through evaporation or dissolution, the sample tubes
were uncapped and placed outside in the sunlight for 48 hours. After this time, the initial
extraction and analysis was performed. The spiked samples were still wet, but excess
liquid was not present. These initial analyses represented the starting point for measuring
the rate of degradation of gasoline or diesel in the spiked samples. Extraction of diesel
and gasoline from the spiked soil samples was conducted by using appropriate solvents
and a centrifuge to separate the dissolved contaminant and the soil. Following extraction,
gas chromatography was used to analyze the diluted contaminant solutions.
The contaminated diesel and gasoline samples were evaluated and compared by using a
ranking methodology. First, scores for each sample were determined by comparing
different types of soil exposed under the same conditions and by comparing different
types of microorganisms and nutrients. Each gasoline sample was assigned a total
cumulative score for benzene, toluene, ethylbenzene, m- and p-xylene, and o-xylene.
Each diesel sample was assigned a score by analyzing the C10-C22 range and comparing
the milligrams of C10-C22 in a kilogram of dry soil to initial levels. Second, the rate of
change was calculated between the first and last day of evaluation. Third, the lowest
3
value for the rate of change was assigned a score of one, and scores were assigned
successively to the last sample. The lowest score represented the best remediation option
analyzed for the type of soil (Hristovski et al. 2008). Also, the different types of soil,
remediation, and added nutrients were compared using this technique.
CONCLUSIONS
All three soil types contaminated with gasoline showed a reduction in benzene, toluene,
ethylbenzene, and xylene (BTEX) levels to below Arizona Department of Environmental
Quality’s (ADEQ’s) soil remediation levels (SRLs) within 21 days, even in the absence
of added microorganisms or nutrients. However, in trying to compare the rates of
degradation among various options, some degree of quantification can be obtained by
normalizing the BTEX concentration and measuring the rate of decay. This was done by
comparing the change in concentration by the number of days between measurements,
resulting in a rate of degradation suitable for comparison.
The most effective treatment for gasoline-contaminated Mesa soils was to add Miracle-
Gro. For Burro Creek and Show Low soils, Miracle-Gro was the second most effective
treatment for gasoline contamination, with the most effective being to leave the soils
alone (without adding water or other products). Micro-Blaze treatment was rated either
number 3 or 4, while Hydro Clean was rated number 3, 4, or 5 out of the five possible
treatment options. However, the most important observation is that all soil samples
contaminated with gasoline were below the residential Arizona SRLs by day 21, no
matter what treatment option was employed. There was some acceleration with certain
treatments, but all samples ultimately decayed to approximately the same levels of
BTEX.
The situation with diesel-contaminated soils was quite different. In none of the sample
treatments was the diesel (total petroleum hydrocarbon) concentration below either
residential or non-residential SRLs by day 83. For Burro Creek and Show Low soils, the
optimal treatment was with Hydro Clean, and this was the second-best treatment option
for Mesa soils. Micro-Blaze was the optimal treatment for Mesa soils and the second
best for Burro Creek soils. In all soils, treatment with Miracle-Gro resulted in an actual
increase in measured diesel range organics (DRO) after 83 days; Micro-Blaze also had
this effect in Show Low soils. This is likely due to a division of long chain organics into
smaller fragments, which are still included in the DRO sampling range.
RECOMMENDATIONS
Even though the State of Arizona no longer has an SRL for total petroleum hydrocarbons,
it is prudent to take action to remediate. Clean-up of petrochemical hydrocarbons will
protect stormwater and surface water and eliminate environmental and public health
hazards.
Further research in the area of polycyclic aromatic hydrocarbons (PAHs) in soils from
diesel fuel spills and from incomplete combustion of carbon-containing fuels should be
considered.
4
Changes in research design should be considered to include in situ application of
remediation products. The research was performed in a laboratory situation. The rate at
which volatile organic compounds (VOCs) decayed was in days as opposed to weeks,
which would have been expected if research occurred in situ.
Further research with gas chromatography/mass spectrometry (GC/MS) may be useful to
confirm the breakdown of DRO into smaller hydrocarbon chains. The increase in DRO
may be a result of larger-chain hydrocarbon being broken down from large chains to
smaller chains, causing DRO numbers to increase.
It also would be prudent to consider further evaluation of other products listed on the
Environmental Protection Agency’s (EPA) National Contingency Plan Subpart J Product
Schedule of dispersants, other chemicals, and oil spill mitigating devices and substances
that may be used to remove or control oil discharges. Research associated with the
control of oil from rubberized asphalt and other asphaltic materials is a related area that
warrants further investigation.
5
1.0 INTRODUCTION
The Arizona Department of Transportation (ADOT) is interested in determining cost-effective
methods that would minimize or eliminate environmental and public health
hazards from petroleum product spills in roadway vehicular incidents. ADOT contracted
with N. Weiss Associates, Inc., to determine whether commercial bioremediation
products might be used to remediate soils contaminated with gasoline or diesel fuels.
N. Weiss Associates, Inc., subcontracted with the Environmental Technology
Management program at Arizona State University to conduct laboratory-based
experiments to evaluate the feasibility of this approach.
ADOT currently uses a microbial solution called Micro-Blaze® for soil remediation in
small accidents. However, its effectiveness in accelerating the biodegradation of
gasoline- or diesel-contaminated soils has never been tested. Natural degradation of
petroleum products can occur through physical processes such as evaporation or
dissolution and also through biodegradation from naturally occurring organisms in soils.
The specific issue to be tested was whether Micro-Blaze accelerated the degradation
process significantly compared to natural processes.
Other commercially available biodegradation products were discovered during the
literature review for this project. Two materials—Hydro Clean, made by Desert Shield,
and a plant fertilizer made by Miracle-Gro®— were tested in addition to Micro-Blaze. A
fourth set of experiments was conducted with no additional product except water applied
to the contaminated soils.
Because ADOT must respond to spills throughout Arizona, different soil types and
climates are encountered. There are three predominant soil types in Arizona:
 Aridisols with relatively low organic matter and low moisture storage capacity;
common in dry regions
 Alfisols with relatively low organic matter with high base saturation; common in
high elevations in semiarid and subhumid regions
 Entisols have a thin surface with some accumulation of organic matter and
variable moisture content.
In this project, three different soil samples from different geographic areas of the state
were selected. Aridisols are found in soils from Burro Creek; alfisols are found in soil
from Show Low; and entisols are found in soils from Mesa.
7
2.0 BACKGROUND
Of interest to this study, the Arizona Soil Remediation Level (SRL) Rule for remediating
sites with soil contaminations changed during the course of this project. Included in
Tables 1 and 2 are the old and new standards. The new standard does not include
hydrocarbon remediation levels. This project began prior to the change, and the results
reference the old standard. However, the change in standard does not affect the project
findings as shown in Tables 1 and 2.
Table 1: Old Soil Remediation Levels.
Chemical Name SRL Residential
(mg/kg)
SRL Non-Residential
(mg/kg)
Benzene 0.62 1.4
Ethylbenzene 1500 2700
Toluene 790 2700
Xylene 2800 2800
Hydrocarbon
C10-C32
4100 18000
Table 2: New Soil Remediation Levels.
Chemical Name SRL Residential
(mg/kg)
SRL Non-Residential
(mg/kg)
Benzene 0.65 1.4
Ethylbenzene 400 400
Toluene 650 650
Mixed Xylene 270 420
Hydrocarbon
C10-C32
None None
9
3.0 METHODOLOGY
3.1 SOILS PREPARATION
Soil samples of native Arizona soils were obtained from Burro Creek, Show Low, and
Mesa (see Figure 1 for locations). Each soil type was homogenized and mixed
thoroughly using a trowel, and then sieved through a screen with a 2 mm diameter
opening (Standard test sieve, ASTM E-11 specification, US Mesh No. 10) to remove
larger particles such as rocks and plant materials. The prepared loose soils were stored in
capped glass containers at room temperature.
Burro Creek
Show Low
Mesa
A picnometer was employed to determine density, percent of dry mass content, and
porosity of the soil samples. The following steps were undertaken using a 30 mL
picnometer:
1. The picnometer was dried in the oven at 105º C for one hour.
2. The picnometer was cooled in a desiccator to room temperature.
3. The picnometer was weighed, and the mass of the dry picnometer was recorded.
4. A sample of sieved soil was added to the picnometer; it was weighed, and the
mass was recorded.
5. The picnometer with the soil sample dried overnight at 105 ºC to constant mass,
and it was cooled to room temperature in a desiccator.
6. The picnometer with the soil was weighed, and the mass was recorded.
7. Ultrapure water was added to the picnometer filled with soil. The picnometer was
weighed, and the mass was recorded.
8. The extra water was removed, and the picnometer with wet soil was weighed.
Figure 1: Location of Soil Samples.
10
The porosity ε was determined once the bulk density ρb and the particle density ρp were
known, using the following equation (Sontheimer et al. 1988).
ε = 1 – ρb
ρp
The bulk density ρb represents the ratio of the mass of dry solids to the bulk volume of
the soil V, and it was calculated using
ρb = ms - ma
V
The particle density ρp was determined using
ρp = ms - ma
V – (mst –ma) – (msw – ma)
ρw
where ρw is the density of the water, ms is the picnometer weight containing the soil
sample dried in the oven, ma is the empty (air-filled) picnometer weight, msw is the
picnometer weight when filled with soil and water, and mst is the picnometer weight with
V =  - msw - mst
ρw
where  is the picnometer volume. Wilke (2005) used the following equation to obtain
the dry mass content mdm expressed in percentage by mass, where mm is the mass of the
picnometer filled with soil sample that was not dried. The obtained results for the
different types of soils are shown in the Results section of this report.
mdm = ms – ma x 100
mm - ma
3.2 PREPARATION OF SAMPLES
Soil samples from Burro Creek, Show Low, and Mesa were prepared by weighing 45 g of
soil into 60-mL pre-cleaned glass vials that were cleaned to U.S. Environmental
Protection Agency (EPA) standards. Spiked soil samples were prepared using diesel No.
2 and unleaded gasoline, which were purchased on April 15, 2008, from a local supplier,
Circle K (4353 S. Power Rd., Mesa, AZ 85212), and used without modifications.
Dilutions of 5 % v/v of the commercial gasoline and diesel in methanol and
dichloromethane, respectively, were prepared to determine the fuel compositions by gas
chromatography. Details of the gas chromatographic analysis are provided later in this
section. Aqueous solutions of the bioremediation products Micro-Blaze or Hydro Clean
or the fertilizer Miracle-Gro were then added to the spiked samples. Ultrapure water was
used in place of bioremediation products for blank samples.
11
Soil Sample Procedures for Soil-Gasoline-Water Blanks
Forty-five grams of soil were weighed in a 60-mL pre-cleaned glass vial, and 10 mL of
commercial gasoline were added. The vial was capped, and the sample was
homogenized by shaking until the soil was saturated with the contaminant. Five mL of
ultrapure water were added, and the sample was homogenized by shaking until the soil
was saturated.
Soil Sample Procedures for Soil-Diesel Blanks
The sample was prepared by weighing 45 g of soil in a 60-mL pre-cleaned glass vial, and
10 mL of commercial diesel fuel were added. The vial was capped, and the sample was
homogenized by shaking until the soil was saturated with the contaminant. Five mL of
ultrapure water were added, and the sample was homogenized by shaking until the soil
was saturated.
Soil Sample Procedures for Soil-Treatment Product Blanks
Samples were prepared by weighing 45 g of soil in a 60-mL pre-cleaned glass vial and 5
mL of an aqueous solution of Micro-Blaze, Hydro Clean, or Miracle-Gro were added.
The vial was capped and the sample was homogenized by shaking until the soil was
saturated with the solution.
Soil Sample Procedures for Soil-Gasoline-Treatment Product Blanks
Forty-five grams of soil were weighed in a 60-mL pre-cleaned glass vial, and 10 mL of
commercial gasoline were added. The vial was capped, and the sample was
homogenized by shaking until the soil was saturated with the contaminant. Five mL of
Micro-Blaze, Hydro Clean, or Miracle-Gro solution were then added, and the sample was
homogenized by shaking until the soil was saturated.
Soil Sample Procedures for Soil-Diesel-Treatment Product Blanks
Forty-five grams of soil were weighed in a 60-mL pre-cleaned glass vial, and 10 mL of
commercial diesel fuel were added. The vial was capped, and the sample was
homogenized by shaking until the soil was saturated with the contaminant. Five mL of
Micro-Blaze, Hydro Clean, or Miracle-Gro solution were then added, and the sample was
homogenized by shaking until the soil was saturated.
Tables 3, 4, and 5 describe the designation for the samples prepared during the study.
12
Table 3: Soil Blank Sample Denomination.
Sample No. Soil Contaminant Treatment
1  X
2  X
3  X
4  Y
5  Y
6  Y
7  Z
8  Z
9  Z
Note:  = Mesa soil;  =Burro Creek soil;  = Show Low soil;
X = Micro-Blaze; Y = Hydro Clean; Z = Miracle-Gro. No contaminant added.
Table 4: Soil Gasoline Sample Denomination.
Sample No. Soil Contaminant Treatment
1  X
2  X
3  X
4  Y
5  Y
6  Y
7  Z
8  Z
9  Z
Note:  = Mesa soil;  =Burro Creek soil;  = Show Low soil;
X = Micro-Blaze; Y = Hydro Clean; Z = Miracle-Gro.
Contaminant type is gasoline for all samples.
13
Table 5: Soil Diesel Sample Denomination.
Sample No. Soil Contaminant Treatment
25  D
26  D
27  D
28  D X
29  D X
30  D X
31  D Y
32  D Y
33  D Y
34  D Z
35  D Z
36  D Z
Note:  = Mesa soil;  =Burro Creek soil;  = Show Low soil;
X = Micro-Blaze; Y = Hydro Clean; Z = Miracle-Gro.
Contaminant type is gasoline for all samples.
3.3 EXTRACTION AND ANALYSIS
All of the sample tubes listed in Tables 3–5 were uncapped and placed outside in the
sunlight for 48 hours. The initial extraction and analysis were conducted after 48 hours.
At this point, the spiked samples were still wet, but there was no excess liquid present.
These initial analyses represented the starting point for measuring the rate of degradation
of gasoline or diesel in the spiked samples.
Diesel Extraction
The diesel extraction was conducted by weighing 1 g of soil sample from the 60 mL vial
and placing it in a 20 mL vial (20 mL, clear w/septa, I-CHEM). The samples were
capped immediately to prevent contaminant loss due to evaporation and labeled with the
sample’s name and date.
Diesel range organics, C10-C22, were extracted from the soil samples using anhydrous
dichloromethane (99.9+ %, Alfa Aesar, Lot # D125037). A volume of 10 mL of
dichloromethane (99.9+ %, Alfa Aesar, Lot # D125037) was added to each 20 mL glass
vial, and the samples were sonicated for a period of 15 min. The samples were
centrifuged at F ~ 1300 G for a period of 5 minutes to separate the soil and
dichloromethane. The extraction process of all the samples was completed during the
same day to ensure the same experimental conditions. Duplicate samples were prepared
14
for every 10 samples using the same procedures. All samples were cooled to 4 ± 2º C
and analyzed within 14 days of sampling.
The diesel-containing samples were diluted with anhydrous dichloromethane by a factor
of 20. Syringes were used to make the dilutions, and the samples were stored in a 2 mL
glass vial (2 mL, 9 mm, Ultra, wide-mouth screw vial).
Diesel Analysis
The dilutions were analyzed using gas chromatography following Method 8015AZ-Revision
1.0 for detection of C10-C22 hydrocarbon range in soil. Quantitative and
qualitative analysis of C10-C22 diesel range was determined using a Varian Model 3800
gas chromatograph equipped with VARIAN Capillary column, Select Mineral Oil, 15 m,
0.32 mm #CP7491, a Model 1079 injector, a Model 8200 auto-sampler and a flame
ionization detector operating at 340 ºC. The analyzed dilutions were prepared in 2-mL
Varian Ultra gas chromatography/mass spectrometry (GC/MS) vials (clear glass wide-opening
screw-top vials with ultra GC/MS liners). Component identification was
conducted by comparing the resident times of purchased standards, n-decane (1000 mg,
neat, 442669, Supelco, Lot # LB45279) and n-docosane (1000 mg, neat, 442670,
Supelco, Lot # LB32530). All samples were analyzed using the Star Chromatography
Workstation version 6.3. Table 6 summarizes instrument conditions necessary to achieve
separation between the diesel fuel components.
Table 6: Operating Conditions for Diesel Analysis.
The instrument was calibrated using a five-point linear calibration curve (not forced to
zero). Calibration standards of 30, 100, 200, 500, and 1000 g/mL were obtained by
15
dilution of a composite No. 2 diesel fuel standard solution (50,000 μg/mL in
dichloromethane; ULTRA Scientific; Lot # M-1431) in anhydrous dichloromethane
(99.9+ %, Alfa Aesar, Lot # D125037). The goodness of fit (R2) was 0.9977 using linear
regression. The calibration curve for the C10-C22 range is shown in Section 4, Results.
Diesel range (C10-C22) concentrations were reported between 1.4 min. and 20 min. to
assure the C10-C22 range, as the n-decane (C10) retention time was 1.570 min. and the n-docosane
(C22) retention time was 18.957 min., and those have a little variation. The
n-decane and n-docosane chromatogram and retention times are shown in Section 4.2,
Qualitative Analysis. The mass of diesel range aliphatic hydrocarbons (C10-C22) was
calculated by determining the total area of the peaks between retention times 1.4 min. and
20 min. and then comparing it to the total area obtained from the calibration curve. The
mass was reported in nanograms (ng). All the obtained data were analyzed and presented
as milligrams of contaminant per kilogram of dry soil (mg/kg).
Quality Assurance and Quality Control
Quality assurance and quality control (QA/QC) procedures were followed using blanks,
spikes, and standard solutions. QA/QC equations and procedures from Arizona
Department of Health Services (ADHS) Method 8015AZ- Revision 1.0 (1998) were
used. A method blank, dichloromethane (99.9+ %, Alfa Aesar, Lot # D125037), was run
before every analysis of diesel samples. A continuing calibration verification standard
(CCV) solution, composite No. 2 diesel fuel standard solution (500 μg/mL), was
analyzed at the beginning of each analytical run and after every 10 samples analyzed. An
acceptable percent recovery of the CCV was between 70% and 130% of the true value.
Percent recovery was calculated using the following equation:
Percent recovery = R1 x 100
R2
where R1 is the measured amount of the analyzed component and R2 is the true value.
A spiked sample, a soil sample in dichloromethane with composite No. 2 diesel fuel
standard solution (500 μg/mL), was prepared using the same procedures as the other
diesel samples and was run every time the GC was used to guarantee the accuracy of the
method. The following equation was used to calculate the spike recovery:
Percent Spike Recovery = S – R x 100
C
where S is the measured spiked sample result, R is the concentration of the sample before
the spike, and C is the actual spike concentration. An acceptable percent spike recovery
was between 70% and 130%.
Relative percent difference (RPD) was used to calculate the precision from duplicate
samples measured. The following equation was used for calculating the percent RPD:
16
% RPD = X1 – X2 x 100
[(X1 + X2)/2]
where X1 and X2 are the two measurements being compared. An acceptable RPD was
between 0 and 20%.
Gasoline Extraction
Gasoline was extracted from soil samples by weighing 1 g of soil from the 60 mL vial
sample and suspending it in 10 mL methanol (99.9+%, Sigma-Aldrich Chemie GmbH,
GC grade, Batch # 04555 BD) in 20 mL pre-cleaned vials. To make possible the
extraction of the contaminants from the soil, all sample vials were placed in a sonicator
bath for 15 min. After sonication, the vials were centrifuged for 5 min. at F ~ 1300G.
Syringes were utilized to prepare the dilutions of the soil sample to be analyzed in a gas
chromatograph purge and trap. Syringes were cleaned by rinsing them three times with
99%+ methanol solution.
Gasoline Analysis
Method 8015AZ, revision 1.0, was used for benzene, toluene, ethylbenzene, and xylene
(BTEX) detection and quantification in soil (Arizona Department of Health Services,
1998). Analysis was performed using a SRI 8610B gas chromatograph purge and trap
(SRI Instruments, Inc.), equipped with two detectors: a flame ionization detector (FID),
and a photo ionization detector (PID). The results were obtained using a Restek fused
silica, phase MTX-1, 60 m column (0.53 mm, cat #70183-273, serial # 815473) and
helium as a gas carrier. Table 7 illustrates the temperature profile used during the 29.666
min. analysis. Table 8 shows the event program for the purge and trap unit, which was
used during analysis of the gasoline samples. The BTEX separation peaks attained using
these conditions are shown in Section 4, Results.
Table 7: Purge and Trap Temperature Profile.
17
Table 8: Purge and Trap Unit Event Program.
Identification of the gasoline constituents was based on the retention times. BTEX
components were selected as representative fingerprint components to determine the
concentration of gasoline in the samples. Retention times were identified for the BTEX
components using purchased standards. Information about the purchased standards and
their retention times is presented in Section 4, Results.
After identification of each BTEX compound, dilutions of BTEX standard solutions were
analyzed to calibrate the equipment. m-Xylene and p-xylene were reported together
because there was no peak separation between these compounds under these operating
conditions. Five dilutions of a BTEX mix standard solution (2,000 μg/mL in methanol;
Supelco; Lot # LB46930) at concentrations of 10 μg/mL, 20 μg/mL, 50 μg/mL, 100
μg/mL, and 200 μg/mL in methanol (99.9+%, Sigma-Aldrich Chemie GmbH, GC grade,
Batch #04555 BD) were prepared and analyzed to create a calibration curve. Linear
calibration (not forced to zero) was conducted over the range of 10-200 g/mL for the
five target BTEX compounds with a run time of 29.666 min and a purge volume of 5 mL
high performance liquid chromatography (HPLC) grade water (Fluka). All the analyzed
18
samples were purged, from a Pyrex culture tube 16x125 mm, with 5 mL of HPLC grade
water (Fluka).
The data for the instrument calibration and samples analyzed were processed using
PeakSimple 3.59 software. An R2 of 0.995 or better of acceptance criteria was used in
the construction of the BTEX calibration curves. The calibration curves of BTEX
compounds are illustrated in Section 4, Results. The mass of each BTEX component was
calculated by determining the area of representative peak and by comparing it to the area
obtained from the calibration curve. The mass was reported in nanograms (ng). All data
obtained from soil samples were analyzed and presented as milligrams of contaminant
per kilogram of dry soil (mg/kg).
Quality Assurance and Quality Control
To ensure that the instrument was properly calibrated, the calibration curve was validated
every time the instrument was used by running a BTEX standard solution with a
concentration of 50 μg/mL and examining the percent recovery of the target analytes.
The percent recovery was calculated in the same manner as for the diesel samples.
Blank standards were run using 5 mL of HPLC grade water (Fluka) to ensure that there
was no carryover contamination. A purchased standard solution of α,α,α-trifluorotoluene
(1000 mg, neat, 442429, Supelco, Lot No LB33410) was used as an internal standard.
Each sample was injected with 10 μL of α,α,α-trifluorotoluene (100 μg/mL in methanol)
to ensure proper instrument operation. The acceptance range for internal standard
recovery was between 70% and 130% of true value as defined by ADHS Method
8015AZR1 (1998).
Duplicate samples were analyzed every 10 samples to estimate sample variability. The
results from the duplicate samples were compared and evaluated using RPD. A CCV
standard solution, standard BTEX (20 μg/mL) solution in methanol, was analyzed at the
beginning of each analytical run and for every 10 samples analyzed. The percent
recovery of the CCV was between 70% and 130% of the true value. Percent recovery
was calculated as described above.
A gram of spiked sample in methanol with a known amount of standard BTEX
(50 μg/mL) was analyzed every 20 analytical runs to check the appropriateness of the
method for the soil matrix. The percent spike recovery, as described above, was used to
evaluate the accuracy of the method.
3.4 RANKING METHODOLOGY
A ranking methodology was used to evaluate and compare different diesel and gasoline
contaminated samples. Also, the different types of soil, remediation, and added nutrients
were compared using this technique.
19
Gasoline Ranking Methodology
For gasoline samples, the benzene, toluene, ethylbenzene, m-xylene, p-xylene and o-xylene
normalized values ((mg/kg)/(mg/kg)o) were each analyzed comparing different
types of soil exposed under the same conditions. Next, the benzene, toluene,
ethylbenzene, m-xylene, p-xylene, and o-xylene normalized values ((mg/kg)/(mg/kg)o)
were each analyzed comparing different types of microorganism and nutrient treatments.
Third, a number was obtained from the rate of change of the normalized values
d((mg/kg)/(mg/kg)o)/dt, which was calculated from the first and last data obtained from
the first and last day of analyses. Fourth, the lowest rate of change
d((mg/kg)/(mg/kg)o)/dt was assigned a score of 1, the second lowest value was assigned
a score of 2, and so on successively to the last sample. A total cumulative score for each
sample was calculated by adding the scores for benzene, toluene, ethylbenzene, m-xylene,
p-xylene, and o-xylene. The sample with the lowest total score represented the
best of the remediation options studied for a type of soil (Hristovski et al. 2008).
Diesel Ranking Methodology
In the diesel range (C10-C22), the following ranking methodology was used to evaluate the
results obtained from different samples. First, the C10-C22 range was analyzed in all
samples, and the amounts were normalized to initial milligrams of C10-C22 per kilogram
of soil for different types of soil and treatment products. Second, the rate of change
d((mg/kg)/(mg/kg)o)/dt between the first and last day of evaluation was calculated.
Third, the lowest value of d((mg/kg)/(mg/kg)o)/dt was assigned a score of 1, and higher
values were assigned successive numbers to the last sample. The lowest score
represented the best remediation option analyzed for the type of soil (Hristovski et al.
2008).
21
4.0 RESULTS
4.1 PHYSICAL PROPERTIES OF THE SOILS USED IN THE PROJECT
The soils considered for the purpose of this study are considered representative of soils
found in Arizona. Table 9 summarizes the types of soils used in the study and some of
their physical properties. Show Low soil is characterized by highest porosity, while the
Mesa soil sample has the highest bulk and particle density. Samples’ soil orders were
distinguished using the dominant soil order distribution maps of the United States
Department of Agriculture (2008).
Table 9: Physical Properties of the Soils.
4.2 QUALITATIVE ANALYSIS
Gasoline
Aliquots of benzene, toluene, ethylbenzene, o-xylene, m-xylene, and p-xylene standard
solution were injected in a SRI 8610B gas chromatograph purge and trap. These samples
were analyzed to determine the retention time of each BTEX compound at working
settings in the equipment (i.e., the operating conditions of the chromatograph). Figure 2
shows the peak separation and retention times of each BTEX compound. BTEX
compounds have different boiling points; consequently, their retention times are different.
Table 10 details the retention times obtained by analyzing standards of each BTEX
compound under these operating conditions.
22
Figure 2: BTEX Chromatogram.
Table 10: BTEX Retention Times in Minutes.
Diesel
Standard solutions of n-decane and n-docosane were analyzed in a Varian Model 3800
gas chromatograph to identify the limits and retention times of C10-C22 diesel range.
Figure 3 shows the identification and retention time of n-decane and n-docosane.
Table 11 shows the retention times of n-decane and n-docosane under these operating
conditions.
23
Figure 3: Chromatogram of n-Decane and n-Docosane.
Table 11: n-Decane and n-Docosane Retention Times.
4.3 QUANTITATIVE ANALYSIS
Gasoline Calibration Curves
The level of gasoline contamination in soil was expressed as the mass of BTEX
compounds contained in a kilogram of dry soil. To quantify the BTEX contained in soil,
the equipment was calibrated using dilutions of BTEX standard solution in methanol.
Table 12 shows the correlation coefficients obtained for each BTEX compound
calibration curve using a FID detector. The BTEX compound calibration curves obtained
by using a FID detector are showed in Figures 4 through 8.
24
Table 12: BTEX Correlation Coefficients.
Figure 4: Benzene Calibration Curve.
Figure 5: Toluene Calibration Curve.
25
Figure 6: Ethylbenzene Calibration Curve.
Figure 7: m- and p-Xylene Calibration Curve.
Figure 8: o-Xylene Calibration Curve.
26
Diesel Calibration Curve
The diesel range organics (DRO) range of C10-C22 was analyzed in samples contaminated
with diesel No. 2. Before soil analysis, dilutions of composite No. 2 diesel fuel standard
solution (50,000 μg/mL in dichloromethane) were used to calibrate the equipment. The
calibration curve for the C10-C22 range is exhibited in Figure 9.
Figure 9: C10 – C22 Calibration Curve.
4.4 ANALYSIS OF SOIL AND TREATMENTS
Soil Blanks Purge and Trap Analysis
The initial contamination of each type of soil was tested by placing a gram of soil in a test
tube with 5 mL of ultrapure water. The mixture was analyzed in a purge and trap GC
under the same conditions as the contaminated samples. During the soil blank analysis,
no background BTEX contamination above detection levels was found in any of the three
types of soil.
Soil-Treatment Product Blanks Purge and Trap Analysis
The two different types of microorganisms and an aqueous solution of the added nutrients
utilized in this study were first analyzed, without gasoline contamination, by purge and
trap analysis. The soil-treatment product blanks were prepared and tested under the same
conditions as the gasoline-contaminated samples. No BTEX contaminants were observed
in the analysis of Micro-Blaze, Hydro Clean, or Miracle-Gro in the three different types
of soil.
27
Soil Blanks Diesel Range Organic Analysis
Before DRO analysis, each type of soil was analyzed alone to identify possible initial
DRO contamination. In this analysis, 1 g of soil was placed in a 20 mL vial with 10 mL
of dichloromethane, and an aliquot was analyzed in the Model 3800 GC. No DRO
contamination above detection limits was found in any of the three types of soil.
Soil-Treatment Product Blanks Diesel Range Organic Analysis
Micro-Blaze, Hydro Clean, and Miracle-Gro products were initially tested without diesel
contamination by the GC 3800. The procedures used to prepare the samples were the
same as those used for the diesel-contaminated soil samples (described in Section 3.2).
The results showed no DRO-range contamination above detection limits in the
commercial products and soils tested.
4.5 GASOLINE-CONTAMINATED SOIL
The results from the analysis of gasoline-contaminated soil samples were expressed in
milligrams of contaminant contained per kilogram of dry soil. The results are shown
only for toluene, ethylbenzene, m-xylene, p-xylene, and o-xylene. Benzene results were
not shown because benzene concentrations were out of range of the benzene calibration
curve (lower than the lowest benzene calibration point) by the second time that the
samples were analyzed. 100 g of benzene per kilogram of soil was the minimum
detection limit for the method described in Section 3, Methodology. The Arizona
Department of Environmental Quality’s (ADEQ) benzene soil remediation level is
0.62 mg/kg for residential soils and 1.4 mg/kg for non-residential soils. ADEQ’s benzene
residential SRL was attained before day 7 of the study. An example of the benzene peak
disappearance can be seen in Figure 10, where the progressive degradation of BTEX
compounds can be observed.
28
Figure 10: Show Low Soil Contaminated with Gasoline and Treated
with Micro-Blaze. Note the Rapid Disappearance of the Benzene Peak.
Soil-Gasoline-Water Blanks
The three different types of soil were contaminated with gasoline and 5 mL of ultrapure
water was added in each sample. These samples were prepared to compare untreated
gasoline-contaminated samples with gasoline-contaminated samples that were treated
with different microorganisms or nutrients. Both types of contaminated samples, those
receiving no treatment and those treated with microorganisms or nutrients, had the same
moisture level. Table 14 illustrates the results obtained for toluene, ethylbenzene, and
xylenes. Benzene was not included because it was below the detection limit by the
second measurement.
Duplicate samples for every 10 samples were prepared and analyzed to determine
precision of measurements. ADEQ’s toluene, ethylbenzene, and xylenes SRLs were
29
attained in less than 21 days when the three different types of soil were treated only with
water. Graphic results of toluene levels in different types of soil treated with water can
be seen in Figure 11. Figure 11 demonstrates that the toluene levels in the three types of
soil become lower than ADEQ’s toluene SRL (see Table 13).
Table 13: ADEQ's Soil Remediation Levels for BTEX and
DRO Petroleum Hydrocarbons.
30
Table 14: Soil Types Contaminated with Gasoline and Treated with Water.
Note: α = Mesa soil; β = Burro Creek soil; δ = Show Low soil; W= Water.
Mg/kg=milligrams of contaminant contained in a kilogram of dry soil.
*= Duplicate sample.
31
Figure 11: Toluene Levels in Soils Treated with Gasoline and Water.
Soil-Gasoline Blanks
Samples prepared with three different types of soil and commercial gasoline, without
added water, were also analyzed. Table 15 describes the results obtained for toluene,
ethylbenzene, and xylenes. The precision of the method was assured by a relative percent
difference lower than 20 in duplicate samples. Figure 12 shows the gasoline evaporation
rate for the three different types of soils and shows that the ADEQ’s toluene SRL was
attained by the second sampling date, on day 7 of the study. However, the final levels
after day 21 were slightly higher than the final levels in samples to which water was
added (shown in Table 14).
Mesa-Gasoline-Water
Burro Creek –Gasoline-
Water
Show Low-Gasoline-
Water
ADEQ’s Toluene SRL
during 2006
32
Table 15: Gasoline-Contaminated Soil Samples.
Note: α = Mesa soil; β = Burro Creek soil; δ = Show Low soil; G= Gasoline.
Mg/kg=milligrams of contaminant contained in a kilogram of dry soil.
*= Duplicate sample.
33
Figure 12: Toluene Levels in Soils
Contaminated with Gasoline.
Soil-Gasoline-Treatment Product Blanks
The three commercial products, Micro-Blaze, Hydro Clean, and Miracle-Gro, were tested
under the same conditions in different types of gasoline-contaminated soils. The
precision of the method was assured by acceptance criteria of a relative percent
difference of less than 20% in duplicate samples.
Table 16 details the results obtained during the analysis of the three products treating
Mesa soil contaminated with gasoline. Table 17 shows the results for Burro Creek soil
and Table 18 the results for Show Low soil. Figures 13 through 15 show the toluene
levels in Mesa, Burro Creek, and Show Low soils, respectively, after no treatment,
treatment with water, and treatment with each of the three products.
The results for all three soil types and treatment methods are similar to those in Tables 14
and 15, where no commercial treatments were applied. In all cases, the final
concentrations by day 21 were below ADEQ’s SRLs.
Mesa-Gasoline
Burro Creek -Gasoline
Show Low-Gasoline
ADEQ’s Toluene SRL during 2006
34
Table 16: Gasoline-Contaminated Mesa Soil
Treated with Different Products.
Note: α = Mesa soil; β = Burro Creek soil; δ = Show Low soil; G= Gasoline;
X=Micro-Blaze; Y= Hydro Clean; Z= Miracle-Gro. Mg/kg=milligrams of
contaminant contained in a kilogram of dry soil. *= Duplicate sample.
35
Figure 13: Toluene Levels in Mesa Soil.
Mesa-Gasoline-Water
Mesa-Gasoline
Mesa-Gasoline-Micro-Blaze
Mesa-Gasoline-Hydro Clean
Mesa-Gasoline-Miracle-Gro
ADEQ’s Toluene SRL during 2006
36
Table 17: Gasoline-Contaminated Burro Creek Soil
Treated with Different Products.
Note: β = Burro Creek soil; G= Gasoline; X=Micro-Blaze; Y= Hydro Clean;
Z= Miracle-Gro. Mg/kg=milligrams of contaminant contained in a kilogram
of dry soil. *= Duplicate sample.
37
Figure 14: Toluene Levels in Burro Creek Soil.
Burro Creek-Gasoline-Water
Burro Creek-Gasoline
Burro Creek-Gasoline-Micro-Blaze
Burro Creek-Gasoline-Hydro Clean
Burro Creek-Gasoline-Miracle-Gro
ADEQ’s Toluene SRL during 2006
38
Table 18: Gasoline-Contaminated Show Low Soil
Treated with Different Products.
Note: α = Mesa soil; β = Burro Creek soil; δ = Show Low soil; G=Gasoline;
X=Micro-Blaze; Y= Hydro Clean; Z= Miracle-Gro; RPD% = Relative Percent
Difference; Mg/kg=milligrams of contaminant contained in a kilogram of dry
soil. *= Duplicate sample.
39
Figure 15: Toluene Levels in Show Low Soil.
Show Low-Gasoline-Water
Show Low-Gasoline
Show Low-Gasoline-Micro-
Blaze
Show Low-Gasoline-Hydro
Clean
Show Low-Gasoline-Miracle-
Gro
ADEQ’s Toluene SRL during
2006
40
4.6 DIESEL-CONTAMINATED SOIL
Soil-Diesel Blanks
Diesel range organics C10-C22 were analyzed, according to the methodology described in
Section 2.2, from the three different types of soil contaminated with commercial diesel
No. 2 without any added treatments. The results are shown in Table 19. After 83 days,
the DRO concentration in soil was still greater than the ADEQ diesel limits for soils.
Table 19: Diesel Blank Samples.
Note: α = Mesa soil; β = Burro Creek soil; δ = Show Low soil; D =Diesel;
Mg/kg=milligrams of contaminant contained in a kilogram of dry soil.
*= Duplicate sample.
Soil-Diesel-Treatment Product Blanks
The three commercial products, Micro-Blaze, Hydro Clean, and Miracle-Gro, were
applied to the different types of soil contaminated with the same amount of diesel No. 2.
Table 20 shows the results obtained from the treatment of Mesa soil. Figure 16 shows
the DRO degradation level for each remediation product applied in Mesa soil. After 83
days, levels of diesel contamination were still above the SRL enforced by ADEQ even
with treatments. Table 21 and Figure 17 show the results for Burro Creek soil, and Table
22 and Figure 18 show the results for Show Low soil.
41
Table 20: Mesa Soil Treated with Different Products.
Note: α = Mesa soil; D= Diesel; X=Micro-Blaze; Y= Hydro Clean; Z= Miracle-Gro.
Mg/kg=milligrams of contaminant contained in a kilogram of dry soil. *= Duplicate sample.
Figure 16: Mesa Soil Contaminated with Diesel.
Mesa-Diesel
Mesa-Diesel- Micro-Blaze
Mesa-Diesel-Hydro Clean
Mesa-Diesel-Miracle-Gro
ADEQ’s SRL during 2006
42
Table 21: Burro Creek Soil Treated with Different Products.
Note: β = Burro Creek soil; D= Diesel.; X=Micro-Blaze; Y= Hydro Clean;
Z= Miracle-Gro; RPD% = Relative Percent Difference; Mg/kg=milligrams of
contaminant contained in a kilogram of dry soil. *= Duplicate sample.
Figure 17: Burro Creek Soil Contaminated with Diesel.
Burro Creek-Diesel
Burro Creek-Diesel- Micro-
Blaze®
Burro Creek-Diesel-Hydro
Clean
Burro Creek-Diesel-Miracle-
Gro®
ADEQ’s SRL during 2006
43
Table 22: Show Low Soil Treated with Different Products.
Note: δ = Show Low soil; D =Diesel; X=Micro-Blaze; Y= Hydro Clean;
Z= Miracle-Gro; RPD% = Relative Percent Difference; Mg/kg=milligrams of
contaminant contained in a kilogram of dry soil. *= Duplicate sample; Area= Peaks
under C14-C22 Range.
Figure 18: Show Low Soil Contaminated with Diesel.
Show Low-Diesel
Show Low-Diesel- Micro-
Blaze
Show Low-Diesel-Hydro
Clean
Show Low-Diesel-Miracle-
Gro
ADEQ’s SRL during 2006
45
5.0 CONCLUSIONS
5.1 GASOLINE
All three soil types contaminated with gasoline showed a reduction in BTEX levels to
below ADEQ’s SRLs within 21 days, even in the absence of added microorganisms or
nutrients. However, in trying to compare the rates of degradation among various options,
some degree of quantification can be obtained by normalizing the BTEX concentration
and measuring the rate of decay.
Thus, the concentration of an individual contaminant at a given time is divided by the
initial concentration measurement, and the change in normalized concentration is then
divided by the number of days between measurements. The initial measurement of
BTEX was performed on day 2. For example, in Table 14, for αGW, the toluene
concentration on day 2 is 1352 mg/kg. Its normalized value is 1352/1352 = 1. The
concentration after day 7 is 322 mg/kg for a normalized value of 322/1352 = 0.238.
Thus, the initial rate of decay is
Rate = change in normalized concentration/change in time.
= (1 – 0.238)/ 5
= 0.152
After 14 days, the rate of decay is (1 – 0.044) / 12 = 0.080.
In Table 15, where no water was added, the rate of decay for toluene after seven days was
0.174. After 14 days, it was 0.082. Thus, the initial contaminant reduction rate for
toluene was slightly greater when no water was added, and the rates after 14 days were
similar.
Table 23 shows the normalized initial rates of decay for toluene, ethylbenzene, m- and p-xylene,
and o-xylene for all three soil types contaminated with gasoline without added
water and with added water (data from Tables 14 -18) from days 2 and 7.
Table 24 shows scores for each treatment method for each contaminant. The highest
normalized initial rate was assigned a score of 1, the next highest assigned a score of 2,
etc. The total for all components was then added for each soil type and treatment
method. The more effective treatment options correspond to lower total scores.
Table 25 arranges the total scores by soil type in order to compare the effectiveness of
treatment options.
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Table 23: Normalized Initial Rates (5 Days) of Decay
for Gasoline-Contaminated Soils.
Sample Toluene Ethylbenzene m- and p-
Xylene o-Xylene
αG 0.174 0.157 0.16 0.152
βG 0.187 0.162 0.163 0.159
δG 0.182 0.164 0.164 0.164
αGW 0.152 0.115 0.111 0.01
βGW 0.163 0.145 0.14 0.132
δGW 0.189 0.181 0.184 0.185
αGX 0.18 0.177 0.175 0.174
αGY 0.176 0.162 0.157 0.151
αGZ 0.197 0.185 0.189 0.189
βGX 0.171 0.149 0.145 0.139
βGY 0.168 0.148 0.142 0.138
βGZ 0.165 0.142 0.16 0.154
δGX 0.16 0.127 0.108 0.103
δGY 0.131 0.086 0.121 0.121
δGZ 0.176 0.156 0.152 0.146
Note: α = Mesa soil; β = Burro Creek soil; δ = Show Low soil; W = Water;
G = Gasoline; X = Micro-Blaze; Y = Hydro Clean; Z = Miracle-Gro.
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Table 24: BTEX Scores; Lower Scores Indicate Greater Effectiveness.
Sample Toluene Ethylbenzene m- and p-
Xylene o-Xylene Total
αG 8 7 6 7 28
βG 3 5 5 5 18
δG 4 4 4 4 16
αGW 13 14 14 15 56
βGW 11 11 12 12 46
δGW 2 2 2 2 8
αGX 5 3 3 3 14
αGY 6 5 8 8 27
αGZ 1 1 1 1 4
βGX 8 9 10 10 37
βGY 9 10 11 11 41
βGZ 10 12 6 6 34
δGX 12 13 15 14 54
δGY 14 15 13 13 55
δGZ 6 8 9 9 32
Note: α = Mesa soil; β = Burro Creek soil; δ = Show Low soil; W = Water; G = Gasoline;
X = Micro-Blaze; Y = Hydro Clean; Z = Miracle-Gro.
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Table 25: BTEX Scores According to Soil Type.
Sample Toluene Ethylbenzene m- and p-
Xylene o-Xylene Total
αG 8 7 6 7 28
αGW 13 14 14 15 56
αGX 5 3 3 3 14
αGY 6 5 8 8 27
αGZ 1 1 1 1 4
βG 3 5 5 5 18
βGW 11 11 12 12 46
βGX 8 9 10 10 37
βGY 9 10 11 11 41
βGZ 10 12 6 6 34
δG 4 4 4 4 16
βGW 11 11 12 12 46
δGX 12 13 15 14 54
δGY 14 15 13 13 55
δGZ 6 8 9 9 32
Note: α = Mesa soil; β = Burro Creek soil; δ = Show Low soil; W = water; G = Gasoline;
X = Micro-Blaze; Y = Hydro Clean; Z = Miracle-Gro.
Table 25 indicates that the most effective treatment for gasoline-contaminated Mesa soils
was to add Miracle-Gro (indicated by the letter Z). For Burro Creek and Show Low soils,
Miracle-Gro was the second most effective treatment, with the most effective being to
leave the soils alone without adding either water or other products. Micro-Blaze
treatment (letter X) was rated number 2, 3, or 4, while Hydro Clean (letter Y) was rated
number 3, 4, or 5 out of the five possible treatment options.
However, the most important observation is that all soil samples contaminated with
gasoline were below the residential Arizona SRLs by day 21, no matter what treatment
option was employed. There was some acceleration with certain treatments, but all
samples ultimately decayed to approximately the same levels of BTEX.
5.2 DIESEL
The situation with diesel-contaminated soils was quite different. In none of the sample
treatments was the diesel concentration below either residential or non-residential SRLs
by day 83. Normalized diesel scores according to soil type are shown in Table 26.
49
Table 26: Normalized Diesel Scores
According to Soil Type After 83 Days.
Sample Score Rank Order
αD (blank) 0.000732 3
αDX 0.00628 1
αDY 0.00423 2
αDZ -0.00508 4
βD (blank) 0.000136 3
βDX 0.000251 2
βDY 0.00330 1
βDZ -0.0032 4
δD (blank) 0.00177 2
δDX -0.0040 3
δDY 0.00614 1
δDZ -0.0085 4
Note: α = Mesa soil; β = Burro Creek soil; δ = Show Low soil; W = Water; D= Diesel;
X = Micro-Blaze; Y = Hydro Clean; Z = Miracle-Gro.
Normalized diesel scores were calculated in the same manner as scores for gasoline-contaminated
soils. For Burro Creek and Show Low soils, the optimal treatment was
with Hydro Clean, which was the second-best treatment option for Mesa soils. Micro-
Blaze was the optimal treatment for Mesa soils and the second-best for Burro Creek soils.
In all soils, treatment with Miracle-Gro resulted in an actual increase in measured DRO
after 83 days, as did treatment with Micro-Blaze in Show Low soils. This is likely due to
a division of long-chain organics into smaller fragments, which are still included in the
DRO sampling range.
51
6.0 RECOMMENDATIONS AND SUGGESTIONS
Even though the State of Arizona no longer has an SRL for total petroleum hydrocarbons,
it is prudent to take action to remediate. Cleaning up petrochemical hydrocarbons will
protect stormwater and surface water and eliminate environmental and public health
hazards.
Further research in the area of polycyclic aromatic hydrocarbons (PAHs) in soils from
diesel fuel spills and from incomplete combustion of carbon-containing fuels should be
considered.
The research was performed in a laboratory situation. The rate at which volatile organic
compounds (VOCs) decayed was in days as opposed to weeks, although decay would
have taken weeks if research had occurred in situ. Changes in research design should be
considered to include in situ application of remediation products.
The increase in DRO may be a result of larger-chain hydrocarbons being broken down to
smaller chains, causing DRO numbers to increase. Further research with GC/MS may be
useful to confirm the breakdown of DRO into smaller hydrocarbon chains.
It is also prudent to consider further evaluation of other dispersants, chemicals, and oil
spill mitigating devices and substances listed on the EPA National Contingency Plan
Subpart J Product Schedule. Research associated with the control of oil from rubberized
asphalt and other asphaltic materials is a related area that warrants further investigation.
53
7.0 REFERENCES
Arizona Department of Health Services. (1998). C10-C32 Hydrocarbons in Soil – Method
8015AZ, Revision 1.0, September 25. Available at
http://www.azdhs.gov/lab/license/tech/8015azr1.pdf.
Hristovski, K., P. Westerhoff, T. Moller, P. Sylvester, W. Condit, and H. Mash. (2008).
Simultaneous Removal of Perchlorate and Arsenate by Ion-Exchange Media
Modified with Nanostructured Iron (Hydr)Oxide. Journal of Hazardous
Materials, 152(1): 397- 406. doi:10.1016/j.jhazmat.2007.07.016
Micro-Blaze®. (2008). Micro-Blaze. Retrieved April 3, 2008, from
http://www.microblaze.com/faqs_mb_prods.htm
Miracle-Gro®. (2008). Miracle-Gro. Retrieved April 5, 2008, from
http://www.scotts.com/smg/catalog/productCategorySubSelf.jsp?navAction=jump
&itemId=cat70048&id=cat50006.
Sontheimer, H., J.C. Crittenden, and R.S. Summers. (1988). Activated Carbon for Water
Treatment (Engler-Bunter-Institu Trans.). (Second ed.). Karlsruhe, Germany:
DVGWForschungsstelle.
United States Agriculture Department. (2008). Natural Resources Conservation Service.
Retrieved June 5, 2008, from http://www.az.nrcs.usda.gov/technical/soils/.
Wilke, B. (2005). Determination of Chemical and Physical Soil Properties. In R.
Margesin & F. Schinner (Eds.), (pp. 47-93). Heidelberg, Germany: Springer.