Assessment of Hydrocarbon Carryover 

Potential for Six Field Cleaning Protocols

NOAA National Centers for Coastal Ocean Science

Stressor Detection and Impacts Division

Emily C. Pisarski, Edward F. Wirth, S. Ian Hartwell, Brian S. Shaddrix,

David R. Whitall, Dennis A. Apeti, Michael H. Fulton

NOAA Office of Response and Restoration

Assessment and Restoration Division

Greg Baker

May 2018

NOAA Technical Memorandum NOS NCCOS 247

NOAA NCCOS Stressor Detection and Impacts Division
Acknowledgments

The authors would like to thank Sarah Allan (NOAA/NOS/ORR), Len Balthis (NOAA/NOS/NCCOS), 

and Paul Pennington (NOAA/NOS/NCCOS) for their helpful reviews. Cover photographs were provided 

by Ian Hartwell and Emily Pisarski, photographs throughout the document were provided by Ian Hartwell 

and Ed Wirth.

Citation

Pisarski, E.C., E.F. Wirth, S.I. Hartwell, B.S. Shaddrix, D.R. Whitall, D.A. Apeti, M.H. Fulton, G. Baker. 

2018. Assessment of Hydrocarbon Carryover Potential for Six Field Cleaning Protocols. NOAA 

Technical Memorandum NOS NCCOS 247. Silver Spring, MD. 36 pp.

Disclaimer: 

The scientific results and conclusions, as well as any opinions expressed herein, are those of the author(s) 

and do not necessarily reflect the views of NOAA or the Department of Commerce. The mention of any 

commercial product is not meant as an endorsement by the Agency or Department.

ii
Assessment of Hydrocarbon Carryover Potential for Six Field Cleaning 

Protocols 

Prepared by:

NOAA’s National Centers for Coastal Ocean Science and Office of Response and Restoration

NOAA Technical Memorandum NOS NCCOS 247

Authors:

Emily C. Pisarski1

, Edward F. Wirth2, S. Ian Hartwell3, Brian S. Shaddrix1, David R. Whitall3, 

Dennis A. Apeti3

, Michael H. Fulton2, Greg Baker4

1 NOAA/NOS/National Centers for Coastal Ocean Science/JHT Inc., Stressor Detection and 

Impacts Division, Charleston, SC

2 NOAA/NOS/National Centers for Coastal Ocean Science, Stressor Detection and Impacts 

Division, Charleston, SC

3 NOAA/NOS/National Centers for Coastal Ocean Science, Stressor Detection and Impacts 

Division, Silver Spring, MD

4 NOAA/NOS/Office of Response and Restoration, Assessment and Restoration Division, CA

United States Department 

of Commerce

Wilbur Ross

Secretary

National Oceanic and Atmospheric 

Administration

RDML Tim Gallaudet, Ph.D. USN 

Ret. Assistant Secretary of Commerce 

and Acting Under Secretary

Secretary of Commerce for 

Oceans and Atmosphere 

National Ocean Service

Russell Callender, Ph.D.

Assistant Administrator

iii
Table of Contents

List of Figures v

List of Tables vi

Executive Summary 2

Introduction 3

Materials and Methods 4

Sediment Collection 4

Site Water 4

Sampling and Decontamination Materials 4

Sediment Grain Size Analysis/Total Organic Carbon Determination 4

Sediment Spiking 4

Assessment of Cleaning Protocol Carryover Potential 5

Measurement of Hydrocarbons in Cleaning Protocol Rinses 5

Measurement of Hydrocarbons in Sediment 5

Measurement of Hydrocarbons in Seawater and Solvents 5

Instrumental Analysis 6

Method Detection Limits and Blank Correction 7

Statistical Analysis and Units of Measurement 8

Results and Discussion 9

Grain Size and Total Organic Carbon Analysis 9

Hydrocarbons in Seawater and Solvent 9

Hydrocarbons in Process Blanks 10

Hydrocarbons in Spiked Sediment 11

Residual Hydrocarbons from Cleaning Protocols 11

Silt versus Sand Sediment Comparison 14

Protocol Comparisons (using pooled sediment data) 14

Protocol Comparisons (within sediment types) 15

Conclusions 22

Literature Cited 23

Supplemental Information 25

iv
List of Figures

Figure 1: Percent residual PAH50 plotted for each sediment type 16

Figure 2A-D: Photos taken during the cleaning protocol process 17

Figure 3: Photo of the site water rinse process during a sand replicate 18

Figure 4: Average PAH50 profiles for both the sand and silt spiked sediments 19

Figure 5A-B: The average proportional residual PAH profile after each cleaning protocol 21

Supplemental Figure 1: Equation for calculating individual PAH MDLs 25

Supplemental Figure 2: PAH analyte proportions for each cleaning protocol blank 27

Supplemental Figure 3: PAH 50 profile for PAHs measured in the solvent, seawater and cleaning 

protocol blanks 28

v
List of Tables

Table 1: Cleaning protocols tested in this study 3

Table 2: Parent and alkylated PAHs that comprise PAH50 7

Table 3: Measured TEH and PAH50 from Charleston Harbor seawater and extraction solvents 10

Table 4: Measured TEH and PAH50 for the blanks associated with each cleaning protocol 11

Table 5: TEH and PAH50 concentrations from spiked sediments 11

Table 6: Measured TEH and PAH50 from each bowl/spoon after each cleaning protocol 13

Table 7: T-test results for silt versus sand sediment comparison within each protocol 14

Table 8: Results of Tukey-Kramer pairwise (PAH50) and Dunn All Pairs for Joint Ranks (TEH) 

for comparisons among cleaning protocols using pooled sediment types 15

Table 9: Results of Tukey-Kramer pairwise comparisons among cleaning protocols using sand 

sediment type only 15

Supplemental Table 1: Grain-size analysis and Particle (Φ) Distribution 29

vi
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1
Executive Summary

Executive Summary

Sample collection in the field faces many challenges including, but not limited to, the 

equipment and materials that can be brought safely into the field. Field teams will often reuse 

sample collection gear by cleaning it between sampling sites to prevent cross-contamination. 

Decontamination protocols for equipment used to collect samples for organic contaminant 

analysis range from a simple water rinse with scrub brush application to more involved measures 

that include soap and/or the use of various organic solvents. The efficacy of six different field 

cleaning protocols for sediment sampling tools was evaluated in a controlled laboratory setting 

using two different sediments (predominantly sand and silt) that were dosed with weathered 

Deepwater Horizon oil (i.e. “Slick B oil”; collected from surface slicks on June 19, 2010). 

Percent (%) residual total extractable hydrocarbons (TEH) and percent residual polycyclic 

aromatic hydrocarbons (PAH) were measured to evaluate the relative effectiveness of the various 

protocols in removing oiled sediment from the stainless steel materials. Cleaning protocols 

encompass scenarios where decontamination is limited by resources, supplies, and time, as well 

as scenarios where resources, supplies, and time are not a factor. 

Key findings from this study include:

•	 The measured % residual TEH and PAH values from all protocols in this study were 

within the range of values that would be indistinguishable from expected sampling, 

laboratory, or instrumental variability; thus, regardless of decontamination protocol, all 

were effective at hydrocarbon removal.

•	 Cleaning protocols that used organic solvents as a step had less % residual TEH and % 

residual PAH than protocols that didn’t use solvent as a step.

•	 The highest % residual TEH and % residual PAH value (0.032% and 0.029% 

respectively) were obtained from the cleaning protocol that only used site water and a 

scrub brush.

2
Introduction

Introduction 

Collecting samples in the field for chemical analysis can be challenging. Sampling efforts 

are often limited by both the amount of material and equipment (i.e., sampling gear) that can 

be carried in the field as well as the types of supplies (i.e., soap, solvents) that can be safely 

transported, handled, and disposed. For example, field teams may not always be able to carry 

and use solvents safely in the field. With these limitations, field efforts often include sample 

collection gear that is used multiple times and cleaned (decontaminated) between stations to 

avoid cross-contamination of samples. Various multi-step field cleaning protocols have been 

developed and some include the use of organic solvents. It is, therefore, important to understand 

the risks and benefits of the different cleaning practices.

The National Centers for Coastal Ocean Science (NCCOS), in collaboration with the 

Office of Response and Restoration (OR&R), developed a testing design to determine if there 

are measurable chemical residues, related to environmental oiling, in sampling equipment 

following decontamination. The test design assessed chemical carryover between sediment 

samples, collected with sampling gear that has been cleaned following several conventional 

protocols. Six different cleaning protocols were tested (Table 1) on two different sediment types 

(one predominantly fine silt and the other primarily sand) that were spiked with Slick B oil (a 

weathered form of Louisiana Sweet Crude oil collected in large quantities from surface slicks 

on July 19, 2010 during the Deepwater Horizon Oil Spill event). Chemical analyses for total 

extractable hydrocarbons (TEH) and polycyclic aromatic hydrocarbons (PAHs) were performed 

to determine residual hydrocarbon contaminants.

Table 1: Cleaning protocols tested in this study. 

Cleaning 

Protocol 

(CP) 

Cleaning Protocol Protocol Designation

CP1 site water and brush minimal decontamination (limited resources, 

supplies, time)

CP2 site water/soap and brush/site 

water/deionized (DI) water

more rigorous than CP1, for times when 

solvent is not available or prohibited in the 

field

CP3 site water and brush/site water/

acetone/DI water NCCOS protocol (Apeti et al., 2012)

CP4 site water/soap and brush/site 

water/acetone/hexane/air dry OR&R protocol (Bejarano et al., 2014)

CP5 site water and brush/isopropyl 

alcohol wipe/DI water EPA protocol (Fisher et al., 2004)

CP6

site water/soap and brush/site 

water/isopropyl alcohol wipe/DI 

water

EPA protocol (Fisher et al., 2004)

3
Materials and Methods

Materials and Methods

Sediment Collection 

Two different sediment types were collected from estuarine locations in Charleston, SC 

that have been previously determined to contain low or non-detectable levels of hydrocarbons. 

Folly River sediment (N32.63898; W-79.98767) is predominantly sand and has been used 

extensively as a reference sediment for bivalve toxicity testing (Chung, 1999; Key et al., 2007). 

Leadenwah Creek sediment (N32.6475; W-80.22168) is predominantly silt and serves as a field 

reference site for crustacean toxicological research (Scott et al., 1999). 

Site Water

Seawater, which was used as “site water” for the cleaning protocols, was obtained from 

the Charleston Harbor, Charleston, SC. Seawater was allowed to settle for at least 72 hr and 

mechanically filtered to 25 μm (sand filter). Additional mechanical filtration to 10 μm (cartridge 

filtration) was followed by exposure to a 150W UV sterilizer to limit bacterial growth prior to 

experimental testing. 

Sampling and Decontamination Materials

Stainless steel bowls (4 quart) and 11-inch stainless steel spoons were purchased from 

Seva Technical Services, Inc. Twelve-inch natural bristle brushes were obtained from Coronado 

Distribution Company, Inc. Brushes, bowls, and spoons were reused throughout the study across 

the six cleaning protocols so extra care was taken to eliminate cross-contamination between 

protocols. After completing each decontamination protocol, standard operating procedures for 

thorough decontamination of laboratory equipment were followed: all brushes were sonicated in 

Liquinox® soap (Alconox, Inc.) and water for 30 min, rinsed with hot tap water and deionized 

(DI) water, air-dried overnight, then solvent rinsed with methanol prior to reuse. Spoons were 

treated in the same manner, except that they were solvent rinsed with acetone, dichloromethane, 

and hexane following soap and water sonication. Bowls were scrubbed and washed by 

hand with Liquinox soap, hot tap water, and DI water, and then solvent rinsed with acetone, 

dichloromethane, and hexane.

Solvents used for this project were obtained from VWR (Burdick and Jackson 

dichloromethane and acetone) or Fisher Scientific (n-hexane and methanol). All solvents used 

were of high purity (≥99.9% purity), suitable for HPLC and GC analysis. Isopropyl alcohol 

wipes were manufactured by Techspray and contained 99.8% pure isopropyl alcohol. Liquinox 

soap was used for any cleaning protocol that required soap. 

Sediment Grain Size Analysis/Total Organic Carbon Determination

Grain size analysis relating to silt-clay determination was performed according to 

methods by Plumb (1981). Grain size distribution determination followed methods from Folk 

(1974), Lewis (1984), and Lewis and McConchie (1994). Total organic carbon (TOC) analysis 

was performed using the methods of Heiri et al. (2001). 

Sediment Spiking

Roughly 10 L of sediment was collected from each site and stored at 4°C for 14 days. 

Prior to spiking with Slick B oil, each portion of sediment was well mixed by hand using a 

solvent-cleaned spoon for 10-15 minutes. Approximately 3700 g of wet sediment was weighed 

4
Materials and Methods

into 4-L pre-cleaned glass jars and spiked with Slick B for an expected nominal concentration 

of 10,000 mg Slick B/kg wet sediment. This mass of sediment was selected so that there 

was ample sediment available to aliquot into multiple replicates for each cleaning protocol. 

The nominal concentration of 10,000 mg Slick B/kg wet sediment was selected to represent a 

reasonable worst-case field scenario for encountering oil-contamination in soil and sediment, 

based on a summary review of PAH50 concentrations in thousands of such samples collected 

during the Deepwater Horizon oil spill natural resource damage assessment (Rouhani et al 2016). 

Calculated nominal wet mass concentrations were 9,930 and 10,230 mg Slick B/kg wet sediment 

for Folly River (sand) and Leadenwah Creek (silt) sediment respectively. After spiking, each jar 

was rolled on a mechanical jar roller for at least 8 hours. After spiking and mixing, the sediment 

was stored in the dark at 4°C. 

Assessment of Cleaning Protocol Carryover Potential

To assess the potential carryover associated with each cleaning protocol, the glass jars 

of spiked sediment were retrieved from storage, allowed to come to room temperature, and 

homogenized by a mechanical roller for one hour. For each sample replicate, roughly 500 g of 

sediment was placed into a stainless steel bowl and stirred with a stainless steel spoon for ~ 30 

seconds. The sediment was then scooped by spoon from the bowl after which the bowl and spoon 

were cleaned according to each designated protocol. For any given protocol, both sediment types 

were tested (three replicates per sediment type). After the cleaning protocol was completed for 

each replicate, the bowl was rinsed with approximately 50 mL of dichloromethane and 50 mL of 

hexane and the spoon was rinsed with approximately 25 mL of dichloromethane and 25 mL of 

hexane in order to collect and measure any hydrocarbon residues remaining after the completed 

cleaning protocol. For each replicate, the solvents used to rinse the bowl and spoon were 

collected into pre-cleaned 500-mL wide-mouth amber bottles.

Measurement of Hydrocarbons in Cleaning Protocol Rinses

The composited dichloromethane and hexane rinses were spiked with isotopically labeled 

PAH and TEH internal standards (Cambridge Isotope Laboratories), treated with anhydrous 

sodium sulfate for water removal, concentrated, and processed through silica solid phase 

extraction (SPE) prior to instrumental analysis on GC/MS. 

Measurement of Hydrocarbons in Sediment

Three 10-g aliquots of each sediment type were assessed for PAHs and TEH. Sediment 

aliquots were extracted using methods adapted from Kucklick et al. (1997), Long et al. (1998), 

and Balthis et al. (2012). Briefly, sediment was placed into a glass mortar bowl containing 

anhydrous sodium sulfate to dry the sediment. The sediment and sodium sulfate mixture 

was transferred to a stainless steel Accelerated Solvent Extraction (ASE) cell, spiked with 

isotopically labeled PAH and TEH internal standards, and extracted with a mixture of 1:1 

dichloromethane:acetone using an ASE 200 system (Dionex). Afterwards the extract was treated 

with activated copper wool for sulfur removal and passed through additional sodium sulfate for 

residual water removal. Final extract cleanup steps included gel permeation chromatography 

(GPC) followed by silica SPE. 

Measurement of Hydrocarbons in Seawater and Solvents

The seawater used during the testing, along with the solvents (hexane and 

dichloromethane) used to rinse the bowl and spoon after each cleaning protocol, were assessed 

5
Materials and Methods

for their potential contribution of hydrocarbons. Three replicates of seawater (each 1 L) were 

extracted using liquid/liquid extraction. Each seawater sample was sequentially extracted using 

dichloromethane (60 mL), 1:1 dichloromethane:hexane (60 mL), and hexane (60 mL). In total, 

180 mL of solvent was used to extract the seawater. Seawater solvent extracts were combined, 

then processed through sodium sulfate to remove residual water, concentrated, and cleanedup with silica SPE. To determine hydrocarbons related to the solvent and/or concentration 

process, three 150-mL replicates of 1:1 dichloromethane:hexane were concentrated in a water 

bath (40°C) under nitrogen (N2

), and then passed through silica SPE. Solvent (150 mL of 1:1 

dichloromethane:hexane) was also concentrated using a water bath only (no N2

) to determine 

residual hydrocarbons solely related to the solvent. 

Instrumental Analysis

Extracts from all chemical analyses were analyzed using an Agilent GC/MS (6890/5973, 

electron impact configuration) operated in selected ion monitoring mode, containing a split/

splitless injector and DB17ms analytical column (Agilent J&W 60 m x 0.25 mm x 0.25 μm). The 

instrument was calibrated with calibration standards ranging from 0.1-5000 ng (PAHs) and 0.25-

20 mg (TEH). The TEH calibration curve was made by diluting Slick B material and extracting 

the calibration levels through silica SPE prior to instrumental analysis. Continuing calibration 

verification standards were run every 10-15 samples to ensure the validity of the calibration 

curve. All analytes had a coefficient of determination (r2

) greater than or equal to 0.995. Data 

analysis was performed using MSD Chemstation software. Total PAH (PAH50) is reported for 50 

parent and alkylated PAHs (Table 2).

6
Materials and Methods

Table 2: Parent and alkylated PAHs that comprise PAH50.

Parent PAHs in PAH50 Alkylated PAHs in PAH50

naphthalene C1-naphthalenes

biphenyl C2-naphthalenes

acenaphthene C3-naphthalenes

acenaphthylene C4-naphthalenes

fluorene C1-fluorenes

dibenzofuran C2-fluorenes

dibenzothiophene C3-fluorenes

phenanthrene C1-dibenzothiophenes

anthracene C2-dibenzothiophenes

fluoranthene C3-dibenzothiophenes

pyrene C4-dibenzothiophenes

benz(a)anthracene C1-phenanthrenes/anthracenes

benzo(b)naphtho(2,1-d)thiophene C2-phenanthrenes/anthracenes

chrysene + triphenylene C3-phenanthrenes/anthracenes

benzo(a)fluoranthene C4-phenanthrenes/anthracenes

benzo(b)fluoranthene C1-fluoranthenes/pyrenes

benzo(j)fluoranthene C2-fluoranthenes/pyrenes

benzo(k)fluoranthene C3-fluoranthenes/pyrenes

benzo(a)pyrene C4-fluoranthenes/pyrenes

benzo(e)pyrene C1-chrysenes/benzanthracenes

dibenzo(a,h)anthracene C2-chrysenes/benzanthracenes

indeno(1,2,3-c,d)pyrene C3-chrysenes/benzanthracenes

benzo(g,h,i)perylene C4-chrysenes/benzanthracenes

C1-naphthobenzothiophenes

C2-naphthobenzothiophenes

C3-naphthobenzothiophenes

C4-naphthobenzothiophenes

Method Detection Limits and Blank Correction

Method detection limits (MDLs) for TEH were calculated by using the lowest calibration 

point (0.25 mg) and dividing that by the mass or volume of sample in the extract. The MDLs 

for PAHs were calculated according to Ragland et al. (2014). Briefly, the minimum detectable 

peak area (MDPA) of any given analyte was estimated using procedural blanks by taking into 

account instrument sensitivity, as well as extraction efficiency, relating to both the process and 

analyst (Ragland et al., 2014). The general equation for calculating the PAH MDLs can be found 

in Supplemental Figure 1. The procedural blanks used for calculating the MDLs were obtained 

from the solvent (with N2 concentration) extracts.

7
Materials and Methods

For each cleaning protocol, a blank (a spoon and bowl, without any sediment) was 

processed using the same cleaning protocol as the bowls and spoons that contained sediment. 

These process blanks were used to understand if and how the cleaning protocol itself contributed 

to possible PAH/TEH concentrations. Process blanks were run at the end of each cleaning 

protocol. Any measured PAHs found in a given process blank were subtracted from measured 

PAHs observed in replicate samples from the same cleaning protocol.

Statistical Analysis and Units of Measurement

All statistical analyses were performed using JMP version 12.1.0. All datasets were tested 

for normality prior to statistical analyses. If a dataset had a p-value greater than 0.05, it passed 

the test for normality, whereas datasets with a p-value less than or equal to 0.05 failed the test 

for normality. For datasets with normal distributions, the Student’s t-test or a one-way analysis 

of variance (ANOVA) with a Tukey-Kramer pairwise comparison (when applicable) was used to 

examine differences between treatments. For datasets with non-normal distributions, equivalent 

non-parametric statistical analyses (Wilcoxon test or Kruskal-Wallis test with the Dunn Method 

for joint ranking) were used.

Due to large differences in scale between TEH and PAH50, TEH is reported in units of 

mg, mg/kg, mg/L or ppm while PAH50 is reported in units of ng, ng/g, ng/mL, or ppb.

8
Results and Discussion

Results and Discussion

Grain Size and Total Organic Carbon Analysis

The quantified grain size and TOC confirmed that the two sediment sampling locations 

represented two different sediment types. In this study, having different sediment types was 

important in understanding how factors such as grain size and/or TOC may influence potential 

routes of cross-contamination. Generally, organic contaminants with a high log Kow tend to 

preferentially bind to silt/clay based sediments, which typically have higher TOCs. Sediment 

from the Folly River was predominantly sand (93.8%; Supplemental Table 1) while the 

Leadenwah Creek sediment was 48.8% sand (Supplemental Table 1). Percent TOC for Folly 

River and Leadenwah Creek was measured as 1.27±0.04% and 7.92±0.05%, respectively. 

Hydrocarbons in Seawater and Solvent

 Results for the seawater and solvent replicates are shown in Table 3. In both seawater 

and solvent (with and without N2

 concentration) TEH was below the method detection limit 

(0.0003-0.0017 mg/mL). There were measurable PAHs in both seawater and N2

 concentrated 

solvent. There were no PAHs detected in the solvent where N2

 concentration was not used. 

PAH50 for the seawater and N2

 concentrated solvent was normalized to the volume of solvent 

used and compared using a t-test. There was no significant difference between the seawater and 

N2

 concentrated solvent PAH50 residues (p=0.0862) when normalized to solvent volume. This 

suggests that measured PAHs were more likely related to the extraction process (i.e., N2

 gas 

concentration step) rather than the seawater and/or solvent.

Naphthalene, 1-methylnaphthalene, and 2-methylnapthalene accounted for 90-95% of 

PAHs that were measured in both seawater and N2

 concentrated solvent (Supplemental Figure 3). 

These PAHs are some of the more volatile PAHs and appear to be related to the N2

 gas that was 

used during the concentration steps in the extraction/clean-up process. It should also be noted 

that extraction solvent volume, which dictates concentration time, appears to affect detected 

PAH masses. In Table 3, it was observed that the average PAH50 mass for seawater was 102 ng 

and for solvent alone was 67.1 ng. Corresponding extraction solvent volumes were 200 and 150 

mL respectively. Thus, it can be inferred that larger solvent volumes, which require longer N2

evaporation time, lead to higher detected hydrocarbon masses. These analytes at these reported 

concentrations are typical for our laboratory processes. Efforts were made to limit hydrocarbon 

contamination by using an in-line filter designed to remove hydrocarbons on the nitrogen gas 

line. Despite this effort, hydrocarbon contamination was observed and therefore measured PAHs 

in the solvent were factored into the calculated method detection limits (MDL).

9
Results and Discussion

Table 3: Measured TEH and PAH50 from Charleston Harbor seawater and extraction solvents (with and 

without N2 concentration). PAH50 measurements are given in mass of PAHs measured (which does not 

take extraction volume nor solvent volume used into account), PAH50 concentration based on the amount 

of seawater extracted (only applicable to seawater samples), and PAH50 concentration based on the 

volume of solvent used. 

TEH (mg) PAH50 (ng)

PAH50 conc. 

based on water 

vol. (ng/mL)

PAH50 conc. 

based on solvent 

vol. (ng/mL)

Seawater 1 0.00 93.4 0.0934 0.467

Seawater 2 0.00 114 0.114 0.570

Seawater 3 0.00 99.4 0.0994 0.497

Average

(Std. Dev)

--

--

102

(10.6)

0.102

(0.011)

0.511

(0.053)

Solvent with N2

 1 0.00 56.9 -- 0.379

Solvent with N2

 2 0.00 67.8 -- 0.452

Solvent with N2

 3 0.00 66.4 -- 0.443

Average

(Std. Dev)

--

--

67.1

(0.99)

--

--

0.425

(0.040)

Solvent (no N2

) 1 0.00 0.00 -- 0.00

Solvent (no N2

) 2 0.00 0.00 -- 0.00

Solvent (no N2

) 3 0.00 0.00 -- 0.00

Hydrocarbons in Process Blanks

The measured TEH and PAH50 values from the process (i.e., cleaning protocol) blanks 

are shown in Table 4. Measured TEH was below the detection limit for all cleaning protocols 

except for CP5. Measured PAH50 concentration based on solvent volume for the process blanks 

(Table 4), N2 concentrated solvent, and seawater (Table 3) were compared using an ANOVA. 

A significant difference was observed among treatments (p=0.0277) and a Tukey-Kramer 

pairwise comparison revealed that PAH50 concentrations in the blank were greater than PAH50 

concentrations in the solvent (p=0.0346). There was no significant difference between the process 

blanks and seawater (p=0.1107). Naphthalene, 1-methylnaphthalene and 2-methylnapthalene 

account for 61-83% of PAHs that were measured in the process blanks (Supplemental Figures 

2A-B, 3). Observationally, there were decreases in the proportions of the naphthalenes between 

the solvent/seawater and the cleaning protocol blanks which may indicate that the measured 

PAHs are not solely related to the laboratory extraction/cleanup process (i.e., nitrogen gas) but 

that there is also a minor contribution from the cleaning protocol. In protocols where soap and 

water were required, only one soap and water bath was made and used throughout that cleaning 

protocol, which may be a potential source of cross-contamination in samples and ultimately the 

blanks. The decision was made to use the measured PAHs from the process blanks to correct 

samples from the corresponding cleaning protocol. Measured values for any detected PAH 

analyte found in the blanks were subtracted from the associated PAHs in the individual replicates 

for a given cleaning protocol. This correction was made in order to account for hydrocarbon 

contributions occurring from the extraction process as well as from the soap and water bath. 

10
Results and Discussion

Table 4: Measured TEH and PAH50 for the blanks associated with each cleaning protocol.

Cleaning Protocol TEH (mg) PAH50 (ng)

PAH50 conc. 

based on solvent 

volume (ng/mL)

CP1 <MDL 127 0.747

CP2 <MDL 150 0.882

CP3 <MDL 102 0.600

CP4 <MDL 141 0.829

CP5 0.32 187 1.10

CP6 <MDL 83.4 0.491

Hydrocarbons in Spiked Sediment

Measured TEH and PAH50 for the spiked sediment are found in Table 5. The targeted 

Slick B whole oil concentration in the sediment was 10,000 mg/kg wet. Average measured 

TEH in the spiked sand (Folly) was 8930±780 mg/kg wet and in the spiked silt (Leadenwah) 

was 9350±1470 mg/kg wet. On a dry mass basis TEH was 12600±1100 and 24500±3900 mg/

kg respectively. Average PAH50 was 27600±1150 and 28600±5410 ng/g wet for the sand and 

silt sediments respectively (on a dry mass basis PAH50 was 38800±1620 and 75000±14200 

ng/g respectively). On average, PAH50 accounted for 0.31±0.012% of the total extractable 

hydrocarbons in Slick B.

Table 5: TEH and PAH50 concentrations from spiked sediments.

Sediment 

Type 

(Dry Fraction)

Replicate

TEH

mg/kg wet 

(ppm)

TEH 

mg/kg dry 

(ppm)

PAH50 

ng/g wet 

(ppb)

PAH50 

ng/g dry 

(ppb)

Folly River - 

Sand

(0.711)

1 9670 13600 28800 40500

2 8120 11400 26500 37200

3 8990 12600 27500 38700

Average 

(std. dev.)

8930

(780)

12600

(1100)

27600

(1150)

38800

(1620)

Leadenwah 

Creek - Silt

(0.382)

1 10500 27600 33500 87800

2 9820 25700 29600 77500

3 7700 20200 22800 59800

Average 

(std. dev.)

9350

(1470)

24500

(3900)

28600

(5410)

75000

(14200)

Residual Hydrocarbons from Cleaning Protocols

Measured TEH and PAH50 values for each cleaning protocol are found in Table 6. To 

understand the percentage of TEH and PAH50 that remained in the bowl after the cleaning 

11
Results and Discussion

protocol, the percent (%) residual TEH and % residual PAH50 were calculated. These values 

were calculated by taking the average TEH and PAH50 wet concentrations for each sediment 

type (Table 5) and multiplying that by the amount of sediment that was placed in each bowl; this 

value is the total TEH and PAH50 that was transferred into each bowl. The TEH (or PAH50) 

residue that was measured after the cleaning process was then divided by the total TEH (or 

PAH50) and multiplied by 100 to obtain the % residual TEH (or % residual PAH50) for any 

given replicate in any given cleaning protocol. The % residual TEH and PAH50 generally agreed 

with each other which indicates that the designated cleaning protocol did not preferentially 

remove aliphatic hydrocarbons (TEH) over aromatic hydrocarbons (PAH50) or vice versa. 

The highest percentage of residual TEH and PAH50 was observed in CP1, silt sediment, 

replicate 3. Residual TEH and PAH50 for this sample was 0.032% and 0.029% respectively. 

Within many of the protocols, TEH was less than the detection limit. The lowest recorded % 

residual PAH50 was observed in CP 4, with 0.0001% residual PAH50. Generally the mass of 

residual hydrocarbons remaining on the equipment after cleaning was near or below 0.01% 

(i.e., 0.0001 as a fraction) of the hydrocarbons in the sample material. Thus if reusing the 

cleaned sampling equipment for a subsequent collection of a sample having similar hydrocarbon 

contamination, the most additional hydrocarbon contamination the cleaned equipment 

theoretically could contribute to the new sample is on the order of 0.01%, a negligible difference 

given the other variability in field sampling and laboratory analysis. Even if the subsequent 

sample is far less contaminated (e.g., contains two orders of magnitude less TEH or PAH50), 

the most contamination that could be contributed by the decontaminated equipment would only 

increase the hydrocarbon concentration in the sample by 1%. It is also important to note that 

this assumes that all of the residual hydrocarbons would be transferred into the next sample; in 

a real world scenario this would be highly unlikely. For example, when using a grab sampler, it 

is common practice to scoop sediment only from the interior of the grab (i.e., sediment that does 

not touch the sampler itself) thus the potential for residual hydrocarbon contamination in Table 6 

may be overestimated.

12
Results and Discussion

Table 6: Measured TEH and PAH50 from each bowl/spoon after each cleaning protocol. The % residual TEH and % 

residual PAH were calculated by multiplying the average TEH (or PAH50) concentration (Table 5) by the amount 

of sediment placed into each bowl to obtain an estimate of the total TEH (or PAH50) for any given treatment. 

The measured TEH (or PAH50) measured after each cleaning protocol replicate was divided by the total TEH (or 

PAH50) and multiplied by 100 to determine % residual TEH (or PAH50).

Cleaning Protocol Sediment Type TEH (mg) PAH50 (ng) % Residual TEH % Residual PAH50

CP1-site water and 

brush 

Sand

1.01 2550 0.020 0.017

0.760 1930 0.015 0.013

0.810 1910 0.018 0.013

Average (Std. Deviation) 0.860 (0.132) 2130 (363) 0.018 (0.003) 0.014 (0.002)

Silt

0.500 1240 0.011 0.009

0.810 1210 0.017 0.008

1.53 4220 0.032 0.029

Average (Std. Deviation) 0.947 (0.528) 2220 (172) 0.02 (0.010) 0.015 (0.011)

CP2-site water/

soap and brush/site 

water/DI 

Sand

0.290 716 0.006 0.005

0.760 978 0.017 0.007

0.760 1600 0.017 0.013

Average (Std. Deviation) 0.603 (0.271) 1098 (454) 0.013 (0.006) 0.008 (0.004)

Silt

0.270 797 0.006 0.005

0.000 514 0.000 0.004

0.000 342 0.000 0.002

Average (Std. Deviation) 0.090 (0.156) 551 (230) 0.002 (0.003) 0.004 (0.002)

CP3-site water and 

brush/site water/

acetone/DI 

Sand

0.000 74.1 0.000 0.0005

0.680 249 0.015 0.002

0.000 123 0.000 0.0009

Average (Std. Deviation) 0.227 (0.392) 149 (90) 0.005 (0.008) 0.001 (0.001)

Silt

0.620 749 0.013 0.005

0.310 103 0.006 0.0007

0.000 159 0.000 0.001

Average (Std. Deviation) 0.31 (0.31) 337 (358) 0.006 (0.006) 0.002 (0.002)

CP4-site water/

soap and brush/

site water/acetone/ 

hexane/air dry

Sand

0.000 16.0 0.000 0.0001

0.000 29.2 0.000 0.0002

0.000 73.1 0.000 0.0005

0.000 (0.000) 39.4 (29.8) 0.000 (0.000) 0.0003 (0.0002)

Silt

0.000 20.2 0.000 0.0001

0.820 894 0.017 0.006

0.330 331 0.007 0.002

Average (Std. Deviation) 0.383 (0.412) 415 (443) 0.008 (0.008) 0.003 (0.003)

CP5-site water and 

brush/IPA wipe/DI 

Sand

0.000 223 0.000 0.002

0.000 115 0.000 0.0008

0.000 256 0.000 0.002

Average (Std. Deviation) 0.000 (0.000) 198 (744) 0.000 (0.000) 0.002 (0.001)

Silt

0.000 219 0.000 0.002

0.340 695 0.007 0.005

0.560 496 0.012 0.003

Average (Std. Deviation) 0.300 (0.282) 470 (239) 0.006 (0.006) 0.003 (0.001)

CP6-site water/

soap and brush/site 

water/IPA wipe/DI 

Sand

0.000 48.8 0.000 0.0003

0.000 31.2 0.000 0.0002

0.000 66.9 0.000 0.0005

Average (Std. Deviation) 0.000 (0.000) 49.0 (18) 0.000 (0.000) 0.0003 (0.0002)

Silt

0.000 77.1 0.000 0.0005

0.280 254 0.006 0.002

0.330 328 0.007 0.002

Average (Std. Deviation) 0.203 (0.177) 220 (128) 0.004 (0.003) 0.002 (0.001)

13
Results and Discussion

Silt versus Sand Sediment Comparison

To understand if there is a difference between % residual TEH or PAH50 carryover based 

on sediment type within any given cleaning protocol, the t-test was used (Table 7). There were 

no significant differences found for any protocol between sediment types for PAH50. For TEH, 

the only significant difference observed between sediment types was found in cleaning protocol 

2 (p=0.0353). Based on these observations, the decision was made to pool all replicates within a 

cleaning protocol, regardless of sediment type, for further analyses.

Table 7: T-test results for silt versus sand sediment comparison within each protocol.“*” denotes a 

significant difference (p<0.05) between sediment types for a particular cleaning protocol.

Cleaning Protocol TEH PAH50

CP1

CP2 *

CP3

CP4

CP5

CP6

Protocol Comparisons (using pooled sediment data) 

In order to determine if there were differences in the efficacy of each protocol, an 

ANOVA was performed using log transformed % residual PAH50 data. For this analysis, data 

from the two different sediment types within a cleaning protocol were pooled (i.e., the three 

silt and three sand replicates performed in any given cleaning protocol were pooled together). 

The ANOVA indicated that there was a significant difference among cleaning protocol means 

(p<0.0001). In subsequent Tukey-Kramer pairwise comparisons, significant differences were 

observed between CP1 and CP3, CP1 and CP4, CP1 and CP5, CP1 and CP6, CP2 and CP4, and 

CP2 and CP6 (Table 8). A nonparametric Kruskal-Wallis test was performed with the % residual 

TEH data. The Kruskal-Wallis test showed that there were significant differences among the 

cleaning protocol means (p = 0.0132). A nonparametric comparison for all pairs using the Dunn 

Method for joint ranking was conducted; significant differences were observed between CP1 

and CP5, and CP1 and CP6 (Table 8). From these results it can be inferred that protocols that 

use solvent as a step (CPs 3-6) were more effective in removing chemical residue than protocols 

without solvent (CP1 and CP2). This hypothesis was tested for both the % residual PAH50 and 

% residual TEH data. It was found that there was a significant difference between protocols using 

solvents versus protocols not using solvent for both the PAH50 and TEH data (Student’s t-test, 

p<0.0001 and nonparametric Wilcoxon test, p=0.0018 respectively). 

14
Results and Discussion

Table 8: Results of Tukey-Kramer pairwise (PAH50) and Dunn All Pairs for Joint Ranks (TEH) for 

comparisons among cleaning protocols using pooled sediment types.“*” denotes a significant difference 

for PAH50, “+” denotes a significant difference for TEH.

CP1 CP2 CP3 CP4 CP5 CP6

CP1 * * * *

CP2 * *

CP3

CP4

CP5 +

CP6 +

Protocol Comparisons (within sediment types) 

Differences between cleaning protocols within each sediment type were also evaluated. 

To determine if there were significant differences among cleaning protocols for the sand 

sediment (Folly River sediment), an ANOVA using log transformed % residual PAH50 data 

was conducted with a follow-up Tukey-Kramer pairwise comparison (Table 9). For the sand 

sediment, a significant difference was observed among cleaning protocol means (p<0.0001). 

Treatments that were significantly different from one another are denoted by “*” in Table 9. A 

similar ANOVA was also performed for silt sediment (Leadenwah Creek sediment); there were 

no significant differences among cleaning protocol means (p=0.1307 for % residual PAH50 and 

p=0.0968 for % residual TEH). For the sand sediment, more than half of the % residual TEH data 

was below the detection limit so there was no statistical analysis applied. 

Table 9: Results of Tukey-Kramer pairwise comparisons among cleaning protocols using sand sediment 

type only (there were no significant differences for silt-PAH50 or silt-TEH). “*” denotes a significant 

difference for PAH50 in sand sediments. Sand-TEH was not performed due more than half of the data 

being less than the detection limit.

CP1 CP2 CP3 CP4 CP5 CP6

CP1 * * * *

CP2 * * * *

CP3

CP4 *

CP5 *

CP6

Results of comparisons among cleaning protocols with the used pooled sediment (Table 

8) and those based on sediment type (Table 9) suggest that differences in the effectiveness of 

different cleaning protocols are driven by sediment type. There were no significant differences 

related to % residual PAH50 among cleaning protocols for the silt sediment. Conversely, 

significant differences were observed among cleaning protocols for the sand sediment. A plot 

of % residual PAH50 by sediment type and cleaning protocol (Figure 1), illustrates that silt 

replicates encompassed a large amount of variability, while PAH50 measured in the sand 

replicates was much less variable. The large variability within silt replicates could explain why 

we were not able to detect statistically significant differences between sediment types within 

15
Results and Discussion

a cleaning protocol and it may also explain why no differences were detected when looking at 

only the silt sediment across all cleaning protocols. During the cleaning protocol process it was 

documented (Figures 2A-D) that some of the silt replicates still had visible sediment or oil on 

the bowl and/or spoon after the initial site water rinse was performed whereas the sand replicates 

generally appeared to be “clean” after the first rinse (Figure 3). The inherent “sticky” nature of 

the silt sediment appears to lead to an inconsistent ability to clean the bowl/spoon effectively, 

which may be responsible for the observed variability. Sand, in contrast, was easier to remove 

from the bowl and spoon, which led to less variable results. 

Figure 1: Percent residual PAH50 plotted for each sediment type. Error bars are one standard deviation.

16
Results and Discussion

 

 

Figure 2A-D: Photos taken during the cleaning protocol process. All photos are from silt replicates and 

show sediment and/or oil that was remaining after the initial site water rinse. Figure A was from CP2, rep 

1 (site water/soap and brush/site water/DI water); B was from CP2, rep 3; C was from CP3, rep 3 (site 

water and brush/site water/acetone/DI water); and D was from CP4, rep 3 (site water/soap and brush/site 

water/acetone/hexane/air dry).

17
Results and Discussion

Figure 3: Photo of the site water rinse process during a sand replicate.

The PAH50 profiles, on an average proportional basis, were plotted for each sediment 

type (Figure 4). PAH profiles between the two sediment types are very consistent. The 

predominant PAHs in the Slick B spiked sediment were C1-C4 phenanthrenes, C1-C4 

dibenzothiophenes and C1-C3 fluorenes. Average residual PAH50 profiles were plotted for 

each cleaning protocol as well (Figure 5A and 5B). The predominant PAHs that remained after 

each cleaning protocol were also the C1-C4 phenanthrenes, C1-C4 dibenzothiophenes and 

C1-C3 fluorenes. Patterns between each protocol are generally consistent. This indicates that 

certain PAHs are not being selectively removed based on a particular cleaning protocol and also 

demonstrates that the residual PAHs are related to residual oil rather than laboratory processes as 

noted earlier. 

18
Results and Discussion

Figure 4: Average PAH50 profiles for both the sand and silt spiked sediments. Error bars are one standard deviation. 

19
Results and Discussion

20
Results and Discussion

Figure 5A-B: The average proportional residual PAH profile after each cleaning protocol. For ease for viewing, the PAH50 profile was separated into low molecular weight PAHs (A) and high molecular weight PAHs (B). Low molecular weight PAHs contain three or fewer rings; high molecular weight PAHs have four or more rings. Some light weight PAHs are observed (i.e. naphthalene, C2-naphthalenes), however, looking at the sediment profiles for Slick B (Figure 1), these PAHs are not present. It is thought that these PAHs are related laboratory process contamination rather than the cleaning process. Error bars are one standard deviation.

21
Conclusions

Conclusions

 Six field cleaning protocols were tested with two different spiked sediment types. Even at 

these worst-case sediment scenarios, the highest residual percentages of TEH and PAH50 in any 

of the cleaning protocol replicates were 0.032% and 0.029% respectively. Generally, the cleaning 

protocols left hydrocarbon residues that were ≤ 0.01% of the amount in the sediment sample. 

This indicates that regardless of decontamination protocol or sediment type, the TEH and PAH50 

residue remaining is so minimal that it would be indistinguishable from other sources of field 

sampling or laboratory analytical variability. While statistically significant differences were 

detected in the relative efficacies of different cleaning protocols (i.e., protocols that included 

a solvent step removed more hydrocarbons from the equipment than those that did not), the 

differences were inconsequential given that only very low hydrocarbon residues were measured 

in all cases. 

From these results, it was observed that cleaning protocols that used solvent as part of the 

process were more effective than protocols that did not. Unfortunately, bringing solvent bottles 

into the field is not always a feasible option and the use of isopropyl alcohol wipes represents an 

effective and practical alternative to solvents such as acetone and hexane. Ultimately, although 

the results of this study of oil-spiked sediments indicated that cross-contamination from properly 

cleaned and reused field sampling equipment was negligible, good field sampling practices 

should continue to be followed, including the practice of collecting equipment blanks as ordained 

by the sampling plan, and, if possible, the sequencing of sample collection from areas of least to 

areas of most expected contamination. 

22
Literature Cited

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24
Supplemental Information

Supplemental Information

Where:

j = sample

i = analyte

ISa = internal standard area

ISm = internal standard mass

SACi = average MDPAi + 3σMDPAi

m = calibration slope

b = calibration intercept

Supplemental Figure 1: Equation for calculating individual PAH MDLs. 

25
Supplemental Information

26
Supplemental Information

Supplemental Figure 2: PAH analyte proportions for each cleaning protocol blank. For ease for viewing, the PAH50 profile was separated into low molecular weight PAHs (A) and high molecular weight PAHs (B). Low molecular weight PAHs contain three or fewer rings; high molecular weight PAHs have four or more rings. 

27
Supplemental Information

Supplemental Figure 3: PAH 50 profile for PAHs measured in the solvent, seawater and cleaning protocol blanks (the blanks from each of the six protocols were averaged together). The error bars are standard deviation. 

28
Supplemental Information

Supplemental Table 1: Grain-size analysis and Particle (Φ) Distribution

Folly River Leadenwah Creek 

Φ 

Fraction

Percent (%) 

Composition

% Sediment 

Fraction

Percent (%) 

Composition

% Sediment 

Fraction

Gravel -1 0 0 0 0

Sand 0 0 93.8 0 48.8

1 0.242 0.846

1.5 0.107 0.172

2 1.39 1.81

2.5 7.56 7.12

3 50.9 24.0

3.5 31.2 11.8

4 2.43 3.02

Silt 4 0.186 6.2 0.484 51.2

4.5 0.371 4.25

5 0.047 0.147

5.5 0.191 0.125

6 0.174 1.79

6.5 0.238 2.09

7 0.514 2.21

7.5 0.279 14.6

Clay 8 0.346 10.8

8.5 0.149 1.23

9 3.70 13.8

29