October 20, 1997

**Protocols For Collecting NRDA Samples INTERTIDAL SEDIMENTS**

# Sampling Objectives

-   To determine the concentration and source of oil compounds in the
    sediments collected.

-   To measure sediment characteristics for interpreting chemical and
    biological results.

-   To maintain the integrity the sample(s) during sampling, transport,
    and storage.

[**Sample Volume by Analytical Method**]{.underline} (see *back page for
description and suggested detection limits)*

THC by GC/FID 500 ml; or 1 pint or 16 oz\
PAH by GC/MS-SIM 500 ml; or 1 pint; or 16 oz\
TOC 10 g; or less than 10 ml\
Grain size 100 g; or 4 oz

# Sampling Equipment / Containers

-   To collect subsurface samples m coarse sediments (sand and gravel),
    it is easiest to use a shovel to dig a small trench and collect the
    desired sediment intervals from the exposed wall in the trench.

-   To collect subsurface samples in fine sediments (mud), use a shovel
    to expose the sediments at the desired depth. Collect the sample
    from the natural break side, rather than the shovel side.

-   Coring tubes can be used in muddy sediments when the sampling
    intervals have not been determined. Plastic tubes (polycarbonate or
    polyethylene is okay) should be 5 cm (2 in) in diameter, with a wall
    thickness of about 3 mm.

-   Sediment samples for THC and PAH should be placed in glass
    containers, certified-clean to be organic-free (solvent rinsed),
    with Teflon or aluminum-lined lid. For TOC, they can be placed in
    soap-cleaned glass or plastic containers. For grain size, Ziploc or
    Whirl-Pak bags can be used.

# Sample Collection Methods

-   Decon sampling equipment and supplies initially and between samples,
    if re-using them. First, wash with laboratory-grade detergent and
    clean water, with a triple clean water rinse. Use a clean water
    source for rinsing (distilled water from a local store is OK). Them
    rinse with methanol or acetone, followed by methylene chloride or
    hexane (Capillary GC Pesticide Residue Grade or equivalent). Do not
    work with solvents downwind of exhaust or other airborne hydrocarbon
    source. Collect waste/rinsate solvents for proper disposal

-   To reduce the need for field decon, use pre-cleaned, disposable
    utensils (e.g., stainless steel blade or wooden spatula), single-use
    core tubes, etc. The only equipment to be used between sites is a
    shovel

-   Discrete samples from a single sample point may be collected to
    represent a specific condition, such as a tarball for fingerprinting
    and source identification.

-   Composite samples (of at least three subsamples) are recommended for
    characterization of a sampling site, such as contaminant content in
    marsh sediments.

-   Photograph the sampling site prior to sample collection to document
    the site conditions.

-   For surface sediments, use a wooden spatula or stainless steel blade
    to accurately collect the top 2 cm, avoiding contact with disturbed
    sediments.

-   For subsurface sediments, expose a fresh surface at the desired
    interval, and then remove the sediments that were in contact with
    the shovel prior to sampling.

-   On each trip try to sample control and least oiled areas first, then
    the most contaminated areas.

-   Record the sample no. on both the label and lid. Record the
    following on the field log sheet:

-sample no.; date/time; station location; tidal elevation

-description of oiling conditions, using standard shoreline assessment
terminology

-sediment characteristics: texture, color, biota, vegetation, debris,
odor, etc.

-   Make a quick sketch in a field logbook or sketch form showing the
    sampling locations in enough detail that the location could be
    re-occupied by someone else.

# Preservation/Holding Times

-   Immediately place all sediment samples in a cooler and keep at 4 C.
    Freeze samples for chemical analysis by the end of each day.
    Refrigerate samples for TOC and grain size (do not freeze).

-   Use packing material such as bubble wrap, around containers to
    prevent breakage.

-   Sediment samples can be held frozen in the dark for several years
    without loss of sample integrity.

-   Sediment extracts can be held at 4°C in the dark/or 40 days without
    loss of sample integrity.

## Analytical Methods 

-   **Total hydrocarbons** (THC). Often referred to as total petroleum
    hydrocarbons, but most methods do not differentiate among petroleum,
    pyrogenic, and biogenic hydrocarbons. THC by GC-FID (total area of
    FID gas chromatogram of combined f1 and f2 fractions after column
    chromatography) is often the preferred method because of the low
    detection limit (2 ppm versus 100-1000 ppm for other THC methods)
    and the direct measurement of hydrocarbons. This method does not
    detect low boiling compounds (below n-C8). For NRDA, THC analyses
    generally will not provide the data needed to support calculation of
    toxic effects from PAH exposure, and will have to be corrected to
    equivalent PAHs. The THC results, however, can be used to track oil
    weathering and map extent of exposure of intertidal resources.
    Detection limits are usually higher than those needed for intertidal
    injury assessment.

-   **Polynuclear aromatic hydrocarbons** (PAH). Since most of the
    toxicity in oil is due to the PAHs, it is often the preferred
    analysis for NRDA. The analytes must include the alkyl-substituted
    PAH homologs, in addition to the standard PAH \"priority
    pollutants." This method is referred to as Modified EPA Method 8270,
    because the list of PAHs is expanded to include the alkylated
    homologs, using GC/MS in the selected ion monitoring mode. Detection
    levels should be 1 ppb for individual PAHs to support injury
    assessment using toxicity thresholds.

**[Other Considerations:]{.underline}**

-   Be aware of the potential for contamination of the site from oil on
    boots and shovels.

-   Keep a detailed photo log so that each photograph can be labeled.

-   Collect background samples from clean sites representative of
    pre-oiling conditions, as well as areas not yet oiled but in the
    potential path of the oil.

-   It is very important to have a defined sampling strategy prior to
    conducting field work. Intertidal sediments are difficult to sample
    because of their inherent heterogeneity over space, depth, and time.
    Truly quantitative samples have to be collected in a very precise
    manner and be related to a surface areas or meaningful volume
    metric. Grab samples are not very useful to injury quantification.
    Documenting exposure of intertidal areas is best accomplished with
    photography, video, and good field notes and sketches using standard
    shoreline assessment methods. Samples may be needed for
    fingerprinting or monitoring weathering, to correlate a degree of
    oiling term with oil loading, to confirm the presence of oil, or for
    bioassay purposes.

### Key References

NOAA, 1993. Sampling and analytical methods of the National Status and
Trends Program, National Benthic Surveillance and Mussel Water Projects,
1984-1992. Volume IV, Comprehensive descriptions of trace organic
analytical methods. Lauenstein, G.G. and A.Y. Cantillo (eds.). NOAA
Tech. Memo NOS ORCA 71, Silver Spring, MD. 181 pp.

Reinharz, E. and J. Michel, 1996. Preassessment phase guidance document.
NOAA Damage Assessment and Restoration Program, Silver Spring, MD. 35
pp. + 10 appendices.

Sauer, T.C. and P.D. Boehm. 1995. Hydrocarbon chemistry for analytical
methods for oil spill assessments. Marine Spill Response Corporation
Technical Report Series 95-032, Washington, D.C. 114 pp.

USEPA, 1979. Methods for chemical analysis of water and wastes.
EPA-600/4-79/020. USEPA Environmental Monitoring Systems Laboratory,
Office of Research and Development, Cincinnati, Ohio.

USEPA, 1986. Test methods for evaluating solid waste. SW 846 Third
Edition (and updates).