Sediments

Valence state: The combining capacity of an atom or radical determined by the number of electrons that it will lose, add, or share when it reacts with other atoms.

Source: The American Heritage™ Dictionary of the English Language, Fourth Edition
Copyright © 2000 by Houghton Mifflin Company.

free product: A NAPL found in the subsurface in sufficient quantity that it can be partially recovered by pumping or gravity drain.

aerobic: Direct aerobic metabolism involves microbial reactions that require oxygen to go forward. The bacteria uses a carbon substrate as the electron donor and oxygen as the electron acceptor. Degradation of contaminants that are susceptible to aerobic degradation but not anaerobic often ceases in the vicinity of the source zone because of oxygen depletion. This can sometimes be reversed by adding oxygen in the form of air (air sparging, bioventing), ozone, or slow oxygen release compound (e.g., ORC(r)).

Aerobic dechlorination may also occur via cometabolism where the dechlorination is incidental to the metabolic activities of the organisms. In this case, contaminants are degraded by microbial enzymes that are metabolizing other organic substrates. Cometabolic dechlorination does not appear to produce energy for the organism. At pilot- or full-scale treatment, cometabolic and direct dechlorination may be indistinguishable, and both processes may contribute to contaminant removal. For aerobic cometabolism to occur there must be sufficient oxygen and a suitable substrate which allows the microbe to produce the appropriate enzyme. These conditions may be present naturally but often in the presence of a source area oxygen and a substrate such as methane or propane will need to be introduced.

Adapted from US. EPA 2006 Engineering Issue: In Situ and Ex Situ Biodegradation Technologies for Remediation of Contaminated Sites

anaerobic: Direct anaerobic metabolism involves microbial reactions occurring in the absence of oxygen and encompasses many processes, including fermentation, methanogenesis, reductive dechlorination, sulfate-reducing activities, and denitrification. Depending on the contaminant of concern, a subset of these activities may be cultivated. In anaerobic metabolism, nitrate, sulfate, carbon dioxide, oxidized metals, or organic compounds may replace oxygen as the electron acceptor.

Anaerobic dechlorination also may occur via cometabolism where the dechlorination is incidental to the metabolic activities of the organisms. In this case, contaminants are degraded by microbial enzymes that are metabolizing other organic substrates. Cometabolic dechlorination does not appear to produce energy for the organism. At pilot- or full-scale treatment, cometabolic and direct dechlorination may be indistinguishable, and both processes may contribute to contaminant removal.

Quoted from US. EPA 2006 Engineering Issue: In Situ and Ex Situ Biodegradation Technologies for Remediation of Contaminated Sites

architecture: "Architecture" refers to the physical distribution of the contaminant in the subsurface. Residuals that take the form of long thin ganglia or small dispersed globules provide a larger surface area that will dissolve much faster than if the same amount of liquid were concentrated in a competent pool.

Sources: For purposes of this discussion, a DNAPL source zone includes the zone that encompasses the entire subsurface volume in which DNAPL is present either at residual saturation or as "pools" of accumulation above confining units. In addition, the DNAPL source zone includes regions that have come into contact with DNAPL that may be storing contaminant mass as a result of diffusion of DNAPL into the soil or rock matrix.

source zone: For purposes of this discussion, a DNAPL source zone includes the zone that encompasses the entire subsurface volume in which DNAPL is present either at residual saturation or as "pools" of accumulation above confining units. In addition, the DNAPL source zone includes regions that have come into contact with DNAPL that may be storing contaminant mass as a result of diffusion of DNAPL into the soil or rock matrix.

focal ulceration: The process or fact of a localized area being eroded away.

metaplasia of the glandular stomach: A change of cells to a form that does not normally occur in the tissue in which it is found.

hyperplasia of the glandular stomach: A condition in which there is an increase in the number of normal cells in a tissue or organ.

histiocytic: Degenerative.

duodenum: First part of the small intestine.

microcytic: Any abnormally small cell.

squamous cell papillomas: A small solid benign tumor with a clear-cut border that projects above the surrounding tissue.

squamous cell carcinomas: Cancer that begins in squamous cells-thin, flat cells that look under the microscope like fish scales. Squamous cells are found in the tissue that forms the surface of the skin, the lining of hollow organs of the body, and the passages of the respiratory and digestive tracts. Squamous cell carcinomas may arise in any of these tissues.

jejunum: The middle portion of the small intestine, between duodenum and ileum. It represents about 2/5 of the remaining portion of the small intestine below duodenum.

ileum: The distal and narrowest portion of the small intestine.

squamous: Flat cells that look like fish scales.

metaplasia: A condition in which there is a change of one adult cell type to another similar adult cell type.

ossification: The process of creating bone, that is of transforming cartilage (or fibrous tissue) into bone.

clastogenesis: Any process resulting in the breakage of chromosomes.

neoplastic: Abnormal and uncontrolled growth of cells.

ulceration: The process or fact of being eroded away.

leucocytosis: An elevation of the total number of white cells in blood.

neutrophils: A type of white blood cell.

chromodulin: A small protein that binds four trivalent chromium ions.

biomagnification: The increased accumulation and concentration of a contaminant at higher levels of the food chain; organisms higher on the food chain will have larger amounts of contaminants than those lower on the food chain, because the contaminants are not eliminated or broken down into other chemicals within the organisms.

exencephaly: Cerebral tissue herniation through a congenital or acquired defect in the skull.

everted viscera: Rotated body organs in the chest cavity.

To Be Considered: Documents, such as federal or state guidances, that are not legally binding but may be relevant to the topic in question.

gaining: A gaining surface water body is one where groundwater flows into it.

losing: A surface water body is losing when there is a permeable sediment bed that is not in contact with the groundwater allowing the surface water to seep through it.

fluvial: Of or pertaining to flow in rivers and streams.

lacustrine: Of or pertaining to a lake as in lacustrine sediments—sediments at the bottom of a lake.

lipid: Any class of fats that are insoluble in water.

lipophilic: Able to dissolve in lipids—in this case fatty tissue.

organelles: A part of a cell such as mitochondrion, vacuole, or chloroplast that plays a specific role in how the cell functions and membranes.

RfD: The RfD is an estimate of a daily exposure of the human population (including sensitive sub-groups) to a substance that is likely to be without "the appreciable risk of deleterious effects during a lifetime." An RfD is expressed in units of mg/kg-day.

autonomic: That part of the nervous system that controls non-conscious actions such as heart rate, perspiration and digestion.

ataxia: Lack of muscle coordination.

funnel-and-gate configuration: A system where low-permeability walls (the funnel) placed in the saturated zone direct contaminated ground-water toward a permeable treatment zone (the gate)

References: ATSDR (Agency for Toxic Substances and Disease Registry). 2015. Draft Toxicological Profile for Perfluoroalkyls. 574 pp.

EFSA (European Food Safety Authority). 2008. Opinion of the scientific panel on contaminants in the food chain on perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) and their salts. EFSA Journal 653:1-131.

Hekster, F.M., R.W.P.M. Laane, and P. de Voogt. 2003. Environmental and toxicity effects of perfluoroalkylated substances. Reviews of Environmental Contamination and Toxicology 179:99-121.

Higgins, C. and R. Luthy. 2006. Sorption of perfluorinated surfactants on sediments. Environmental Science & Technology 40(23):7251-7256.

HSDB (Hazardous Substances Data Bank). 2012 Update. Perfluorooctanoic acid.

Kaiser, M.A., B.S. Larsen, C-P.C. Kao, and R.C. Buck. 2005. Vapor pressures of perfluorooctanoic, -nonanoic, -decanoic, -undecanoic, and -dodecanoic acids. Journal of Chemical and Engineering Data 50(6):1841-1843.

Kauck, E.A. and A.R. Diesslin. 1951. Some properties of perfluorocarboxylic acids. Industrial and Engineering Chemical Research 43(10):2332-2334.

Lewis, R.J., Sr., ed. 2004. Sax's Dangerous Properties of Industrial Materials. 11th ed. Wiley-Interscience, Hoboken, NJ. V3:2860.

Lide, D.R. 2007. CRC Handbook of Chemistry and Physics. 88th ed. CRC Press, Boca Raton, FL. 3-412.

SRC (Syracuse Research Corporation). 2016. PHYSPROP Database. SRC Scientific Databases, Accessed May 2016.

UNEP (United Nations Environmental Program). 2015. Proposal to List Pentadecafluorooctanoic Acid (CAS No: 335-67-1, PFOA, Perfluorooctanoic Acid), Its Salts and PFOA-Related Compounds in Annexes A, B and/or C to the Stockholm Convention on Persistent Organic Pollutants. UNEP/POPS/POPRC.11/5.

USEPA (U.S. Environmental Protection Agency). 2016. Drinking Water Health Advisory for Perfluorooctanoic Acid (PFOA).#pdfsmall# Office of Water, EPA 822-R-16-005, 103 pp

• Overview
• Policy and Guidance
• Conceptual Site Models
• Fate and Transport of Contaminants
• Site Characterization
• Risk Assessment
  • Bioavailability, and Bioaccumulation, and Biotransformation
  • Human Health Risk Assessment
  • Ecological Risk Assessment
• Remediation
• Additional Resources

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Ecological Risk Assessment

EPA provides guidance for the performance of ecological risk assessment (ERA) in Ecological Risk Assessment Guidance for Superfund: Process for Designing and Conducting Ecological Risk Assessments (ERAGS), Interim Final (1997). ERAGS addresses the risk from hazardous substances released to the environment and does not focus on other stressors, such as physical alterations. An example of a physical stressor could be the infilling of a gravel bed of a stream by fine-grained sediments. Sediment fines may reduce the available oxygen between the gravel stones and reduce the quality of the habitat for breeding fish and macroinvertebrates, but may not necessarily be chemically contaminated.

ERAGS provides a contaminant-driven seven-step process for the ERA and an eighth step for risk management. The first two steps of the ERA process may stand alone as a screening-level risk assessment, thereby providing a decision point on whether to pursue additional investigations or reach a "no further action" decision. A screening-level ERA is purposely designed to be conservative to prevent a false assumption that no risk to ecological receptors exists from contamination when such a risk exists. If the output from Step 2 of the ERA shows no sediment contaminants exceeding conservative screening-level concentrations, the results can be used safely to conclude that little or no risk is present to ecological receptors, and that no further investigation is necessary. However, if the concentration of a contaminant exceeds a screening level, such as an ESB, or a hazard quotient (HQ) calculated in Step 2, there is a risk that should be addressed by completing ERA Steps 3 through 7. These steps also should be completed if the risk manager decides that insufficient data exist to support a screening level assessment.

The Role of Screening-Level Risk Assessments and Refining Contaminants of Concern in Baseline Ecological Risk Assessments
USEPA, Office of Solid Waste and Emergency Response, EPA 540/F-01/014, 10 pp, 2001

Risk Assessment Forum

This Web page contains a number of links to documents and guidance related to ecological risk assessment. The Risk Assessment Forum is a standing committee of senior EPA scientists. It was established to promote Agency-wide consensus on difficult and controversial risk assessment issues and ensure that consensus is incorporated into appropriate Agency risk assessment guidance.

Ecological Risk Assessment of Polycyclic Aromatic Hydrocarbons in Sediments: Identifying Sources and Ecological Hazard
Neff, J.N., S.A. Stout, and D.G. Gunster.
Integrated Environmental Assessment and Management, Vol 1, No 1, 2005 (abstract)

Evaluating Ecological Risk to Invertebrate Receptors from PAHs in Sediments at Hazardous Waste Sites
Burgess, Robert M.
EPA, Office of Research and Development, EPA/600/R-06/162F, 23 pp, 2009

Predicting Toxicity to Amphipods from Sediment Chemistry
USEPA, Office of Research and Development, EPA 600/R-04/030, 212 pp, 2005

This model predicts the risk of amphipod toxicity from known sediment chemistry.

Generic Ecological Assessment Endpoints (GEAE) for Ecological Risk Assessment
USEPA, Risk Assessment Forum, EPA 630/P-02/004f, 67 pp, 2004

Ecological Risk Assessment Training: Why and How to Develop Conceptual Models

Guidelines for Ecological Risk Assessment
USEPA, Office of Research and Development, EPA 630/R-95/002F, 1998

Recommendations for RMP Sediment Monitoring
San Francisco Bay Estuary Institute, 14 pp, 1998

This report provides examples of conceptual models of sediment transport and fate, and animal exposure and effects.

It is feasible to provide site -specific toxicity data for ERA by subjecting sediments collected from suspect areas to laboratory testing. Sediment toxicity tests may be short (acute) or long-term (chronic), and a range of organisms (fish, marine and freshwater invertebrates, and plants) can be employed. An amphipod sediment toxicity test can be used as a surrogate for such ecological attributes as the structure and function of the benthic community and the viability of the populations of fish and waterfowl that consume benthos. Specific endpoints can be selected for measurement. Echinoderms can be tested to evaluate reproduction, worms for growth, and amphipods for survival. While sediment toxicity testing gives an indication of the bioavailability of contaminants, it does not identify contaminants or account for biomagnification.

Components of Estuarine and Marine Ecological Risk Assessment
Klimas, D.M and D.A. MacDonald.
NOAA, National Ocean Service, 49 pp, 2007

This report is an introductory presentation by NOAA describing estuarine and marine ERA with references to bioaccumulation, bioavailability, toxicity testing, and the weight-of-evidence (WOE) approach.

Site-specific bioaccumulation data are usually acquired from the collection of wildlife and subsequent off-site tissue analysis; however, data also may come from exposing "clean" organisms, obtained from a commercial supplier, to contaminated sediments on site. On-site bioaccumulation tests usually involve suspending groups of caged organisms (often Corbicula fluminea, a clam) in sediment and determining the levels of contaminants in tissue before and after a specified test period.

Population studies of benthic invertebrates can be made at a site to provide additional data on the impact of sediment contamination. A record of the numbers of distinct taxa present in a sample collected from a site represents the diversity of its benthic community. A taxon is a grouping of organisms given a formal taxonomic name, such as species or genus. Increasing diversity equates to the increasing health of the benthic assembly and indicates that food, habitat, and niche space are all adequate for the survival and growth of many species.

The Sediment Quality Triad (Triad) combined with a weight-of-evidence approach is used to assess the contamination of sediments by integrating sediment chemistry, laboratory toxicity testing, and community structure indices. A table is assembled with scores derived for various locations (NOAA 2007). For example:

A Sediment Triad Analysis of Lakes Sammamish, Washington and Union
Moshenberg, K.L.
King County Department of Natural Resources and Parks, Water and Land Resources Division, Seattle, Washington, 109 pp, 2004

Using the Sediment Quality Triad Approach to Characterize Toxic Conditions in the Chesapeake Bay (2002): An Assessment of Tidal River Segments in the Bohemia, Elk, Northeast and Severn Rivers
Pinkney, A.E., B.L. McGee, P.C. McGowan, D.J. Fisher, J. Ashley, and D. Velinsky.
USEPA, Chesapeake Bay Program Office, CBFO-C05-01, 234 pp, 2005

The Stressor-Driven Approach to Identifying the Cause of Biological Impairment

The stressor identification (SI) guidance (US EPA 2000) is "intended to provide a formal and rigorous process that identifies stressors causing biological impairment in aquatic ecosystems" and "provides a structure for organizing the scientific evidence supporting the conclusions." This approach looks for the potential stressors that can cause biological impairment. In an estuarine environment, stressors could include elevated nutrient concentrations, algal blooms, low dissolved-oxygen content, or sediment contamination by chemical releases. For example, after the observation of biological impairment, such as the unexplained absence of a species of fish from a location where it would be expected, the SI process can include any of the following activities:

• Listing the candidate causes of impairment
• Analysis of the evidence
• Characterization of candidate causes � cause either eliminated or diagnosed, with strength of evidence evaluated
• Identification of the probable cause of impairment
• Identification or apportionment of the sources of the cause
• Management action � causes eliminated or controlled
• Monitoring results
• Restoration or protection of the biological condition

Stressor Identification Guidance Document
USEPA, Office of Water, EPA 822/B-00/025, 228 pp, 2000

Other Ecological Risk Resources

Adaptive Risk Assessment Modeling Systems
USACE

This Web page offers a downloadable tool for the evaluation of present and future human and ecological health impacts or risks associated with chronic exposure to militarily relevant compounds (MRCs) and other constituents of potential concern.

Baseline Ecological Risk Assessment for the Ogden Railyard Site Ogden, Utah
USEPA, Region 8, 400 pp, 2003

Demonstration and Certification of Amphibian Ecological Risk Assessment Protocol
B. Bleiler, D. Pillard, M. Johnson, C. Archer, M. Bazar, D. Anders, D. Barclift, J. Noles, P. Henry, K. Harvey, and A. Hawkins.
TR-2318-ENV, ESTCP Project ER-0514, 112 pp, July 2009

This report presents a methodology for evaluating potential risks to amphibians in wetlands and for deriving remediation goals based on these important ecological receptors. The project evaluated the validity of previously developed lead and copper screening values designed to be protective of amphibians and also applied the amphibian ERA framework presented in "Development of a Standardized Approach for Assessing Potential Risks to Amphibians Exposed to Sediments and Hydric Soils" (TR-2245-ENV, 2004) at a DoD site to evaluate whether or not it provides valuable risk management information. The protocols, ERA framework, and lead and copper screening values were deemed appropriate for use at both demonstration sites in addition to being sensitive enough to detect lethal and sublethal impacts due to firing range contaminant exposure. See also the project ESTCP Cost and Performance Report.

Demonstration and Commercialization of the Sediment Ecosystem Assessment Protocol
Rosen, G., D.B. Chadwick, M.A. Colvin, C. Stransky, A. Burton, J. Radford, H. Bailey, et al.
SPAWAR Technical Report 3052, ESTCP Project ER-201130, 278 pp, 2017

The Sediment Ecosystem Assessment Protocol (SEAP), an integrated ecological risk assessment approach, is based on the performance of a field-deployed device referred to as the Sediment Ecotoxicity Assessment Ring (SEA Ring). The commercially available SEA Ring consists of a circular carousel capable of housing an array of in situ bioassay chambers and passive sampling devices. The SEA Ring represents an alternative to traditional lab-based approaches to toxicity and bioaccumulation testing. Field demonstrations were conducted utilizing two different commercial prototypes of the SEA Ring for in situ bioaccumulation or toxicity testing at the Puget Sound Naval Shipyard and Intermediate Maintenance Facility; the Marine Corps Base in Quantico, VA; and Naval Base San Diego. Additional information: ESTCP Cost and Performance Report

Determination of the Biologically Relevant Sampling Depth for Terrestrial and Aquatic Ecological Risk Assessments
Kravitz, M. and R.H. Anderson.
EPA 600-R-15-176, ERASC-015F, 75 pp, 2015

Based upon an extensive review of ecological literature, this report attempts to provide defensible approximations for identification of the depth of the biotic zone in soils and sediments. Actual sampling depths may be modified by the assessor based on the purpose of the assessment. The methods used in this study differ somewhat between Part 1 (Terrestrial Biotic Zone) and Part 2 (Aquatic Biotic Zone). In Part 1, biological activity was quantified in forests and grasslands as a function of depth across selected metrics. In Part 2, the reviewers based the biotic zone(s) in various habitats on the 80th percentile of abundance or on biomass depth distributions.

Determining Steady-State Tissue Residues for Invertebrates in Contaminated Sediment
A.J. Kennedy, G.R. Lotufo, J.A. Steevens, and T.S. Bridges.
ERDC/EL TR-10-2, 114 pp, 2010

Risk assessment of contaminated sediments often involves quantification of compounds in tissues via laboratory bioaccumulation exposures of benthic invertebrates; however, the standard 28-day exposure duration may not be adequate for some compounds to reach steady state, which is defined as a stable concentration in exposed organisms. This report describes how site-specific correction factors were developed using uptake and elimination rate constants for estimating steady-state residues from 28-day exposures.

Ecological Risk Assessment Support Center (ERASC)

ERASC, based in Cincinnati, OH, provides technical information and addresses scientific questions of concern or interest on topics relevant to ecological risk assessment at hazardous waste sites. This Web site offers numerous publications related to sediment risk assessment.

The FishRand Spatially Explicit Bioaccumulation Model
von Stackelberg, K., M.A. Williams, and M.S. Johnson.
ESTCP Project ER-200917, 241 pp, 2014

Predictive models are required to evaluate the impact of potential contaminated sediment management alternatives. This project demonstrated at two Army sites the application of a probabilistic, spatially explicit, and dynamic bioaccumulation model, referred to as FishRand. Those results were compared to the currently accepted practice of a deterministic application and a probabilistic but not spatially explicit application. An application was developed for total PCBs, two individual PCB congeners, and three homologue groups at one site, and for DDT, DDE, and DDD at the other site. Since completion of this effort, the model has been updated to provide direct linkage to GIS files. Additional information: FishRand Model; Project Resources.

Guidance for Assessing Chemical Contaminant Data for Use In Fish Advisories Volume 1: Fish Sampling and Analysis - Third Edition
USEPA, Office of Water, EPA 823/B-00/007, 2000

Guidance for Assessing Chemical Contaminant Data for Use In Fish Advisories Volume 2: Risk Assessment and Fish Consumption Limits - Third Edition
USEPA, Office of Water, EPA 823/B-00/008, 2000

Measurement and Modeling of Ecosystem Risk and Recovery for In Situ Treatment of Contaminated Sediments: Phase I
Luthy, R.G., S.N. Luoma, and J.K. Thompson.
SERDP Project ER-1552, 184 pp, 2011

Strategies to assess ecological recovery after in situ sediment treatment by activated carbon (AC) amendment were evaluated at Hunters Point, San Francisco Bay, CA. Polyethylene sampling devices and a PCB immunoassay technique were compared and the polyethylene results correlated with those obtained using conventional methods. Further work with thin polyoxymethylene sampling devices demonstrated the utility of this method to measure the vertical pore-water profile in the sediment and how this compares to the AC distribution in sediment cores. Field-related influences on bioaccumulation and the effectiveness of AC amendment were tested with in situ bioassays and passive sampler deployment. A biodynamic model was used to simulate PCB exposure scenarios present at Hunters Point and the reference sites.

Mid-Continent Ecology Division

This Web site provides downloadable databases and publications on ecological risk assessment issues and research, many of which are sediment related.

Navy Guidance for Conducting Ecological Risk Assessment
Naval Facilities Engineering Command (NAVFAC).

In addition to guidance, this Web page links to issue papers, methods, tools, and case studies.

PCB Residue Effects (PCBRes) Database

The PCB Residue Effects (PCBRes) Database can assist scientists and risk assessors in correlating PCB and dioxin-like compound residues with toxic effects. The purpose is to develop PCB critical residue values for fish, mammals, and birds, especially as these relate to aquatic and aquatic-dependent species. This database also includes expression of critical residue values based upon PCB Aroclors and total PCB-based congener-specific methods because PCBs occur as complex mixtures. Because PCB toxicity occurs via the arylhydrocarbon-receptor (AhR), PCB toxicity has also been expressed using the sum of the dioxin-like PCBs after adjustment using toxicity equivalence factors (TEF). Limited dioxin and furan compounds in single and mixture studies are also included.

USEPA Ecological Risk Assessment Training

Sediment Ecosystem Assessment Protocol (SEAP): An Accurate and Integrated Weight-of-Evidence Based System
Burton, G.A., B. Chadwick, G. Rosen, and M. Greenberg.
SERDP, Project ER-1550, 162 pp, 2011

SEAP has been developed to address two high-priority needs: 1) develop and evaluate rapid measurement tools/screening assays to assess the ecological risk and recovery at contaminated sediment sites for relevant receptors, particularly for assessing natural recovery and 2) assess the ecological impacts to benthic communities of remedial technologies currently in use at contaminated sediment sites. The SEAP method is meant to provide a relative ranking of station risk, identifying high-risk sediments in particular.

Sediment Quality Guidelines Approved for the National Status and Trends Program
NOAA, 12 pp, 1999

NOAA developed Sediment Quality Guidelines as informal, interpretive tools for its National Status and Trends program. These are numerical guidelines that initially were intended for NOAA�s use in ranking areas that required further investigation for adverse effects, such as toxicity.

Sediment Toxicity Identification Evaluation (TIE): Phases I, II, and III. Guidance Document
Ho, K.T., R.M. Burgess, D.R. Mount, T.J. Norberg-King, and J.R. Hockett.
EPA 600-R-07-080, 145 pp, 2007

This document incorporates the current understanding of TIE methods for identifying the cause(s) of toxicity in both marine and freshwater interstitial waters and whole sediments. This guidance does NOT include approaches for the implementation of sediment TIE in a regulatory context. Phase I TIE (characterization) methods for interstitial waters and whole sediments includes guidance on when to use whole sediment or interstitial water methods, the collection of interstitial waters for testing, and test volume considerations. Existing guidance for Phases II and III methods has been tailored for chemical classes normally found in sediments.

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