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
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Contaminated sediments present short and long-term toxic risks to human health and wildlife. Sediment contaminants include persistent organic pollutants, such as the polychlorinated dibenzo-p-dioxins and furans (PCDDs and PCDFs), polychlorinated biphenyls (PCBs), and chlorinated pesticides. Recognized adverse impacts of long-term exposure of both human and wildlife receptors to PCDDs, PCDFs, and the dioxin-like PCBs include impairment of the immune, neurological, and reproductive systems, impaired development of the young, and an increased risk of cancer. Polycyclic aromatic hydrocarbons (PAHs), present in fuel spills, coal tars, creosotes, and urban runoff, are frequent sediment contaminants and are known human and animal carcinogens. The chlorinated pesticides can impair the central nervous system and disrupt the endocrine systems of human and wildlife receptors. Contamination of sediment with heavy metals, such as cadmium, lead, arsenic, and mercury, can lead to kidney and nervous system damage and impaired development in ecological and human receptors.

The adverse effects of contaminated sediment on the structure and function of the benthic community can result in a loss of population for the wildlife communities that depend on them as their primary food source. Ecosystem processes that naturally purify water, such as the decomposition of organic matter and water filtration, can also be lost, resulting in environmental degradation.

The nature and magnitude of current and potential threats to human health and ecological receptors posed by contaminated sediment are characterized by the baseline risk assessment (BRA). A Superfund BRA is usually performed as part of the Remedial Investigation/Feasibility Study (RI/FS) phase of a response action.

Risk assessment supports risk management in the adoption of a management strategy for remediating contaminated sediment. Management strategies encompass a wide variety of actions, from intrusive remedies, such as dredging, removal, and treatment of contaminated sediment, to monitored natural recovery (MNR), or to a "no action" alternative. Each action has its own economic cost, engineering limitations and benefits, risks during implementation, and residual long-term risks to human and ecological receptors. Risk assessment provides a framework for identifying and ranking the risks associated with each alternative (US EPA 2005).

Baseline Ecological Risk Assessment of the Calcasieu Estuary, Louisiana
D.D. MacDonald, et al.
Archives of Environmental Contamination and Toxicology 61(1):1-58(2011)

As part of the RI/FS for this site, a baseline ecological risk assessment was conducted. Details of this work have been published in three consecutive papers in the July 2011 issue of Archives of Environmental Contamination and Toxicology. These papers describe the environmental setting and site history; identify the chemicals of potential concern (metals, PCBs, PAHs, PCDD/Fs, chlorinated benzenes, TCE, pesticides); present the exposure scenarios and conceptual model for the site; summarize the assessment and measurement endpoints used in the investigation; describe the results of an evaluation of effects-based sediment-quality guidelines; and present an assessment of risks to benthic invertebrates associated with exposure to contaminated sediment. Background information is summarized in an EPA document, Calcasieu Estuary Remedial Investigation/Feasibility Study (RI/FS): Baseline Ecological Risk Assessment Workshop (2000). Link to abstracts

Contaminated Sediment Remediation Guidance for Hazardous Waste Sites
USEPA OSWER December 2005

Framework for Metals Risk Assessment
EPA, Office of Science Adviser, EPA 120/R-07/001, 172 pp, 2007

This document covers both human health and ecological risk assessment for metals.

Hudson River Natural Resources Damage Assessment Plan
Hudson River Trustee Council, 81 pp, 2002

This document describes the wide-ranging economic, cultural, and ecotoxicological impacts of PCB contamination on the Hudson River.

Implementation of Dredging Risk Assessment Modeling Applications for Evaluation of the No-Action Scenario and Dredging Impacts
U. S. Army Corps off Engineers (USACE), ERDC TN-DOER-R2, 14 pp, 2001

Importance of Implementation and Residual Risk Analyses in Sediment Remediation
Wenning, R.J., S. Sorenson, and V.S. Magar.
Integrated Environmental Assessment and Management, Vol 2, No 1, Jan 2006

This review links risk assessment to cost/benefit analysis and discusses two types of risk—biological and engineering—that deserve consideration when evaluating sediment remedy alternatives.

Rapid Sediment Characterization (RSC) Tools for Ecological Risk Assessment
SPAWAR Systems Center Pacific, 21 pp, June 2011

RSC technologies are field-transportable screening tools that provide measurements of chemical, biological or physical parameters on a real-time or near real-time basis. These tools can streamline many aspects of the ecological risk assessment (ERA) process when used to delineate areas of concern, fill in information gaps, and assure that expensive, certified analyses have the greatest possible impact. X-ray fluorescence for metals, UV fluorescence for PAHs, QwikSed bioassay for assessing toxicity, and several other techniques are discussed for their use at marine sediment sites, and examples are provided.

Risk Characterization Handbook
USEPA, Science Policy Council, EPA 100/B-00/002, 189 pp, 2000

The Risk Characterization Guide is designed to provide risk assessors, risk managers, and other decision-makers an understanding of the goals and principles of risk characterization, the importance of planning and scoping for a risk assessment, the essential elements to address in a risk characterization, the factors that are considered in decision making by risk managers, and the forms the risk characterization takes for different audiences. A discussion of the various administrative details regarding risk characterization completes the guide.

A Risk Management Strategy for PCB Contaminated Sediments
National Academy of Sciences, 452 pp, 2001

The summary of this document presents the 11 major conclusions and recommendations concerning the risks presented by PCB contaminated sediments and management options.

Sediment Toxicology
USGS Columbia Missouri Office

This Web page contains numerous primarily USGS produced documents and studies concerning toxicity assessments of sediment.

Toxicity of Sediments
Burton, G.A. and P.F. Landrum.
In the Encyclopedia of Sediments and Sedimentary Rocks, Kluwer Academic Publishers, Dordrecht, p 748-751, 2003

This chapter includes a brief introduction to the subject of sediment toxicity.

Toxicological Profiles
Agency for Toxic Substances and Disease Registry (ATSDR)

ATSDR publishes toxicological profiles for organic and inorganic chemicals, some of which may be found in sediment. Each profile lists the chemical�s health effects by route of exposure (oral, dermal, and inhalation); its toxicokinetics, chemical, and physical information; its potential for human exposure, including its environmental fate and transport; and methods of chemical analysis.

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