Lexikon

natural sediments are defined as the organic and inorganic materials found at the bottom of a water body. Sediments may include clay, silt, sand, gravel, decaying organic matter, and shells among other things, but exclude anthropogenic debris, such as vehicle tires.

Sediments can become contaminated in a number of ways. Urban runoff that discharges to surface waters often contains polycyclic aromatic hydrocarbons (PAHs), oil and grease, and heavy metals. Agricultural runoff may contain nutrients and pesticides. Industrial spills and releases, especially those that occurred before controls were in place, can put product into the water. Chemicals that are denser than water, such as polychlorinated biphenyls (PCBs) and some pesticides like DDT, will sink to the bottom of water bodies and directly contaminate sediments. Atmospheric deposition of substances such as mercury is another source of sediment contamination as is the discharge of contaminated groundwater through the sediments to the overlying surface water (USEPA 1999 and USEPA 2005).

The classes of contaminants that are most common in sediment contamination are pesticides, PCBs, PAHs, and to a lesser extent dissolved phase chlorinated hydrocarbons. With the right geochemical conditions heavy metals and metalloids can also occur in sediments or precipitate into them. The sediments of many marinas are contaminated with tributyltin, an organo tin compound that was used as a biocide in marine paints (USEPA 1999).

Sediment investigations are generally conducted in two parts. The first uses common sampling and analytical procedures to determine if the total concentrations of contaminants are high enough to warrant concern. The underlying assumption is that all the contaminant is bioavailable. If the data indicate there may be a problem, then the second part of the investigation is done. This part focuses on bioavailability and determining whether there is physical evidence of an impact such as less biodiversity in the impacted sediments and the presence of the chemicals in the tissue of flora and fauna (USEPA 2005).

In addition to evaluating contaminant concentrations, the site investigation needs to develop a very complete conceptual site model. Unlike conventional soil and groundwater investigations, where rapid change in the site conditions is not expected, sediment systems can be very dynamic and it is important for both the risk assessment and remedy selection to have a full understanding of potential changes in site dynamics. A fuller discussion on investigation techniques is found in the Site Characterization section (USEPA 2005).

The risk assessment estimates the potential impacts of the contaminated sediments on human and ecological receptors. Many common organic sediment contaminants are suspected carcinogens and some, such as PCBs and mercury, bioaccumulate in the food chain. Risk assessors have developed a triad, or weight-of-evidence approach, that integrates sediment chemistry, laboratory toxicity testing, and community structure indices to assess risk (Pinkney et al 2005). A more complete discussion of sediment risk assessment and related guidance documents can be found in the Risk Assessment section.

Sources:

USEPA. 1999. Introduction to Contaminated Sediments. EPA 823-F-99-006, Office of Science and Technology, 24 pp.

USEPA. 2005. Adobe PDF LogoContaminated Sediment Remediation Guidance for Hazardous Waste Sites, EPA-540-R-05-012. Office of Superfund Remediation and Technology Innovation, 236 pp.

Pinkney, A.E., B.L. McGee, P.C. McGowan, D.J. Fisher, J. Ashley, and D. Velinsky. 2005. Adobe PDF LogoUsing 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, CBFO-C05-01. USEPA, Chesapeake Bay Program Office, 234 pp.

sedimentary rock is the type of rock that is formed by sedimentation of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle and accumulate or minerals to precipitate from a solution. Particles that form a sedimentary rock by accumulating are called sediment. Before being deposited, sediment was formed by weathering and erosion in a source area, and then transported to the place of deposition by water, wind, mass movement or glaciers. Though sedimentary rocks form just a small part of the Earth's crust, they cover the largest part of the Earth's surface. Sedimentary rocks are deposited in strata that form a structure called bedding. Sedimentary rocks contain important information about the history of Earth. They contain fossils, the preserved remains of ancient plants and animals. The composition of sediments provides us with clues as to the original rock. Differences between successive layers indicate changes to the environment which have occurred over time. Sedimentary rocks can contain fossils because, unlike most igneous and metamorphic rocks, they form at temperatures and pressures that do not destroy fossil remains. (http://en.wikipedia.org/wiki). Sedimentary rocks are classified into three groups. These groups are: clastic, chemical precipitate and biochemical or biogenic. Clastic sedimentary rocks are composed of discrete fragments or clasts of materials derived from other minerals. They are composed largely of quartz with other common minerals including feldspar, amphiboles, clay minerals, and sometimes more exotic igneous and metamorphic minerals. The classification of clastic sedimentary rocks is complex because there are many variables involved. Particle size (both the average size and range of sizes of the particles), composition of the particles, the cement, and the matrix (the name given to the smaller particles present in the spaces between larger grains) must all be taken into consideration. (http://en.wikipedia.org/wiki). Chemical sedimentary rocks form when minerals in solution become oversaturated and precipitate. In marine environments, this is a method for the formation of limestone. Another common environment in which chemical sedimentary rocks form is a body of water that is evaporating. Evaporation decreases the amount of water without decreasing the amount of dissolved material. Therefore, the dissolved material can become oversaturated and precipitate. Sedimentary rocks from this process can include the evaporite minerals halite (rock salt), barite and gypsum (http://en.wikipedia.org/wiki). Organic sedimentary rocks contain materials generated by living organisms, and include carbonate minerals created by organisms, such as corals, mollusks, and foraminifera, which cover the ocean floor with layers of calcite which can later form limestone. Other examples include coal and oil shale (derived from the remains of tropical plants and subjected to heat) (http://en.wikipedia.org/wiki).

according to REACH definition, an eye damage is serious the production of tissue damage in the eye, or serious physical decay of vision, following application of a test substance to the anterior surface of the eye, which is not fully reversible within 21 days of application.

The Society of environmental toxicology and Chemistry is a not-for-profit, worldwide professional organization comprised of individuals and institutions dedicated to the study, analysis and solution of environmental problems, the management and regulation of natural resources, research and development and environmental education. Our mission is to support the development of principles and practices for protection, enhancement and management of sustainable environmental quality and ecosystem integrity.
SETAC fulfills its mission through the advancement and application of scientific research related to contaminants and other stressors in the environment, education in the environmental sciences and the use of science in environmental policy and decision-making.
http://www.SETAC.org/

SETAC Europe is a Geographic Unit (GU) of the Society of environmental toxicology and Chemistry (SETAC), established to promote and undertake activities of SETAC in Europe. SETAC Europe is dedicated to the use of multidisciplinary approaches to examine the impacts of stressors, chemicals, and technology on the environment. The Society also provides an open forum for scientists and institutions engaged in the study of environmental problems, management and regulation of natural resources, education, research and development, and manufacturing.
http://www.SETAC.org/node/88

the silicate minerals make up the largest and most important class of rock-forming minerals, comprising approximately 90 percent of the crust of the Earth. Silicate minerals all contain silicon (silicium in Latin) and oxygen. They are classified based on the structure of their silicate group. The most predominant silicate is quartz (SiO₂). The basic chemical unit of silicates is the (SiO₄) tetrahedron shaped anionic group with a negative four charge (^-4). The central silicon ion has a charge of positive four while each oxygen has a charge of negative two (^-2) and thus each silicon-oxygen bond is equal to one half (1/2) the total bond energy of oxygen. This condition leaves the oxygens with the option of bonding to another silicon ion and therefore linking one (SiO₄) tetrahedron to another and another, etc. Mineralogically, silicate minerals are divided according to structure of their silicate anion into the following groups: nesosilicates (single tetrahedrons), sorosilicates (double tetrahedrons), inosilicates (single and double chains), cyclosilicates (rings), phyllosilicates (sheets), tectosilicates (frameworks).The phyllosilicates (sheet silicates) include the clay minerals. They are one of the primary products of chemical weathering and one of the more abundant constituents of sedimentary rocks. The basic structure of the phyllosilicates is based on interconnected six member rings of SiO₄^-4 tetrahedra that extend outward in infinite sheets. Three out of the 4 oxygen atoms from each tetrahedon is shared with other tetrahedra. This leads to a basic structural unit of Si₂O₅^-2. In case the Si⁺⁴ atom in the middle of the tetradera is replaced by lower valency atoms such as Fe⁺³ or Al⁺³, then more negative bonds become available on the surface of the sheet structured clay minerals (http://en.wikipedia.org). These bonds have primary role in plant nutrient fixation, exchange and supply. Meanwhile these bonds contribute to the sorption of inorganic contaminants, fixing of ions to the surface of the clay mineral, while in case of treatment of contaminated soil to their removal (soil washing, extraction) or even to their stabilisation (soil stabilisation, immobilisation, chemical immobilisation/stabilisation in soil, vitrification). See also fate of inorganic pollutants in soil.

site of Community importance means a site which, in the biogeographical region or regions to which is belongs, contributes significantly to the maintenance or restoration at a favourable conservation status of a natural habitat type in Annex I or of a species in Annex II and may also contribute significantly to the coherence of Natura 2000 referred to in Article 3, and/or contributes significantly to the maintenance of biological diversity within the biogeographic region or regions concerned.

For animal species ranging over wide areas, sites of Community importance shall correspond to the places within the natural range of such species which present the physical or biological factors essential to their life and reproduction;

Source: Council Directive 92/43/EEC of 21 May 1992 on the conservation of natural habitats and of wild fauna and flora.
http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:31992L0043:EN:html

Irritation and corrosion are local effects, i.e. changes occur at the site of first contact of the substance with the skin, eye, or mucous epithelia such as the respiratory tract.

Corrosive substances may destroy living tissues with which they come into contact after single exposure. Irritant substances are non-corrosive substances which, through immediate contact with the tissue under consideration may cause inflammation after single exposure.

Substances that cause irritant effects only after repeated exposure are not classified as irritants. Skin and/or eye irritation refers to the production of fully reversible changes following application of a substance (in the case of eye irritation, when application is performed to the anterior surface of the eye).

Corrosive substances produce irreversible effects such as necrosis through the epidermis and into the dermis, ocular tissue damages or decay of vision.

Chemicals which are classified for respiratory irritation may provoke irritations similar to skin or eye irritations. They may also cause other toxic effects, in relation with interactions with the vegetative nervous system and leading to reflex responses (sneezing, coughing, respiratory symptoms, etc). These effects are reversible. Testing for respiratory irritation is not required under REACH as no validated guidelines are available. Nevertheless, existing and available data that provide evidence of the respiratory irritation potential of a substance should be taken into account.

a rotating cultivation technique in which trees are cut down and burned in order to clear land for temporary agriculture; the land is used until its productivity declines at which point a new plot is selected and the process repeats; this practice is sustainable while population levels are low and time is permitted for regrowth of natural vegetation; conversely, where these conditions do not exist, the practice can have disastrous consequences for the environment.

Sustainable maNagement of sOil and groundWater under the pressure of soil pollution and soil contaMinAtioN. The objectives of SNOWMAN are to:
1. Review European research activity in the field of protection of soil and groundwater from contamination;
2. Produce a new vision which identifies research needs in this area at the European scale;
3. Develop mechanisms to improve cooperation and coordination between the member states in the delivery of this new research agenda.
http://www.environment-agency.gov.uk/science/922300/scienceprojects

a Socio Economic Assessment and Analysis (SEA) may include the following elements:

1. Impact of a granted or refused authorisation on the applicant(s), or, in the case of a proposed restriction, the impact on industry (e.g. manufacturers and importers). The impact on all other actors in the supply chain, downstream users and associated businesses in terms of commercial consequences such as impact on investment, research and development, innovation, one-off and operating costs (e.g. compliance, transitional arrangements, changes to existing processes, reporting and monitoring systems, installation of new technology, etc.) taking into account general trends in the market and technology.
2. Impacts of a granted or refused authorisation, or a proposed restriction, on consumers. For example, product prices, changes in composition or quality or performance of products, availability of products, consumer choice, as well as effects on human health and the environment to the extent that these affect consumers.
3. Social implications of a granted or refused authorisation, or a proposed restriction. For example job security and employment.
4. Availability, suitability, and technical feasibility of alternative substances and/or technologies, and economic consequences thereof, and information on the rates of, and potential for, technological change in the sector(s) concerned. In the case of an application for authorisation, the social and/or economic impacts of using any available alternatives.
5. Wider implications on trade, competition and economic development (in particular for SMEs and in relation to third countries) of a granted or refused authorisation, or a proposed restriction. This may include consideration of local, regional, national or international aspects.
6. In the case of a proposed restriction, proposals for other regulatory or non-regulatory measures that could meet the aim of the proposed restriction (this shall take account of existing legislation). This should include an assessment of the effectiveness and the costs linked to alternative risk management measures.
7. In the case of a proposed restriction or refused authorisation, the benefits for human health and the environment as well as the social and economic benefits of the proposed restriction. For example, worker health, environmental performance and the distribution of these benefits, for example, geographically, population groups.
8. An SEA may also address any other issue that is considered to be relevant by the applicant(s) or interested party.

Source: REACH regulation

soil acidification is a process whereby soil becomes acid (pH < 7) because acid parent material is present or in regions with high rainfall, where soil leaching occurs. Acidification can be accelerated by human activities such as the use of fertilisers, deposition of industrial and vehicular pollutants.

soil bioremediation based on aerobic oxidation means that the soil remediation is based on aerobic biodegradation. The microbiological biodegradation occurs in this case on a high redoxpotential of +0,8-+0,6 Volt. The degrading microorganisms utilise the pollutant as enbergy sources. The source of oxigen is the atmospheric air, soil air, or dissolved oxigen in soil moisture or ground water. If the oxigen-concentration is low, the technologist can increase it by aeration of the soil or the groundwater as well as by adding peroxide substances or other oxigene release compounds ORC to serve as oxigene source for the activation of the aerobic soil microbes.

small size laboratory microcosm prepared from a soil core, an undisturbed part of the soil with original microstructure. SCM is mainly for studying the microscale spatial gradients and processes in the soil.

soil fracturing is an enhancement technology designed to increase the efficiency of other in situ technologies in difficult soil conditions. The fracturing extends and enlarges existing fissures and introduces new fractures, primarily in the horizontal direction. When fracturing has been completed, the formation is then subjected to vapor extraction, either by applying a vacuum to all wells or by extracting from selected wells, while other wells are capped or used for passive air inlet or forced air injection. Technologies commonly used in soil fracturing include pneumatic fracturing (PF) and hydraulic fracturing. Fracturing is applicable to the complete range of contaminant groups with no particular target group. The echnology is used primarily to fracture silts, clays, shale, and bedrock.

Source: EURODEMO Project

soil remediation based on aerobic biodegradation is an oxidative process catalysed by microbes. Microbes, mainly bacteria utilise the contaminant as substrate for producing energy. Aerobic bacteria use athmospheric oxigen for the oxidation of the polluting organic compounds and produce inorganic products, such as CO₂, NO₃ and H₂O. This process is also called mineralisation.

When athmospheric oxigen is limited, the biodegradation is catalysed by facultative anaerobic microbes, which use NO₃ for their alternative respiration. In this case the oxidation/mineralisation products from the substrate the contaminant are alcohols or aldehydes.

anaerobic biodegradation of soil contaminants is based on the aternative respiration of soil microorganisms, using oxigen from NO₃^2-, SO₄^2-or CO₂, as hydrogen-acceptor instead of atmospheric oxigen. Paralel to the oxidation of the contaminant energy source in this case, nitrate, sulfate and carbonate are reduced into N₂ via nitrite NO₂⁻, nitric oxide NO, nitrous oxide N₂O, H₂S and CH₄ respectively.

There are some metals which can also be reduced and function as electronacceptor, such as ferric ion Fe³⁺reduction to Fe²⁺ or Fe⁰, manganic ion Mn⁴⁺ reduction to Mn²⁺, selenate SeO₄^2- reduction to selenite: SeO₃^2- and Se⁰, arsenate AsO₄^3- reduction to arsenite: AsO₃^3- or uranyl ion UO₂²⁺ reduction to uranium dioxide UO₂ for the electron transport chain.

The anaerobic biodegradation of xenobiotics needs a microorganism- and metabolism-specific redoxpotential. The soil remedial biotechnology is responsible for ensuring the proper redoxpotential in the soil to control the process and run biodegradation on the optimum.

To control the redoxpotential the technologist should ensure sufficient quantity of nitrate, sulfate or any other electronacceptors in the soil.