Lexikon

phytotechnology is broadly defined as the use of vegetation to address contaminants in soil, sediment, surface water, and groundwater. Cleanup objectives for phytotechnologies can be contaminant removal and destruction, control and containment, or both. Phytoremediation (i.e., contaminant removal and destruction) is a phytotechnology subset (ITRC 2009).

While phytotechnologies generally are applied in situ, ex situ applications (e.g., hydroponics systems) are possible. Typical organic contaminants, such as petroleum hydrocarbons, gas condensates, crude oil, chlorinated compounds, pesticides, and explosive compounds, can be addressed using plant-based methods. Phytotechnologies also can be applied to typical inorganic contaminants, such as heavy metals, metalloids, radioactive materials, and salts (ITRC 2009).

Six major plant mechanisms enable phytotechnologies to remove, destroy, transfer, stabilize, or contain contaminants:

1.Phytoextraction

Phytoextraction involves contaminant uptake by plant roots, with subsequent accumulation in plant tissue. Plants that accumulate contaminants may require periodic harvesting and proper disposal to avoid recontaminating the soil when the plants die or drop their leaves. Phytoextraction typically is used to address inorganic contaminants, such as metals, metalloids, and radionuclides. Organic contaminants are more likely to be transformed rather than accumulated within the plant tissue. Successful field applications of phytoextraction to take up metals have been limited; however, promising research is underway for using phytoextraction on mercury and persistent organic pollutants (USEPA 2006).

Pesticides classified as persistent organic pollutants resist biodegradation and can remain in the environment for decades. Scientists have identified plants that are capable of extracting chemicals, such as chlordane and 2,2-bis(p-chlorophenyl)1,1-dichloroethene (p,p'-DDE), and storing them in their roots, leaves, and fruits (USEPA 2006).

Plants used in phytoextraction (e.g., Indian mustard, Alpine pennycress, sunflowers, ferns, grasses) typically are effective only in the top one foot of soil because of their shallow root systems and generally slow growth. Researchers are working on genetic modifications that increase the survivability of plants that hyperaccumulate toxic contaminants (USEPA 2006).

2. Phytodegradation

Like phytoextraction, phytodegradation involves the uptake of contaminants; however, metabolic processes within the plant subsequently break down the contaminants. Phytodegradation also encompasses the breakdown of contaminants in the soil through the effects of enzymes and other compounds produced by plant tissues other than the roots (USEPA 2006).

Phytodegradation is applicable to organic contaminants. Their uptake is affected by their hydrophobicity, solubility, and polarity; moderately hydrophobic and polar compounds are more likely to be taken up after sorbing to plant roots. Chlorinated solvents, herbicides, insecticides, pentachlorophenol (PCP), polychlorinated biphenyls (PCBs), and munitions constituents have phytodegradation potential (USEPA 2006).

3. Phytovolatilization

Phytovolatilization is the uptake of a contaminant into a plant and its subsequent transpiration to the atmosphere, or the transformation or phytodegradation of the contaminant with subsequent transpiration of the transformation or degradation products to the atmosphere. Phytovolatilization generally is applied to groundwater but also can be applied to soluble soil contaminants (USEPA 2006).

Transformation or degradation of the contaminant within the plant can create a less toxic product that is transpired; however, degradation of some contaminants, like trichloroethene (TCE), may produce even more toxic products (e.g., vinyl chloride). Once in the atmosphere, these products may be degraded more effectively by sunlight (photodegradation) than they would be by the plant (phytodegradation), but the potential advantages and disadvantages of phytovolatilization must be assessed on a site-specific basis (USEPA 2006).

Phytovolatilization has been applied to both organic and inorganic (e.g., selenium, mercury, arsenic) contaminants, but it must be reiterated that simply volatilizing a contaminant may not be an acceptable alternative (USEPA 2006).

4.Rhizodegradation

The rhizosphere is the zone of soil influenced by plant roots. Essentially, rhizodegradation is "plant-assisted bioremediation" in that the root zone enhances microbial activity, thus increasing the breakdown of organic contaminants (such as petroleum hydrocarbons, PAHs, pesticides, BTEX, chlorinated solvents, PCP, PCBs, and surfactants) in the soil. The rhizosphere extends only about 1 mm from each root. The presence of plant roots moderates soil moisture and increases soil aeration, making conditions more favorable to bioremediation. The production of root exudates, such as sugars, amino acids, and other compounds, stimulates the population growth and activity of native microbes. Root exudates also may serve as food for the microbes, which can result in cometabolism of contaminants as degradation of exudates occurs. Because the microbes consume nutrients, the plants in a rhizodegradation plot often require additional fertilization (USEPA 2006).

Rhizodegradation actually breaks down contaminants; thus, plant harvesting and disposal is not necessary. In some instances, complete mineralization of the contaminant can occur. The success of this technique is site-specific, however, and laboratory microcosms may not reflect the microbial conditions encountered in the field. Petroleum hydrocarbons have been degraded successfully in the rhizosphere, but degradation of aged hydrocarbons has been shown to be more problematic (USEPA 2006).

5.Phytosequestration

Phytosequestration, also referred to as phytostabilization, is a mechanism that immobilizes contaminants, mainly metals, within the root zone, limiting their migration. Immobilization of contaminants can result from adsorption of metals to plant roots, formation of metal complexes, precipitation of metal ions (e.g., due to a change in pH), or a change to a less toxic redox state. Phytosequestration can occur when plants alter the chemical and microbial makeup of the soil (e.g., through the production of exudates or carbon dioxide), which impacts the fate and transport of the soil metals. (USEPA 2006) Although transport proteins within the plant facilitate the transfer of contaminants between cells, plant cells contain a compartment called the vacuole that acts, in part, as a storage and waste receptacle for the plant. The vacuoles of root cells can sequester contaminants, preventing further translocation to the xylem (ITRC 2009).

Because contaminants are retained in the soil, phytosequestration does not require plant harvesting and disposal; however, evaluation of the system is necessary to verify that translocation of contaminants into the plant tissue is not occurring. Due to the continuing presence of contaminants in the root zone, plant health must be monitored and maintained to ensure system integrity and prevent future release of contaminants. Phytosequestration also can be used to prevent migration of soil contaminants with wind and water erosion, soil dispersion, and leaching (USEPA 2006).

6. Phytohydraulics

Phytohydraulics is the ability of vegetation to evapotranspire sources of surface water and groundwater. Water interception capacity by the aboveground canopy and subsequent evapotranspiration through the root system can limit vertical migration of water from the surface downward. The horizontal migration of groundwater can be controlled or contained using deep-rooted species, such as prairie plants and trees, to intercept, take up, and transpire the water. Trees classified as phreatophytes are deep-rooted, high-transpiring, water-loving organisms that send their roots into regions of high moisture and can survive in conditions of temporary saturation. Typical phreatophytes include species such as cottonwoods, poplars, and willows (ITRC 2009).

Source: USEPA. 2006. In Situ Treatment Technologies for Contaminated Soil: Engineering Forum Issue Paper. EPA 542-F-06-013.

ITRC (Interstate Technology & Regulatory Council). 2009. Phytotechnology

Technical and Regulatory Guidance and Decision Trees, Revised. Phyto-3

PIC = Prior Informed Consent
The Rotterdam Convention on Prior Informed Consent (PIC) is a global treaty that came into force in February 2004, with the intention to protect developing countries from the import of dangerous chemicals. The PIC Convention is implemented in the EU by means of regulation concerning the export and import of dangerous chemicals. Under the proposed recast of this PIC Regulation, the companies will continue to notify to their national authorities their intention to export banned or severely restricted chemicals. ECHA will take over the task to communicate with the destination country and to keep a register of the notifications.

Source: News from ECHA, No 5, Oct 2011, http://echa.europa.eu/doc/press/newsletter/echa_newsletter_2011_5.pdf

Plant breeding is the science and practice of changing the genetics of plants for the benefit of mankind. Plant breeding can be accomplished through many different techniques ranging from simply selecting plants with desirable characteristics for propagation, through induced mutagenesis and following selection to more complex molecular techniques.

For several thousand years, farmers have been altering the genetic makeup of the crops they grow. Human selection for features such as faster growth, larger seeds or sweeter fruits has dramatically changed domesticated plant species compared to their wild relatives. Remarkably, many of our modern crops were developed by people who lacked an understanding of the scientific basis of plant breeding.

Despite the poor understanding of the process, plant breeding was a popular activity. Gregor Mendel himself, the father of genetics, was a plant breeder, as were some of the leading botanists of his time. Mendel's 1865 paper explaining how dominant and recessive alleles could produce the traits we see and could be passed to offspring was the first major insight into the science behind the art. The paper was largely ignored until 1900, when three scientists working on breeding problems rediscovered it and publicized Mendel's findings.

Major advances in plant breeding followed the revelation of Mendel's discovery. Breeders brought their new understanding of genetics to the traditional techniques of self-pollinating and cross-pollinating plants.

modern landfills are designed to protect both public health and the environment by providing physical containment of trash, isolation from air and water, and control of landfill gas, leachate, odors, disease vectors, and other nuisances. Modern landfill technology provides hydrologic isolation with various systems of liners and surface capping using compacted clay, plastic membranes, or both; as well as an overlay of about 18 inches of earthen material and at least six inches of soil to support native plant growth and control erosion. Final cover systems are also expected to meet aesthetic and other post-closure site end use criteria for waste management sites. These systems are intended to achieve their functional requirements for time periods of many decades to hundreds of years.

Questions about the long-term performance of the low-permeable layers in conventional cover designs have prompted significant interest and research into alternative designs. Alternative landfill cover systems emerged in the late 1990s as a possible cost-effective option to conventional covers and have been applied at some landfills and other types of waste management units (e.g., waste piles and surface impoundments). The implementation of an alternative cover system is dependent on specific site characteristics. The site characteristics that have a dominant influence on the choice of an appropriate final cover include climate, soils, landfill waste characteristics, hydrogeology, gas production, seismic environment, and reuse of landfill areas.

There are various alternatives to conventional covers. This site focuses on covers that utilize natural processes to manage water precipitating on waste containment sites, commonly known as evapotranspiration (ET) covers. These covers have proven an effective means of containing waste at municipal landfills, hazardous, and industrial waste landfills. There are other types of alternatives to conventional cover systems, such as asphalt barriers. However, these are not addressed on this site because they are not evapotranspiration covers.

ET covers are also known as store and release covers, vegetative covers, sponge and pump covers, alternative final covers (AFC), alternative final earthen covers (AFEC), and other names. They include various combinations of earthen materials and plants, and generally can be categorized into the following cover types:

Monolithic: Any precipitation water is stored in a layer of soil and later removed through evapotranspiration.

Capillary break: This cover uses a two layer system to increase the water storage capacity of the cover. A capillary break is formed by two layers – a layer of fine soil over a layer of coarser material (e.g. sand or gravel). Capillary force causes the layer of fine soil overlying the coarser material to hold more water than if there were no change in particle size between the layers.

Dry barrier: The dry barrier cover uses wind-driven airflow through the layer of coarse material to remove water from a storage layer.

Source: US-EPA, Clu-In: http://www.clu-in.org/products/evap/

there are 16 elements that are essential nutrients for plant growth. Plants can only take those nutrients from soils if they are easily available or in specific chemical forms. Chemical, physical and biological processes contribute to the availability of these nutrients in soils. In this context, processes carried out by soil biota are important for the maintenance of crop production and good crop yields. They also contribute to plant nutrition in areas where chemical fertilizers cannot be applied. Below are some examples of how the soil biota can contribute to the formation of nutrient pools and the availability of nutrients.

Source: EUROPEAN ATLAS OF SOIL BIODIVERSITY, JRC, European Comission, 2010

EU legislation regulates the marketing and use of plant protection products and their residues in food.

Council Directive 91/414/EEC concerning the placing of plant protection products on the market lays down rules and procedures for approval of the active substances at EU-level and for the authorisation at Member State level of plant protection products (PPPs) containing these substances. This Directive states that substances cannot be used in plant protection products unless they are included in a positive EU list. Once a substance is included in the positive list Member States may authorise the use of products containing them.

Pesticides residues in food are regulated by Regulation (EC) No 396/2005 . The legislation covers the setting, monitoring and control of pesticides residues in products of plant and animal origin that may arise from their use in plant protection. The maximum levels set are those consistent with good agricultural practice in Member States and third countries. The levels are set after an evaluation of any risks to consumers of different age groups and they are only set if they are considered safe. Nonetheless, MRLs (Minimal Risk Level) exceedences are closely monitored, evaluated and communicated to the authorities in the Member States through the Rapid Alert System for Food and Feed whenever there is a potential risk to consumers.

Both Directive 91/414 on the placing on the market of plant protection products and Regulation 396/2005 on pesticide residues in food and feed aim at a high level of protection of human health and the environment.

The European Parliament approved new EU pesticides legislation in January 2009, which will increase the number of pesticides available in Member States, while in due course banning the use of certain dangerous chemicals in these products. Measures to ensure the safer use of pesticides in daily life will also be introduced.

The key points of the new regulation, which deals with the production and licensing of pesticides, are as follows:

• A positive list of approved "active substances" (the chemical ingredients of pesticides) is to be drawn up at EU level. Pesticides will then be licensed at national level on the basis of this list.

• Certain highly toxic chemicals will be banned unless exposure to them would in practice be negligible, namely those which are carcinogenic, mutagenic or toxic to reproduction, those which are endocrine-disrupting, and those which are persistent, bioaccumulative and toxic (PBT) or very persistent and very bioaccumulative (vPvB).

• For developmental neurotoxic and immunotoxic substances, higher safety standards may be imposed.

• If a substance is needed to combat a serious danger to plant health, it may be approved for up to five years even if it does not meet the above safety criteria.

• Products containing certain hazardous substances are to be replaced if safer alternatives are shown to exist. MEPs successfully demanded a shorter deadline for their replacement, of three years rather than five.

• Substances likely to be harmful to honeybees will be outlawed.

see plant protection products directive, 91/414/EEC

plutonic rocks (also called intrusive igneous rocks) resulted from magmas solidified below ground. When magmas crystallize deep underground they look different from volcanic rocks because they cool more slowly and, therefore, have larger crystals. Igneous rocks cooled beneath the Earth's surface are called intrusive rocks. The intrusive equivalents of basalt, andesite, and rhyolite are gabbro, diorite, and granite, respectively. In Hungary the Velencei mountain is composed of intrusive igneous rocks such as, granodiorite and diorite and the granite block in Mórágy was formed in similar conditions.

The underground crystallization stages of the magma are the following:
A. Preliminary crystallization stage (approx. 1100–1000 °C)
During the preliminary crsystallization stage ultrabasic and basic rocks are formed. The temperature decrease results separation of the silicate and sulphide melts. The preliminary crystallization gives economically important ore deposits: chromite, magnetite, ilmenite, platina, diamond and apatite.
B. Main crystallization stage (approx. 1000–700 °C)
In the main crystallization stage the magma solidification occurs. The olivine, pyroxene, amphiboles and the feldspars crystallize in parallel and finally the quartz.
C. Post magmatic stage (from approx. 700 °C)
The volatile containing residual magma is crystallised in this phase. The post magmatic stage includes three phases:

Pegmatite phase (approx. 700–550 °C): The mineral composition of the pegmatites crystallized in this phase is identical with that of the main crystallization phase however the pegmatites contain much larger crystals. The pegmatites in general occur in veins and are rich in rare elements such as stanium, uranium, thorium, boron, lithium, berillium, zirconium, titanium, tanthal.

Pneumatolitic phases (approx. 550–375 °C): The halogene rich solutions are chemically very active and thus are able to considerably modify the solidified rocks. This phase results various minerals such as quartz, fluorite, wolframite, turmaline.

Hydrothermal phase (from approx. 375 °C): The water diluted, solutions of the residual magma penetrated the cracks, voids of the rocks forming hydrothermal veins. During the hydrothermal phase mainly the following metals are concentrated: gold, silver, copper, lead, zinc, mercury and the iron, cobalt and nickel remained still in the residual solution.

the illegal killing of animals or fish, a great concern with respect to endangered or threatened species.

point and non-point sources of water pollution means the sources of pollutants and nutrients the input of which to waters is caused either by locally determined discharges (point source) or by diffuse effects being widespread over the catchment areas (non-point or diffuse sources).

polychlorinated dibenzofurans (PCDFs) are a group of halogenated organic componunds with a furane skeleton and chlor substituents different in numer. PCDFs occur as by-products in the manufacture of chlorinated organic substances, in the incineration of chlorine-containing substances such as PVC, in the bleaching of paper, and also from natural sources such as volcanoes and forest fires. Somilar to polychlorinated dibenzodioxins (PCDDs), they have been shown to bioaccumulate in humans and and animals, are known toxic, mutagenic, carcinogenic and reprotoxic.

the place where a hazardous substance comes from, such as a landfill, waste pond, incinerator, storage tank, or drum. A source of contamination is the first part of an exposure pathway. The source may ba a point or a diffuse source.

the direct or indirect introduction, as a result of human activity, of substances or heat into the air, water or land which may be harmful to human health or the quality of aquatic ecosystems or terrestrial ecosystems directly depending on aquatic ecosystems, which result in damage to material property, or which impair or interfere with amenities and other legitimate uses of the environment.

polychlorinated biphenyls (PCBs) are a class of chlorinated organic compounds, with 1-10 chlorine atoms bound to the biphenyl skeleton, which is the condensate of two benzene rings. The general chemical formula of PCBs is: C₁₂H_10-xCl_x. 

PCBs were used as dielectric fluids in transformers and capacitors, coolants, lubricants, stabilizing additives in flexible PVC coatings of electrical wiring and electronic components, they were used as pesticide extenders, flame retardants, hydraulic fluids, adhesives, anti-dust agents, coating of copy papers, etc.

PCB production was banned in the 1970s due to the high toxicity, mutagenicity and reprotoxicity. They are able to accumulate in the food chain. They are classified as POPs, Persistent organic pollutants.

polychlorinated dibenzodioxins (PCDDs), or simply dioxins, are a group of halogenated organic componunds with a dioxin skeleton and chlor substituents different in numer. Members of the PCDD family have been shown to bioaccumulate in humans and and animals, are known toxic, mutagenic, carcinogenic and reprotoxic. Similar group of toxicants are the the polychlorinated dibenzofurans (PCDFs). Dioxins occur as by-products in the manufacture of chlorinated organic substances, in the incineration of chlorine-containing substances such as PVC, in the bleaching of paper, and also from natural sources such as volcanoes and forest fires.

a polychromatic erythrocyte is an immature erythrocyte in an interstitial phase, that still contains ribosomes, so it can be distinguished from mature erythrocytes by applying selective staining.

substance consisting of molecules characterised by the sequence of one or more types of monomer units. Such molecules must be distributed over a range of molecular weights wherein differences in the molecular weight are primarily attributable to differences in the number of monomer units. A polymer compromises the following:
(a) a simple weight majority of molecules containing at least three monomer units which are covalently bound to at least one other monomer unit or other reactant
(b) less than a simple weight majority of molecules of the same molecular weight.
In the context of this definition a "monomer unit" means the reacted form of a monomer substance in a polymer. (Source: REACH, Article 3 (5))

PCR is a method for amplifying a DNA base sequence using a heat-stable polymerase and two 20-base primers, one complementary to the (+) strand at one end of the sequence to be amplified and one complementary to the (-) strand at the other end. Because the newly synthesized DNA strands can subsequently serve as additional templates for the same primer sequences, successive rounds of primer annealing, strand elongation, and dissociation produce rapid and highly specific amplification of the desired sequence. PCR also can be used to detect the existence of the defined sequence in a DNA sample.

Source: http://www.ornl.gov/sci/techresources/Human_Genome/glossary/glossary.shtml#modelorganisms

a multiple of the haploid chromosome number (n) other than the diploid number (i.e., 3n, 4n and so on). Polyploidy occurs in cells and organisms when there are more than two paired (homologous) sets of chromosomes. Most organisms are normally diploid, meaning they have two sets of chromosomes - one set inherited from each parent. Polyploidy may occur due to abnormal cell division during metaphase I in meiosis. It is most commonly found in plants.

Persistent Organic Pollutants

see permeable reactive barriers