Phytoremediation

Phytoremediation Phytoremediation or is a branch of bioremediation techniques and commonly referred to the remediation of polluted and contaminated soils and groundwater using plants. This is a so-called in-situ - method, since the treatment of the soil or water takes place on site. Currently, phytoremediation is in the development phase. One differentiates various methods:

Phytoextraction

Phytoextraction is a remediation method, are used in the Pflanzenkultivare, absorb the contaminants from the soil and reinforced in their biomass accumulate in high concentrations (so-called hyper- accumulators). The pollutants can thereby be stored in the roots, as well as in the aboveground biomass. These plant parts are then removed at harvest after the growing season (ie, depending also removal of roots ) and is depending on the load of a suitable disposal; the combustion is in addition to other processes only one of the possible methods of disposal. The biggest advantage of phytoextraction is opposite va the soil exchange ( removal ) with deposition in a landfill (dig and dump ) and acid wash that the soil functions are retained. This is especially for the rehabilitation of arable land (eg contamination with heavy metals by sewage sludge ) is of great importance.

The problem was, until then, however, that many studied hyperaccumulators such as thale cress in Central Europe are very small and grow very slowly. This was already in newer multi-year series of experiments, for example, circumvented zinc loaded and not too acidic surfaces, characterized in that particularly selected cultivars of Central European crops ( such as tobacco and sunflower ) with a high biomass, but only moderate enrichment of heavy metal was used. Overall, these cultivars extract then net more than hyper - accumulators with relatively low biomass. In addition, the environmentally sound disposal is so much easier, especially when it is in the extracted substances are substances essential in animals and humans (such as zinc).

It is important to take into account that the soil properties ( especially as the pH ), the height of the floor covering, the micro- climatic conditions and the type of fertilizer have a significant impact on the success of phytoextraction. Alkaline soils are doing worse than slightly acidic soils. Properly executed phytoremediation acts not only schadstoffabreichernd, but also stabilizes the pH - value ratios and promotes the desired crumbling.

Goal of phytoremediation is not necessarily the distance to high overall levels eg otherwise be of naturally occurring substances in the soil such as zinc in slag heaps. You can also serve only to remove excessive soluble contents and the simultaneous suppression of the mobilization from the total ( mainly poorly soluble ) pollutants in the soil. Thus, an otherwise much more expensive and not always environmentally beneficial soil exchange is replaced. In the sense of "smart" Remediation phytoremediation is not the panacea for all threats to soil, but a complement to the other soil remediation process. Generally increases with accumulator cultivars above certain concentrations of pollutants as a result of the accumulation rate of toxicity ( necrosis) sharply. Whether Phytoremediation can be used successfully, therefore always requires a careful clarification of the specific local conditions by experts before use.

Also can be reduced by cultivating the dickstieligen water hyacinth, the content of cyanide and copper in waste water of gold mining.

Phytodegradation

In Phytodegradation the ( usually organic ) pollutants which the plant, does not accumulate as in the phytoextraction but chemically modified and thus inactive. Also include processes in which the pollutants are not absorbed by the plant, but only the plants stimulate the degradation of the pollutants by micro-organisms, for Phytodegradation. This stimulation is achieved on the one hand by the better Assimilatversorgung of microorganisms due to the penetration of the soil ( rhizodeposition ) and on the other by certain substances that are excreted by the plant roots ( root exudates ).

Phytomining

As phytomining refers to the extraction of metals using plants. Unlike phytoextraction, this method applies only to metals. These metals can be recovered from the combustion residue again. So far, this process is only to reduce the cost of phytoremediation by winning the extracted metals something. However, it is researched from using phytomining also for ore mining.

Phytovolatilisation

When Phytovolatilisation the plant takes the pollutants with the roots and gives them through their aboveground organs in the air again. This may result in the plant biochemical transformations in volatile forms of pollutants. In the case of mercury, this is done by methylation of mercury to methyl mercury by the plant. Methyl mercury is volatile and can therefore be discharged from the plant into the air.

Rhizofiltration

Rhizofiltration is a process in which the plants are not directly involved in the clean-up but contribute through their root system prevents microbial activity is increased in the soil. The pollutants are then degraded by microorganisms. Based on the groundwater remediation, Rhizofiltration also means generally the absorption and condensation on the plant roots and / or uptake and accumulation in the roots.

Phytostabilisierung

Phytostabilisierung is not a remediation process, but is only used to backup the soil. In general, the mobility of contaminants is reduced. A dense grass cover protects the soil from erosion. The superficial removal of pollutants by the wind and the rain is prevented. At the fine roots can adsorb pollutants, they are thus held in the soil and their leaching into groundwater is reduced. Through the transpiration of plants, there is a largely upwardly directed stream of water, this can also prevent leaching of contaminants into the groundwater. In addition, certain substances that are secreted by the plant roots lead to immobilization of pollutants (eg precipitation of heavy metals).

Bioaugmentation

Swell

• Terry Norman, Gary Banuelos: Phytoremediation of Contaminated Soil and Water, CRC Press LLC, 2000..
• Puschenreiter & Wenzel ( 2003): Plants as metal eaters, in: . Rural, online trade journal of the Federal Ministry of Agriculture, Forestry, Environment and Water Management, Edition 01 /2003