By controlling the mobility of nutrients and contaminants, using phyto-geochemical technology, we can support plants in growing in polluted environments.
We like to know what role phyto-geochemical technology can play in growing plants on strongly contaminated soil, not necessarily promising a rose garden, but at least improving success and efficiency of phytoremediation.
Phytoremediation uses higher plants to remove, immobilize or degrade contaminants such as metal(loid)s in soil and water and two approaches can be distinguished (Bolan et al., 2011):
- Phytoextraction aims at cleaning soil and water by the uptake of contaminants and their storage in plant tissue. The contaminants are removed by harvesting the plants.
- Phytostabilization aims at immobilizing contaminants by roots and plant cover, preventing their percolation to groundwater and their spreading by wind and water erosion.
Nutrients and contaminants enter the plants via the rhizosphere, a volume of soil or water that envelopes the roots in a few millimeters thin layer. Their mobility and uptake depend on the composition of soil and the activities of the plant and associated microbes (mycorrhizal fungi and bacteria) in the rhizosphere.
The mobility and availability of, for instance, metal(loid)s is strongly regulated by the pH of the pore water of the soil. The plant influences the pH by releasing fluxes of H+ or OH-, counterbalancing the uptake of cations and anions, respectively (Tang and Rengel 2003).
The mobility and availability of metal(loid)s is also defined by the charge of soil particles with a high surface per weight ratio. Fine-grained organic matter and clay minerals show strong capacity for adsorption and exchange of cations or anions, expressed in the Cation- and Anion Exchange Capacities (CEC and AEC) of the soil (Bolan et al., 1999).
Plants have trouble distinguishing between useful nutrients (e.g. K+, Ca2+, PO43-) and hazardous contaminants (e.g. Tl+, Cd2+, AsO43-) of the same charge and similar size (Reid and Hayes, 2003).
With phyto-geochemical technology we aim at supporting plants growing on contaminated soil by influencing the pH, CEC, AEC and bio-availability of nutrients and contaminants, using inorganic amendments (e.g. liming materials, phosphate compounds and clay materials) and organic amendments (e.g. topsoil, compost, manure, waste water treatment biosolids, peat and biochar).
We like to know: What amendments are required for effective phyto-geochemical technology and; How to administer amendments for efficient phyto-geochemical technology?