Phytoremediation of heavy metal contaminated land
The mineral properties of natural zeolites can be used to provide a source of ammonium ions that enable nitrifying bacteria to develope very large populations. 
By composting poultry manure with crushed zeolitic tuff ammonia, produced during microbial decompostion,is surface adsorbed and ion-exchanged by the zeolite.
On completion of the composting process an odourless, dry material results which can be used to amend metal contaminated soils. Ammonium ions are back exchanged,
by potassium and calcium ions from the soil pore water, which become oxidized by nitrifying bacteria. The enzyme reactions which ensue produce nitrate and
surplus hydrogen ions. The hydrogen ion availability causes mobilization of cations in the soil pore water. In this way an adequate range of nutrient elements
are provided which can sustain plant growth even in the most metal polluted soils. This method of re-vegetation has proved to be cost effective as the high abundance
of the zeolite mineral clinoptilolite, found as a low temperature alteration product of volcanic glass in sedimentary deposits of tuffaceous rocks, make
this commodity readily available throughout the World. Further work on the microbiology of the system is in progress and is expected to yield results that will
make organo-zeolitic systems components of novel permeable reactive barriers that will be effective against industrial organic wastes in soils and groundwater.
For more information contact Peter J.Leggo at Department of Earth Sciences, University of Cambridge, UK. e-mail :
Posted: 10/02/2004 By: Peter Leggo