INVESTIGATION OF A SYNTHETIC SOIL FOR CREATED WETLAND ENHANCEMENT

Wetland loss is a major global environmental problem. One method of combating wetland loss is to produce created wetlands when natural systems are destroyed or degraded. Mitigation banking systems are in place in numerous states where wetlands destroyed by residential and commercial development must be replaced by created wetlands. In many areas the constructed wetlands do not perform as well as their natural counterparts and as a consequence methods are being sought to improve constructed wetland performance.

One key issue is that soils material used in created wetlands do not have the same physical or mineralogical properties as their natural counterparts. This investigation has devised a synthetic soil system at the beaker and bench scale that may be used to produce more effective wetlands that develop in sand-rich environments with ortstein-like soils. Solutions of silicic acid are introduced to mixtures of Fe powder and quartz-rich sand at ambient temperature. Solutions are allowed to evaporate over a period of days and solutions are refreshed. A progressive Munsell color change occurs from 7.5 YR 8/2 to10 YR 4/6 with this progressive reaction. The result is synthetic sandy soil material that is rich in amorphous and poorly crystalline Fe-oxyhydroxides. X-ray diffraction data indicate that lepidocrocite and goethite are common mineral constituents. Transmission electron microscopy (TEM) investigation indicates that particle morphologies and chemical compositions of individual oxyhydroxide particles in the synthetic soil are similar to those observed in their natural counterparts. TEM chemical mapping reveals particles have variable amounts of Si content. The mineralogy of the synthetic soil is broadly similar to natural ortsteins and hydromorphic soils associated with temperate wetland environments.

Materials involved in the process are inexpensive and there are low energy requirements involved in the production of these materials making them a green technology. This technology is patent pending.