Using of biological soil crust for surface stabilization 1A. Dody 2E. Zaady 1 BGU, Beer Sheva, ISRAEL 2 ARO Gilat, ISRAEL

Outline Objective Background Types of soil crusts What is Biological soil crust (BSC) Advantages of BSC Development of crust Indexes to prove growing of BSC Conclusions

Objective Providing a new and environment friendly method for capping waste disposal sites. This is by promoting colonization of local BSC’s organisms

Background In arid and semi arid zones, near surface disposal sites are sensitive to surface geomorphological processes (erosion). In disturbed areas, wind and overland runoff expose and transfer the cap layers causing hazardous condition.

Types of Soil Crust Physical crust Chemical crust Biological crust

Physical crust

BSC with mosses and lichens Rodent hole under BSC Contact between BSC and sands Rodents dig the hole in the interface between sand soil and crust

What is Biological Soil Crusts (BSC) BSC are predominantly composed of living organisms; cyanobacteria, soil bacteria, algae and lichens. Mosses may be found in more humid areas. BSC are usually between 1 and 15 mm thick and its components can be found up to 70% of the arid or semi-arid areas of the world. BSC species composition varies from place to place, due to rainfall amounts.

How BSC looks like from space by Landsat image (703 km) ?

50 cm 70 cm

Advantages of BSC over WDS Reducing water percolation into the WDS Reducing surface erosion Longevity and durability of the biological components. Survive in climate changes No maintenance is needed The BSC does not replace any other EBs

Longevity and durability of the BSC Crusts are comprised of species, which have adapted to the local ecosystem, facilitating maintenance. Evidence for the cyanobacteria existence ~3.5x109 yr ago, emphasizes successful adaptation to extreme global changes. Under sever dryness all the organisms building the crust are dormant, losing 70% of their weight (of water). Moisture will reactivate them.

Development of the crust Filamentous cyanobacteria, such as Microcoleus sp., are the primary colonizer, especially in crust formation in arid and semi arid environments. Algae and cyanobacteria produce mucilaginous polysaccharides that seal the soil surface and form the crust. Soil particles are immobilized by being both glued to each other and entrapped in a web of cyanobacterial filaments. Green algae, lichens or mosses are interwoven into the crust further and strengthened it.

Indexes used to prove growing of BSC The BSC succession over the target sites will be studied in 5 distinct forms: The depth of the crust The hardness of the crust Amount of polysaccharides in the crust NDVI (remote sensing technique) Infiltration rate

The field experiment

no crust with crust

Conclusions Using environment friendly BSC at radioactive or hazard waste disposal sites can be effective for reducing dispersion of contaminants to the environment: reducing surface erosion of cap layers. reducing water percolation, preventing the leaching of the waste material. Long term protection due to the longevity and durability of the BSC in comparison to other geo-textile layers.

Thanks

NDVI = (NIR-RED)/NIR+RED Where NIR is the reflectance flux between 950-1100 nm RED is the reflectance flux between 650-700 nm