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

2. 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

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

4. 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.

5. Types of Soil Crust
Physical crust
Chemical crust
Biological crust

6. Physical crust

7. 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

8. 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.

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

12. 50 cm
70 cm

13. 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

14. 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.

15. 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.

16. 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

17. The field experiment

18. no crust
with crust

19. 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.

20. Thanks

21. NDVI = (NIR-RED)/NIR+RED
Where
NIR is the reflectance flux between nm
RED is the reflectance flux between nm