Phytoremediation of Radionuclides: Effective Bioremediation Using the Common Sunflower

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  • Figure from 1996
  • Figure from Medvedev et al
  • Figure from Dushenkov et al 1999
  • Source: Dushenkove et al
  • Figure from Dushenkov et al
  • Phytoremediation of Radionuclides: Effective Bioremediation Using the Common Sunflower

    1. 1. Dominic Aebi and Caitlin Henderson-Toth March 31, 2011 CHEE 591 Environmental Bioremediation
    2. 2.  April 26, 1986  Reactor #4 at Chernobyl NPP melts down and explodes  Cause: human error ▪ Disabled cooling system during testing
    3. 3.   Radioactive material released into air, water, soil. Exclusion Zone  30 km radius around Chernobyl  Units  1 Bq = 1 decay / s  1 Ci = 3.7 x 1010 Bq
    4. 4.     Iodine Cesium Strontium Barium  Degradation product of Cs  Plutonium  Small amounts
    5. 5.  Without Intervention  200 yrs to farm within 30 km radius  20,000 yrs to inhabit land within 1.5 km radius  Contaminates Water, Food, Soil  Illegal farming in Exclusion Zone  Effect on animal life  Plant workers monitoring sarcophagus  Health Affects      Iodine irradiates thyroid Strontium causes bone cancer Cesium mimics potassium Plutonium can cause lung, liver cancer Birth defects
    6. 6.  Use of Plants, their associated microbes to accelerate remediation of organic and nonorganic contaminants  TCE, Hydrocarbons, PCBs   Cost Effective Option to use native/common plants  Sunflower  Poplar  Reed
    7. 7. Mechanisms      Phytodegradation Rhizosphere Remediation Phytostabilization Phytoextraction Phytovolotalization  Evapotranspiration Figure 2. The phytoremediation mechanisms. Pollutants may be stabilized or degraded within the rhizosphere, accumulated or degraded within the plant body, or transpired into the air .
    8. 8.  Chernobyl Cooling Pond 23 km2  1 km from reactor, dilute contaminant  Small Pond (75 m2)  9.2x106 Bq 137Cs  1.4x108 Bq 90Sr  Phytotech Inc. Researchers sampled water  Over 1000 plants tested  600 L sample treated  Conclude sunflowers rapidly/preferentially remove 137Cs/90Sr
    9. 9.  Ex Situ  8 wk old plants  Placed in 50 L water, for 48 hrs each  12 days - Removal 90% 137Cs, 80% 90Sr  In Situ     1.0 m2 raft 4-8 weeks floating 24 plants Anaylsis: 137Cs in roots, 90Sr in shoots ▪ Found that 55 kg dry weight Sunflower could remove all contaminants ▪ 60 Sunflowers employed for complete remediation
    10. 10.  Bad  Information limited on remediated levels  “Black Box” approach ▪ Limited understanding of mechanism ▪ No information on uptake of other contaminants  Pilot study short ▪ Questions as to seasonal variation in 137Cs, 90Sr uptake  Good  Sunflowers grow naturally in the Ukraine, acclimated, resist pestilence  Successful remediation (2nd attempt)  Valuable bioaccumulation coefficient obtained
    11. 11.  Bioaccumulation coefficients determined  Can calculate sunflower biomass required to remediate other ponds  After 4-8 wks  Sunflower accumulate 8x the 137Cs in roots as other plants  Shoots contain enough 90Sr to warrant quarrantine (2.5x106 Bq 90Sr /kg dry biomass)
    12. 12.  Dushenkov et. al., Env. Sci. Tech., 1999.  Goals 1. Find an additive to desorb 137Cs from soil 2. Find a plant which bioaccumulates 137Cs 3. Test additive for bioaccumulation stimulation 4. Test nascent bioremediation effectiveness in- situ
    13. 13.   Using Indian Mustard Improvement measured  More than control?
    14. 14.  Encasement  Prevents further contamination  Natural Attenuation  Adsorption/Encasement with minerals  Very long time period  Capping/Vitrification (ex situ)  Useful for very high concentrations  Expensive  Permeable Reactive Multibarriers  Efficient for removal of radionuclides in groundwater
    15. 15.   Chernobyl phytoremediation of WATER shows excellent promise Chernobyl phytoremediation of SOIL hampered by adsorption phenomena  Has shown minimal but measureable effectiveness  Phytoremediation  Versatile, Inexpensive, In situ, Natural  Apply lessons to present day Fukushima NPP disaster.
    16. 16.  Any questions?

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