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  • I recommend using this slide rather than the previous one which included the high Cd Chicago Nu-Earth. This shows the remarkable effect of high Fe biosolids on Cd phytoavailability. Comparison at equal soil pH.

Kukier chaney-2005-effect of biosolids on phytoavailability of cd Kukier chaney-2005-effect of biosolids on phytoavailability of cd Presentation Transcript

  • Effect of Biosolids on Phytoavailability of Cd in Long-term Amended Soil. U. Kukier 1 , R.L. Chaney 2 , J.A. Ryan 3 , W.L. Daniels 1 , R.H. Dowdy 4 , and T. Granato 5 Virginia Tech, Blacksburg, VA; USDA-ARS Beltsville, MD; US EPA Cincinnati, OH
  • Experimental Design Soil were collected from paired long-term biosolids-amended and unamended soils from controlled field tests in Maryland, Minnesota and Illinois. Soil pH was adjusted to 6.5±0.2 in 0.01 M Ca(NO 3 ) 2 . Cd-salt added at rates 0, 2.5, 5.0, 7.5, 10 mg Cd kg -1 soil. Cd-nitrate was enriched in 111 Cd. Romaine lettuce was grown in the greenhouse for 35 days after transplanting. Four replications in randomized complete blocks.
  • New Test of Biosolids Cd Adsorption vs. Uptake (Kukier, Chaney, Ryan et al.)
    • Long-term Biosolids Amended Field Plots:
      • Add long ago (1978-1978)
      • Different sources of biosolids applied once.
      • Incorporated and then cropped regularly.
      • Each control and biosolids-amended soils amended with 111 Cd(NO 3 ) 2 at 0, 2.5, 5.0, 7.5 and 10.0 mg Cd/kg
    • Soils collected from plow layer in 2001:
      • Processed as moist soils to maintain soil biology.
      • Soil pH adjusted to 6.5 in 0.01 M Sr(NO 3 ) 2
      • Fertilizers added for normal growth of Romaine lettuce.
      • Lettuce and soil analyzed for Cd and 111 Cd, and other elements to evaluate long-term effects of biosolids.
  • Biosolids Application Sites, Rates, and Time Since Application Sampling Biosolids Cumulative Years Total Treatment Application since last Soil Cd Rate application Mg ha -1 mg kg -1 Hayden Farm Control 0 - 0.20 Maryland Heat Treated 224 24 1.16 Composted 672 24 1.51 Nu-Earth 50 22 1.76 Nu-Earth 100 22 3.44 Minnesota Control 0 - 0.33 Low Rate 60 20 2.75 Medium Rate 120 20 5.30 High Rate 180 20 8.50 Fulton Co. Control 0 - 0.23 Chicago Biosolids 643 16 32.1
  • Composition of Biosolids In the Different Field Plots Biosolids Cd Zn Fe mg/kg mg/kg % Heat-Treated 13.4 1329. 8.3 Composted 7.2 731. 4.1 Nu-Earth 212. 4140. 2.5 Twin Cities 140. 1890. 0.9 Chicago 263. 3660. 4.6 EPA-APL (mg/kg) 39. 2800. . EPA-CPLR (kg/ha) 39. 2800. .
  • Phytoavailability of Cd added to Long-Term Biosolids-Amended Soils.
  • Romaine Lettuce grown on Hayden Farm Control and Long-Term Biosolids Compost-amended (672 t/ha) soils with 0-10 mg Cd/kg, at pH 6.5 in Ca(NO 3 ) 2 . Reduced uptake/toxicity of Cd to lettuce (control vs. biosolids-amended).
  • Phytoavailability of Cd added to Long-Term Biosolids-Amended Soils pH=6.5
  • Phytoavailability of Cd added to Long-Term Biosolids-Amended Soils.
  • Phytoavailability of Cd added to Long-Term Biosolids-Amended Soils.
  • Phytoavailability of Biosolids Cd:
    • Biosolids Cd remains in labile pool for indefinite period, as does most soil Cd.
    • Persistent biosolids effect reduces uptake of Cd compared to untreated soils.
    • Phytotoxicity of added Zn is very effective limit to excessive bioavailable Cd in crops.
    • With high quality biosolids, bioavailable crop Cd is not increased even when Cd is increased.
    • High Cd:Zn ratio in biosolids promotes crop Cd uptake and bioavailability of crop Cd.
    • Subsistence rice diets had high influence on absorption of Cd by affected humans.
      • Polished rice is deficient in Fe, Zn and Ca for humans
  • Does increased consumption of fruits and vegetables increase risk from biosolids Cd?
    • Some claim that the EPA 503 Rule is not protective because it ignores higher Cd intake by highly exposed gardeners if they ate the current US Dept. Agr. recommended diet.
    • The USDA “Diet Pyramid” recommends eating more leafy and root vegetables, fruits and whole grains , some with high Cd uptake slopes, than earlier USDA/FDA/EPA model diets used in risk assessment.
    • These claims ignore the presence of Zn in biosolids which serves as a limit on maximum crop Cd due to Zn phytotoxicity, inhibits Cd uptake by crops, and inhibits Cd bioavailability to animals.
    • Because food Cd with 1:100 Cd:Zn ratio has essentially zero Cd bioavailability as found experimentally for lettuce and Swiss chard, increased garden foods consumption cannot comprise dietary Cd risk from gardens.
    • Cannot extrapolate from rice-Cd risks to other crops (e.g., wheat, lettuce) without data to show these foods can cause human risk when grown on soil with low Cd:Zn.
  • CONCLUSIONS
    • Biosolids provide long term protection
    • Cd is in labile form
    • Modern high quality biosolids contain low Cd levels and low Cd:Zn ratios and cannot cause high accumulation of Cd in crops.
    • Risk from Cd in crops depends on bioavailability of that Cd, and crop Zn inhibits Cd risk. Usual Cd:Zn ratio of <1:100 prevents undue Cd absorption in consumers.