Uptake of PAH compounds by specialty crops grown in biochar amended soils

1. Uptake of PAH compounds by specialty crops grown in biochar amended soils Eric Nooker Department of Soil, Water, and Climate University of Minnesota 6/14/13

2. Specialty Crops & Biochar Fruits, vegetables, tree nuts, and nursery crops Half of the value of U.S. crop production Safety issue with PAHs sorbed on biochar

3. PAH – Polycyclic aromatic hydrocarbon Composed solely of carbon and hydrogen atoms Have two or more fused aromatic carbon rings in the structure Simplest PAH is naphthalene Compose a large group of compounds (200+) Naphthalene Benzo(g,h,i)perylene

4. PAH Occurrence PAHs are among the most common organic pollutants Ease of atmospheric transport Universal environmental presence US EPA lists 32 of these PAHs as priority pollutants

5. PAH Formation Incomplete combustion Burning of fossil fuels: coal, diesel, gasoline Transportation sector Burning of biomass (e.g. wood, tobacco, brush fires) Cooking for meal preparation PAH production has also been confirmed during: Production of charcoal by pyrolysis Present in bio-oil from biomass pyrolysis

6. Natural Sources of PAH Present in: Fossil fuels Crude oil Shale oil Coal Coal tars Present in gases and ashes from: Forest fires Grassland fires Volcanoes Biological Routes: Microbial degradation of black carbons Microbial production during complex organic matter formation (soil humic substances)

7. Primary sources: Anthropogenic Largest stationary point source emissions: Paper mills Consumer wood product factories Petroleum refining

8. PAH Presence in Various Materials

9. PAH Sorbed to Black Carbon • Observed biochar range: 0.01 to 45 µg g-1

10. PAH range from 0.01 to 83 µg g-1 • Naphthalene was present on all biochars • Possible influence of production technique • Not statistically significant within this sample pool Pyrolysis influence on PAH MicrowaveAssistedPyrolysis Traditional Kiln/Soil Mound Fast Pyrolysis Unknown Slow Pyrolysis Hydrothermal

11. Materials and Methods Field and Greenhouse Experiments Field: One rate & biochar type Greenhouse: Multiple rates, types of biochar, and soils

12. PAH Extraction

13. Field Results Rosemount, MN

14. Specialty crops grown in biochar amended soils bio-accumulate PAH compounds Could be contaminated from rainwater splash of BC-soils

16. Greenhouse Treatments

17. Greenhouse Results Plant Growth Facility,University of Minnesota

18. Specialty crops grown in biochar amended soils bio-accumulate PAH compounds Levels are variable as a function of soil type and biochar

19. Biochar Weathering BC BC Control

20. Research Data Spectrum of specialty crop PAH uptake: Increases Decreases No changes PAH concentrations are influenced by: Feedstock moisture levels Presence of oxygen during pyrolysis, and post-cooling Post-production handling and storage Soil organic content Rate PAH sorbed biochar is applied

21. Uncertainties PAH contents of each biochar Human health impacts

22. Conclusions Plant PAH uptake depends on: Crop PAH content of the biochar PAH content of the original soil Native soil organic content PAH sorbed on biochar may elevate specialty crop PAH levels, especially at higher biochar application rates

23. Acknowledgements Minnesota Department of Agriculture Kurt Spokas Martin DuSaire Students: Abby Anderson, Amanda Bidwell, Ed Colosky, Mike Ottman, Tara Phan,Tia Phan, Rena Weiss Kia Yang, and Vang Yang