Polynuclear Aromatic Hydrocarbon Content of Corn Stover Biochar Generated by Pyrolysis at Three Different Temperatures John W Scott, ISTC Senior Analytical Chemist In Collaboration With Mike Machesky and Tom Holm

“Priority” Polynuclear Aromatic Hydrocarbons (PAHs)

Project Goals Measure PAH content of corn stover biochar created by slow pyrolysis at 450 o C, 550 o C, and 750 o C Measure PAH content of same biochar samples after ageing Measure the sorption parameters of PAHs (pyrene) to fresh and aged biochars Estimate the bioavailability of PAH’s (pyrene) present in fresh and aged biochars by mild extraction conditions

Extraction and Analysis ASE ExtractionTurbovap ConcentrateGC/MS Analysis Dionex® ASE300 Parameters -Solvent: Hexane-Acetone (1:1) -Temperature: 100 o C -Pressure: 1500psi -Static Time: 5 min -Solvent to sample ratio: -Stover 20 ml/g -Stover BC 32 ml/g Turbovap Parameters -Final Volume: 1.0 ml -Temperature: 40 o C -Three Solvent Exchanges Varian® GC/MS Parameters -Detector: Saturn 2000 Ion Trap MS operated in selected ion mode -Column: Restek® Rtx-5MS (30 m x 0.25 mm x 0.25  ) -Injection: 300 o C, Spilt-less, 1  l -Oven:

Quality Control (QC) Parameters Sample Prep QC Parameters Samples Prepared in Triplicate Reagent Blanks Reagent Blank Spike Sample Matrix Spike Surrogate Addition of Terphenyl-d14 Analysis QC Parameters Continuing calibration check standards Analytical sample duplicates Analytical sample spikes Addition of five internal standards (isotope enriched PAHs)

Total Target PAH, mg/kg

Summary Part 1 The total target PAH’s measured in the corn stover biochar created at 450 o C and 550 o C are 1.4 mg/kg and 0.20 mg/kg, respectively The PAH profile for corn stover biochar created at 450 o C dominated by three and four cyclic ring species. The PAH profile for corn stover biochar created at 550 o C is more evenly distributed with higher ring substituted species. The total target PAH’s measured in the corn stover biochar created at 750 o C are mg/kg, however the results obtained are questionable The corn stover biochar created at 750 o C has a much stronger affinity for PAH’s than the biochars created at lower temperatures

PAH Content of Aged Biochar Corn stover biochars generated at the three temperatures (450, 550, and 750 o C) Samples aged for one month in open atmosphere Samples moistened to field capacity, however were dry at PAH extraction Aging was performed at three temperatures, -15 o C, 60 o C, and 110 o C

Summary Part 2 As the aging temperature is increased, surrogate recoveries for corn stover biochar created at 750 o C increased as well As the aging temperature is increased, the total target PAH content of the corn stover biochar created at 450 o C decreases Total target PAH content of the corn stover biochar created at 550 o C was not affected by the aging temperature

Acknowledgments Nandakishore Rajagopalan for Technical Assistance and Discussions Gerald Bargren “The Sample Prep Master!” Wei Zheng for Initiating Biochar work and Collaboration BK Sharma and Dheeptha Murali for Biochar Preparation ISWS Collaborators Michael Machesky, Thomas Holm, and Jillian O'Connell