The sorption and desorption of phosphate-P, ammonium-N and nitrate-N in cacao shell and corn cob biochars.
The sorption of PO4-P, NH4-N and NO3-N to cacao shell and corn cob biochars produced at 300-350°C was quantified. The biochars were used; (i) as received (unwashed), (ii) after rinsing with Millipore water and (iii) following leaching with Millipore water. In addition to sorption, desorption of PO4-P from the unwashed biochars was quantified. There was no sorption of PO4-P to either washed or rinsed biochars, but following leaching, both biochars adsorbed PO4-P and distribution coefficients (Kd L kg(-1)) were very similar for both materials (10(1.1±0.5) for cacao shell biochar and 10(1.0±0.2) for corn cob biochar). The BET surface area and micropore volume increased 80% and 60% for the cacao shell and corn cob biochars following leaching. After 60 d, 1483±45 mg kg(-1) and 172±1 mg kg(-1) PO4-P was released from the cacao shell and corn cob biochars. NH4-N was sorbed by both unwashed biochars, albeit weakly with Kd values around 10(2) L kg(-1). We speculate that NH4-N could bind via an electrostatic exchange with other cationic species on the surface of the biochar. There was no significant release or sorption of NO3-N from or to either of the biochars.
Norwegian Geotechnical Institute (NGI), P.O. Box 3930, Ullevål Stadion, NO-0806 Oslo, Norway. sarah.hale@ngi.no
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Hale
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Alling
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Martinsen
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Mulder
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Breedveld
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Cornelissen
D000042:Absorption; D064751:Ammonium Compounds / Q000378:metabolism; D002099:Cacao / Q000378:metabolism*; D002606:Charcoal / Q000378:metabolism*; D002623:Chemistry Techniques, Analytical; D004784:Environmental Monitoring; D005290:Ferric Compounds / Q000378:metabolism; D005308:Fertilizers / Q000032:analysis; D007214:Indonesia; D009566:Nitrates / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism*; D012987:Soil / Q000737:chemistry*; D013045:Species Specificity; D015024:Zambia; D003313:Zea mays / Q000378:metabolism*
D064751:Ammonium Compounds; D005290:Ferric Compounds; D005308:Fertilizers; D009566:Nitrates; D010710:Phosphates; D012987:Soil; C540010:biochar; D002606:Charcoal; C000499:ferric oxide