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| Titel |
Physical and chemical effects of biochar on natural and artificial water repellent soils |
| VerfasserIn |
Ingrid Hallin, Peter Douglas, Stefan H. Doerr, Rob Bryant, Ian Matthews, Cecile Charbonneau |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250098754
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| Publikation (Nr.) |
 EGU/EGU2014-14458.pdf |
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| Zusammenfassung |
| Water repellency (WR) affects soils worldwide. Hydrophobic compounds accumulate in soil
through organic matter decomposition, microbial activity, condensation of organic
compounds during vegetation fires, or through anthropogenic impacts such as oil spills.
WR hinders vegetation establishment, which can lead to soil erosion and increased
runoff.
Biochar is currently being evaluated for its potential to increase soil carbon and as a soil
amendment. To date, the effect of biochar on water repellent soils has remained largely
undetermined. This study considered the potential of biochar as both a physical and chemical
amendment for water repellent soils by asking two questions: does adding biochar reduce the
observed degree of soil water repellency; and does biochar remove hydrophobic compounds
from soil?
The potential of biochar as a physical amendment to water repellent soils was evaluated
by mixing 5, 10, 25 and 40% (by weight) each of coarse and fine ground biochar with two
naturally water repellent soils and measuring the water drop penetration time (WDPT) for
each mixture. Biochar particles beyond the range of existing soil particle diameters increased
WDPT variability, which could be explained by increased surface roughness and the resulting
enhancement of water repellency effects through Cassie-Baxter interactions. Overall, fine
biochar was more effective at reducing water repellency: 25% w/w rendered both soils
studied wettable.
Removal of hydrophobic compounds by biochar was tested by mixing 1, 5, 10, 25 and
40% biochar with acid washed sand (AWS) coated with 1.2x10-5 mol octadecane
and octadecanoic acid (per gram AWS, which corresponds to approximately 50
monolayers hydrophobic compound per gram AWS). Each mix stood for 1 to 30 days
in a solution of pH 3, 6 or 9 before the AWS was extracted and the quantity of
hydrophobic compound remaining determined by infrared spectroscopy and/or gas
chromatography.
Biochar successfully removed the hydrophobic compounds, even in dry conditions and
independent of pH and exposure time. Results varied with the quantity of biochar added:
some removal was evident with 1% and 5% biochar additions, approximately 50% of material
initially deposited onto AWS was removed by 10% biochar, and ≥ 25% biochar removed
100% of the material present.
These results suggest that biochar can reduce WR effects in soils by creating wettable
pathways through water repellent soil and by removing hydrophobic compounds from soil
particles. |
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