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| Titel |
Factors influencing biochar hydrophobicity and the influence of biochar content on the hydrological and erosional response of a silt loam under simulated rainfall |
| VerfasserIn |
Steve Aston, Alayne Street-Perrott, Stefan Doerr |
| 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 |
250096936
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| Publikation (Nr.) |
 EGU/EGU2014-12472.pdf |
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| Zusammenfassung |
| The production of biochar and its application to soil has the potential to make a significant
contribution to climate change mitigation while simultaneously improving soil
quality. Several authors have reported that biochar is hydrophobic. Few studies to
date have investigated the effects of biochar on soil hydrology and erosion during
rainfall.
Hydrophobicity was assessed by using a goniometer to measure water-droplet
contact-angles on the surfaces of biochar particles. Biochars were produced from Salix
viminalis, Miscanthus giganteus and Picea sitchensis feedstocks that were pyrolyzed at 350,
500, 600 and 800°C in a nitrogen-purged tube furnace. The influence of biochar on soil
hydrology was investigated using hydrophobic biochar produced from hardwoods pyrolysed
in a ring kiln at ~400°C. The biochar was ground and sieved to < 2 mm then added to a silt
loam at rates of 0, 5, 25 and 50 g kg-1. Water (30% of the water-holding capacity of the
unamended soil) was thoroughly stirred into each sample. Samples were stored at 21°C in
sealed containers in a dark room without natural light for 250 days. Aggregate stability and
the hydrological and erosional response of the soils were then assessed using a laboratory
rainfall-simulator. The organic matter content of soils and eroded sediments was measured by
loss-on-ignition.
The hydrophobicity of biochar was influenced both by the initial material (biomass type
and particle size) and the pyrolysis temperature. For each biomass type, hydrophobicity
was reduced with increasing pyrolysis temperature. This can be attributed both to
the destruction of alkyl functionalities and shrinkage of particles during pyrolysis,
smoothing their surfaces. A biochar content of 5g kg-1 did not affect the aggregate
stability of a silt loam, but biochar contents of 25 and 50 g kg-1 reduced aggregate
stability by 11 and 23% respectively. Lower aggregate stability accelerated formation
of surface seals in soils with high biochar content, so rainwater infiltration was
reduced, meaning runoff coefficients increased with increasing biochar content.
Sub-surface flow was reduced with increasing biochar content. Biochar content did not
affect the total amounts of sediment eroded by runoff and splashing from soils
of differing biochar content. However, correlations between rainfall duration and
erosion became weaker with increasing biochar content. The differences between the
organic matter content of eroded sediments and that of the plots from which they
were eroded tended to increase with increasing biochar content, suggesting that
biochar was increasingly preferentially eroded as its prevalence in the soil increased. |
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