Biochar amendment for enhanced infiltration and aggregation of compact urban soils
Date
2021
Authors
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Publisher
University of Delaware
Abstract
Urban development results in soil compaction and conversion of pervious lands
into impervious surfaces, which decreases soil infiltration and increases stormwater runoff
volume and associated pollutants. To alleviate the problem, biochar – a porous
carbonaceous material – may be amended to existing soils next to impervious surfaces such
as parking lots and roadways to increase stormwater infiltration. To assess the impact of
biochar amendment at the field scale, a commercial wood-based biochar was amended with
soil adjacent to urban impervious surfaces at four sites- two sites receiving stormwater
runoff from parking lots and two sites from Interstate-95. The effectiveness of biochar to
enhance stormwater infiltration in test sites was assessed periodically up to 1.5 years by
measuring saturated hydraulic conductivity (Ksat). Factors affecting soil Ksat such as soil
compaction, vegetation density, soil water retention capacity, water-stable aggregate
fraction and organo-mineral content were measured in undisturbed field soil cores at
different ages (up to five months for highway soils and up to 15 months for parking lot
soils) of the treatment systems. Results showed that despite the spatial (soil texture) and
temporal (season) variability, the geometric mean Ksat of 4% (w/w) biochar amended soils
was 1.8 to 4.6 times greater than that of undisturbed soils. The building blocks of water stable aggregates, the organo-mineral content, in 4% biochar amended soils were on
average 1.7 times and 3.9 times higher than undisturbed soils after five months and 16
months, respectively. Consistent with these data, water stable aggregate fractions in 4%
biochar amended soils were on average 27.2% and 47.3% greater than in undisturbed soils
after five months and 16 months, respectively. For the first time, this study showed that
biochar is effective in enhancing infiltration in compact roadway soils causing increased
hydraulic conductivity, improved water retention and improved soil structure through
biochar mediated aggregation.
Description
Keywords
Biochar, Organo-mineral association, Soil aggregation, Stormwater infiltration, Urban soil