Abstract
Novel carbon sequestration strategies such as large-scale land application of biochar may provide sustainable pathways to increase the terrestrial storage of carbon. Biochar has a long residence time in the soil and hence comprehensive studies are urgently needed to quantify the environmental impacts of large-scale biochar application. In particular, black carbon emissions from soils amended with biochar may counteract the negative emission potential due to the impacts on air quality, climate, and biogeochemical cycles. We investigated, using wind tunnel experiments, the particulate matter emission potential of a sand and two agriculturally important soils amended with different concentrations of biochar, in comparison to control soils. Our results indicate that biochar application considerably increases particulate emissions possibly by two mechanisms–the accelerated emission of fine biochar particles and the generation and emission of fine biochar particles resulting from abrasion of large biochar particles by sand grains. Our study highlights the importance of considering the background soil properties (e.g., texture) and geomorphological processes (e.g., aeolian transport) for biochar-based carbon sequestration programs.
Highlights
Soil erosion by wind and water, partly because the erosion potential of biochar and downstream impacts are unknown
The emissions from soils amended with sieved biochar (T4) were lower than control soils (Control) in the initial stages and higher when threshold conditions were attained (Fig. 1)
All controls and treatments showed a decline in PM10 emission at later stages of the wind tunnel tests even when the wind velocity was higher than the threshold for emissions, possibly due to limited supply of fine particles and abraders
Summary
Soil erosion by wind and water, partly because the erosion potential of biochar and downstream impacts are unknown. The particulate matter emissions (e.g., black carbon) from biochar-amended soils may counteract the negative emission potential[24]. Considering the potential impacts of black carbon aerosols on air quality, climate, radiation budgets and biogeochemical (carbon) cycles, comprehensive studies are urgently needed to assess the emission potential of biochar-amended soils[10,24]. We are not aware of any studies that have examined wind (aeolian) erosion and subsequent particulate emissions from biochar-amended soils. Using laboratory wind tunnel experiments, we investigated the particulate matter emission potentials of biochar-amended soils. We mixed biochar (unsieved or sieved to appropriate particle sizes and application rates of 5, 10 and 20% of the soil by volume) to a pure sand (Ottawa sand) and two agriculturally important soils (Ritzville silt loam and Warden sandy loam) and estimated the changes in fine particulate matter emissions (PM10 or particulate matter ≤1 0 μmin diameter) in comparison to control soils
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