PARTICULATE MATTER EMISSIONS FROM BIOCHAR-AMENDED SOILS: A POTENTIAL HEALTH HAZARD?

Novel carbon sequestration strategies such as large-scale biochar application may provide sustainable pathways to increase the terrestrial storage of carbon in agricultural soils. As biochar has a long residence time in the soil, understanding the environmental impacts of biochar addition needs to be investigated. While many of the beneficial results of biochar application have been demonstrated in laboratory and field studies, the potential negative impacts of widespread biochar application to soils have not been satisfactorily examined. Very few studies have investigated the impacts on soil erosion, in particular on wind (aeolian) erosion and subsequent particulate emissions. We used a combination of wind tunnel studies and laboratory experiments to investigate the dust emission potential of biochar-amended agricultural soils. We added biochar (unsieved or sieved to appropriate particle size; application rates ranging from 1 - 5 % of the soil by weight) to three soil types (sand, sandy loam, and silt loam) and estimated the changes in threshold shear velocity for wind erosion and dust emission potential in comparison to control soils. Our results show that biochar application significantly increased particulate emissions and that the intermediate concentrations of biochar lead to higher particulate emissions. Furthermore, abrasion by sand grains was found to be a major mechanism generating fine biochar particles that are highly susceptible to wind erosion. While biochar application presents potential for improving soil quality and offsetting greenhouse gas emissions, the increase in airborne dust can impact human health, especially since contaminants can be adsorbed and transported through biochar particles.