PM2.5 and PM10 emissions by abrasion of agricultural soils

Abstract

Abrasion of soil clods by wind erosion is one process contributing to fine particulate emissions, which degrades air quality. Little is known about the abrasion process that generates and emits particulate matter with aerodynamic diameter of less than 2.5 μm (PM2.5) or those less than 10 μm (PM10). Both PM2.5 and PM10 are regulated by the US-Environmental Protection Agency as health hazards. We used a laboratory wind tunnel to study the abrasion induced emissions of 15 aggregated soils from across the U.S. We subjected aggregated soils in trays as well as sets of aggregates placed on the wind tunnel floor to abrader sand (0.29 to 0.42 mm diameter) blown at 13 m s−1. PM2.5 and PM10 emissions were found to vary by soil type. Sandy soils had the poorest aggregation as well as lowest primary fine particulate contents and were found to have the greatest abrasion coefficients (AC) and highest emission of PM2.5 and PM10 under abrasion. By contrast, soils higher in clay had lower AC and emissions under abrasion. In addition, five of the soils tested had long-term histories of both conventional tillage (CT) and no-till (NT) management for paired comparisons of emission based on CT and NT managements. CT management tended to show higher AC values and greater abrasion emissions compared to NT management for the same soil, although only three of five management pairs were significant. Dry aggregate stability parameters were found to have an exponential relationship to AC with break force being a better AC predictor (R2 = 0.936) than dry stability (R2 = 0.894). We also developed equations that predict PM2.5 emissions as a fraction of PM10 emissions for aggregated soils (R2 = 0.932) and individual aggregates alone (R2 = 0.854). This research contributes to the understanding and prediction of PM2.5 and PM10 emission through the abrasion process.