PM2.5 and PM10 emissions by breakage during saltation of agricultural soils

Abstract

Breakage of soil aggregates during saltation is one process that contributes to the generation of fine dust emissions by wind erosion. Fine dust is also known to affect human respiratory health. Of particular hazard are particles of aerodynamic diameter less than 2.5 μm (PM2.5) and those less than 10 μm (PM10), both of which are regulated by the US-Environmental Protection Agency. We used a laboratory wind tunnel with wind at 13 m s−1 to investigate the emission parameters for PM2.5 and PM10 caused by saltation-size aggregates (0.15 to 0.84 mm) from 15 soils with a wide range in properties from across the U.S. The coefficient of breakage (Cbk) was found to vary inversely with clay content, with the largest values found for soils with the greatest sand content. Only one soil with the highest sand content was found to be statistically different in total suspension flux from breakage (Gssbk). We did not find a relationship between soil texture or organic matter and the soil fraction of PM2.5 and PM10 from breakage (SF2.5bk and SF10bk). In addition, five of the soils tested had long-term histories of either conventional tillage (CT) or no-till (NT) management for paired comparisons of emission based on management. CT soils tended to have higher sand, lower silt and lower organic matter than NT management. Management significantly affected Cbk for four of the five soil pairs where the three with the highest clay content having lower Cbk under NT than CT management and the fourth pair had lower Cbk under CT management. Long-term NT management showed significantly less vertical suspension flux from breakage during saltation (Gssbk) than CT management for only two of the five paired soils. A linear relationship predicted PM2.5 emissions from breakage as a fraction of PM10 emissions for the mineral soils tested (R2 = 0.972). This research contributes to our understanding of PM2.5 and PM10 emission during saltation. It also provides parameters that will improve fine dust simulation in the Wind Erosion Prediction System (WEPS) model.