Dust emission characteristics of unpaved field roads in the black soil region of Northeast China based on PI-SWERL experiments

Background Unpaved road dust represents a significant source of atmospheric particulate matter. The black soil region of Northeast China is a crucial grain production base. Unpaved roads are subjected to compounded erosion forces, leading to severe soil degradation and ecological risks. Wind-induced dust emissions from widespread unpaved roads not only threaten agricultural production and public health but also amplify surface erosion through synergistic interactions with seasonal processes, so thorough research and control measures are urgently needed. However, quantifying dust emission potential under dynamic field conditions remains challenging due to limitations in conventional sampling methods. Methods This study employed a Portable In-Situ Wind ERosion Lab (PI-SWERL) to systematically quantify real-time PM10 emission fluxes from typical unpaved roads in the black soil region of Northeast China. Field experiments target three road types: the bare soil road, gravel roads and the hardened gravel road which is subjected to leveling and solidification. Dust emissions are measured under controlled friction velocities, simulating natural wind shear stresses. Statistical analyses differentiated emission mechanisms (saltation and aerodynamic entrainment). Results The PM10 emission flux demonstrate a positive correlation with friction velocity, and there exist highly significant disparities in the dust emission fluxes measured under varying wind speeds. It is suggested that the bare soil road exhibits the highest potential for dust emission among the types investigated. Specifically, at a friction velocity of 0.56 m·s-1, the dust emission flux of the bare soil road is measured to be in the range of 0.43 to 9.51 mg·m-2·s-1. In contrast, when a higher friction velocity reaches 0.86 m·s-1, the dust emission flux of gravel roads is determined to be between 0.04 and 1.54 mg·m-2·s-1. The dust emission flux of the bare soil road at a lower friction velocity exceeds that of gravel roads at a higher friction velocity by 1-2 orders of magnitude. The dust emission types of unpaved roads within the study region can be categorized into four distinct types, based on comprehensive analysis of PM10 concentration and saltation particle variation trend, and dust emissions in this region primarily result from particle saltation and aerodynamic entrainment. Notably, the hardened gravel road exhibits the lowest emission fluxes ranging 0.09-0.18 mg∙m-2∙s-1, indicating that hardening measures effectively reduce dust emissions and play a critical role of road hardening in dust suppression. Conclusions This research quantifies the dust emission potential of unpaved roads in the black soil region of Northeast China and elucidates the dynamic processes and characteristic differences in dust emission across different road surface types. These findings provide a theoretical basis for optimizing wind erosion control technologies targeting unpaved agricultural roads in erosion-prone black soil ecosystems.