Particle Size Effects in Gaussian-Based Air Quality Modeling of Mine Dust: A Review with Mechanistic Numerical Demonstration

The environmental impacts of mine dust in mining operations can be mitigated through improved prediction of its spatial distribution using dispersion models, particularly Gaussian-based air quality models. However, Gaussian-based models often predict concentrations that differ substantially from observed mine dust behavior, because dust properties and transport mechanisms vary markedly with particle size. In this study, particle-size-related mechanisms for dust dispersion behaviors were classified as dry/wet deposition, turbulent diffusivity, erosion, hygroscopicity, or agglomeration, and their effects on dust dispersion behaviors and effective simulation methods were reviewed. Currently, the most clearly established particle size influence is on deposition, especially for coarse dust emitted from mechanical mining processes. Other mechanisms, including erosion, hygroscopicity, and agglomeration, are more relevant to finer dust below 2.5 µm or in the submicron range. This study proposes that wind erosion, mainly saltation flux, can also be integrated into Gaussian dispersion models as near-ground boundary flux terms. Hygroscopic and agglomeration effects can be assessed using relative humidity and simplified particle size redistribution assumptions near dust emission sources. In particular, incorporation of agglomeration mechanisms may begin with a simple bimodal assumption: the agglomeration of PM2.5 into PM10. This can be incorporated into a modified Gaussian deposition equation. Finally, the size dependence of the turbulent diffusivity coefficient is relatively insignificant, so the diffusivity values can be regarded as constants. These findings provide a mechanistic basis for improving mine dust prediction and environmental management in open-pit mines, haul roads, tailings areas, and stockpile environments.