Alkaline materials flux from unpaved roads: Source strength, chemistry and potential for acid rain neutralization

Data on elemental chemistry of unpaved road surface materials and surficial soils was used to estimate the potential flux of calcium, magnesium, potassium and sodium from open sources (unpaved roads, agricultural tilling, agricultural wind erosion) to the atmosphere. Results are summarized on a state-by-state basis (48 contiguous states). Preliminary calculations indicated that unpaved roads were the source of 90 per cent of the open source calcium flux in 37 states, and 90 per cent of the magnesium flux in 33 states. The domination of roads over soils was primarily due to the higher concentrations of these elements in road surface materials. Unpaved road contributions to potassium and sodium fluxes were less than 90 per cent in 27 and 28 states, respectively, reflecting the relative concentrations of these elements in soils and road surface materials. Fluxes presented were based on the rather imprecise data and equations available in the literature, and may be overestimates.