Bulk percipitation displays the combined effects of all water soluble components of precipitation. Dust from the earth's surface is commonly assumed to be alkaline; it is commonly reported in the literature as a constituent of the atmosphere and of precipitation. Alkaline and alkaline earth cations in precipitation are typically attributed to such sources as "soil dust", "terrestrial dust" and "cystal dust". Specific sources include soil, from which wind erosion and filling operations, and also unpaved roads, from which dust is raised by vehicle traffic.