Soils are mixtures of material derived from substrate weathering, plant decomposition, and solute and particulate deposition from the atmosphere. The relative contribution from each source varies widely among soil types and environments. Atmospheric deposition of marine and mineral aerosols can have a major impact on the geochemistry and biogeochemistry of the Critical Zone. Some of the best-studied examples are from ocean islands because of the strong geochemical contrast between bedrock and atmospheric sources, but for the most part continental areas are more severely impacted by atmospheric deposition. With dust flux greater than 10% of the global river sediment flux, deposition from the atmosphere plays an important role in the biogeochemistry of soils worldwide.