Exposure to Light Elicits a Spectrum of Chemical Changes in Soil

Abstract

The significance of photochemically active solar radiation is well substantiated in Earth's air and water environments, but no broad connection has yet been ascertained between sunlight and the chemical properties of land surfaces. Since it is obvious that sunlight strikes Earth every day, an inquiry into this connection was made in a simple experiment with a diverse group of 20 soils. Light-induced alteration of most of the major elements in soil was evident, including significant changes in dissolved organic carbon, inorganic nitrogen, pH, phosphorus availability and sorption capacity, and soluble and mineral forms of iron, manganese, aluminum, silicon, and calcium. In many instances the extent of these changes could be predicted from initial values. This broad response to light attests to the vivid photochemistry of soils and has both pedological and edaphological implications that reach beyond the surface. The phenomena reported here affirm the opportunity for novel inquiries into the chemistry of soils and land surfaces in general.