Lithological controls of dissolved trace elements: carbonate versus silicate

Abstract

Trace elements in river waters can give information about chemical weathering and aqueous environments, but the systematics of trace elements in river waters have been poorly understood. Here, concentrations of dissolved trace elements were determined to investigate factors controlling their seasonal and spatial variations in the Han River Basin (HR), South Korea. Two major branches, the North Han River (NHR) and South Han River (SHR), differed largely in concentrations of their trace elements (e.g., As, B, Co, Li, Ni, and U), with the NHR having low concentrations and the SHR having high concentrations. This difference can be mainly attributed to the underlying lithology of the watersheds, namely, silicates in the NHR and carbonates plus clastic sediments containing black slate rich in trace elements in the SHR. Seasonally, concentrations of trace elements such as Al, Co, Fe, and Rb in the NHR were higher in summer, indicating that these trace elements exist as a colloid-borne form because of intensive physical weathering in the NHR. In contrast, the SHR showed little or no seasonal variation in concentrations of those trace elements.