Volume 5 has several objectives. The first is to present an overview of the composition of surface and ground waters on the continents and the mechanisms that control the compositions. The second is to present summaries of the tools and methodologies used in modern studies of the geochemistry of surface and ground waters. The third is to present information on the role of weathering and soil formation in geochemical cycles: weathering affects the chemistry of the atmosphere through uptake of carbon dioxide and oxygen, and paleosols (preserved soils in the rock record) provide information on the composition of the atmosphere in the geological past.