Abstract
Seventy-three sediment samples were collected in Sendai City, and their bulk components and soluble components in 0.1N HC1 were analyzed by AAS, ICP-AES and ICP-MS. The data are expressed graphically on geochemical maps and used to estimate natural background of respective elements and find the pollution enhanced by human activity. The characteristics of geochemical maps for bulk components reflect the geology of background area. The elemental concentrations are controlled mainly by the underlying mineral substrate in the study area such as sedimentary rock with acid tuff and andesite-basalt lava. The geochemical maps of soluble components in 0.1N HC1 have the similar trends to those of bulk components. Although the unstable phase is only a fraction of the stream sediments, the 40-70% of the contents of Cu, Zn and Pb in stream sediments is attributable to this phase. The application of geochemical maps to environmental assessment reveals the influence of agricultural pollution in the area of rice field where P concentrations in the bulk and acid soluble components are very high. However, we did not find any anomalous distributions of elemental concentrations in the urban area where many anthropogenic materials are found in stream sediments and river water is tainted by human activity.
