Ohta,A., Imai,N., Terashima,S., Tachibana,Y., Ikehara,K., Okai,T., Ujiie-Mikoshiba,M. and Kubota R.(2007): Elemental distribution of coastal sea and stream sediments in the island-arc region of Japan and mass transfer processes from terrestrial to marine environments. Applied Geochemistry, 22, 2872-2891.

『日本の島弧域における沿海と河川堆積物の元素分布および陸域から海洋環境への物質輸送過程』


Abstract
 A total of 49 elements have been identified in 338 coastal sea sediment samples collected from an area situated off the Ise-Tokai region of Japan for a nationwide marine geochemical mapping project. The spatial distribution patterns of the elemental concentrations in coastal seas along with the existing geochemical maps in terrestrial areas were used to define the natural geochemical background variation, mass transport, and contamination processes. The elemental concentrations of coastal sea sediments are determined primarily by particle size and regional differences. Most elemental concentrations increase with a decrease in particle size. Some elements such as Ca, Mn, and Yb are found to exist in large quantities in coarse particles containing calcareous shells, Fe-Mn oxides, and felsic volcanic sediments. Regional differences reflect the mass transfer process from terrestrial areas to coastal seas and the influence of the local marine geology. An analysis of variance (ANOVA) reveals that for many elements, the particle size effect is predominant over regional difference. The mean chemical compositions of coastal sea sediments are similar to those of stream sediments in adjacent terrestrial areas and in the upper crust of Japan. This observation supports the fact that coastal sea sediments have certainly originated from terrestrial materials. However, the spatial distributions of elemental concentrations are bot always continuous between the land and coastal seas. The scale of mass movement observed in marine geochemical maps occurs at a distance of 20 km from the river mouth. A detailed examination of the spatial distribution patterns of K (K2O) and Cr concentrations suggests that terrestrial materials supplied through rivers are deposited near the shore initially, and then gravity-driven processes shift the sediments deeper into the basin. Contamination with heavy metals such as Zn, Cd and Pb was observed in coastal bays surrounded by urban and industrial areas. It is noteworthy that the areas with the highest concentration of these elements usually do not occur near the shore (not near the contamination source) but at the center of the bay. Unexpected low concentrations of Zn, Cd and Pb near shore may either be due to a decreased anthropogenic load in the most recent sediments or to dilution by unpolluted flood sediments.』

1. Introduction
2. Study area
3. Materials and methods
4. Geochemical map preparation
5. Results
 5.1. Spatial distribution patterns of elemental concentrations in the coastal sea and adjoining terrestrial areas
 5.2. Variation in elemental concentrations in coastal sea sediments with particle size
6. Discussion
 6.1. Regional differences found in elemental distributions
 6.2. Particle size dependence of elemental concentrations in coastal sea sediments
 6.3. Major factors controlling the distribution of elements in coastal seas
  6.3.1. Relationships between regional differences and particle size effects
  6.3.2. Analysis of variance (ANOVA) to test the effects of particle size and regional difference
  6.3.3. Interpretation of the results obtained by ANOVA
 6.4. Mass transport processes in the coastal sea
 6.5. Distribution of anthropogenic materials in coastal bays
 6.6. Comparison of elemental abundance in coastal sea sediments, stream sediment, and Japanese and continental upper crusts
7. Conclusions
Acknowledgements
References


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