Elemental composition of sediments in Lake Jinzai, Japan: assessment of sources and pollution.

Bottom sediments from Lake Jinzai in southwest Japan were analyzed to determine their chemical compositions and to assess the potential for ecological harm by comparison with sediment quality guidelines. The pollution status of lake sediments was evaluated by employing contamination factor (CF), pollution load index (PLI), and geoaccumulation index (I(geo)), focusing on a suite of elements in lakebed and core sediments. Elevated concentrations of As, Pb, Zn, Cu, TOC, N, and P were present in several layers of the upper core and other surface sediments. The elevated metal concentrations are likely related to the fine-grained nature of the sediments, reducing bottom conditions produced by abundant organic matter, and possibly minor non-point anthropogenic sources. Moreover, correlations between the concentrations of trace metals and organic carbon, nitrogen, phosphorus, and iron, suggest that these elements play a role in controlling abundances. Calculated CF, PLI, and I(geo) indicate that the sediments are strongly polluted with respect to As, moderately to strongly polluted with Zn, and moderately polluted with Pb and Cu. Metal concentrations exceed the New York State Department of Environmental Conservation (NYSDEC) lowest effect level and the Canadian Council of Ministers of the Environment (CCME) interim sediment quality guidelines that indicate moderate impact on aquatic organisms in the study area.

Recent sedimentary environment of coastal lagoon in southwestern Japan: evidence from major and trace elements.

A geochemical study of the bottom sediments of Lake Shinji and the River Ohashi in southwestern Japan was carried out to determine their elemental compositions and to evaluate the pollution status of lake sediments by employing enrichment factor (EF), pollution load index (PLI), and geoaccumulation index (Igeo). Present-day water quality was also assessed. Results showed that the water quality of Lake Shinji contrasts slightly between the upper and lower parts. The chemical composition of the sediments, as measured by X-ray fluorescence, included major and trace elements and total sulfur (TS). Average abundances of As, Pb, Zn, Cu, Ni, and Cr in the Shinji sediments were 10, 29, 143, 27, 19, and 54 ppm, respectively, compared to 6, 18, 57, 16, 10, and 37 ppm in the river sediments. Based on the EF, PLI, and Igeo, the lake sediments are moderately to strongly polluted with respect to As, moderately polluted with Pb, Zn, and Cr, and unpolluted with Cu and Ni. The high EF and Igeo for As, Pb, and Zn in the lake sediments indicate that metal concentration has occurred in Shinji. Increases in the abundances of these metals are likely related to the fine-grained nature of the sediments, reducing conditions of the bottom sediments, enrichment in organic matter, and possibly a minor contribution from non-point anthropogenic sources. Trace metal contents are strongly correlated with Fe2O3 and TS, suggesting that Fe oxides and sulfides play a role in controlling abundances in the investigated areas.

Abundances, distribution, and sources of trace metals in Nakaumi-Honjo coastal lagoon sediments, Japan.

Bottom sediments from Nakaumi Lagoon and the Honjo Area in southwest Japan were analyzed to determine their geochemical compositions and to assess potential impacts by comparison with sediment quality guidelines. Present-day water quality was also assessed. Results showed that the water quality of Nakaumi Lagoon and the Honjo area contrasts between their upper and lower parts. Average abundances of As, Pb, Zn, Cu, Ni, and Cr in the Nakaumi sediments were 12, 25, 135, 32, 21, and 46 ppm, respectively, compared to 10, 24, 110, 26, 20, and 38 ppm in the Honjo area. All averages are greater than those of the upper continental crust. The elevated metal concentrations are probably related to the fine-grained nature of the sediments, reducing bottom conditions produced by abundant organic matter and possibly minor non-point anthropogenic sources. Trace metal contents are strongly correlated with Fe2O3, suggesting that Fe oxides play a role in controlling abundances. Metal concentrations exceed the NYSDEC lowest effect level and CCME interim sediment quality guidelines that indicate moderate impact on aquatic organisms. Average abundances of As and Zn are comparable to the Coastal Ocean Sediment Database threshold, whereas maximum concentrations exceed that value, indicating that the concentrations of these metals are potentially toxic. These enrichments suggest that regular monitoring may be desirable even where no point sources of metal pollution exist.