Ecological shifts due to anthropogenic activities in the coastal seas of the Seto Inland Sea, Japan, since the 20th century.

Multiproxy analyses were conducted using sediment cores in a low-polluted coastal site (Hiuchi-nada) in the Seto Inland Sea (SIS), Japan. Heavy metal and organic pollution peaked in the 1960s and the bottom environments have ameliorated since the 1980s due to several environmental regulations. First ecological shifts in meiobenthic ostracodes and diatoms occurred in the 1960s due to the initiation of eutrophication. Then, a second ecological shift occurred in the 1980s due to the amelioration of the water and the bottom quality. A compilation of similar analytical results in the coastal seas of the SIS reveals three types of ecological and environmental history since the 20th century. The environmental improvement since the 1980s affects the ecosystems, in particular, in a low-polluted bay. However, ecological compositions are different from those prior to the 1960s, suggesting that the ecosystem was not recovered but changed into the next stage in the SIS.

Spatial distribution, enrichment, and source of environmentally important elements in Batticaloa lagoon, Sri Lanka.

The present paper is the first documentation of distribution and contamination status of environmentally important elements of superficial sediments in the Batticaloa lagoon that is connected to the largest bay of the world. Surface sediment samples were collected from 34 sites covering all over the lagoon. Concentrations of elements such as As, Cr, Cu, Fe, Nb, Ni, Pb, Sc, Sr, Th, V, Y, Zn, and Zr were measured by X-ray florescence analysis. Geochemically, the lagoon has three different zones that were influenced mainly by fresh water sources, marine fronts, and intermediate mixing zones. The marine sediment quality standards indicate that Zr and Th values are exceeded throughout the lagoon. According to the freshwater sediment quality standards, Cr levels of all sampling sites exceed the threshold effect level (TEL) and 17 % of them are even above the probable effect level (PEL). Most sampling sites of the channel discharging areas show minor enrichment of Cu, Ni, and Zn with respect to the TEL. Contamination indices show that the lagoon mouth area is enriched with As. Statistical analysis implies that discharges from agricultural channel and marine fluxes of the lagoon effects on the spatial distribution of measured elements. Further research is required to understand the rate of contamination in the studied marine system.

Assessment of dam removal from geochemical examination of Kuma River sediment, Kyushu, Japan.

The aim of this study was to determine if Arase dam gate removal and flushing elevated concentrations of any trace elements in Kuma River and Yatsushiro Bay sediments or caused riverine environmental change. The Arase dam gate on the Kuma River was opened in April 2010. Surface and bottom sediments were compared using 10-cm-long cores (2011) and two grain size fractions. Surface sediment data from 2002, 2012, and 2013 from the Kuma River and Yatsushiro Bay were also compared. The sediments were analyzed using XRF for 23 elements, and the grain size analysis was done. The short core surface and bottom sediments do not show major chemical changes, and therefore, may not represent post-and pre-dam sediments. Results based on 2011 samples show that the removal of the Arase dam gates in 2010 has been geoenvironmentally beneficial due to the decrease of environmentally related trace elements Pb and Zn in 2013. However, a slight increase in the levels of Cr, Cu, Zr, and Nb in 2013 indicates that periodic flushing in winter leads to elevation in these elements due to an increase in the fine fraction. Metal enrichment factors (EF) in 2002 are higher and these have decreased by 2013. Some elements exceed environmental guidelines, but this is due to natural background values, and there is no anthropogenic contamination. Thus, the environment of the river and bay has been significantly improved due to the dam opening. This result suggests that assessment and environmental monitoring studies are very important for dam management and future decision making.

Geochemical evaluation of present-day Tuul River sediments, Ulaanbaatar basin, Mongolia.

The Tuul River flows through the Ulaanbaatar basin of Mongolia and is the main source of water for the capital city, Ulaanbaatar. The Tuul catchment can be divided into three parts around Ulaanbaatar (upper, middle, and lower), according to the extent of urbanization. Sixteen surface water and groundwater samples were collected to evaluate present-day water quality and 34 stream sediment samples taken to examine their geochemical composition in relation to provenance and to assess the impact of urban activity on heavy metal accumulation. Groundwater quality in the upper and central water sources was adequate, but high concentrations of NO (3) (-) were found in the lower water source. Heavy metal concentrations in the sediments are evaluated by comparison with average upper continental crust (UCC) values, coupled with ecological risk assessment by reference to sediment quality guidelines (SQG). The results show average abundances of potentially toxic metals such as As, Pb, Zn, Cu, Ni, Cr, and V are higher in the middle part (within the city) than in the upper and lower parts. However, all three parts show depletion in some chalcophile and high field strength elements (Cu, Ni, Cr, Sr, Nb, Zr, Th, Sc) relative to UCC, indicating that the river sediments were derived from a highly felsic crustal source. The assessment using SQG shows As and Cr are present in levels that cause adverse aquatic biological effects. Although concentrations of Pb, Zn, Cu, and Ni are generally below their respective threshold effect levels, in the middle reaches, values increase and border on the probable effect level. This suggests significant anthropogenic contamination in the urban areas, increasing values above a naturally low regional background.

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.

Trace metal concentrations in tidal flat coastal sediments, Yamaguchi Prefecture, southwest Japan.

Geochemical investigations of tidal flat coastal sediments at Ogori, Ozuki, and Kasado in Yamaguchi Bay of southwest Japan were conducted to determine their metal concentrations and to assess contamination levels, compared with sediment quality guidelines (SQG) and several pollutant indicators. Selected major oxides, trace elements, and total sulfur (TS) were determined by X-ray fluorescence. pH values of most samples were alkaline, indicating anoxic conditions. Average abundances of As, Pb, Zn, Cu, Ni, and Cr in Ozuki sediments were 11, 27, 109, 21, 19, and 52 mg/kg, respectively, compared to 9, 29, 80, 16, 18, and 42 mg/kg at Ogori and 12, 27, 151, 34, 30 and 80 mg/kg at Kasado, respectively. Average concentrations of As, Zn, and Cu in all samples and TiO(2), Fe(2)O(3), and P(2)O(5) at Kasado were greater than those of the upper continental crust. Contamination levels were assessed based on SQG, contamination factors (CF), pollution load index (PLI), enrichment factor (EF), and index of geoaccumulation (Igeo). According to the SQG of the US EPA, the sediments were heavily polluted with respect to As, whereas Zn, Cu, Ni, and Cr were classed as moderately polluted. The elevated CF values of As, Pb, and Zn identify moderate to considerable contamination, indicating that these metals are potentially toxic in the study area. Based on PLI and EF, the study sites are moderate to moderately severe polluted with As and Pb, moderately polluted with Zn, and weakly contaminated to noncontaminated with Cu, Ni, and Cr. The highest Igeo values for As, Pb, and Zn in the surface and core sediments reflected the tendency of metal contamination that seems to be related to their fine-grained nature, organic matter-rich sediments, and anthropogenic point sources. Trace metal contents were strongly correlated with Fe(2)O(3) and TiO(2), suggesting that Fe oxyhydroxides and detrital clastic load play a role in controlling abundances 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.