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Toshiaki M.,The Toyama Prefecture Environmental Science Center | Toshiaki M.,University of Toyama | Zhang J.,University of Toyama | Hiroshi S.,University of Toyama | And 3 more authors.
Atmospheric Research | Year: 2012

We measured the lead (Pb) and sulfur (S) isotopic ratios in precipitation collected in Toyama Prefecture, Japan, to investigate their characteristics as tracers for trans-boundary air pollution. The Pb concentrations and isotopic ratios were measured by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). A relatively higher 207Pb/ 206Pb isotopic ratio (area 3: Northern China, 0.869±0.003; area 4: Central China and Korea, 0.870±0.006) was assumed to be related to Northern Asian sources, whereas the samples influenced by Japanese air mass showed a lower 207Pb/ 206Pb ratio (area 5: Japan, 0.863±0.004). Sulfur ion was measured by Ion Chromatography (IC), and S isotopic ratios were measured by Mass Spectrometry. The S isotopic ratios' weighted average values (area 3: 4.9±1.4%; area 4: 6.3±1.5%) of the Asian continent showed a higher isotopic ratio than that of Japan (area 5: 3.6±1.8%). It was difficult to use the NO 3 -/non-sea-salt SO 4 2- (nss SO 4 2-) (N/S) ratio's weighted average values to distinguish the Japanese origin (area 5: 0.71) from the continental origin (area 3: 0.68, area 4: 0.66). We attempted to use the S isotopic ratio in addition to the lead isotopic ratio to characterize the transported East Asian air pollution, and as a result we found that the combination of these isotopic ratios was useful for identifying the origin of air pollution in the East Asian region. © 2011. Source

Sakamoto S.X.,University of Tokyo | Sasa S.,University of Tokyo | Sawayama S.,University of Tokyo | Tsujimoto R.,Northwest Pacific Region Environmental Cooperation Center | And 4 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

Seaweed beds are very important for abalones and sea urchins as a habitat. In Sanriku Coast, these animals are target species of coastal fisheries. The huge tsunami hit Sanriku Coast facing Pacific Ocean on 11 March 2011. It is needed for fishermen to know present situation of seaweed beds and understand damages of the huge tsunami on natural environments to recover coastal fisheries. We selected Shizugawa Bay as a study site because abalone catch of Shizugawa Bay occupied the first position in Sanriku Coast. To evaluate impact of tsunami on seaweed beds, we compared high spatial resolution satellite image of Shizugawa Bay before the tsunami with that after the tsunami by remote sensing with ground surveys to know impact of the tsunami on seaweed beds. We used two multi-band imageries of commercial high-resolution satellite, Geoeye-1, which were taken on 4 November 2009 before the tsunami and on 22 February 2012 after the tsunami. Although divers observed the tsunami damaged a very small part of Eisenia bicyclis distributions on rock substrates at the bay head, it was not observed clearly by satellite image analysis. On the other hand, we found increase in seaweed beds after the tsunami from the image analysis. The tsunami broke concrete breakwaters, entrained a large amount of rocks and pebble from land to the sea, and disseminated them in the bay. Thus, hard substrates suitable for attachment of seaweeds were increased. Ground surveys revealed that seaweeds consisting of E. bicyclis, Sargassum and Laminaria species grew on these hard substrates on the sandy bottom. © 2012 SPIE. Source

Terauchi G.,Northwest Pacific Region Environmental Cooperation Center | Terauchi G.,Nagasaki University | Tsujimoto R.,Northwest Pacific Region Environmental Cooperation Center | Ishizaka J.,Nagoya University | Nakata H.,Nagasaki University
Mer | Year: 2014

It is often reported that increase of phytoplankton biomass in Toyama Bay coastal area in summer is a cause of water quality degradation as measured by Chemical Oxygen Demand. Satellite chlorophyll-a concentration (Chl-a) and river discharge from 1998 to 2009 were compared to study the influence of land-based sources of nutrients on seasonal and interannual variability of Chl-a in Toyama Bay. Toyama Bay was divided into three sub-areas (A, B and C, from innermost to outermost) by taking level, trend and peak timing of satellite Chl-a into consideration. In sub-area A, satellite Chl-a increased towards summer and its increasing interannual trend was detected. From the comparison of variability in satellite Chl-a with river discharge and nutrient data in Toyama Bay, it was suggested that a high concentration of total nitrogen from the Jinzu River was a compelling cause of potential eutrophication in subarea A. In both suh-areas B and C, a positive correlation was found between satellite Chl-a and river discharge from May to July (p < 0.01, r 0.47 in sub-area B; p < 0.01, r = 0.47 in subarea C) and August to October (p < 0.01, r = 0.51 in sub-area B; p < 0.01, r - 0.47 in sub-area C). It was considered that there were excessive nutrients not used by phytoplankton in subarea A, and they were delivered to sub-areas B and C from May to October then contributed to increase in phytoplankton biomass. The influence of river discharge on satellite Chl-a was obvious in the sub-area A throughout the year, but it also occasionally extends to sub-areas B and C from May to October. Monitoring the peak pattern and level of seasonal variability in Chl-a was suggested for assessment and management of water quality, because a single and long summer peak pattern is correlated with symptoms of eutrophication. Source

Terauchi G.,Northwest Pacific Region Environmental Cooperation Center | Terauchi G.,Nagasaki University | Tsujimoto R.,Northwest Pacific Region Environmental Cooperation Center | Ishizaka J.,Nagoya University | Nakata H.,Nagasaki University
Journal of Oceanography | Year: 2014

Time series of the chlorophyll-a concentration (Chl-a) observed by ocean color satellites from 1998 to 2009 were used to assess eutrophication in Toyama Bay, the Sea of Japan. An overall mean of Chl-a during the 12-year period was used to divide the study area into "high" or "low" Chl-a areas based on a reference condition of 5 mg m-3. The annual maximum monthly mean Chl-a trend was estimated pixel-wise and its significance examined by the Sen slope test at a 90 % confidence level. By combining the level and trend of remotely sensed Chl-a, Toyama Bay was then classified into six eutrophication states: high-increasing, high-no trend, high-decreasing, low-increasing, low-no trend and low-increasing. Our study indicates that the combined use of both the level and trend of remotely sensed Chl-a can be an efficient method to preliminarily assess eutrophication of coastal waters after a quality screening process with level 2 flags and validation with in situ Chl-a data. © 2014 The Oceanographic Society of Japan and Springer Japan. Source

Maeda T.,Fisheries Research Institute | Maeda T.,Northwest Pacific Region Environmental Cooperation Center | Uchiyama I.,Fisheries Research Institute
Nippon Suisan Gakkaishi (Japanese Edition) | Year: 2013

To clarify the growth of female beni-zuwai crab Chionoecetes japonicus, they were collected from the central part of Toyama Bay at the depth of 1060-1270 m by beam trawls from 2006 to 2011. Carapace width (CW) measurements revealed 9 and 2 modes in the size frequency distribution in juvenile and immature, and adult female, crabs respectively. Dividing into each normal distribution by the Hasselblad method, the mean size in CW was estimated to be 6.3, 9.0, 12.8, 18.0, 24.4, 33.2, 43.2, 56.1 and 66.1 mm in juvenile and immature crabs, and 68.5 and 81.5 mm in adult crabs, which were thought to mean CW at the 3rd to 11th instars and 11th to 12th instars, respectively. The size frequency distribution showed that most females would experience terminal molt at the 10th instar and grow into adult females at the 11th instar. Source

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