All issues
Volume 66, Issue 1
Displaying 1-6 of 6 articles from this issue
- |<
- <
- 1
- >
- >|
-
Mitsuyo SAITO, Shin-ichi ONODERA, Tsutomu TAKEI2005 Volume 66 Issue 1 Pages 1-10
Published: April 20, 2005
Released on J-STAGE: December 11, 2009
JOURNAL FREE ACCESSIn order to demonstrate the nitrate transport process from land to the sea, variations in the NO3--N flux of river water were investigated, and the NO3--N flux of groundwater was estimated in a small coastal alluvial fan catchment covered by orange groves. The results are summarized as follows: 1) In the base-flow period, the NO3--N flux of river water decreased from the midstream to the downstream area with the deduction in runoff; 2) At the peak of a storm event with 11 mm of total rainfall, the NO3--N flux increased up to about 16 times that in the base-flow period. The total discharge of NO3--N during that event was estimated to be equal to that of 4 days during the base-flow period; 3) The NO3--N concentration in groundwater was more than 20 mg L-1 at the midstream area, whereas it had declined to less than 2.0 mg L-1 in the downstream area. Based on these results, we estimated the NO3--N discharge by groundwater to the sea to be about 2.4% of the annual nitrogen input from fertilizer application, suggesting that NO3--N was removed from groundwater by denitrification in the downstream area.View full abstractDownload PDF (816K) -
Shin-ichi ISHIWATA, Yasuhiro TAKEMON2005 Volume 66 Issue 1 Pages 11-35
Published: April 20, 2005
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSMany Japanese mayflies have been given two or more than two Japanese names by different taxonomists. In this paper, we conducted a historical review of the Japanese names of mayflies and discussed the necessity of determining a standard Japanese name for each taxon of the order. We then proposed the standard Japanese names for thirteen families, 39 genera, and 142 species of Japanese Ephemeroptera. Some corrections of their scientific names are also noted based on recent taxonomic studies.View full abstractDownload PDF (1921K) -
Takaki MINE, Shin-ichi ONODERA, Mitsuyo SAITO2005 Volume 66 Issue 1 Pages 37-41
Published: April 20, 2005
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSA river contains self-purification mechanisms such as denitrification and assimilation by plants. Although these mechanisms have extensively been studied, during a rainfall event when a river's flow differs from its normal condition, it is not clear what effect this has on its self-purification mechanisms. Therefore, to clarify the transformation and self-purification process of nitrogen, we focused on attention on variations in the discharge and nitrogen flux following three rainfall events in the Kurose River in Hiroshima Prefecture. Our observation site was put established 17 km from the riverhead. Water reaching the site flows through both urban and agricultural area. During three rainfall events, we sampled the river water at 2-hours intervals using an automatic water sampler and measured the water level in the river by means of level indicator. Water samples were analyzed for dissolved nitrogen (DN), NO3--N, NO2--N, and NH4+-N. The discharge was calculated from measured water level data and H-Q curve, and the flux from the product of concentration and discharge. Our results showed that DN flux varied inversely to variations in the discharge, and that its main factor was a decrease in the NO3--N flux. This indicates that the variations in upstream conditions involved changes in the discharge influenced the nitrogen discharge in the river.View full abstractDownload PDF (304K) -
Species redetermination of Trapezium liratum inhabiting Lake ObuchiKunio KONDO, Shinji UEDA, Keiko YAMAGUCHI, Machiko HATSUMI, Masatake K ...2005 Volume 66 Issue 1 Pages 43-50
Published: April 20, 2005
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSA comparison of the species thought to be Trapezium liratum inhabiting brackish Lake Obuchi in Aomori Prefecture with those inhabiting Lake Nakaumi shows some morphological differences, i.e., maximum shell size, shell width/shell length ratio, and surface pigmentation. We therefore conducted an isozyme polymorphism analysis to determine whether the species inhabiting Lake Obuchi is composed of the same species as those in Lake Nakaumi. Twelve different marker enzymes, AAT, ACP, CK, FDH, FUM, αGPD, IDH, LAP, MDH, ME, PGM and SOD, were detected, and fifteen loci were hypothesized from the populations in the two lakes. The allele frequency, average heterozygosity per locus (H), genetic identity (I), and genetic distance (D) were obtained. The level of genetic differentiation between the two populations revealed that each had a unique gene pool, but that this genetic differentiation was not at a level that would qualify them as different species. It was determined that the Trapezium liratum inhabiting both lakes are composed of the same species.View full abstractDownload PDF (1532K) -
Toshinobu MURAKAMI2005 Volume 66 Issue 1 Pages 51-57
Published: April 20, 2005
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSA terraced paddy field developing on a sloping area forms a special hydrologic cycle system due to its traditional plot-to-plot irrigation. In order to elucidate the flow and consumption of irrigation water, an investigation on water balance was conducted in the Obasute terraced paddy field of Chikuma City, Nagano Prefecture. The water level in the experimental paddies remained relatively high, since the water was supplied continuously from paddies father up the slope. Water balance analysis on rainless days made it clear that the amount of inflowing water was the most important factor controlling the other water balance items. The amount of percolation is relatively small in this area, as revealed by a result of gross analysis of water balance, because the upper plot losses water by percolation, while the lowest plot receives water through seepage from the bund of the upper ones. The alternation of percolation and seepage between the paddies creates a special water circulation system of the terraced paddy fields.View full abstractDownload PDF (1577K) -
2005 Volume 66 Issue 1 Pages 76
Published: 2005
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSDownload PDF (22K)
- |<
- <
- 1
- >
- >|