冬季の温暖化が渓流水の酸性化に及ぼす影響

We studied the annual variation of the pH of stream water in a snowy temperate area, where rain or temporary warming can cause frequent melting at the surface of snow cover, even in mid-winter with its intermittent snowfall. On the other hand, in the snowy cold area, the air temperature seldom rises above freezing point during winter. We reported the seasonal variation of the pH of stream water in a snowy temperate area. The pH value of stream water in a snowy temperate area was always changeably, decreasing in cold seasons and increasing in warm seasons. The drop in pH during the snowmelt season was remarkable. Although the pH drop of stream water was also temporarily observed in flooding during warm seasons, relatively long pH drops were observed in cold seasons. The air temperature and the snow depth in winter determine the pH of stream water in the snowmelt season. We examine the relationship between the pH of stream water in the snowmelt season and the air temperature and the snow depth in winter. The monthly mean temperature in February is very closely correlated with the monthly average pH of stream water in March. Furthermore, the maximum snow depth is also closely correlated with the monthly average pH of stream water in March.ArticleBulletin of Glaciological Research. 22:57-61 (2005)journal articl

温暖積雪地域における融雪水の化学特性

We studied the chemical properties of snow meltwater in a snowy temperate area, where air temperature above the freezing point and rainfall are observed even in mid-winter. The amount of bottom-melt beneath the snow cover in the snowy temperate area we studied was below 1mm day-1, which is similar to the amount in a snowy cold area. However, in the case of winter melting, the pH of the meltwater decreased and its electric conductivity increased correspondingly. As the snowmelt progressed, the oxygen-18(.DELTA.18O) of the snow cover increased gradually, and as a result, the .DELTA.18O of the meltwater also increased accordingly. We conducted a multiple regression analysis with four species of acidifying ions(NO-3 and nss-SO2-4) and neutralizing ions(NH+4 and nss-Ca2+) in meltwater as independent variables and H+ as a dependent variable. We could explain 86% of the H+ concentration fluctuation in meltwater based on the concentrations of these four ion species. A clear diurnal variation is observed in anion concentrations in meltwater at the peak melt season. The anion enrichment factors in meltwater are higher in the order of NO-3, nss-SO2-4 and Cl-, with values of 7.7, 7.2 and 4.0, respectively.ArticleBulletin of Glaciological Research. 20:15-20 (2003)journal articl

積雪融解に伴う花粉濃度ピークの変化

We have investigated the changes in Cryptomeria japonica pollen concentrations in a melting snow cover at different time points in order to understand the alterations in their concentration peaks. Recent studies have revealed that the pollen concentration peaks in mountain snow covers in temperate regions are useful for distinguishing between annual and several seasonal layers. Moreover, a dating method was applicable to a melting ice core. However, the manner in which pollen grains and their concentration peak values get influenced by melt water needs to be clarified. The present study intends to clarify this issue. Snow samples were collected from the Norikura Highland in central Japan during two snow-melting seasons: (1) from March to April in 2005 and (2) from March to May in 2006. The analysis of the C. japonica pollens was carried out because the pollen release reaches a high level from March to April in Japan when the winter seasonal snow still remains at the site; further, the pollen grains are commonly found within a typical size range. The results showed that the snow depth from the ground surface decreased because of snow melting during April and May, and the pollen concentration peak was consistently observed at the surface of the snow cover during the melting process. This indicated that the pollen concentration peak was not redistributed to the lower layers because of melting and the pollen grains present in the melted snow were concentrated at the surface. However, when the snow cover was about to disappear, the peak value decreased. This might account for the horizontal relocation of the pollen grains at the surface. Additionally, the peaks persisted at the surface even in the regions of the snow cover where water channels were formed. This indicated that the pollen peaks in the snow cover did not move toward the lower layers because of significant melting, although the peak values themselves may be changed due to the horizontal relocation of pollen grains.ArticleBulletin of Glaciological Research. 25:1-7 (2008)journal articl

中国・長白山における積雪の化学特性

ArticleBulletin of Glacier Research. 16:13-17 (1998)journal articl

乗鞍岳における融雪期の積雪中の化学物質の動態

A snow pit study was conducted on Mt. Norikura in the Northern Japan Alps from January to April to clarify the chemical dynamics in the snowpack during the snowmelt season. Little snowmelt occurred before February , the first snowmelt occurred between February and , and the peak of the snowmelt season occurred after March . Snow layers with remarkably high Cl , NO , and SO concentrations in the snowpack were traced; furthermore, the snow layers with high SO concentrations were found to disappear first. It was concluded that the ease with which the ions were flushed out from the snowpack was SO NO Cl.ArticleBulletin of Glaciological Research. 26:9-14 (2008)journal articl

北アルプスの山地流域における水収支と物質収支

We have investigated the water balance and mass balance for four years in Maekawa River basin on the eastern slope of Mt. Norikura-dake. In this region, the precipitation frequency is high from the rainy season to the autumn. The maximum base-flow discharge occurs in the spring snowmelt season. The pH and electric conductivity of the river water decline rapidly with the beginning of the snowmelt runo and temporarily decrease when the discharge increases temporarily in the rainy season or during a typhoon event. The Cl concentration of the river water increases in the early stage of snowmelt season since there is a considerable amount of sea salt in the snow. In addition, the NO concentration of the river water increases when the rainfall increases the discharge. The major ion concentration of the river water, except Cl and NO almost synchronizes with the change in the electric conductivity. In the mass balance of cations, the runo rate from the river basin considerably exceeds the atmospheric deposition rate to the river basin. This is because there is extremely much elution of ions from new volcanic rocks and soils. Further, the atmospheric deposition rate of NO is larger bigger with the biological consumption in the river basin than the runo rate from the basin.ArticleBulletin of Glaciological Research. 26:1-8 (2008)journal articl

中部山岳地域における降雪条件の違いによる積雪中の化学特性

We conducted a snow survey in February 2006 and January 2007 in Japan Alps. Approximately 0.60m and 1.05m snowfalls were deposited at the study site in February 2006 and January 2007, respectively. It was observed that the occurrence of snowfall was due to the low pressure formation in the vicinity of Japan and it also being the winter monsoon period. As a result of the analyzed snowpack, including new snow at a high resolution every 0.03m, a plurality of high-electric conductivity layers were observed at di erent depths. From the measurement of the major ion concentrations, it was observed that the high-electric conductivity layers had di erent chemical characteristics. High concentrations of NO3 and SO42 deposits were observed in the snowpack layer that was formed due to the low-pressure system that passed in the vicinity of Japan. On the other hand, the layer that formed during the winter monsoon pattern, large amounts of sea salts were deposited in the snowpack in January 2007. However, layers with a high sea-salt concentration were not observed in February 2006. We analyzed the movement of the air mass that flowed into the study area. Air mass passed through the city at the time of the passage of the low-pressure system. In addition, the air mass that crossed the Sea of Japan entered the study area during the winter monsoon pattern. However, the movement of the air mass was di erent during the winter monsoon pattern in February 2006 and January 2007.ArticleBulletin of Glaciological Research. 26:15-21 (2008)journal articl

融雪期における北方針葉樹林地の積雪中の化学物質の挙動

ArticleBulletin of Glacier Research. 11:33-38 (1993)journal articl

Is snowmelt runoff timing in the Japanese Alps region shifting toward earlier in the year?

Inter-annual variations of snowmelt runoff timing in 15 basins across central Japan were analyzed across 30 years, from 1980-2009, to determine if mountain hydrology has been affected by global warming. Observed daily river discharge was utilized to calculate center time (CT) of mass of flow. CT was found to be occurring significantly earlier in the year at two northern basins, with a rate of change of around five days per decade. While decreasing trends in CT in the other basins were not significant, negative correlations between CT and winter temperature was significant except for the central to northeastern basins. The effect of winter warming on snowmelt runoff was more significant in northern basins on the Sea of Japan side, where CT also correlated with the flowering date of cherry trees. Positive correlations between precipitation and discharge were stronger in southern basins, disturbing winter warming effect on spring discharge. These findings support the notion that winter warming accelerates snowmelt runoff, although year-to-year fluctuations were more pronounced than progressive warming over the three decades. Our results highlight inter-basin differences in hydrological response to climatic change, serving to validate down-scaling of climate simulations over the Japanese Alps region.ArticleHydrological Research Letters. 6:87-91 (2012)journal articl

北アルプスにおける冬季降水中の化学成分濃度

Spatial variability of the chemical constituents of winter precipitation on the eastern-western slopes of Mt. Norikura (alt. 3025m) of Japan Northern Alps was examined to clarify the transport process of aerosol that flows over the mountain barrier. The concentrations of chemical constituents in the snow recorded at the upper part of the mountain (above alt. 2420m) make a little difference. However, at the lower part of the mountain (below alt. 2420m), Cl- concentration in the snow on the eastern slope was lower than that on the western slope; non-sea-salt SO42- (nssSO42-), NO3-, nssCa2+, nssMg2+ and NH4+ concentrations on the eastern slope was higher than that on the western slope. The prevailing westerlies raged at the western and alpine parts of the mountain. On the eastern part of the mountain, the easterlies were predominant. We infer that the snow below an altitude of 2420m, in comparison to the other parts of mountain, is under relatively greater influence of the local emission of the chemical constituents.ArticleBulletin of Glaciological Research. 28:17-26 (2010)journal articl