17:15 〜 18:45
[AHW18-P03] Role of the alpine soil for the stream water quality formation in alpine regions
キーワード：高山帯、土壌、溶出試験、水保持、水質
The alpine region is an important water source area downstream. Previous research has revealed that water quality would not be largely affected by soil and geology in alpine regions due to rapid runoff response to rainfall; however, recent research mentioned that water retention potential is not negligible in areas with well-developed alpine soils. This indicates that the role of alpine soils in forming stream water quality remains unexplored. Therefore, the objective of this study is to determine the water retention functions of alpine soils associated with forming the stream water quality.
The field surveys were conducted at 17 sites in the alpine zone of Norikura-dake in the Northern Japanese Alps. Soil cores were collected at each depth with recording soil features. Soil water, stream water, and spring water were collected and analyzed for water quality and isotope ratios. The collected soil was then used for the leaching experiment. The dissolved ions in the eluted water were analyzed after the experiment.
A maximum soil layer of 1.11 m was observed in the field. While isotopic ratios of soil water were higher in shallower depth layers, they were plotted in the same position as precipitation on the delta diagram. Thus, the high precipitation and low temperatures characteristic of alpine areas may have shortened the evaporation time of soil water. The total dissolved ion concentrations in the water samples were higher in the order of soil water > spring water > precipitation, and calcium and bicarbonate ion concentrations were higher in the soil water. Soil water retains subsurface long enough to acquire much-dissolved ions. In other words, the soil would have a water storage function to retain water longer time. The nitrate concentrations in the collected soil water were low, whereas higher concentrations were detected in the filtrate from the leaching experiments. This suggests that the use of nitrate by organisms in the field is active and that there may not be a large enough surplus to dissolve in the water.
The field surveys were conducted at 17 sites in the alpine zone of Norikura-dake in the Northern Japanese Alps. Soil cores were collected at each depth with recording soil features. Soil water, stream water, and spring water were collected and analyzed for water quality and isotope ratios. The collected soil was then used for the leaching experiment. The dissolved ions in the eluted water were analyzed after the experiment.
A maximum soil layer of 1.11 m was observed in the field. While isotopic ratios of soil water were higher in shallower depth layers, they were plotted in the same position as precipitation on the delta diagram. Thus, the high precipitation and low temperatures characteristic of alpine areas may have shortened the evaporation time of soil water. The total dissolved ion concentrations in the water samples were higher in the order of soil water > spring water > precipitation, and calcium and bicarbonate ion concentrations were higher in the soil water. Soil water retains subsurface long enough to acquire much-dissolved ions. In other words, the soil would have a water storage function to retain water longer time. The nitrate concentrations in the collected soil water were low, whereas higher concentrations were detected in the filtrate from the leaching experiments. This suggests that the use of nitrate by organisms in the field is active and that there may not be a large enough surplus to dissolve in the water.