報告書番号

U98009

タイトル（和文）

森林渓流水水質の空間的分布と長期的変動の要因

タイトル（英文）

SPATIAL DISTRIBUTION AND LONG-TERM FLUCTUATION IN STREAMWATER CHEMISTRY OF FOREST WATERSHEDS

概要 （図表や脚注は「報告書全文」に掲載しております）

河川水質の形成機構を明らかにするため，■城県内３０箇所の森林流域における渓流水の水質の空間的分布特性と，時系列変動について調査を実施した。その結果，森林流域の水質形成に影響を与える要因として，流域内の地質や，海岸からの距離あるいは森林の林齢等の要因が関係しているという結果を得た。また渓流水の水質の時系列変動について調査し，長周期・短周期流出成分の異なる混合率の変化を仮定し予測した場合に，再現性が向上する結果を得た。

概要 （英文）

A STUDY OF THE DISTRIBUTION PROPERTY OF STREAMWATER CHEMISTRY WAS CONDUCTED FOR THREE YEARS IN ABOUT 30 FOREST WATERSHEDS IN IBARAKI PREFECTURE. A HIGHLY SIGNIFICANT NEGATIVE RELATIONSHIP WAS SHOWN BETWEEN INCREASING DISTANCE FROM COASTLINE AND CL,SO4 OR MGCONCENTRATIONS OF STREAMWATER. THESE COMPONENTS MUST BE STRONGLY RELATED TO MARINE-DERIVED SALT OR OTHER ARTIFICIAL SOURCES. CHLORIDE AND SULFUR CONCENTRATIONS INCREASED SIGNIFICANTLY WITH FOREST AGE, IMPLYING THAT ADDITIONAL DEPOSITION WAS SCAVENGED AT MATURING FOREST. NITRATE CONCENTRATION IN DEFORESTED WATERSHED WAS HIGHER THAN NEIGHBORING FOREST WATERSHED. HOWEVER IT SHOWED NO CORRELATION WITH FOREST AGE. THE PATTERN OF CHANGE IN STREAMWATER CHEMISTRY IS SIMULATED BY ASSUMING MIXING MECHANISM OF TWO SOURCE WATERS WITH SLOW AND RAPID RESPONSE CHARACTERISTICSOF FLOW. THE CHEMISTRY OF WATER WITH RAPID FLOW RESPONSE RESEMBLES THAT OF THE SOIL WATER OF THE SITE, THAT POSSIBLY MEANS THE WATER IS MAINLY COMPOSED OF SOIL OR VADOSE WATERS.

報告者

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