報告書番号

T97043

タイトル（和文）

スギ林の土壌溶液におけるアルミニウムの存在形態

タイトル（英文）

SPECIATION OF SOIL SOLUTION ALUMINUM IN A JAPANESE CEDAR FOREST

概要 （図表や脚注は「報告書全文」に掲載しております）

群馬県の実験林において，スギの樹幹近傍１０ｃｍと樹幹から１ｍ以上離れたところの土壌溶液（深さ１０ｃｍ）を採取し，Ａｌの濃度と存在形態を調べた。樹幹近傍（Ｓ試料）と樹幹遠方（Ｔ試料）のｐＨは，それぞれ平均４．５２，平均５．８２であり，樹幹近傍では１．３程度のｐＨ低下がみられた。水中のＡｌを電荷が異なる３種類のＡｌ種（ＡｌＬＸ＜＝１＋，ＡｌＬＸ２＋，Ａｌ３＋）に分別する手法（ＨＰＬＣ法）を適用した結果，Ｔ試料の全Ａｌ濃度は平均１．０ミューｍであり，そのすべてがＡｌＬＸ＜＝１＋であった。一方，Ｓ試料の全Ａｌ濃度は平均４７ミューｍと顕著に高く，その７６％はＡｌ３＋であった。この結果から，土壌が著しく酸性化すると，全Ａｌ濃度が上昇するだけではなく，植物毒性が強いＡｌ３＋が卓越種となることが明らかとなった。

概要 （英文）

IT IS WELL KNOWN IN JAPAN THAT SOILS CLOSE TO THE STEMS OF JAPANESE CENDAR TREES (CRYPTOMERIA JAPONICA) ARE STRONGLY ACIDIC. THIS IS PARTLY DUE TO THE LEACHING OF HYDROGEN IONS FROM THE STEMS. SINCE SOIL ACIDIFICATION DUE TO ACIDIC DEPOSITION IS NOT OBSERVED IN JAPAN,INVESTIGATION OF SOILS AND SOIL SOLUTIONS CLOSE TO STEMS MAYBE WORTHWHILE TO PREDICT THE SITUATION THAT MAY OCCUR AFTER ACIDIFICATION DU TO ACIDIC DEPOSITION. IN A JAPANESE CEDAR FOREST IN GUNMA PREFECRURE,SOIL SOLUTIONS WERE COLLECTED TWICE A MONTH FROM MAY 1997 TO JANUARY 1998 USING CERAMIC POROUS CUPS AT A DEPTH OF 10 CM. SOIL SOLUTIONS FAR FROM STEMS (>= 100CM) WERE SLIGHTLY ACIDIC (PH-5.8) AND CONTAINED AVE. 1.0 MU M OF TOTAL AL. THE SPECIATION OF AL,USING CATION EXCHANGE CHROMATOGRAPHY WITH FLUORESCENCE DETECTION OF THE AL-LUMOGALLION COMPLEX,SHOWED THAT NEARLY 100 % OF THE AL CONSISTED OF SPECIES WITH A CHARGE LESS THAN OR EQUAL TO +1 (POSSIBLY,ORGANICALLY BOUND AL). THE MOLAR RATIOS OF BC (= CA2+ + MG2+ + K+) TO TOTAL AL RANGED FROM 66 TO 1050. IN CONTRAST,SOIL SOLUTIONS CLOSE TO A STEM (10 CM) WERE MARKEDLY ACIDIC (PH-4.5) AND CONTAINED AVE. 47 MU M OF TOTAL AL. FURTHERMORE,AVE. 76 % OF THE AL SPECIES WERE IN THE FORM OF AL3+. THE BC/AL RATIOS IN WINTER DECLINED TO AS LOW AS 2,WHICH WAS CLOSE TO THE THRESHOLD VALUE OF 1 THAT IS OFTEN USED IN CRITICAL LOAD ESTIMATES.

報告者

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