報告書番号

T90001

タイトル（和文）

酸性降下物に対する土壌緩衝能の鉛直分布

タイトル（英文）

VERTICAL DISTRIBUTION OF ACID-NEUTRALIZING CAPACITY OF SOILS

概要 （図表や脚注は「報告書全文」に掲載しております）

前報で提案した土壌の酸緩衝能の簡易測定法を用いて，緩衝能が大きく異なる代表３地点（土壌型：褐色森林土，残積性未熟土，黒ボク土）において地表から深さ１ｍまでの緩衝能の鉛直分布を調べた。その結果，酸緩衝能の鉛直分布は深さ方向に一定ではなく，土壌の非晶質鉱物含量の大小によって２種類の鉛直パターンを示すことが判った。１）褐色森林土をはじめとする非晶質鉱物に乏しい多くの土壌では，緩衝能は有機物（腐植）に富む地表付近が最も高く，地表から深さ１０ｃｍ程度の間で急激に減少し，それ以深ではほぼ一定の低い値となる。２）アロフェン質の黒ボク土に代表される非晶質鉱物に富む土壌では，表層約１０ｃｍでの分布は上記土壌に類似し，それ以深では非晶質鉱物量の増加に応じて緩衝能が増大する。

概要 （英文）

BY USING A SIMPLE PROCEDURE FOR MEASURING THE ACID-NEUTRALIZING CAPACITY (ANC) OF SOILS PROPOSED IN PREVIOUS PAPERS,THE VERTICAL ANC DISTRIBUTION OF SOILS WAS INVESTIGATED UP TO 1 M IN DEPTH AT THREE SITES. THE SOIL TYPES WERE CAMBISOL,REGOSOL AND ANDOSOL. FOR THE CAMBISOL SITE,THE ANC SHOWED A MAXIMUM VALUE OF 19.6 MEQ/100 G IN THE UPPERMOST 0 3 CM LAYER; IT DECREASED ABRUPTLY TO APPROXIMATELY 5MEQ/100 G WITHIN 10 CM DEPTH,AND SHOWED ALMOST CONSTANT VALUES (2 5 MEQ/100 G) IN THE DEEPER LAYERS. FOR THE REGOSOL SITE,THE VERTICAL ANC PATTERN WAS SIMILAR TO THAT OBSERVED AT THE CAMBISOL SITE. THIS PATTERN GAVE GOOD AGREEMENT WITH THE ORGANIC (HUMIC AND FULVIC) ACID CONTENT OF THE SOILS AT EACH SITE,INDICATING THAT THE ANC IN THE SURFACE LAYERS ARISES MAINLY FROM EXCHANGEABLE BASES IN THE HUMUS. AT THE ANDOSOL SITE,THE ANC DECREASED FROM THE GROUND SURFACE TO 10 CM IN DEPTH,AND THEN INCREASED GRADUALLY WITH DEPTH. THIS VERTICAL PATTERN GAVE GOOD AGREEMENT WITH THE ORGANIC-ACID CONTENT OF THE SOILS UP TO 10 CM IN DEPTH AND,IN THE DEEPER LAYERS,WITH THE AMOUNT OF SI EXTRACTED FROM AMORPHOUS MINERALS IN THE SOILS. THIS INDICATES THAT EXCHANGEABLE BASES IN THE HUMUS INTHE SURFACE LAYERS ARE THE MAIN CONTRIBUTOR TO THE ANC. WHEREAS IN THEDEEPER LAYERS,SO42- ADSORPTION BY AMORPHOUS MINERALS INCLUDING ALLOPHANE DOMINATES THE ANC.

報告者

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