報告書番号

T97056

タイトル（和文）

スギ林への酸性物質の沈着量の評価－樹冠雨データにもとづく乾性沈着量の推定－

タイトル（英文）

EVALUATION OF ACIDIC DEPOSITION TO A JAPANESE CEDAR FOREST-ESTIMATION OF DRY DEPOSITION BASED ON THROUGHFALL MEASUREMENTS-

概要 （図表や脚注は「報告書全文」に掲載しております）

群馬県の実験林のスギ林において，樹冠雨の通年観測を実施し，その結果から酸性物質の乾性沈着量を評価した。スギ林内の３地点での観測から，ほとんどの成分について，地点間の林内沈着量に有意な差は認められなかった。樹冠雨データに，ＳＯ４２－を非溶脱成分とみなす物質収支モデルを適用し，乾性沈着量，溶脱量を分別評価した。その結果は，各成分の正味の林内沈着量の変動傾向や既往の文献値に一致し，おおむね妥当なものと判断された。スギ林へのＮＯ３－，ＳＯ４２－の年間の乾性沈着量の推定値は，それぞれ２２０ｅｑ／ｈａ／ｙｒ，１８１ｅｑ／ｈａ／ｙｒであり，これらの値はいずれも総沈着量（湿性＋乾性）の３０％を占めた。また，両成分の乾性沈着量の約９０％は暖候季にもたらされており，この要因として，暖候季に大気中のＨＮＯ３濃度が増加すること，ＳＯ２の沈着速度が増加することが推定された。

概要 （英文）

IN THIS STUDY,WE EVALUATED THE DRY DEPOSITION OF ACIDIFYING COMPONENTS TO A JAPANESE CEDAR (CRYPTOMERIA JAPONICA) FOREST LOCATED IN GUMMA PREFECTURE BASED ON THROUGHFALL MEASUREMENTS. INONE-YEAR MEASUREMENTS OF THROUGHFALL (TF) AND STEMFLOW (SF) CONDUCTED AT THREE DIFFERENT SITES WITHIN A FOREST,LARGE SPATIAL VARIATIONS IN TF+SF WERE NOT OBSERVED FOR MOST IONS. THE DRY DEPOSITION AND CANOPY LEACHING FOR THE MAJOR IONS WERE ESTIMATED USING A COMBINATION OF THROUGHFALL MEASUREMENTS AND A CANOPY BUDGET MODEL. IN THIS CANOPY BUDGET MODEL,IT WAS ASSUMED THAT CANOPY LEACHING OF SO42- WAS NEGLIGIBLE. THE RESULTS OF ESTIMATION WERE CONSIDERED TO BE REASONABLE,BECAUSE THE RATIO OF DRY DEPOSITION TO CANOPY LEACHING FOR MOST IONS AGREED FAIRLY WELL WITH THE RESULTS OF THE CORRELATION ANALYSIS FOR NET THROUGHFALL FLUXES AND THE ESTIMATED VALUES IN THE LITERATURE. THE ANNUAL DRY DEPOSITION FOR NO3- AND SO42- WAS ESTIMATED TO BE 220 EQ/HA/YR AND 181 EQ/HA/YR,RESPECTIVELY,WHICH AMOUNTING TO 30 % OF THE TOTAL (WET + DRY) DEPOSITION. THE ESTIMATED DRY DEPOSITION OF NO3- AND SO42- IN THE WARM SEASON WAS EQUALTO 90 % OF THE ANNUAL DRY DEPOSITION OF BOTH IONS. IT WAS CONSIDERED THAT THESE REMARKABLE SEASONAL VARIATIONS IN THE DRY DEPOSITION OF NO3- AND SO42- WERE DUE TO THE INCREASE OF HNO3 CONCENTRATION IN THE ATMOSPHERE AND THE INCREASE IN DEPOSITION VELOCITY OF SO2 TO A JAPANESE CEDAR FOREST.

報告者

キーワード