広谷 博史

酸性雨に対し中程度の耐性を示す褐色森林土壌地域で，河川水質に及ぼす酸性雨の影響を解明するために，石手川上流で調査を行った。1986-1987年と1997-1998年に採水したバルク降水の年間平均pHは約4.6であった。標高214mの主調査地点で1978-2003年に毎月測定した河川水のpHは，当初の約8.4から1991年の約7.5へと漸次低下したのち，約8.1へと再上昇した。この傾向は森林内の補助調査地点でも見られた。1985-2003年の3ヶ月ごとの詳細な河川水質調査で，SO4 2-濃度は当初から低下傾向を示した。強酸イオン濃度より過剰な塩基イオンとHCO3-とが弱アルカリ性をもたらした。因子分析の結果，pH変化がHCO3-濃度でなくCO2ガス分圧Pco2に依存することが分かった。HCO3-がH+の約10 5倍の濃度に保たれている中で，Pco2の増減が，H2CO3の解離を通してH+とHCO3-を同量変化させることで，pHにより強く影響したと見られる。酸性雨が降る前の記録と比べて，1980-1990年代の河川水では，塩基イオンとSO4 2-及びN03-の濃度が増大したが，HCO3-濃度はほとんど変化しなかった。酸性雨は土壌中の鉱物風化速度を速めたが，河川水のpHに大きな影響はなかったと見られる。

Microbial indicators such as heterotrophic bacteria, total conforms, and Escherichia coli in naturally developed riverbed biofilms were investigated. Pebbles covered with natural biofilm were sampled directly from the riverbed at sampling stations ranging from the upstream region within a quasi-national park to the midstream in the urban district. Heterotrophic bacteria densities in biofilm positively correlated with stream discharge. E. coli densities in biofilm positively correlated with temperature, which suggests the growth in the biofilm. It was considered that the attachment of planktonic bacteria to biofilm was negligible. The biofilm may serve as an internal source of false positive indication of fecal contamination in the water column. © IWA Publishing 2010.

Water quality parameters in the water column of a dam reservoir were measured monthly in 2001. From July to November, the vertical profiles of alkaline phosphatase activity (APA) and related parameters were examined in detail. APA increased during the summer in epilimnion while it was almost stable in hypolimnion. A small increase in APA was observed at a depth immediately above the bottom of the lake. APA fluctuation was independent of soluble reactive phosphorus. It was assumed that APA is not indicative of the phosphorus status of aquatic microorganisms in the lake. A positive correlation was observed between chlorophyll a content and APA in the photic zone. In the aphotic zone, APA correlated positively with the colony count of heterotrophic bacteria, but not with microscopic total bacterial count.

Fluctuations of alkaline phosphatase activities in two streams and in reservoirs receiving the stream waters located in two adjacent but not connected watersheds were investigated from January to December in 2000. Alkaline phosphatase activities (APA) remained nearly constant in both streams, whereas in reservoirs they increased during the summer season. No relation was found between APA and soluble reactive phosphorus concentration. At one sampling station located in the stream, phosphorus concentration extraordinarily increased later in the study, but there were no related change observed in APA. An examination of size-fractionated samples suggested that most the APA in stream could be attributed to dissolved enzymes, whereas in reservoir most APA was related to bacterial particles. It assumed that APA is not indicative of phosphorus status of aquatic microorganisms.

The occurrence of Aeromonas hydrophila in a mountain stream was studied quarterly for more than 3 years. A. hydrophila and fecal coliforms were measured by the membrane filter method, and heterotrophic plate counts (HPC) were measured by the pour plate method at 20 and 35 degrees C. A. hydrophila was detected from all samples collected and correlated with HPC, especially at 35 degrees C, but not with fecal coliforms. A. hydrophila densities along the main stream in a log scale correlated positively with the catchment areas in a log scale. The intercepts of the regression lines correlated positively with the mean water temperatures along the channel, which is considered to reflect the growth of the bacterium on the stream bed. The slopes correlated negatively with total precipitation in a 60-day period before each sampling. These results suggested that the Factors controlling A. hydrophila in a mountain stream were water temperature and precipitation, and that the bacterium was indigenous to stream environment rather than from contamination because of human activity.

Dryobalanops aromatica (Da)とD. lanceolata (Dl)はボルネオ熱帯雨林において突出木層を構成している主要なフタバガキ属の樹種である。その分布は近接しているが,決して重なり合うことはない。本論文では,これら2樹種の分布を,土壌形態学的,物理学的,化学的,微生物学的特性から吟味した。<BR> 地形的にみれば,Daは斜面上部のみに分布していたが,Dlは斜面の上部および下部に分布していた。この2樹種の優先する土壌の深さはいずれも1.3m以上であった。土性はDa土壌では砂質であったが,Dl土壌では砂質から粘質とその範囲が広かった。さらに,次のような差異が両土壌に認められた。1)リター層は伽土壌で厚かった。2)次表層の土色はDl土壌の方が鈍い色調を示していた。3)Dl土壌にはレキが認められたのに対して,翫土壌では認められなかった。4)交換性陽イオンのうち,CaおよびMg含量はD1土壌の方が高かった。5)交換性AlとH含量はDa土壌で高かった。6)気相,粗孔隙量と砂含量はDa土壌の方が高かった。このことは,降雨後Da土壌はより乾燥した土壌水分条件になることを示すが,それは土壌水分ポテンシャルのモニターによって証明された。7)カビはDa土壌の方がD1土壌よりも10倍多く認められた。<BR>以上の結果を総合するとDaは乾燥し易く,貧栄養で酸性の強い,安定した土壌生成過程を経た土壌に成立する。一方,D1はある期間還元を受けるような湿潤条件下で,かつDa土壌に比較して養分状態がよく,酸性が弱く,土壌生成過程の弱い土壌に成立することが明らかとなった。現地の焼畑農民はDlが成立する土地を耕地として利用するが,このDl土壌の特性を考慮すると,農民の伝統的な土地識別方法はきわめて適切であることが土壌学的観点から明らかとなった。

From a monthly survey over a ten-year period (1983-1992) of the Ishitegawa Reservoir, Japan, two multiple regression equations describing the mean chlorophyll a (Chl-a) concentration at 0.5 m depth during July, August and September (C-S) and the maximum Chl-a concentration in the photic zone, including its subsurface maximum during this period (C-M), were obtained. The conductivity at 0.5 m depth in May and the mean air temperature during May or during May and June were used as independent variables. These equations were calculated using seven years of data (1983-1988 and 1992). From 1989 to 1991 two impermeable plastic-coated sheet fences were installed across the upper end of the reservoir along the top 5 m of water column. The equations were used to determine the effectiveness of this flow regulation on the summer Chl-a concentration. In 1989 and 1991, when the fences were in place from June to August, no effects were found on the observed C-S and C-M values. In 1990, when the fences had been in place since October 1989, the observed values were lower than the predicted values.

Positive correlations in logarithmic scale were found between catchment areas and densities of bacteria in the upper reaches of the Ishite River in Ehime Prefecture, Japan. The constants, i.e. the intercepts and the slopes, given in the regression lines were analyzed to examine the factors affecting the bacterial counts. For this purpose we introduced the term "effective precipitation" which gives weight to the rainfall recorded near the day of sampling. It was suggested that total bacterial counts were affected by effective precipitation and water temperature. On the other hand, fecal coliform counts appeared to relate only to water temperature.

The antiviral extract from Rhodopseudomonas capsulata was purified and the predominant active component was defined as cis-vaccenic acid (Cl-8:1-DELTA-11) by gas-liquid chromatography and gas chromatography-mass spectrometry analyses. Antiviral activities of unsaturated fatty acids and related alcohols against T5 phage were also tested. Among them, linoelaidic acid, oleic acid, and petroselenyl alcohol inactivated 98%, 53%, 67% of T5 phage at the concentration of 50-mu-g/ml, respectively.

1)光合成細菌菌体中に存在する抗ウイルス活性物質の精製を行い,非活性が250倍にまで精製することに成功した。2)光合成細菌は,小児マヒウイルスを不活性化する抗ウイルス活性物質を産し,精製により活性は,著しく上昇した。3)銅イオンおよびアスコルビン酸を添加することにより,この物質のT5ファージに対する抗ウイルス活性は上昇した。鉄イオンは,この物質のT5ファージに対する抗ウイルス活性を阻害した。4)ニンジン,ピーマンは,抗ウイルス活性物質を含有し,光合成細菌のものと同様の操作で抽出,精製した。ただし,含有量は光合成細菌のものと比べると非常に低かった。

1)光合成細菌の一種Rhodopseudomonas capsulataは,シンドビスウイルスや大腸菌を宿主とするT5ファージを不活性化する物質を生産することが明らかとなった。2)その抗ウイルス活性物質は分子量10,000以下で蛋白質でもなく,核酸関連物質でもないと推察された。3)その抗ウイルス活性物質は暗黒条件では比較的熱安定性(60℃, 5分間ではほとんど不活性化しない)であった。しかし,光照射条件下では不活性化は進行した。ウイルスを不活性化する作用は光照射条件の方が暗黒条件より高かった。