土壌の物理性

大気境界層における炭酸ガス輸送の測定

大滝英治

1992 年 65 巻 p. 3-9
発行日: 1992年
公開日: 2021/12/30

DOIhttps://doi.org/10.34467/jssoilphysics.65.0_3

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The fast response instrument designed to measure simultaneous fluctuations of carbon dioxide and water vapor is described. The measuring frequency was 30 Hz. The sensing path length of the instrument was 20 cm. This is compatible with the path length of the standard type of a sonic anemometer. The noise level was about 0.8ppm for carbon dioxide measurement and about 0.02g/kg for water vapor measurement. The cospectrum estimate of carbon dioxide and vertical wind velocity showed that the high frequency loss due to smoothing effect of sensing path length was about 2 % for wfc r measurement. This denotes that the present instrument is promising for flux measurements of carbon dioxide by the eddy correlation technique in conjunction with a sonic anemomet er. The carbon dioxide flux measured by the eddy correlation technique showed a well defined diurnal variation over a paddy field characterized by the negative values in the daylight hours and positive values in the nighttime. Examination of the stability dependency of eddy diffusivities for carbon dioxide (Xc), sensible heat (Kh), and momentum (Km) showed that the ratio Kh/Kc is unity, but the ratio Kc/Km increases with increasing instability of the air layer as a function of (1—16z/L)1/4.

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水田土壌中におけるC02とCH4の動態一大気へのフラックスー

木村眞人, 村瀬潤

1992 年 65 巻 p. 11-20
発行日: 1992年
公開日: 2021/12/30

DOIhttps://doi.org/10.34467/jssoilphysics.65.0_11

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The earth warming is now one of the most serious environmental problems. Of all the greenhouse gases, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) are deeply related to agriculture. Methane is emitted from paddy fields, and nitrous oxide from upland fields according to fertilizer application, respectively. As is well known, paddy fields are one of the most important sources of methane fluxes. Hitherto, studies on methane fluxes from paddy fields have mainly focused on their quantitative estimation, while production and movement of methane in paddy soils have not been major concern among researchers. Paddy soils are microbially dynamic environment, in which carbon dioxide and methane are produced and emitted through various processes. In this paper, the processes involved in the production and movement of carbon dioxide and methane in paddy soils were reviewed with special consideration to chemical properties of these two gases and the role of percolation water on their fates in paddy soils.

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土壌•堆積物の一酸化二窒素還元活性

吉田尚弘, 山崎岳

1992 年 65 巻 p. 21-28
発行日: 1992年
公開日: 2022/01/04

DOIhttps://doi.org/10.34467/jssoilphysics.65.0_21

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岩手県大槌川水系に沿って,森林土壌から湾内堆積物にいたる土壌•堆積物試料を採取し,1SNで標識をつけた一酸化二窒素(N2O)を用いて,地球温暖化とオゾン層の消長に重要な役割を果たすN2Oの還元活性を測定した。いずれの土壌•堆積物も髙い還元活性を示し,もっとも高い活性を示したのは嫌気的な部位の卓越する河口の堆積物であった。湾内の堆積物コア試料についてN2O還元活性の鉛直分布を調べたところ,亜表層の堆積物が,堆積物中の間隙水のN2O濃度の上昇を抑制していることが明らかにされた。N2Oの還元活性と硝酸の還元活性の間には非常によい相関があり,これを利用することですでに数多く研究されている硝酸還元活性の見積もりから地球規模の還元によるN2O消滅星を推定することが可能になると思われる。一方,N2OとN2Oに関わる化合物について窒素と酸素の安定同位体比を指標とする研究はN2〇の地球化学的循環を理解するための有効なアプローチである。安定同位体による研究とフラックスの測定により得られた知見の重ね合わせを通して,N2Oの地球化学的循環の全体像が明らかにされると考えられる。

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農業生態系から放出される含硫ガス

陽捷行

1992 年 65 巻 p. 29-33
発行日: 1992年
公開日: 2022/01/04

DOIhttps://doi.org/10.34467/jssoilphysics.65.0_29

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Interest in the atmospheric sulfur (S) budget has developed rapidly because anthropogenic activities are increasing the rates of emission of S gases into the atmosphere. These increase are important because S gases are oxidized in the atmosphere with formation of sulfate, the resulting contributes to environment problems associated with acid rain. There also is evidence that S gases may alter the optical properties of clouds and which could affect global climate. Large uncertainties remain concerning the chemical speciation and the magnitude of natural emission of S gases to the atmosphere. It has been well documented that dimethylsulfide (DMS) is most important in ocean, which have been estimated to contribute 40 Tg or 15 TgS to the atmosphere as S gases each year. The annual amounts of S evolved from soil have been estimated to be 7 to 77 TgS. Very little is known concerning emissions from paddy field, which are abundant in many parts of the world. The purpose of this report is to summarize the results of recent measurements of emissions of biogenic S gases from rice paddies in Japan. Emissions were measured in laboratory studies to learn more about the kinds and sources of S gases produced. Emissions were measured in paddy lysimeters and in paddy fields to gain better information about the amounts of DMS, carbonyl sulfide (COS), and carbon disulfide (CS2) emitted, the seasonal and diurnal patterns of emission, and the factors affecting emissions of these gases under field conditions.

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生態系における腐植生成と脂肪族成分の変動

米林甲陽

1992 年 65 巻 p. 35-41
発行日: 1992年
公開日: 2022/01/04

DOIhttps://doi.org/10.34467/jssoilphysics.65.0_35

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To estimate the average chemical structure of humic acids, structural parameters were calculated from the elemental and functional groups analysis and hydrogen distribution estimated by H-NMR ; carbon aromaticity fa, hydrogen to carbon ratio in hypothetical unsubstituted aromatic material Hau/Cau, and number of aliphatic substituent nai. From the Hau/Cau value, condensation degree of aromatic ring was estimated. Number average molecular weight of humic acids were measured by the vapor pressure osmometry. Consequently, Andisol humic acids consist of a few structural subunits assumed to be condensed aromatic rings with short aliphatic substituents and many carboxyl and carbonyl groups. Aquent and Ochrept humic acids consist of many structural subunits assumed to be aromatic ring with relatively long aliphatic substituents. Macroporous, nonionic Amberlite XAD-8 resin was used for fractionation of soil humic acids in order to reduce their complexity. H+-saturated humic acid was adsorbed onto the resin at pH 3 and fractionated into four components by stepwise elution using universal buffers adjusted to pH 7, to pH 11,water, and 50% ethanol. The first components consists of a few structural subunits, assumed to be condensed aromatic rings with short aliphatic substituents and many carboxyl groups. The second component was characterized by phenolic groups, and the third by relatively long aliphatic chains. The fourth component consists of many structural subunits, assumed to be aromatic rings with long aliphatic substituents. These components were termed as carboxylic, phenolic, semi-aliphatic, and aliphatic components, respectively. Andisol humic acids contained abundant amounts of carboxylic component. Aquatic sediment humic acids contained ample amount of aliphatic components. Phenolic component was dominant in humic acids of tropical peats sublayer soils. Component analysis could lead to a new way to estimate the humification processes of humic substances.

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「土壌中の非保存性物質の動態」に関する土壌物理学ならびに農業土木学の観点からのコメント

三野徹

1992 年 65 巻 p. 45-46
発行日: 1992年
公開日: 2022/01/04

DOIhttps://doi.org/10.34467/jssoilphysics.65.0_45

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総合討論

1992 年 65 巻 p. 47-54
発行日: 1992年
公開日: 2022/01/04

DOIhttps://doi.org/10.34467/jssoilphysics.65.0_47

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TDRによる土壌の体積含水率および電気伝導度の測定について

堀野治彦, 丸山利輔

1992 年 65 巻 p. 55-61
発行日: 1992年
公開日: 2022/01/04

DOIhttps://doi.org/10.34467/jssoilphysics.65.0_55

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