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原位置不溶化処理を行った水銀およびふっ素で汚染された地盤を対象として長期安定性を評価した。そこで，(1)汚染物質の溶出抑制効果の定量評価，(2)再溶出した汚染物質の挙動把握が必要と考えた。ここでは，前者について実際に原位置不溶化処理した地盤で採取した土を用い，室内試験により不溶化処理土の再溶出の可能性を確認した。後者は数値解析に基づき再溶出した物質の地盤内の挙動を検討した。その結果，水銀は130年経過した場合に基準不適合となり，ふっ素は1,800年以上基準適合となることから不溶化処理によって長期的に安定することが推察された。再溶出した汚染物質は，不溶化処理に伴う化学形態の変化と地盤の透水性低下に伴い，水銀の場合に100年経過しても0.02m程度の移動となった。以上のことより，原位置不溶化処理による長期的な拡大防止効果に関して定量的な評価が可能になった。

We conducted a numerical simulation of disaster waste disposal by using a Dynamic Hauling/Transportation model (DHT model) in order to extract the factors to hinder the execution of a disposal management plan of Wakayama city government. The DHT model was developed for estimating number of days required for disaster waste disposal, following parameters are mandisopdatory as the model inputs; (1) disaster waste characteristics (distributions, volume and contents) in damaged area, (2) hauling/transportation route, (3) number/capacities of transportation vehicles, (4) maximum capacities at temporary storage / final disposal sites and (5) abilities of crushing/classification equipment. Almost all parameters were set by referring to a planning document of disaster waste disposal provided by Wakayama city and disposal guidelines published by Ministry of the Environment of Japan. Several parameters without description in these document/guideline, e.g. maximum capacities at temporary storage and distance of hauling/transportation route were estimated by using GIS. Severe shock and tsunami caused by Nankai Trough huge earthquake were adopted as external forces generating disaster waste. By assumption that parameters included in (3) and (5) could be critical parameters for a result of simulation, we performed sensitivity analysis of each parameter in them. As a result, abilities of several crushing / classification at temporary storages were the most sensitive parameters of all evaluated parameters. Therefore, augments of crushing/classification functions at temporary storage might be effective to shorten processing days for disaster waste disposal

エサキアメンボでは, 越冬世代の成虫はその他世代の成虫よりも飛翔性が強く, 繁殖場所となる溜池と越冬場所となる溜池との間を秋季と春季に飛翔移動すると推定されている。その真偽を検討するために, 和歌山県紀の川市で2ヶ年にわたって, 冬季の成虫, ならびに初夏の幼虫と成虫の存否を96の溜池で調査した。さらに, 冬季の存否と夏季の水面上の "植生面積" との組み合わせ, ならびに夏季の存否と冬季の "陸域面積" との組み合わせに基づいたパッチ占有モデルによって分布予測をおこなった。野外では, 冬季も夏季も生息を確認できた溜池が存在した一方で, 夏季あるいは冬季のみに生息を確認できた溜池もあった。モデル解析結果は実際の分布変動に近似した。これらの結果は本種が春季と秋季に飛翔移動することを強く示唆しており, 繁殖場所と越冬場所をともに備えた溜池が, 短命な局所個体群の創設雌の供給源であることを示した。こうした点に注目し, 京都府精華町で新たに発見した生息場所の状況を記録した。

土壌汚染対策法の施行規則では，原位置封じ込めが地下水汚染を経由した健康被害を防止するための標準的措置になっている。しかし，同法の主な対象と考えられる市街地では，原位置封じ込めの適用条件を満足する不透水層があまり存在しないことが明らかになってきた。そこで本研究では，より多くの現場に適用可能な原位置封じ込め措置として地下水揚水併用型を考え，数値解析を実施して汚染拡散防止効果を考察した。その結果，薄い難透水層しか存在しない現場においても，地下水揚水の併用によって，原位置封じ込め措置を適用できることが確認された。また，汚染拡散防止に必要な難透水層内の上向きの地下水浸透量は，封じ込め区域900m2あたり0.1m3/d程度でよいことも推察された。これは，遮水壁の性能が十分であれば，地下水揚水量が難透水層内の浸透量と同程度の少量で済むことを示唆している。

本稿では，3次元数値解析を実施して，茨城県神栖市で起きた有機ヒ素化合物(ジフェニルアルシン酸，DPAA)による地下水汚染機構を明らかにした。汚染が発見された飲用井戸(A井戸)周辺を対象とした数値解析では，A井戸南東90m地点の表層地盤中で発見されたコンクリート様の塊から溶出したDPAAを高濃度に含む汚染水が，密度流によって地下深くまで降下浸透し，深度30m付近の洪積砂礫層に達した後，流速の大きな地下水流れに乗って，A井戸およびその下流域にまで拡がっていく様子が示された。これにより，A井戸の汚染の原因はコンクリート様の塊から溶出したDPAAであることが推察された。また，汚染地域全体を対象とした数値解析では，汚染発見によって複数の企業局揚水井戸の運転が停止されるまでの間，これらの井戸からの揚水の影響でDPAAの下流への拡散が抑制されていた可能性が高いことも示唆された。

本稿では，2003年3月に茨城県神栖市で発生した有機ヒ素化合物による地下水汚染の実態について報告する。汚染物質となった有機ヒ素化合物はジフェニルアルシン酸である。汚染地域で実施した野外調査では，ジフェニルアルシン酸は主に帯水層深部から検出された。しかし，汚染の発端となった飲用井戸の南東90m付近の人工的に埋め戻された浅層地盤からは，ジフェニルアルシン酸を高濃度に含むコンクリート様の塊が発見され，これが汚染源と推察された。また，地下水の汚染は汚染源から約3km離れた下流地区まで拡がっていることが確認された。

We showed that the amount of irrigation water was 34.4 m3/s during irrigation period in the kinokawa river, Japan. This is very large compared to the river discharge in a normal flow condition. To take water use into account a runoff analysis using a distributed hydrological model, we proposed a new model that consider the water-intake from head works, inflow, storage and flood control by dams. It was found that the simulated river discharge using this model agreed with the observation data, especially for the low water flow in the irrigation period. In addition, the reduction rate of irrigation water from paddy fields to kinokawa river was inversely estimated. The rate was low in a small precipitation year and was high in a high precipitation year. This characteristic agrees with a traditional and empirical water uses of irrigation water.

本研究では, 廃棄物処分場等の鉛直遮水工として適用されることが多いソイルセメント系連続地中壁の物理・力学特性に関する種々の室内試験を実施するとともに, 地震応答解析によりソイルセメント系連続地中壁の耐震性能評価を行った。その結果, 1) ソイルセメント連続地中壁は, 兵庫県南部地震クラスの巨大地震 (レベル2地震動) に遭遇すると, 引張強度不足に起因してクラック等が発生し遮水機能が大幅に低下する可能性があること, 2) ベントナイトの混合比率を大幅に増加させることによって, 固化後でも塑性状態を維持し得るソイルセメント・ベントナイト連続地中壁の造成が可能となること, 3) ソイルセメント系連続地中壁の耐震性能評価を行う場合, ソイルセメント連続地中壁では引張応力に対する安全率に, またソイルセメント・ベントナイト連続地中壁ではせん断応力に対する安全率に着目すればよいことを明らかにした。

In order to evaluate the natural attenuationof chlorinatedethenes, especially trichloroethylene (TCE) anddichloroethylenes (DCEs) in an aquifer, the effects ofdispersion-and-dilution and biodegradation on the concentrations of TCE and DCEs were investigated using numerical simulation. The resultsobtained in this study can be summarized as follows: (1) In an aquifer with high biodegradation rate of DCEs (first order rateconstantof DCEs is over 2.0×10-3/d), the concentrationratioof DCEs to TCE is less than 1.0. (2) In an aquifer with highdispersion-and-dilution rate (groundwater velocity is over 0.6m/d-1.0m/d), the concentration ratio of DCEs to TCE is less than 1.0. (3) When the first order rate constantof DCEs is less than 1.0×10-3/d and the groundwater velocity is less than 0.4m/d-0.7m/d, DCEs tend to accumulate in an aquifer.

ネットワークの高速化やパーソナルコンピュータ(PC)の高性能化により，PC間をネットワーク結合したPCクラスタを利用した並列計算機がスーパーコンピュータ並みの高速計算処理能力を有するまでになってきた．本稿では，地下水中の物質輸送解析法の一つである特性曲線法を分散メモリ型のMPI(Message Passing Interface)を用いて並列化し，PCクラスタ上で実行させて並列化手法の有効性を検討した．その結果，PC8台を利用した場合の演算速度の向上は最大6倍となり，並列実行の効果が大きいことがわかった．

有害な揮発性物質による土壌・地下水汚染では，吸引法，エアースパージング工法やバイオベンティング工法などの対策工が用いられる．それらの対策工法の設計には地盤の透気係数や影響半径が必要となり，透気係数や影響半径を求めるために現場透気試験がこれまでも行われてきた．しかし，これまでに，現場透気試験により得られた結果の整理方法については十分に検討されなかった．そこで，本論文では，井戸やボーリング孔より空気を吸引する場合の理論解と軸対称の有限要素法の数値解析を比較して理論式の特徴を整理し，その結果を基に透気試験と影響半径を求めるための現場透気試験のデータ整理方法を提示した．

本稿では10年以上の長期にわたって継続している地下水揚水法による土壌・地下水浄化対策の評価を行った. また, 汚染物質であるトリクロロエチレンの分解による自然減衰効果についても考察した. 現場では長期にわたる揚水処理を続けた結果, 汚染源及びその周辺の浅層地下水の浄化をほぼ完了した. その過程で汚染物質濃度が環境基準よりも高い時期には揚水量が増えると浄化率が上がり, 環境基準を下回り始めると浄化率の向上が顕著でなくなる傾向を示した. 一方, 自然減衰効果としては, 分解生成物のジクロロエチレン濃度がトリクロロエチレン濃度の約64%に保たれていること, および地下水濃度が環境基準値以下になるまでの修復期間が自然減衰効果により約2年は早まっていることが明らかになった.

This paper evaluated the effects of land use on river water quality in the Kishi and Zakuro Rivers. Both basins are mainly covered by forest and orchards, and especially about 30% of the Zakuro River watershed is orchard. In the field observation, the concentrations of NO3- and Mg2+ in the Zakuro River were observed to be higher than those in the Kishi River from autumn to spring. However, there were no differences in the concentrations of the other ions and COD between both rivers. In order to examine these results, especially the effects on the concentrations of NO3- and COD, nitrogen and COD loadings were calculated using pollutant load factors. The calculation result of nitrogen loading implied that the discharge of nitrogen from the orchards played the most important role in the change in the NO3- concentration of the Zakuro River. In the meantime, there were no differences in COD loadings between both basins and therefore the COD concentrations would be approximately equal.

Recently, the assessing of the natural attenuation capacity in the aquifer, which is called the monitored natural attenuation (MNA), is attempted as a remediation technique for groundwater contamination by the volatile organic compounds (VOCs). The natural attenuation includes the processes of biodegradation, dispersion, dilution, sorption, and volatilization of contaminants. Especially the biodegradation process is often recognized as a dominant destructive attenuation mechanism. In this paper, the characteristics of biodegradation in the aquifer and the effect of natural attenuation capacity were evaluated by the field survey and the numerical simulation at the groundwater remediation site. As a result, the biodegradation rates of trichloroethylene (TCE) and dichloroethylenes (DCEs) were calculated and it was cleared that DCEs were degraded faster than TCE.

Soluble substances of the Kinokawa-river increased down the stream. Excluding weathering of limestone, soluble substances in the upper stream of the catchment covered with forest were very low and main components were HCO-3, SO2-4, Na+, and Ca2+. Soluble substances in the upper stream of the forest catchment with limestone were high and the main components were Ca2+ and HCO-3 Ca2+ and HCO-3 concentrations increased from the upper stream to the middle stream with forest, but Na+, Cl- and SO2-4 concentrations remained unchanged because of weathering of limestone and feldspar. In the lower stream of the catchment with farm land and housing site, the concentrations of Na+, Cl-, NO-3 and SO2-4 were very high. It was concluded from the relation between land uses and water qualities that Na+ and SO2-4 origin were farmland, and Cl- origin was sewage respectively, and NO-3 was derived from both origins. Isotopic study of oxygen and hydrogen indicated that the river water originated from precipitation and isotopic ratios depended on mainly precipitation altitude.

Air sparging coupled with soil vapor extraction has been developed and applied to remove volatile contaminants from subsurface environment instead of groundwater extraction coupled with soil vapor extraction. In this paper, laboratory experiments, using 1mm glass beads as the porous medium, were conducted to examine air sparging performance. The purpose of these experiments was to observe the basic mechanisms of injected air and water flows in saturated porous medium during air sparging. The results obtained in this study were the following. The continuous air channels formed inside the porous medium when the grain size of the medium was 1 mm. The pulsed operation for air injection spread the region of injected air flow more than in the continuous operation. Water in the medium gradually moved outside the air flow region by pulsed operation.

The flux of NO-3 and BOD values in the Yamato river water directly increased with precipitation. Therefore, the NO-3 was considered to originate mainly from fertilizer (A) because it was reported that the flux of NO-3in farmland drainage increased with precipitation, although domestic sewage (B) also contains a lot of NO-3. As sediments in the river channels and drains containing organic compounds migrated on rainy days, river BOD values are considered to increase after rain. On the other hand, NO-3origins in branch rivers of the Yamato river are various combinations of (A) and (B). The NO-3origins of branch rivers were determined by whether the flux of NO-3 increased with the flow rate or not. On the other hand, CF concentration in the Yamato river water is considered to strongly depend on the amount of domestic sewage. Although the flow rate in the river changed remarkably due to heavy rains, the flux of CF remained unchanged because the volume of domestic sewage did not change even on a rainy day.

BOD指標の第1位の清流な河川である札内川 (平成7年度) とBOD指標ワースト1の大和川 (平成7年度) の支流石川について, 土地利用特性を考慮して河川水質の比較を行った. その結果, 札内川では中流域の農地において河川水は硝酸イオンに富んでいた. 硝酸イオンの単位面積負荷量は札内川の方が高い値を示し, 施肥等の影響が強いものと考えられる. また, 流域人口の違いは塩素イオン濃度に大きな影響を与えることが分かった. 酸素・水素同位体比より札内川の方が蒸発速度の速い気団が供給源となっていることが推定された. さらに, 両流域の比較によって酸素同位体比の緯度効果が確認された.

Sources of water and soluble substances in the river and groundwater were studied. As the δ D andδ18O values of river and groundwater were on the meteoric line and these values varied with sampling altitudes, these waters were thought to have arisen from precipitation. CO2 pressure in river and groundwater were estimated to be high from pH values and HCO 3- and were equilibrated with CO2 pressure in soil. The δ 13C values of river and groundwater were in agreement with that of soil. High CO2 pressure derived from soil was thought to cause weathering of feldspar in rock and to increase HCO3- and Ca2+ concentration in waters. As the δ 15N values of NO3- in river water varied with land use of sampling pints, the source of nitrogen contamination could be estimated from δ 15N values of NO3- in waters.

The groundwater pollution due to volatile organochlorines like trichloroethylene and tetrachloroethylene has been a great environmental issue in Japan. The nation wide survey revealed on the basis of up to fifty-nine thousand samples collected until 1995 that 1.5% for trichloroethylene and 2.3% for tetrachloroethylene cannot meet the drinking water standard. In order to repair subsurface pollution and to establish the integrated procedure for cost-benefit remediation measure, physical remediation technologies of soil vapor extraction and groundwater extraction were applied to a study site contaminated with trichloroethylene. The results showed that the trichloroethylene amounts of 472 kg by soil vapor extraction and 1764 kg by groundwater extraction were removed during three-year operation. In addition experience with both technologies has demonstrated that the soil vapor extraction has been successful in removing 1 kg hr−1 of trichloroethylene at the initial stage of remediation, which shows one order as high as the groundwater extraction. However, the removal rate due to soil vapor extraction declines much earlier than groundwater extraction, and consequently the removal rates of both technologies develop inversely with the progress of remediation. Such remediation behavior of technologies raised the relative cost for soil vapor extraction 15 times as high as groundwater extraction.

It is important that it makes clear cyclic process of water and water balance in urban river. But, the process of water cycle and water balance have not been made clear in the hydrologic system, because many factors are each other influenced complicatedly and that it is not elucidated in real basin.In this study, we attempt to clarity the process of water cycle in a watershed of the Ishikawa river with a discharge area of 220 km2 by environmental isotope tracers. Both geochemical data which are EC, δ18 O etc. and river discharge are directly measured at many points.As result, it is obvious that cyclic process of river water and water balance are grasped through geochemical data and field observation from macroscopic point.

Groundwater contamination due to chlorinated hydrocarbons like trichloroethylene and tetrachloroethylene has been a great environmental issue in Japan. Because these substances are volatile and little soluble in water, and can exist in unsaturated zone as vaporized, dissolved and undiluted non-aqueous phases, they migrate as gas-water-liquid three phase flow in subsurface. Recently, the air sparging coupled with the soil vapor extraction as the physical remediation technologies has been applied to a site contaminated with chlorinated hydrocarbons. The air sparging technology facilitates the contaminant volatilization with air injected into saturated zone and the soil vapor extraction technology extracts the contaminant in soil and injected gas. Therefore, in order to establish these technologies, it is indispensable to understand the mechanism of gas-water two phase flow in subsurface.

Chlorinated hydrocarbons (CHCs) are highly volatile and little soluble in water, and can exist in unsaturated zone as vaporized, dissolved and undiluted non-aqueous phases. Therefore, it is of great importance to understand transport mechanism of CHCs with gas advection and diffusion in unsaturated zone, and then numerical analysis for vertical transport of CHCs in unsaturated zoneincluding effect of rainfall was conducted. Vertical one-dimensional fluid flow equations and mass transport equations for water and gas phases, and two layer model for mass transfer between the phases were employed in the model presented. The results showed that, though gas phase transport is usually dominant during dry period in unsaturated zone, transport in water phase overcomes that in gas phase during rainwater percolating period.

Recently, a vacuum extraction method is expected as the recovery method for the comtaminated groundwater by chlorinated hydrocarbons (CHC). In order to make an effective in situ remediation, it is indispensable to understand the mechanism of CHC gas transport and the volatilization-dissolution as well as the transport through water phase in the aquifer.In this paper, the numerical simulation in cylindrical two-dimensional model has been carried out to evaluate the CHC transport in the unsaturated zone and the volatilization-dissolution between the phases. As a result, it was found that the gas transport influences the CHC concentration in the unsaturated zone where the water flow is less dominant and the nonequilibrium state is significant during the initial stage.

本論文では, 水に溶解した有機塩素化合物の不飽和-飽和領域における輸送特性を不飽和土壌中でのガス拡散を考慮して検討した. まず, 不飽和土壌中における有機塩素化合物の液相-気相間での揮発・溶解を伴った輸送現象を鉛直1次元カラム実験と数値計算との比較により明らかにした. 次いで, 数値計算モデルを断面2次元不飽和-飽和領域に適用して, 揮発およびガス拡散が地下水中汚染物質濃度へ与える影響について明らかにした.

In the present paper, the simulation results of infiltration of trichloroethylene from the natural river bed to groundwater region is shown. The method of characteristics (MOC) and iterated alternating direction implicit method (IADI) was applied to the computation of two-dimensional convection-dispersion equation and groundwater flow equation. It was found that the infiltration from the river bed when the groundwater level was high in the steady state becomes large while small when the level was low. In the transient period of the groundwater table from high to low or from low to high levels, spread of trichloroethylene showed an opposite tendency due to the unsteady velocity field which contributes to the convection of mass transport.