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  • J-STAGE (Japan Science and Technology Agency)  (10)
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  • J-STAGE (Japan Science and Technology Agency)  (10)
  • 1
    Language: English
    In: SOILS AND FOUNDATIONS, 2011, Vol.51(1), pp.123-132
    Description: Colloid-facilitated transport enhances migration of strongly sorbing compounds (e.g., radionuclides, phosphorus, heavy metals) in soil and groundwater. Mobilization, transport and deposition of soil colloids are the underlying processes governing colloid-facilitated contaminant transport. Although significant progress has been made in simulating mobilization and transport/deposition of model colloids in different collector systems, it may be inadequate for the prediction of natural colloidal behavior in the subsurface. This study quantifies the leaching of natural volcanic ash soil colloids (NC) as well as the simultaneous transport of applied water dispersible soil colloids (WDC) in aggregated volcanic ash soil columns. Two water-saturated soil columns were irrigated with artificial irrigation water (AIW) at an intensity of 80 mm/hr for 60 hours. Two additional columns were irrigated at the same intensity, but a colloidal suspension of 5 mg/L was applied after 20 hours for a period of 20 hours. Effluent colloid concentrations were measured in each experiment. HYDRUS-1D was used for the simulation and estimation of colloid transport parameters. The results clearly showed different kinetics for applied colloid transport and natural colloid leaching. Transport of applied WDC followed first-order attachment kinetics, while the two-site equilibrium/kinetic model with equal fractions of equilibrium and kinetic sites best described the leaching of NC. Coupling these best model approaches well predicted the simultaneous leaching of natural and applied colloids, hereby providing a useful tool for the design of colloid-based in-situ soil remediation systems.〈br〉
    Keywords: Chemical Non-Equlibrium ; Column Experiment ; Leaching ; Soil Colloids ; Two-Site Equilibrium/Kinetic Model ; Volcanic Ash Soil ; Water Dispersible Colloids ; (≪B≫Igc≪/B≫: D4/E7)
    ISSN: 0038-0806
    E-ISSN: 18811418
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  • 2
    Language: Japanese
    In: 土木学会論文集G(環境), 2013, Vol.69(7), pp.III_571-III_579
    Description:  本研究ではPPCPsの一群である3種類の香料成分(OTNE, HHCB, AHTN)と抗菌剤であるtriclosanを対象として下水処理場内への流入と放流濃度を測定し, 除去率を導出した, また広島湾北部域での底質濃度分布を測定した. それに基づき広島湾流入城を対象として処理場からの流出と湾内への堆積負荷を導出し, それぞれの物質収支を検討した. 流域内での下水処理場を経由する負荷は流入においてはそれぞれ200-1000kg yr〈sup〉-1〈/sup〉, 流出は0-600kg yr〈sup〉-1〈/sup〉であった. 広島湾北部の底質への堆積負荷はそれぞれ0-4kg yr〈sup〉-1〈/sup〉であり, 下水処理場からの流出負荷は広島湾の堆積負荷と比較して高いという結果が得られた. 更に関連する物質の濃度を測定しその動態を考察した.
    Description:  The concentrations and mass flow rates of three polycyclic musk fragrances OTNE, HHCB, and AHTN, a bactericide triclosan were examined in a sewage treatment plant and coastal marine sediments in the Hiroshima bay area, Japan. Based on the results, the total emission and sedimentation loadings in the bay area was evaluated. The total sewage influent loadings in the area were estimated to be 200-1000 kg yr〈sup〉-1〈/sup〉, respectively, whereas the effluent loadings from sewage treatment plants were 0-600 kg yr〈sup〉-1〈/sup〉. The sedimentation loadings in the bay area were far lower than the effluent loadings and were 0-4 kg yr〈sup〉-1〈/sup〉, respectively. Further, the concentrations of related chemicals were measured and their behaviors were discussed.
    Keywords: Ppcps ; Polycyclic Musks ; Triclosan ; Sewage Treatment Plant ; Loadings ; Marine Sediments
    ISSN: 2185-6648
    ISSN: Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research)
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  • 3
    Language: English
    In: SOILS AND FOUNDATIONS, 2008, Vol.48(3), pp.397-406
    Description: Risk assessment and design of remediation methods at soil sites polluted with gaseous phase contaminant require an accurate description of soil-gas diffusion coefficient (〈i〉D〈/i〉〈sub〉p〈/sub〉) which is typically governed by the variations in soil air-filled porosity (〈i〉v〈/i〉〈sub〉a〈/sub〉). For undisturbed volcanic ash soils, recent studies have shown that a linear 〈i〉D〈/i〉〈sub〉p〈/sub〉(〈i〉v〈/i〉〈sub〉a〈/sub〉) model, taking into account inactive air-filled pore space (threshold soil-air content, 〈i〉v〈/i〉〈sub〉a, th〈/sub〉), captured the 〈i〉D〈/i〉〈sub〉p〈/sub〉 data across the total soil moisture range from wet to completely dry conditions. In this study, we developed a simple, easy to apply, and still accurate linear 〈i〉D〈/i〉〈sub〉p〈/sub〉(〈i〉v〈/i〉〈sub〉a〈/sub〉) model for undisturbed volcanic ash soils. The model slope 〈i〉C〈/i〉 and intercept (interpreted as 〈i〉v〈/i〉〈sub〉a, th〈/sub〉) were derived using the classical Buckingham (1904) 〈i〉D〈/i〉〈sub〉p〈/sub〉(〈i〉v〈/i〉〈sub〉a〈/sub〉) power-law model, 〈i〉v〈/i〉〈sub〉a〈/sub〉〈sup〉〈i〉X〈/i〉〈/sup〉, at two soil-water matric potentials of pF 2 (near field capacity condition) and pF 4.1 (near wilting point condition), and assuming the same value for the Buckingham exponent (〈i〉X〈/i〉=2.3) in agreement with measured data. This linear 〈i〉D〈/i〉〈sub〉p〈/sub〉(〈i〉v〈/i〉〈sub〉a〈/sub〉) prediction model performed better than the traditionally-used non-linear 〈i〉D〈/i〉〈sub〉p〈/sub〉(〈i〉v〈/i〉〈sub〉a〈/sub〉) models, especially at dry soil conditions, when tested against several independent data sets from literature. Model parameter sensitivity analysis on soil compaction effects showed that a decrease in slope 〈i〉C〈/i〉 and 〈i〉v〈/i〉〈sub〉a, th〈/sub〉 due to uniaxial reduction of air-filled pore space in between aggregates markedly affects the magnitude of soil-gas diffusivity. We recommend the new 〈i〉D〈/i〉〈sub〉p〈/sub〉(〈i〉v〈/i〉〈sub〉a〈/sub〉) model using only the soil-air contents at two soil-water matric potential conditions (field capacity and wilting point) for a rapid assessment of the entire 〈i〉D〈/i〉〈sub〉p〈/sub〉-〈i〉v〈/i〉〈sub〉a〈/sub〉 function.〈br〉
    Keywords: Air-Filled Porosity ; Soil-Gas Diffusion Coefficient ; Soil-Gas Diffusivity ; Soil-Water Retention ; Volcanic Ash Soil ; (≪B≫Igc≪/B≫: D4/E14)
    ISSN: 0038-0806
    E-ISSN: 18811418
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  • 4
    Language: English
    In: Journal of Environmental Chemistry, 1998, Vol.8(4), pp.769-779
    Description: Adsorption and desorption isotherms of Simazine on a decomposed granitic (DG) soil, two natural loam soils, and selected soil particle size fractions were measured in batch experiments. Soil-water content (air-dry compared to oven-dry) markedly influenced the amounts of simazine adsorbed and desorbed on the low-organic DG soil and its soil size fractions while only slight effects were observed for the higher-organic loam soils and their soil size fractions. Decreasing adsorption and increasing desorption with increasing pH was observed for all soils. For both DG and loam, the largest soil size fraction (1.0-2.0 mm) was the most effective adsorber based on unit surface area. The Freundlich isotherm equation well described the measured adsorption and desorption data. The Freundlich adsorption and desorption coefficients (k〈SUB〉f, a〈/SUB〉 and k〈SUB〉f, d〈/SUB〉) were both highly correlated with specific surface area for the DG and soil organic matter content for the loam. Also, k〈SUB〉f, d〈/SUB〉 was highly correlated with k〈SUB〉f, a〈/SUB〉 Three step desorption experiments gave a final desorption of simazine from the DG soil and its size fractions between 91-95 % of the total amount initially adsorbed compared to only 12-22 % for the loam soils and their size fractions. Minor sorption hysteresis was observed for DG. Large hysteresis effects were seen for the loam soils where the hysteresis index was controlled by the soil organic matter content. The difference in sorption characteristics and hysteresis for the two soil types was confirmed in micro-column transport experiments, where significant retardation and tailing of the simazine effluent concentration curve was observed only for the loam soil.
    Keywords: Simazine ; Adsorption ; Desorption ; Pre-Treatment Effects ; Ph Effects ; Sorption Hysteresis
    ISSN: 0917-2408
    E-ISSN: 18825818
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  • 5
    Language: English
    In: Journal of Environmental Chemistry, 1998, Vol.8(2), pp.259-266
    Description: Adsorption and desorption of simazine on a Hiroshima loam soil and its colloidal size fractions were studied in batch experiments. The colloidal size fractions were isolated by repeated gravity sedimentation. Two-step sorption kinetics (step I-with initially non-polluted soil and step II-with soil initially polluted during step I) were well described by a modified Freundlich type kinetics sorption model. Both for the whole soil and soil size fractions the sorption kinetics were characterized by a rapid initial adsorption where the major part of the pesticide was adsorbed within the first 10 minutes followed by a slow, diffusion-controlled sorption. The sorption kinetics parameter N was well correlated with soil organic matter content, and N decreased from step I to step II, dependent on the total amount of simazine adsorbed during step I. This suggests that adsorption kinetics were controlled by both the actual organic matter content and the previous sorption history of each soil size fraction. Adsorption and desorption isotherms for whole soil and loam soil size fractions were well described by the classical Freundlich isotherm equation. A fine silt size fraction with a relatively higher soil organic matter content adsorbed the most simazine and, also, released the least simazine after 10 steps desorption. A large difference between the adsorption and desorption isotherms and therefore a hysteretic sorption behavior for all soil size fractions was observed. Significant correlation was found between adsorption and desorption coefficients and the soil organic matter content.
    Keywords: Simazine ; Soil Colloidal Size Fractions ; Adsorption ; Desorption ; Kinetics
    ISSN: 0917-2408
    E-ISSN: 18825818
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  • 6
    Language: Japanese
    In: 土木学会論文集, 1997, Vol.1997(559), pp.13-22
    Description: テトラクロロエチレン, ベンゼンなどの揮発性有機化合物 (Volatile Organic Chemicals) の土壌内挙動を把握するために, VOCsの移動特性を評価する指標として遅延係数に着目し, マイクロカラムを用いてガスクロマトグラフによる簡便な遅延係数決定法を提案した. この方法は, 移流分散の条件下でVOCs (気体) の遅延を測定するもので, 同時に移動パラメータ (流速, 分散係数) を決定することができる. テトラクロロエチレン, トリクロロエタンについて流速, 温度, 有機物量, カラム長などの遅延係数に与える影響を検討した結果, 流速, カラム長の影響は小さい, 温度の低下とともに, また有機物量の増加とともに遅延係数は大きくなる, 温度, 有機物量の移動パラメータに与える影響は小さい, ことなどが確認された.
    Description: A new gas chromatography (GC) based micro-column method to determine the retardation factor and other transport parameters that govern the movement of Volatile Organic Chemicals (VOCs) in soils is presented. The retardation factors as well as the mean gas velocity and dispersion coefficient of 1, 1, 1-trichloroethane and tetrachloroethylene were measured under convective gas flow conditions, using the GC-micro column method. The study showed that the effects of gas velocity and column length on retardation factors in GC-columns (Chromosorb W, P) were small. The values of retardation factors as expected increased with decreasing temperature and increasing organic matter content.
    Keywords: Gaseous Volatile Organic Chemicals (Vocs) ; Retardation Factor ; Transport Parameters ; Gc-Micro-Column Method
    ISSN: 0289-7806
    E-ISSN: 18827187
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  • 7
    Language: Japanese
    In: 土木学会論文集, 1997, Vol.1997(559), pp.23-29
    Description: 土壌ガス吸引法 (SV法) は揮発性有機化合物 (VOC) によって汚染された土壌の浄化法として広く用いられているが, SV法による土壌浄化の効果を把握するするためには移流分散の条件下でのVOCの挙動を明らかにする必要がある. 本研究ではVVOC (気体) の遅延係数を土壌マイクロカラム法により測定し, VOCの土壌内移動特性に与える流速, 温度, 土壌水分, 土壌特性などの影響について検討した. 得られた結果は次のとおりである. 流速, カラム形状は遅延係数にほとんど影響しない. 温度の低下に伴って遅延係数の値は増加し, 温度の効果は土壌水分が小さい範囲で著しい. 土壌特性により遅延係数は大きく変化し, 表面積の小さい土壌では, 土壌永分の遅延係数に与える影響が大きいことが認められた.
    Description: Soil venting (soil vapor extraction) techniques are widely used to remove Volatile Organic Chemicals (VOCs) from polluted soil sites. The purpose of this study is to evaluate the mobility of VOCs in soils under soil-venting conditions, i. e., rapid, convective-dispersive gas transport conditions. Retardation of VOCs (1, 1, 1-trichloroethane and toluene) in decomposed granite (Mass) and a clayey soil (Yolo loam) was determined using a newly developed soil micro-column method based on gas chromatography. The effect of gas flow rate, soil temperature, soil column dimensions and soil -water content was investigated. In dry soils, even small decreases in water content gave one or several orders of magnitude increase in VOC retardation, probably due to direct adsorption of the VOC's onto the soil minerals.
    Keywords: Gaseous Volatile Organic Chemicals (Vocs) ; Retardation Factor ; Soil Venting ; Convective-Dispersive Gas Transport ; Gc-Micro-Column Method
    ISSN: 0289-7806
    E-ISSN: 18827187
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  • 8
    Language: Japanese
    In: 土木学会論文集, 2001, Vol.2001(678), pp.111-122
    Description: 近年, コロイド粒子に吸着した汚染物質の土壌内移動が注目されるようになってきた. 本研究では汚染物質の運び手となる土壌コロイド粒子の降雨時における移動について, 不撹乱・撹乱土壌を用いたカラム実験により検討を行った. その結果, 撹乱土壌では不撹乱土壌に比べてコロイド粒子の流出量が多いことが分かった. また, 降雨強度が小さい場合, 雨水中にNa〈sup〉+〈/sup〉を含む場合および雨水のイオン強度が小さい場合にはコロイド粒子の流出量が多くなること, 土壌中に macropore がある場合はない場合に比べ降雨初期にコロイドの流出量が多いが全流出量は少ないことが明らかになった. モデル解析の結果から, macropore がある場合はコロイド粒子の流出は拡散律速であることが示された.
    Description: This study investigated soil colloid mobilization and leaching through a Hiroshima loam soil during three irrigation periods. The experiments were carried out using both intact soil columns and repacked columns with and without continuous macropores. Large effects of irrigation intensity and of irrigation water chemical composition (sodium content and ionic strength) were seen. Colloid leaching was higher in repacked soil than in undisturbed soil. During the first irrigation, an enhanced colloid leaching in soil containing macropores was seen, but during the next two irrigation the leaching became smaller and could be described by a parabolic diffusion type model. This suggests that the mobilization of colloids is controlled by colloid diffusion from the soil into the macropores. This mechanism needs to be included in models for transport of colloid-bound contaminants in macropore soils.
    Keywords: Soil Colloid Transport ; Soil Siructure ; Macropores ; Irrigation Intensity ; Turbidity ; Parabolic Diffusion Model
    ISSN: 0289-7806
    E-ISSN: 18827187
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  • 9
    Language: Japanese
    In: 土木学会論文集, 2002, Vol.2002(706), pp.61-76
    Description: 汚染物質のキャリアーとなり得るコロイド粒子と溶存有機物の降雨による表層土壌からの移動についてカラム実験により検討した. その結果, 無機・有機コロイドと溶存有機物の流出挙動はそれぞれ異なる, 降雨強度の影響は特に見られない, macropore の存在により無機・有機コロイドおよび溶存有機物のいずれも流出量が増加することなどが明らかとなった. 土壌から流出するコロイド粒子のうち約93%が無機性, 約7%が有機性であった. 流出する有機物のうち約14%が有機性コロイド, 約84%が溶存有機物, 約2%が粒子状有機物であった. 環境中において有機コロイドや溶存有機物により輸送が促進されるベンゾ (a) ピレンの地下水への流出濃度は約4.9×10〈sup〉-3〈/sup〉(μg/L) と試算され, その危険性が示唆された.
    Description: This study investigated mobilization and leaching of three natural soil constituents, inorganic colloidal matter (ICM), colloidal organic carbon (COC) and dissolved organic carbon (DOC) from a surface soil (loam) during repeated irrigation events. IMC, COC and DOC showed widely different leaching behavior and, also, behaved differently in soil with and without continuous macropores. COC contributed with only 7% to total colloid leaching. However, DOC dominated total organic carbon leaching with a contribution of 84%. Using these results, calculations on transport of a strongly sorbing Benzo (a) pyrene suggested that DOC-facilitated transport could be a dominating part of Benzo (a) pyrene transport, and potentially violate drinking water criteria indicated by IRIS of EPA.
    Keywords: Colloid Transport ; Dissolved Organic Carbon (Doc) Transport ; Macropores ; Long-Term Continuous Irrigation ; Doc Facilitated Pahs Transport
    ISSN: 0289-7806
    E-ISSN: 18827187
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  • 10
    Language: Japanese
    In: 土木学会論文集C, 2009, Vol.65(2), pp.579-586
    Description:  原位置通気係数(〈i〉K〈sub〉a, insitu〈/sub〉〈/i〉)は,比較的低コストかつ迅速測定が可能であり,地盤内でのガスや水の移動特性を把握する上で非常に有効な物質移動パラメータである.一般に,〈i〉K〈sub〉a, insitu〈/sub〉〈/i〉の計算には,地盤内の三次元空気流れを考慮するための形状係数が組み込まれる.本研究では,有限要素法による数値解析により地盤内空気流れをシミュレーションし,得られた形状係数や〈i〉K〈sub〉a, insitu〈/sub〉〈/i〉を既往の研究結果と比較するとともに,形状係数に横境界や下端境界条件の変化が及ぼす影響を数値解析および模型実験により検証した.その結果,〈i〉K〈sub〉a, insitu〈/sub〉〈/i〉測定時の下端境界条件が形状係数や〈i〉K〈sub〉a, insitu〈/sub〉〈/i〉に大きな影響を与えることが明らかにされた.特に,地盤表層付近に不透気層が存在する場合は,調査地点での境界条件を考慮した形状係数を求め,Ka, insitu を適切に算出することが必要である.
    Description:   In-situ air permeability (〈i〉K〈sub〉a, insitu〈/sub〉〈/i〉) is a rapid field measurement that provides important information on soil-gas and water transport properties in soil. The 〈i〉K〈sub〉a, insitu〈/sub〉〈/i〉 can be determined by using a shape factor taking account of field flow geometry effects on one-dimensional air flow. In this study, effects of lateral and bottom boundary conditions on the shape factor (〈i〉G〈/i〉) and subsequent 〈i〉K〈sub〉a, insitu〈/sub〉〈/i〉 were investigated by combining finite-element numerical simulations and a model experiment with repacked sand in a container. Results showed that calculated and measured values of 〈i〉G〈/i〉 and 〈i〉K〈sub〉a, insitu〈/sub〉〈/i〉 were highly dependent on the bottom boundary, and especially that a shallow zero-flux bottom boundary caused an underestimation of 〈i〉K〈sub〉a, insitu〈/sub〉〈/i〉. This shows that special care must be taken to determine the shape factor with due consideration to the proper boundary conditions. This is especially critical in the case of impermeable layers such as highly-compacted subsurface soil or a shallow groundwater table.
    Keywords: In-Situ Air Permeability ; Shape Factor ; Impermeable Layer ; Numerical Simulation
    ISSN: 1880-604X
    Source: Japan Science and Technology Agency
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