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Per Moldrup - One of the best experts on this subject based on the ideXlab platform.
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the solute diffusion coefficient in variably compacted unsaturated Volcanic Ash Soils
Vadose Zone Journal, 2009Co-Authors: Shoichiro Hamamoto, Ken Kawamoto, Toshiko Komatsu, Augustus C Resurreccion, M S A Perera, Shuichi Hasegawa, Per MoldrupAbstract:The solute diffusion coefficient in soil ( D s ) and its dependency on the soil water content (θ), soil type, and compaction govern the transport and fate of dissolved chemicals in the soil vadose zone. Only a few studies have quantified solute diffusivity ( D s / D 0 , where D s and D 0 are the solute diffusion coefficients in soil and pure water, respectively) for variably compacted Soils with different textures. We measured the D s for KCl on five different Soils from Japan: two Volcanic Ash Soils (Andisols) at different bulk densities, two sandy Soils, and a loamy soil. The D s was measured across a wide range of θ using the half-cell method. The D s / D 0 values for Andisols with bimodal pore size distribution were comparatively lower than for the other Soils. Opposite to the behavior for sandy Soils, the D s / D 0 for Andisols at a given θ decreased markedly with increasing bulk density under wet conditions but increased with increasing bulk density under dry conditions. Data for all soil types including sandy Soils with unimodal pore size distribution implied a two-region behavior when plotted as log( D s / D 0 ) vs. θ. We suggest that the similar behavior across soil types can be explained by regions of low and high water phase connectivity for relatively structureless Soils and by high intraaggregate and low interaggregate water phase tortuosity for aggregated Soils. Among a number of tested predictive models for D s / D 0 , the Penman–Millington–Quirk model, which requires knowledge of only θ and total porosity, performed best across soil types.
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Adsorption of 2,4-dichlorophenoxyacetic acid onto Volcanic Ash Soils: effects of pH and soil organic matter.
EnvironmentAsia, 2009Co-Authors: Ei Ei Mon, Syuntaro Hiradate, Taiki Hirata, Ken Kawamoto, Toshiko Komatsu, Per MoldrupAbstract:The quantification of the linear adsorption coefficient (Kd) for Soils plays a vital role to predict fate and transport of pesticides in the soil-water environment. In this study, we measured Kd values for 2,4-Dichlorophenoxyacetic acid (2,4-D) adsorption onto Japanese Volcanic Ash Soils with different amount of soil organic matter (SOM) in batch experiments under different pH conditions. All measurements followed well both linear and Freundlich adsorption isotherms. Strong correlations were found between measured Kd values and pH as well as SOM. The 2,4-D adsorption increased with decreasing pH and with increasing SOM. Based on the data, a predictive Kd equation for Volcanic Ash Soils, log (Kd) = 2.04 0.37 pH + 0.91 log (SOM), was obtained by the multiple regression analysis. The predictive Kd equation was tested against measured 2,4-D sorption data for other Volcanic Ash Soils and normal mineral Soils from literature. The proposed Kd equation well predicted Kd values for other Volcanic Ash Soils and slightly overor under-predicted Kd values for normal mineral Soils. The proposed Kd equation performed well against Volcanic Ash Soils from different sites and countries, and is therefore recommended for predicting Kd values at different pH and SOM conditions for Volcanic Ash Soils when calculating and predicting 2,4-D mobility and fate in soil and groundwater.
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linear model to predict soil gas diffusivity from two soil water retention points in unsaturated Volcanic Ash Soils
Soils and Foundations, 2008Co-Authors: Augustus C Resurreccion, Ken Kawamoto, Toshiko Komatsu, Seiko Yoshikawa, Masanobu Oda, Per MoldrupAbstract:Risk assessment and design of remediation methods at soil sites polluted with gaseous phase contaminant require an accurate description of soil-gas diffusion coefficient (Dp) which is typically governed by the variations in soil air-filled porosity (va). For undisturbed Volcanic Ash Soils, recent studies have shown that a linear Dp(va) model, taking into account inactive air-filled pore space (threshold soil-air content, va, th), captured the Dp 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 Dp(va) model for undisturbed Volcanic Ash Soils. The model slope C and intercept (interpreted as va, th) were derived using the classical Buckingham (1904) Dp(va) power-law model, vaX, 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 (X=2.3) in agreement with measured data. This linear Dp(va) prediction model performed better than the traditionally-used non-linear Dp(va) 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 C and va, th due to uniaxial reduction of air-filled pore space in between aggregates markedly affects the magnitude of soil-gas diffusivity. We recommend the new Dp(va) 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 Dp-va function.
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Air Permeability in Undisturbed Volcanic Ash Soils
Soil Science Society of America Journal, 2003Co-Authors: Per Moldrup, Toshiko Komatsu, Seiko Yoshikawa, Torben Olesen, Dennis E. RolstonAbstract:Soil air permeability (k a ) governs convective air and gas transport in soil. The increased use of soil venting systems during vadose zone remediation at polluted soil sites has created a renewed interest in k a and its dependency on soil type and soil air-filled porosity (e). Predictive k a (e) models have only been tested within limited ranges of pore-size distribution and total porosity. Andisols (Volcanic Ash Soils) exhibit unusually high porosities and water retention properties. In this study, measurements of k a (e) on 16 undisturbed Andisols from three locations in Japan were carried out in the soil matric potential interval from -10 cm H 2 O (near water saturation) to -15 000 cm H 2 O (wilting point). Two simple power-function k a (e) models, both with measured k, at -100 cm H 2 O as a reference point, gave similar and good predictions of k a (e) between -10 and -1000 cm H 2 O. For one location comprising finely textured and humic Andisols, both models largely underpredicted k,(e) in dry soil (
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Gas Diffusivity in Undisturbed Volcanic Ash Soils
Soil Science Society of America Journal, 2003Co-Authors: Per Moldrup, Toshiko Komatsu, Seiko Yoshikawa, Torben Olesen, Dennis E. RolstonAbstract:Soil-water-characteristic-dependent (SWC-dependent) models to predict the gas diffusion coefficient. D r , in undisturbed soil have only been tested within limited ranges of pore-size distribution and total porosity. Andisols (Volcanic Ash Soils) exhibit unusually high porosities and water retention properties. The Campbell SWC model and two Campbell SWC-based models for predicting Dp in undisturbed soil were tested against SWC and Dp data for 18 Andisols and four Gray-lowland (paddy field) Soils from Japan. The Campbell model accurately described SWC data for all 22 Soils within the matric potential range from -10 to -15 000 cm H 2 O. The SWC-dependent Buckingham-Burdine-Campbell (BBC) gas diffusivity model predicted Dp data well within the same matric potential range for the 18 Andisols. The BBC model showed a minor but systematic underprediction of Dp for three out of the four Gray-lowland Soils, likely due to a blocky soil structure with internal fissures. A recent Dp model that also takes into account macroporosity performed nearly as well as the BBC model. However, Dp in the macropore region (air-filled pores >30 μm) was consistently underpredicted, likely due to high continuity of the macropore system in both Andisols and Gray-lowland Soils. In agreement with previous model tests for 21 European Soils (representing lower porosities and water retention properties), both SWC-dependent D p models gave better predictions for the 22 Japanese Soils than soil-type independent models. Combining Dp and SWC data, a so-called gas diffusion fingerprint (GDF) plot to describe soil aeration potential is proposed.
Giovanny M Mosquera - One of the best experts on this subject based on the ideXlab platform.
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water transport and tracer mixing in Volcanic Ash Soils at a tropical hillslope a wet layered sloping sponge
Hydrological Processes, 2020Co-Authors: Giovanny M Mosquera, Patricio Crespo, Lutz Breuer, Jan Feyen, David WindhorstAbstract:Andosol Soils formed in Volcanic Ash provide key hydrological services in montane environments. To unravel the subsurface water transport and tracer mixing in these Soils we conducted a detailed characterization of soil properties and analyzed a 3‐year data set of sub‐hourly hydrometric and weekly stable isotope data collected at three locations along a steep hillslope. A weakly developed (52–61 cm depth), highly organic andic (Ah) horizon overlaying a mineral (C) horizon was identified, both showing relatively similar properties and subsurface flow dynamics along the hillslope. Soil moisture observations in the Ah horizon showed a fast responding (few hours) “rooted” layer to a depth of 15 cm, overlying a “perched” layer that remained near saturated year‐round. The formation of the latter results from the high organic matter (33–42%) and clay (29–31%) content of the Ah horizon and an abrupt hydraulic conductivity reduction in this layer with respect to the rooted layer above. Isotopic signatures revealed that water resides within this soil horizon for short periods, both at the rooted (2 weeks) and perched (4 weeks) layer. A fast soil moisture reaction during rainfall events was also observed in the C horizon, with response times similar to those in the rooted layer. These results indicate that despite the perched layer, which helps sustain the water storage of the soil, a fast vertical mobilization of water through the entire soil profile occurs during rainfall events. The latter being the result of the fast transmissivity of hydraulic potentials through the porous matrix of the Andosols, as evidenced by the exponential shape of the water retention curves of the subsequent horizons. These findings demonstrate that the hydrological behavior of Volcanic Ash Soils resembles that of a “layered sponge,” in which vertical flow paths dominate.
Zuengsang Chen - One of the best experts on this subject based on the ideXlab platform.
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soil organic carbon stocks in relation to elevation gradients in Volcanic Ash Soils of taiwan
Geoderma, 2013Co-Authors: Chunchih Tsui, Chenchi Tsai, Zuengsang ChenAbstract:Abstract Soil organic carbon (SOC) stocks are controlled by factors with varying degrees of importance at different spatial scales. In this study, soil data were collected from recently sampled pedons and previous studies on Volcanic origin Soils in Yangmingshan (YMS) National Park in northern Taiwan. This study evaluated the effect of soil order, vegetation type and elevation on the SOC stocks of humid subtropical Volcanic Ash Soils. Analysis results indicate that SOC stock (mean ± standard deviation) was 15.6 ± 4.5 kg m − 2 m − 1 (n = 40) for Andisols and 17.3 ± 7.3 kg m − 2 m − 1 (n = 20) for Inceptisols with andic soil properties. Meanwhile, SOC stocks under silver grass (17.4 ± 5.5 kg m − 2 m − 1 , n = 20) and bamboo (17.9 ± 2.5 kg m − 2 m − 1 , n = 8) were significantly higher than those under secondary forests (14.9 ± 6.0 kg m − 2 m − 1 , n = 32). Additionally, statistically significant linear regressions were found between the mean SOC stock and the mean of elevation classes. Climate, vegetation types and soil mineralogy vary along elevation gradients in the complex terrain. Our results demonstrated that elevation is a simple and effective predictor of SOC stock.
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pedogenic development of Volcanic Ash Soils along a climosequence in northern taiwan
Geoderma, 2010Co-Authors: Chenchi Tsai, Zuengsang Chen, C I Kao, Franz Ottner, Shuhji Kao, Franz ZehetnerAbstract:Abstract Andisols have been shown to evolve over time to other, more weathered soil types. However, more information is needed on the time-scales over which these changes occur under different climatic conditions. In this study, we analyze mineral weathering and soil formation along a soil climosequence formed on Volcanic deposits of > 400 ka of age in the subtropical climate of Northern Taiwan. We sampled 6 pedons at elevations between 140 and 1090 m above sea level (asl), representing a climatic gradient from about 22 °C mean annual temperature (MAT) and 2000 mm mean annual precipitation (MAP) to about 16.5 °C MAT and 5000 mm MAP. Our results show that phosphate retention, Al o + 1/2Fe o , Si o and the Fe o /Fe d ratio significantly increased with elevation. The high-elevation Soils (> 900 m asl) contained metastable poorly crystalline materials (e.g. allophane, ferrihydrite) and classified as Andisols, whereas the low-elevation Soils (
Femke H. Tonneijck - One of the best experts on this subject based on the ideXlab platform.
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Towards understanding of carbon stocks and stabilization in Volcanic Ash Soils in natural Andean ecosystems of northern Ecuador
European Journal of Soil Science, 2010Co-Authors: Femke H. Tonneijck, Boris Jansen, Jacobus M. Verstraten, Klaas G.j. Nierop, Jan Sevink, L. De LangeAbstract:Volcanic Ash Soils contain very large stocks of soil organic matter (SOM) per unit area. Consequently, they constitute potential sources or sinks for the greenhouse gas carbon dioxide. Whether Soils become a net carbon source or sink with climate and/or land-use change depends on the stability of SOM against decomposition, which is influenced by stabilization mechanisms in the soil. To quantify organic carbon stocks and to clarify the importance of chemical and physical soil characteristics for carbon stabilization in Volcanic Ash Soils, we applied selective extraction techniques, performed X-ray diffraction analysis of the clay fraction and estimated pore-size distribution of Soils under natural upper montane forest and grassland (paramo) in the Ecuadorian Andes. Our results show that organic carbon stocks under both vegetation types are roughly twice as large as previously reported global averages for Volcanic Ash Soils. SOM stabilization is suggested to be dominantly influenced by the following chemical and physical soil characteristics: (i) direct stabilization of SOM in organo-metallic (Al-humus) complexes, explaining at most 40% of carbon accumulation, (ii) indirect protection of SOM (notably aliphatic compounds) through low soil pH and toxic levels of Al, and probably also (iii) physical protection of SOM caused by a very large micro-porosity. Moreover, in the case of the forest Soils, inherent recalcitrance of OM itself was responsible for substantial accumulation in ectorganic horizons. Both vegetation types contributed to soil acidification, thus increasing SOM accumulation.
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the influence of bioturbation on the vertical distribution of soil organic matter in Volcanic Ash Soils a case study in northern ecuador
European Journal of Soil Science, 2008Co-Authors: Femke H. Tonneijck, A G JongmansAbstract:Soil faunal bioturbation ('bioturbation') is often cited as a major process influencing the vertical distribution of soil organic matter (SOM). The influence of bioturbation on vertical SOM transport is complex because it is the result of interaction between different groups of soil faunal species that redistribute SOM through the soil profile in distinct ways. We performed a semi-quantitative micromorphological analysis of soil faunal pedofeatures and related their occurrence to the vertical distribution of SOM and high-resolution radiocarbon dating in Volcanic Ash Soils under montane forest and grassland (paramo) vegetation in the northern Ecuadorian Andes. The paramo soil data suggest that bioturbation was largely responsible for the vertical distribution of SOM, while illuviation and root input were of minor importance. Bioturbation was caused by endogeic species, which typically mix the soil only over short vertical distances. Short vertical distance mixing was apparently enhanced by the upward shifting of bioturbation as a result of soil thickening due to SOM accumulation. A change from paramo to forest vegetation was accompanied by a change from endogeic to epigeic species. As these latter species do not redistribute material vertically, this eventually resulted in the formation of thick ectorganic horizons in the forest.
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Tephra stratification of Volcanic Ash Soils in Northern Ecuador
Geoderma, 2008Co-Authors: Femke H. Tonneijck, Jan Sevink, Jos A. Hageman, Jacobus M. VerstratenAbstract:We combined proxies traditionally used in stratigraphic research (mineral assemblages, grain size distribution, and element ratios) with soil organic carbon contents and radiocarbon dating both at a high vertical resolution, to unravel the tephra stratigraphy in Volcanic Ash Soils. Our results show that soil profiles along an altitudinal transect intersecting the upper forest line in Northern Ecuador were formed in three distinct tephra deposits. Although the deposits contained a similar assemblage of minerals, we were able to differentiate these deposits because of their characteristic organic carbon distribution, grain size distribution and typical SrO to Na2O, CaO and crystalline Al2O3 ratios. Unravelling the tephra stratigraphy improved understanding of the vertical distribution of soil organic carbon, including paleoecological proxies, in the studied Soils. We demonstrated that bioturbation likely plays an important role in current pedogenesis, resulting in overprinting (merging, mixing) of the paleosol. Surprisingly, in spite of bioturbation, a linear age depth relationship exists, leading to the hypothesis that the active zone of bioturbation shifted upwards during soil formation. Therefore, we conclude that paleoecological proxies are stratified in our Soils, albeit probably somewhat more crudely than in undisturbed peat bogs or lake sediments
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organic matter in Volcanic Ash Soils under forest and paramo along an ecuadorian altitudinal transect
Soil Science Society of America Journal, 2007Co-Authors: Klaas G.j. Nierop, Boris Jansen, Femke H. Tonneijck, J M VerstratenAbstract:The Volcanic Ash Soils along an altitudinal transect in Guandera Biological Station in northern Ecuador have been developed under varying vegetation around the upper forest line. Generally, the Soils currently covered by forest are composed of Fulvic Andosols (melanic index >1.7) while those under paramo (tropical alpine grasslands) have developed into Melanic Andosols. This vegetation effect on soil formation is believed to be associated with differences in organic matter composition. In this study, we examined whether Fulvic Andosols differed from Melanic Andosols in organic matter composition. Using analytical pyrolysis techniques, we found hardly any differences in the organic matter characteristics related to vegetation cover, not even between Soils that supposedly have been covered by forest and paramo for millennia. Small differences were found within the lipid compounds, while the polysaccharides and lignin were virtually absent from the (deeper) mineral soil horizons. The low abundance of polysaccharides in Soils that have undergone severe organic matter decomposition is not unusual for most Soils, but is uncommon in other Andosols studied with the same pyrolysis techniques.
David Windhorst - One of the best experts on this subject based on the ideXlab platform.
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water transport and tracer mixing in Volcanic Ash Soils at a tropical hillslope a wet layered sloping sponge
Hydrological Processes, 2020Co-Authors: Giovanny M Mosquera, Patricio Crespo, Lutz Breuer, Jan Feyen, David WindhorstAbstract:Andosol Soils formed in Volcanic Ash provide key hydrological services in montane environments. To unravel the subsurface water transport and tracer mixing in these Soils we conducted a detailed characterization of soil properties and analyzed a 3‐year data set of sub‐hourly hydrometric and weekly stable isotope data collected at three locations along a steep hillslope. A weakly developed (52–61 cm depth), highly organic andic (Ah) horizon overlaying a mineral (C) horizon was identified, both showing relatively similar properties and subsurface flow dynamics along the hillslope. Soil moisture observations in the Ah horizon showed a fast responding (few hours) “rooted” layer to a depth of 15 cm, overlying a “perched” layer that remained near saturated year‐round. The formation of the latter results from the high organic matter (33–42%) and clay (29–31%) content of the Ah horizon and an abrupt hydraulic conductivity reduction in this layer with respect to the rooted layer above. Isotopic signatures revealed that water resides within this soil horizon for short periods, both at the rooted (2 weeks) and perched (4 weeks) layer. A fast soil moisture reaction during rainfall events was also observed in the C horizon, with response times similar to those in the rooted layer. These results indicate that despite the perched layer, which helps sustain the water storage of the soil, a fast vertical mobilization of water through the entire soil profile occurs during rainfall events. The latter being the result of the fast transmissivity of hydraulic potentials through the porous matrix of the Andosols, as evidenced by the exponential shape of the water retention curves of the subsequent horizons. These findings demonstrate that the hydrological behavior of Volcanic Ash Soils resembles that of a “layered sponge,” in which vertical flow paths dominate.
