The Experts below are selected from a list of 18852 Experts worldwide ranked by ideXlab platform
Mohammad Tajbakhsh - One of the best experts on this subject based on the ideXlab platform.
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Effect of Lime and Rice Husk Ash on Horizontal Saturated Hydraulic Conductivity of Sandy Loam Soils
Geotechnical and Geological Engineering, 2019Co-Authors: Manoochehr Fathi-moghaddam, Mohammad Tavakol-sadrabadi, Mohammad TajbakhshAbstract:Saturated hydraulic conductivity (K_sat) of soil is one of the most frequently used parameters in geotechnical studies especially in the case of structures in permanent contact with water. This property is significantly influenced by pore distribution and surface characteristics of soil particles. In this study, a physical model was utilized to investigate the effect of varying amounts (2, 4 and 6% of weight) of hydrated Lime and hydrated Lime-Rice husk ash mixture (LRHA) with 1:1 ratio on the horizontal hydraulic conductivity (k_sat-h) of a compacted Sandy Loam soil. The horizontal saturated permeability of samples was tested after 28 days of curing. Results indicated that a soil mixture including 4% hydrated lime, increased the initial hydraulic conductivity significantly. While adding greater amounts of lime reduced the K_sat due to the lime filling the pores of the Sandy soil. It is also shown that adding 2% of LRHA had a slight incremental effect on the K_sat. Nevertheless, mixtures including 4% and 6% LRHA led to the reduction of the initial hydraulic conductivity up to 65% and 50% respectively. Comparing the results in the same amount of additives, it can be concluded that the reduced K_sat of mixtures with LRHA is the result of the participation of the LRHA in pozzolanic reactions which reduces the K_sat and not filling the pores of the soil simply.
Philippe Baveye - One of the best experts on this subject based on the ideXlab platform.
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Influence of Anionic Surfactant on Saturated Hydraulic Conductivity of Loamy Sand and Sandy Loam Soils
Water, 2017Co-Authors: Zhenyang Peng, Christophe Darnault, Fuqiang Tian, Philippe BaveyeAbstract:Surfactants released into the terrestrial environment in large amounts can potentially alter the physical, chemical and biological properties of Soils, particularly the saturated hydraulic conductivity (Ks). Unfortunately findings regarding this process are quite limited. In this study, column tests were used to analyze the effects of Aerosol 22, a widely used anionic surfactant, on Ks of Loamy sand and Sandy Loam Soils. Solutions were injected into columns from the bottom with controlled pressure heads. Both the overall Ks of columns and the Ks of 6 layers at distances of 0–1 cm, 1–3 cm, 3–5 cm, 5–7 cm, 7–9 cm, and 9–10 cm from the bottom, were continuously monitored before and after the surfactant injections. Results showed that the overall Ks of all columns decreased after 2–4 pore volumes of the surfactant injections. However, stabilization and even increase at the beginning of the surfactant injection was also observed due to the different Ks variations in different layers. Specifically, a surfactant injection of 2–4 pore volumes continuously decreased the Ks of the 0–1 cm layers which yielded a Ks reduction of two orders of magnitude and dominated the Ks variations of the column. In contrast, an increase in the Ks of the 1–3 cm and 3–5 cm layers was more likely, while Ks variation of the 5–10 cm layers was less likely. We hypothetically attributed the Ks variations to the swelling of clay, the collapse of soil aggregates and subsequent particle displacements from surfactant adsorption, which caused pore clogging in the bottom 0–1 cm layer and higher porosities in the layers above. The adsorption of the surfactant aggregates and crystallization were also possibly thought to cause a pore clogging in the bottom layer thus decrease the surfactant concentration from the inlet, the severity of which affects these layers less at greater distances from the inlet. In view of the uncertainty showed by the experimental results, we also suggest to include more replicate columns in future studies, so as to increase the repeatability of the measurements.
Francesco Morari - One of the best experts on this subject based on the ideXlab platform.
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effects of biochar on the dynamics of aggregate stability in clay and Sandy Loam Soils
European Journal of Soil Science, 2018Co-Authors: Chiara Pituello, Dal N Ferro, Ornella Francioso, Gianluca Simonetti, Antonio Berti, Ilaria Piccoli, Annamaria Pisi, Francesco MorariAbstract:SUMMARY: Recent advances suggest that organic substances of different origins might have different aggregate stability dynamics. We investigated the extent to which contrasting soil types affect the dynamics of aggregation after the addition of crop residues (R) and of biochar at two doses (BC20, 20 Mg ha⁻¹; BC40, 40 Mg ha⁻¹) in a 2‐year experiment. To evaluate disaggregation, we measured a set of physical–chemical and structure‐related properties of clay and Sandy Loam aggregates sieved to 1–2 mm, including wet aggregate stability after different pretreatments combined with laser diffraction analysis. The electrochemical properties of the colloidal suspension were also analysed to identify changes in soil chemistry affected by organic inputs. Different amounts of added biochar and soil types produced contrasting effects on wet aggregate stability. In Sandy Loam, the increased soil surface area from added biochar (at either dose) offset the initial small soil organic carbon (SOC) content and subsequently promoted SOC‐controlled aggregation. Conversely in clay soil, the larger biochar dose (BC40) strengthened the repulsive forces between particles with the same charge and monovalent cations, which led to chemical perturbation and some aggregate breakdown not found with BC20. Pore structure also changed in clay aggregates. A shift towards more micropores (30–5 μm, + 29% more than in the control) and ultramicropores (5–0.1 μm, + 22% more than in the control), which contributed to aggregate stabilization, resulted when biochar was added, but not for residue. Our results suggest that biochar promotes aggregate stability, which, in turn, improves the physical fertility of soil, especially if it has a coarse texture and small organic carbon content. Further study is needed of the physical–chemical interactions between added biochar and surface‐charged clay‐rich Soils. HIGHLIGHTS: Aggregate dynamics are poorly understood because of complex interactions between organic inputs and soil type. A multidisciplinary approach was used to study aggregation dynamics. Large biochar input changed soil chemical properties that weakened stability in clay aggregates. Aggregate stability depended on biochar dose and soil type.
Manoochehr Fathi-moghaddam - One of the best experts on this subject based on the ideXlab platform.
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Effect of Lime and Rice Husk Ash on Horizontal Saturated Hydraulic Conductivity of Sandy Loam Soils
Geotechnical and Geological Engineering, 2019Co-Authors: Manoochehr Fathi-moghaddam, Mohammad Tavakol-sadrabadi, Mohammad TajbakhshAbstract:Saturated hydraulic conductivity (K_sat) of soil is one of the most frequently used parameters in geotechnical studies especially in the case of structures in permanent contact with water. This property is significantly influenced by pore distribution and surface characteristics of soil particles. In this study, a physical model was utilized to investigate the effect of varying amounts (2, 4 and 6% of weight) of hydrated Lime and hydrated Lime-Rice husk ash mixture (LRHA) with 1:1 ratio on the horizontal hydraulic conductivity (k_sat-h) of a compacted Sandy Loam soil. The horizontal saturated permeability of samples was tested after 28 days of curing. Results indicated that a soil mixture including 4% hydrated lime, increased the initial hydraulic conductivity significantly. While adding greater amounts of lime reduced the K_sat due to the lime filling the pores of the Sandy soil. It is also shown that adding 2% of LRHA had a slight incremental effect on the K_sat. Nevertheless, mixtures including 4% and 6% LRHA led to the reduction of the initial hydraulic conductivity up to 65% and 50% respectively. Comparing the results in the same amount of additives, it can be concluded that the reduced K_sat of mixtures with LRHA is the result of the participation of the LRHA in pozzolanic reactions which reduces the K_sat and not filling the pores of the soil simply.
Zhenyang Peng - One of the best experts on this subject based on the ideXlab platform.
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Influence of Anionic Surfactant on Saturated Hydraulic Conductivity of Loamy Sand and Sandy Loam Soils
Water, 2017Co-Authors: Zhenyang Peng, Christophe Darnault, Fuqiang Tian, Philippe BaveyeAbstract:Surfactants released into the terrestrial environment in large amounts can potentially alter the physical, chemical and biological properties of Soils, particularly the saturated hydraulic conductivity (Ks). Unfortunately findings regarding this process are quite limited. In this study, column tests were used to analyze the effects of Aerosol 22, a widely used anionic surfactant, on Ks of Loamy sand and Sandy Loam Soils. Solutions were injected into columns from the bottom with controlled pressure heads. Both the overall Ks of columns and the Ks of 6 layers at distances of 0–1 cm, 1–3 cm, 3–5 cm, 5–7 cm, 7–9 cm, and 9–10 cm from the bottom, were continuously monitored before and after the surfactant injections. Results showed that the overall Ks of all columns decreased after 2–4 pore volumes of the surfactant injections. However, stabilization and even increase at the beginning of the surfactant injection was also observed due to the different Ks variations in different layers. Specifically, a surfactant injection of 2–4 pore volumes continuously decreased the Ks of the 0–1 cm layers which yielded a Ks reduction of two orders of magnitude and dominated the Ks variations of the column. In contrast, an increase in the Ks of the 1–3 cm and 3–5 cm layers was more likely, while Ks variation of the 5–10 cm layers was less likely. We hypothetically attributed the Ks variations to the swelling of clay, the collapse of soil aggregates and subsequent particle displacements from surfactant adsorption, which caused pore clogging in the bottom 0–1 cm layer and higher porosities in the layers above. The adsorption of the surfactant aggregates and crystallization were also possibly thought to cause a pore clogging in the bottom layer thus decrease the surfactant concentration from the inlet, the severity of which affects these layers less at greater distances from the inlet. In view of the uncertainty showed by the experimental results, we also suggest to include more replicate columns in future studies, so as to increase the repeatability of the measurements.
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Movement of Cryptosporidium parvum Oocysts through Soils without Preferential Pathways: Exploratory Test
Frontiers in Environmental Science, 2017Co-Authors: Christophe J. G. Darnault, Zhenyang Peng, Astrid R. Jacobson, Philippe C. BaveyeAbstract:Groundwater contamination by oocysts of the waterborne pathogen Cryptosporidium parvum is a significant cause of animal and human disease worldwide. Although research has been undertaken in the past to determine how specific physical and chemical properties of Soils affect the risk of groundwater contamination by C. parvum, there is as yet no clear conclusion concerning the range of mobility of C. parvum that one should expect in field Soils. In this context, the key objective of this research was to determine the magnitude of C. parvum transport in a number of Soils, under conditions in which fast and preferential transport has been successfully prevented. C. parvum oocysts were applied at the surface of different Soils and subjected to artificial rainfall. Apparently for the first time, quantitative PCR was used to detect and enumerate oocysts in the soil columns and in the leachates. The transport of oocysts by infiltrating water, and the considerable retention of oocysts in soil was demonstrated for all Soils, although differences in the degree of transport were observed with Soils of different types. More oocysts were found in leachates from Sandy Loam Soils than in leachates from Loamy sand Soils and the retention of oocysts in different Soils did not significantly differ. The interaction of various processes of the hydrologic system and biogeochemical mechanisms contributed to the transport of oocysts through the soil matrix. Results suggest that the interplay of clay, organic matter, and Ca2+ facilitates and mediates the transfer of organic matter from mineral surfaces to oocysts surface, resulting in the enhanced breakthrough of oocysts through matrices of Sandy Loam Soils compared to those of Loamy sand Soils. Although the number of occysts that penetrate the soil matrix account for only a small percentage of initial inputs, they still pose a significant threat to human health, especially in groundwater systems with a water table not too distant from the soil surface. The results of the research demonstrate a critical need for the simultaneous study of the interaction of various processes affecting oocysts transport in the subsurface, and for its expansion into complex systems, in order to obtain a coherent picture of the behavior of C. parvum oocysts in Soils.
