The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Joyce Y Wong - One of the best experts on this subject based on the ideXlab platform.
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adsorption of superparamagnetic iron oxide nanoparticles on silica and calcium Carbonate Sand
Langmuir, 2014Co-Authors: Yoonjee Park, Jeffrey L Paulsen, Ragnhild D Whitaker, Vidhya Mathiyazhagan, Yiqiao Song, Martin D Hurlimann, Igal Szleifer, Joyce Y WongAbstract:Superparamagnetic iron oxide (SPIO) nanoparticles have the potential to be used in the characterization of porous rock formations in oil fields as a contrast agent for NMR logging because they are small enough to traverse through nanopores and enhance contrast by shortening NMR T2 relaxation time. However, successful development and application require detailed knowledge of particle stability and mobility in reservoir rocks. Because nanoparticle adsorption to Sand (SiO2) and rock (often CaCO3) affects their mobility, we investigated the thermodynamic equilibrium adsorption behavior of citric acid-coated SPIO nanoparticles (CA SPIO NPs) and poly(ethylene glycol)-grafted SPIO nanoparticles (PEG SPIO NPs) on SiO2 (silica) and CaCO3 (calcium Carbonate). Adsorption behavior was determined at various pH and salt conditions via chemical analysis and NMR, and the results were compared with molecular theory predictions. Most of the NPs were recovered from silica, whereas far fewer NPs were recovered from calcium c...
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adsorption of superparamagnetic iron oxide nanoparticles on silica and calcium Carbonate Sand
Langmuir, 2014Co-Authors: Yoonjee Park, Jeffrey L Paulsen, Ragnhild D Whitaker, Vidhya Mathiyazhagan, Yiqiao Song, Martin D Hurlimann, Igal Szleifer, Rikkert J Nap, Joyce Y WongAbstract:Superparamagnetic iron oxide (SPIO) nanoparticles have the potential to be used in the characterization of porous rock formations in oil fields as a contrast agent for NMR logging because they are small enough to traverse through nanopores and enhance contrast by shortening NMR T2 relaxation time. However, successful development and application require detailed knowledge of particle stability and mobility in reservoir rocks. Because nanoparticle adsorption to Sand (SiO2) and rock (often CaCO3) affects their mobility, we investigated the thermodynamic equilibrium adsorption behavior of citric acid-coated SPIO nanoparticles (CA SPIO NPs) and poly(ethylene glycol)-grafted SPIO nanoparticles (PEG SPIO NPs) on SiO2 (silica) and CaCO3 (calcium Carbonate). Adsorption behavior was determined at various pH and salt conditions via chemical analysis and NMR, and the results were compared with molecular theory predictions. Most of the NPs were recovered from silica, whereas far fewer NPs were recovered from calcium Carbonate because of differences in the mineral surface properties. NP adsorption increased with increasing salt concentration: this trend was qualitatively explained by molecular theory, as was the role of the PEG grafting in preventing NPs adsorption. Quantitative disagreement between the theoretical predictions and the data was due to NP aggregation, especially at high salt concentration and in the presence of calcium Carbonate. Upon aggregation, NP concentrations as determined by NMR T2 were initially overestimated and subsequently corrected using the relaxation rate 1/T2, which is a function of aggregate size and fractal dimension of the aggregate. Our experimental validation of the theoretical predictions of NP adsorption to minerals in the absence of aggregation at various pH and salt conditions demonstrates that molecular theory can be used to determine interactions between NPs and relevant reservoir surfaces. Importantly, this integrated experimental and theoretical approach can be used to gain insight into NP mobility in the reservoir.
Odette Nehza - One of the best experts on this subject based on the ideXlab platform.
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the origin of erratic calcite speleothems in the dangcheomul cave lava tube cave jeju island korea
Quaternary International, 2008Co-Authors: K. S. Woo, Jeong Chan Kim, Don Won Choi, Jin Kyung Kim, Ryeon Kim, Odette NehzaAbstract:Abstract Dangcheomul Cave in Jeju Island, Korea, is a lava tube about 110 m long. The cave is located only a few meters below the surface under alkali basalt, and contains numerous and various calcite speleothems such as soda straws, stalactites, stalagmites, columns, cave corals, curtains, flowstones, rimstones, Carbonate powders, and shelfstones. Carbonate Sand dunes overlying the lava tube are responsible for the formation of calcite speleothems. The Sand dunes were formed from the Carbonate sediments transported from adjacent shallow seas and beaches, and are composed of mollusks, echinoderms, coralline algae, benthic foraminifers, bryozoans, etc. Oxygen isotopic compositions of some speleothems and cave water indicate that the spelothems have grown mostly by evaporation of cave water. Also, carbon isotopic compositions suggest that the majority of carbon was derived from overlying Carbonates with a minor contribution of organic carbon from the overlying soil. Most speleothems in Dangcheomul Cave do not show typical morphology as can be commonly seen in limestone caves. These erratic forms imply a different mode of speleothem formation. High density of soda straws, stalactites, and columns as well as erratic morphology may also provide the evidence that the plant roots are responsible for their growth.
Yoonjee Park - One of the best experts on this subject based on the ideXlab platform.
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adsorption of superparamagnetic iron oxide nanoparticles on silica and calcium Carbonate Sand
Langmuir, 2014Co-Authors: Yoonjee Park, Jeffrey L Paulsen, Ragnhild D Whitaker, Vidhya Mathiyazhagan, Yiqiao Song, Martin D Hurlimann, Igal Szleifer, Joyce Y WongAbstract:Superparamagnetic iron oxide (SPIO) nanoparticles have the potential to be used in the characterization of porous rock formations in oil fields as a contrast agent for NMR logging because they are small enough to traverse through nanopores and enhance contrast by shortening NMR T2 relaxation time. However, successful development and application require detailed knowledge of particle stability and mobility in reservoir rocks. Because nanoparticle adsorption to Sand (SiO2) and rock (often CaCO3) affects their mobility, we investigated the thermodynamic equilibrium adsorption behavior of citric acid-coated SPIO nanoparticles (CA SPIO NPs) and poly(ethylene glycol)-grafted SPIO nanoparticles (PEG SPIO NPs) on SiO2 (silica) and CaCO3 (calcium Carbonate). Adsorption behavior was determined at various pH and salt conditions via chemical analysis and NMR, and the results were compared with molecular theory predictions. Most of the NPs were recovered from silica, whereas far fewer NPs were recovered from calcium c...
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adsorption of superparamagnetic iron oxide nanoparticles on silica and calcium Carbonate Sand
Langmuir, 2014Co-Authors: Yoonjee Park, Jeffrey L Paulsen, Ragnhild D Whitaker, Vidhya Mathiyazhagan, Yiqiao Song, Martin D Hurlimann, Igal Szleifer, Rikkert J Nap, Joyce Y WongAbstract:Superparamagnetic iron oxide (SPIO) nanoparticles have the potential to be used in the characterization of porous rock formations in oil fields as a contrast agent for NMR logging because they are small enough to traverse through nanopores and enhance contrast by shortening NMR T2 relaxation time. However, successful development and application require detailed knowledge of particle stability and mobility in reservoir rocks. Because nanoparticle adsorption to Sand (SiO2) and rock (often CaCO3) affects their mobility, we investigated the thermodynamic equilibrium adsorption behavior of citric acid-coated SPIO nanoparticles (CA SPIO NPs) and poly(ethylene glycol)-grafted SPIO nanoparticles (PEG SPIO NPs) on SiO2 (silica) and CaCO3 (calcium Carbonate). Adsorption behavior was determined at various pH and salt conditions via chemical analysis and NMR, and the results were compared with molecular theory predictions. Most of the NPs were recovered from silica, whereas far fewer NPs were recovered from calcium Carbonate because of differences in the mineral surface properties. NP adsorption increased with increasing salt concentration: this trend was qualitatively explained by molecular theory, as was the role of the PEG grafting in preventing NPs adsorption. Quantitative disagreement between the theoretical predictions and the data was due to NP aggregation, especially at high salt concentration and in the presence of calcium Carbonate. Upon aggregation, NP concentrations as determined by NMR T2 were initially overestimated and subsequently corrected using the relaxation rate 1/T2, which is a function of aggregate size and fractal dimension of the aggregate. Our experimental validation of the theoretical predictions of NP adsorption to minerals in the absence of aggregation at various pH and salt conditions demonstrates that molecular theory can be used to determine interactions between NPs and relevant reservoir surfaces. Importantly, this integrated experimental and theoretical approach can be used to gain insight into NP mobility in the reservoir.
Douglas R. Tait - One of the best experts on this subject based on the ideXlab platform.
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nutrient and greenhouse gas dynamics through a range of wastewater loaded Carbonate Sand treatments
Ecological Engineering, 2015Co-Authors: Douglas R. Tait, Benjamin O Shepherd, Kevin M Befus, Dirk V ErlerAbstract:Abstract Most countries in the South Pacific rely on traditional soak pits which transfers wastewater down through the unsaturated Carbonate Sand sediment profile with little nutrient attenuation. With surface nutrients having an almost direct path to groundwater, this may have consequences for the sustainability of subsurface water reserves. This study examined the long-term removal and production of wastewater nutrients (including greenhouse gases) in tropical sediments and materials under different saturation regimes. The study showed that unsaturated Carbonate Sands alone are not an effective means of reducing nutrient loads to groundwater. There was no significant difference in removal rates of total dissolved nitrogen (TN) and phosphorus (TP) in unsaturated Carbonate Sand columns and columns amended with coconut husk and basalt sediment. Doubling of the effluent flow rate resulted in no significant decrease in the TN removal rate, but did halve the TP removal rate. The addition of a biochar filter to the unsaturated Carbonate Sand columns increased TN removal from ∼8% to ∼42%. The TN removal rate in the wastewater-saturated treatments (662.1 ± 49.4 mg m −3 day −1 ) was approximately six times higher than the unsaturated treatments (110.2 ± 27.2 mg m −3 day −1 ). TN removal in the fully saturated columns increased from 63% to 95% after the addition of an external carbon source (glucose). Higher nitrous oxide (N 2 O) and methane (CH 4 ) concentrations in partially saturated columns and at the surface of the fully saturated columns were likely due to partial coupled nitrifier denitrification. The addition of basalt sediments to Carbonate Sands increased the total phosphorous removal from 72% to 95%. Sampling of groundwater below an in situ wastewater treatment system showed an almost complete removal of TN and TP within two meters of the aquifer surface, even with limited bioavailable carbon to facilitate denitrification. Modelling of NO 3 − and N 2 concentrations for an idealized treatment system indicated reduced NO 3 − concentrations may be due to a combination of dilution with high volumes of groundwater (∼45% of removal at the farthest sampling point from the system) and denitrification.
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Behaviour of estrogenic endocrine-disrupting chemicals in permeable Carbonate Sands
Environmental Science and Pollution Research, 2015Co-Authors: Benjamin O Shepherd, Douglas R. Tait, Dirk V Erler, Lukas Zwieten, Stephen Kimber, Bradley D EyreAbstract:The remediation of four estrogenic endocrine-disrupting compounds (EDCs), estrone (E1), estradiol (E2), ethinylestradiol (EE2) and estriol (E3), was measured in saturated and unsaturated Carbonate Sand-filled columns dosed with wastewater from a sewage treatment plant. The estrogen equivalency (EEQ) of inlet wastewater was 1.2 ng L^−1 and was remediated to an EEQ of 0.5 ng L^−1 through the unsaturated Carbonate Sand-filled columns. The high surface area of Carbonate Sand and associated high microbial activity may have assisted the degradation of these estrogens. The fully saturated Sand columns showed an increase in total estrogenic potency with an EEQ of 2.4 ng L^−1, which was double that of the inlet wastewater. There was a significant difference ( P
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Nutrient transport, modification and fate in a Carbonate Sand coral reef lagoon
2015Co-Authors: Douglas R. TaitAbstract:Although nutrients are a fundamental component of living organisms, excessive concentrations of nutrients in marine ecosystems can result in a range of negative consequences. Carbonate Sand-dominated islands, like those found throughout the South Pacific, may be particularly susceptible to the nutrient over-enrichment of their surrounding waters due to the high porosity of Carbonate Sands and the perceived lack of biological activity in the sediments. To contribute to closing the knowledge gap of nutrient dynamics in Carbonate Sand systems, this thesis examines the movement, biogeochemistry and mitigation of nutrients in a coral Sand lagoon system. In order to then determine the flow of nutrient into the surrounding lagoon, the flux of submarine groundwater discharge (SGD) was determined using three different but commonly used radon mass-balance models. There was an approximately eight-fold difference in the SGD flux rates calculated by the models. The study highlighted, through the use of time series, survey and electric resistivity techniques, that the applicability of each model is based on the hydrological and geological features of the study area. To determine the contribution of groundwater derived nutrient to the surrounding lagoon, a nutrient mass balance was then constructed. The mass balance accounted for 92% of dissolved nitrogen (N) leaving the lagoon, and for approximately 36% of dissolved phosphorus (P) inputs. SGD accounted for 81% of dissolved inorganic N (DIN) inputs and 47% of DIN exported form the lagoon. Analysis of tritium concentrations showed that old, deep groundwater (10 – 93 years old) was the main source of SGD derived nutrients to the lagoon indicating there may be a large time lag between nutrient infiltration on land and discharge into the receiving waters. A series of long term column experiments showed that the TN removal rate in the wastewater-saturated treatments was approximately six times higher than the unsaturated treatments. The addition of a carbon source and biochar facilitated a drop in both nutrient ii and greenhouse gas concentrations. Sampling of groundwater below an in situ wastewater treatment system showed an almost complete removal of TN and TP within two meters of the aquifer surface, even with limited bioavailable carbon to facilitate denitrification.Modelling of NO3 - and N2 concentrations for an idealized treatment system indicated reduced NO3 - concentrations may be due to a combination of dilution with high volumes of groundwater and denitrification. Lastly, in order to mitigate groundwater nutrient flow into the lagoon, a low cost, low technology wastewater treatment system adapted to the constraints of South Pacific islands was developed and monitored. The system removed 63% of total P and 43% of total N over 17 months of monitoring. The system showed complete attenuation of NH4 + as wastewater moved through the system, and simultaneous nitrification/denitrification in both aerobic and anaerobic zones. Overall, the study endeavoured to not only make a…
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Nutrient processing in a novel on-site wastewater treatment system designed for permeable Carbonate Sand environments
Ecological Engineering, 2013Co-Authors: Douglas R. Tait, Dirk V Erler, Andrew Dakers, Leigh Davison, Bradley D EyreAbstract:Abstract This study was the first to develop, install and examine a secondary treatment system for domestic wastewater specific to permeable Carbonate Sand systems. The ‘ecoTrench’ (eT), relied on effluent passing through a number of different treatment layers including a coconut husk humus ecology, a saturated trench and unsaturated Carbonate Sands. An eT was installed on a residential property on the main island of Rarotonga in the Cook Islands and received primary treated effluent from a septic tank over a 21 month period from May 2009 until February 2011. Nutrient removal efficiencies for the eT averaged 63% of total phosphorous and 43% of total nitrogen. The eT was an effective nitrifyer of NH4+ to NO3− with almost complete attenuation of NH4+ as effluent passed through the system. Uptake rates of NH4+ averaged 36.7 ± 4.1 mmol m−3 h−1 as wastewaters left the saturated trench. The addition of labelled stable isotope (15NH4+), showed that simultaneous nitrification/denitrification was occurring in both aerobic and anaerobic treatment layers. Elevated concentrations of dissolved organic nitrogen (DON) were seen as effluent left the saturated treatment layer before largely being attenuated as effluent moved down through the sediment profile. This may have contributed to a significant build-up of NO3− as effluent moved towards groundwater largely due to inhibited denitrification and the mobilization and remineralisation of previously assimilated DON. The eT represents an efficient and effective way to reduce nutrient loading to groundwater and can work well within the constraints of many island communities based in permeable Carbonate Sand systems.
Ragnhild D Whitaker - One of the best experts on this subject based on the ideXlab platform.
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adsorption of superparamagnetic iron oxide nanoparticles on silica and calcium Carbonate Sand
Langmuir, 2014Co-Authors: Yoonjee Park, Jeffrey L Paulsen, Ragnhild D Whitaker, Vidhya Mathiyazhagan, Yiqiao Song, Martin D Hurlimann, Igal Szleifer, Joyce Y WongAbstract:Superparamagnetic iron oxide (SPIO) nanoparticles have the potential to be used in the characterization of porous rock formations in oil fields as a contrast agent for NMR logging because they are small enough to traverse through nanopores and enhance contrast by shortening NMR T2 relaxation time. However, successful development and application require detailed knowledge of particle stability and mobility in reservoir rocks. Because nanoparticle adsorption to Sand (SiO2) and rock (often CaCO3) affects their mobility, we investigated the thermodynamic equilibrium adsorption behavior of citric acid-coated SPIO nanoparticles (CA SPIO NPs) and poly(ethylene glycol)-grafted SPIO nanoparticles (PEG SPIO NPs) on SiO2 (silica) and CaCO3 (calcium Carbonate). Adsorption behavior was determined at various pH and salt conditions via chemical analysis and NMR, and the results were compared with molecular theory predictions. Most of the NPs were recovered from silica, whereas far fewer NPs were recovered from calcium c...
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adsorption of superparamagnetic iron oxide nanoparticles on silica and calcium Carbonate Sand
Langmuir, 2014Co-Authors: Yoonjee Park, Jeffrey L Paulsen, Ragnhild D Whitaker, Vidhya Mathiyazhagan, Yiqiao Song, Martin D Hurlimann, Igal Szleifer, Rikkert J Nap, Joyce Y WongAbstract:Superparamagnetic iron oxide (SPIO) nanoparticles have the potential to be used in the characterization of porous rock formations in oil fields as a contrast agent for NMR logging because they are small enough to traverse through nanopores and enhance contrast by shortening NMR T2 relaxation time. However, successful development and application require detailed knowledge of particle stability and mobility in reservoir rocks. Because nanoparticle adsorption to Sand (SiO2) and rock (often CaCO3) affects their mobility, we investigated the thermodynamic equilibrium adsorption behavior of citric acid-coated SPIO nanoparticles (CA SPIO NPs) and poly(ethylene glycol)-grafted SPIO nanoparticles (PEG SPIO NPs) on SiO2 (silica) and CaCO3 (calcium Carbonate). Adsorption behavior was determined at various pH and salt conditions via chemical analysis and NMR, and the results were compared with molecular theory predictions. Most of the NPs were recovered from silica, whereas far fewer NPs were recovered from calcium Carbonate because of differences in the mineral surface properties. NP adsorption increased with increasing salt concentration: this trend was qualitatively explained by molecular theory, as was the role of the PEG grafting in preventing NPs adsorption. Quantitative disagreement between the theoretical predictions and the data was due to NP aggregation, especially at high salt concentration and in the presence of calcium Carbonate. Upon aggregation, NP concentrations as determined by NMR T2 were initially overestimated and subsequently corrected using the relaxation rate 1/T2, which is a function of aggregate size and fractal dimension of the aggregate. Our experimental validation of the theoretical predictions of NP adsorption to minerals in the absence of aggregation at various pH and salt conditions demonstrates that molecular theory can be used to determine interactions between NPs and relevant reservoir surfaces. Importantly, this integrated experimental and theoretical approach can be used to gain insight into NP mobility in the reservoir.