Celine Pallud | UC Berkeley (original) (raw)
Papers by Celine Pallud
FTR data (effluent Fe(II), DOC and pH) obtained at 6 and 18C from experiments with subalpine wetl... more FTR data (effluent Fe(II), DOC and pH) obtained at 6 and 18C from experiments with subalpine wetland soils and Fe(II) and DOC export rates from the same experiments
Marine Chemistry, 2007
... To deal with the uncertainties associated with temporal and spatial variations in solute ... ... more ... To deal with the uncertainties associated with temporal and spatial variations in solute ... severely disrupt the physical, chemical and microbial structure of the sediments, thereby introducing ... by removing transport limitations on the supply of reactants to the cells ([Marxsen and ...
Journal of Hydrology, 2012
Journal of Environment Quality, 2013
Reduction of As(V) and Fe(III) is commonly the dominant process controlling the fate and transpor... more Reduction of As(V) and Fe(III) is commonly the dominant process controlling the fate and transport of As in soils and sediments. However, the physical structure of such environments produces complex heterogeneity in biogeochemical processes controlling the fate and transport of As. To resolve the role of soil and sediment physical structure on the distribution of biogeochemical processes controlling the fate and transport of As, we examined the biogeochemical transformations of As and Fe within constructed aggregates-a fundamental unit of soil structure. Spherical aggregates were made with As(V)- or As(III)-bearing, ferrihydrite-coated quartz that was fused with agarose and placed in a cylindrical reactor; advective flow of anoxic solutes was then initiated around the aggregates to examine As release from a dual-pore domain system. To examine the impact of biotic As(V) and Fe(III) reduction, constructed aggregates having As(V)-bearing, ferrihydrite-coated quartz inoculated with sp. ANA-3 were placed in flow-through reactors under anoxic and aerated advective flow. Consistent with desorption from advective columns, As(III) is released to advecting water more prevalently than As(V) within abiotic aggregate systems, indicating a greater lability and concomitant enhanced propensity for transport of As(III) relative to As(V). During reaction with , As release to advecting water was similar between anoxic and aerated systems for the first 20 d; thereafter, the anoxic advecting solutes increased As release relative to the aerated counterpart. With aerated advecting solutes, Fe remained oxidized (or was oxidized) in the aggregate exterior, forming a protective barrier that limited As release to the advective channel. However, anaerobiosis within the aggregate interior, even with aerated advective flow, promotes internal repartitioning of As to the exterior region.
Geochimica et Cosmochimica Acta, 2006
Geochimica et Cosmochimica Acta, 2006
Advances in Space Research, 2010
Vadose Zone Journal, 2012
Combined use of a specific probe and PCAT medium to study Burkholderia in soil
ABSTRACT Most of the agricultural activities in California occur within the Sacramento and San Jo... more ABSTRACT Most of the agricultural activities in California occur within the Sacramento and San Joaquin River Basins, where, as a consequence, water quality as well as quantity have been significantly affected over the last century. Dissolved organic carbon (DOC) concentrations and fluxes from the Sacramento and San Joaquin River Basins have received much attention because riverine DOC flux is an important part of the carbon cycle connecting terrestrial and oceanic ecosystems and because DOC concentration can influence public health as a precursor of carcinogenic disinfectant byproducts (DBPs) such as trihalomethanes and haloacetic acids. Studies on the fate of DOC in watersheds and its relationship with land use are crucial to improve drinking water quality. Considering that water yield from a watershed is one of the main factors governing riverine DOC flux, it is essential to understand factors affecting riverine discharge from watersheds such as precipitation variability, wetland surface area, soil moisture content, and irrigation methods. We investigated the role of precipitation, crop species, and agricultural practices including flood irrigation on watershed water budget and DOC export from subwatersheds of the Sacramento and San Joaquin River Basins using GIS analysis. The preliminary results indicate that agricultural practices effect on DOC fluxes may deserve further attention due to its impacts on watershed water budget, which will be critical for watershed management of DBP precursors.
Structured soils exhibit significant variations in transport characteristics at the aggregate sca... more Structured soils exhibit significant variations in transport characteristics at the aggregate scale. Preferential flow occurs through macropores while predominantly diffusive exchange takes place in intra-aggregate micropores. Such environments characterized by mass transfer limitations are conducive to the formation of small-scale chemical gradients and promote strong spatial variation in processes controlling the fate of redox-sensitive elements such as Fe. In this
Soils and sediments act as open bio-physico-chemical reactors where chemical changes are driven b... more Soils and sediments act as open bio-physico-chemical reactors where chemical changes are driven by the interactions between moving fluids, solid- and aqueous-phase constituents, and microorganisms. They represent complex multiphase environments, with structural and geochemical heterogeneities expressed over spatial scales ranging from the molecular to field scale. In situ rates at which resident microbial populations produce and consume chemical constituents are
Frontiers in Microbiology, 2012
Enhanced anthropogenic inputs of nitrogen (N) and sulfur (S) have disturbed their biogeochemical ... more Enhanced anthropogenic inputs of nitrogen (N) and sulfur (S) have disturbed their biogeochemical cycling in aquatic and terrestrial ecosystems. The N and S cycles interact with one another through competition for labile forms of organic carbon between nitrate-...
Geochimica et Cosmochimica Acta
ABSTRACT Soils display large variations with respect to their physical, geochemical and biologica... more ABSTRACT Soils display large variations with respect to their physical, geochemical and biological characteristics at scales ranging from nanometers to kilometers. The impact of small-scale spatial heterogeneity on ecosystem-scale biogeochemical processes is as of yet poorly understood. The aggregate scale (mm-cm) is of particular interest in structured soils, due to the sharp transition in size between inter-aggregate macropores and intra-aggregate micropores. Micropores limit advective transport thus facilitating the formation of aggregate-scale concentration gradients. Selenium (Se) is an essential micronutrient that has recently emerged as an environmental contaminant. A mechanistic understanding of Se reduction and retention within soil aggregates may lead to improved predictions of Se transport and attenuation in the surface layers of contaminated soils. In order to investigate the coupling between physical and biogeochemical processes controlling Se reduction at the aggregate scale, we used flow-through reactor systems, recreating the transition between advection-dominated macropores and diffusion-dominated micropores. Each system consisted of a spherical artificial aggregate (ID 2.5 cm) contained in a flow-through reactor cell (ID 5.1 cm, L 3.7 cm), with inflow solution providing selenate and an electron donor. Aggregates were constructed using either sand or ferrihydrite-coated sand (to investigate the effect of sorption on selenium reduction and retention) homogenously inoculated with Se-reducing bacteria. Oxic and anoxic experiments were compared. Concentrations of selenite and total Se were measured in the outflow solution and in concentric sections of the aggregates' solid phase. A 2D reactive transport model of reactor-aggregate systems was developed. The majority of selenium reduced inside the aggregates was exported in the form of selenite, unless sorption was significant due to presence ferrihydrite. Selenite export rates were enhanced by the absence of oxygen, and by higher selenate or C-source concentrations in the input solution. The reactive transport model shows that observed differences in selenate solid phase concentrations between aggregates were driven by the interplay between intra-aggregate consumption, supply from the surrounding fluid via diffusively dominated transport, and sorption. We found that solid phase selenite concentrations increased linearly towards the core of aggregates under all conditions investigated. Reactive transport modeling confirmed the role of aggregate geometry and diffusively limited transport in creating the observed pattern: slow transport allows for the build-up and retention of reduced selenium products within the core of aggregates. This suggests that aggregate size may have a predictable, first-order impact on the retention of selenium in soils.
Egs Agu Eug Joint Assembly, Mar 30, 2003
FTR data (effluent Fe(II), DOC and pH) obtained at 6 and 18C from experiments with subalpine wetl... more FTR data (effluent Fe(II), DOC and pH) obtained at 6 and 18C from experiments with subalpine wetland soils and Fe(II) and DOC export rates from the same experiments
Marine Chemistry, 2007
... To deal with the uncertainties associated with temporal and spatial variations in solute ... ... more ... To deal with the uncertainties associated with temporal and spatial variations in solute ... severely disrupt the physical, chemical and microbial structure of the sediments, thereby introducing ... by removing transport limitations on the supply of reactants to the cells ([Marxsen and ...
Journal of Hydrology, 2012
Journal of Environment Quality, 2013
Reduction of As(V) and Fe(III) is commonly the dominant process controlling the fate and transpor... more Reduction of As(V) and Fe(III) is commonly the dominant process controlling the fate and transport of As in soils and sediments. However, the physical structure of such environments produces complex heterogeneity in biogeochemical processes controlling the fate and transport of As. To resolve the role of soil and sediment physical structure on the distribution of biogeochemical processes controlling the fate and transport of As, we examined the biogeochemical transformations of As and Fe within constructed aggregates-a fundamental unit of soil structure. Spherical aggregates were made with As(V)- or As(III)-bearing, ferrihydrite-coated quartz that was fused with agarose and placed in a cylindrical reactor; advective flow of anoxic solutes was then initiated around the aggregates to examine As release from a dual-pore domain system. To examine the impact of biotic As(V) and Fe(III) reduction, constructed aggregates having As(V)-bearing, ferrihydrite-coated quartz inoculated with sp. ANA-3 were placed in flow-through reactors under anoxic and aerated advective flow. Consistent with desorption from advective columns, As(III) is released to advecting water more prevalently than As(V) within abiotic aggregate systems, indicating a greater lability and concomitant enhanced propensity for transport of As(III) relative to As(V). During reaction with , As release to advecting water was similar between anoxic and aerated systems for the first 20 d; thereafter, the anoxic advecting solutes increased As release relative to the aerated counterpart. With aerated advecting solutes, Fe remained oxidized (or was oxidized) in the aggregate exterior, forming a protective barrier that limited As release to the advective channel. However, anaerobiosis within the aggregate interior, even with aerated advective flow, promotes internal repartitioning of As to the exterior region.
Geochimica et Cosmochimica Acta, 2006
Geochimica et Cosmochimica Acta, 2006
Advances in Space Research, 2010
Vadose Zone Journal, 2012
Combined use of a specific probe and PCAT medium to study Burkholderia in soil
ABSTRACT Most of the agricultural activities in California occur within the Sacramento and San Jo... more ABSTRACT Most of the agricultural activities in California occur within the Sacramento and San Joaquin River Basins, where, as a consequence, water quality as well as quantity have been significantly affected over the last century. Dissolved organic carbon (DOC) concentrations and fluxes from the Sacramento and San Joaquin River Basins have received much attention because riverine DOC flux is an important part of the carbon cycle connecting terrestrial and oceanic ecosystems and because DOC concentration can influence public health as a precursor of carcinogenic disinfectant byproducts (DBPs) such as trihalomethanes and haloacetic acids. Studies on the fate of DOC in watersheds and its relationship with land use are crucial to improve drinking water quality. Considering that water yield from a watershed is one of the main factors governing riverine DOC flux, it is essential to understand factors affecting riverine discharge from watersheds such as precipitation variability, wetland surface area, soil moisture content, and irrigation methods. We investigated the role of precipitation, crop species, and agricultural practices including flood irrigation on watershed water budget and DOC export from subwatersheds of the Sacramento and San Joaquin River Basins using GIS analysis. The preliminary results indicate that agricultural practices effect on DOC fluxes may deserve further attention due to its impacts on watershed water budget, which will be critical for watershed management of DBP precursors.
Structured soils exhibit significant variations in transport characteristics at the aggregate sca... more Structured soils exhibit significant variations in transport characteristics at the aggregate scale. Preferential flow occurs through macropores while predominantly diffusive exchange takes place in intra-aggregate micropores. Such environments characterized by mass transfer limitations are conducive to the formation of small-scale chemical gradients and promote strong spatial variation in processes controlling the fate of redox-sensitive elements such as Fe. In this
Soils and sediments act as open bio-physico-chemical reactors where chemical changes are driven b... more Soils and sediments act as open bio-physico-chemical reactors where chemical changes are driven by the interactions between moving fluids, solid- and aqueous-phase constituents, and microorganisms. They represent complex multiphase environments, with structural and geochemical heterogeneities expressed over spatial scales ranging from the molecular to field scale. In situ rates at which resident microbial populations produce and consume chemical constituents are
Frontiers in Microbiology, 2012
Enhanced anthropogenic inputs of nitrogen (N) and sulfur (S) have disturbed their biogeochemical ... more Enhanced anthropogenic inputs of nitrogen (N) and sulfur (S) have disturbed their biogeochemical cycling in aquatic and terrestrial ecosystems. The N and S cycles interact with one another through competition for labile forms of organic carbon between nitrate-...
Geochimica et Cosmochimica Acta
ABSTRACT Soils display large variations with respect to their physical, geochemical and biologica... more ABSTRACT Soils display large variations with respect to their physical, geochemical and biological characteristics at scales ranging from nanometers to kilometers. The impact of small-scale spatial heterogeneity on ecosystem-scale biogeochemical processes is as of yet poorly understood. The aggregate scale (mm-cm) is of particular interest in structured soils, due to the sharp transition in size between inter-aggregate macropores and intra-aggregate micropores. Micropores limit advective transport thus facilitating the formation of aggregate-scale concentration gradients. Selenium (Se) is an essential micronutrient that has recently emerged as an environmental contaminant. A mechanistic understanding of Se reduction and retention within soil aggregates may lead to improved predictions of Se transport and attenuation in the surface layers of contaminated soils. In order to investigate the coupling between physical and biogeochemical processes controlling Se reduction at the aggregate scale, we used flow-through reactor systems, recreating the transition between advection-dominated macropores and diffusion-dominated micropores. Each system consisted of a spherical artificial aggregate (ID 2.5 cm) contained in a flow-through reactor cell (ID 5.1 cm, L 3.7 cm), with inflow solution providing selenate and an electron donor. Aggregates were constructed using either sand or ferrihydrite-coated sand (to investigate the effect of sorption on selenium reduction and retention) homogenously inoculated with Se-reducing bacteria. Oxic and anoxic experiments were compared. Concentrations of selenite and total Se were measured in the outflow solution and in concentric sections of the aggregates' solid phase. A 2D reactive transport model of reactor-aggregate systems was developed. The majority of selenium reduced inside the aggregates was exported in the form of selenite, unless sorption was significant due to presence ferrihydrite. Selenite export rates were enhanced by the absence of oxygen, and by higher selenate or C-source concentrations in the input solution. The reactive transport model shows that observed differences in selenate solid phase concentrations between aggregates were driven by the interplay between intra-aggregate consumption, supply from the surrounding fluid via diffusively dominated transport, and sorption. We found that solid phase selenite concentrations increased linearly towards the core of aggregates under all conditions investigated. Reactive transport modeling confirmed the role of aggregate geometry and diffusively limited transport in creating the observed pattern: slow transport allows for the build-up and retention of reduced selenium products within the core of aggregates. This suggests that aggregate size may have a predictable, first-order impact on the retention of selenium in soils.
Egs Agu Eug Joint Assembly, Mar 30, 2003