I am an environmental engineer. My research interests are: ecohydrology, biogeochemistry and fluid mechanics of environmental interfaces. I focus on the effects of hydrology on bacteria and microbial activity in soils and sediments. My current projects are: 1) Impacts of water and oxygen dynamics on trace gas emissions in variably saturated soils; 2) biofilm formation and its effects on water quality; 3) visualization of local maps of oxidative metabolism in soils and biofilms; 4) effects of flow on submerged vegetation and microbes; and 5) microbial activity in the hyporheic zone. My research relies on both experimental and modeling activities. Address: http://simonettarubol.wix.com/ecoservice
Infiltration through sediments is linked to complex biogeochemical processes occurring at small s... more Infiltration through sediments is linked to complex biogeochemical processes occurring at small spatial scales, often leading to a progressive reduction in infiltration rates due to microbial growth and/or mechanical clogging. Unraveling the linkage between microbial dynamics and water infiltration in a heterogeneous medium is of concern in artificial recharge ponds and natural infiltration systems. We present an 84-day laboratory infiltration experiment that aims at studying the temporal variation of selected biogeochemical parameters at different depths along the infiltration path. The experimental setup consists of a 1.2 m high tank packed with a heterogeneous soil and instrumented with arrays of sensors as well as soil and liquid samplers. Results indicate that: (i) microbial processes are responsible for infiltration reduction, enhancing the spatially heterogeneous distribution of infiltration rates with time; (ii) bacteria and extracellular polymeric substances (EPS) are present at all monitored depths, indicating the potential for deep biological clogging; (iii) bacteria functioning and richness exhibit depth zonation after the system reaches a mature state, and (iv) the retention curve changes towards highest saturation by the end of the experiment. The increase in water holding capacity is largest at depth, where the presence of EPS is noticeable. The reduction in time of the quantity of water infiltrating along the tank can only be accounted for with a truly interdisciplinary approach involving physical, chemical and biological processes.
Fine-scale processes in soils affect large-scale phenomena by controlling mixing and reaction rat... more Fine-scale processes in soils affect large-scale phenomena by controlling mixing and reaction rates, yet technological constraints have hampered the collection of micro-scale kinetic data. As a result, limited information is available on the magnitude of fine-scale biogeochemical rates and their temporal and spatial pattern in response to environmental perturbations. In thisworkwe investigate the spatio-temporal dynamics in oxidative microbial activity and the development of anoxic micro zones (i.e., anoxic hot-spots) at the microscopic level (μm - cm). These analyses rely on novel non-invasive & non-destructive optodes, which are able to capture real-time imaging of oxygen concentrations over time at an interval of twenty seconds. Results showed that labile carbon addition resulted in maximum rates of local metabolic activity within a few minutes (5 to 15) and led to the subsequent formation of anoxic hot-spots. Different areas within a given soil sample presented up to one order of magnitude variation in metabolic rate values. As a result, oxic and anoxic micro-zones coexisted closely. The relationship between oxygen concentrations and heterogeneity of oxidative metabolism resulted in an initial increase in metabolic heterogeneity over time followed by a decreasewhen anoxic conditions dominated. A similar link was found by comparing metabolic activity and its heterogeneity across a range of soil types. These results demonstrate that the microbial activity and hot-spot development can be monitored by using a non-invasive quantitative imaging system that allows real-time monitoring of spatial oxygen distribution. We conclude that local dynamics of heterogeneity in space and time at the fine-scale present the same functional behavior encountered in most ecosystems at the landscape-scale.
Canopy layers control momentum and solute transport to and from the overlying water surface layer... more Canopy layers control momentum and solute transport to and from the overlying water surface layer. These transfer mechanisms strongly dependent on canopy geometry, affect the amount of solute in the river, the hydrological retention and availability of dissolved solutes to organisms located in the vegetated layers and are critical to improve water quality. In this work we consider steady-state transport in a vegetated channel under fully-developed flow conditions. Under the hypothesis that the canopy layer can be described as an effective porous medium with prescribed properties, i.e. porosity and permeability, we model solute transport above and within the vegetated layer with an advection-dispersion equation with a spatially variable dispersion coefficient (diffusivity). By means of the Generalized Integral Transform Technique, we derive a semi-analytical solution for the concentration field in submerged vegetated aquatic systems. We show that canopy layer's permeability affects the asymmetry of the concentration profile, the effective vertical spreading behavior, and the magnitude of the peak concentration. Due to its analytical features, the model has a low computational cost. The proposed solution successfully reproduces previously published experimental data.
The accumulation of biofilms in porous media is likely to influence the overall hydraulic propert... more The accumulation of biofilms in porous media is likely to influence the overall hydraulic properties and, consequently, a sound understanding of the process is required for the proper design and management of many technological applications. In order to bring some light into this phenomenon we present a mechanistic model to study the variably saturated hydraulic properties of bio-amended soils. Special emphasis is laid on the distribution of phases at pore-scale and the mechanisms to retain and let water flow through, providing valuable insights into phenomena behind bioclogging. Our approach consists in modeling the porous media as an ensemble of capillary tubes, obtained from the biofilm-free water retention curve. This methodology is extended by the incorporation of a biofilm composed of bacterial cells and extracellular polymeric substances (EPS). Moreover, such a microbial consortium displays a channeled geometry that shrinks/swells with suction. Analytical equations for the volumetric water content and the relative permeability can then be derived by assuming that biomass reshapes the pore space following specific geometrical patterns. The model is discussed by using data from laboratory studies and other approaches already existing in the literature. It can reproduce (i) displacements of the retention curve toward higher saturations and (ii) permeability reductions of distinct orders of magnitude. Our findings also illustrate how even very small amounts of biofilm may lead to significant changes in the hydraulic properties. We, therefore, state the importance of accounting for the hydraulic characteristics of biofilms and for a complex/more realistic geometry of colonies at the pore-scale.
We describe a novel inexpensive method, utilizing particle image velocimetry (PIV) and refractive... more We describe a novel inexpensive method, utilizing particle image velocimetry (PIV) and refractive index-matching (RIM) for visualizing and quantifying the flow field within bio-amended porous media. To date, this technique has been limited to idealized particles, whose refractive index does not match that of fresh water and thus requires specialized and often toxic or hazardous fluids. Here, we use irregularly shaped grains made of hydrogel as the solid matrix and water as the fluid. The advantage of using water is that it provides, for the first time, the opportunity to study both hydraulic and biological processes, which typically occur in soils and streambeds. By using RIM coupled with PIV (RIM-PIV), we measured the interstitial flow field within a cell packed with granular material consisting of hydrogel grains in a size range of 1-8 mm, both in the presence and in the absence of Sinorhizobium meliloti bacteria (strain Rm8530). We also performed experiments with fluorescent tracer (fluorescein) and fluorescent microbes (Shewanella GPF MR-1) to test the capability of visualizing solute transport and microbial movements. Results showed that the RIM-PIV can measure the flow field for both biofilm-free and biofilm-covered hydrogel grains. The fluorescent tracer injection showed the ability to visualize both physical (concave surfaces and eddies) and biological (biofilms) transient storage zones, whereas the fluorescent microbe treatment showed the ability to track microbial movements within fluids. We conclude that the proposed methodology is a promising tool to visualize and quantify biofilm attachment, growth and detachment in a system closer to natural conditions than a 2D flow cell experiment.
Two non-destructive techniques, confocal laser scanning microscopy (CLSM) and planar optode (Visi... more Two non-destructive techniques, confocal laser scanning microscopy (CLSM) and planar optode (VisiSens imaging), were combined to relate the fine-scale spatial structure of biofilm components to real-time images of oxygen decay in aquatic biofilms. Both techniques were applied to biofilms grown for seven days at contrasting light and temperature (10/20°C) conditions. The geo-statistical analyses of CLSM images indicated that biofilm structures consisted of small (~10⁰ μm) and middle sized (~10¹ μm) irregular aggregates. Cyanobacteria and EPS (extracellular polymeric substances) showed larger aggregate sizes in dark grown biofilms while, for algae, aggregates were larger in light-20°C conditions. Light-20°C biofilms were most dense while 10°C biofilms showed a sparser structure and lower respiration rates. There was a positive relationship between the number of pixels occupied and the oxygen decay rate. The combination of optodes and CLMS, taking advantage of geo-statistics, is a promising way to relate biofilm architecture and metabolism at the micrometric scale.
Flow resistance caused by vegetation is a key parameter to properly assess flood management and r... more Flow resistance caused by vegetation is a key parameter to properly assess flood management and river restoration. However, quantifying the friction factor or any of its alternative metrics, e.g. the drag coefficient, in canopies with complex geometry has proven elusive. We explore the effect of canopy morphology on vegetated channels flow structure and resistance by treating the canopy as a porous medium characterized by an effective permeability, a property that describes the ease with which water can flow through the canopy layer. We employ a two-domain model for flow over and within the canopy, which couples the log-law in the free layer to the Darcy-Brinkman equation in the vegetated layer. We validate the model analytical solutions for the average velocity profile within and above the canopy, the volumetric discharge and the friction factor against data collected across a wide range of canopy morphologies encountered in riverine systems. Results indicate agreement between model predictions and data for both simple and complex plant morphologies. For low submergence canopies, we find a universal scaling law that relates friction factor with canopy permeability and a rescaled bulk Reynolds number. This provides a valuable tool to assess habitats sustainability associated with hydro-dynamical conditions.
Understanding the role of the nitrogen cycle in soil systems is of importance in many environment... more Understanding the role of the nitrogen cycle in soil systems is of importance in many environmental applications (for example, minimizing greenhouse emissions). Soils are a dominant source of nitrous oxide N2O releasing an estimated 9.5 Tg N2O -N year-1 (65% of global emissions according to IPCC, 2001a). Further research is still needed to comprehend key drivers of N2O emissions from
ABSTRACT Soil is a complex natural system and exhibits heterogeneity both in space and time. In t... more ABSTRACT Soil is a complex natural system and exhibits heterogeneity both in space and time. In this study, we aim to investigate the effect of this spatially heterogeneous behavior of soil metabolic activity (measured as the rate of sedimentary O2 consumption) on the effective time-averaged rate constant. To meet this objective, we used a novel optical sensor plus imaging technology called VisiSens (PreSens Precision Sensing) that gave us a unique opportunity to obtain percentage air saturation of the sediment in time and space using the images of the surface of the sediment at a set interval (every 20 s for 40 min). Each of these series of images (each consisting of 120 images) were analyzed using an image analysis software (ImajeJ) to extract the spatial data of O2 saturation. For this study, we used fresh sediments collected from Llobregat (Barcelona, Spain) riverbed. The sediments were homogenized and monitored for percentage air upon addition of substrates containing glucose and humic substances. The results show that the rate of O2 consumption is heterogeneous in space and therefore should be considered in the computation of the effective rate of sedimentary O2 consumption for modeling purposes.
ABSTRACT Coupled flows through and over permeable layers occur in a variety of natural phenomena ... more ABSTRACT Coupled flows through and over permeable layers occur in a variety of natural phenomena including turbulent flows over submerged vegetation. In this work we employ a two-domain approach to model flow through and over submerged canopies. The model, amenable of a closed-form solution, couples the log-law and the Darcy-Brinkman equation, and is characterised by a novel representation of the drag force which does not rely on a parametrisation through an unknown drag coefficient. This approach limits to one, i.e., the obstruction permeability, the number of free parameters. Analytical expressions for the average velocity profile through and above the canopies, volumetric flow rate, penetration length and canopy shear layer parameter are obtained in terms of the canopy layer effective permeability. The model suggests that appropriately rescaled velocities in the canopy and surface layers follow two different scaling laws. The analytical predictions match with the experimental data collected by Ghisalberti ana Nepf [2004] and Nepf et at. [2007].
Among the mechanisms that regulate the sources of greenhouse trace gases, such as CO2 and N2O, qu... more Among the mechanisms that regulate the sources of greenhouse trace gases, such as CO2 and N2O, quantifying the CO2 and N2O emissions from soils is particularly challenging because of the spatial and temporal patterns of soil moisture that control their dynamics. This complexity is further complicated by projected increases in frequency, intensity, and duration of rainfall events, floods, and droughts. This will affect the spatial and temporal distribution of soil moisture which will affect the redox zonation and bio-chemical transformations in soils, which in turn determine the production of these trace gases. Additionally, substrate availability and microbial-organic matter interaction contribute to create a highly dynamic environments that impact CO2 and N2O dynamics. Here we present a stochastic modeling framework which couples oxygen and soil water dynamics with the aim of quantifying the importance of biochemical reaction and oxygen consumption on trace gas emission at daily time scale. The model accounts for N2O production from nitrification and denitrification, as well as for the competition for nitrate by denitrification, dissimilatory reduction of nitrate to ammonium, and plant uptake. Different soil types and possible clogging and air-entrapment phenomena are described by varying the rate of gas diffusion through the soil. Preliminary results indicate that the role of soil moisture changes dynamically in time, and is strongly affected by soil diffusivity. As a consequence, our model results show how greenhouse gas production and emission are controlled by both climatic conditions and the internal dynamics of the soil system.
Infiltration through sediments is linked to complex biogeochemical processes occurring at small s... more Infiltration through sediments is linked to complex biogeochemical processes occurring at small spatial scales, often leading to a progressive reduction in infiltration rates due to microbial growth and/or mechanical clogging. Unraveling the linkage between microbial dynamics and water infiltration in a heterogeneous medium is of concern in artificial recharge ponds and natural infiltration systems. We present an 84-day laboratory infiltration experiment that aims at studying the temporal variation of selected biogeochemical parameters at different depths along the infiltration path. The experimental setup consists of a 1.2 m high tank packed with a heterogeneous soil and instrumented with arrays of sensors as well as soil and liquid samplers. Results indicate that: (i) microbial processes are responsible for infiltration reduction, enhancing the spatially heterogeneous distribution of infiltration rates with time; (ii) bacteria and extracellular polymeric substances (EPS) are present at all monitored depths, indicating the potential for deep biological clogging; (iii) bacteria functioning and richness exhibit depth zonation after the system reaches a mature state, and (iv) the retention curve changes towards highest saturation by the end of the experiment. The increase in water holding capacity is largest at depth, where the presence of EPS is noticeable. The reduction in time of the quantity of water infiltrating along the tank can only be accounted for with a truly interdisciplinary approach involving physical, chemical and biological processes.
Fine-scale processes in soils affect large-scale phenomena by controlling mixing and reaction rat... more Fine-scale processes in soils affect large-scale phenomena by controlling mixing and reaction rates, yet technological constraints have hampered the collection of micro-scale kinetic data. As a result, limited information is available on the magnitude of fine-scale biogeochemical rates and their temporal and spatial pattern in response to environmental perturbations. In thisworkwe investigate the spatio-temporal dynamics in oxidative microbial activity and the development of anoxic micro zones (i.e., anoxic hot-spots) at the microscopic level (μm - cm). These analyses rely on novel non-invasive & non-destructive optodes, which are able to capture real-time imaging of oxygen concentrations over time at an interval of twenty seconds. Results showed that labile carbon addition resulted in maximum rates of local metabolic activity within a few minutes (5 to 15) and led to the subsequent formation of anoxic hot-spots. Different areas within a given soil sample presented up to one order of magnitude variation in metabolic rate values. As a result, oxic and anoxic micro-zones coexisted closely. The relationship between oxygen concentrations and heterogeneity of oxidative metabolism resulted in an initial increase in metabolic heterogeneity over time followed by a decreasewhen anoxic conditions dominated. A similar link was found by comparing metabolic activity and its heterogeneity across a range of soil types. These results demonstrate that the microbial activity and hot-spot development can be monitored by using a non-invasive quantitative imaging system that allows real-time monitoring of spatial oxygen distribution. We conclude that local dynamics of heterogeneity in space and time at the fine-scale present the same functional behavior encountered in most ecosystems at the landscape-scale.
Canopy layers control momentum and solute transport to and from the overlying water surface layer... more Canopy layers control momentum and solute transport to and from the overlying water surface layer. These transfer mechanisms strongly dependent on canopy geometry, affect the amount of solute in the river, the hydrological retention and availability of dissolved solutes to organisms located in the vegetated layers and are critical to improve water quality. In this work we consider steady-state transport in a vegetated channel under fully-developed flow conditions. Under the hypothesis that the canopy layer can be described as an effective porous medium with prescribed properties, i.e. porosity and permeability, we model solute transport above and within the vegetated layer with an advection-dispersion equation with a spatially variable dispersion coefficient (diffusivity). By means of the Generalized Integral Transform Technique, we derive a semi-analytical solution for the concentration field in submerged vegetated aquatic systems. We show that canopy layer's permeability affects the asymmetry of the concentration profile, the effective vertical spreading behavior, and the magnitude of the peak concentration. Due to its analytical features, the model has a low computational cost. The proposed solution successfully reproduces previously published experimental data.
The accumulation of biofilms in porous media is likely to influence the overall hydraulic propert... more The accumulation of biofilms in porous media is likely to influence the overall hydraulic properties and, consequently, a sound understanding of the process is required for the proper design and management of many technological applications. In order to bring some light into this phenomenon we present a mechanistic model to study the variably saturated hydraulic properties of bio-amended soils. Special emphasis is laid on the distribution of phases at pore-scale and the mechanisms to retain and let water flow through, providing valuable insights into phenomena behind bioclogging. Our approach consists in modeling the porous media as an ensemble of capillary tubes, obtained from the biofilm-free water retention curve. This methodology is extended by the incorporation of a biofilm composed of bacterial cells and extracellular polymeric substances (EPS). Moreover, such a microbial consortium displays a channeled geometry that shrinks/swells with suction. Analytical equations for the volumetric water content and the relative permeability can then be derived by assuming that biomass reshapes the pore space following specific geometrical patterns. The model is discussed by using data from laboratory studies and other approaches already existing in the literature. It can reproduce (i) displacements of the retention curve toward higher saturations and (ii) permeability reductions of distinct orders of magnitude. Our findings also illustrate how even very small amounts of biofilm may lead to significant changes in the hydraulic properties. We, therefore, state the importance of accounting for the hydraulic characteristics of biofilms and for a complex/more realistic geometry of colonies at the pore-scale.
We describe a novel inexpensive method, utilizing particle image velocimetry (PIV) and refractive... more We describe a novel inexpensive method, utilizing particle image velocimetry (PIV) and refractive index-matching (RIM) for visualizing and quantifying the flow field within bio-amended porous media. To date, this technique has been limited to idealized particles, whose refractive index does not match that of fresh water and thus requires specialized and often toxic or hazardous fluids. Here, we use irregularly shaped grains made of hydrogel as the solid matrix and water as the fluid. The advantage of using water is that it provides, for the first time, the opportunity to study both hydraulic and biological processes, which typically occur in soils and streambeds. By using RIM coupled with PIV (RIM-PIV), we measured the interstitial flow field within a cell packed with granular material consisting of hydrogel grains in a size range of 1-8 mm, both in the presence and in the absence of Sinorhizobium meliloti bacteria (strain Rm8530). We also performed experiments with fluorescent tracer (fluorescein) and fluorescent microbes (Shewanella GPF MR-1) to test the capability of visualizing solute transport and microbial movements. Results showed that the RIM-PIV can measure the flow field for both biofilm-free and biofilm-covered hydrogel grains. The fluorescent tracer injection showed the ability to visualize both physical (concave surfaces and eddies) and biological (biofilms) transient storage zones, whereas the fluorescent microbe treatment showed the ability to track microbial movements within fluids. We conclude that the proposed methodology is a promising tool to visualize and quantify biofilm attachment, growth and detachment in a system closer to natural conditions than a 2D flow cell experiment.
Two non-destructive techniques, confocal laser scanning microscopy (CLSM) and planar optode (Visi... more Two non-destructive techniques, confocal laser scanning microscopy (CLSM) and planar optode (VisiSens imaging), were combined to relate the fine-scale spatial structure of biofilm components to real-time images of oxygen decay in aquatic biofilms. Both techniques were applied to biofilms grown for seven days at contrasting light and temperature (10/20°C) conditions. The geo-statistical analyses of CLSM images indicated that biofilm structures consisted of small (~10⁰ μm) and middle sized (~10¹ μm) irregular aggregates. Cyanobacteria and EPS (extracellular polymeric substances) showed larger aggregate sizes in dark grown biofilms while, for algae, aggregates were larger in light-20°C conditions. Light-20°C biofilms were most dense while 10°C biofilms showed a sparser structure and lower respiration rates. There was a positive relationship between the number of pixels occupied and the oxygen decay rate. The combination of optodes and CLMS, taking advantage of geo-statistics, is a promising way to relate biofilm architecture and metabolism at the micrometric scale.
Flow resistance caused by vegetation is a key parameter to properly assess flood management and r... more Flow resistance caused by vegetation is a key parameter to properly assess flood management and river restoration. However, quantifying the friction factor or any of its alternative metrics, e.g. the drag coefficient, in canopies with complex geometry has proven elusive. We explore the effect of canopy morphology on vegetated channels flow structure and resistance by treating the canopy as a porous medium characterized by an effective permeability, a property that describes the ease with which water can flow through the canopy layer. We employ a two-domain model for flow over and within the canopy, which couples the log-law in the free layer to the Darcy-Brinkman equation in the vegetated layer. We validate the model analytical solutions for the average velocity profile within and above the canopy, the volumetric discharge and the friction factor against data collected across a wide range of canopy morphologies encountered in riverine systems. Results indicate agreement between model predictions and data for both simple and complex plant morphologies. For low submergence canopies, we find a universal scaling law that relates friction factor with canopy permeability and a rescaled bulk Reynolds number. This provides a valuable tool to assess habitats sustainability associated with hydro-dynamical conditions.
Understanding the role of the nitrogen cycle in soil systems is of importance in many environment... more Understanding the role of the nitrogen cycle in soil systems is of importance in many environmental applications (for example, minimizing greenhouse emissions). Soils are a dominant source of nitrous oxide N2O releasing an estimated 9.5 Tg N2O -N year-1 (65% of global emissions according to IPCC, 2001a). Further research is still needed to comprehend key drivers of N2O emissions from
ABSTRACT Soil is a complex natural system and exhibits heterogeneity both in space and time. In t... more ABSTRACT Soil is a complex natural system and exhibits heterogeneity both in space and time. In this study, we aim to investigate the effect of this spatially heterogeneous behavior of soil metabolic activity (measured as the rate of sedimentary O2 consumption) on the effective time-averaged rate constant. To meet this objective, we used a novel optical sensor plus imaging technology called VisiSens (PreSens Precision Sensing) that gave us a unique opportunity to obtain percentage air saturation of the sediment in time and space using the images of the surface of the sediment at a set interval (every 20 s for 40 min). Each of these series of images (each consisting of 120 images) were analyzed using an image analysis software (ImajeJ) to extract the spatial data of O2 saturation. For this study, we used fresh sediments collected from Llobregat (Barcelona, Spain) riverbed. The sediments were homogenized and monitored for percentage air upon addition of substrates containing glucose and humic substances. The results show that the rate of O2 consumption is heterogeneous in space and therefore should be considered in the computation of the effective rate of sedimentary O2 consumption for modeling purposes.
ABSTRACT Coupled flows through and over permeable layers occur in a variety of natural phenomena ... more ABSTRACT Coupled flows through and over permeable layers occur in a variety of natural phenomena including turbulent flows over submerged vegetation. In this work we employ a two-domain approach to model flow through and over submerged canopies. The model, amenable of a closed-form solution, couples the log-law and the Darcy-Brinkman equation, and is characterised by a novel representation of the drag force which does not rely on a parametrisation through an unknown drag coefficient. This approach limits to one, i.e., the obstruction permeability, the number of free parameters. Analytical expressions for the average velocity profile through and above the canopies, volumetric flow rate, penetration length and canopy shear layer parameter are obtained in terms of the canopy layer effective permeability. The model suggests that appropriately rescaled velocities in the canopy and surface layers follow two different scaling laws. The analytical predictions match with the experimental data collected by Ghisalberti ana Nepf [2004] and Nepf et at. [2007].
Among the mechanisms that regulate the sources of greenhouse trace gases, such as CO2 and N2O, qu... more Among the mechanisms that regulate the sources of greenhouse trace gases, such as CO2 and N2O, quantifying the CO2 and N2O emissions from soils is particularly challenging because of the spatial and temporal patterns of soil moisture that control their dynamics. This complexity is further complicated by projected increases in frequency, intensity, and duration of rainfall events, floods, and droughts. This will affect the spatial and temporal distribution of soil moisture which will affect the redox zonation and bio-chemical transformations in soils, which in turn determine the production of these trace gases. Additionally, substrate availability and microbial-organic matter interaction contribute to create a highly dynamic environments that impact CO2 and N2O dynamics. Here we present a stochastic modeling framework which couples oxygen and soil water dynamics with the aim of quantifying the importance of biochemical reaction and oxygen consumption on trace gas emission at daily time scale. The model accounts for N2O production from nitrification and denitrification, as well as for the competition for nitrate by denitrification, dissimilatory reduction of nitrate to ammonium, and plant uptake. Different soil types and possible clogging and air-entrapment phenomena are described by varying the rate of gas diffusion through the soil. Preliminary results indicate that the role of soil moisture changes dynamically in time, and is strongly affected by soil diffusivity. As a consequence, our model results show how greenhouse gas production and emission are controlled by both climatic conditions and the internal dynamics of the soil system.
Uploads
Papers by Simonetta Rubol