70 research outputs found
Examination of the seepage face boundary condition in subsurface and coupled surface/subsurface hydrological models
No full textA seepage face is a nonlinear dynamic boundary that strongly affects pressure head distributions, water table fluctuations, and flow patterns. Its handling in hydrological models, especially under complex conditions such as heterogeneity and coupled surface/subsurface flow, has not been extensively studied. In this paper, we compare the treatment of the seepage face as a static (Dirichlet) versus dynamic boundary condition, we assess its resolution under conditions of layered heterogeneity, we examine its interaction with a catchment outlet boundary, and we investigate the effects of surface/subsurface exchanges on seepage faces forming at the land surface. The analyses are carried out with an integrated catchment hydrological model. Numerical simulations are performed for a synthetic rectangular sloping aquifer and for an experimental hillslope from the Landscape Evolution Observatory. The results show that the static boundary condition is not always an adequate stand-in for a dynamic seepage face boundary condition, especially under conditions of high rainfall, steep slope, or heterogeneity; that hillslopes with layered heterogeneity give rise to multiple seepage faces that can be highly dynamic; that seepage face and outlet boundaries can coexist in an integrated hydrological model and both play an important role; and that seepage faces at the land surface are not always controlled by subsurface flow. The paper also presents a generalized algorithm for resolving seepage face outflow that handles heterogeneity in a simple way, is applicable to unstructured grids, and is shown experimentally to be equivalent to the treatment of atmospheric boundary conditions in subsurface flow models.ECH
Mass-conservative reconstruction of Galerkin velocity fields for transport simulations
No full textAccurate calculation of mass-conservative velocity fields from numerical solutions of Richards’ equation is central to reliable surface–subsurface flow and transport modeling, for example in long-term tracer simulations to determine catchment residence time distributions. In this study we assess the performance of a local Larson-Niklasson (LN) post-processing procedure for reconstructing mass-conservative velocities from a linear (P₁) Galerkin finite element solution of Richards’ equation. This approach, originally proposed for a-posteriori error estimation, modifies the standard finite element velocities by imposing local conservation on element patches. The resulting reconstructed flow field is characterized by continuous fluxes on element edges that can be efficiently used to drive a second order finite volume advective transport model. Through a series of tests of increasing complexity that compare results from the LN scheme to those using velocity fields derived directly from the P₁ Galerkin solution, we show that a locally mass-conservative velocity field is necessary to obtain accurate transport results. We also show that the accuracy of the LN reconstruction procedure is comparable to that of the inherently conservative mixed finite element approach, taken as a reference solution, but that the LN scheme has much lower computational costs. The numerical tests examine steady and unsteady, saturated and variably saturated, and homogeneous and heterogeneous cases along with initial and boundary conditions that include dry soil infiltration, alternating solute and water injection, and seepage face outflow. Typical problems that arise with velocities derived from P₁ Galerkin solutions include outgoing solute flux from no-flow boundaries, solute entrapment in zones of low hydraulic conductivity, and occurrences of anomalous sources and sinks. In addition to inducing significant mass balance errors, such manifestations often lead to oscillations in concentration values that can moreover cause the numerical solution to explode. These problems do not occur when using LN post-processed velocities.</p
Amino acids in the pelagic stromatolites of the Rosso Ammonitico Veronese formation (Middle-Upper Jurassic, Southern Alps, Italy).
No full textDeterminazione litologica e provenienza di ceppi e ancore antiche del Museo Archeologico Regionale di Camarina (Ragusa)
No full textMultiresponse modeling of variably saturated flow and isotope tracer transport for a hillslope experiment at the Landscape Evolution Observatory
No full textThis paper explores the challenges of model parameterization and process
representation when simulating multiple hydrologic responses from a highly
controlled unsaturated flow and transport experiment with a physically based
model. The experiment, conducted at the Landscape Evolution Observatory
(LEO), involved alternate injections of water and deuterium-enriched water
into an initially very dry hillslope. The multivariate observations included
point measures of water content and tracer concentration in the soil, total
storage within the hillslope, and integrated fluxes of water and tracer
through the seepage face. The simulations were performed with a
three-dimensional finite element model that solves the Richards and
advection–dispersion equations. Integrated flow, integrated transport,
distributed flow, and distributed transport responses were successively
analyzed, with parameterization choices at each step supported by standard
model performance metrics. In the first steps of our analysis, where seepage
face flow, water storage, and average concentration at the seepage face were
the target responses, an adequate match between measured and simulated
variables was obtained using a simple parameterization consistent with that
from a prior flow-only experiment at LEO. When passing to the distributed
responses, it was necessary to introduce complexity to additional soil
hydraulic parameters to obtain an adequate match for the point-scale flow
response. This also improved the match against point measures of tracer
concentration, although model performance here was considerably poorer. This
suggests that still greater complexity is needed in the model
parameterization, or that there may be gaps in process representation for
simulating solute transport phenomena in very dry soils.</p
Flow dynamics in hyper-saline aquifers: Hydro-geophysical monitoring and modeling
No full textSaline–freshwater interaction in porous media is a phenomenon of practical interest particularly for the management of water resources in arid and semi-arid environments, where precious freshwater resources are threatened by seawater intrusion and where storage of freshwater in saline aquifers can be a viable option. Saline–freshwater interactions are controlled by physico-chemical processes that need to be accurately modeled. This in turn requires monitoring of these systems, a non-trivial task for which spatially extensive, high-resolution non-invasive techniques can provide key information. In this paper we present the field monitoring and numerical modeling components of an approach aimed at understanding complex saline–freshwater systems. The approach is applied to a freshwater injection experiment carried out in a hyper-saline aquifer near Cagliari (Sardinia, Italy). The experiment was monitored using time-lapse cross-hole electrical resistivity tomography (ERT). To investigate the flow dynamics, coupled numerical flow and transport modeling of the experiment was carried out using an advanced three-dimensional (3-D) density-driven flow-transport simulator. The simulation results were used to produce synthetic ERT inversion results to be compared against real field ERT results. This exercise demonstrates that the evolution of the freshwater bulb is strongly influenced by the system’s (even mild) hydraulic heterogeneities. The example also highlights how the joint use of ERT imaging and gravity-dependent flow and transport modeling give fundamental information for this type of study
Efeito do óleo de nim (Azadirachta indica A. Juss) no intestino médio de Ceraeochrysa claveri (Navás, 1911) (Neuroptera: Chrysopidae): estudo citoquímico, imunocitoquímico e ultraestrutural
No full textCeraeochrysa claveri, popularmente conhecido como bicho lixeiro, é um inseto predador de ovos e larvas de insetos pragas encontrados em diferentes ecossistemas agrícolas. O bicho lixeiro se destaca por apresentar potencial para ser utilizado em programas de Controle Biológico, uma vez que é predador na fase de larva, apresenta curto tempo de desenvolvimento, fácil criação massal e alto potencial reprodutivo na fase adulta. Com o propósito de aprofundar o conhecimento na morfologia e ultraestrutura do intestino médio de C. claveri, o objetivo deste trabalho foi caracterizar histológica e ultraestruturalmente o intestino médio de C. claveri no terceiro ínstar de larva, pupa e adulto. Objetivamos, ainda, avaliar o efeito da ingestão do óleo de nim (Azadirachta indica A. Juss) (Meliaceae) sobre as células epiteliais do intestino médio de larva de terceiro ínstar, pupa e adulto de C. claveri. Ovos de Diatraea saccharalis foram tratados com óleo de nim em três diferentes concentrações (0,5; 1 e 2%) e oferecidos como alimento a larvas de C. claveri durante todo período larval. Após coleta e fixação do intestino médio de larva, pupa e adulto (grupos controle e tratados com óleo de nim), as regiões do mesêntero (anterior, média e posterior) foram processadas para análise histológica (citoquímica e imunocitoquímica) e para análise ultraestrutural. Nossos resultados mostraram que o intestino médio de C. claveri, para as três fases do ciclo de vida, é do tipo pseudoestratificado, composto por células colunares, regenerativas e endócrinas; diferenças morfológicas e ultraestruturais no epitélio permitem caracterizar duas regiões, anterior e posterior, atuando respectivamente na secreção e absorção; região média apresenta características...Ceraeochrysa claveri, popularly known as trash-carriers is a predator insect of eggs and larvae of insect pests found in different agroecosystems. The trash-carriers stands out because it has the potential to be used in biological control programs, once it is a predator in the larval stage; it has short developmental times, easy mass-rearing and high reproductive potential in adult stage. In order to deepen the knowledge on the morphology and ultrastructure of the midgut of C. claveri, the aim of this study was to characterize histological and ultrastructurally the midgut of C. claveri in the third instar larva, pupa and adult. We also evaluate the effect of ingestion of neem oil (Azadirachta indica A. Juss) (Meliaceae) on the midgut epithelial cells of third instar larva, pupa and adult of C. claveri. Diatraea saccharalis eggs were treated with neem oil at three different concentrations (0.5, 1 and 2%) and provided as food to larvae of C. claveri throughout the larval period. After collected and fixed the midgut of larva, pupa and adult (control and treated groups with neem oil), the midgut regions (anterior, middle and posterior) were processed for histological (cytochemistry and immunocytochemistry) and for ultrastructural analysis. Our results showed that the midgut of C. claveri for the three phases of the life cycle is of pseudostratified type, consisting of columnar cells, regenerative cells, and endocrine cells, morphological and ultrastructural differences in the epithelium allowed to characterize two regions, the anterior and posterior, they working mainly in the secretion and absorption respectively; the middle region has intermediate characteristics, and it is considered a transitional area. The ingestion of neem oil in the larval stage of C. claveri showed to be toxic to this predator, causing ultrastructural alterations... (Complete abstract click electronic access below)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP
Efeito do óleo de nim (Azadirachta indica A. Juss) no intestino médio de Ceraeochrysa claveri (Navás, 1911) (Neuroptera: Chrysopidae): estudo citoquímico, imunocitoquímico e ultraestrutural
No full textCeraeochrysa claveri, popularmente conhecido como bicho lixeiro, é um inseto predador de ovos e larvas de insetos pragas encontrados em diferentes ecossistemas agrícolas. O bicho lixeiro se destaca por apresentar potencial para ser utilizado em programas de Controle Biológico, uma vez que é predador na fase de larva, apresenta curto tempo de desenvolvimento, fácil criação massal e alto potencial reprodutivo na fase adulta. Com o propósito de aprofundar o conhecimento na morfologia e ultraestrutura do intestino médio de C. claveri, o objetivo deste trabalho foi caracterizar histológica e ultraestruturalmente o intestino médio de C. claveri no terceiro ínstar de larva, pupa e adulto. Objetivamos, ainda, avaliar o efeito da ingestão do óleo de nim (Azadirachta indica A. Juss) (Meliaceae) sobre as células epiteliais do intestino médio de larva de terceiro ínstar, pupa e adulto de C. claveri. Ovos de Diatraea saccharalis foram tratados com óleo de nim em três diferentes concentrações (0,5; 1 e 2%) e oferecidos como alimento a larvas de C. claveri durante todo período larval. Após coleta e fixação do intestino médio de larva, pupa e adulto (grupos controle e tratados com óleo de nim), as regiões do mesêntero (anterior, média e posterior) foram processadas para análise histológica (citoquímica e imunocitoquímica) e para análise ultraestrutural. Nossos resultados mostraram que o intestino médio de C. claveri, para as três fases do ciclo de vida, é do tipo pseudoestratificado, composto por células colunares, regenerativas e endócrinas; diferenças morfológicas e ultraestruturais no epitélio permitem caracterizar duas regiões, anterior e posterior, atuando respectivamente na secreção e absorção; região média apresenta características...Ceraeochrysa claveri, popularly known as trash-carriers is a predator insect of eggs and larvae of insect pests found in different agroecosystems. The trash-carriers stands out because it has the potential to be used in biological control programs, once it is a predator in the larval stage; it has short developmental times, easy mass-rearing and high reproductive potential in adult stage. In order to deepen the knowledge on the morphology and ultrastructure of the midgut of C. claveri, the aim of this study was to characterize histological and ultrastructurally the midgut of C. claveri in the third instar larva, pupa and adult. We also evaluate the effect of ingestion of neem oil (Azadirachta indica A. Juss) (Meliaceae) on the midgut epithelial cells of third instar larva, pupa and adult of C. claveri. Diatraea saccharalis eggs were treated with neem oil at three different concentrations (0.5, 1 and 2%) and provided as food to larvae of C. claveri throughout the larval period. After collected and fixed the midgut of larva, pupa and adult (control and treated groups with neem oil), the midgut regions (anterior, middle and posterior) were processed for histological (cytochemistry and immunocytochemistry) and for ultrastructural analysis. Our results showed that the midgut of C. claveri for the three phases of the life cycle is of pseudostratified type, consisting of columnar cells, regenerative cells, and endocrine cells, morphological and ultrastructural differences in the epithelium allowed to characterize two regions, the anterior and posterior, they working mainly in the secretion and absorption respectively; the middle region has intermediate characteristics, and it is considered a transitional area. The ingestion of neem oil in the larval stage of C. claveri showed to be toxic to this predator, causing ultrastructural alterations... (Complete abstract click electronic access below)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP
Efeito do óleo de nim (Azadirachta indica A. Juss) no intestino médio de Ceraeochrysa claveri (Navás, 1911) (Neuroptera: Chrysopidae): estudo citoquímico, imunocitoquímico e ultraestrutural
No full textCeraeochrysa claveri, popularmente conhecido como bicho lixeiro, é um inseto predador de ovos e larvas de insetos pragas encontrados em diferentes ecossistemas agrícolas. O bicho lixeiro se destaca por apresentar potencial para ser utilizado em programas de Controle Biológico, uma vez que é predador na fase de larva, apresenta curto tempo de desenvolvimento, fácil criação massal e alto potencial reprodutivo na fase adulta. Com o propósito de aprofundar o conhecimento na morfologia e ultraestrutura do intestino médio de C. claveri, o objetivo deste trabalho foi caracterizar histológica e ultraestruturalmente o intestino médio de C. claveri no terceiro ínstar de larva, pupa e adulto. Objetivamos, ainda, avaliar o efeito da ingestão do óleo de nim (Azadirachta indica A. Juss) (Meliaceae) sobre as células epiteliais do intestino médio de larva de terceiro ínstar, pupa e adulto de C. claveri. Ovos de Diatraea saccharalis foram tratados com óleo de nim em três diferentes concentrações (0,5; 1 e 2%) e oferecidos como alimento a larvas de C. claveri durante todo período larval. Após coleta e fixação do intestino médio de larva, pupa e adulto (grupos controle e tratados com óleo de nim), as regiões do mesêntero (anterior, média e posterior) foram processadas para análise histológica (citoquímica e imunocitoquímica) e para análise ultraestrutural. Nossos resultados mostraram que o intestino médio de C. claveri, para as três fases do ciclo de vida, é do tipo pseudoestratificado, composto por células colunares, regenerativas e endócrinas; diferenças morfológicas e ultraestruturais no epitélio permitem caracterizar duas regiões, anterior e posterior, atuando respectivamente na secreção e absorção; região média apresenta características...Ceraeochrysa claveri, popularly known as trash-carriers is a predator insect of eggs and larvae of insect pests found in different agroecosystems. The trash-carriers stands out because it has the potential to be used in biological control programs, once it is a predator in the larval stage; it has short developmental times, easy mass-rearing and high reproductive potential in adult stage. In order to deepen the knowledge on the morphology and ultrastructure of the midgut of C. claveri, the aim of this study was to characterize histological and ultrastructurally the midgut of C. claveri in the third instar larva, pupa and adult. We also evaluate the effect of ingestion of neem oil (Azadirachta indica A. Juss) (Meliaceae) on the midgut epithelial cells of third instar larva, pupa and adult of C. claveri. Diatraea saccharalis eggs were treated with neem oil at three different concentrations (0.5, 1 and 2%) and provided as food to larvae of C. claveri throughout the larval period. After collected and fixed the midgut of larva, pupa and adult (control and treated groups with neem oil), the midgut regions (anterior, middle and posterior) were processed for histological (cytochemistry and immunocytochemistry) and for ultrastructural analysis. Our results showed that the midgut of C. claveri for the three phases of the life cycle is of pseudostratified type, consisting of columnar cells, regenerative cells, and endocrine cells, morphological and ultrastructural differences in the epithelium allowed to characterize two regions, the anterior and posterior, they working mainly in the secretion and absorption respectively; the middle region has intermediate characteristics, and it is considered a transitional area. The ingestion of neem oil in the larval stage of C. claveri showed to be toxic to this predator, causing ultrastructural alterations... (Complete abstract click electronic access below)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP
Incipient subsurface heterogeneity and its effect on overland flow generation – insight from a modeling study of the first experiment at the Biosphere 2 Landscape Evolution Observatory
No full textEvolution of landscape heterogeneity is controlled by coupled Earth system
dynamics, and the resulting process complexity is a major hurdle to cross
towards a unified theory of catchment hydrology. The Biosphere 2 Landscape
Evolution Observatory (LEO), a 334.5 m2 artificial hillslope built with
homogeneous soil, may have evolved into heterogeneous soil during the first
experiment driven by an intense rainfall event. The experiment produced
predominantly seepage face water outflow, but also generated overland flow,
causing superficial erosion and the formation of a small channel. In this
paper, we explore the hypothesis of incipient heterogeneity development in
LEO and its effect on overland flow generation by comparing the modeling
results from a three-dimensional physically based hydrological model with
measurements of total mass change and seepage face flow. Our null hypothesis
is that the soil is hydraulically homogeneous, while the alternative
hypothesis is that LEO developed downstream heterogeneity from transport of
fine sediments driven by saturated subsurface flow. The heterogeneous case
is modeled by assigning saturated hydraulic conductivity at the LEO seepage
face (Ksat,sf) different from that of the rest (Ksat). A range of
values for Ksat, Ksat,sf, soil porosity, and pore size distribution
is used to account for uncertainties in estimating these parameters,
resulting in more than 20 000 simulations. It is found that the best runs
under the heterogeneous soil hypothesis produce smaller errors than those
under the null hypothesis, and that the heterogeneous runs yield a higher
probability of best model performance than the homogeneous runs. These
results support the alternative hypothesis of localized incipient
heterogeneity of the LEO soil, which facilitated generation of overland
flow. This modeling study of the first LEO experiment suggests an important
role of coupled water and sediment transport processes in the evolution of
subsurface heterogeneity and on overland flow generation, highlighting the
need of a coupled modeling system that integrates across disciplinary processes
- …
