bluuebunny/crossref_metadata_2025 huggingface dataset:
Exploring Scenarios to Dramatically Reduce Smoking Prevalence: A Simulation Model of the Three-Part Cessation Process
Authors: Levy David T. , Mabry Patricia L. , Graham Amanda L. , Orleans C. Tracy , Abrams David B.
Published: May 2010

Objectives. We used a simulation model to analyze whether the Healthy People 2010 goal of reducing smoking prevalence from the current 19.8% rate to 12% by 2010 could be accomplished by increasing quit attempts, increasing the use of treatments, or increasing the effectiveness of treatment.

Methods. We expanded on previous versions of the tobacco control simulation model SimSmoke to assess the effects of an increase in quit attempts, treatment use, and treatment effectiveness to reduce smoking prevalence. In the model, we considered increases in each of these parameters individually and in combination.

Results. Individually, 100% increases in quit attempts, treatment use, and treatment effectiveness reduced the projected 2020 prevalence to 13.9%, 16.7%, and 15.9%, respectively. With a combined 100% increase in all components, the goal of a 12% adult smoking prevalence could be reached by 2012.

Conclusions. If we are to come close to reaching Healthy People 2010 goals in the foreseeable future, we must not only induce quit attempts but also increase treatment use and effectiveness. Simulation models provide a useful tool for evaluating the potential to reach public health targets.
A Network Assessment of Community-Based Participatory Research: Linking Communities and Universities to Reduce Cancer Disparities
Authors: Valente Thomas W. , Fujimoto Kayo , Palmer Paula , Tanjasiri Sora Park
Published: May 2010

Objectives. We sought to determine whether a community-based initiative designed to reduce cancer disparities among Pacific Islanders in Southern California increased communications between community-based organizations and university researchers.

Methods. We conducted network analysis among 11 community-based organizations (CBOs) and 5 universities by interviewing 91 and 56 members of these organizations, respectively, at 2 points in time. We estimated random effects probit regression and stochastic actor-oriented network dynamic models.

Results. We found that, during the 2-year study period, CBOs increased their connectedness with one another (b= 0.44; P < .05) and to the universities (b = 0.46; P < .05), but that university researchers did not increase their connectedness to each other or to CBOs.

Conclusions. Cancer awareness, cancer education, and access to cancer services are low among Pacific Island groups, and this study provides an initial attempt to reduce these disparities. Community-based initiatives can strengthen a CBO network, creating the potential for increased community-informed cancer research and improved community access to cancer research resources.
Application of a System Dynamics Model to Inform Investment in Smoking Cessation Services in New Zealand
Authors: Tobias Martin I. , Cavana Robert Y. , Bloomfield Ashley
Published: May 2010

Objectives. We estimated the long-term effects of smoking cessation interventions to inform government decision-making regarding investment in tobacco control.

Methods. We extracted data from the 2006 New Zealand Tobacco Use Survey and other sources and developed a system dynamics model with the iThink computer simulation package. The model derived estimates of population cessation rates from smoking behaviors and applied these over a 50-year period, from 2001 to 2051, under business-as-usual and enhanced cessation intervention scenarios.

Results. The model predicted larger effects by 2051 with the enhanced cessation than with the business-as-usual scenario, including: an 11% greater decline in adult current smoking prevalence (9 versus 10 per 100 people), 16% greater decline in per capita tobacco consumption (370 versus 440 cigarette equivalents per year), and 11% greater reduction in tobacco-attributable mortality (3000 versus 3300 deaths per year).

Conclusions. The model generated reliable estimates of the effects on health and on tobacco use of interventions designed to enhance smoking cessation. These results informed a decision announced in May 2007 to increase funding for smoking cessation by NZ $42 million over 4 years.
An Impact Evaluation of a Federal Mine Safety Training Regulation on Injury Rates Among US Stone, Sand, and Gravel Mine Workers: An Interrupted Time-Series Analysis
Authors: Monforton Celeste , Windsor Richard
Published: May 2010

Objectives. We evaluated the impact of a safety training regulation, implemented by the US Department of Labor's Mine Safety and Health Administration (MSHA) in 1999, on injury rates at stone, sand, and gravel mining operations.

Methods. We applied a time-series design and analyses with quarterly counts of nonfatal injuries and employment hours from 7998 surface aggregate mines from 1995 through 2006. Covariates included standard industrial classification codes, ownership, and injury severity.

Results. Overall crude rates of injuries declined over the 12-year period. Reductions in incident rates for medical treatment only, restricted duty, and lost-time injuries were consistent with temporal trends and provided no evidence of an intervention effect attributable to the MSHA regulation. Rates of permanently disabling injuries (PDIs) declined markedly. Regression analyses documented a statistically significant reduction in the risk rate in the postintervention time period (risk rate = 0.591; 95% confidence interval = 0.529, 0.661).

Conclusions. Although a causal relationship between the regulatory intervention and the decline in the rate of PDIs is plausible, inconsistency in the results with the other injury-severity categories preclude attributing the observed outcome to the MSHA regulation. Further analyses of these data are needed.
Epidemiology and Burden of Hepatitis A, Malaria, and Typhoid in New York City Associated With Travel: Implications for Public Health Policy
Authors: Adamson Rosemary , Reddy Vasudha , Jones Lucretia , Antwi Mike , Bregman Brooke , Weiss Don , Phillips Michael , Horowitz Harold W.
Published: May 2010

We examined New York City Department of Health and Mental Hygiene surveillance data on hepatitis A, malaria, and typhoid to determine the proportion of these diseases related to travel and their geographic distribution. We found that 61% of hepatitis A cases, 100% of malaria cases, and 78% of typhoid cases were travel related and that cases clustered in specific populations and neighborhoods at which public health interventions could be targeted. High-risk groups include Hispanics (for hepatitis A), West Africans living in the Bronx (for malaria), and South Asians (for typhoid).
“Our Reach Is Wide by Any Corporate Standard”: How the Tobacco Industry Helped Defeat the Clinton Health Plan and Why It Matters Now
Authors: Tesler Laura E. , Malone Ruth E.
Published: May 2010

Contemporary health care reformers, like those who promoted the failed Clinton era plan, face opposition from multiple corporate interests. However, scant literature has examined how relationships between corporations and other stakeholders, such as think tanks and advocacy groups, shape health care reform debate.

We show how the 2 biggest US tobacco companies, Philip Morris and RJ Reynolds, and their trade association coordinated in mobilizing ideologically diverse constituencies to help defeat the Clinton plan. Unwittingly perhaps, some reform supporters advanced the tobacco industry's public relations blitz, contributing to perceptions of public opposition to the plan.

As the current reform debate unfolds, this case highlights the importance of funding transparency for interpreting the activities of think tanks, advocacy groups, and “grassroots” movements.
Syringe Disposal Among Injection Drug Users in San Francisco
Authors: Wenger Lynn D. , Martinez Alexis N. , Carpenter Lisa , Geckeler Dara , Colfax Grant , Kral Alex H.
Published: May 2010

To assess the prevalence of improperly discarded syringes and to examine syringe disposal practices of injection drug users (IDUs) in San Francisco, we visually inspected 1000 random city blocks and conducted a survey of 602 IDUs. We found 20 syringes on the streets we inspected. IDUs reported disposing of 13% of syringes improperly. In multivariate analysis, obtaining syringes from syringe exchange programs was found to be protective against improper disposal, and injecting in public places was predictive of improper disposal. Few syringes posed a public health threat.
“Willful Misconduct”: How the US Government Prevented Tobacco-Disabled Veterans From Obtaining Disability Pensions
Authors: Offen Naphtali , Smith Elizabeth A. , Malone Ruth E.
Published: May 2010

In this descriptive case study, we analyze the unsuccessful struggle to access disability pensions by veterans sickened by tobacco use begun during service. Drawing on tobacco industry documents and other material, we show how the US government, tobacco industry, and veterans' organizations each took inconsistent positions to protect their interests.

Congress and Department of Veterans Affairs leadership, concerned about costs, characterized veterans' smoking as “willful misconduct,” thereby contradicting the government's position in a federal lawsuit that tobacco companies addicted smokers. Veterans' groups supported the pensions, despite previously defending smoking as a “right.” The tobacco industry wavered, fearing liability. Securing pensions was complicated by the notion that smoking is primarily a personal choice.

The US government should compensate veterans fairly and should abolish military practices that encourage tobacco addiction.
An Actor-Network Theory Analysis of Policy Innovation for Smoke-Free Places: Understanding Change in Complex Systems
Authors: Young David , Borland Ron , Coghill Ken
Published: May 2010

Complex, transnational issues like the tobacco epidemic are major challenges that defy analysis and management by conventional methods, as are other public health issues, such as those associated with global food distribution and climate change. We examined the evolution of indoor smoke-free regulations, a tobacco control policy innovation, and identified the key attributes of those jurisdictions that successfully pursued this innovation and those that to date have not. In doing so, we employed the actor-network theory, a comprehensive framework for the analysis of fundamental system change. Through our analysis, we identified approaches to help overcome some systemic barriers to the solution of the tobacco problem and comment on other complex transnational problems.
Engineered Surface Barrier Monitoring Using Ground‐Penetrating Radar, Time‐Domain Reflectometry, and Neutron‐Scattering Techniques
Authors: Strickland Christopher E. , Ward Andy L. , Clement William P. , Draper Kathryn E.
Published: May 2010

Effective monitoring of surface barriers intended to isolate and protect waste from the accessible environment requires techniques to assess their performance. Quantifying drainage conditions at any point below the barrier is difficult because field‐scale drainage measurements are not well suited for assessing spatial drainage heterogeneity. Measurements of water storage, however, can provide an indirect measure of impending drainage. We measured seasonal water content at a vegetated capillary barrier on the Hanford Site in southeastern Washington to determine effective water‐storage monitoring methods. Measurements were made using ground‐penetrating radar (GPR) direct ground wave methods operating at 100 MHz. Simultaneous measurements using time‐domain reflectometry (TDR) and neutron‐scattering probe (NP) were used to determine the sampling depth of the GPR ground wave. The ground wave sampling depth increased only slightly with decreasing moisture content, ranging from 30 to 37.5 cm. The TDR measurements were made using permanently emplaced arrays, eliminating the need for repeated ground disturbance. All three methods showed similar seasonal responses, with the highest water contents observed during the winter months and decreasing through the summer. Unlike TDR and NPs, which are local‐scale measurements, GPR exhibited much greater spatial detail across the barrier surface. While measurement uncertainties exist with regard to the sampling depth and dispersive effects, our results indicate that GPR can be an effective and minimally invasive method for providing reasonable near‐surface estimates of soil water content changes within an engineered barrier.
Comparison of Single‐ and Double‐Ring Infiltrometer Methods on Stony Soils
Authors: Verbist K. , Torfs S. , Cornelis W.M. , Oyarzún R. , Soto G. , Gabriels D.
Published: May 2010

Infiltration measurements to determine the field saturated hydraulic conductivity (Kfs) in arid lands are often plagued by large variations that can be attributed to soil heterogeneity, the measurement method, the number of replications, and the Kfs calculation method used. This study addressed the question of how comparable are two different measurement methods, the single‐ring infiltrometer (SR) and double‐ring infiltrometer (DR), when applied at three locations in a semiarid part of Chile that show moderate (15%) to high (55%) stoniness. Additionally, Kfs variations due to different calculation methods for the same measurement method were thoroughly investigated, considering nine methods for the SR and 10 methods for the DR. Results showed that different calculation techniques gave sometimes significantly different estimates of Kfs when using the same data set, and those relative differences were conserved between measurement locations. When comparing the same calculation technique for both SR and DR, both methods gave equivalent Kfs estimates for each location. The SR infiltration measurements were modeled better using a transient approach, while infiltration models considering steady state performed better with the DR.
A Dynamic Network‐Type Simulator to Investigate the Multiphase Flow Properties of Heterogeneous Soils
Authors: Tsakiroglou C.D. , Sygouni V. , Aggelopoulos C.A.
Published: May 2010

A dynamic and large‐scale network simulator was developed to simulate the rate‐controlled immiscible displacement of two fluids in long, undisturbed soil columns. The simulator is a fast method for upscaling the hydraulic properties of heterogeneous soils and is an alternative to the conventional method where a system of partial differential equations is solved in a numerical grid. The pore space is regarded as a cubic network. Each node represents a pore network, the permeability of which is chosen randomly from a density distribution function. The macroheterogeneity of the large‐scale network is quantified by the width of the node permeability distribution. The capillary pressure and relative permeability functions are obtained from either the quasistatic simulation of the displacement of water by oil in a pore‐and‐throat network or the inverse modeling of soil column flow tests by using the approximate multiflowpath model (MFPM). At each time step, the fluid saturation and pressure of each node are calculated, formulating mass balances at each node, accounting for capillary, viscous and gravity forces, solving the system of coupled and linear equations, calculating the instantaneous flow rates, and updating the local fluid saturations. The inlet pressure is adjusted to keep the total flow rate of injected fluid constant. Sensitivity analysis revealed that the transient responses of the axial distribution of fluid saturation, total pressure drop across the network, and sample averaged (upscaled) relative permeability functions depend on the variability of permeability distribution, spatial correlations of permeability field, capillary number, and viscosity ratio. When the microheterogeneity at the pore network scale of nodes strengthens, the flow of oil through preferential pathways is enhanced, and the upscaled water and oil relative permeabilities change drastically.
Using Oxygen‐18 to Study the Role of Preferential Flow in the Formation of Hillslope Runoff
Authors: Vogel Tomas , Sanda Martin , Dusek Jaromir , Dohnal Michal , Votrubova Jana
Published: May 2010

Soil water dynamics at an experimental hillslope site is studied by means of a one‐dimensional dual‐continuum model. The model is based on Richards' equation for vertical soil water flow and the advection–dispersion equation for transport of the stable isotope 18O. The water body contained in the soil‐matrix pore space and the one transmitted through the system of preferential pathways are treated as two separate, mutually communicating soil water continua. The 18O isotope, monitored in precipitation, subsurface hillslope discharge, and soil water, was used as a natural tracer to study the role of preferential flow in the formation of shallow subsurface runoff. It is shown that the dual‐continuum approach can, in principle, explain the observed variations of 18O content in the subsurface hillslope discharge. The model successfully describes mixing of new water, which reflects the isotope signatures of the individual precipitation events, with old water, reflecting the seasonal variability of the isotope signal.
Estimation of the Dual‐Permeability Model Parameters using Tension Disk Infiltrometer and Guelph Permeameter
Authors: Kodešová Radka , Šimůnek Jiří , Nikodem Antonín , Jirků Veronika
Published: May 2010

A determination of the parameters describing the soil hydraulic properties of matrix and macropore domains and mass exchange between these domains is crucial when preferential water flow in structured soils is simulated using the dual‐permeability model. This study focused on estimating the parameters of the radially symmetric dual‐permeability model from cumulative infiltration measured in the surface horizon of a Haplic Luvisol. While parameters obtained from the numerical inversion of the tension disk infiltration, using the single‐porosity flow model in HYDRUS 2D/3D, were used to describe the matrix domain, the parameters characterizing the macropore domain and mass exchange between domains were estimated using the Guelph permeameter infiltration and the dual‐permeability flow model in HYDRUS 2D/3D. The mass transfer coefficient between the two pore domains affected the simulated water regime considerably, and subsequently, the calibrated value of the saturated hydraulic conductivity in the macropore domain, Ksf A less significant impact of the aggregate shape factor was observed due to a low range of possible values compared with the other two parameters, which either varied within orders of magnitude (the effective saturated hydraulic conductivity of the interface between the two pore domains, Ksa) or were squared (the characteristic length of an aggregate, a). The Ksf values increased when mass exchange decreased (when a increased and Ksa decreased). Since both parameters are mutually correlated and therefore have a similar impact on simulated data, we suggest that a be determined independently, and Ksa and Ksf should be simultaneously optimized when the parameters of the dual‐permeability model are evaluated using the presented experimental procedure.
Advective and Diffusive Gas Transport through Fractured Sulfur Blocks
Authors: Birkham T.K. , Hendry M.J. , Barbour S.L.
Published: May 2010

Long‐term storage of S0 blocks poses a contamination risk to both groundwater and surface water as the oxidation of S0 to H2SO4 creates drainage waters with low pH and elevated SO42− concentrations. Because the presence of O2 in the S0 blocks is a primary control on S0 oxidation, rates of atmospheric gas migration into the blocks can be used to quantify S0 oxidation rates. Using in situ measurements and a tracer experiment combined with laboratory diffusion experiments, we determined that transport analysis of multiple gas species is required to quantify O2 fluxes into a S0 block. Advection, created by O2 consumption within the block, accounted for 21% of the total O2 influx and considerably increased H2SO4 production in the block above that attributed to O2 diffusion. While barometric pumping of the fracture porosity in the upper 8 m was probably occurring, its overall effect on O2 influx was determined to be negligible. Quantification of O2 and CO2 fluxes was necessary to explain the direction and magnitude of N2 concentration gradients that develop in the block, despite the fact that N2 was nonreactive. Our findings should be widely applicable because the construction method of S0 blocks is standard throughout the world.
Investigating Preferential Flow Processes in a Forest Soil Using Time Domain Reflectometry and Electrical Resistivity Tomography
Authors: Oberdörster C. , Vanderborght J. , Kemna A. , Vereecken H.
Published: May 2010

We compared the well‐established time domain reflectometry (TDR) method and electrical resistivity tomography (ERT) to monitor bulk electrical conductivity, σb, during a saline tracer experiment. The experiment was conducted at a forest site on the premises of the Forschungszentrum Jülich. To parameterize solute transport processes, the convection–dispersion equation (CDE) and the mobile–immobile (MIM) model were fitted to the data. Although σb derived from ERT was lower than TDR measurements at almost all depths, the estimated pore water velocities of the CDE model were very similar. Early peak arrival times at lower depths and long tailings of the breakthrough curves clearly indicated preferential flow phenomena that could not be described with an appropriate parameterization using classical transport approaches such as the CDE. Adoption of the MIM model did not lead to more reasonable solute transport parameters. Additionally, preferential flow was reflected in high peak velocities in the lower depths, which exceeded piston flow velocities. The strong decline in peak σb with depth showed that the volume through which transport took place decreased with depth. Typical features of preferential transport could be detected and the spatial variability of the preferential transport process could be imaged by ERT.
Applicability of Ethanol for Measuring Intrinsic Hydraulic Properties of Sand with Various Water Repellency Levels
Authors: Lamparter A. , Bachmann J. , Deurer M. , Woche S.K.
Published: May 2010

Many soils worldwide show water repellency to some degree. Soil water repellency (SWR) is known to alter hydraulic processes. Particularly in water‐repellent soils a decreased water infiltration rate can be observed. In this case soil hydraulic properties, like the hydraulic conductivity, not only are a result of the soil's pore system but also depend on the physicochemical properties of the pore surfaces (water repellency). Ethanol as a completely wetting liquid is not influenced by the soil's water repellency. In this study we introduce the concept of intrinsic soil hydraulic properties, that is, the hydraulic properties that are only dependent on the porous system and independent of its surface properties. We used the concept of intrinsic permeability, originally developed for saturated conditions. The effect of different liquid surface tensions of water and ethanol, important under unsaturated conditions, was incorporated using a correction factor for the matric potential. Retention and saturated and unsaturated liquid conductivity of water and ethanol were systematically measured in sand and glass‐bead porous media with different wettabilites. Results showed no difference between the intrinsic hydraulic properties (measured with ethanol) and the hydraulic properties (measured with water) in fully wettable porous media. In water‐repellent porous media, intrinsic hydraulic properties deviate from measured hydraulic properties. Measurements further showed that the influence of soil water repellency on hydraulic conductivity and retention of water can be predicted as a function of the macroscopic contact angle (CA) in these model substrates. In summary, at least for well‐defined substrates such as sands, we suggest measuring the hydraulic conductivity and intrinsic liquid retention of the pore system with ethanol as a standard procedure.
A Numerical Study of the Impact of Precipitation Redistribution in a Beech Forest Canopy on Water and Aluminum Transport in a Podzol
Authors: Nikodem Antonín , Kodešová Radka , Drábek Ondřej , Bubeníčková Libuše , Borůvka Luboš , Pavlů Lenka , Tejnecký Václav
Published: May 2010

Vegetation influences water flow and solute transport in a soil not only because of its transpiration and root uptake of solutes, but also because of its impact on precipitation redistribution on the soil surface. The aim of this study was to assess the impact of the precipitation redistribution (stemflow and throughfall) under a beech tree (Fagus sylvatica L.) on the water regime and Al transport within the one‐ and two‐dimensional soil profiles using the HYDRUS‐1D and HYDRUS 2D/3D simulation models. The field study was performed at the Smědava Mountain in the Jizera Mountains in the Czech Republic. Simulations were performed for one selected soil (Haplic Podzol) on a relatively steep hillside. The simulation results for the 1D and 2D scenarios showed that the spatially redistributed precipitation under the beech tree caused funneled water flow and solute transport near the stem base. For the 1D scenarios, slightly higher weighted average water and solute discharge at the bottom were calculated as compared to those for the uniformly distributed precipitation. This spatial difference in discharge was simulated although the weighted average infiltration under the beech tree was lower than that for the uniformly distributed precipitation because runoff during stemflow around the tree bases was also obtained. For the 2D scenarios, all the fluxes simulated by assuming a spatially redistributed precipitation under the trees were higher than the fluxes obtained with the uniformly distributed precipitation because of the higher applied potential infiltration rates along the top boundary for that case. The funneled water and solute flow near the stem base caused the intensive simulated Al leakage around the tree stem. The Al content increased in the subsurface layer at the lower part of the simulated vertical transect as compared to that for the uniformly distributed precipitation. The results suggest that spatially redistributed precipitation should not be neglected when predicting potential leaching of toxic substances toward ground and surface water bodies.
How Differential Capillary Stresses Promote Particle Mobilization in Macroporous Soils: A Novel Conceptual Model
Authors: Michel E. , Majdalani S. , Di-Pietro L.
Published: May 2010

Soil particles of colloidal size have been known for more than two decades to facilitate the transport of adsorbed contaminants through the vadose zone. Understanding the mobilization mechanisms of these particles is thus essential for environment and water resource protection. It was recently shown that when the dry period before a rainfall event varies from 1 h to a few days, the mass of mobilized particles increases by more than an order of magnitude. This mobilization increase was indirectly linked to water content variations in preferential flow pathways. In this study, we developed a novel conceptual model of autochthonous particle mobilization in macroporous soils that explains this observation. We assumed that during a rain interruption, water loss from the macropore walls induces differential capillary stresses that weaken the structure of the walls. This weakening promotes mobilization during the passage of the infiltration front at the beginning of a subsequent rainfall event. The model computes the number of mobilized particles as a function of the rain interruption duration. We compared the computed mobilization with data obtained from a series of successive rainfall events performed at the column scale on a calcareous soil. Our simple model reproduced qualitatively well the observed variations of mobilization with rain interruption duration. This agreement strengthens the hypothesis of a mobilization process linked to capillary stresses occurring in the macropore walls. The model also provides insight into how the chronology of rainfall events undergone by the soil influences mobilization during successive events. Finally, it provides a novel link between colloid mobilization and pore structure evolution.
Theory for Source‐Responsive and Free‐Surface Film Modeling of Unsaturated Flow
Authors: Nimmo John R.
Published: May 2010

A new model explicitly incorporates the possibility of rapid response, across significant distance, to substantial water input. It is useful for unsaturated flow processes that are not inherently diffusive, or that do not progress through a series of equilibrium states. The term source‐responsive is used to mean that flow responds sensitively to changing conditions at the source of water input (e.g., rainfall, irrigation, or ponded infiltration). The domain of preferential flow can be conceptualized as laminar flow in free‐surface films along the walls of pores. These films may be considered to have uniform thickness, as suggested by field evidence that preferential flow moves at an approximately uniform rate when generated by a continuous and ample water supply. An effective facial area per unit volume quantitatively characterizes the medium with respect to source‐responsive flow. A flow‐intensity factor dependent on conditions within the medium represents the amount of source‐responsive flow at a given time and position. Laminar flow theory provides relations for the velocity and thickness of flowing source‐responsive films. Combination with the Darcy–Buckingham law and the continuity equation leads to expressions for both fluxes and dynamic water contents. Where preferential flow is sometimes or always significant, the interactive combination of source‐responsive and diffuse flow has the potential to improve prediction of unsaturated‐zone fluxes in response to hydraulic inputs and the evolving distribution of soil moisture. Examples for which this approach is efficient and physically plausible include (i) rainstorm‐generated rapid fluctuations of a deep water table and (ii) space‐ and time‐dependent soil water content response to infiltration in a macroporous soil.
Comparison of Heterogeneous Transport Processes Observed with Electrical Resistivity Tomography in Two Soils
Authors: Garré S. , Koestel J. , Günther T. , Javaux M. , Vanderborght J. , Vereecken H.
Published: May 2010

Preferential flow in soils can manifest itself in several ways. To illustrate this, we analyzed solute transport during a step tracer experiment in two soils expected to differ in their governing transport processes: a loamy sand and a silty soil. By combining electrical resistivity tomography (ERT), time domain reflectometry, and effluent measurements, we observed different preferential flow phenomena. The transport process was characterized using voxel‐ and column‐scale effective convective–dispersive equation (CDE) parameters, local velocities, and leaching surfaces. At the column scale, transport in the loamy sand was dominated by a homogenous convective–dispersive transport behavior, but at the scale of the voxel, preferential transport was observed. Transport in the silty soil was considerably more heterogeneous. Preferential flow was identified using ERT, voxel‐ and column‐scale effective CDE parameters, local velocities, and leaching surfaces. In these soils, a clear influence of soil layering on solute transport was observed.
Benchmarking of Two Dual‐Permeability Models under Different Land Use and Land Cover
Authors: Bachmair S. , Weiler M. , Nützmann G.
Published: May 2010

Land use and land cover (LULC) exert strong controls on soil properties and thus water flow in soils. The question arises whether existing models designed for simulating water and solute movement in heterogeneous soil include the effects of LULC on infiltration and percolation. To answer this question, the predictive capacity of two solute transport models was benchmarked to simulate flow processes in soils developed under different LULCs. To benchmark the model performance, dye tracer sprinkling experiments were conducted on five sites displaying similar soil texture and parent material but differences in LULC (two farmland sites, tilled and untilled, two grassland sites, and one deciduous forest site). Water content changes were continuously measured at different depths with time domain reflectometers during 60‐mm irrigation over 4 h. After the tracer application, vertical and horizontal soil sections were excavated and photographed. The experimental data were then compared with the simulations based on a multicriteria benchmarking strategy, including simulated vs. observed water content changes, solute distribution profiles, and maximum infiltration depth. Both models were capable of predicting water flow for one of the grassland sites but revealed severe weaknesses when additional flow processes not explicitly included in the model structure came into play. Poor model outcomes resulted from LULC effects such as a strong surface microtopography altering macropore flow initiation in the agricultural soils and from horizontally oriented roots and surface water repellency in the forest soil. Our results suggest that LULC effects need to be better incorporated into the conceptualization and parameterization of infiltration and percolation in hydrologic models to obtain realistic predictions concerning water quality and quantity.
Multifractal Analysis of Soil Porosity Based on Mercury Injection and Nitrogen Adsorption
Authors: Paz Ferreiro J. , Miranda J.G.V. , Vidal Vázquez E.
Published: May 2010

Pore‐size distributions (PSD) determined by different methods across various ranges of equivalent pore radius have shown multifractal characteristics. Here, the multifractal formalism was employed to describe both mercury injection porosimetry (MIP) and nitrogen adsorption isotherms (NAI) curves, measured in a Mollisol and in a Vertisol. Four different soil use intensities and three replicate samples per treatment were analyzed. Mercury injection and nitrogen adsorption were used to measure PSDs for equivalent pore radii 150 to 0.005 μm and 0.1 to 0.001 μm, respectively. The scaling properties of all the Hg injection curves and N2 adsorption isotherms could be fitted reasonably well with multifractal models. A generalized dimension spectrum, Dq, led to a better definition of multifractal scaling than a singularity spectrum, f(α). Parameters derived from these two functions showed highly significant differences between MIP and NAI in both soil types. Thus, mean values of entropy dimension, D1, and correlation dimension, D2, were significantly higher for mercury injection than for nitrogen adsorption. On the contrary, Hölder exponents of order zero, α0, were on average significantly higher for nitrogen adsorption. Also, mean widths of the f(α) spectra were much larger for nitrogen adsorption. These results indicate heterogeneity due to the presence of different porous domains at the scale of primary soil aggregates. The multifractal approach was useful to characterize the heterogeneity of the soil pore system and to distinguish between different patterns of PSD corresponding to various degrees of clustering.
Physical and Numerical Coupling in Dual‐Continuum Modeling of Preferential Flow
Authors: Vogel Tomas , Brezina Jan , Dohnal Michal , Dusek Jaromir
Published: May 2010

Dual‐continuum models are useful for describing flow in porous systems with significant local pressure disequilibrium between slow moving water, contained in the porous matrix, and fast moving water in preferential pathways. The formation and intensity of preferential flow depends on the contrast between the hydraulic properties of the two flow domains as well as on the properties of their interface. In this study, we focused on both physical coupling of the flow domains through the mass transfer term and numerical coupling of the respective governing equations. The set of governing equations was alternatively solved using a sequentially coupled (SC) approach and a fully coupled (FC) approach. The SC approach was shown to be computationally more efficient for strongly developed preferential flow in systems with high interfacial resistance; however, it becomes numerically unstable for weak preferential flow associated with low interfacial resistance. The FC approach is a computationally more expensive yet numerically more robust alternative, capable of simulating a complete class of intermediate flow regimes ranging from strongly preferential flow in a dual‐continuum system to nonpreferential flow in a single‐continuum system. To illustrate the performance of the numerical coupling approaches in conjunction with the effect of different interfacial resistances, we present a simple example problem involving one‐dimensional near‐saturated flow in a vertical soil column.
Characterization of Water Infiltration and Redistribution for Two‐Dimensional Soil Profiles by Moment Analyses
Authors: Sperling Or , Lazarovitch Naftali
Published: May 2010

Soil water moments are a set of statistical characteristics calculated from the water‐content values of a soil profile. The moments indicate the water's center of mass location on the x and z axes and the water distribution around those axes, thereby producing a clear and unique temporal and spatial description of water location using only four parameters. Our objective in this research was to investigate soil water behavior during and after an infiltration event using the soil water moments parameters. Despite their advantages, soil water moments have been mainly presented for numerical solutions rather than physical infiltration experiments because their calculation requires a vast collection of water‐content values in the soil profile. Because it is difficult to obtain such data by known methods of soil sampling or by sensors installed in situ, we developed a method based on image analysis. Continuous images were analyzed for their color intensities. These were converted to water‐content values and the soil water moments were then calculated. We performed laboratory infiltration experiments with two soils, sand and sandy loam, for analysis and comparison using the water moments. Infiltration occurred for 35 min at a discharge rate of 0.285 cm3 min−1, followed by 130 min of redistribution. The water moments presented a clear picture of water infiltration and redistribution, as they varied in time and differed between soils. While in the sand the water's center of mass reached a depth of 5 cm, and the water was distributed almost uniformly around it, in the sandy loam, the center of mass only reached a depth of 2.5 cm, and water distribution resembled a flat horizontal ellipse. Any fraction of water added can be related to a “probability” curve relating the size of the ellipse that contains that amount of water. Remarkably, the probability curves are identical for all times and soils. The consistency of the probability relationships can be exploited to pinpoint the extent of subsurface water for any fraction of the volume added. Furthermore, a high correspondence was found between the results and previous numerical solution outputs.
Can Continuum Extensions to Multiphase Flow Models Describe Preferential Flow?
Authors: DiCarlo David A.
Published: May 2010

Gravity‐driven preferential flow paths (fingers) have been shown to be the result of nonmonotonic saturation profiles observed during constant‐flux, one‐dimensional infiltration. These nonmonotonic profiles, also known as saturation overshoot, cannot be described by traditional unsaturated continuum flow models, such as the Richards equation. Instead, continuum models require additional extensions, higher order in either time or space, which are still open to much question. In this study, an extensive data set was obtained on preferential flow and overshoot behavior in well‐sorted sands. The overshoot behavior is the strongest evidence of dynamic effects in porous media because other reported experimental evidence can be the result of varying measuring volumes or media heterogeneities. Thus the extensive overshoot data set provides the best testing ground for the various proposed extensions, and the data set was compared with recently proposed continuum extensions to unsaturated flow models.
Noninvasive Observations of Flow Patterns in Locally Heterogeneous Mine Soils using Neutron Radiation
Authors: Badorreck Annika , Gerke Horst H. , Vontobel P.
Published: May 2010

The description of water flow in mine soils is limited by heterogeneities due to the dumping of partly mixed overburden sediments resulting in a soil matrix with embedded lignitic or fine‐textured fragments. Previous attempts assuming a mobile–immobile type dual‐porosity model failed to explain soil core outflow experiments. Our objective in this study was to improve the understanding of flow in mine soils by visualizing flow paths with neutron radiography (NR) and neutron tomography (NT) using H2O as tracer. The methodological focus was to develop a setup for intact soil samples. Two‐dimensional NR technique was used to observe steady‐state infiltration in 2‐cm‐thick unsaturated (i.e., −5 and −30 hPa) soil slabs. In a three‐dimensional NT approach, we determined the distributions of infiltrating H2O in a soil core using a multistep in‐ and outflow experiment (i.e., at −30, −15, −3, and −30 hPa) with installed tensiometers. The NR time sequences allowed distinguishing millimeter‐scale flow paths in the soil slabs. The NT experiment revealed higher H2O contents in the vicinity of fragments; tensiometer data indicated local nonequilibrium in pressure heads between fragment and matrix pore regions. The results suggest that under near‐saturated conditions, water preferably flows around fragments within a more continuous pore network that exists locally in the matrix and that flow patterns depend on the structure of the embedded fragments. The separate consideration of this pore network may improve flow description in soils with comparable heterogeneity. Neutron imaging proved to be useful for complex natural soils as well, although quantification of H2O content dynamics was still limited here by residual water and lignitic carbon contents.
DRIFT Mapping of Organic Matter Composition at Intact Soil Aggregate Surfaces
Authors: Leue Martin , Ellerbrock Ruth H. , Gerke Horst H.
Published: May 2010

In structured soils, interaction of percolating water and reactive solutes with the soil matrix is often restricted to the outer surfaces of the preferential flow paths. Such surfaces of soil aggregates and biopores are mostly covered by organic matter (OM) that finally controls wettability, sorption, and transfer properties of the flow pathways. However, the local OM properties along such surfaces are largely unknown to date because the coatings are relatively thin and vulnerable. The objective of this study was to determine and compare the local two‐dimensional distribution of soil OM composition at intact aggregate surfaces that serve as preferential flow paths. The Fourier transformed infrared spectroscopy in diffuse reflectance mode (diffuse reflectance infrared Fourier transform, DRIFT) was applied to determine transects and grids of OM functional group data (i.e., CH/CO ratios) on undisturbed and intact surfaces of soil aggregate samples using a DRIFT mapping procedure in 1‐mm steps. The aggregate sample surfaces could be distinguished by DRIFT mapping in areas from earthworm burrows, root channels, and aggregate coatings. The water drop infiltration time of these structural surfaces appeared to correspond with CH/CO ratios for uncoated crack surfaces but less so for earthworm burrows. The results show that coatings at preferential flow‐path surfaces differed locally in terms of OM composition, distribution, and possibly also in wettability, indicating yet unknown implications for preferential movement of water and reactive solutes.
Water Content Wave Approach Applied to Neutron Radiographs of Finger Flow
Authors: Hincapié Ingrid , Germann Peter
Published: May 2010

Finger flow along distinct paths in homogeneous soils and other porous media is well known, but its characterization and quantification with existing approaches is challenging. Neutron radiography produces 2‐d images of water content distributions that allow testing of a water content wave approach to finger flow. Neutron radiographs were taken every 25 s during finger flow in a sand box that was 200 mm wide, 400 mm deep, and 5 mm thick. The sand was sieved to 0.2‐ to 0.5‐mm diameter. The area of finger flow was 30 mm wide. We approached water content variations during infiltration and redistribution in the finger flow area with a water content wave model that assumes gravity as the driving force and viscosity to oppose it. The two model parameters are thickness of the water film F (μm) and its contact length L (m−1) per unit cross‐sectional area A (m2) between the film and the stationary parts of the sand–water–air system. The velocity vW (m s−1) of the wetting front is an exclusive function of F, while mobile water content and volume flux density are functions of L and F We observed constant vW across the entire depth of investigation, which indicates constant F despite the considerable spatial variations in bulk density and porosity. The contact length L expresses the surface area per unit volume of the medium onto which momentum dissipates. The value of L compared well with the estimated surface area per volume of the smallest sand fraction during unhampered flow; however, it increased drastically when flow was influenced by the capillary fringe at the bottom of the sand box.
Tracing the Entrapped Air in Heterogeneous Soil by Means of Magnetic Resonance Imaging
Authors: Sněhota Michal , Císlerová Milena , Amin M.H. Gao , Hall Lawrence D.
Published: May 2010

Magnetic resonance imaging (MRI) was used to study the process of infiltration in an undisturbed core of coarse sandy loam during a repeated ponded infiltration experiment (RPI), in which the first infiltration was conducted into a naturally dry sample and the second infiltration into a wet sample. The primary aim was to assess the change in distribution of entrapped air in the undisturbed soil sample and its influence on steady‐state flow rates. The RPI experiment was conducted on a sample 8.9 cm in diameter and 8.4 cm high. Concurrently with the MRI monitoring, pressure heads and fluxes were measured. Multiple‐slice maps of longitudinal relaxation time (T1), which is a parameter related to the surface/volume ratio, and proton density (M0), related to the water content, covered almost the entire volume of the sample. The T1 mapping was conducted during four stages of the experiment: steady‐state flow of the first (I1) and second (I2) infiltrations and the equilibrium stage after drainage of the sample (Stages D1 and D2). During I1 and I2, the highest values of M0 and T1 were detected in the upper 3 cm of the sample, which is in good agreement with findings of computer tomography showing lower sample density and higher porosity in this region. The drop in the quasi‐steady‐state flow rate that was observed between the I1 and I2 runs corresponded to the decline in T1 and M0 in the upper 4 cm of the sample. The decrease in T1 indicates replacement of water in large pores with trapped air, while a lower M0 signifies a general decrease of water content in the affected areas.