Columbus Air Force Base Research Articles

Damage Analysis and Close-Range Radar Observations of the 13 April 2019 Greenwood Springs, Mississippi, Tornado during VORTEX-SE Meso18-19

Abstract A tornado outbreak occurred across the Southeast United States on 13–14 April 2019, during the Verification of the Origins of Rotation in Tornadoes Experiment–Southeast (VORTEX-SE) Meso18-19 experiment. Among the most noteworthy events was a pair of large tornadoes in Monroe County, Mississippi, near the Columbus Air Force Base (GWX) Weather Surveillance Radar–1988 Doppler (WSR-88D). The second tornado, near the Greenwood Springs community, formed within the “no data” region near the radar and passed about 900 m to its east, rapidly strengthening into an intense tornado. This tornado produced forest devastation and electrical infrastructure damage up to at least EF4 intensity. The maximum radial velocity from GWX was 81.5 m s−1 (182 mph) in a resolution volume centered at 56 m (183 ft) above radar level. This paper presents a damage survey of the Greenwood Springs tornado and compares this assessment to the GWX data. A displacement of the maximum forest damage from the maximum radial velocity, despite the radar beam sampling <100 m ARL, is documented, as well as other likely effects of debris loading by the tornado on the observed radar signatures. The radar observations are placed into context with past mobile radar studies to illustrate the unique nature of this dataset. The relationship between radar data and damage observations, the implications for tornado structure in rough terrain and land cover, and the use of forest damage and radar data in tornado intensity estimation are discussed. Significance Statement This study showcases radar and damage observations of an intense tornado in a forested region of Mississippi. The formation of the tornado within 1 km of a WSR-88D allowed for near-surface radar observations to be collected as significant tree destruction was occurring. Doppler velocities below 60 m above radar level (ARL), near tree canopy top, exceeded 80 m s−1. Tree damage patterns were complicated while the tornado was near maximum intensity. The most severe tree damage was notably displaced from the highest radar-observed velocities, despite the radar sampling as low as 45 m ARL. These findings highlight challenges in utilizing radar data to estimate tornado intensity and structure, particularly in a region of relatively high surface and terrain roughness.

Identifying the Fractional Orders in Anomalous Diffusion Models from Real Data

An attempt is made to identify the orders of the fractional derivatives in a simple anomalous diffusion model, starting from real data. We consider experimental data taken at the Columbus Air Force Base in Mississippi. Using as a model a one-dimensional fractional diffusion equation in both space and time, we fit the data by choosing several values of the fractional orders and computing the infinite-norm “errors”, representing the discrepancy between the numerical solution to the model equation and the experimental data. Data were also filtered before being used, to see possible improvements. The minimal discrepancy is attained correspondingly to a fractional order in time around 0 . 6 and a fractional order in space near 2. These results may describe well the memory properties of the porous medium that can be observed.

Structure Adaptation in Stochastic Inverse Methods for Integrating Information

The use of inverse modeling techniques has greatly increased during the past several years because the advances in numerical modeling and increased computing power. Most of these methods require an a priori definition of the stochastic structure of conductivity (K) fields that is inferred only from K measurements. Therefore, the additional conditioning data, that implicitly integrate information not captured by K data, might lead to changes in the a priori model. Different inverse methods allow different degrees of structure adaptation to the whole set of data during the conditioning procedure. This paper illustrates the application of a powerful stochastic inverse method, the Gradual Conditioning (GC) method, to two different sets of data, both non-multiGaussian. One is based on a 2D synthetic aquifer and another on a real-complex case study, the Macrodispersion Experiment (MADE-2), site on Columbus Air Force Base in Mississippi (USA). We have analyzed how additional data change the a priori model on account of the perturbations performed when constraining stochastic simulations to data. Results show how the GC method tends to honour the a priori model in the synthetic case, showing fluctuations around it for the different simulated fields. However, in the 3D real case study, it is shown how the a priori structure is slightly modified not obeying just to fluctuations but possibly to the effect of the additional information on K, implicit in piezometric and concentration data. We conclude that implementing inversion methods able to yield a posteriori structure that incorporate more data might be of great importance in real cases in order to reduce uncertainty and to deal with risk assessment projects.

Collapse of higher‐order solute concentration moments in groundwater transport

In this paper, we use numerical simulations based on a Lagrangian framework to study contaminant transport through highly heterogeneous porous media due to advection and local diffusion (under local diffusion, we assume coupled effect of mechanical dispersion and molecular diffusion). The analysis of the concentration field is done for the case of a two‐dimensional hydraulic conductivity domain representing the aquifer, with three log‐conductivity structures that differ in spatial correlation. In addition to different conductivity structures, we focus our investigation on mild and highly heterogeneous porous media characterized by the values of hydraulic log‐conductivity variance being equal to 1 and 8. In the concentration moment analysis, we show that a linear relationship exists between higher‐order to second‐order normalized concentration moments on a log‐log scale up to the fourth‐order moment. This leads to the important finding that moments of a higher than the second order can be derived based on information about the first two concentration moments only. Such a property has been observed previously for boundary‐layer water channels, wind tunnels, and turbulent diffusion in open terrain and laboratory experiments. Normalized moments are shown to collapse for different types of hydraulic conductivity structures, Peclet (Pe) numbers and values. In the case of local diffusion absence, a linear log‐log relationship is derived analytically and is set as a lower limit. The deviation from the lower limit is explained to be predominantly caused by the local diffusion, which needs time to evolve. In the case of local diffusion presence, we define the moment deriving function (MDF) to describe the linear log‐log relationship between higher‐order concentration moments to the second‐order normalized one. Finally, the comparison between numerical results and those obtained from the Columbus Air Force Base Macrodispersion Experiment (MADE 1) is used to demonstrate the robustness of the moment collapse.

A comparative study of three-dimensional hydraulic conductivity upscaling at the macro-dispersion experiment (MADE) site, Columbus Air Force Base, Mississippi (USA)

Simple averaging, simple-Laplacian, Laplacian-with-skin, and non-uniform coarsening are the techniques investigated in this comparative study of three-dimensional hydraulic conductivity upscaling. The reference is a fine scale conditional realization of the hydraulic conductivities at the MAcro-Dispersion Experiment site on Columbus Air Force Base in Mississippi (USA). This realization was generated using a hole-effect variogram model and it was shown that flow and transport modeling in this realization (at this scale) can reproduce the observed non-Fickian spreading of the tritium plume. The purpose of this work is twofold, first to compare the effectiveness of different upscaling techniques in yielding upscaled models able to reproduce the observed transport behavior, and second to demonstrate and analyze the conditions under which flow upscaling can provide a coarse model in which the standard advection–dispersion equation can be used to model transport in seemingly non-Fickian scenarios. Specifically, the use of Laplacian-based upscaling technique coupled with a non-uniform coarsening scheme yields the best results both in terms of flow and transport reproduction, for this case study in which the coarse blocks are smaller than the correlation ranges of the fine scale conductivities.

Geological modeling of submeter scale heterogeneity and its influence on tracer transport in a fluvial aquifer

We developed a new model of aquifer heterogeneity to analyze data from a single‐well injection‐withdrawal tracer test conducted at the Macrodispersion Experiment (MADE) site on the Columbus Air Force Base in Mississippi (USA). The physical heterogeneity model is a hybrid that combines 3‐D lithofacies to represent submeter scale, highly connected channels within a background matrix based on a correlated multivariate Gaussian hydraulic conductivity field. The modeled aquifer architecture is informed by a variety of field data, including geologic core sampling. Geostatistical properties of this hybrid heterogeneity model are consistent with the statistics of the hydraulic conductivity data set based on extensive borehole flowmeter testing at the MADE site. The representation of detailed, small‐scale geologic heterogeneity allows for explicit simulation of local preferential flow and slow advection, processes that explain the complex tracer response from the injection‐withdrawal test. Based on the new heterogeneity model, advective‐dispersive transport reproduces key characteristics of the observed tracer recovery curve, including a delayed concentration peak and a low‐concentration tail. Importantly, our results suggest that intrafacies heterogeneity is responsible for local‐scale mass transfer.

Lessons Learned from 25 Years of Research at the MADE Site

Field studies at well-instrumented research sites have provided extensive data sets and important insights essential for development and testing of transport theories and mathematical models. This paper provides an overview of over 25 years of research and lessons learned at one of such field research sites on the Columbus Air Force Base in Mississippi, commonly known as the Macrodispersion Experiment (MADE) site. Since the mid-1980s, field data from the MADE site have been used extensively by researchers around the world to explore complex contaminant transport phenomena in highly heterogeneous porous media. Results from field investigations and modeling analyses suggested that connected networks of small-scale preferential flow paths and relative flow barriers exert dominant control on solute transport processes. The classical advection-dispersion model was shown to inadequately represent plume-scale transport, while the dual-domain mass transfer model was found to reproduce the primary observed plume characteristics. The MADE site has served as a valuable natural observatory for contaminant transport studies where new observations have led to better understanding and improved models have sprung out analysis of new data.

Relative importance of dispersion and rate‐limited mass transfer in highly heterogeneous porous media: Analysis of a new tracer test at the Macrodispersion Experiment (MADE) site

A single‐well injection‐withdrawal (SWIW) bromide tracer test was conducted to further investigate transport processes at the Macrodispersion Experiment (MADE) site on Columbus Air Force Base in Mississippi. The bromide breakthrough curve is highly asymmetric and exhibits an early time high‐concentration peak followed by an extended period of low‐concentration tailing. Comparisons of results simulated by advection‐dispersion (AD) and dual‐domain mass transfer (DDMT) models with the field data show that the DDMT model more accurately represents the magnitudes of both the early high‐concentration peak and the later low‐concentration tail. For both the AD and DDMT models, the match with field data is enhanced by incorporating hydraulic conductivity information from new direct‐push profiling methods. The Akaike information criterion for the DDMT models is much smaller than that for the AD models in both the homogeneous and heterogeneous cases investigated in this work. The improved match of the DDMT model with the SWIW test data supports the hypothesis of mass transfer processes occurring at this highly heterogeneous site.

Gradual conditioning of non-Gaussian transmissivity fields to flow and mass transport data: 3. Application to the Macrodispersion Experiment (MADE-2) site, on Columbus Air Force Base in Mississippi (USA)

A large-scale natural-gradient tracer experiment conducted in a highly heterogeneous aquifer at the Macrodispersion Experiment (MADE-2) site on Columbus Air Force Base in Mississippi (USA) is simulated using the gradual conditioning (GC) method. This methodology allows the stochastic inversion of hydraulic conductivity data (K), and transient piezometric (h) and solute concentration (c) measurements in a non-Gaussian framework, including soft and secondary data. Results show (i) that the GC method allows the reproduction of the heavy tailing of the tracer plume as observed in the field by using a dual-domain mass transfer approach together with conditioning to K, h and c data, in a non-Gaussian framework, (ii) a good agreement between data and simulated mass distribution at time 328 days, including the non-Gaussian plume behaviour, (iii) the necessity of using a dual-domain mass transfer approach – or other transport equation different to the advection–dispersion equation (ADE) – when treating with upscaled models regardless of what random function is used to generate the K distribution, (iv) the reduction of uncertainty results when conditioning to all available information and not only to K data, and (v) the importance of preferential flow paths on the anomalous tracer plume spreading at the MADE site. Besides, the viability of the GC method in a highly heterogeneous 3D aquifer is proven, and also its contribution to the state-of-the-art in stochastic inverse modelling.

Columbus Air Force Base medication profile intervention practice innovation

Objective: To determine whether community pharmacist-initiated interventions containing a recommendation to adjust prescribed medication therapy and delivered via fax are viewed as helpful by prescribers and to what extent prescribers accept those recommendations. DesignCross-sectional. SettingColumbus Air Force Base (Columbus, MS) during a 3-month period in August through October 2007. Participants57 patient profiles were reviewed by pharmacy staff. InterventionPharmacy staff evaluated patient profiles with eight or more active medications for drug interactions, therapeutic duplications, ability to simplify complex drug regimens, and opportunities for additional therapy. After reviewing a patient profile, the pharmacist completed a medication management report, noted any recommendations about medication therapy, and faxed the report to the patient's primary care provider. Physicians were asked to return a form detailing their response to the medication management report. Main outcome measureWhether pharmacist recommendations were deemed helpful by prescribers in making clinical decisions. Secondary outcome measures included the degree to which prescribers accepted pharmacist recommendations and how quickly providers responded to pharmacist recommendations. ResultsThe pharmacist-initiated medication management fax had a 64.9% response rate from prescribers and was considered helpful by 97.3% of prescribers who returned the form to the pharmacist. In addition, the majority of prescribers stated via the form that they would address the pharmacist's concerns at the next patient visit or call and schedule an appointment with the patient. ConclusionAs this initiative continues and grows, prescribers will be more aware of the medication management fax form program and, theoretically, will be more likely to respond to pharmacist recommendations.

Prediction of contaminant plumes (shapes, spatial moments and macrodispersion) in aquifers with insufficient geological information

The first Macrodispersion Experiment (MADE1) at Columbus Air Force Base in northern Mississippi is utilized to perform numerical simulations of solute transport in an aquifer. The purpose is to illustrate the capability of the coupled Markov chain (CMC) model in delineating the complex geometrical configuration at the site for solute transport simulations under the lack of geological information. The CMC model is also used to study the effect of reducing geological information on the transport predictions in terms of plume configuration, first and second spatial moments and macrodispersion. The results show the power of the coupled Markov chain methodology in delineating aquifer heterogeneity at the site. Conditional simulations on 16, 9 and 6 boreholes show reasonably the same plume behavior in terms of average longitudinal and vertical extensions, especially in the far-field; 9 boreholes seem to provide practically acceptable results in terms of the global plume shape. This indicates more reliability on the use of the CMC model for subsurface characterization. Comparison of CMC model results, in terms of aquifer characterization, with the model used by Eggleston and Rojstaczer [Water Resour. Res. 34 (1998) 2155] (polynomial regression trend, Kalman filter trend, hydrofacies trend and Kriging) shows that the CMC model behaves better. The CMC model conditioned on 9 and 16 boreholes with mid-range conductivities for each lithology captures both the plume shape and the observed plume spatial moments at the MADE site.

Natural Attenuation of Fuel Hydrocarbon Contaminants:Correlation of Biodegradation with Hydraulic Conductivity in a Field Case Study

Two biodegradation models are developed to represent natural attenuation of fuel-hydrocarbon contaminants as observed in a comprehensive natural-gradient tracer test in a heterogeneous aquifer on the Columbus Air Force Base in Mississippi, USA. The first, a first-order mass loss model, describes the irreversible losses of BTEX and its individual components, i.e., benzene (B), toluene (T), ethyl benzene (E), and xylene (X). The second, a reactive pathway model, describes sequential degradation pathways for BTEX utilizing multiple electron acceptors, including oxygen, nitrate, iron and sulfate, and via methanogenesis. The heterogeneous aquifer is represented by multiple hydraulic conductivity (K) zones delineated on the basis of numerous flowmeter K measurements. A direct propagation artificial neural network (DPN) is used as an inverse modeling tool to estimate the biodegradation rate constants associated with each of the K zones. In both the mass loss model and the reactive pathway model, the biodegradation rate constants show an increasing trend with the hydraulic conductivity. The finding of correlation between biodegradation kinetics and hydraulic conductivity distributions is of general interest and relevance to characterization and modeling of natural attenuation of hydrocarbons in other petroleum-product contaminated sites.

Numerical simulation of a natural attenuation experiment with a petroleum hydrocarbon NAPL source.

A three-dimensional solute transport model with biological reactions is presented for simulating the natural attenuation study (NATS) at the Columbus Air Force Base in eastern Mississippi. NATS consisted of the release of a petroleum-based nonaqueous phase liquid (NAPL) and subsequent monitoring of BTEX (benzene, toluene, ethylbenzene, p-xylene), naphthalene, decane, and bromide in a shallow, unconfined aquifer. Conceptual and mathematical models were developed for NAPL source release, sequential aerobic/anaerobic biodegradation, and sorption during NATS. A multiple species, solute transport code (SEAM3D) was used to simulate fully three-dimensional transport and aerobic, nitrate-reducing, ferrogenic, and methanogenic hydrocarbon biodegradation. Simulation results matched individual BTEX concentration distributions collected five- and nine-months following NAPL release. SEAM3D mass-balance calculations at t = nine months indicated that 49% of the hydrocarbon mass that dissolved into the aqueous phase was consumed by biodegradation, 13% of this mass was sorbed, and the remaining 38% was present in the aqueous phase. Mass calculations at t = nine months further indicated that aerobic biodegradation accounted for the majority of hydrocarbon biodegradation (46% of the biodegraded mass), followed by ferrogenesis (28%), nitrate-reduction (21%), and methanogenesis (5%). Model results were particularly sensitive to the NAPL release rate, the initial ferric iron (Fe[III]) concentration, hydrocarbon utilization rates, initial condition for the anaerobic microbial populations, and dispersivity.

A dual‐domain mass transfer approach for modeling solute transport in heterogeneous aquifers: Application to the Macrodispersion Experiment (MADE) site

A large‐scale natural‐gradient tracer test in a highly heterogeneous aquifer at the Macrodispersion Experiment (MADE) site on the Columbus Air Force Base in Mississippi is simulated using three‐dimensional hydraulic conductivity distributions derived from borehole flowmeter test data. Two methods of hydraulic conduct(fBm), are used to construct the hydraulic conductivity distributions needed by the numerical model. Calculated and observed mass distributions are compared to evaluate the effectiveness of the dual‐domain mass transfer approach relative to the single‐domain advection‐dispersion approach. The results show that the classical Fickian advection‐dispersion model can reproduce reasonably well the observed tritium plume above a certain concentration limit but fails to reproduce the extensive spreading of the tracer at diluted concentrations as observed in the field. The alternative dual‐domain mass transfer model is able to represent the rapid, anomalous spreading significantly better while retaining high concentrations near the injection point. This study demonstrates that the dual‐domain mass transfer approach may offer a practical solution to modeling solute transport in highly heterogeneous aquifers where small‐scale preferential flow pathways cannot be fully and explicitly represented by the spatial discretization of the numerical model.

Can We Predict Subsurface Mass Transport?

Predictions of contaminant transport produced by computer models are now widely used to evaluate health risks, determine remediation strategies, and guide environmental regulatory decisions. But model prediction errors are not generally well-known or quantified. In this study, the results of an extensive tracer test at the Columbus Air Force Base (CAFB), MS, test site are used to quantify error in computer model predictions of groundwater contaminant movement in the subsurface. Our modeling assumes no knowledge of the observed solute transport, uses widely applied modeling methods to generate computer predictions, and uses permeability and water levels as input data. Predicted and observed mass transport differ significantly, despite the relative abundance of aquifer data. It is not possible to accurately predict mass transport at CAFB using our approach because permeability cannot be characterized at the necessary resolution. Prediction errors at Superfund sites and other contaminated groundwater sites m...

Changes in Subsurface Catabolic Gene Frequencies during Natural Attenuation of Petroleum Hydrocarbons

Subsurface hydrocarbon contamination associated with petroleum spills is a widespread occurrence that presents a significant threat to groundwater resources. The natural attenuation test site (NATS) at Columbus Air Force Base, MS, provided a unique opportunity to monitor changes in the molecular microbial ecology as well as stimulation of natural biodegradative processes under transient field study conditions. A large, synthetic jet fuel mixture containing BTEX compounds and naphthalene in a decane carrier was introduced into the subsurface. Over 462 days, a plume of hydrocarbon contamination developed and stabilized at a distance of less than 15 m downgradient from the source area. Exposure of indigenous microorganisms to the contaminant hydrocarbons was evaluated using an array of gene probes targeting common genotypes associated with the aerobic biodegradation of BTEX and naphthalene. Each of the targeted genotypes alkB, nahA, nahH, todC1C2, and xylA showed significant responses to hydrocarbon exposure. Aerobic mineralization potentials of selected contaminants were greater in sediments collected from within the plume relative to uncontaminated areas, suggesting that an aerobic contaminant-degrading community successfully developed within the plume. An increase in aerobic degradation activity coincided with the arrival of the hydrocarbon front within the well field. The Natural Attenuation Study at Columbus AFB successfully linked adaptations of indigenous microorganisms to hydrocarbon exposure during a transient field study.

Assessment of the Microbiological Potential for the Natural Attenuation of Petroleum Hydrocarbons in a Shallow Aquifer System.

Abstract A multidisciplinary field study investigating the fate and transport of petroleum hydrocarbons commonly associated with jet-fuel contamination is currently underway at Columbus Air Force Base (AFB), Mississippi. Sixty sediment cores from 12 boreholes were recovered from the study aquifer. The goal of this initial sampling was to characterize the potential microbial activity using 14C-labeled substrates, as well as the presence, abundance, and distribution of specific hydrocarbon degrading genotypes using DNA:DNA hybridization. Enumeration of total microbial abundance using a 16S rDNA universal oligonucleotide probe was compared to traditional enumeration methods. Total culturable populations determined by spread plate analysis ranged from a low of 10(4) to more than 10(6) organisms per gram sediment. Microbial abundance estimated by DNA hybridization studies with 16S rDNA genes ranged from 10(7) to 10(8) organisms per gram sediment. Molecular analysis of aquifer samples using DNA probes targeting genes encoding the degradative enzymes alkane hydroxylase (alkB), catechol 2,3-dioxygenase (nahH), naphthalene dioxygenase (nahA), toluene dioxygenase (todC1C2), toluene monooxygenase (tomA), and xylene monooxygenase (xylA), as well as two probes measuring methanogenic microorganisms, codh (carbon monoxide dehydrogenase) and mcr (methyl coenzyme reductase), revealed that each target gene sequence was present in nearly all 60 samples. The presence of organisms demonstrating the phenotype to degrade BTEX and naphthalene was further supported using mineralization assays with 14C-labeled benzene, toluene, naphthalene, and phenanthrene. Minimal activity occurred during the first 24 hours. After a period of 5-7 days, greater than 40% of the target compounds were mineralized in aquifer sediments.

Identification of large‐scale hydraulic conductivity trends and the influence of trends on contaminant transport

We examine the identification of large‐scale spatial trends in hydraulic conductivity and the influence of these trends on contaminant transport. Using three different trend identification methods, polynomial regression and Kaiman filtering, which fit smooth functions, and hydrofacies delineation, which constructs a geologic model, we try to identify the hydraulic conductivity patterns controlling solute transport in a heavily sampled heterogeneous aquifer on Columbus Air Force Base, Mississippi. Even with >2400 hydraulic conductivity measurements, unambiguous determination of large‐scale trends is not possible. None of the estimated hydraulic conductivity trends gives transport simulations that reproduce the observed non‐Gaussian transport behavior. Hydrofacies delineation and Kalman filtering give the best results. While the influence of the identified large‐scale trends on advective transpo) hydraulic conductivity structures.

Heterogeneity of sorption and transport-related properties in a sand–gravel aquifer at Columbus, Mississippi

Properties related to sorption and transport of organic compounds have been determined on 126 sections of 17 cores taken in an aquifer at Columbus Air Force Base in Columbus, MS. Each core section was homogenized prior to analysis. Organic carbon content (OC), specific surface area (SA), distribution coefficient ( K d) for naphthalene, and particle size distribution were measured on each section. Hydraulic conductivity ( K h) for each section was calculated from the particle size distributions. K h values obtained were comparable with those from earlier borehole flowmeter and pulse tracer tests. Frequency distributions for all properties were lognormal. The arithmetic means and standard deviations for all samples are: OC=0.028% (+0.031, −0.015), SA=4.02 m 2/g (+3.95, −1.99), K d=0.198 l/kg (+0.195, −0.098), K h=0.00033 m/s (+0.00051, −0.00020). These standard deviations are asymmetrical about the mean because statistics were calculated using log-transformed data, and antilogarithms then taken to obtain the results in the units of property measurement. Variabilities, expressed as coefficients of variation, were similar for all properties. Correlations between the properties were investigated. A good correlation between naphthalene K d and OC ( r=0.78) was found, and other correlations were weak, thus indicating that organic carbon content may control sorption of nonpolar organic solutes in this low carbon aquifer. Autocorrelation (variogram) analysis indicated that, for all properties, correlation lengths were less than the distance between sample points, which were separated by about 20 m horizontally and 1 m vertically. Separate statistical analysis of two widely separated groups of wells showed the groups similar in all properties, except organic carbon. Large-scale inhomogeneity was not detected, although earlier tracer tests produced irregular plumes indicating inhomogeneity in observed solute transport. Implications of the results to site characterization, in situations where aquifers are heterogeneous on short length scales, are discussed.

Theory of anomalous chemical transport in random fracture networks

We show that dominant aspects of chemical (particle) transport in fracture networks\char22{}non-Gaussian propagation\char22{}result from subtle features of the steady flow-field distribution through the network. This is an outcome of a theory, based on a continuous time random walk formalism, structured to retain the key space-time correlations of particles as they are advected across each fracture segment. The approach is designed to treat the complex geometries of a large variety of fracture networks and multiscale interactions. Monte Carlo simulations of steady flow in these networks are used to determine the distribution of velocities in individual fractures as a function of their orientation. The geometry and velocity distributions are used, in conjunction with particle mixing rules, to map the particle movement between fracture intersections onto a joint probability density $\ensuremath{\psi}(\mathbf{r},t).$ The chemical concentration plume and breakthrough curves can then be calculated analytically. Particle tracking simulations on these networks exhibit the same non-Gaussian profiles, demonstrating quantitative agreement with the theory. The analytic plume shapes display the same basic behavior as extensive field observations at the Columbus Air Force Base, Mississippi. The quantitative correlation between the time dependence of the mean and standard deviation of the field plumes, and their shape, is predicted by the theory.