30 CFR 816.105 - Backfilling and grading: Thick overburden.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Backfilling and grading: Thick overburden. 816...-SURFACE MINING ACTIVITIES § 816.105 Backfilling and grading: Thick overburden. (a) Definition. Thick... surrounding terrain. (b) Performance standards. Where thick overburden occurs within the permit area, the...

30 CFR 819.19 - Auger mining: Backfilling and grading.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Auger mining: Backfilling and grading. 819.19 Section 819.19 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE... MINING § 819.19 Auger mining: Backfilling and grading. (a) General. Auger mining shall be conducted in...

30 CFR 819.19 - Auger mining: Backfilling and grading.

Code of Federal Regulations, 2010 CFR

2010-07-01

... safety factor for the stability of the backfill of at least 1.3. (2) All spoil generated by the auger... nonacid-, nontoxic-forming material and the backfill graded to a slope which is compatible with the approved postmining land use and which provides adequate drainage and long-term stability. (4) Any remnant...

UNDERGROUNG PLACEMENT OF COAL PROCESSING WASTE AND COAL COMBUSTION BY-PRODUCTS BASED PASTE BACKFILL FOR ENHANCED MINING ECONOMICS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Y.P. Chugh; D. Biswas; D. Deb

2002-06-01

This project has successfully demonstrated that the extraction ratio in a room-and-pillar panel at an Illinois mine can be increased from the current value of approximately 56% to about 64%, with backfilling done from the surface upon completion of all mining activities. This was achieved without significant ground control problems due to the increased extraction ratio. The mined-out areas were backfilled from the surface with gob, coal combustion by-products (CCBs), and fine coal processing waste (FCPW)-based paste backfill containing 65%-70% solids to minimize short-term and long-term surface deformations risk. This concept has the potential to increase mine productivity, reduce miningmore » costs, manage large volumes of CCBs beneficially, and improve the miner's health, safety, and environment. Two injection holes were drilled over the demonstration panel to inject the paste backfill. Backfilling was started on August 11, 1999 through the first borehole. About 9,293 tons of paste backfill were injected through this borehole with a maximum flow distance of 300-ft underground. On September 27, 2000, backfilling operation was resumed through the second borehole with a mixture of F ash and FBC ash. A high-speed auger mixer (new technology) was used to mix solids with water. About 6,000 tons of paste backfill were injected underground through this hole. Underground backfilling using the ''Groutnet'' flow model was simulated. Studies indicate that grout flow over 300-foot distance is possible. Approximately 13,000 tons of grout may be pumped through a single hole. The effect of backfilling on the stability of the mine workings was analyzed using SIUPANEL.3D computer program and further verified using finite element analysis techniques. Stiffness of the backfill mix is most critical for enhancing the stability of mine workings. Mine openings do not have to be completely backfilled to enhance their stability. Backfill height of about 50% of the seam height is

Electrical resistivity measurement of mechanically stabilized Earth wall backfill : technical summary.

DOT National Transportation Integrated Search

2016-06-01

In Kansas, mechanically stabilized earth (MSE) retaining walls are typically : backfilled with coarse aggregate. Current backfill material testing procedures used : by the Kansas Department of Transportation (KDOT) utilize on-site observations for : ...

Adaptive Multiscale Modeling of Geochemical Impacts on Fracture Evolution

NASA Astrophysics Data System (ADS)

Molins, S.; Trebotich, D.; Steefel, C. I.; Deng, H.

2016-12-01

Understanding fracture evolution is essential for many subsurface energy applications, including subsurface storage, shale gas production, fracking, CO2 sequestration, and geothermal energy extraction. Geochemical processes in particular play a significant role in the evolution of fractures through dissolution-driven widening, fines migration, and/or fracture sealing due to precipitation. One obstacle to understanding and exploiting geochemical fracture evolution is that it is a multiscale process. However, current geochemical modeling of fractures cannot capture this multi-scale nature of geochemical and mechanical impacts on fracture evolution, and is limited to either a continuum or pore-scale representation. Conventional continuum-scale models treat fractures as preferential flow paths, with their permeability evolving as a function (often, a cubic law) of the fracture aperture. This approach has the limitation that it oversimplifies flow within the fracture in its omission of pore scale effects while also assuming well-mixed conditions. More recently, pore-scale models along with advanced characterization techniques have allowed for accurate simulations of flow and reactive transport within the pore space (Molins et al., 2014, 2015). However, these models, even with high performance computing, are currently limited in their ability to treat tractable domain sizes (Steefel et al., 2013). Thus, there is a critical need to develop an adaptive modeling capability that can account for separate properties and processes, emergent and otherwise, in the fracture and the rock matrix at different spatial scales. Here we present an adaptive modeling capability that treats geochemical impacts on fracture evolution within a single multiscale framework. Model development makes use of the high performance simulation capability, Chombo-Crunch, leveraged by high resolution characterization and experiments. The modeling framework is based on the adaptive capability in Chombo

Electrical resistivity measurement of mechanically stabilized Earth wall backfill : final report.

DOT National Transportation Integrated Search

2016-06-01

In Kansas, mechanically stabilized earth (MSE) retaining walls are typically backfilled with coarse aggregate. : Current backfill material testing procedures used by the Kansas Department of Transportation (KDOT) utilize on-site : observations for co...

Geochemical studies of backfill aggregates, lake sediment cores and the Hueco Bolson Aquifer

NASA Astrophysics Data System (ADS)

Thapalia, Anita

This dissertation comprises of three different researches that focuses on the application of geochemistry from aggregates, lake sediment cores and Hueco Bolson Aquifer. Each study is independent and presented in the publication format. The first chapter is already published and the second chapter is in revision phase. Overall, three studies measure the large scale (field) as well as bench scale (lab) water-rock interactions influenced by the climatic and anthropogenic factors spans from the field of environmental geology to civil engineering. The first chapter of this dissertation addresses the chemical evaluation of coarse aggregates from six different quarries in Texas. The goal of this work is to find out the best geochemical methods for assessing the corrosion potential of coarse aggregates prior to their use in mechanically stabilized earth walls. Electrochemical parameters help to define the corrosion potential of aggregates following two different leaching protocols. Testing the coarse and fine aggregates demonstrate the chemical difference due to size-related kinetic leaching effects. Field fines also show different chemistry than the bulk rock indicating the weathering impact on carbonate rocks. The second chapter investigates zinc (Zn) isotopic signatures from eight lake sediment cores collected both from pristine lakes and those impacted by urban anthropogenic contamination. Zinc from the natural weathering of rocks and anthropogenic atmospheric pollutants are transported to these lakes and the signatures are recorded in the sediments. Isotopic analysis of core samples provides the signature of anthropogenic contamination sources. Dated sediment core and isotopic analysis can identify Zn inputs that are correlated to the landuse and population change of the watersheds. Comparison of isotopic data from both pristine and urban lake sediment core also serves as an analog in other lake sediment cores in the world. The third chapter studies on Hueco Bolson

Deformation Monitoring of Waste-Rock-Backfilled Mining Gob for Ground Control

PubMed Central

Zhao, Tongbin; Zhang, Yubao; Zhang, Zhenyu; Li, Zhanhai; Ma, Shuqi

2017-01-01

Backfill mining is an effective option to mitigate ground subsidence, especially for mining under surface infrastructure, such as buildings, dams, rivers and railways. To evaluate its performance, continual long-term field monitoring of the deformation of backfilled gob is important to satisfy strict public scrutiny. Based on industrial Ethernet, a real-time monitoring system was established to monitor the deformation of waste-rock-backfilled gob at −700 m depth in the Tangshan coal mine, Hebei Province, China. The designed deformation sensors, based on a resistance transducer mechanism, were placed vertically between the roof and floor. Stress sensors were installed above square steel plates that were anchored to the floor strata. Meanwhile, data cables were protected by steel tubes in case of damage. The developed system continually harvested field data for three months. The results show that industrial Ethernet technology can be reliably used for long-term data transmission in complicated underground mining conditions. The monitoring reveals that the roof subsidence of the backfilled gob area can be categorized into four phases. The bearing load of the backfill developed gradually and simultaneously with the deformation of the roof strata, and started to be almost invariable when the mining face passed 97 m. PMID:28475168

Deformation Monitoring of Waste-Rock-Backfilled Mining Gob for Ground Control.

PubMed

Zhao, Tongbin; Zhang, Yubao; Zhang, Zhenyu; Li, Zhanhai; Ma, Shuqi

2017-05-05

Backfill mining is an effective option to mitigate ground subsidence, especially for mining under surface infrastructure, such as buildings, dams, rivers and railways. To evaluate its performance, continual long-term field monitoring of the deformation of backfilled gob is important to satisfy strict public scrutiny. Based on industrial Ethernet, a real-time monitoring system was established to monitor the deformation of waste-rock-backfilled gob at -700 m depth in the Tangshan coal mine, Hebei Province, China. The designed deformation sensors, based on a resistance transducer mechanism, were placed vertically between the roof and floor. Stress sensors were installed above square steel plates that were anchored to the floor strata. Meanwhile, data cables were protected by steel tubes in case of damage. The developed system continually harvested field data for three months. The results show that industrial Ethernet technology can be reliably used for long-term data transmission in complicated underground mining conditions. The monitoring reveals that the roof subsidence of the backfilled gob area can be categorized into four phases. The bearing load of the backfill developed gradually and simultaneously with the deformation of the roof strata, and started to be almost invariable when the mining face passed 97 m.

A modified procedure for mixture-model clustering of regional geochemical data

USGS Publications Warehouse

Ellefsen, Karl J.; Smith, David B.; Horton, John D.

2014-01-01

A modified procedure is proposed for mixture-model clustering of regional-scale geochemical data. The key modification is the robust principal component transformation of the isometric log-ratio transforms of the element concentrations. This principal component transformation and the associated dimension reduction are applied before the data are clustered. The principal advantage of this modification is that it significantly improves the stability of the clustering. The principal disadvantage is that it requires subjective selection of the number of clusters and the number of principal components. To evaluate the efficacy of this modified procedure, it is applied to soil geochemical data that comprise 959 samples from the state of Colorado (USA) for which the concentrations of 44 elements are measured. The distributions of element concentrations that are derived from the mixture model and from the field samples are similar, indicating that the mixture model is a suitable representation of the transformed geochemical data. Each cluster and the associated distributions of the element concentrations are related to specific geologic and anthropogenic features. In this way, mixture model clustering facilitates interpretation of the regional geochemical data.

Geochemical Modeling of Carbon Sequestration, MMV, and EOR in the Illinois Basin

USGS Publications Warehouse

Berger, P.M.; Roy, W.R.; Mehnert, E.

2009-01-01

The Illinois State Geologic Survey is conducting several ongoing CO2 sequestration projects that require geochemical models to gain an understanding of the processes occurring in the subsurface. The ISGS has collected brine and freshwater samples associated with an enhanced oil recovery project in the Loudon oil field. Geochemical modeling allows us to understand reactions with carbonate and silicate minerals in the reservoir, and the effects they have had on brine composition. For the Illinois Basin Decatur project, geochemical models should allow predictions of the reactions that will take place before CO2 injection begins. ?? 2009 Elsevier Ltd. All rights reserved.

Testing of candidate waste-package backfill and canister materials for basalt

NASA Astrophysics Data System (ADS)

Wood, M. I.; Anderson, W. J.; Aden, G. D.

1982-09-01

The Basalt Waste Isolation Project (BWIP) is developing a multiple-barrier waste package to contain high-level nuclear waste as part of an overall system (e.g., waste package, repository sealing system, and host rock) designed to isolate the waste in a repository located in basalt beneath the Hanford Site, Richland, Washington. The three basic components of the waste package are the waste form, the canister, and the backfill. An extensive testing program is under way to determine the chemical, physical, and mechanical properties of potential canister and backfill materials. The data derived from this testing program will be used to recommend those materials that most adequately perform the functions assigned to the canister and backfill.

Backfilling behavior of a mixed aggregate based on construction waste and ultrafine tailings

PubMed Central

Zhang, Qinli; Xiao, Chongchun; Chen, Xin

2017-01-01

To study the possibility of utilizing mixed construction waste and ultrafine tailings (CW&UT) as a backfilling aggregate that can be placed underground in a mine, physicochemical evaluation, proportioning strength tests, and pumpability experiments were conducted. It was revealed that mixed CW&UT can be used as a backfilling aggregate due to the complementarities of their physicochemical properties. In addition, as the results of the proportioning strength tests show, the compressive strength of a cemented CW&UT backfilling specimen cured for 28 days, with a mass fraction of 72–74%, a cement-sand ratio of 1:12, and a CW proportion of 30%, is higher than 1.0 MPa, which meets the safety requirements and economic consideration of backfilling technology in many underground metal mines, and can also be enhanced with an increase in the cement-sand ratio. The results of the pumpability experiments show that cemented backfilling slurry based on CW&UT can be transported to the stope underground with a common filling pump, with a 16.6 MPa maximum pressure, with the condition that the time of emergency shut-down is less than approximately 20 min. All in all, the research to utilize mixed CW&UT as a backfilling aggregate can not only provide a way to dispose of CW&UT but also will bring large economic benefits and can provide constructive guidance for environmental protection. PMID:28662072

Backfilling behavior of a mixed aggregate based on construction waste and ultrafine tailings.

PubMed

Chen, Qiusong; Zhang, Qinli; Xiao, Chongchun; Chen, Xin

2017-01-01

To study the possibility of utilizing mixed construction waste and ultrafine tailings (CW&UT) as a backfilling aggregate that can be placed underground in a mine, physicochemical evaluation, proportioning strength tests, and pumpability experiments were conducted. It was revealed that mixed CW&UT can be used as a backfilling aggregate due to the complementarities of their physicochemical properties. In addition, as the results of the proportioning strength tests show, the compressive strength of a cemented CW&UT backfilling specimen cured for 28 days, with a mass fraction of 72-74%, a cement-sand ratio of 1:12, and a CW proportion of 30%, is higher than 1.0 MPa, which meets the safety requirements and economic consideration of backfilling technology in many underground metal mines, and can also be enhanced with an increase in the cement-sand ratio. The results of the pumpability experiments show that cemented backfilling slurry based on CW&UT can be transported to the stope underground with a common filling pump, with a 16.6 MPa maximum pressure, with the condition that the time of emergency shut-down is less than approximately 20 min. All in all, the research to utilize mixed CW&UT as a backfilling aggregate can not only provide a way to dispose of CW&UT but also will bring large economic benefits and can provide constructive guidance for environmental protection.

Experimental Study on the Coupling Mechanism of Early-strength Backfill and Rock

NASA Astrophysics Data System (ADS)

Wang, Mingxu

2017-11-01

In order to study the interaction mechanism between the ore rock and backfill at the early stage, paraffin is chosen as the cementing agent. Based on the damage mechanics and fractal theory, the interaction mechanism between the ore rock and backfill is characterized by the relevant tests on the complex of proportioned ore rock and backfill with resistance strain gauge, crack propagation, microscopic imaging and AE. The experimental results showed that: 1) Through the axial loading test, compared with the early strength of the cemented filling and paraffin mechanical deformation characteristics, the stress and strain curves of the two had a common linear deformation law, while in the early strength of the filling elastic capacity strong, with a certain degree of resilience. 2) The bearing capacity of the backfill was weak, but the deformation ability was strong. During the bearing process, the deformation of the upper load was mainly caused by the ore rock, which leaded to the damage of the rock. 3) The distribution of AE points during the co-carrying of the filling and the ore rock was monitored by the acoustic emission instrument. The damage occurred mainly in the contact zone between the backfill and the ore rock zone. The corresponding AE point distribution also validated the crack happening.

Evaluating the methodology and performance of jetting and flooding of granular backfill materials.

DOT National Transportation Integrated Search

2014-11-01

Compaction of backfill in confined spaces on highway projects is often performed with small vibratory plates, based : solely on the experience of the contractor, leading to inadequate compaction. As a result, the backfill is prone to : erosion and of...

Hiereachical Bayesian Model for Combining Geochemical and Geophysical Data for Environmental Applications Software

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Jinsong

2013-05-01

Development of a hierarchical Bayesian model to estimate the spatiotemporal distribution of aqueous geochemical parameters associated with in-situ bioremediation using surface spectral induced polarization (SIP) data and borehole geochemical measurements collected during a bioremediation experiment at a uranium-contaminated site near Rifle, Colorado. The SIP data are first inverted for Cole-Cole parameters including chargeability, time constant, resistivity at the DC frequency and dependence factor, at each pixel of two-dimensional grids using a previously developed stochastic method. Correlations between the inverted Cole-Cole parameters and the wellbore-based groundwater chemistry measurements indicative of key metabolic processes within the aquifer (e.g. ferrous iron, sulfate, uranium)more » were established and used as a basis for petrophysical model development. The developed Bayesian model consists of three levels of statistical sub-models: 1) data model, providing links between geochemical and geophysical attributes, 2) process model, describing the spatial and temporal variability of geochemical properties in the subsurface system, and 3) parameter model, describing prior distributions of various parameters and initial conditions. The unknown parameters are estimated using Markov chain Monte Carlo methods. By combining the temporally distributed geochemical data with the spatially distributed geophysical data, we obtain the spatio-temporal distribution of ferrous iron, sulfate and sulfide, and their associated uncertainity information. The obtained results can be used to assess the efficacy of the bioremediation treatment over space and time and to constrain reactive transport models.« less

The Resource Usage Aware Backfilling

NASA Astrophysics Data System (ADS)

Guim, Francesc; Rodero, Ivan; Corbalan, Julita

Job scheduling policies for HPC centers have been extensively studied in the last few years, especially backfilling based policies. Almost all of these studies have been done using simulation tools. All the existent simulators use the runtime (either estimated or real) provided in the workload as a basis of their simulations. In our previous work we analyzed the impact on system performance of considering the resource sharing (memory bandwidth) of running jobs including a new resource model in the Alvio simulator. Based on this studies we proposed the LessConsume and LessConsume Threshold resource selection policies. Both are oriented to reduce the saturation of the shared resources thus increasing the performance of the system. The results showed how both resource allocation policies shown how the performance of the system can be improved by considering where the jobs are finally allocated.

Long-term geochemical evolution of the near field repository: Insights from reactive transport modelling and experimental evidences

NASA Astrophysics Data System (ADS)

Arcos, David; Grandia, Fidel; Domènech, Cristina; Fernández, Ana M.; Villar, María V.; Muurinen, Arto; Carlsson, Torbjörn; Sellin, Patrik; Hernán, Pedro

2008-12-01

The KBS-3 underground nuclear waste repository concept designed by the Swedish Nuclear Fuel and Waste Management Co. (SKB) includes a bentonite buffer barrier surrounding the copper canisters and the iron insert where spent nuclear fuel will be placed. Bentonite is also part of the backfill material used to seal the access and deposition tunnels of the repository. The bentonite barrier has three main safety functions: to ensure the physical stability of the canister, to retard the intrusion of groundwater to the canisters, and in case of canister failure, to retard the migration of radionuclides to the geosphere. Laboratory experiments (< 10 years long) have provided evidence of the control exerted by accessory minerals and clay surfaces on the pore water chemistry. The evolution of the pore water chemistry will be a primordial factor on the long-term stability of the bentonite barrier, which is a key issue in the safety assessments of the KBS-3 concept. In this work we aim to study the long-term geochemical evolution of bentonite and its pore water in the evolving geochemical environment due to climate change. In order to do this, reactive transport simulations are used to predict the interaction between groundwater and bentonite which is simulated following two different pathways: (1) groundwater flow through the backfill in the deposition tunnels, eventually reaching the top of the deposition hole, and (2) direct connection between groundwater and bentonite rings through fractures in the granite crosscutting the deposition hole. The influence of changes in climate has been tested using three different waters interacting with the bentonite: present-day groundwater, water derived from ice melting, and deep-seated brine. Two commercial bentonites have been considered as buffer material, MX-80 and Deponit CA-N, and one natural clay (Friedland type) for the backfill. They show differences in the composition of the exchangeable cations and in the accessory mineral

Long-term geochemical evolution of the near field repository: insights from reactive transport modelling and experimental evidences.

PubMed

Arcos, David; Grandia, Fidel; Domènech, Cristina; Fernández, Ana M; Villar, María V; Muurinen, Arto; Carlsson, Torbjörn; Sellin, Patrik; Hernán, Pedro

2008-12-12

The KBS-3 underground nuclear waste repository concept designed by the Swedish Nuclear Fuel and Waste Management Co. (SKB) includes a bentonite buffer barrier surrounding the copper canisters and the iron insert where spent nuclear fuel will be placed. Bentonite is also part of the backfill material used to seal the access and deposition tunnels of the repository. The bentonite barrier has three main safety functions: to ensure the physical stability of the canister, to retard the intrusion of groundwater to the canisters, and in case of canister failure, to retard the migration of radionuclides to the geosphere. Laboratory experiments (< 10 years long) have provided evidence of the control exerted by accessory minerals and clay surfaces on the pore water chemistry. The evolution of the pore water chemistry will be a primordial factor on the long-term stability of the bentonite barrier, which is a key issue in the safety assessments of the KBS-3 concept. In this work we aim to study the long-term geochemical evolution of bentonite and its pore water in the evolving geochemical environment due to climate change. In order to do this, reactive transport simulations are used to predict the interaction between groundwater and bentonite which is simulated following two different pathways: (1) groundwater flow through the backfill in the deposition tunnels, eventually reaching the top of the deposition hole, and (2) direct connection between groundwater and bentonite rings through fractures in the granite crosscutting the deposition hole. The influence of changes in climate has been tested using three different waters interacting with the bentonite: present-day groundwater, water derived from ice melting, and deep-seated brine. Two commercial bentonites have been considered as buffer material, MX-80 and Deponit CA-N, and one natural clay (Friedland type) for the backfill. They show differences in the composition of the exchangeable cations and in the accessory mineral

Resolving the Multi-scale Behavior of Geochemical Weathering in the Critical Zone Using High Resolution Hydro-geochemical Models

NASA Astrophysics Data System (ADS)

Pandey, S.; Rajaram, H.

2015-12-01

This work investigates hydrologic and geochemical interactions in the Critical Zone (CZ) using high-resolution reactive transport modeling. Reactive transport models can be used to predict the response of geochemical weathering and solute fluxes in the CZ to changes in a dynamic environment, such as those pertaining to human activities and climate change in recent years. The scales of hydrology and geochemistry in the CZ range from days to eons in time and centimeters to kilometers in space. Here, we present results of a multi-dimensional, multi-scale hydro-geochemical model to investigate the role of subsurface heterogeneity on the formation of mineral weathering fronts in the CZ, which requires consideration of many of these spatio-temporal scales. The model is implemented using the reactive transport code PFLOTRAN, an open source subsurface flow and reactive transport code that utilizes parallelization over multiple processing nodes and provides a strong framework for simulating weathering in the CZ. The model is set up to simulate weathering dynamics in the mountainous catchments representative of the Colorado Front Range. Model parameters were constrained based on hydrologic, geochemical, and geophysical observations from the Boulder Creek Critical Zone Observatory (BcCZO). Simulations were performed in fractured rock systems and compared with systems of heterogeneous and homogeneous permeability fields. Tracer simulations revealed that the mean residence time of solutes was drastically accelerated as fracture density increased. In simulations that include mineral reactions, distinct signatures of transport limitations on weathering arose when discrete flow paths were included. This transport limitation was related to both advective and diffusive processes in the highly heterogeneous systems (i.e. fractured media and correlated random permeability fields with σlnk > 3). The well-known time-dependence of mineral weathering rates was found to be the most

Native backfill materials for mechanically stabilized earth walls.

DOT National Transportation Integrated Search

2005-01-01

Mechanically stabilized earth walls are an attractive alternative to conventional reinforced concrete retaining walls. The economy of these walls for non-critical applications might be improved by using alternative backfills consisting of on-site soi...

Fat metaplasia and backfill are key intermediaries in the development of sacroiliac joint ankylosis in patients with ankylosing spondylitis.

PubMed

Maksymowych, Walter P; Wichuk, Stephanie; Chiowchanwisawakit, Praveena; Lambert, Robert G; Pedersen, Susanne J

2014-11-01

Fat metaplasia in bone marrow on T1-weighted magnetic resonance imaging (MRI) scans may develop after resolution of inflammation in patients with ankylosing spondylitis (AS) and may predict new bone formation in the spine. Similar tissue, termed backfill, may also fill areas of excavated bone in the sacroiliac (SI) joints and may reflect resolution of inflammation and tissue repair at sites of erosions. The purpose of this study was to test our hypothesis that SI joint ankylosis develops following repair of erosions and that tissue characterized by fat metaplasia is a key intermediary step in this pathway. We used the Spondyloarthritis Research Consortium of Canada (SPARCC) SI structural lesion score (SSS) method to assess fat metaplasia, erosions, backfill, and ankylosis on MRIs of the SI joints in 147 patients with AS monitored for 2 years. Univariate and multivariate regression analyses focused first on identifying significant MRI predictors of new backfill and fat metaplasia. We then assessed the role of backfill and fat metaplasia in the development of new ankylosis. All analyses were adjusted for demographic features, treatment, and baseline and 2-year change in SSS values for parameters of inflammation and MRI structural lesions. Resolution of inflammation and reduction of erosions were each independently associated with the development of new backfill and fat metaplasia at 2 years on multivariate analyses. Multivariate regression analysis that included demographic features, baseline and 2-year change in parameters of inflammation and MRI structural lesion showed that reduction in erosions (P = 0.0005) and increase in fat metaplasia (P = 0.002) at 2 years was each independently associated with the development of new ankylosis. Our data support a disease model whereby ankylosis develops following repair of erosions, and fat metaplasia and backfill are key intermediary steps in this pathway. Copyright © 2014 by the American College of Rheumatology.

MODELING MONOMETHYLMERCURY AND TRIBUTYLTIN SPECIATION WITH EPA'S GEOCHEMICAL SPECIATION MODEL MINTEQA2

EPA Science Inventory

Given the complexity of the various, simultaneous (and competing) equilibrium reactions governing the speciation of ionic species in aquatic systems, EPA has developed and distributed the geochemical speciation model MINTEQA2 (Brown and Allison, 1987, Allison et al., 1991; Hydrog...

GEOCHEMICAL MODELING OF ARSENIC SPECIATION AND MOBILIZATION: IMPLICATIONS FOR BIOREMEDIATION

EPA Science Inventory

Geochemical modeling techniques were used to examine the biogeochemical linkages between Fe, S, and As in shallow alluvial aquifers. We modeled: 1) the adsorption and desorption of As on the surface of hydrous ferric oxides (HFO’s) in stream beds under aerobic conditions; 2) red...

A novel silica alumina-based backfill material composed of coal refuse and fly ash.

PubMed

Yao, Yuan; Sun, Henghu

2012-04-30

In this paper, a systematic study was conducted to investigate a novel silica alumina-based backfill material composed of coal refuse and fly ash. The coal refuse and fly ash had different properties under various thermal activation temperatures (20 °C, 150 °C, 350 °C, 550 °C, 750 °C and 950 °C). It is known that a thermal activation temperature ranging from 20 °C to 950 °C significantly increases the flowability and pozzolanic properties of the coal refuse; however, the flowability of fly ash decreases when the activation temperature is higher than 550 °C because of a severe agglomeration phenomenon on its surface. An optimal design for this backfill material was determined to include an activated portion composed of 5% coal refuse at 750 °C and 15% fly ash at 20 °C. This combination yields the best performance with excellent flowability, a high compressive strength and a low bleeding rate. The microanalysis results corresponded well with the performance tests at different activation conditions. In the coal refuse, kaolinite peaks began to decrease because of their transformation into metakaolin at 550 °C. Chlorite peaks disappeared at 750 °C. Muscovite peaks decreased at 750 °C and disappeared at 950 °C. During this process, muscovite 2M(1) gradually dehydroxylated to muscovite HT. Furthermore, this paper examined the environmental acceptance and economic feasibility of this technology and found that this silica alumina-based backfill material composed of coal refuse and fly ash not only meets EPA requirements but also has several advantages in industry feasibility when compared with hydraulic backfill, rock backfill and paste backfill. Published by Elsevier B.V.

A COMSOL-GEMS interface for modeling coupled reactive-transport geochemical processes

NASA Astrophysics Data System (ADS)

Azad, Vahid Jafari; Li, Chang; Verba, Circe; Ideker, Jason H.; Isgor, O. Burkan

2016-07-01

An interface was developed between COMSOL MultiphysicsTM finite element analysis software and (geo)chemical modeling platform, GEMS, for the reactive-transport modeling of (geo)chemical processes in variably saturated porous media. The two standalone software packages are managed from the interface that uses a non-iterative operator splitting technique to couple the transport (COMSOL) and reaction (GEMS) processes. The interface allows modeling media with complex chemistry (e.g. cement) using GEMS thermodynamic database formats. Benchmark comparisons show that the developed interface can be used to predict a variety of reactive-transport processes accurately. The full functionality of the interface was demonstrated to model transport processes, governed by extended Nernst-Plank equation, in Class H Portland cement samples in high pressure and temperature autoclaves simulating systems that are used to store captured carbon dioxide (CO2) in geological reservoirs.

Calculation of individual isotope equilibrium constants for implementation in geochemical models

USGS Publications Warehouse

Thorstenson, Donald C.; Parkhurst, David L.

2002-01-01

Theory is derived from the work of Urey to calculate equilibrium constants commonly used in geochemical equilibrium and reaction-transport models for reactions of individual isotopic species. Urey showed that equilibrium constants of isotope exchange reactions for molecules that contain two or more atoms of the same element in equivalent positions are related to isotope fractionation factors by , where is n the number of atoms exchanged. This relation is extended to include species containing multiple isotopes, for example and , and to include the effects of nonideality. The equilibrium constants of the isotope exchange reactions provide a basis for calculating the individual isotope equilibrium constants for the geochemical modeling reactions. The temperature dependence of the individual isotope equilibrium constants can be calculated from the temperature dependence of the fractionation factors. Equilibrium constants are calculated for all species that can be formed from and selected species containing , in the molecules and the ion pairs with where the subscripts g, aq, l, and s refer to gas, aqueous, liquid, and solid, respectively. These equilibrium constants are used in the geochemical model PHREEQC to produce an equilibrium and reaction-transport model that includes these isotopic species. Methods are presented for calculation of the individual isotope equilibrium constants for the asymmetric bicarbonate ion. An example calculates the equilibrium of multiple isotopes among multiple species and phases.

A new statistical model to find bedrock, a prequel to geochemical mass balance

NASA Astrophysics Data System (ADS)

Fisher, B.; Rendahl, A. K.; Aufdenkampe, A. K.; Yoo, K.

2016-12-01

We present a new statistical model to assess weathering trends in deep weathering profiles. The Weathering Trends (WT) model is presented as an extension of the geochemical mass balance model (Brimhall & Dietrich, 1987), and is available as an open-source R library on GitHub (https://github.com/AaronRendahl/WeatheringTrends). WT uses element concentration data to determine the depth to fresh bedrock by assessing the maximum extent of weathering for all elements and the model applies confidence intervals on the depth to bedrock. WT models near-surface features and the shape of the weathering profile using a log transformation of data to capture the magnitude of changes that are relevant to geochemical kinetics and thermodynamics. The WT model offers a new, enhanced opportunity to characterize and understand biogeochemical weathering in heterogeneous rock types. We apply the model to two 21-meter drill cores in the Laurels Schist bedrock in the Christina River Basin Critical Zone Observatory in the Pennsylvania Piedmont. The Laurels Schist had inconclusive weathering indicators prior to development and application of WT model. The model differentiated between rock variability and weathering to delineate the maximum extent of weathering at 12.3 (CI 95% [9.2, 21.3]) meters in Ridge Well 1 and 7.2 (CI 95% [4.3, 13.0]) meters in Interfluve Well 2. The modeled extent to weathering is decoupled from the water table at the ridge, but coincides with the water table at the interfluve. These depths were applied as the parent material for the geochemical mass balance for the Laurels Schist. We test statistical approaches to assess the variability and correlation of immobile elements to facilitate the selection of the best immobile element for use in both models. We apply the model to other published data where the geochemical mass balance was applied, to demonstrate how the WT model provides additional information about weathering depth and weathering trends.

30 CFR 816.106 - Backfilling and grading: Previously mined areas.

Code of Federal Regulations, 2010 CFR

2010-07-01

... operation shall be included within the permit area. (2) The backfill shall be graded to a slope which is compatible with the approved postmining land use and which provides adequate drainage and long-term stability...

30 CFR 817.106 - Backfilling and grading: Previously mined areas.

Code of Federal Regulations, 2010 CFR

2010-07-01

... operation shall be included within the permit area. (2) The backfill shall be graded to a slope which is compatible with the approved postmining land use and which provides adequate drainage and long-term stability...

Manual hierarchical clustering of regional geochemical data using a Bayesian finite mixture model

USGS Publications Warehouse

Ellefsen, Karl J.; Smith, David

2016-01-01

Interpretation of regional scale, multivariate geochemical data is aided by a statistical technique called “clustering.” We investigate a particular clustering procedure by applying it to geochemical data collected in the State of Colorado, United States of America. The clustering procedure partitions the field samples for the entire survey area into two clusters. The field samples in each cluster are partitioned again to create two subclusters, and so on. This manual procedure generates a hierarchy of clusters, and the different levels of the hierarchy show geochemical and geological processes occurring at different spatial scales. Although there are many different clustering methods, we use Bayesian finite mixture modeling with two probability distributions, which yields two clusters. The model parameters are estimated with Hamiltonian Monte Carlo sampling of the posterior probability density function, which usually has multiple modes. Each mode has its own set of model parameters; each set is checked to ensure that it is consistent both with the data and with independent geologic knowledge. The set of model parameters that is most consistent with the independent geologic knowledge is selected for detailed interpretation and partitioning of the field samples.

30 CFR 819.19 - Auger mining: Backfilling and grading.

Code of Federal Regulations, 2014 CFR

2014-07-01

... health and safety or to the environment. ... of the highwall shall be stable and not pose a hazard to the public health and safety or to the... safety factor for the stability of the backfill of at least 1.3. (2) All spoil generated by the auger...

30 CFR 819.19 - Auger mining: Backfilling and grading.

Code of Federal Regulations, 2013 CFR

2013-07-01

... health and safety or to the environment. ... of the highwall shall be stable and not pose a hazard to the public health and safety or to the... safety factor for the stability of the backfill of at least 1.3. (2) All spoil generated by the auger...

Understanding the Alteration of Bentonite Backfill Using Coupled THMC Modeling for a Long Term Heater Test at the Grimsel Underground Research Lab

NASA Astrophysics Data System (ADS)

Birkholzer, J. T.; Zheng, L.; Xu, H.; Rutqvist, J.

2017-12-01

Compacted bentonite is commonly used as backfill material in emplacement tunnels of nuclear waste repositories because of its low permeability, high swelling pressure, and retardation capacity of radionuclide. To assess whether this backfill material can maintain these favorable features when undergoing heating from the waste package and hydration from the host rock, we need a thorough understanding of the thermal, hydrological, mechanical, and chemical evolution of bentonite under disposal conditions. Dedicated field tests integrated with THMC modeling provide an effective way to deepen such understanding. Here, we present coupled THMC models for an in situ heater test which was conducted at the Grimsel Test Site in Switzerland for 18 years. The comprehensive monitoring data obtained in the test provide a unique opportunity to evaluate bentonite integrity and test coupled THMC models. We developed a modeling strategy where conceptual model complexity is increased gradually by adding/testing processes such as Non-Darcian flow, enhanced vapor diffusion, thermal osmosis and different constitutive relationships for permeability/porosity changes due to swelling. The final THMC model explains well all the THM data and the concentration profiles of conservative chemical species. Over the course of modeling the in situ test, we learned that (1) including Non-Darcian flow into the model leads to a significant underestimation of hydration rate of bentonite, (2) chemical data provide an important additional piece of information for calibrating a THM model; (3) key processes needed to reproduce the data include vapor diffusion, as well as porosity and permeability changes due to swelling and thermal osmosis; (4) the concentration profiles of cations (calcium, potassium, magnesium and sodium) were largely shaped by transport processes despite their concentration levels being affected by mineral dissolution/precipitation and cation exchange. The concentration profiles of p

The Study on Development of Light-Weight Foamed Mortar for Tunnel Backfill

NASA Astrophysics Data System (ADS)

Ma, Sang-Joon; Kang, Eun-Gu; Kim, Dong-Min

This study was intended to develop the Light-Weight Foamed Mortar which is used for NATM Composite lining backfill. In the wake of the study, the mixing method which satisfies the requirements for compressive strength, permeability coefficient, fluidity, specific gravity and settlement was developed and moreover field applicability was verified through the model test. Thus the mixing of Light-Weight Foamed Mortar developed in this study is expected to be applicable to NATM Composite lining, thereby making commitment to improving the stability and drainage performance of lining.

Selected Geochemical Data for Modeling Near-Surface Processes in Mineral Systems

USGS Publications Warehouse

Giles, Stuart A.; Granitto, Matthew; Eppinger, Robert G.

2009-01-01

The database herein was initiated, designed, and populated to collect and integrate geochemical, geologic, and mineral deposit data in an organized manner to facilitate geoenvironmental mineral deposit modeling. The Microsoft Access database contains data on a variety of mineral deposit types that have variable environmental effects when exposed at the ground surface by mining or natural processes. The data tables describe quantitative and qualitative geochemical analyses determined by 134 analytical laboratory and field methods for over 11,000 heavy-mineral concentrate, rock, sediment, soil, vegetation, and water samples. The database also provides geographic information on geology, climate, ecoregion, and site contamination levels for over 3,000 field sites in North America.

Roadway backfill method to prevent geohazards induced by room and pillar mining: a case study in Changxing coal mine, China

NASA Astrophysics Data System (ADS)

Zhou, Nan; Li, Meng; Zhang, Jixiong; Gao, Rui

2016-11-01

Coal mines in the western areas of China experience low mining rates and induce many geohazards when using the room and pillar mining method. In this research, we proposed a roadway backfill method during longwall mining to target these problems. We tested the mechanical properties of the backfill materials to determine a reasonable ratio of backfill materials for the driving roadway during longwall mining. We also introduced the roadway layout and the backfill mining technique required for this method. Based on the effects of the abutment stress from a single roadway driving task, we designed the distance between roadways and a driving and filling sequence for multiple-roadway driving. By doing so, we found the movement characteristics of the strata with quadratic stabilization for backfill mining during roadway driving. Based on this research, the driving and filling sequence of the 3101 working face in Changxing coal mine was optimized to avoid the superimposed influence of mining-induced stress. According to the analysis of the surface monitoring data, the accumulated maximum subsidence is 15 mm and the maximum horizontal deformation is 0.8 mm m-1, which indicated that the ground basically had no obvious deformation after the implementation of the roadway backfill method at 3101 working face.

Backfill composition for secondary barriers in nuclear waste repositories

DOEpatents

Beall, Gary W.; Allard, Bert M.

1982-01-01

A backfill composition for sorbing and retaining hazardous elements of nuclear wastes comprises 50-70% by weight of quartz, 10-30% by weight of montmorillonite, 1-10% by weight of phosphate mineral, 1-10% by weight of ferrous mineral, 1-10% by weight of sulfate mineral and 1-10% by weight of attapulgite.

A Geochemical Reaction Model for Titration of Contaminated Soil and Groundwater at the Oak Ridge Reservation

NASA Astrophysics Data System (ADS)

Zhang, F.; Parker, J. C.; Gu, B.; Luo, W.; Brooks, S. C.; Spalding, B. P.; Jardine, P. M.; Watson, D. B.

2007-12-01

This study investigates geochemical reactions during titration of contaminated soil and groundwater at the Oak Ridge Reservation in eastern Tennessee. The soils and groundwater exhibits low pH and high concentrations of aluminum, calcium, magnesium, manganese, various trace metals such as nickel and cobalt, and radionuclides such as uranium and technetium. The mobility of many of the contaminant species diminishes with increasing pH. However, base additions to increase pH are strongly buffered by various precipitation/dissolution and adsorption/desorption reactions. The ability to predict acid-base behavior and associated geochemical effects is thus critical to evaluate remediation performance of pH manipulation strategies. This study was undertaken to develop a practical but generally applicable geochemical model to predict aqueous and solid-phase speciation during soil and groundwater titration. To model titration in the presence of aquifer solids, an approach proposed by Spalding and Spalding (2001) was utilized, which treats aquifer solids as a polyprotic acid. Previous studies have shown that Fe and Al-oxyhydroxides strongly sorb dissolved Ni, U and Tc species. In this study, since the total Fe concentration is much smaller than that of Al, only ion exchange reactions associated with Al hydroxides are considered. An equilibrium reaction model that includes aqueous complexation, precipitation, ion exchange, and soil buffering reactions was developed and implemented in the code HydroGeoChem 5.0 (HGC5). Comparison of model results with experimental titration curves for contaminated groundwater alone and for soil- water systems indicated close agreement. This study is expected to facilitate field-scale modeling of geochemical processes under conditions with highly variable pH to develop practical methods to control contaminant mobility at geochemically complex sites.

Evacuate and backfill apparatus and method

DOEpatents

Oakley, David J.; Groves, Oliver J.

1985-01-01

An apparatus and method for treatment of hollow articles by evacuating existing gas or gases therefrom and purging or backfilling the articles with a second gas such as helium. The apparatus includes a sealed enclosure having an article storage drum mounted therein. A multiplicity of such articles are fed singly into the enclosure and loaded into radial slots formed in the drum. The enclosure is successively evacuated and purged with helium to replace the existing gas in the articles with helium. The purged articles are then discharged singly from the drum and transported out of the enclosure.

Evacuate and backfill apparatus and method

DOEpatents

Oakley, D.J.; Groves, O.J.

1984-06-27

An apparatus and method as described for treatment of hollow articles by evacuating existing gas or gases therefrom and purging or backfilling the articles with a second gas such as helium. The apparatus includes a sealed enclosure having an article storage drum mounted therein. A multiplicity of such articles are fed singly into the enclosure and loaded into radial slots formed in the drum. The enclosure is successively evacuated and purged with helium to replace the existing gas in the articles with helium. The purged articles are then discharged singly from the drum and transported out of the enclosure.

Backfill composition for secondary barriers in nuclear waste repositories

DOEpatents

Beall, G.W.; Allard, B.M.

1980-05-30

A backfill composition for sorbing and retaining hazardous elements of nuclear wastes comprises 50 to 70% by weight of quartz, 10 to 30% by weight of montmorillonite, 1 to 10% by weight of phosphate mineral, 1 to 10% by weight of ferrous mineral, 1 to 10% by weight of sulfate mineral and 1 to 10% by weight of attapulgite.

Numerical analysis of dense narrow backfills for increasing lateral passive resistance.

DOT National Transportation Integrated Search

2010-08-01

Previously, full-scale lateral load tests conducted on pile caps with different aspect ratios showed that placement : of a narrow, dense backfill zone against the cap could substantially increase the passive resistance. The objective : of this study ...

Geochemical Constraints for Mercury's PCA-Derived Geochemical Terranes

NASA Astrophysics Data System (ADS)

Stockstill-Cahill, K. R.; Peplowski, P. N.

2018-05-01

PCA-derived geochemical terranes provide a robust, analytical means of defining these terranes using strictly geochemical inputs. Using the end members derived in this way, we are able to assess the geochemical implications for Mercury.

Radon emanation from backfilled mill tailings in underground uranium mine.

PubMed

Sahu, Patitapaban; Mishra, Devi Prasad; Panigrahi, Durga Charan; Jha, Vivekananda; Patnaik, R Lokeswara; Sethy, Narendra Kumar

2014-04-01

Coarser mill tailings used as backfill to stabilize the stoped out areas in underground uranium mines is a potential source of radon contamination. This paper presents the quantitative assessment of radon emanation from the backfilled tailings in Jaduguda mine, India using a cylindrical accumulator. Some of the important parameters such as (226)Ra activity concentration, bulk density, bulk porosity, moisture content and radon emanation factor of the tailings affecting radon emanation were determined in the laboratory. The study revealed that the radon emanation rate of the tailings varied in the range of 0.12-7.03 Bq m(-2) s(-1) with geometric mean of 1.01 Bq m(-2) s(-1) and geometric standard deviation of 3.39. An increase in radon emanation rate was noticed up to a moisture saturation of 0.09 in the tailings, after which the emanation rate gradually started declining with saturation due to low diffusion coefficient of radon in the saturated tailings. Radon emanation factor of the tailings varied in the range of 0.08-0.23 with the mean value of 0.21. The emanation factor of the tailings with moisture saturation level over 0.09 was found to be about three times higher than that of the absolutely dry tailings. The empirical relationship obtained between (222)Rn emanation rate and (226)Ra activity concentration of the tailings indicated a significant positive linear correlation (r = 0.95, p < 0.001). This relationship may be useful for quick prediction of radon emanation rate from the backfill material of similar nature. Copyright © 2014 Elsevier Ltd. All rights reserved.

30 CFR 717.14 - Backfilling and grading of road cuts, mine entry area cuts, and other surface work areas.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Backfilling and grading of road cuts, mine entry area cuts, and other surface work areas. 717.14 Section 717.14 Mineral Resources OFFICE OF SURFACE... MINING GENERAL PERFORMANCE STANDARDS § 717.14 Backfilling and grading of road cuts, mine entry area cuts...

Assessment of (222)Rn emanation from ore body and backfill tailings in low-grade underground uranium mine.

PubMed

Mishra, Devi Prasad; Sahu, Patitapaban; Panigrahi, Durga Charan; Jha, Vivekanand; Patnaik, R Lokeswara

2014-02-01

This paper presents a comparative study of (222)Rn emanation from the ore and backfill tailings in an underground uranium mine located at Jaduguda, India. The effects of surface area, porosity, (226)Ra and moisture contents on (222)Rn emanation rate were examined. The study revealed that the bulk porosity of backfill tailings is more than two orders of magnitude than that of the ore. The geometric mean radon emanation rates from the ore body and backfill tailings were found to be 10.01 × 10(-3) and 1.03 Bq m(-2) s(-1), respectively. Significant positive linear correlations between (222)Rn emanation rate and the (226)Ra content of ore and tailings were observed. For normalised (226)Ra content, the (222)Rn emanation rate from tailings was found to be 283 times higher than the ore due to higher bulk porosity and surface area. The relative radon emanation from the tailings with moisture fraction of 0.14 was found to be 2.4 times higher than the oven-dried tailings. The study suggested that the mill tailings used as a backfill material significantly contributes to radon emanation as compared to the ore body itself and the (226)Ra content and bulk porosity are the dominant factors for radon emanation into the mine atmosphere.

Probabilistic, sediment-geochemical parameterisation of the groundwater compartment of the Netherlands for spatially distributed, reactive transport modelling

NASA Astrophysics Data System (ADS)

Janssen, Gijs; Gunnink, Jan; van Vliet, Marielle; Goldberg, Tanya; Griffioen, Jasper

2017-04-01

Pollution of groundwater aquifers with contaminants as nitrate is a common problem. Reactive transport models are useful to predict the fate of such contaminants and to characterise the efficiency of mitigating or preventive measures. Parameterisation of a groundwater transport model on reaction capacity is a necessary step during building the model. Two Dutch, national programs are combined to establish a methodology for building a probabilistic model on reaction capacity of the groundwater compartment at the national scale: the Geological Survey program and the NHI Netherlands Hydrological Instrument program. Reaction capacity is considered as a series of geochemical characteristics that control acid/base condition, redox condition and sorption capacity. Five primary reaction capacity variables are characterised: 1. pyrite, 2. non-pyrite, reactive iron (oxides, siderite and glauconite), 3. clay fraction, 4. organic matter and 5. Ca-carbonate. Important reaction capacity variables that are determined by more than one solid compound are also deduced: 1. potential reduction capacity (PRC) by pyrite and organic matter, 2. cation-exchange capacity (CEC) by organic matter and clay content, 3. carbonate buffering upon pyrite oxidation (CPBO) by carbonate and pyrite. Statistical properties of these variables are established based on c. 16,000 sediment geochemical analyses. The first tens of meters are characterised based on 25 regions using combinations of lithological class and geological formation as strata. Because of both less data and more geochemical uniformity, the deeper subsurface is characterised in a similar way based on 3 regions. The statistical data is used as input in an algoritm that probabilistically calculates the reaction capacity per grid cell. First, the cumulative frequency distribution (cfd) functions are calculated from the statistical data for the geochemical strata. Second, all voxel cells are classified into the geochemical strata. Third, the

Delineation of geochemical anomalies based on stream sediment data utilizing fractal modeling and staged factor analysis

NASA Astrophysics Data System (ADS)

Afzal, Peyman; Mirzaei, Misagh; Yousefi, Mahyar; Adib, Ahmad; Khalajmasoumi, Masoumeh; Zarifi, Afshar Zia; Foster, Patrick; Yasrebi, Amir Bijan

2016-07-01

Recognition of significant geochemical signatures and separation of geochemical anomalies from background are critical issues in interpretation of stream sediment data to define exploration targets. In this paper, we used staged factor analysis in conjunction with the concentration-number (C-N) fractal model to generate exploration targets for prospecting Cr and Fe mineralization in Balvard area, SE Iran. The results show coexistence of derived multi-element geochemical signatures of the deposit-type sought and ultramafic-mafic rocks in the NE and northern parts of the study area indicating significant chromite and iron ore prospects. In this regard, application of staged factor analysis and fractal modeling resulted in recognition of significant multi-element signatures that have a high spatial association with host lithological units of the deposit-type sought, and therefore, the generated targets are reliable for further prospecting of the deposit in the study area.

30 CFR 816.101 - Backfilling and grading: Time and distance requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... provided in paragraph (b) of this section, rough backfilling and grading for surface mining activities... not more than four spoil ridges behind the pit being worked, the spoil from the active pit constituting the first ridge; or (3) Other surface mining methods. In accordance with the schedule established...

30 CFR 816.101 - Backfilling and grading: Time and distance requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... provided in paragraph (b) of this section, rough backfilling and grading for surface mining activities... not more than four spoil ridges behind the pit being worked, the spoil from the active pit constituting the first ridge; or (3) Other surface mining methods. In accordance with the schedule established...

Retardation of uranium and thorium by a cementitious backfill developed for radioactive waste disposal.

PubMed

Felipe-Sotelo, M; Hinchliff, J; Field, L P; Milodowski, A E; Preedy, O; Read, D

2017-07-01

The solubility of uranium and thorium has been measured under the conditions anticipated in a cementitious, geological disposal facility for low and intermediate level radioactive waste. Similar solubilities were obtained for thorium in all media, comprising NaOH, Ca(OH) 2 and water equilibrated with a cement designed as repository backfill (NRVB, Nirex Reference Vault Backfill). In contrast, the solubility of U(VI) was one order of magnitude higher in NaOH than in the remaining solutions. The presence of cellulose degradation products (CDP) results in a comparable solubility increase for both elements. Extended X-ray Absorption Fine Structure (EXAFS) data suggest that the solubility-limiting phase for uranium corresponds to a becquerelite-type solid whereas thermodynamic modelling predicts a poorly crystalline, hydrated calcium uranate phase. The solubility-limiting phase for thorium was ThO 2 of intermediate crystallinity. No breakthrough of either uranium or thorium was observed in diffusion experiments involving NRVB after three years. Nevertheless, backscattering electron microscopy and microfocus X-ray fluorescence confirmed that uranium had penetrated about 40 μm into the cement, implying active diffusion governed by slow dissolution-precipitation kinetics. Precise identification of the uranium solid proved difficult, displaying characteristics of both calcium uranate and becquerelite. Copyright © 2017 Elsevier Ltd. All rights reserved.

Use of fly-ash slurry in backfill grouting in coal mines.

PubMed

Jiang, Ning; Zhao, Jinhai; Sun, Xizhen; Bai, Liyang; Wang, Changxiang

2017-11-01

Cave backfill grouting implies grouting of the caving rock mass prior to it being compacted. The filling materials strengthen the caving rock and support the overlying strata to achieve the purpose of slowing down the surface subsidence. The broken roof will fail and collapse during mining operations performed without appropriate supporting measures being taken. It is difficult to perform continuous backfill mining on the working face of such roofs using the existing mining technology. In order to solve the above problems, fly ash and mine water are considered as filling materials, and flow characteristics of fly-ash slurry are investigated through laboratory experiments and theoretical analyses. Laws governing the diffusion of fly-ash slurry in the void of caving rock masses and in the void between a caving rock mass and a basic roof are obtained and verified. Based on the results obtained from the above analyses and actual conditions at the Zhaoguan coal mine, Shandong Province, China, a cave backfill grouting system of the hauling pipeline is developed and successfully tested at the 1703 working face in the Zhaoguan coal mine. The results demonstrate that a filling rate of 43.46% is achieved, and the surface subsidence coefficient of the grouting process is found to be 0.475. Compared to the total caving method, the proposed system is found to achieve a reduction rate of 40.63%. This effectively helps in lowering the value of the surface subsidence coefficient. Fly ash and mine water, considered as primary materials in this study, also play a significant role in improving the air quality and water environment.

Geochemical modeling of iron, sulfur, oxygen and carbon in a coastal plain aquifer

NASA Astrophysics Data System (ADS)

Brown, C. J.; Schoonen, M. A. A.; Candela, J. L.

2000-11-01

Fe(III) reduction in the Magothy aquifer of Long Island, NY, results in high dissolved-iron concentrations that degrade water quality. Geochemical modeling was used to constrain iron-related geochemical processes and redox zonation along a flow path. The observed increase in dissolved inorganic carbon is consistent with the oxidation of sedimentary organic matter coupled to the reduction of O 2 and SO 42- in the aerobic zone, and to the reduction of SO 42- in the anaerobic zone; estimated rates of CO 2 production through reduction of Fe(III) were relatively minor by comparison. The rates of CO 2 production calculated from dissolved inorganic carbon mass transfer (2.55×10 -4 to 48.6×10 -4 mmol l -1 yr-1) generally were comparable to the calculated rates of CO 2 production by the combined reduction of O 2, Fe(III) and SO 42- (1.31×10 -4 to 15×10 -4 mmol l -1 yr-1). The overall increase in SO 42- concentrations along the flow path, together with the results of mass-balance calculations, and variations in δ34S values along the flow path indicate that SO 42- loss through microbial reduction is exceeded by SO 42- gain through diffusion from sediments and through the oxidation of FeS 2. Geochemical and microbial data on cores indicate that Fe(III) oxyhydroxide coatings on sediment grains in local, organic carbon- and SO 42--rich zones have been depleted by microbial reduction and resulted in localized SO 42--reducing zones in which the formation of iron disulfides decreases dissolved iron concentrations. These localized zones of SO 42- reduction, which are important for assessing zones of low dissolved iron for water-supply development, could be overlooked by aquifer studies that rely only on groundwater data from well-water samples for geochemical modeling.

Modules based on the geochemical model PHREEQC for use in scripting and programming languages

USGS Publications Warehouse

Charlton, Scott R.; Parkhurst, David L.

2011-01-01

The geochemical model PHREEQC is capable of simulating a wide range of equilibrium reactions between water and minerals, ion exchangers, surface complexes, solid solutions, and gases. It also has a general kinetic formulation that allows modeling of nonequilibrium mineral dissolution and precipitation, microbial reactions, decomposition of organic compounds, and other kinetic reactions. To facilitate use of these reaction capabilities in scripting languages and other models, PHREEQC has been implemented in modules that easily interface with other software. A Microsoft COM (component object model) has been implemented, which allows PHREEQC to be used by any software that can interface with a COM server—for example, Excel®, Visual Basic®, Python, or MATLAB". PHREEQC has been converted to a C++ class, which can be included in programs written in C++. The class also has been compiled in libraries for Linux and Windows that allow PHREEQC to be called from C++, C, and Fortran. A limited set of methods implements the full reaction capabilities of PHREEQC for each module. Input methods use strings or files to define reaction calculations in exactly the same formats used by PHREEQC. Output methods provide a table of user-selected model results, such as concentrations, activities, saturation indices, and densities. The PHREEQC module can add geochemical reaction capabilities to surface-water, groundwater, and watershed transport models. It is possible to store and manipulate solution compositions and reaction information for many cells within the module. In addition, the object-oriented nature of the PHREEQC modules simplifies implementation of parallel processing for reactive-transport models. The PHREEQC COM module may be used in scripting languages to fit parameters; to plot PHREEQC results for field, laboratory, or theoretical investigations; or to develop new models that include simple or complex geochemical calculations.

Modules based on the geochemical model PHREEQC for use in scripting and programming languages

USGS Publications Warehouse

Charlton, S.R.; Parkhurst, D.L.

2011-01-01

The geochemical model PHREEQC is capable of simulating a wide range of equilibrium reactions between water and minerals, ion exchangers, surface complexes, solid solutions, and gases. It also has a general kinetic formulation that allows modeling of nonequilibrium mineral dissolution and precipitation, microbial reactions, decomposition of organic compounds, and other kinetic reactions. To facilitate use of these reaction capabilities in scripting languages and other models, PHREEQC has been implemented in modules that easily interface with other software. A Microsoft COM (component object model) has been implemented, which allows PHREEQC to be used by any software that can interface with a COM server-for example, Excel??, Visual Basic??, Python, or MATLAB??. PHREEQC has been converted to a C++ class, which can be included in programs written in C++. The class also has been compiled in libraries for Linux and Windows that allow PHREEQC to be called from C++, C, and Fortran. A limited set of methods implements the full reaction capabilities of PHREEQC for each module. Input methods use strings or files to define reaction calculations in exactly the same formats used by PHREEQC. Output methods provide a table of user-selected model results, such as concentrations, activities, saturation indices, and densities. The PHREEQC module can add geochemical reaction capabilities to surface-water, groundwater, and watershed transport models. It is possible to store and manipulate solution compositions and reaction information for many cells within the module. In addition, the object-oriented nature of the PHREEQC modules simplifies implementation of parallel processing for reactive-transport models. The PHREEQC COM module may be used in scripting languages to fit parameters; to plot PHREEQC results for field, laboratory, or theoretical investigations; or to develop new models that include simple or complex geochemical calculations. ?? 2011.

Investigation of Flash Fill{reg_sign} as a thermal backfill material

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ayers, P.H.; Charlton, C.B.; Frishette, C.W.

1995-09-01

Flash Fill{reg_sign} was created as a fast-setting, flowable backfill material made entirely from coal combustion by-products and water. Its quick-setting, self-leveling, self-compacting characteristics makes trench road repairs faster, easier, and more economical. Other uses include building foundations, fill around pipes, gas lines, and manholes, and replacement of weak subgrade beneath rooters. Flash Fill can be hand-excavated without the use of power assisted tools or machinery. To enhance thermal resistivity, the original Flash Fill mix was modified to include concrete sand. This resulted in a new Flash Fill, designated FSAND, with all of the aforementioned desirable characteristics of Flash Fill andmore » a thermal resistivity of approximately 50{degree} C-cm/watt. Thermal resistivity tests using conventional laboratory thermal probes, high-current thermal tests, and moisture migration tests have been performed to determine the properties of FSAND. As a result of these tests, FSAND has been approved for use as power cable thermal backfill on all AEP System distribution projects.« less

The Geochemical Earth Reference Model (GERM)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Staudigel, H.; Albarede, F.; Shaw, H.

The Geochemical Earth Reference Model (GERM) initiative is a grass- roots effort with the goal of establishing a community consensus on a chemical characterization of the Earth, its major reservoirs, and the fluxes between them. Long term goal of GERM is a chemical reservoir characterization analogous to the geophysical effort of the Preliminary Reference Earth Model (PREM). Chemical fluxes between reservoirs are included into GERM to illuminate the long-term chemical evolution of the Earth and to characterize the Earth as a dynamic chemical system. In turn, these fluxes control geological processes and influence hydrosphere-atmosphere-climate dynamics. While these long-term goals aremore » clearly the focus of GERM, the process of establishing GERM itself is just as important as its ultimate goal. The GERM initiative is developed in an open community discussion on the World Wide Web (GERM home page is at http://www-ep.es.llnl. gov/germ/germ-home.html) that is mediated by a series of editors with responsibilities for distinct reservoirs and fluxes. Beginning with the original workshop in Lyons (March 1996) GERM is continued to be developed on the Internet, punctuated by workshops and special sessions at professional meetings. It is planned to complete the first model by mid-1997, followed by a call for papers for a February 1998 GERM conference in La Jolla, California.« less

A Quantitative Geochemical Target for Modeling the Formation of the Earth and Moon

NASA Technical Reports Server (NTRS)

Boyce, Jeremy W.; Barnes, Jessica J.; McCubbin, Francis M.

2017-01-01

The past decade has been one of geochemical, isotopic, and computational advances that are bringing the laboratory measurements and computational modeling neighborhoods of the Earth-Moon community to ever closer proximity. We are now however in the position to become even better neighbors: modelers can generate testable hypthotheses for geochemists; and geochemists can provide quantitive targets for modelers. Here we present a robust example of the latter based on Cl isotope measurements of mare basalts.

The effect of various backfilling techniques on the fracture resistance of simulated immature teeth performed apical plug with Biodentine.

PubMed

Topçuoğlu, Hüseyin Sinan; Kesim, Bertan; Düzgün, Salih; Tuncay, Öznur; Demirbuga, Sezer; Topçuoğlu, Gamze

2015-07-01

To evaluate the fracture resistance of simulated immature teeth that had been backfilled using different materials after using Biodentine as the apical plug material. Seventy-five single-rooted teeth were divided into five groups (n = 15). The 15 teeth in group 1 served as a negative control group and received no treatment. The remaining 60 teeth were instrumented to a #6 Peeso reamer to obtain a standard internal diameter of 1.5 mm. The apical 4 mm of 60 teeth was filled with Biodentine. The backfilling was then performed on each group as follows: group 2--no backfilling (positive control), group 3--gutta-percha, group 4--fiber post, and group 5--Biodentine. Specimens were then subjected to fracture testing. The force required to fracture each specimen was recorded, and the data were statistically analyzed. The mean fracture values of groups 1 and 4 were significantly higher than groups 2, 3, and 5 (P < 0.05). The values of groups 3 and 5 were significantly higher than group 2 (P < 0.05). The backfilling with fiber post after an apical Biodentine plug provided the highest fracture resistance among all experimental groups. © 2014 BSPD, IAPD and John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Using multifractal modeling as a standard tool in geochemical exploration for predicting mineralized areas

NASA Astrophysics Data System (ADS)

Gonçalves, Mario A.

2015-04-01

It has been 20 years since the pioneering work of Cheng et al (1994) first proposed a quantitative relationship for the areas enclosing concentration values of an element above given thresholds and their distribution in the field, known as concentration-area (CA) method, which is based in multifractal theory. The method allows the definition of geochemical anomalies in wide set of geological backgrounds but it took nearly 15 years before it became a widely used methodology for mineral exploration. The method was also extended to 1D and 3D data sets. It is worth noting the variety of methods that spanned from the theory of fractals. Building on previous models, including multiplicative cascades and size-grade relationships, increasing evidence points to the powerful tools of fractal theory to describe and model ore deposit distribution and formation. However, while much of these approaches become complex and not easy to use, the CA method is remarkable for its utter simplicity and disarming results obtained when confronted with the geological reality in the field. This is most valued by companies and professionals undertaking geochemical exploration surveys for the characterization or refining of potential ore targets or known mineralized areas. Several approaches have combined the CA method with geostatistic modeling and simulation and other established statistical techniques in order to enhance anomalous threshold identification. Examples are not restricted to geochemical exploration alone, other applications being studies on environmental change. Some of these examples will be addressed as they have been applied to different regions in the world, but particular emphasis will be put on geochemical exploration surveys in different geotectonic units of the Variscan basement in the Iberian Peninsula. These include quartz-vein gold mineralization in Northern Portugal and several surveys for base metals over two wide areas, which served to re-evaluate much of the

Application of mine water leaching protocol on coal fly ash to assess leaching characteristics for suitability as a mine backfill material.

PubMed

Madzivire, Godfrey; Ramasenya, Koena; Tlowana, Supi; Coetzee, Henk; Vadapalli, Viswanath R K

2018-04-16

Over the years, coal mining in the Mpumalanga Province of South Africa has negatively affected the environment by causing pollution of water resources, land subsidence and spontaneous coal combustion. Previous studies show that in-situ treatment of acid mine drainage (AMD) using coal fly ash (CFA) from local power stations was possible and sludge recovered out of such treatment can be used to backfill mines. In this article, the authors have attempted to understand the leaching characteristics of CFA when placed underground as a backfill material using the mine water leaching protocol (MWLP). The results show that the migration of contaminants between the coal fly ash and the AMD in the mine voids depends on the pH and quality of the mine water. While backfilling mine voids with CFA can neutralize and scavenge between 50% and 95% of certain environmentally sensitive elements from AMD such as Fe, Al, Zn, Cu, Ni, Co and Mn. At this moment, it is also important to point out that certain scavenged/removed contaminants from the AMD during initial phases of backfilling can be remobilized by the influx of acidic water into the mine voids. It has therefore been concluded that, while CFA can be used to backfill mine voids, the influx of fresh acidic mine water should be avoided to minimize the remobilization of trapped contaminants such as Fe, Al, Mn and As. However, the pozzolanic material resulting from the CFA-AMD interaction could prevent such influx.

Multicomponent Nanomaterials with Complex Networked Architectures from Orthogonal Degradation and Binary Metal Backfilling in ABC Triblock Terpolymers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cowman, Christina D.; Padgett, Elliot; Tan, Kwan Wee

2015-05-13

Selective degradation of block copolymer templates and backfilling the open mesopores is an effective strategy for the synthesis of nanostructured hybrid and inorganic materials. Incorporation of more than one type of inorganic material in orthogonal ways enables the synthesis of multicomponent nanomaterials with complex yet well-controlled architectures; however, developments in this field have been limited by the availability of appropriate orthogonally degradable block copolymers for use as templates. We report the synthesis and self-assembly into cocontinuous network structures of polyisoprene-block-polystyrene-block-poly(propylene carbonate) where the polyisoprene and poly(propylene carbonate) blocks can be orthogonally removed from the polymer film. Through sequential block etchingmore » and backfilling the resulting mesopores with different metals, we demonstrate first steps toward the preparation of three-component polymer–inorganic hybrid materials with two distinct metal networks. Multiblock copolymers in which two blocks can be degraded and backfilled independently of each other, without interference from the other, may be used in a wide range of applications requiring periodically ordered complex multicomponent nanoarchitectures.« less

Multicomponent nanomaterials with complex networked architectures from orthogonal degradation and binary metal backfilling in ABC triblock terpolymers

DOE PAGES

Cowman, Christina D.; Padgett, Elliot; Tan, Kwan Wee; ...

2015-04-02

Selective degradation of block copolymer templates and backfilling the open mesopores is an effective strategy for the synthesis of nanostructured hybrid and inorganic materials. Incorporation of more than one type of inorganic material in orthogonal ways enables the synthesis of multicomponent nanomaterials with complex yet well-controlled architectures; however, developments in this field have been limited by the availability of appropriate orthogonally degradable block copolymers for use as templates. We report the synthesis and self-assembly into cocontinuous network structures of polyisoprene-block-polystyrene-block-poly(propylene carbonate) where the polyisoprene and poly(propylene carbonate) blocks can be orthogonally removed from the polymer film. Through sequential block etchingmore » and backfilling the resulting mesopores with different metals, we demonstrate first steps toward the preparation of three-component polymer–inorganic hybrid materials with two distinct metal networks. Lastly, multiblock copolymers in which two blocks can be degraded and backfilled independently of each other, without interference from the other, may be used in a wide range of applications requiring periodically ordered complex multicomponent nanoarchitectures.« less

Geochemical modeling of iron, sulfur, oxygen and carbon in a coastal plain aquifer

USGS Publications Warehouse

Brown, C.J.; Schoonen, M.A.A.; Candela, J.L.

2000-01-01

Fe(III) reduction in the Magothy aquifer of Long Island, NY, results in high dissolved-iron concentrations that degrade water quality. Geochemical modeling was used to constrain iron-related geochemical processes and redox zonation along a flow path. The observed increase in dissolved inorganic carbon is consistent with the oxidation of sedimentary organic matter coupled to the reduction of O2 and SO4/2- in the aerobic zone, and to the reduction of SO4/2- in the anaerobic zone; estimated rates of CO2 production through reduction of Fe(III) were relatively minor by comparison. The rates of CO2 production calculated from dissolved inorganic carbon mass transfer (2.55 x 10-4 to 48.6 x 10-4 mmol 1-1 yr-1) generally were comparable to the calculated rates of CO2 production by the combined reduction of O2, Fe(III) and SO4/2- (1.31 x 10-4 to 15 x 10-4 mmol 1-1 yr-1). The overall increase in SO4/2- concentrations along the flow path, together with the results of mass-balance calculations, and variations in ??34S values along the flow path indicate that SO4/2- loss through microbial reduction is exceeded by SO4/2- gain through diffusion from sediments and through the oxidation of FeS2. Geochemichal and microbial data on cores indicate that Fe(III) oxyhydroxide coatings on sediment grains in local, organic carbon- and SO4/2- -rich zones have localized SO4/2- -reducing zones in which the formation of iron disulfides been depleted by microbial reduction and resulted in decreases dissolved iron concentrations. These localized zones of SO4/2- reduction, which are important for assessing zones of low dissolved iron for water-supply development, could be overlooked by aquifer studies that rely only on groundwater data from well-water samples for geochemical modeling. (C) 2000 Elsevier Science B.V.Fe(III) reduction in the Magothy aquifer of Long Island, NY, results in high dissolved-iron concentrations that degrade water quality. Geochemical modeling was used to constrain iron

Geochemical Reaction Mechanism Discovery from Molecular Simulation

DOE PAGES

Stack, Andrew G.; Kent, Paul R. C.

2014-11-10

Methods to explore reactions using computer simulation are becoming increasingly quantitative, versatile, and robust. In this review, a rationale for how molecular simulation can help build better geochemical kinetics models is first given. We summarize some common methods that geochemists use to simulate reaction mechanisms, specifically classical molecular dynamics and quantum chemical methods and discuss their strengths and weaknesses. Useful tools such as umbrella sampling and metadynamics that enable one to explore reactions are discussed. Several case studies wherein geochemists have used these tools to understand reaction mechanisms are presented, including water exchange and sorption on aqueous species and mineralmore » surfaces, surface charging, crystal growth and dissolution, and electron transfer. The impact that molecular simulation has had on our understanding of geochemical reactivity are highlighted in each case. In the future, it is anticipated that molecular simulation of geochemical reaction mechanisms will become more commonplace as a tool to validate and interpret experimental data, and provide a check on the plausibility of geochemical kinetic models.« less

Modeling background radiation using geochemical data: A case study in and around Cameron, Arizona

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marsac, Kara E.; Burnley, Pamela C.; Adcock, Christopher T.

Here, this study compares high-resolution forward models of natural gamma-ray background with that measured by high resolution aerial gamma-ray surveys. The ability to predict variations in natural background radiation levels should prove useful for those engaged in measuring anthropogenic contributions to background radiation for the purpose of emergency response and homeland security operations. The forward models are based on geologic maps and remote sensing multi-spectral imagery combined with two different sources of data: 1) bedrock geochemical data (uranium, potassium and thorium concentrations) collected from national databases, the scientific literature and private companies, and 2) the low spatial resolution NURE (Nationalmore » Uranium Resource Evaluation) aerial gamma-ray survey. The study area near Cameron, Arizona, is located in an arid region with minimal vegetation and, due to the presence of abandoned uranium mines, was the subject of a previous high resolution gamma-ray survey. We found that, in general, geologic map units form a good basis for predicting the geographic distribution of the gamma-ray background. Predictions of background gamma-radiation levels based on bedrock geochemical analyses were not as successful as those based on the NURE aerial survey data sorted by geologic unit. The less successful result of the bedrock geochemical model is most likely due to a number of factors including the need to take into account the evolution of soil geochemistry during chemical weathering and the influence of aeolian addition. Refinements to the forward models were made using ASTER visualizations to create subunits of similar exposure rate within the Chinle Formation, which contains multiple lithologies and by grouping alluvial units by drainage basin rather than age.« less

Modeling background radiation using geochemical data: A case study in and around Cameron, Arizona

DOE PAGES

Marsac, Kara E.; Burnley, Pamela C.; Adcock, Christopher T.; ...

2016-09-16

Here, this study compares high-resolution forward models of natural gamma-ray background with that measured by high resolution aerial gamma-ray surveys. The ability to predict variations in natural background radiation levels should prove useful for those engaged in measuring anthropogenic contributions to background radiation for the purpose of emergency response and homeland security operations. The forward models are based on geologic maps and remote sensing multi-spectral imagery combined with two different sources of data: 1) bedrock geochemical data (uranium, potassium and thorium concentrations) collected from national databases, the scientific literature and private companies, and 2) the low spatial resolution NURE (Nationalmore » Uranium Resource Evaluation) aerial gamma-ray survey. The study area near Cameron, Arizona, is located in an arid region with minimal vegetation and, due to the presence of abandoned uranium mines, was the subject of a previous high resolution gamma-ray survey. We found that, in general, geologic map units form a good basis for predicting the geographic distribution of the gamma-ray background. Predictions of background gamma-radiation levels based on bedrock geochemical analyses were not as successful as those based on the NURE aerial survey data sorted by geologic unit. The less successful result of the bedrock geochemical model is most likely due to a number of factors including the need to take into account the evolution of soil geochemistry during chemical weathering and the influence of aeolian addition. Refinements to the forward models were made using ASTER visualizations to create subunits of similar exposure rate within the Chinle Formation, which contains multiple lithologies and by grouping alluvial units by drainage basin rather than age.« less

PhreeqcRM: A reaction module for transport simulators based on the geochemical model PHREEQC

USGS Publications Warehouse

Parkhurst, David L.; Wissmeier, Laurin

2015-01-01

PhreeqcRM is a geochemical reaction module designed specifically to perform equilibrium and kinetic reaction calculations for reactive transport simulators that use an operator-splitting approach. The basic function of the reaction module is to take component concentrations from the model cells of the transport simulator, run geochemical reactions, and return updated component concentrations to the transport simulator. If multicomponent diffusion is modeled (e.g., Nernst–Planck equation), then aqueous species concentrations can be used instead of component concentrations. The reaction capabilities are a complete implementation of the reaction capabilities of PHREEQC. In each cell, the reaction module maintains the composition of all of the reactants, which may include minerals, exchangers, surface complexers, gas phases, solid solutions, and user-defined kinetic reactants.PhreeqcRM assigns initial and boundary conditions for model cells based on standard PHREEQC input definitions (files or strings) of chemical compositions of solutions and reactants. Additional PhreeqcRM capabilities include methods to eliminate reaction calculations for inactive parts of a model domain, transfer concentrations and other model properties, and retrieve selected results. The module demonstrates good scalability for parallel processing by using multiprocessing with MPI (message passing interface) on distributed memory systems, and limited scalability using multithreading with OpenMP on shared memory systems. PhreeqcRM is written in C++, but interfaces allow methods to be called from C or Fortran. By using the PhreeqcRM reaction module, an existing multicomponent transport simulator can be extended to simulate a wide range of geochemical reactions. Results of the implementation of PhreeqcRM as the reaction engine for transport simulators PHAST and FEFLOW are shown by using an analytical solution and the reactive transport benchmark of MoMaS.

Chemical mixing model studies of lunar orbital geochemical data - Apollo 16 and 17 highlands compositions

NASA Technical Reports Server (NTRS)

Spudis, P. D.; Hawke, B. R.

1982-01-01

Chemical mixing model studies of lunar geochemical data for the central and Taurus-Littrow lunar highlands were performed utilizing pristine highland rock types as end member compositions. The central highlands show considerable diversity in composition; anorthosite is the principal rock type in the Apollo 16/Descartes region, while norite predominates in the highlands west of the landing site. This change in crustal composition is coincident with a major color boundary seen in earth-based multispectral data and probably represents the presence of distinct geochemical provinces within the central highlands. The Taurus-Littrow highlands are dominated by norite; anorthosite is far less abundant than in the central highlands. This suggests that the impact target for the Serenitatis basin was different than that of the Nectaris basin and further strengthens the hypothesis that the lunar highlands are petrologically heterogeneous on a regional basis. It is suggested that the lunar highlands should be viewed in terms of geochemical provinces that have undergone distinct and complex igneous and impact histories.

Interactive Visual Analytics Approch for Exploration of Geochemical Model Simulations with Different Parameter Sets

NASA Astrophysics Data System (ADS)

Jatnieks, Janis; De Lucia, Marco; Sips, Mike; Dransch, Doris

2015-04-01

Many geoscience applications can benefit from testing many combinations of input parameters for geochemical simulation models. It is, however, a challenge to screen the input and output data from the model to identify the significant relationships between input parameters and output variables. For addressing this problem we propose a Visual Analytics approach that has been developed in an ongoing collaboration between computer science and geoscience researchers. Our Visual Analytics approach uses visualization methods of hierarchical horizontal axis, multi-factor stacked bar charts and interactive semi-automated filtering for input and output data together with automatic sensitivity analysis. This guides the users towards significant relationships. We implement our approach as an interactive data exploration tool. It is designed with flexibility in mind, so that a diverse set of tasks such as inverse modeling, sensitivity analysis and model parameter refinement can be supported. Here we demonstrate the capabilities of our approach by two examples for gas storage applications. For the first example our Visual Analytics approach enabled the analyst to observe how the element concentrations change around previously established baselines in response to thousands of different combinations of mineral phases. This supported combinatorial inverse modeling for interpreting observations about the chemical composition of the formation fluids at the Ketzin pilot site for CO2 storage. The results indicate that, within the experimental error range, the formation fluid cannot be considered at local thermodynamical equilibrium with the mineral assemblage of the reservoir rock. This is a valuable insight from the predictive geochemical modeling for the Ketzin site. For the second example our approach supports sensitivity analysis for a reaction involving the reductive dissolution of pyrite with formation of pyrrothite in presence of gaseous hydrogen. We determine that this reaction

A Spatially Constrained Multi-autoencoder Approach for Multivariate Geochemical Anomaly Recognition

NASA Astrophysics Data System (ADS)

Lirong, C.; Qingfeng, G.; Renguang, Z.; Yihui, X.

2017-12-01

Separating and recognizing geochemical anomalies from the geochemical background is one of the key tasks in geochemical exploration. Many methods have been developed, such as calculating the mean ±2 standard deviation, and fractal/multifractal models. In recent years, deep autoencoder, a deep learning approach, have been used for multivariate geochemical anomaly recognition. While being able to deal with the non-normal distributions of geochemical concentrations and the non-linear relationships among them, this self-supervised learning method does not take into account the spatial heterogeneity of geochemical background and the uncertainty induced by the randomly initialized weights of neurons, leading to ineffective recognition of weak anomalies. In this paper, we introduce a spatially constrained multi-autoencoder (SCMA) approach for multivariate geochemical anomaly recognition, which includes two steps: spatial partitioning and anomaly score computation. The first step divides the study area into multiple sub-regions to segregate the geochemical background, by grouping the geochemical samples through K-means clustering, spatial filtering, and spatial constraining rules. In the second step, for each sub-region, a group of autoencoder neural networks are constructed with an identical structure but different initial weights on neurons. Each autoencoder is trained using the geochemical samples within the corresponding sub-region to learn the sub-regional geochemical background. The best autoencoder of a group is chosen as the final model for the corresponding sub-region. The anomaly score at each location can then be calculated as the euclidean distance between the observed concentrations and reconstructed concentrations of geochemical elements.The experiments using the geochemical data and Fe deposits in the southwestern Fujian province of China showed that our SCMA approach greatly improved the recognition of weak anomalies, achieving the AUC of 0.89, compared

Modeling background radiation using geochemical data: A case study in and around Cameron, Arizona.

PubMed

Marsac, Kara E; Burnley, Pamela C; Adcock, Christopher T; Haber, Daniel A; Malchow, Russell L; Hausrath, Elisabeth M

2016-12-01

This study compares high resolution forward models of natural gamma-ray background with that measured by high resolution aerial gamma-ray surveys. The ability to predict variations in natural background radiation levels should prove useful for those engaged in measuring anthropogenic contributions to background radiation for the purpose of emergency response and homeland security operations. The forward models are based on geologic maps and remote sensing multi-spectral imagery combined with two different sources of data: 1) bedrock geochemical data (uranium, potassium and thorium concentrations) collected from national databases, the scientific literature and private companies, and 2) the low spatial resolution NURE (National Uranium Resource Evaluation) aerial gamma-ray survey. The study area near Cameron, Arizona, is located in an arid region with minimal vegetation and, due to the presence of abandoned uranium mines, was the subject of a previous high resolution gamma-ray survey. We found that, in general, geologic map units form a good basis for predicting the geographic distribution of the gamma-ray background. Predictions of background gamma-radiation levels based on bedrock geochemical analyses were not as successful as those based on the NURE aerial survey data sorted by geologic unit. The less successful result of the bedrock geochemical model is most likely due to a number of factors including the need to take into account the evolution of soil geochemistry during chemical weathering and the influence of aeolian addition. Refinements to the forward models were made using ASTER visualizations to create subunits of similar exposure rate within the Chinle Formation, which contains multiple lithologies and by grouping alluvial units by drainage basin rather than age. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Recycled Asphalt Pavement and Crushed Concrete Backfill: State-of-the-Art Review and Material Characterization

DOT National Transportation Integrated Search

2001-10-01

This report describes research results from the first year of a three-year study focused on the use of recycled asphalt pavement (RAP) and crushed concrete (CC) as backfill for mechanically stabilized earth (MSE) walls.

A geochemical examination of humidity cell tests

USGS Publications Warehouse

Maest, Ann; Nordstrom, D. Kirk

2017-01-01

Humidity cell tests (HCTs) are long-term (20 to >300 weeks) leach tests that are considered by some to be the among the most reliable geochemical characterization methods for estimating the leachate quality of mined materials. A number of modifications have been added to the original HCT method, but the interpretation of test results varies widely. We suggest that the HCTs represent an underutilized source of geochemical data, with a year-long test generating approximately 2500 individual chemical data points. The HCT concentration peaks and valleys can be thought of as a “chromatogram” of reactions that may occur in the field, whereby peaks in concentrations are associated with different geochemical processes, including sulfate salt dissolution, sulfide oxidation, and dissolution of rock-forming minerals, some of which can neutralize acid. Some of these reactions occur simultaneously, some do not, and geochemical modeling can be used to help distinguish the dominant processes. Our detailed examination, including speciation and inverse modeling, of HCTs from three projects with different geology and mineralization shows that rapid sulfide oxidation dominates over a limited period of time that starts between 40 and 200 weeks of testing. The applicability of laboratory tests results to predicting field leachate concentrations, loads, or rates of reaction has not been adequately demonstrated, although early flush releases and rapid sulfide oxidation rates in HCTs should have some relevance to field conditions. Knowledge of possible maximum solute concentrations is needed to design effective treatment and mitigation approaches. Early flush and maximum sulfide oxidation results from HCTs should be retained and used in environmental models. Factors that complicate the use of HCTs include: sample representation, time for microbial oxidizers to grow, sample storage before testing, geochemical reactions that add or remove constituents, and the HCT results chosen for use

Modeling Background Radiation in our Environment Using Geochemical Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malchow, Russell L.; Marsac, Kara; Burnley, Pamela

2015-02-01

Radiation occurs naturally in bedrock and soil. Gamma rays are released from the decay of the radioactive isotopes K, U, and Th. Gamma rays observed at the surface come from the first 30 cm of rock and soil. The energy of gamma rays is specific to each isotope, allowing identification. For this research, data was collected from national databases, private companies, scientific literature, and field work. Data points were then evaluated for self-consistency. A model was created by converting concentrations of U, K, and Th for each rock and soil unit into a ground exposure rate using the following equation:more » D=1.32 K+ 0.548 U+ 0.272 Th. The first objective of this research was to compare the original Aerial Measurement System gamma ray survey to results produced by the model. The second objective was to improve the method and learn the constraints of the model. Future work will include sample data analysis from field work with a goal of improving the geochemical model.« less

Hydro-geochemical modeling of the spatial and the temporal geochemical variations of the granitic Strengbach catchment springs (Vosges massif, France)

NASA Astrophysics Data System (ADS)

Ackerer, Julien; Chabaux, François; Lucas, Yann; Pierret, Marie Claire; Viville, Daniel; Fritz, Bertrand; Clement, Alain; Beaulieu, Emilie; Negrel, Philippe

2017-04-01

Regular analysis of the major element concentrations in waters from springs emerging on the Strengbach catchment is made for more than 20 years (OHGE, Observatoire Hydro-Géochimique de l'Environnement). These data confirm the spatial variability of geochemical characteristics of the Strengbach springs linked, at least partly, to the lithological variability of the substratum (Pierret et al., 2014). The data also indicate that at the first order, the geochemical fluxes exported from each spring are mainly linked to the spring discharges, without significant variations of the relationships linking these two parameters between 1990 and 2010. There is also no observation of significant variations for the dissolved silica and for most of the cationic concentrations with time. Only a significant decrease of the Ca concentrations is observed for the Strengbach springs from 1990 to 2010. Numerical simulations, performed with the KIRMAT hydro-geochemical code, show that such a decrease can be considered as the response in the "bedrock" of the water-rock interactions to the variations of the soil solution chemical compositions recorded over the last 20 years, marked by a significant increase of pH and decrease of Ca concentrations. In particular, the modeling results show that the Ca concentration decrease is controlled by the couple apatite/clays, and that significant modifications of the apatite dissolution rate and clay compositions occurred between 1990 and 2010. This study shows that the temporal evolution of the Strengbach spring chemistry cannot be explained by the only variations of the clay mineral compositions, i.e. a modification of the chemical composition of the precipitated clays or a modification of the ionic exchange capacity of the clay minerals, but that it is definitely the interrelations between the apatite and the clay minerals that are involved.

Solid phase studies and geochemical modelling of low-cost permeable reactive barriers.

PubMed

Bartzas, Georgios; Komnitsas, Kostas

2010-11-15

A continuous column experiment was carried out under dynamic flow conditions in order to study the efficiency of low-cost permeable reactive barriers (PRBs) to remove several inorganic contaminants from acidic solutions. A 50:50 w/w waste iron/sand mixture was used as candidate reactive media in order to activate precipitation and promote sorption and reduction-oxidation mechanisms. Solid phase studies of the exhausted reactive products after column shutdown, using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), confirmed that the principal Fe corrosion products identified in the reactive zone are amorphous iron (hydr)oxides (maghemite/magnetite and goethite), intermediate products (sulfate green rust), and amorphous metal sulfides such as amFeS and/or mackinawite. Geochemical modelling of the metal removal processes, including interactions between reactive media, heavy metal ions and sulfates, and interpretation of the ionic profiles was also carried out by using the speciation/mass transfer computer code PHREEQC-2 and the WATEQ4F database. Mineralogical characterization studies as well as geochemical modelling calculations also indicate that the effect of sulfate and silica sand on the efficiency of the reactive zone should be considered carefully during design and operation of low-cost field PRBs. Copyright © 2010 Elsevier B.V. All rights reserved.

Modeling Anaerobic Soil Organic Carbon Decomposition in Arctic Polygon Tundra: Insights into Soil Geochemical Influences on Carbon Mineralization: Modeling Archive

DOE Data Explorer

Zheng, Jianqiu; Thornton, Peter; Painter, Scott; Gu, Baohua; Wullschleger, Stan; Graham, David

2018-06-13

This anaerobic carbon decomposition model is developed with explicit representation of fermentation, methanogenesis and iron reduction by combining three well-known modeling approaches developed in different disciplines. A pool-based model to represent upstream carbon transformations and replenishment of DOC pool, a thermodynamically-based model to calculate rate kinetics and biomass growth for methanogenesis and Fe(III) reduction, and a humic ion-binding model for aqueous phase speciation and pH calculation are implemented into the open source geochemical model PHREEQC (V3.0). Installation of PHREEQC is required to run this model.

Geochemical modeling of subsurface fluid generation in the Gulf of Cadiz

NASA Astrophysics Data System (ADS)

Schmidt, Christopher; Hensen, Christian; Wallmann, Klaus

2016-04-01

During RV METEOR cruise M86/5 in 2012 a number of deep-sea mud volcanoes were discovered at about 4500 m water depth west of the deformation front of the accretionary wedge in the Gulf of Cadiz (NE Atlantic). Fluid flow at these locations is mediated by an active strike-slip fault marking the transcurrent plate boundary between Africa and Eurasia. Geochemical signals of emanating fluids have been interpreted as being a mixture of various deep-sourced processes such as the alteration of oceanic crust, clay-mineral dehydration, and recrystallization of carbonaceous, Upper Jurassic sediments (Hensen et al. 2015). In the current study we present results of a geochemical reactive-transport model that was designed to simulate major fluid-affecting processes, such as the smectite to illite transformation or recrystallization of carbonates in order to provide a proof of concept. Preliminary results show that the model is able to reproduce pore water signatures (e.g. for chloride, strontium, 87Sr/86Sr) in subsurface sediments that are similar to those of MV fluids. Hensen, C., Scholz, F., Nuzzo, M., Valadares, V., Gràcia, E., Terrinha, P., Liebetrau, V., Kaul, N., Silva, S., Martínez-Loriente, S., Bartolome, R., Piñero, E., Magalhães, V.H., Schmidt, M., Weise, S.M., Cunha, M., Hilario, A., Perea, H., Rovelli, L. and Lackschewitz, K. (2015) Strike-slip faults mediate the rise of crustal-derived fluids and mud volcanism in the deep sea. Geology 43, 339-342.

A review of the hydrogeologic-geochemical model for Cerro Prieto

USGS Publications Warehouse

Lippmann, M.J.; Truesdell, A.H.; Halfman-Dooley, S. E.; Mañónm, A.

1991-01-01

With continued exploitation of the Cerro Prieto, Mexico, geothermal field, there is increasing evidence that the hydrogeologic model developed by Halfman and co-workers presents the basic features controlling the movement of geothermal fluids in the system. In mid-1987 the total installed capacity at Cerro Prieto reached 620 MWc, requiring a large rate of fluid production (more than 10,500 tonnes/hr of a brine-steam mixture; August 1988). This significant mass extraction has led to changes in reservoir thermodynamic conditions and in the chemistry of the produced fluids. Pressure drawdown has caused an increase in cold water recharge in the southern and western edges of the field, and local and general reservoir boiling in parts of the geothermal system. After reviewing the hydrogeologic and geochemical models of Cerro Prieto, the exploitation-induced cold water recharge and reservoir boiling (and plugging) observed in different areas of the field, are discussed and interpreted on the basis of these models and schematic flow models that describe the hydrogeology. ?? 1991.

Geochemical Characterization Using Geophysical Data and Markov Chain Monte Carlo Methods

NASA Astrophysics Data System (ADS)

Chen, J.; Hubbard, S.; Rubin, Y.; Murray, C.; Roden, E.; Majer, E.

2002-12-01

Although the spatial distribution of geochemical parameters is extremely important for many subsurface remediation approaches, traditional characterization of those parameters is invasive and laborious, and thus is rarely performed sufficiently to describe natural hydrogeological variability at the field-scale. This study is an effort to jointly use multiple sources of information, including noninvasive geophysical data, for geochemical characterization of the saturated and anaerobic portion of the DOE South Oyster Bacterial Transport Site in Virginia. Our data set includes hydrogeological and geochemical measurements from five boreholes and ground-penetrating radar (GPR) and seismic tomographic data along two profiles that traverse the boreholes. The primary geochemical parameters are the concentrations of extractable ferrous iron Fe(II) and ferric iron Fe(III). Since iron-reducing bacteria can reduce Fe(III) to Fe(II) under certain conditions, information about the spatial distributions of Fe(II) and Fe(III) may indicate both where microbial iron reduction has occurred and in which zone it is likely to occur in the future. In addition, as geochemical heterogeneity influences bacterial transport and activity, estimates of the geochemical parameters provide important input to numerical flow and contaminant transport models geared toward bioremediation. Motivated by our previous research, which demonstrated that crosshole geophysical data could be very useful for estimating hydrogeological parameters, we hypothesize in this study that geochemical and geophysical parameters may be linked through their mutual dependence on hydrogeological parameters such as lithofacies. We attempt to estimate geochemical parameters using both hydrogeological and geophysical measurements in a Bayesian framework. Within the two-dimensional study domain (12m x 6m vertical cross section divided into 0.25m x 0.25m pixels), geochemical and hydrogeological parameters were considered as data

Preparation of fly ash-granulated blast furnace slag-carbide slag binder and application in total tailings paste backfill

NASA Astrophysics Data System (ADS)

Li, Chao; Hao, Ya-fei; Zhao, Feng-qing

2018-03-01

Based on activation and synergistic effect among various materials, a low-cost mine backfill cementing material, FGC binder, was prepared by using fly ash, granulated blast-furnace slag (GBFS), carbide slag and composite activator. The proper proportioning of FGC binder is obtained by response surface experiment optimization method: fly ash 62 %, GBFS 20 %, carbide slag 8 % and compound activators 10 %. Adjusting the material ratio obtains different cementing material which could satisfy requirements of different mined-out areas. With the mass ratio of cementing material and tailings 1:4∼1:8, the concentration of total solid 70 %, the compressive strength values of total tailings filling body at 28 d reaches 1.64∼4.14 MPa, and the backfilling cost is 20 % lower than using OPC cement.

Fluid-rock geochemical interaction for modelling calibration in geothermal exploration in Indonesia

NASA Astrophysics Data System (ADS)

Deon, Fiorenza; Barnhoorn, Auke; Lievens, Caroline; Ryannugroho, Riskiray; Imaro, Tulus; Bruhn, David; van der Meer, Freek; Hutami, Rizki; Sibarani, Besteba; Sule, Rachmat; Saptadij, Nenny; Hecker, Christoph; Appelt, Oona; Wilke, Franziska

2017-04-01

Indonesia with its large, but partially unexplored geothermal potential is one of the most interesting and suitable places in the world to conduct geothermal exploration research. This study focuses on geothermal exploration based on fluid-rock geochemistry/geomechanics and aims to compile an overview on geochemical data-rock properties from important geothermal fields in Indonesia. The research carried out in the field and in the laboratory is performed in the framework of the GEOCAP cooperation (Geothermal Capacity Building program Indonesia- the Netherlands). The application of petrology and geochemistry accounts to a better understanding of areas where operating power plants exist but also helps in the initial exploration stage of green areas. Because of their relevance and geological setting geothermal fields in Java, Sulawesi and the sedimentary basin of central Sumatra have been chosen as focus areas of this study. Operators, universities and governmental agencies will benefit from this approach as it will be applied also to new green-field terrains. By comparing the characteristic of the fluids, the alteration petrology and the rock geochemistry we also aim to contribute to compile an overview of the geochemistry of the important geothermal fields in Indonesia. At the same time the rock petrology and fluid geochemistry will be used as input data to model the reservoir fluid composition along with T-P parameters with the geochemical workbench PHREEQC. The field and laboratory data are mandatory for both the implementation and validation of the model results.

Dedicated heterogeneous node scheduling including backfill scheduling

DOEpatents

Wood, Robert R [Livermore, CA; Eckert, Philip D [Livermore, CA; Hommes, Gregg [Pleasanton, CA

2006-07-25

A method and system for job backfill scheduling dedicated heterogeneous nodes in a multi-node computing environment. Heterogeneous nodes are grouped into homogeneous node sub-pools. For each sub-pool, a free node schedule (FNS) is created so that the number of to chart the free nodes over time. For each prioritized job, using the FNS of sub-pools having nodes useable by a particular job, to determine the earliest time range (ETR) capable of running the job. Once determined for a particular job, scheduling the job to run in that ETR. If the ETR determined for a lower priority job (LPJ) has a start time earlier than a higher priority job (HPJ), then the LPJ is scheduled in that ETR if it would not disturb the anticipated start times of any HPJ previously scheduled for a future time. Thus, efficient utilization and throughput of such computing environments may be increased by utilizing resources otherwise remaining idle.

Methods for geochemical analysis

USGS Publications Warehouse

Baedecker, Philip A.

1987-01-01

The laboratories for analytical chemistry within the Geologic Division of the U.S. Geological Survey are administered by the Office of Mineral Resources. The laboratory analysts provide analytical support to those programs of the Geologic Division that require chemical information and conduct basic research in analytical and geochemical areas vital to the furtherance of Division program goals. Laboratories for research and geochemical analysis are maintained at the three major centers in Reston, Virginia, Denver, Colorado, and Menlo Park, California. The Division has an expertise in a broad spectrum of analytical techniques, and the analytical research is designed to advance the state of the art of existing techniques and to develop new methods of analysis in response to special problems in geochemical analysis. The geochemical research and analytical results are applied to the solution of fundamental geochemical problems relating to the origin of mineral deposits and fossil fuels, as well as to studies relating to the distribution of elements in varied geologic systems, the mechanisms by which they are transported, and their impact on the environment.

Geochemical mole-balance modeling with uncertain data

USGS Publications Warehouse

Parkhurst, David L.

1997-01-01

Geochemical mole-balance models are sets of chemical reactions that quantitatively account for changes in the chemical and isotopic composition of water along a flow path. A revised mole-balance formulation that includes an uncertainty term for each chemical and isotopic datum is derived. The revised formulation is comprised of mole-balance equations for each element or element redox state, alkalinity, electrons, solvent water, and each isotope; a charge-balance equation and an equation that relates the uncertainty terms for pH, alkalinity, and total dissolved inorganic carbon for each aqueous solution; inequality constraints on the size of the uncertainty terms; and inequality constraints on the sign of the mole transfer of reactants. The equations and inequality constraints are solved by a modification of the simplex algorithm combined with an exhaustive search for unique combinations of aqueous solutions and reactants for which the equations and inequality constraints can be solved and the uncertainty terms minimized. Additional algorithms find only the simplest mole-balance models and determine the ranges of mixing fractions for each solution and mole transfers for each reactant that are consistent with specified limits on the uncertainty terms. The revised formulation produces simpler and more robust mole-balance models and allows the significance of mixing fractions and mole transfers to be evaluated. In an example from the central Oklahoma aquifer, inclusion of up to 5% uncertainty in the chemical data can reduce the number of reactants in mole-balance models from seven or more to as few as three, these being cation exchange, dolomite dissolution, and silica precipitation. In another example from the Madison aquifer, inclusion of the charge-balance constraint requires significant increases in the mole transfers of calcite, dolomite, and organic matter, which reduce the estimated maximum carbon 14 age of the sample by about 10,000 years, from 22,700 years to

Comparison of U-spatial statistics and C-A fractal models for delineating anomaly patterns of porphyry-type Cu geochemical signatures in the Varzaghan district, NW Iran

NASA Astrophysics Data System (ADS)

Ghezelbash, Reza; Maghsoudi, Abbas

2018-05-01

The delineation of populations of stream sediment geochemical data is a crucial task in regional exploration surveys. In this contribution, uni-element stream sediment geochemical data of Cu, Au, Mo, and Bi have been subjected to two reliable anomaly-background separation methods, namely, the concentration-area (C-A) fractal and the U-spatial statistics methods to separate geochemical anomalies related to porphyry-type Cu mineralization in northwest Iran. The quantitative comparison of the delineated geochemical populations using the modified success-rate curves revealed the superiority of the U-spatial statistics method over the fractal model. Moreover, geochemical maps of investigated elements revealed strongly positive correlations between strong anomalies and Oligocene-Miocene intrusions in the study area. Therefore, follow-up exploration programs should focus on these areas.

A compilation of rate parameters of water-mineral interaction kinetics for application to geochemical modeling

USGS Publications Warehouse

Palandri, James L.; Kharaka, Yousif K.

2004-01-01

Geochemical reaction path modeling is useful for rapidly assessing the extent of water-aqueous-gas interactions both in natural systems and in industrial processes. Modeling of some systems, such as those at low temperature with relatively high hydrologic flow rates, or those perturbed by the subsurface injection of industrial waste such as CO2 or H2S, must account for the relatively slow kinetics of mineral-gas-water interactions. We have therefore compiled parameters conforming to a general Arrhenius-type rate equation, for over 70 minerals, including phases from all the major classes of silicates, most carbonates, and many other non-silicates. The compiled dissolution rate constants range from -0.21 log moles m-2 s-1 for halite, to -17.44 log moles m-2 s-1 for kyanite, for conditions far from equilibrium, at 25 ?C, and pH near neutral. These data have been added to a computer code that simulates an infinitely well-stirred batch reactor, allowing computation of mass transfer as a function of time. Actual equilibration rates are expected to be much slower than those predicted by the selected computer code, primarily because actual geochemical processes commonly involve flow through porous or fractured media, wherein the development of concentration gradients in the aqueous phase near mineral surfaces, which results in decreased absolute chemical affinity and slower reaction rates. Further differences between observed and computed reaction rates may occur because of variables beyond the scope of most geochemical simulators, such as variation in grain size, aquifer heterogeneity, preferred fluid flow paths, primary and secondary mineral coatings, and secondary minerals that may lead to decreased porosity and clogged pore throats.

Evaluation of Computational Method of High Reynolds Number Slurry Flow for Caverns Backfilling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bettin, Giorgia

2015-05-01

The abandonment of salt caverns used for brining or product storage poses a significant environmental and economic risk. Risk mitigation can in part be address ed by the process of backfilling which can improve the cavern geomechanical stability and reduce the risk o f fluid loss to the environment. This study evaluate s a currently available computational tool , Barracuda, to simulate such process es as slurry flow at high Reynolds number with high particle loading . Using Barracuda software, a parametric sequence of simu lations evaluated slurry flow at Re ynolds number up to 15000 and loading up tomore » 25%. Li mitations come into the long time required to run these simulation s due in particular to the mesh size requirement at the jet nozzle. This study has found that slurry - jet width and centerline velocities are functions of Re ynold s number and volume fractio n The solid phase was found to spread less than the water - phase with a spreading rate smaller than 1 , dependent on the volume fraction. Particle size distribution does seem to have a large influence on the jet flow development. This study constitutes a first step to understand the behavior of highly loaded slurries and their ultimate application to cavern backfilling.« less

Alaska Geochemical Database (AGDB)-Geochemical data for rock, sediment, soil, mineral, and concentrate sample media

USGS Publications Warehouse

Granitto, Matthew; Bailey, Elizabeth A.; Schmidt, Jeanine M.; Shew, Nora B.; Gamble, Bruce M.; Labay, Keith A.

2011-01-01

The Alaska Geochemical Database (AGDB) was created and designed to compile and integrate geochemical data from Alaska in order to facilitate geologic mapping, petrologic studies, mineral resource assessments, definition of geochemical baseline values and statistics, environmental impact assessments, and studies in medical geology. This Microsoft Access database serves as a data archive in support of present and future Alaskan geologic and geochemical projects, and contains data tables describing historical and new quantitative and qualitative geochemical analyses. The analytical results were determined by 85 laboratory and field analytical methods on 264,095 rock, sediment, soil, mineral and heavy-mineral concentrate samples. Most samples were collected by U.S. Geological Survey (USGS) personnel and analyzed in USGS laboratories or, under contracts, in commercial analytical laboratories. These data represent analyses of samples collected as part of various USGS programs and projects from 1962 to 2009. In addition, mineralogical data from 18,138 nonmagnetic heavy mineral concentrate samples are included in this database. The AGDB includes historical geochemical data originally archived in the USGS Rock Analysis Storage System (RASS) database, used from the mid-1960s through the late 1980s and the USGS PLUTO database used from the mid-1970s through the mid-1990s. All of these data are currently maintained in the Oracle-based National Geochemical Database (NGDB). Retrievals from the NGDB were used to generate most of the AGDB data set. These data were checked for accuracy regarding sample location, sample media type, and analytical methods used. This arduous process of reviewing, verifying and, where necessary, editing all USGS geochemical data resulted in a significantly improved Alaska geochemical dataset. USGS data that were not previously in the NGDB because the data predate the earliest USGS geochemical databases, or were once excluded for programmatic reasons

Improved Geothermometry Through Multivariate Reaction-path Modeling and Evaluation of Geomicrobiological Influences on Geochemical Temperature Indicators: Final Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mattson, Earl; Smith, Robert; Fujita, Yoshiko

2015-03-01

The project was aimed at demonstrating that the geothermometric predictions can be improved through the application of multi-element reaction path modeling that accounts for lithologic and tectonic settings, while also accounting for biological influences on geochemical temperature indicators. The limited utilization of chemical signatures by individual traditional geothermometer in the development of reservoir temperature estimates may have been constraining their reliability for evaluation of potential geothermal resources. This project, however, was intended to build a geothermometry tool which can integrate multi-component reaction path modeling with process-optimization capability that can be applied to dilute, low-temperature water samples to consistently predict reservoirmore » temperature within ±30 °C. The project was also intended to evaluate the extent to which microbiological processes can modulate the geochemical signals in some thermal waters and influence the geothermometric predictions.« less

Mineral dissolution and precipitation during CO 2 injection at the Frio-I Brine Pilot: Geochemical modeling and uncertainty analysis

DOE PAGES

Ilgen, A. G.; Cygan, R. T.

2015-12-07

During the Frio-I Brine Pilot CO 2 injection experiment in 2004, distinct geochemical changes in response to the injection of 1600 tons of CO 2 were recorded in samples collected from the monitoring well. Previous geochemical modeling studies have considered dissolution of calcite and iron oxyhydroxides, or release of adsorbed iron, as the most likely sources of the increased ion concentrations. We explore in this modeling study possible alternative sources of the increasing calcium and iron, based on the data from the detailed petrographic characterization of the Upper Frio Formation “C”. Particularly, we evaluate whether dissolution of pyrite andmore » oligoclase (anorthite component) can account for the observed geochemical changes. Due to kinetic limitations, dissolution of pyrite and anorthite cannot account for the increased iron and calcium concentrations on the time scale of the field test (10 days). However, dissolution of these minerals is contributing to carbonate and clay mineral precipitation on the longer time scales (1000 years). The one-dimensional reactive transport model predicts carbonate minerals, dolomite and ankerite, as well as clay minerals kaolinite, nontronite and montmorillonite, will precipitate in the Frio Formation “C” sandstone as the system progresses towards chemical equilibrium during a 1000-year period. Cumulative uncertainties associated with using different thermodynamic databases, activity correction models (Pitzer vs. B-dot), and extrapolating to reservoir temperature, are manifested in the difference in the predicted mineral phases. Furthermore, these models are consistent with regards to the total volume of mineral precipitation and porosity values which are predicted to within 0.002%.« less

A combined geodynamical-geochemical modelling approach to investigating the Lu-Hf isotopic evolution of the terrestrial mantle and crust

NASA Astrophysics Data System (ADS)

Jones, R.; Van Keken, P. E.; Hauri, E.; Vervoort, J. D.; Ballentine, C. J.

2017-12-01

The chemical and isotopic evolution of the Earth's mantle is largely influenced by the formation of oceanic and continental crust at spreading ridges and through arc volcanism, and the subsequent recycling of this crust back into the mantle via subduction. In this study we use a combined geodynamical-geochemical modelling approach to investigate the Lu-Hf isotopic evolution of the terrestrial mantle and crust. We utilise the geodynamic mantle convection model developed by Brandenburg et al., 2008. This model satisfies the geophysical constraints of oceanic heat flow and average plate velocities, as well as geochemical observations such as 40Ar in the atmosphere. It has also been shown to reproduce the observed geochemical distributions in multiple isotope systems (U-Th-Pb, Rb-Sr, Sm-Nd, and Re-Os) that define the DMM, HIMU and EM1 mantle endmembers. We go on to extend this application to investigate the Lu-Hf isotope system, specifically in combination with Sm-Nd. The model has been updated to include a self-consistent reorganisation of the plates with regions of up-/down-wellings. The model is initiated at 4.55 Ga, assumes continental crust is produced from 4 Ga and that a transition from `dry' to `wet' subduction occurs at 3 Ga. The results of the geodynamic model suggest that the ƐHf composition and evolution of the upper mantle can be generated through the extraction and recycling of oceanic crust, which creates an enriched and radiogenic reservoir at the core-mantle boundary. The formation of continental crust, which is extracted at each time-step from the oceanic crust to imitate subduction zone processes, and the recycling of this continental crust as sediments, plays a lesser role. Depending on the selected partition coefficients DMM, FOZO and HIMU mantle endmember compositions are also produced via the simple extraction and recycling of oceanic crust. The formation of continental crust produces spread in the ƐNd vs. ƐHf array and extends the model

TAPIR--Finnish national geochemical baseline database.

PubMed

Jarva, Jaana; Tarvainen, Timo; Reinikainen, Jussi; Eklund, Mikael

2010-09-15

In Finland, a Government Decree on the Assessment of Soil Contamination and Remediation Needs has generated a need for reliable and readily accessible data on geochemical baseline concentrations in Finnish soils. According to the Decree, baseline concentrations, referring both to the natural geological background concentrations and the diffuse anthropogenic input of substances, shall be taken into account in the soil contamination assessment process. This baseline information is provided in a national geochemical baseline database, TAPIR, that is publicly available via the Internet. Geochemical provinces with elevated baseline concentrations were delineated to provide regional geochemical baseline values. The nationwide geochemical datasets were used to divide Finland into geochemical provinces. Several metals (Co, Cr, Cu, Ni, V, and Zn) showed anomalous concentrations in seven regions that were defined as metal provinces. Arsenic did not follow a similar distribution to any other elements, and four arsenic provinces were separately determined. Nationwide geochemical datasets were not available for some other important elements such as Cd and Pb. Although these elements are included in the TAPIR system, their distribution does not necessarily follow the ones pre-defined for metal and arsenic provinces. Regional geochemical baseline values, presented as upper limit of geochemical variation within the region, can be used as trigger values to assess potential soil contamination. Baseline values have also been used to determine upper and lower guideline values that must be taken into account as a tool in basic risk assessment. If regional geochemical baseline values are available, the national guideline values prescribed in the Decree based on ecological risks can be modified accordingly. The national geochemical baseline database provides scientifically sound, easily accessible and generally accepted information on the baseline values, and it can be used in various

Equilibrium geochemical modeling of a seasonal thermal energy storage aquifer field test

NASA Technical Reports Server (NTRS)

Stottlemyre, J. S.

1980-01-01

A geochemical mathematical modeling study designed to investigate the well plugging problems encountered at the Auburn University experimental field tests is summarized. The results, primarily of qualitative interest, include: (1) loss of injectivity was probably due to a combination of native particulate plugging and clay swelling and dispersion; (2) fluid-fluid incompatibilities, hydrothermal reactions, and oxidation reactions were of insignificant magnitude or too slow to have contributed markedly to the plugging; and (3) the potential for and contributions from temperature-induced dissolved gas solubility reductions, capillary boundary layer viscosity increases, and microstructural deformation cannot be deconvolved from the available data.

Evaluation and analysis of current compaction methods for FDOT pipe trench backfills in areas of high water tables

DOT National Transportation Integrated Search

1999-01-01

This research project was undertaken to examine the practicality and adequacy of the FDOT specifications regarding compaction methods for pipe trench backfills under high water table. Given the difficulty to determine density and to attain desired de...

A conceptual geochemical model of the geothermal system at Surprise Valley, CA

NASA Astrophysics Data System (ADS)

Fowler, Andrew P. G.; Ferguson, Colin; Cantwell, Carolyn A.; Zierenberg, Robert A.; McClain, James; Spycher, Nicolas; Dobson, Patrick

2018-03-01

Characterizing the geothermal system at Surprise Valley (SV), northeastern California, is important for determining the sustainability of the energy resource, and mitigating hazards associated with hydrothermal eruptions that last occurred in 1951. Previous geochemical studies of the area attempted to reconcile different hot spring compositions on the western and eastern sides of the valley using scenarios of dilution, equilibration at low temperatures, surface evaporation, and differences in rock type along flow paths. These models were primarily supported using classical geothermometry methods, and generally assumed that fluids in the Lake City mud volcano area on the western side of the valley best reflect the composition of a deep geothermal fluid. In this contribution, we address controls on hot spring compositions using a different suite of geochemical tools, including optimized multicomponent geochemistry (GeoT) models, hot spring fluid major and trace element measurements, mineralogical observations, and stable isotope measurements of hot spring fluids and precipitated carbonates. We synthesize the results into a conceptual geochemical model of the Surprise Valley geothermal system, and show that high-temperature (quartz, Na/K, Na/K/Ca) classical geothermometers fail to predict maximum subsurface temperatures because fluids re-equilibrated at progressively lower temperatures during outflow, including in the Lake City area. We propose a model where hot spring fluids originate as a mixture between a deep thermal brine and modern meteoric fluids, with a seasonally variable mixing ratio. The deep brine has deuterium values at least 3 to 4‰ lighter than any known groundwater or high-elevation snow previously measured in and adjacent to SV, suggesting it was recharged during the Pleistocene when meteoric fluids had lower deuterium values. The deuterium values and compositional characteristics of the deep brine have only been identified in thermal springs and

INEEL Subregional Conceptual Model Report Volume 2: Summary of Existing Knowledge of Geochemical Influences on the Fate and Transport of Contaminants in the Subsurface at the INEEL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paul L. Wichlacz; Robert C. Starr; Brennon Orr

2003-09-01

This document summarizes previous descriptions of geochemical system conceptual models for the vadose zone and groundwater zone (aquifer) beneath the Idaho National Engineering and Environmental Laboratory (INEEL). The primary focus is on groundwater because contaminants derived from wastes disposed at INEEL are present in groundwater, groundwater provides a pathway for potential migration to receptors, and because geochemical characteristics in and processes in the aquifer can substantially affect the movement, attenuation, and toxicity of contaminants. The secondary emphasis is perched water bodies in the vadose zone. Perched water eventually reaches the regional groundwater system, and thus processes that affect contaminants inmore » the perched water bodies are important relative to the migration of contaminants into groundwater. Similarly, processes that affect solutes during transport from nearsurface disposal facilities downward through the vadose zone to the aquifer are relevant. Sediments in the vadose zone can affect both water and solute transport by restricting the downward migration of water sufficiently that a perched water body forms, and by retarding solute migration via ion exchange. Geochemical conceptual models have been prepared by a variety of researchers for different purposes. They have been published in documents prepared by INEEL contractors, the United States Geological Survey (USGS), academic researchers, and others. The documents themselves are INEEL and USGS reports, and articles in technical journals. The documents reviewed were selected from citation lists generated by searching the INEEL Technical Library, the INEEL Environmental Restoration Optical Imaging System, and the ISI Web of Science databases. The citation lists were generated using the keywords ground water, groundwater, chemistry, geochemistry, contaminant, INEL, INEEL, and Idaho. In addition, a list of USGS documents that pertain to the INEEL was obtained and manually

Mercury Slovenian soils: High, medium and low sample density geochemical maps

NASA Astrophysics Data System (ADS)

Gosar, Mateja; Šajn, Robert; Teršič, Tamara

2017-04-01

Regional geochemical survey was conducted in whole territory of Slovenia (20273 km2). High, medium and low sample density surveys were compared. High sample density represented the regional geochemical data set supplemented by local high-density sampling data (irregular grid, n=2835). Medium-density soil sampling was performed in a 5 x 5 km grid (n=817) and low-density geochemical survey was conducted in a sampling grid 25 x 25 km (n=54). Mercury distribution in Slovenian soils was determined with models of mercury distribution in soil using all three data sets. A distinct Hg anomaly in western part of Slovenia is evident on all three models. It is a consequence of 500-years of mining and ore processing in the second largest mercury mine in the world, the Idrija mine. The determined mercury concentrations revealed an important difference between the western and the eastern parts of the country. For the medium scale geochemical mapping is the median value (0.151 mg /kg) for western Slovenia almost 2-fold higher than the median value (0.083 mg/kg) in eastern Slovenia. Besides the Hg median for the western part of Slovenia exceeds the Hg median for European soil by a factor of 4 (Gosar et al., 2016). Comparing these sample density surveys, it was shown that high sampling density allows the identification and characterization of anthropogenic influences on a local scale, while medium- and low-density sampling reveal general trends in the mercury spatial distribution, but are not appropriate for identifying local contamination in industrial regions and urban areas. The resolution of the pattern generated is the best when the high-density survey on a regional scale is supplemented with the geochemical data of the high-density surveys on a local scale. References: Gosar, M, Šajn, R, Teršič, T. Distribution pattern of mercury in the Slovenian soil: geochemical mapping based on multiple geochemical datasets. Journal of geochemical exploration, 2016, 167/38-48.

Geomechanical/Geochemical Modeling Studies Conducted within theInternational DECOVALEX Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Birkholzer, J.T.; Rutqvist, J.; Sonnenthal, E.L.

2005-10-19

The DECOVALEX project is an international cooperative project initiated by SKI, the Swedish Nuclear Power Inspectorate, with participation of about 10 international organizations. The general goal of this project is to encourage multidisciplinary interactive and cooperative research on modeling coupled thermo-hydro-mechanical-chemical (THMC) processes in geologic formations in support of the performance assessment for underground storage of radioactive waste. One of the research tasks, initiated in 2004 by the U.S. Department of Energy (DOE), addresses the long-term impact of geomechanical and geochemical processes on the flow conditions near waste emplacement tunnels. Within this task, four international research teams conduct predictive analysismore » of the coupled processes in two generic repositories, using multiple approaches and different computer codes. Below, we give an overview of the research task and report its current status.« less

Geomechanical/ Geochemical Modeling Studies onducted Within the International DECOVALEX Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

J.T. Birkholzer; J. Rutqvist; E.L. Sonnenthal

2006-02-01

The DECOVALEX project is an international cooperative project initiated by SKI, the Swedish Nuclear Power Inspectorate, with participation of about 10 international organizations. The general goal of this project is to encourage multidisciplinary interactive and cooperative research on modeling coupled thermo-hydro-mechanical-chemical (THMC) processes in geologic formations in support of the performance assessment for underground storage of radioactive waste. One of the research tasks, initiated in 2004 by the U.S. Department of Energy (DOE), addresses the long-term impact of geomechanical and geochemical processes on the flow conditions near waste emplacement tunnels. Within this task, four international research teams conduct predictive analysismore » of the coupled processes in two generic repositories, using multiple approaches and different computer codes. Below, we give an overview of the research task and report its current status.« less

Application of cluster analysis to geochemical compositional data for identifying ore-related geochemical anomalies

NASA Astrophysics Data System (ADS)

Zhou, Shuguang; Zhou, Kefa; Wang, Jinlin; Yang, Genfang; Wang, Shanshan

2017-12-01

Cluster analysis is a well-known technique that is used to analyze various types of data. In this study, cluster analysis is applied to geochemical data that describe 1444 stream sediment samples collected in northwestern Xinjiang with a sample spacing of approximately 2 km. Three algorithms (the hierarchical, k-means, and fuzzy c-means algorithms) and six data transformation methods (the z-score standardization, ZST; the logarithmic transformation, LT; the additive log-ratio transformation, ALT; the centered log-ratio transformation, CLT; the isometric log-ratio transformation, ILT; and no transformation, NT) are compared in terms of their effects on the cluster analysis of the geochemical compositional data. The study shows that, on the one hand, the ZST does not affect the results of column- or variable-based (R-type) cluster analysis, whereas the other methods, including the LT, the ALT, and the CLT, have substantial effects on the results. On the other hand, the results of the row- or observation-based (Q-type) cluster analysis obtained from the geochemical data after applying NT and the ZST are relatively poor. However, we derive some improved results from the geochemical data after applying the CLT, the ILT, the LT, and the ALT. Moreover, the k-means and fuzzy c-means clustering algorithms are more reliable than the hierarchical algorithm when they are used to cluster the geochemical data. We apply cluster analysis to the geochemical data to explore for Au deposits within the study area, and we obtain a good correlation between the results retrieved by combining the CLT or the ILT with the k-means or fuzzy c-means algorithms and the potential zones of Au mineralization. Therefore, we suggest that the combination of the CLT or the ILT with the k-means or fuzzy c-means algorithms is an effective tool to identify potential zones of mineralization from geochemical data.

Geochemical modeling of reactions and partitioning of trace metals and radionuclides during titration of contaminated acidic sediments.

PubMed

Zhang, Fan; Luo, Wensui; Parker, Jack C; Spalding, Brian P; Brooks, Scott C; Watson, David B; Jardine, Philip M; Gu, Baohua

2008-11-01

Many geochemical reactions that control aqueous metal concentrations are directly affected by solution pH. However, changes in solution pH are strongly buffered by various aqueous phase and solid phase precipitation/dissolution and adsorption/desorption reactions. The ability to predict acid-base behavior of the soil-solution system is thus critical to predict metal transport under variable pH conditions. This studywas undertaken to develop a practical generic geochemical modeling approach to predict aqueous and solid phase concentrations of metals and anions during conditions of acid or base additions. The method of Spalding and Spalding was utilized to model soil buffer capacity and pH-dependent cation exchange capacity by treating aquifer solids as a polyprotic acid. To simulate the dynamic and pH-dependent anion exchange capacity, the aquifer solids were simultaneously treated as a polyprotic base controlled by mineral precipitation/ dissolution reactions. An equilibrium reaction model that describes aqueous complexation, precipitation, sorption and soil buffering with pH-dependent ion exchange was developed using HydroGeoChem v5.0 (HGC5). Comparison of model results with experimental titration data of pH, Al, Ca, Mg, Sr, Mn, Ni, Co, and SO4(2-) for contaminated sediments indicated close agreement suggesting that the model could potentially be used to predictthe acid-base behavior of the sediment-solution system under variable pH conditions.

Predictions of hydrothermal alteration within near-ridge oceanic crust from coordinated geochemical and fluid flow models

USGS Publications Warehouse

Wetzel, L.R.; Raffensperger, Jeff P.; Shock, E.L.

2001-01-01

Coordinated geochemical and hydrological calculations guide our understanding of the composition, fluid flow patterns, and thermal structure of near-ridge oceanic crust. The case study presented here illustrates geochemical and thermal changes taking place as oceanic crust ages from 0.2 to 1.0 Myr. Using a finite element code, we model fluid flow and heat transport through the upper few hundred meters of an abyssal hill created at an intermediate spreading rate. We use a reaction path model with a customized database to calculate equilibrium fluid compositions and mineral assemblages of basalt and seawater at 500 bars and temperatures ranging from 150 to 400??C. In one scenario, reaction path calculations suggest that volume increases on the order of 10% may occur within portions of the basaltic basement. If this change in volume occurred, it would be sufficient to fill all primary porosity in some locations, effectively sealing off portions of the oceanic crust. Thermal profiles resulting from fluid flow simulations indicate that volume changes along this possible reaction path occur primarily within the first 0.4 Myr of crustal aging. ?? 2001 Elsevier Science B.V. All rights reserved.

Spectroscopy as a tool for geochemical modeling

NASA Astrophysics Data System (ADS)

Kopacková, Veronika; Chevrel, Stephane; Bourguignon, Anna

2011-11-01

This study focused on testing the feasibility of up-scaling ground-spectra-derived parameters to HyMap spectral and spatial resolution and whether they could be further used for a quantitative determination of the following geochemical parameters: As, pH and Clignite content. The study was carried on the Sokolov lignite mine as it represents a site with extreme material heterogeneity and high heavy-metal gradients. A new segmentation method based on the unique spectral properties of acid materials was developed and applied to the multi-line HyMap image data corrected for BRDF and atmospheric effects. The quantitative parameters were calculated for multiple absorption features identified within the VIS/VNIR/SWIR regions (simple band ratios, absorption band depth and quantitative spectral feature parameters calculated dynamically for each spectral measurement (centre of the absorption band (λ), depth of the absorption band (D), width of the absorption band (Width), and asymmetry of the absorption band (S)). The degree of spectral similarity between the ground and image spectra was assessed. The linear models for pH, As and the Clignite content of the whole and segmented images were cross-validated on the selected homogenous areas defined in the HS images using ground truth. For the segmented images, reliable results were achieved as follows: As: R2=0.84, Clignite: R2=0.88 and R2 pH: R2= 0.57.

Micromechanical Tests and Geochemical Modeling to Evaluate Evolution of Rock Alteration by CO2-Water Mixtures

NASA Astrophysics Data System (ADS)

Aman, M.; Sun, Y.; Ilgen, A.; Espinoza, N.

2015-12-01

Injection of large volumes of CO2 into geologic formations can help reduce the atmospheric CO2 concentration and lower the impact of burning fossil fuels. However, the injection of CO2 into the subsurface shifts the chemical equilibrium between the mineral assemblage and the pore fluid. This shift will situationally facilitate dissolution and reprecipitation of mineral phases, in particular intergranular cements, and can potentially affect the long term mechanical stability of the host formation. The study of these coupled chemical-mechanical reservoir rock responses can help identify and control unexpected emergent behavior associated with geological CO2 storage.Experiments show that micro-mechanical methods are useful in capturing a variety of mechanical parameters, including Young's modulus, hardness and fracture toughness. In particular, micro-mechanical measurements are well-suited for examining thin altered layers on the surfaces of rock specimens, as well as capturing variability on the scale of lithofacies. We performed indentation and scratching tests on sandstone and siltstone rocks altered in natural CO2-brine environments, as well as on analogous samples altered under high pressure, temperature, and dissolved CO2 conditions in a controlled laboratory experiment. We performed geochemical modeling to support the experimental observations, in particular to gain the insight into mineral dissolution/precipitation as a result of the rock-water-CO2reactions. The comparison of scratch measurements performed on specimens both unaltered and altered by CO2 over geologic time scales results in statistically different values for fracture toughness and scratch hardness, indicating that long term exposure to CO2 caused mechanical degradation of the reservoir rock. Geochemical modeling indicates that major geochemical change caused by CO2 invasion of Entrada sandstone is dissolution of hematite cement, and its replacement with siderite and dolomite during the

Integration of Geophysical and Geochemical Data

NASA Astrophysics Data System (ADS)

Yamagishi, Y.; Suzuki, K.; Tamura, H.; Nagao, H.; Yanaka, H.; Tsuboi, S.

2006-12-01

Integration of geochemical and geophysical data would give us a new insight to the nature of the Earth. It should advance our understanding for the dynamics of the Earth's interior and surface processes. Today various geochemical and geophysical data are available on Internet. These data are stored in various database systems. Each system is isolated and provides own format data. The goal of this study is to display both the geochemical and geophysical data obtained from such databases together visually. We adopt Google Earth as the presentation tool. Google Earth is virtual globe software and is provided free of charge by Google, Inc. Google Earth displays the Earth's surface using satellite images with mean resolution of ~15m. We display any graphical features on Google Earth by KML format file. We have developed softwares to convert geochemical and geophysical data to KML file. First of all, we tried to overlay data from Georoc and PetDB and seismic tomography data on Google Earth. Georoc and PetDB are both online database systems for geochemical data. The data format of Georoc is CSV and that of PetDB is Microsoft Excel. The format of tomography data we used is plain text. The conversion software can process these different file formats. The geochemical data (e. g. compositional abundance) is displayed as a three-dimensional column on the Earth's surface. The shape and color of the column mean the element type. The size and color tone vary according to the abundance of the element. The tomography data can be converted into a KML file for each depth. This overlay plot of geochemical data and tomography data should help us to correlate internal temperature anomalies to geochemical anomalies, which are observed at the surface of the Earth. Our tool can convert any geophysical and geochemical data to a KML as long as the data is associated with longitude and latitude. We are going to support more geophysical data formats. In addition, we are currently trying to

Backfilling-Free Strategy for Biopatterning on Intrinsically Dual-Functionalized Poly[2-Aminoethyl Methacrylate-co-Oligo(Ethylene Glycol) Methacrylate] Films.

PubMed

Lee, Bong Soo; Lee, Juno; Han, Gyeongyeop; Ha, EunRae; Choi, Insung S; Lee, Jungkyu K

2016-07-20

We demonstrated protein and cellular patterning with a soft lithography technique using poly[2-aminoethyl methacrylate-co-oligo(ethylene glycol) methacrylate] films on gold surfaces without employing a backfilling process. The backfilling process plays an important role in successfully generating biopatterns; however, it has potential disadvantages in several interesting research and technical applications. To overcome the issue, a copolymer system having highly reactive functional groups and bioinert properties was introduced through a surface-initiated controlled radical polymerization with 2-aminoethyl methacrylate hydrochloride (AMA) and oligo(ethylene glycol) methacrylate (OEGMA). The prepared poly(AMA-co-OEGMA) film was fully characterized, and among the films having different thicknesses, the 35 nm-thick biotinylated, poly(AMA-co-OEGMA) film exhibited an optimum performance, such as the lowest nonspecific adsorption and the highest specific binding capability toward proteins. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Use of cemented paste backfill in arsenic-rich tailings

NASA Astrophysics Data System (ADS)

Hamberg, Roger; Maurice, Christian; Alakangas, Lena

2015-04-01

Gold is extracted by cyanide leaching from inclusions in arsenopyrite from a mine in the north of Sweden. The major ore mineral assemblage consists of pyrrhotite and arsenopyrite-loellingite. Effluents from the gold extraction were treated with Fe2(SO4)3, with the aim to form stable As-bearing Fe-precipitates (FEP). The use of the method called cemented paste backfill (CPB) is sometimes suggested for the management of tailings. In CPB, tailings are commonly mixed with low proportions (3 - 7 %) of cement and backfilled into underground excavated area. To reduce costs, amendments such as granulated blast furnace slag (GBFS), biofuel fly ash (BFA) and cement kiln dust (CKD) are used for partial replacement of cement in CPB due to their pozzolanic and alkaline properties. The objective for this study was to evaluate the leaching behaviour of As in CPB-mixtures with low proportions (1 - 3 %) of BFA and ordinary cement and unmodified tailings. The selection of CPB-recipies was made based on technical and economical criterias to adress the demands deriving from the mining operations. Speciation of the As in ore and tailings samples revealed that mining processes have dissolved the majority of the arsenopyrite in the ore, causing secondary As phases to co-precipitate with newly formed FEP:s. Tank leaching tests (TLT) and weathering cells (WCT) were used to compare leaching behaviour in a monolithic mass contra a crushed material. Quantification of the presumed benefit of CPB was made by calculation of the cumulative leaching of As. Results from the leaching tests (TLT and WCT) showed that the inclusion of As-rich tailings into a cementitious matrix increased leaching of As. This behaviour could partially be explained by an increase of pH. The addition of alkaline binder materials to tailings increased As leaching due to the relocation of desorbed As from FEPs into less acid-tolerant species such as Ca-arsenates and cementitious As-phases. Unmodified tailings generated an

Geochemical Modeling of Reactions and Partitioning of Trace Metals and Radionuclides during Titration of Contaminated Acidic Sediments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Fan; Parker, Jack C.; Luo, Wensui

2008-01-01

Many geochemical reactions that control aqueous metal concentrations are directly affected by solution pH. However, changes in solution pH are strongly buffered by various aqueous phase and solid phase precipitation/dissolution and adsorption/desorption reactions. The ability to predict acid-base behavior of the soil-solution system is thus critical to predict metal transport under variable pH conditions. This study was undertaken to develop a practical generic geochemical modeling approach to predict aqueous and solid phase concentrations of metals and anions during conditions of acid or base additions. The method of Spalding and Spalding was utilized to model soil buffer capacity and pH-dependent cationmore » exchange capacity by treating aquifer solids as a polyprotic acid. To simulate the dynamic and pH-dependent anion exchange capacity, the aquifer solids were simultaneously treated as a polyprotic base controlled by mineral precipitation/dissolution reactions. An equilibrium reaction model that describes aqueous complexation, precipitation, sorption and soil buffering with pH-dependent ion exchange was developed using HydroGeoChem v5.0 (HGC5). Comparison of model results with experimental titration data of pH, Al, Ca, Mg, Sr, Mn, Ni, Co, and SO{sub 4}{sup 2-} for contaminated sediments indicated close agreement, suggesting that the model could potentially be used to predict the acid-base behavior of the sediment-solution system under variable pH conditions.« less

Geochemical Data Package for Performance Assessment Calculations Related to the Savannah River Site

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaplan, Daniel I.

The Savannah River Site (SRS) disposes of low-level radioactive waste (LLW) and stabilizes high-level radioactive waste (HLW) tanks in the subsurface environment. Calculations used to establish the radiological limits of these facilities are referred to as Performance Assessments (PA), Special Analyses (SA), and Composite Analyses (CA). The objective of this document is to revise existing geochemical input values used for these calculations. This work builds on earlier compilations of geochemical data (2007, 2010), referred to a geochemical data packages. This work is being conducted as part of the on-going maintenance program of the SRS PA programs that periodically updates calculationsmore » and data packages when new information becomes available. Because application of values without full understanding of their original purpose may lead to misuse, this document also provides the geochemical conceptual model, the approach used for selecting the values, the justification for selecting data, and the assumptions made to assure that the conceptual and numerical geochemical models are reasonably conservative (i.e., bias the recommended input values to reflect conditions that will tend to predict the maximum risk to the hypothetical recipient). This document provides 1088 input parameters for geochemical parameters describing transport processes for 64 elements (>740 radioisotopes) potentially occurring within eight subsurface disposal or tank closure areas: Slit Trenches (ST), Engineered Trenches (ET), Low Activity Waste Vault (LAWV), Intermediate Level (ILV) Vaults, Naval Reactor Component Disposal Areas (NRCDA), Components-in-Grout (CIG) Trenches, Saltstone Facility, and Closed Liquid Waste Tanks. The geochemical parameters described here are the distribution coefficient, Kd value, apparent solubility concentration, k s value, and the cementitious leachate impact factor.« less

Geochemical modeling of leaching of Ca, Mg, Al, and Pb from cementitious waste forms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martens, E., E-mail: evelien.martens@csiro.a; Jacques, D.; Van Gerven, T.

2010-08-15

Results from extraction tests on cement-waste samples were simulated with a thermodynamic equilibrium model using a consistent database, to which lead data were added. Subsequent diffusion tests were modeled by means of a 3D diffusive transport model combined with the geochemical model derived from the extraction tests. Modeling results of the leached major element concentrations for both uncarbonated and (partially) carbonated samples agreed well with the extraction test using the set of pure minerals and solid solutions present in the database. The observed decrease in Ca leaching with increasing carbonation level was qualitatively predicted. Simulations also revealed that Pb leachingmore » is not controlled by dissolution/precipitation only. The addition of the calcite-cerrusite solid solution and adsorption reactions on amorphous Fe- and Al-oxides improved the predictions and are considered to control the Pb leaching during the extractions tests. The dynamic diffusive leaching tests were appropriately modeled for Na, K, Ca and Pb.« less

10 CFR 963.17 - Postclosure suitability criteria.

Code of Federal Regulations, 2014 CFR

2014-01-01

...) Near field geochemical environment—for example, the chemical reactions and products resulting from... probability and potential consequences of a self-sustaining nuclear reaction as a result of chemical or..., drip shields, backfill, coatings, or chemical modifications, and (ii) Waste package degradation—for...

10 CFR 963.17 - Postclosure suitability criteria.

Code of Federal Regulations, 2012 CFR

2012-01-01

...) Near field geochemical environment—for example, the chemical reactions and products resulting from... probability and potential consequences of a self-sustaining nuclear reaction as a result of chemical or..., drip shields, backfill, coatings, or chemical modifications, and (ii) Waste package degradation—for...

10 CFR 963.17 - Postclosure suitability criteria.

Code of Federal Regulations, 2010 CFR

2010-01-01

...) Near field geochemical environment—for example, the chemical reactions and products resulting from... probability and potential consequences of a self-sustaining nuclear reaction as a result of chemical or..., drip shields, backfill, coatings, or chemical modifications, and (ii) Waste package degradation—for...

10 CFR 963.17 - Postclosure suitability criteria.

Code of Federal Regulations, 2013 CFR

2013-01-01

...) Near field geochemical environment—for example, the chemical reactions and products resulting from... probability and potential consequences of a self-sustaining nuclear reaction as a result of chemical or..., drip shields, backfill, coatings, or chemical modifications, and (ii) Waste package degradation—for...

10 CFR 963.17 - Postclosure suitability criteria.

Code of Federal Regulations, 2011 CFR

2011-01-01

...) Near field geochemical environment—for example, the chemical reactions and products resulting from... probability and potential consequences of a self-sustaining nuclear reaction as a result of chemical or..., drip shields, backfill, coatings, or chemical modifications, and (ii) Waste package degradation—for...

Detecting and Quantifying Paleoseasonality in Stalagmites using Geochemical and Modelling Approaches

NASA Astrophysics Data System (ADS)

Baldini, J. U. L.

2017-12-01

Stalagmites are now well established sources of terrestrial paleoclimate information, providing insights into climate change on a variety of timescales. One of the most exciting aspects of stalagmites as climate archives is their ability to provide information regarding seasonality, a notoriously difficult component of climate change to characterise. However, stalagmite geochemistry may reflect not only the most apparent seasonal signal in external climate parameters, but also cave-specific signals such as seasonal changes in cave air carbon dioxide concentrations, sudden shifts in ventilation, and stochastic hydrological processes. Additionally, analytical bias may dampen or completely obfuscate any paleoseasonality, highlighting the need for appropriate quantification of this issue using simple models. Evidence from stalagmites now suggests that a seasonal signal is extractable from many samples, and that this signal can provide an important extra dimension to paleoclimate interpretations. Additionally, lower resolution annual- to decadal-scale isotope ratio records may also reflect shifts in seasonality, but identifying these is often challenging. Integrating geochemical datasets with models and cave monitoring data can greatly increase the accuracy of climate reconstructions, and yield the most robust records.

Biological reduction of chlorinated solvents: Batch-scale geochemical modeling

NASA Astrophysics Data System (ADS)

Kouznetsova, Irina; Mao, Xiaomin; Robinson, Clare; Barry, D. A.; Gerhard, Jason I.; McCarty, Perry L.

2010-09-01

Simulation of biodegradation of chlorinated solvents in dense non-aqueous phase liquid (DNAPL) source zones requires a model that accounts for the complexity of processes involved and that is consistent with available laboratory studies. This paper describes such a comprehensive modeling framework that includes microbially mediated degradation processes, microbial population growth and decay, geochemical reactions, as well as interphase mass transfer processes such as DNAPL dissolution, gas formation and mineral precipitation/dissolution. All these processes can be in equilibrium or kinetically controlled. A batch modeling example was presented where the degradation of trichloroethene (TCE) and its byproducts and concomitant reactions (e.g., electron donor fermentation, sulfate reduction, pH buffering by calcite dissolution) were simulated. Local and global sensitivity analysis techniques were applied to delineate the dominant model parameters and processes. Sensitivity analysis indicated that accurate values for parameters related to dichloroethene (DCE) and vinyl chloride (VC) degradation (i.e., DCE and VC maximum utilization rates, yield due to DCE utilization, decay rate for DCE/VC dechlorinators) are important for prediction of the overall dechlorination time. These parameters influence the maximum growth rate of the DCE and VC dechlorinating microorganisms and, thus, the time required for a small initial population to reach a sufficient concentration to significantly affect the overall rate of dechlorination. Self-inhibition of chlorinated ethenes at high concentrations and natural buffering provided by the sediment were also shown to significantly influence the dechlorination time. Furthermore, the analysis indicated that the rates of the competing, nonchlorinated electron-accepting processes relative to the dechlorination kinetics also affect the overall dechlorination time. Results demonstrated that the model developed is a flexible research tool that is

Porosity Development in a Coastal Setting: A Reactive Transport Model to Assess the Influence of Heterogeneity of Hydrological, Geochemical and Lithological Conditions

NASA Astrophysics Data System (ADS)

Maqueda, A.; Renard, P.; Cornaton, F. J.

2014-12-01

Coastal karst networks are formed by mineral dissolution, mainly calcite, in the freshwater-saltwater mixing zone. The problem has been approached first by studying the kinetics of calcite dissolution and then coupling ion-pairing software with flow and mass transport models. Porosity development models require high computational power. A workaround to reduce computational complexity is to assume the calcite dissolution reaction is relatively fast, thus equilibrium chemistry can be used to model it (Sanford & Konikow, 1989). Later developments allowed the full coupling of kinetics and transport in a model. However kinetics effects of calcite dissolution were found negligible under the single set of assumed hydrological and geochemical boundary conditions. A model is implemented with the coupling of FeFlow software as the flow & transport module and PHREEQC4FEFLOW (Wissmeier, 2013) ion-pairing module. The model is used to assess the influence of heterogeneities in hydrological, geochemical and lithological boundary conditions on porosity evolution. The hydrologic conditions present in the karst aquifer of Quintana Roo coast in Mexico are used as a guide for generating inputs for simulations.

A Comparison of Methods for Modeling Geochemical Variability in the Earth's Mantle

NASA Astrophysics Data System (ADS)

Kellogg, J. B.; Tackley, P. J.

2004-12-01

Numerial models of isotopic and chemical heterogeneity of the Earth's mantle fall into three categories, in decreasing order of computational demand. First, several authors have used chemical tracers within a full thermo-chemical convection calculation (e.g., Christensen and Hofmann, 1994, van Keken and Ballentine, 1999; Xie and Tackley, 2004). Second, Kellogg et al. (2002) proposed an extension of the traditional geochemical box model calculations in which numerous subreservoirs were tracked within the bulk depleted mantle reservoir. Third, Allègre and Lewin (1995) described a framework in which the variance in chemical and isotopic ratios were treated as quantities intrinsic to the bulk reservoirs, complete with sources and sinks. Results from these three methods vary, particularly with respect to conclusions drawn about the meaning of the Pb-Pb pseudo-isochron. We revisit these methods in an attempt to arrive at a common understanding. By considering all three we better identify the strengths and weaknesses of each approach and allow each to inform the other. Finally, we present results from a new hybrid model that combines the complexity and regional-scale variability of the thermochemical convection models with the short length-scale sensitivity of the Kellogg et al. approach.

Community-Based Development of Standards for Geochemical and Geochronological Data

NASA Astrophysics Data System (ADS)

Lehnert, K. A.; Walker, D.; Vinay, S.; Djapic, B.; Ash, J.; Falk, B.

2007-12-01

The Geoinformatics for Geochemistry (GfG) Program (www.geoinfogeochem.org) and the EarthChem project (www.earthchem.org) aim to maximize the application of geochemical data in Geoscience research and education by building a new advanced data infrastructure for geochemistry that facilitates the compilation, communication, serving, and visualization of geochemical data and their integration with the broad Geoscience data set. Building this new data infrastructure poses substantial challenges that are primarily cultural in nature, and require broad community involvement in the development and implementation of standards for data reporting (e.g., metadata for analytical procedures, data quality, and analyzed samples), data publication, and data citation to achieve broad acceptance and use. Working closely with the science community, with professional societies, and with editors and publishers, recommendations for standards for the reporting of geochemical and geochronological data in publications and to data repositories have been established, which are now under consideration for adoption in journal and agency policies. The recommended standards are aligned with the GfG and EarthChem data models as well as the EarthChem XML schema for geochemical data. Through partnerships with other national and international data management efforts in geochemistry and in the broader marine and terrestrial geosciences, GfG and EarthChem seek to integrate their development of geochemical metadata standards, data format, and semantics with relevant existing and emerging standards and ensure compatibility and compliance.

Hydrologic and geochemical data assimilation at the Hanford 300 Area

NASA Astrophysics Data System (ADS)

Chen, X.; Hammond, G. E.; Murray, C. J.; Zachara, J. M.

2012-12-01

In modeling the uranium migration within the Integrated Field Research Challenge (IFRC) site at the Hanford 300 Area, uncertainties arise from both hydrologic and geochemical sources. The hydrologic uncertainty includes the transient flow boundary conditions induced by dynamic variations in Columbia River stage and the underlying heterogeneous hydraulic conductivity field, while the geochemical uncertainty is a result of limited knowledge of the geochemical reaction processes and parameters, as well as heterogeneity in uranium source terms. In this work, multiple types of data, including the results from constant-injection tests, borehole flowmeter profiling, and conservative tracer tests, are sequentially assimilated across scales within a Bayesian framework to reduce the hydrologic uncertainty. The hydrologic data assimilation is then followed by geochemical data assimilation, where the goal is to infer the heterogeneous distribution of uranium sources using uranium breakthrough curves from a desorption test that took place at high spring water table. We demonstrate in our study that Ensemble-based data assimilation techniques (Ensemble Kalman filter and smoother) are efficient in integrating multiple types of data sequentially for uncertainty reduction. The computational demand is managed by using the multi-realization capability within the parallel PFLOTRAN simulator.

SilMush: A procedure for modeling of the geochemical evolution of silicic magmas and granitic rocks

NASA Astrophysics Data System (ADS)

Hertogen, Jan; Mareels, Joyce

2016-07-01

A boundary layer crystallization modeling program is presented that specifically addresses the chemical fractionation in silicic magma systems and the solidification of plutonic bodies. The model is a Langmuir (1989) type approach and does not invoke crystal settling in high-viscosity silicic melts. The primary aim is to model a granitic rock as a congealed crystal-liquid mush, and to integrate major element and trace element modeling. The procedure allows for some exploratory investigation of the exsolution of H2O-fluids and of the fluid/melt partitioning of trace elements. The procedure is implemented as a collection of subroutines for the MS Excel spreadsheet environment and is coded in the Visual Basic for Applications (VBA) language. To increase the flexibility of the modeling, the procedure is based on discrete numeric process simulation rather than on solution of continuous differential equations. The program is applied to a study of the geochemical variation within and among three granitic units (Senones, Natzwiller, Kagenfels) from the Variscan Northern Vosges Massif, France. The three units cover the compositional range from monzogranite, over syenogranite to alkali-feldspar granite. An extensive set of new major element and trace element data is presented. Special attention is paid to the essential role of accessory minerals in the fractionation of the Rare Earth Elements. The crystallization model is able to reproduce the essential major and trace element variation trends in the data sets of the three separate granitic plutons. The Kagenfels alkali-feldspar leucogranite couples very limited variation in major element composition to a considerable and complex variation of trace elements. The modeling results can serve as a guide for the reconstruction of the emplacement sequence of petrographically distinct units. Although the modeling procedure essentially deals with geochemical fractionation within a single pluton, the modeling results bring up a

Magma transport and metasomatism in the mantle: a critical review of current geochemical models

USGS Publications Warehouse

Nielson, J.E.; Wilshire, H.G.

1993-01-01

Conflicting geochemical models of metasomatic interactions between mantle peridotite and melt all assume that mantle reactions reflect chromatographic processes. Examination of field, petrological, and compositional data suggests that the hypothesis of chromatographic fractionation based on the supposition of large-scale percolative processes needs review and revision. Well-constrained rock and mineral data from xenoliths indicate that many elements that behave incompatibly in equilibrium crystallization processes are absorbed immediately when melts emerge from conduits into depleted peridotite. After reacting to equilibrium with the peridotite, melt that percolates away from the conduit is largely depleted of incompatible elements. Continued addition of melts extends the zone of equilibrium farther from the conduit. Such a process resembles ion-exchange chromatography for H2O purification, rather than the model of chromatographic species separation. -from Authors

Performance of a Zerovalent Iron Reactive Barrier for the Treatment of Arsenic in Groundwater: Part 2. Geochemical Modeling and Solid Phase Studies

EPA Science Inventory

Arsenic uptake processes were evaluated in a zerovalent iron reactive barrier installed at a lead smelting facility using geochemical modeling, solid-phase analysis, and X-ray absorption spectroscopy techniques. Aqueous speciation of arsenic plays a key role in directing arsenic...

Long-term climate change and the geochemical cycle of carbon

NASA Technical Reports Server (NTRS)

Marshall, Hal G.; Walker, James C. G.; Kuhn, William R.

1988-01-01

The response of the coupled climate-geochemical system to changes in paleography is examined in terms of the biogeochemical carbon cycle. The simple, zonally averaged energy balance climate model combined with a geochemical carbon cycle model, which was developed to study climate changes, is described. The effects of latitudinal distributions of the continents on the carbon cycle are investigated, and the global silicate weathering rate as a function of latitude is measured. It is observed that a concentration of land area at high altitudes results in a high CO2 partial pressure and a high global average temperature, and for land at low latitudes a cold globe and ice are detected. It is noted that the CO2 greenhouse feedback effect is potentially strong and has a stabilizing effect on the climate system.

Geochemical Constraints on the Size of the Moon-Forming Giant Impact

NASA Astrophysics Data System (ADS)

Piet, Hélène; Badro, James; Gillet, Philippe

2017-12-01

Recent models involving the Moon-forming giant impact hypothesis have managed to reproduce the striking isotopic similarity between the two bodies, albeit using two extreme models: one involves a high-energy small impactor that makes the Moon out of Earth's proto-mantle; the other supposes a gigantic collision between two half-Earths creating the Earth-Moon system from both bodies. Here we modeled the geochemical influence of the giant impact on Earth's mantle and found that impactors larger than 15% of Earth mass result in mantles always violating the present-day concentrations of four refractory moderately siderophile trace elements (Ni, Co, Cr, and V). In the aftermath of the impact, our models cannot further discriminate between a fully and a partially molten bulk silicate Earth. Then, the preservation of primordial geochemical reservoirs predating the Moon remains the sole argument against a fully molten mantle after the Moon-forming impact.

Produced water re-injection in a non-fresh water aquifer with geochemical reaction, hydrodynamic molecular dispersion and adsorption kinetics controlling: model development and numerical simulation

NASA Astrophysics Data System (ADS)

Obe, Ibidapo; Fashanu, T. A.; Idialu, Peter O.; Akintola, Tope O.; Abhulimen, Kingsley E.

2017-06-01

An improved produced water reinjection (PWRI) model that incorporates filtration, geochemical reaction, molecular transport, and mass adsorption kinetics was developed to predict cake deposition and injectivity performance in hydrocarbon aquifers in Nigeria oil fields. Thus, the improved PWRI model considered contributions of geochemical reaction, adsorption kinetics, and hydrodynamic molecular dispersion mechanism to alter the injectivity and deposition of suspended solids on aquifer wall resulting in cake formation in pores during PWRI and transport of active constituents in hydrocarbon reservoirs. The injectivity decline and cake deposition for specific case studies of hydrocarbon aquifers in Nigeria oil fields were characterized with respect to its well geometry, lithology, and calibrations data and simulated in COMSOL multiphysics software environment. The PWRI model was validated by comparisons to assessments of previous field studies based on data and results supplied by operator and regulator. The results of simulation showed that PWRI performance was altered because of temporal variations and declinations of permeability, injectivity, and cake precipitation, which were observed to be dependent on active adsorption and geochemical reaction kinetics coupled with filtration scheme and molecular dispersion. From the observed results and findings, transition time t r to cake nucleation and growth were dependent on aquifer constituents, well capacity, filtration coefficients, particle-to-grain size ratio, water quality, and more importantly, particle-to-grain adsorption kinetics. Thus, the results showed that injectivity decline and permeability damage were direct contributions of geochemical reaction, hydrodynamic molecular diffusion, and adsorption kinetics to the internal filtration mechanism, which are largely dependent on the initial conditions of concentration of active constituents of produced water and aquifer capacity.

Geochemical modeling of magma mixing and magma reservoir volumes during early episodes of Kīlauea Volcano's Pu`u `Ō`ō eruption

NASA Astrophysics Data System (ADS)

Shamberger, Patrick J.; Garcia, Michael O.

2007-02-01

Geochemical modeling of magma mixing allows for evaluation of volumes of magma storage reservoirs and magma plumbing configurations. A new analytical expression is derived for a simple two-component box-mixing model describing the proportions of mixing components in erupted lavas as a function of time. Four versions of this model are applied to a mixing trend spanning episodes 3 31 of Kilauea Volcano’s Puu Oo eruption, each testing different constraints on magma reservoir input and output fluxes. Unknown parameters (e.g., magma reservoir influx rate, initial reservoir volume) are optimized for each model using a non-linear least squares technique to fit model trends to geochemical time-series data. The modeled mixing trend closely reproduces the observed compositional trend. The two models that match measured lava effusion rates have constant magma input and output fluxes and suggest a large pre-mixing magma reservoir (46±2 and 49±1 million m3), with little or no volume change over time. This volume is much larger than a previous estimate for the shallow, dike-shaped magma reservoir under the Puu Oo vent, which grew from ˜3 to ˜10 12 million m3. These volumetric differences are interpreted as indicating that mixing occurred first in a larger, deeper reservoir before the magma was injected into the overlying smaller reservoir.

Use of partial dissolution techniques in geochemical exploration

USGS Publications Warehouse

Chao, T.T.

1984-01-01

Application of partial dissolution techniques to geochemical exploration has advanced from an early empirical approach to an approach based on sound geochemical principles. This advance assures a prominent future position for the use of these techniques in geochemical exploration for concealed mineral deposits. Partial dissolution techniques are classified as single dissolution or sequential multiple dissolution depending on the number of steps taken in the procedure, or as "nonselective" extraction and as "selective" extraction in terms of the relative specificity of the extraction. The choice of dissolution techniques for use in geochemical exploration is dictated by the geology of the area, the type and degree of weathering, and the expected chemical forms of the ore and of the pathfinding elements. Case histories have illustrated many instances where partial dissolution techniques exhibit advantages over conventional methods of chemical analysis used in geochemical exploration. ?? 1984.

Use of sediment-trace element geochemical models for the identification of local fluvial baseline concentrations

USGS Publications Warehouse

Horowitz, A.J.; Elrick, K.A.; Demas, C.R.; Demcheck, D.K.

1991-01-01

Studies have demonstrated the utility of fluvial bed sediment chemical data in assesing local water-quality conditions. However, establishing local background trace element levels can be difficult. Reference to published average concentrations or the use of dated cores are often of little use in small areas of diverse local petrology, geology, land use, or hydrology. An alternative approach entails the construction of a series of sediment-trace element predictive models based on data from environmentally diverse but unaffected areas. Predicted values could provide a measure of local background concentrations and comparison with actual measured concentrations could identify elevated trace elements and affected sites. Such a model set was developed from surface bed sediments collected nationwide in the United States. Tests of the models in a small Louisiana basin indicated that they could be used to establish local trace element background levels, but required recalibration to account for local geochemical conditions outside the range of samples used to generate the nationwide models.

VIRUS TRANSPORT IN PHYSICALLY AND GEOCHEMICALLY HETEROGENEOUS SUBSURFACE POROUS MEDIA. (R826179)

EPA Science Inventory

A two-dimensional model for virus transport in physically and geochemically heterogeneous subsurface porous media is presented. The model involves solution of the advection–dispersion equation, which additionally considers virus inactivation in the solution, as well as ...

Reactive Transport of Petroleum Hydrocarbon Constituents in a Shallow Aquifer: Modeling Geochemical Interactions Between Organic and Inorganic Species

NASA Astrophysics Data System (ADS)

McNab, W. W.; Narasimhan, T. N.

1995-08-01

Dissolved organic contaminants such as petroleum hydrocarbon constituents are often observed to degrade in groundwater environments through biologically mediated transformation reactions into carbon dioxide, methane, or intermediate organic compounds. Such transformations are closely tied to local geochemical conditions. Favorable degradation pathways depend upon local redox conditions through thermodynamic constraints and the availability of appropriate mediating microbial populations. Conversely, the progress of the degradation reactions may affect the chemical composition of groundwater through changes in electron donor/acceptor speciation and pH, possibly inducing mineral precipitation/dissolution reactions. Transport of reactive organic and inorganic aqueous species through open systems may enhance the reaction process by mixing unlike waters and producing a state of general thermodynamic disequilibrium. In this study, field data from an aquifer contaminated by petroleum hydrocarbons have been analyzed using a mathematical model which dynamically couples equilibrium geochemistry of inorganic constituents, kinetically dominated sequential degradation of organic compounds, and advective-dispersive chemical transport. Simulation results indicate that coupled geochemical processes inferred from field data, such as organic biodegradation, iron reduction and dissolution, and methanogenesis, can be successfully modeled using a partial-redox-disequilibrium approach. The results of this study also suggest how the modeling approach can be used to study system sensitivity to various physical and chemical parameters, such as the effect of dispersion on the position of chemical fronts and the impact of alternative buffering mineral phases (e.g., goethite versus amorphous Fe(OH)3) on water chemistry.

PHREEQCI; a graphical user interface for the geochemical computer program PHREEQC

USGS Publications Warehouse

Charlton, Scott R.; Macklin, Clifford L.; Parkhurst, David L.

1997-01-01

PhreeqcI is a Windows-based graphical user interface for the geochemical computer program PHREEQC. PhreeqcI provides the capability to generate and edit input data files, run simulations, and view text files containing simulation results, all within the framework of a single interface. PHREEQC is a multipurpose geochemical program that can perform speciation, inverse, reaction-path, and 1D advective reaction-transport modeling. Interactive access to all of the capabilities of PHREEQC is available with PhreeqcI. The interface is written in Visual Basic and will run on personal computers under the Windows(3.1), Windows95, and WindowsNT operating systems.

The evolution of the magmatic arc of Southern Peru (200-60 Ma), Arequipa area: insight from geochemical modeling

NASA Astrophysics Data System (ADS)

Demouy, S.; Benoit, M.; De Saint Blanquat, M.; Brunet, P.

2012-12-01

Cordilleran-type batholiths are built by prolonged arc activity along continental margins and may provide detailed magmatic records of the subduction system evolution. The magmas produced in subduction context involve both mantellic and crustal end members and are subject to various petrological processes. The MASH zones (Hildreth and Moorbath, 1988), at the basis of the continental crust, are the best places for the genesis of such hybrid magmas. The various geochemical signatures observed in the plutonic rocks, may also be attributed to source heterogeneities or generated by subsequent petrological processes. This study has focused in the Arequipa section of the Coastal Batholith of Southern Peru (200-60 Ma), in an area extending over 80x40 km. Major and trace elements as well as Sr and Nd isotopic analyses were performed in a set of 100 samples ranging from gabbro to granite. The obtained data highlight the wide heterogeneity of the geochemical signatures that is not related to the classification of the rocks. In first step, Rb/Sr systematic was used to isolate a set of samples plotting along a Paleocene isochron and defining a cogenetic suite. This suite appears to have evolved by simple fractional crystallization. By using reverse modeling, the parameters controlling the fractional crystallization process were defined, as partition coefficients, initial concentrations and amount of fractional crystallization. The other magmatic suites display a wide range of isotopic and geochemical signatures. To explain this heterogeneity, a model involving competition between fractional crystallization and magma mixing into MASH zones was proposed. A large range of hybrid magma types is potentially generated during the maturation of the system, but this range tends to disappear as fractionation and mixing occurs. Finally the model predicts the genesis of a homogeneous reservoir created at depth, from which magmas may evolve only by fractional crystallization. Therefore

A geochemical model of the Platanares geothermal system, Honduras

USGS Publications Warehouse

Janik, C.J.; Truesdell, A.H.; Goff, F.; Shevenell, L.; Stallard, M.L.; Trujillo, P.E.; Counce, D.

1991-01-01

Results of exploration drilling combined with results of geologic, geophysical, and hydrogeochemical investigations have been used to construct a geochemical model of the Platanares geothermal system, Honduras. Three coreholes were drilled, two of which produced fluids from fractured Miocene andesite and altered Cretaceous to Eocene conglomerate at 450 to 680 m depth. Large volume artesian flows of 160-165??C, predominantly bicarbonate water are chemically similar to, but slightly less saline than widespread boiling hot-spring waters. The chemistry of the produced fluid is dominated by equilibrium reactions in sedimentary rocks at greater depths and higher temperatures than those measured in the wells. Chemical, isotope, and gas geothermometers indicate a deep fluid temperature of 200-245??C and reflect a relatively short residence time in the fractures feeding the wells. Chloride-enthalpy relations as well as isotopic and chemical compositions of well discharges, thermal springs, and local cold waters support a conceptual model of ascending high-temperature (minimum 225??C) parent fluid that has cooled conductively to form the 160-165??C shallow (to 680 m) fluid encountered by the wells. The hot-spring waters are formed by boiling and steam loss from more or less conductively cooled parent fluid. The more dilute boiling spring waters (Cl = ???32 mg/kg) have cooled from > 225??C to about 160??C by conduction and from 160??C to 98??C by boiling. The most concentrated boiling spring waters (Cl = 37 mg/kg) have cooled from > 225??C to about 200??C by conduction and from 200??C to 98??C by boiling. Intermediate concentrations reflect mixed cooling paths. ?? 1991.

Novel use of geochemical models in evaluating treatment trains for aqueous radioactive waste streams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abitz, R.J.

1996-12-31

Thermodynamic geochemical models have been applied to assess the relative effectiveness of a variety of reagents added to aqueous waste streams for the removal of radioactive elements. Two aqueous waste streams were examined: effluent derived from the processing of uranium ore and irradiated uranium fuel rods. Simulations of the treatment train were performed to estimate the mass of reagents needed per kilogram of solution, identify pH regions corresponding to solubility minimums, and predict the identity and quantity of precipitated solids. Results generated by the simulations include figures that chart the chemical evolution of the waste stream as reagents are addedmore » and summary tables that list mass balances for all reagents and radioactive elements of concern. Model results were used to set initial reagent levels for the treatment trains, minimizing the number of bench-scale tests required to bring the treatment train up to full-scale operation. Additionally, presentation of modeling results at public meetings helps to establish good faith between the federal government, industry, concerned citizens, and media groups. 18 refs., 3 figs., 1 tab.« less

The IUGS/IAGC Task Group on Global Geochemical Baselines

USGS Publications Warehouse

Smith, David B.; Wang, Xueqiu; Reeder, Shaun; Demetriades, Alecos

2012-01-01

The Task Group on Global Geochemical Baselines, operating under the auspices of both the International Union of Geological Sciences (IUGS) and the International Association of Geochemistry (IAGC), has the long-term goal of establishing a global geochemical database to document the concentration and distribution of chemical elements in the Earth’s surface or near-surface environment. The database and accompanying element distribution maps represent a geochemical baseline against which future human-induced or natural changes to the chemistry of the land surface may be recognized and quantified. In order to accomplish this long-term goal, the activities of the Task Group include: (1) developing partnerships with countries conducting broad-scale geochemical mapping studies; (2) providing consultation and training in the form of workshops and short courses; (3) organizing periodic international symposia to foster communication among the geochemical mapping community; (4) developing criteria for certifying those projects whose data are acceptable in a global geochemical database; (5) acting as a repository for data collected by those projects meeting the criteria for standardization; (6) preparing complete metadata for the certified projects; and (7) preparing, ultimately, a global geochemical database. This paper summarizes the history and accomplishments of the Task Group since its first predecessor project was established in 1988.

Singularity analysis based on wavelet transform of fractal measures for identifying geochemical anomaly in mineral exploration

NASA Astrophysics Data System (ADS)

Chen, Guoxiong; Cheng, Qiuming

2016-02-01

Multi-resolution and scale-invariance have been increasingly recognized as two closely related intrinsic properties endowed in geofields such as geochemical and geophysical anomalies, and they are commonly investigated by using multiscale- and scaling-analysis methods. In this paper, the wavelet-based multiscale decomposition (WMD) method was proposed to investigate the multiscale natures of geochemical pattern from large scale to small scale. In the light of the wavelet transformation of fractal measures, we demonstrated that the wavelet approximation operator provides a generalization of box-counting method for scaling analysis of geochemical patterns. Specifically, the approximation coefficient acts as the generalized density-value in density-area fractal modeling of singular geochemical distributions. Accordingly, we presented a novel local singularity analysis (LSA) using the WMD algorithm which extends the conventional moving averaging to a kernel-based operator for implementing LSA. Finally, the novel LSA was validated using a case study dealing with geochemical data (Fe2O3) in stream sediments for mineral exploration in Inner Mongolia, China. In comparison with the LSA implemented using the moving averaging method the novel LSA using WMD identified improved weak geochemical anomalies associated with mineralization in covered area.

A hybrid model of the CO2 geochemical cycle and its application to large impact events

NASA Technical Reports Server (NTRS)

Kasting, J. F.; Pollack, J. B.; Toon, O. B.; Richardson, S. M.

1986-01-01

The effects of a large asteriod or comet impact on modern and ancient marine biospheres are analyzed. A hybrid model of the carbonate-silicate geochemical cycle, which is capable of calculating the concentrations of carbon dioxide in the atmosphere, ocean, and sedimentary rocks, is described. The differences between the Keir and Berger (1983) model and the hybrid model are discussed. Equilibrium solutions are derived for the preindustrial atmosphere/ocean system and for a system similar to that of the late Cretaceous Period. The model data reveal that globl darkening caused by a stratospheric dust veil could destroy the existing phytoplankton within a period of several weeks or months, nd the dissolution of atmospheric NO(x) compounds would lower the pH of ocean surface waters and release CO2 into the atmosphere. It is noted that the surface temperatures could be increased by several degrees and surface oceans would be uninhabitable for calcaerous organisms for approximately 20 years.

Concerning evaluation of eco-geochemical background in remediation strategy

NASA Astrophysics Data System (ADS)

Korobova, Elena; Romanov, Sergey

2015-04-01

The geochemical concept of biosphere developed by V.I. Vernadsky states the geological role of the living organisms in the course of their active chemical interaction with the inert matter (Vernadsky, 1926, 1960). Basing on this theory it is reasonable to suggest that coevolution of living organisms and their environment led to development of the dynamically stable biogeocenoses precisely adequate to their geochemical environment. Soil cover was treated by V.I. Vernadsky as a balanced bio-inert matter resulting from this interaction. Appearance of human mind and then a civilization led to global expansion of human beings, first able to survive in unfavorable geochemical conditions and then starting chemical transformation of the environment to satisfy the growing demands of mankind in food and energy. The residence in unfavorable environment and local contamination was followed by appearance of endemic diseases of plants, animals and man. Therefore zonal, regional and local chemical composition of the soil cover formed in natural conditions may be used for estimation of the optimum geochemical background, most adequate for the corresponding zonal biogeocenoses and species. Moreover, the natural geochemical background and technogenic fields have unequal spatial structure and this facilitates their identification that may be relatively easy realized in remediation strategy. On the assumption of the foregoing, the adequate methodical approach to remediation of technogenically affected areas should account of the interaction of the existing natural and the newly formed technogenic geochemical fields and include the following steps: 1) the study and mapping of geochemical structure of the natural geochemical background basing on soil maps; 2) the study of contaminants and mapping spatial distribution of technogenic releases; 3) construction of risk maps for the target risk groups with due regard to natural ecological threshold concentration in context of risk degree for

An interactive code (NETPATH) for modeling NET geochemical reactions along a flow PATH, version 2.0

USGS Publications Warehouse

Plummer, Niel; Prestemon, Eric C.; Parkhurst, David L.

1994-01-01

NETPATH is an interactive Fortran 77 computer program used to interpret net geochemical mass-balance reactions between an initial and final water along a hydrologic flow path. Alternatively, NETPATH computes the mixing proportions of two to five initial waters and net geochemical reactions that can account for the observed composition of a final water. The program utilizes previously defined chemical and isotopic data for waters from a hydrochemical system. For a set of mineral and (or) gas phases hypothesized to be the reactive phases in the system, NETPATH calculates the mass transfers in every possible combination of the selected phases that accounts for the observed changes in the selected chemical and (or) isotopic compositions observed along the flow path. The calculations are of use in interpreting geochemical reactions, mixing proportions, evaporation and (or) dilution of waters, and mineral mass transfer in the chemical and isotopic evolution of natural and environmental waters. Rayleigh distillation calculations are applied to each mass-balance model that satisfies the constraints to predict carbon, sulfur, nitrogen, and strontium isotopic compositions at the end point, including radiocarbon dating. DB is an interactive Fortran 77 computer program used to enter analytical data into NETPATH, and calculate the distribution of species in aqueous solution. This report describes the types of problems that can be solved, the methods used to solve problems, and the features available in the program to facilitate these solutions. Examples are presented to demonstrate most of the applications and features of NETPATH. The codes DB and NETPATH can be executed in the UNIX or DOS1 environment. This report replaces U.S. Geological Survey Water-Resources Investigations Report 91-4078, by Plummer and others, which described the original release of NETPATH, version 1.0 (dated December, 1991), and documents revisions and enhancements that are included in version 2.0. 1 The

The geochemical evolution of riparian ground water in a forested piedmont catchment

USGS Publications Warehouse

Burns, Douglas A.; Plummer, Niel; McDonnell, Jeffrey J.; Busenberg, Eurybiades; Casile, Gerolamo C.; Kendall, Carol; Hooper, Richard P.; Freer, James E.; Peters, Norman E.; Beven, Keith; Schlosser, Peter

2003-01-01

The principal weathering reactions and their rates in riparian ground water were determined at the Panola Mountain Research Watershed (PMRW) near Atlanta, Georgia. Concentrations of major solutes were measured in ground water samples from 19 shallow wells completed in the riparian (saprolite) aquifer and in one borehole completed in granite, and the apparent age of each sample was calculated from chloroflourocarbons and tritium/helium-3 data. Concentrations of SiO2, Na+, and Ca2+ generally increased downvalley and were highest in the borehole near the watershed outlet. Strong positive correlations were found between the concentrations of these solutes and the apparent age of ground water that was modern (zero to one year) in the headwaters, six to seven years midway down the valley, and 26 to 27 years in the borehole, located ∼500 m downstream from the headwaters. Mass-balance modeling of chemical evolution showed that the downstream changes in ground water chemistry could be largely explained by weathering of plagioclase to kaolinite, with possible contributions from weathering of K-feldspar, biotite, hornblende, and calcite. The in situ rates of weathering reactions were estimated by combining the ground water age dates with geochemical mass-balance modeling results. The weathering rate was highest for plagioclase (∼6.4 μmol/L/year), but could not be easily compared with most other published results for feldspar weathering at PMRW and elsewhere because the mineral-surface area to which ground water was exposed during geochemical evolution could not be estimated. However, a preliminary estimate of the mineral-surface area that would have contacted the ground water to provide the observed solute concentrations suggests that the plagioclase weathering rate calculated in this study is similar to the rate calculated in a previous study at PMRW, and three to four orders of magnitude slower than those published in previous laboratory studies of feldspar weathering

Inverse modeling of geochemical and mechanical compaction in sedimentary basins

NASA Astrophysics Data System (ADS)

Colombo, Ivo; Porta, Giovanni Michele; Guadagnini, Alberto

2015-04-01

We study key phenomena driving the feedback between sediment compaction processes and fluid flow in stratified sedimentary basins formed through lithification of sand and clay sediments after deposition. Processes we consider are mechanic compaction of the host rock and the geochemical compaction due to quartz cementation in sandstones. Key objectives of our study include (i) the quantification of the influence of the uncertainty of the model input parameters on the model output and (ii) the application of an inverse modeling technique to field scale data. Proper accounting of the feedback between sediment compaction processes and fluid flow in the subsurface is key to quantify a wide set of environmentally and industrially relevant phenomena. These include, e.g., compaction-driven brine and/or saltwater flow at deep locations and its influence on (a) tracer concentrations observed in shallow sediments, (b) build up of fluid overpressure, (c) hydrocarbon generation and migration, (d) subsidence due to groundwater and/or hydrocarbons withdrawal, and (e) formation of ore deposits. Main processes driving the diagenesis of sediments after deposition are mechanical compaction due to overburden and precipitation/dissolution associated with reactive transport. The natural evolution of sedimentary basins is characterized by geological time scales, thus preventing direct and exhaustive measurement of the system dynamical changes. The outputs of compaction models are plagued by uncertainty because of the incomplete knowledge of the models and parameters governing diagenesis. Development of robust methodologies for inverse modeling and parameter estimation under uncertainty is therefore crucial to the quantification of natural compaction phenomena. We employ a numerical methodology based on three building blocks: (i) space-time discretization of the compaction process; (ii) representation of target output variables through a Polynomial Chaos Expansion (PCE); and (iii) model

An array processing system for lunar geochemical and geophysical data

NASA Technical Reports Server (NTRS)

Eliason, E. M.; Soderblom, L. A.

1977-01-01

A computerized array processing system has been developed to reduce, analyze, display, and correlate a large number of orbital and earth-based geochemical, geophysical, and geological measurements of the moon on a global scale. The system supports the activities of a consortium of about 30 lunar scientists involved in data synthesis studies. The system was modeled after standard digital image-processing techniques but differs in that processing is performed with floating point precision rather than integer precision. Because of flexibility in floating-point image processing, a series of techniques that are impossible or cumbersome in conventional integer processing were developed to perform optimum interpolation and smoothing of data. Recently color maps of about 25 lunar geophysical and geochemical variables have been generated.

Hydro-geochemical modeling of subalpine urbanized area: geochemical characterization of the shallow and deep aquifers of the urban district of Como (first results).

NASA Astrophysics Data System (ADS)

Terrana, Silvia; Brunamonte, Fabio; Frascoli, Francesca; Ferrario, Maria Francesca; Michetti, Alessandro Maria; Pozzi, Andrea; Gambillara, Roberto; Binda, Gilberto

2016-04-01

One of the greatest environmental and social-economics threats is climate change. This topic, in the next few years, will have a significant impact on the availability of water resources of many regions. This is compounded by the strong anthropization of water systems that shows an intensification of conflicts for water resource exploitation. Therefore, it is necessary a sustainable manage of natural resources thorough knowledge of the hosting territories. The development of investigation and data processing methods are essential to reduce costs for the suitable use and protection of resources. Identify a sample area for testing the best approach is crucial. This research aims to find a valid methodology for the characterization, modeling and management of subalpine urban aquifers, and the urban district of Como appears perfect. The city of Como is located at the southern end of the western sector of Lake Como (N Italy). It is a coastal town, placed on a small alluvial plain, therefore in close communication with the lake. The plain is drained by two streams, which are presently artificially buried, and have an underground flow path in the urban section till the mouth. This city area, so, is suitable for this project as it is intensely urbanized, its dimensions is not too extensive and it is characterized by two aquifers very important and little known. These are a shallow aquifer and a deep aquifer, which are important not only for any water supply, but also for the stability of the ground subsidence in the city. This research is also the opportunity to work in a particular well-known area with high scientific significance; however, there is complete absence of information regarding the deep aquifer. Great importance has also the chosen and used of the more powerful open source software for this type of area, such as PHREEQC, EnvironInsite, PHREEQE etc., used for geological and geochemical data processing. The main goal of this preliminary work is the

Technical Approach for Determining Key Parameters Needed for Modeling the Performance of Cast Stone for the Integrated Disposal Facility Performance Assessment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yabusaki, Steven B.; Serne, R. Jeffrey; Rockhold, Mark L.

2015-03-30

provides the critical link between the short-term understanding from laboratory and field tests, and the prediction of repository performance over repository time frames and scales. One common recommendation is that experiments be designed to permit the appropriate scaling in the models. There is a large contrast in the physical and chemical properties between the Cast Stone waste package and the IDF backfill and surrounding sediments. Cast Stone exhibits low permeability, high tortuosity, low carbonate, high pH, and low Eh whereas the backfill and native sediments have high permeability, low tortuosity, high carbonate, circumneutral pH, and high Eh. These contrasts have important implications for flow, transport, and reactions across the Cast Stone – backfill interface. Over time with transport across the interface and subsequent reactions, the sharp geochemical contrast will blur and there will be a range of spatially-distributed conditions. In general, COC mobility and transport will be sensitive to these geochemical variations, which also include physical changes in porosity and permeability from mineral reactions. Therefore, PA modeling must address processes, properties, and conditions that alter the physical and chemical controls on COC transport in the cementitious waste forms over time. Section 2 of this document reviews past Hanford PAs and SRS Saltstone PAs, which to date have mostly relied on the lumped parameter COC release conceptual models for TSPA predictions, and provides some details on the chosen values for the lumped parameters. Section 3 provides more details on the hierarchical modeling strategy and processes and mechanisms that control COC release. Section 4 summarizes and lists the key parameters for which numerical values are needed to perform PAs. Section 5 provides brief summaries of the methods used to measure the needed parameters and references to get more details.« less

Geochemical Interactions and Viral-Prokaryote Relationships in Freshwater Environments

NASA Astrophysics Data System (ADS)

Kyle, J. E.; Ferris, G.

2009-05-01

Viral and prokaryotic abundances were surveyed throughout southern Ontario aquatic habitats to determine relationships with geochemical parameters in the natural environment. Surface water samples were collected from acid mine drainage in summer of 2007 and 2008 and from circum-neutral pH environments in October to November 2008. Site determination was based on collecting samples from various aquatic habitats (acid mine drainage, lakes, rivers, tributaries, wetlands) with differing bedrock geology (limestone and shale dominated vs granitic Canadian Shield) to obtain a range of geochemical conditions. At each site, measurements of temperature, pH, and Eh were conducted. Samples collected for microbial counts and electron imaging were preserved to a final concentration of 2.5 % (v/v) glutaraldehyde. Additional sample were filtered into 60 mL nalgene bottles and amber EPA certified 40 mL glass vials to determine chemical constituents and dissolved organic carbon (DOC), respectively. Water was also collected to determine additional physiochemical parameters (dissolved total iron, ferric iron, nitrate, sulfate, phosphate, alkalinity, and turbidity). All samples were stored at 4 °C until analysis. Viral and prokaryotic abundance was determined by staining samples with SYBR Green I and examining with a epifluorescence microscope under blue excitation. Multiple regression analysis using stepwise backwards regression and general linear models revealed that viral abundance was the most influential predictor of prokaryotic abundance. Additional predictors include pH, sulfate, phosphate, and magnesium. The strength of the model was very strong with 90 % of the variability explained (R2 = 0.90, p < 0.007). This is the first report, to our knowledge, of viruses exhibiting such strong controls over prokaryotic abundance in the natural environment. All relationships are positively correlated with the exception of Mg, which is negatively correlated. Iron was also noted as a

The survival of geochemical mantle heterogeneities

NASA Astrophysics Data System (ADS)

Albarede, F.

2004-12-01

The last decade witnessed major changes in our perception of the geochemical dynamics of the mantle. Data bases such as PETDB and GEOROC now provide highly constrained estimates of the geochemical properties of dominant rock types and of their statistics, while the new generation of ICP mass spectrometers triggered a quantum leap in the production of high-precision isotopic and elemental data. Such new advances offer a fresh view of mantle heterogeneities and their survival through convective mixing. A vivid example is provided by the new high-density coverage of the Mid-Atlantic ridge by nearly 500 Pb, Nd, and Hf isotopic data. This new data set demonstrates a rich harmonic structure which illustrates the continuing stretching and refolding of subducted plates by mantle convection. Just as for oceanic chemical variability, the survival of mantle geochemical heterogeneities though mantle circulation can be seen as a competition between stirring and renewal. The modern residence (renewal) times of the incompatible lithophile elements in the mantle calculated using data bases vary within a rather narrow range (4-9 Gy). The mantle is therefore not currently at geochemical steady-state and the effect of its primordial layering on modern mantle geochemistry is still strong. Up to 50 percent of incompatible lithophile elements may never have been extracted into the oceanic crust, which generalizes a conclusion reached previously for 40Ar. A balance between the buoyancy flux and viscous dissipation provides frame-independent estimates of the rates of mixing by mantle convection: primordial geochemical anomalies with initial length scales comparable to mantle depths of plate lengths are only marginally visible at the scale of mantle melting underneath mid-ocean ridges (≈~50~km). They may show up, however, in hot spot basalts and even more in melt inclusions. Up to 50 percent primordial material may be present in the mantle, but scattered throughout as small (<~10~km

Establishing nursery estuary otolith geochemical tags for Sea Bass (Dicentrarchus labrax): Is temporal stability estuary dependent?

NASA Astrophysics Data System (ADS)

Ryan, Diarmuid; Wögerbauer, Ciara; Roche, William

2016-12-01

The ability to determine connectivity between juveniles in nursery estuaries and adult populations is an important tool for fisheries management. Otoliths of juvenile fish contain geochemical tags, which reflect the variation in estuarine elemental chemistry, and allow discrimination of their natal and/or nursery estuaries. These tags can be used to investigate connectivity patterns between juveniles and adults. However, inter-annual variability of geochemical tags may limit the accuracy of nursery origin determinations. Otolith elemental composition was used to assign a single cohort of 0-group sea bass Dicentrarchus labrax to their nursery estuary thus establishing an initial baseline for stocks in waters around Ireland. Using a standard LDFA model, high classification accuracies to nursery sites (80-88%) were obtained. Temporal stability of otolith geochemical tags was also investigated to assess if annual sampling is required for connectivity studies. Geochemical tag stability was found to be strongly estuary dependent.

Geochemical evolution of groundwater in the Mud Lake area, eastern Idaho, USA

USGS Publications Warehouse

Rattray, Gordon W.

2015-01-01

Groundwater with elevated dissolved-solids concentrations—containing large concentrations of chloride, sodium, sulfate, and calcium—is present in the Mud Lake area of Eastern Idaho. The source of these solutes is unknown; however, an understanding of the geochemical sources and processes controlling their presence in groundwater in the Mud Lake area is needed to better understand the geochemical sources and processes controlling the water quality of groundwater at the Idaho National Laboratory. The geochemical sources and processes controlling the water quality of groundwater in the Mud Lake area were determined by investigating the geology, hydrology, land use, and groundwater geochemistry in the Mud Lake area, proposing sources for solutes, and testing the proposed sources through geochemical modeling with PHREEQC. Modeling indicated that sources of water to the eastern Snake River Plain aquifer were groundwater from the Beaverhead Mountains and the Camas Creek drainage basin; surface water from Medicine Lodge and Camas Creeks, Mud Lake, and irrigation water; and upward flow of geothermal water from beneath the aquifer. Mixing of groundwater with surface water or other groundwater occurred throughout the aquifer. Carbonate reactions, silicate weathering, and dissolution of evaporite minerals and fertilizer explain most of the changes in chemistry in the aquifer. Redox reactions, cation exchange, and evaporation were locally important. The source of large concentrations of chloride, sodium, sulfate, and calcium was evaporite deposits in the unsaturated zone associated with Pleistocene Lake Terreton. Large amounts of chloride, sodium, sulfate, and calcium are added to groundwater from irrigation water infiltrating through lake bed sediments containing evaporite deposits and the resultant dissolution of gypsum, halite, sylvite, and bischofite.

Adjustment of geochemical background by robust multivariate statistics

USGS Publications Warehouse

Zhou, D.

1985-01-01

Conventional analyses of exploration geochemical data assume that the background is a constant or slowly changing value, equivalent to a plane or a smoothly curved surface. However, it is better to regard the geochemical background as a rugged surface, varying with changes in geology and environment. This rugged surface can be estimated from observed geological, geochemical and environmental properties by using multivariate statistics. A method of background adjustment was developed and applied to groundwater and stream sediment reconnaissance data collected from the Hot Springs Quadrangle, South Dakota, as part of the National Uranium Resource Evaluation (NURE) program. Source-rock lithology appears to be a dominant factor controlling the chemical composition of groundwater or stream sediments. The most efficacious adjustment procedure is to regress uranium concentration on selected geochemical and environmental variables for each lithologic unit, and then to delineate anomalies by a common threshold set as a multiple of the standard deviation of the combined residuals. Robust versions of regression and RQ-mode principal components analysis techniques were used rather than ordinary techniques to guard against distortion caused by outliers Anomalies delineated by this background adjustment procedure correspond with uranium prospects much better than do anomalies delineated by conventional procedures. The procedure should be applicable to geochemical exploration at different scales for other metals. ?? 1985.

Constraints on Lunar Structure from Combined Geochemical, Mineralogical, and Geophysical modeling

NASA Astrophysics Data System (ADS)

Bremner, P. M.; Fuqua, H.; Mallik, A.; Diamond, M. R.; Lock, S. J.; Panovska, S.; Nishikawa, Y.; Jiménez-Pérez, H.; Shahar, A.; Panero, W. R.; Lognonne, P. H.; Faul, U.

2016-12-01

The internal physical and geochemical structure of the Moon is still poorly constrained. Here, we take a multidisciplinary approach to attempt to constrain key parameters of the lunar structure. We use an ensemble of 1-D lunar compositional models with chemically and mineralogically distinct layers, and forward calculated physical parameters, in order to constrain the internal structure. We consider both a chemically well-mixed model with uniform bulk composition, and a chemically stratified model that includes a mantle with preserved mineralogical stratigraphy from magma ocean crystallization. Additionally, we use four different lunar temperature profiles that span the range of proposed selenotherms, giving eight separate sets of lunar models. In each set, we employed a grid search and a differential evolution genetic search algorithm to extensively explore model space, where the thickness of individual compositional layers was varied. In total, we forward calculated over one hundred thousand lunar models. It has been proposed that a dense, partially molten layer exists at the CMB to explain the lack of observed far-side deep moonquakes, the observation of reflected seismic phases from deep moonquakes, and enhanced tidal dissipation. However, subsequent models have proposed that these observables can be explained in other ways. In this study, using a variety of modeling techniques, we find that such a layer may have been formed by overturn of an ilmenite-rich layer, formed after the crystallization of a magma ocean. We therefore include a denser layer (modeled as an ilmenite-rich layer) at both the top and bottom of the lunar mantle in our models. For each set of models, we find models that explain the observed lunar mass and moment of inertia. We find that only a narrow range of core radii are consistent with the mass and moment of inertia constraints. Furthermore, in the chemically well-mixed models, we find that a dense layer is required in the upper mantle to

Laboratory determination of migration of Eu(III) in compacted bentonite-sand mixtures as buffer/backfill material for high-level waste disposal.

PubMed

Zhou, Lang; Zhang, Huyuan; Yan, Ming; Chen, Hang; Zhang, Ming

2013-12-01

For the safety assessment of geological disposal of high-level radioactive waste (HLW), the migration of Eu(III) through compacted bentonite-sand mixtures was measured under expected repository conditions. Under the evaluated conditions, advection and dispersion is the dominant migration mechanism. The role of sorption on the retardation of migration was also evaluated. The hydraulic conductivities of compacted bentonite-sand mixtures were K=2.07×10(-10)-5.23×10(-10)cm/s, The sorption and diffusion of Eu(III) were examined using a flexible wall permeameter for a solute concentration of 2.0×10(-5)mol/l. The effective diffusion coefficients and apparent diffusion coefficients of Eu(III) in compacted bentonite-sand mixtures were in the range of 1.62×10(-12)-4.87×10(-12)m(2)/s, 1.44×10(-14)-9.41×10(-14)m(2)/s, respectively, which has a very important significance to forecast the relationship between migration length of Eu(III) in buffer/backfill material and time and provide a reference for the design of buffer/backfill material for HLW disposal in China. © 2013 Elsevier Ltd. All rights reserved.

Thermal Properties of Consolidated Granular Salt as a Backfill Material

NASA Astrophysics Data System (ADS)

Paneru, Laxmi P.; Bauer, Stephen J.; Stormont, John C.

2018-03-01

Granular salt has been proposed as backfill material in drifts and shafts of a nuclear waste disposal facility where it will serve to conduct heat away from the waste to the host rock. Creep closure of excavations in rock salt will consolidate (reduce the porosity of) the granular salt. This study involved measuring the thermal conductivity and specific heat of granular salt as a function of porosity and temperature to aid in understanding how thermal properties will change during granular salt consolidation accomplished at pressures and temperatures consistent with a nuclear waste disposal facility. Thermal properties of samples from laboratory-consolidated granular salt and in situ consolidated granular salt were measured using a transient plane source method at temperatures ranging from 50 to 250 °C. Additional measurements were taken on a single crystal of halite and dilated polycrystalline rock salt. Thermal conductivity of granular salt decreased with increases in temperature and porosity. Specific heat of granular salt at lower temperatures decreased with increasing porosity. At higher temperatures, porosity dependence was not apparent. The thermal conductivity and specific heat data were fit to empirical models and compared with results presented in the literature. At comparable densities, the thermal conductivities of granular salt samples consolidated hydrostatically in this study were greater than those measured previously on samples formed by quasi-static pressing. Petrographic studies of the consolidated salt indicate that the consolidation method influenced the nature of the porosity; these observations are used to explain the variation of measured thermal conductivities between the two consolidation methods. Thermal conductivity of dilated polycrystalline salt was lower than consolidated salt at comparable porosities. The pervasive crack network along grain boundaries in dilated salt impedes heat flow and results in a lower thermal conductivity

Geochemical baseline studies of soil in Finland

NASA Astrophysics Data System (ADS)

Pihlaja, Jouni

2017-04-01

The soil element concentrations regionally vary a lot in Finland. Mostly this is caused by the different bedrock types, which are reflected in the soil qualities. Geological Survey of Finland (GTK) is carrying out geochemical baseline studies in Finland. In the previous phase, the research is focusing on urban areas and mine environments. The information can, for example, be used to determine the need for soil remediation, to assess environmental impacts or to measure the natural state of soil in industrial areas or mine districts. The field work is done by taking soil samples, typically at depth between 0-10 cm. Sampling sites are chosen to represent the most vulnerable areas when thinking of human impacts by possible toxic soil element contents: playgrounds, day-care centers, schools, parks and residential areas. In the mine districts the samples are taken from the areas locating outside the airborne dust effected areas. Element contents of the soil samples are then analyzed with ICP-AES and ICP-MS, Hg with CV-AAS. The results of the geochemical baseline studies are published in the Finnish national geochemical baseline database (TAPIR). The geochemical baseline map service is free for all users via internet browser. Through this map service it is possible to calculate regional soil baseline values using geochemical data stored in the map service database. Baseline data for 17 elements in total is provided in the map service and it can be viewed on the GTK's web pages (http://gtkdata.gtk.fi/Tapir/indexEN.html).

Lead Isotopes in Olivine-Phyric Shergottite Tissint: Implications for the Geochemical Evolution of the Shergottite Source Mantle

NASA Technical Reports Server (NTRS)

Moriwaki, R.; Usui, T.; Simon, J. I.; Jones, J. H.; Yokoyama, T.

2015-01-01

Geochemically-depleted shergottites are basaltic rocks derived from a martian mantle source reservoir. Geochemical evolution of the martian mantle has been investigated mainly based on the Rb-Sr, Sm-Nd, and Lu-Hf isotope systematics of the shergottites [1]. Although potentially informative, U-Th- Pb isotope systematics have been limited because of difficulties in interpreting the analyses of depleted meteorite samples that are more susceptible to the effects of near-surface processes and terrestrial contamination. This study conducts a 5-step sequential acid leaching experiment of the first witnessed fall of the geochemically-depleted olivinephyric shergottite Tissint to minimize the effect of low temperature distrubence. Trace element analyses of the Tissint acid residue (mostly pyroxene) indicate that Pb isotope compositions of the residue do not contain either a martian surface or terrestrial component, but represent the Tissint magma source [2]. The residue has relatively unradiogenic initial Pb isotopic compositions (e.g., 206Pb/204Pb = 10.8136) that fall within the Pb isotope space of other geochemically-depleted shergottites. An initial µ-value (238U/204Pb = 1.5) of Tissint at the time of crystallization (472 Ma [3]) is similar to a time-integrated mu- value (1.72 at 472 Ma) of the Tissint source mantle calculated based on the two-stage mantle evolution model [1]. On the other hand, the other geochemically-depleted shergottites (e.g., QUE 94201 [4]) have initial µ-values of their parental magmas distinctly lower than those of their modeled source mantle. These results suggest that only Tissint potentially reflects the geochemical signature of the shergottite mantle source that originated from cumulates of the martian magma ocean

Assessment of hydration process and mechanical properties of cemented paste backfill by electrical resistivity measurement

NASA Astrophysics Data System (ADS)

Xu, Wenbin; Tian, Xichun; Cao, Peiwang

2018-04-01

Cemented paste backfill (CPB) is an emerging mine backfill technique that allows environmentally hazardous tailings to return to the underground openings or stopes, thereby maximising the safety, efficiency and productivity of operation. Uniaxial compressive strength (UCS) is one of the most commonly used parameters for evaluating the mechanical performance of CPB; the prediction of the UCS of CPB structures from early to advanced ages is of great practical importance. This study aims to investigate the predictability of the UCS of CPB during the hydration process based on electrical resistivity (ER) measurement. For this purpose, the samples prepared at different cement-to-tailing ratios and solid contents were subjected to the ER test during the whole hydration process and UCS tests at 3, 7, 28 days of curing periods. The effect of cement-to-tailing ratio and solid content on the ER and UCS of CPB samples was obtained; the UCS values were correlated with the corresponding ER data. Microstructural analysis was also performed on CPB samples to understand the effect of microstructure on the ER data. The result shows that the ER of CPB decreases first and then increases with the speed which is faster in the previous part than the latter. The ER and UCS of CPB samples increased with increasing cement-to-tailing ratio and solid content and curing periods. A logarithmic relationship is established for each mixture in order to predict the UCS of CPB based on ER. Scanning electron microscope analyses have revealed that the microstructure of the CPB changes with the age from the initial floc to honeycomb, and eventually to the compact clumps. The ER properties of CPB samples were highly associated with their respective microstructural properties. The major output of this study is that ER test is effectively capable for a preliminary prediction of the UCS of CPB.

Utilisation of construction and demolition waste as cemented paste backfill material for underground mine openings.

PubMed

Yılmaz, Tekin; Ercikdi, Bayram; Deveci, Hacı

2018-09-15

This study presents the utilisation of finely ground construction and demolition waste (CDW) as partial replacement (5-15 wt.%) to sulphide tailings on the short- and long-term strength, durability (i.e. no loss of strength) and microstructural properties of cemented paste backfill (CPB) over a curing period of 360 days. The CPB samples containing CDW were prepared at binder dosages of 7.5 and 8.5 wt.%, while control samples (full tailings) were only produced at 8.5 wt.% binder dosage. A total of 108 CPB samples were subjected to the unconfined compressive strength (UCS), acid/sulphate (pH, SO 4 2- ) and microstructure (MIP, XRD etc.) tests. Despite its limited contribution to the resistance of CPB to acid and sulphate attack, the use of CDW as partial replacement (5-15 wt.%) to sulphide tailings enhanced the strength properties of CPB samples by decreasing the total and macro porosity. The UCSs and pH values of CPB samples increased with increasing the CDW content in CPB mixtures, while the generation of sulphate ions (SO4 2- ) decreased irrespective of the binder dosages. Compared with control samples prepared at 8.5 wt.% binder dosage, 5.3-19.5% higher UCS values were obtained for the CPB samples containing 15 wt.% CDW prepared even at 7.5 wt.% binder dosage. Mercury intrusion porosimetry (MIP) analyses proved the beneficial effect of the use of CDW on the microstructural properties (i.e. total porosity) of CPB. These findings suggest that CDW materials can be suitably used as backfill material in the mining industry to fill underground voids created during the ore production. This offers safe disposal and hence environmentally sound management of CDW. Copyright © 2018 Elsevier Ltd. All rights reserved.

A geochemical atlas of South Carolina--an example using data from the National Geochemical Survey

USGS Publications Warehouse

Sutphin, David M.

2005-01-01

National Geochemical Survey data from stream-sediment and soil samples, which have been analyzed using consistent methods, were used to create maps, graphs, and tables that were assembled in a consistent atlas format that characterizes the distribution of major and trace chemical elements in South Carolina. Distribution patterns of the elements in South Carolina may assist mineral exploration, agriculture, waste-disposal-siting issues, health, environmental, and other studies. This atlas is an example of how data from the National Geochemical Survey may be used to identify general or regional patterns of elemental occurrences and to provide a snapshot of element concentration in smaller areas.

Geochemical Constraints on the Size of the Moon — Forming Giant Impact

NASA Astrophysics Data System (ADS)

Piet, H.; Badro, J.; Gillet, P.

2018-05-01

We use the partitioning of siderophile trace elements to model the geochemical influence of the Moon-forming giant impact on Earth’s mantle during core formation. We find the size of the impactor to be 15% of Earth mass or smaller.

Uranium plume persistence impacted by hydrologic and geochemical heterogeneity in the groundwater and river water interaction zone of Hanford site

NASA Astrophysics Data System (ADS)

Chen, X.; Zachara, J. M.; Vermeul, V. R.; Freshley, M.; Hammond, G. E.

2015-12-01

The behavior of a persistent uranium plume in an extended groundwater- river water (GW-SW) interaction zone at the DOE Hanford site is dominantly controlled by river stage fluctuations in the adjacent Columbia River. The plume behavior is further complicated by substantial heterogeneity in physical and geochemical properties of the host aquifer sediments. Multi-scale field and laboratory experiments and reactive transport modeling were integrated to understand the complex plume behavior influenced by highly variable hydrologic and geochemical conditions in time and space. In this presentation we (1) describe multiple data sets from field-scale uranium adsorption and desorption experiments performed at our experimental well-field, (2) develop a reactive transport model that incorporates hydrologic and geochemical heterogeneities characterized from multi-scale and multi-type datasets and a surface complexation reaction network based on laboratory studies, and (3) compare the modeling and observation results to provide insights on how to refine the conceptual model and reduce prediction uncertainties. The experimental results revealed significant spatial variability in uranium adsorption/desorption behavior, while modeling demonstrated that ambient hydrologic and geochemical conditions and heterogeneities in sediment physical and chemical properties both contributed to complex plume behavior and its persistence. Our analysis provides important insights into the characterization, understanding, modeling, and remediation of groundwater contaminant plumes influenced by surface water and groundwater interactions.

A geochemical and geophysical reappraisal to the significance of the recent unrest at Campi Flegrei caldera (Southern Italy)

NASA Astrophysics Data System (ADS)

Moretti, Roberto; De Natale, Giuseppe; Troise, Claudia

2017-04-01

Volcanic unrest at calderas involve complex interaction between magma, hydrothermal fluids and crustal stress and strain. Campi Flegrei caldera (CFc), located in the Naples (Italy) area and characterised by the highest volcanic risk on Earth for the extreme urbanisation, undergoes unrest phenomena involving several meters of uplift and intense shallow micro-seismicity since several decades. Despite unrest episodes display in the last decade only moderate ground deformation and seismicity, current interpretations of geochemical data point to a highly pressurized hydrothermal system. We show that at CFc, the usual assumption of vapour-liquid coexistence in the fumarole plumes leads to largely overestimated hydrothermal pressures and, accordingly, interpretations of elevated unrest. By relaxing unconstrained geochemical assumptions, we infer an alternative model yielding better agreement between geophysical and geochemical observations. The model reconciles discrepancies between what observed 1) for two decades since the 1982-84 large unrest, when shallow magma was supplying heat and fluids to the hydrothermal system, and 2) in the last decade. Compared to the 1980's unrest, the post-2005 phenomena are characterized by much lower aquifers overpressure and magmatic involvement, as indicated by geophysical data and despite large changes in geochemical indicators. Our interpretation points out a model in which shallow sills, intruded during 1969-1984, have completely cooled, so that fumarole emissions are affected now by deeper, CO2-richer, magmatic gases producing a relatively modest heating and overpressure of the hydrothermal system. Our results do have important implications on the short-term eruption hazard assessment and on the best strategies for monitoring and interpreting geochemical data.

The oceanic islands - Azores. [geological, geophysical and geochemical features

NASA Technical Reports Server (NTRS)

Ridley, W. I.; Watkins, N. D.; Macfarlane, D. J.

1974-01-01

A presentation is made of the known geological, geophysical, and geochemical data on the Azores. The regional setting of the islands is described; under the geological heading, surface geology and petrochemistry are discussed; and paleomagnetism, marine magnetic surveys, gravity, seismology, and heat flow are treated in the geophysics category. A model for the origin of the Azores is constructed on the basis of these observations.

Mercury's Geochemical Terranes Revisited

NASA Astrophysics Data System (ADS)

Peplowski, P. N.; Stockstill-Cahill, K. R.

2018-05-01

We applied analytical tools to redefine Mercury's major geochemical terranes. The composition and petrology of each terrane will be discussed, along with analyses of gamma-ray data aimed at deriving absolute abundances of Si and Mg in each terrane.

Integrating Hydrogeological, Microbiological, and Geochemical Data Using a Multi-Component Reactive Transport Model: Quantifying the Biogeochemical Evolution of Redox Zones in a Contaminated Aquifer

NASA Astrophysics Data System (ADS)

McGuire, J. T.; Phanikumar, M. S.; Long, D. T.; Hyndman, D. W.

2003-12-01

Hydrogeological, microbiological, and geochemical processes operating in a shallow sandy aquifer contaminated by waste fuels and chlorinated solvents were integrated using high-resolution mechanistic models. A 3-D, transient, reactive transport model was developed to quantitatively describe coupled processes via thermodynamic and kinetic arguments. The model was created by linking the hydrodynamic model MODFLOW (McDonald and Harbaugh, 1988), with advection, dispersion and user defined kinetic reactions based on RT3D 2.0, (Clement and Jones, 1998) and geochemical model PHREEQC (Parkhurst and Appelo, 1999). This model, BGTK3D 2.0, describes 1) the biodegradation of organic matter based on the influence of transport processes on microbial growth, 2) the complex suite of biogeochemical reactions operating in the aquifer, and 3) sharp chemical gradients. Some key features of this model are an ability to incorporate realistic solid phases to test hypotheses regarding mineral-water interactions, and an ability to accurately describe small-scale biogeochemical cycling (cm variability) observed in the field without oscillations or excessive numerical damping. BGTK3D was used to test hypotheses regarding the evolution of redox chemistry in a contaminated aquifer. The conceptual model that terminal electron accepting processes (TEAPs) distribute themselves sequentially into redox zones down flow path in aqueous systems is often used to interpret how and at what rates organic compounds will be degraded in the environment. Geochemical and microbiological data collected from a mixed contaminant plume at the former Wurtsmith AFB in Oscoda, Michigan suggests that under steady-state, mature plume conditions, traditional redox zonation may not be a realistic model of the distribution of TEAPs and therefore may not be the best model to evaluate the potential degradation of organic compounds. Based on these data, a conceptual model of TEAP evolution in contaminated systems was

WATEQ4F - a personal computer Fortran translation of the geochemical model WATEQ2 with revised data base

USGS Publications Warehouse

Ball, J.W.; Nordstrom, D. Kirk; Zachmann, D.W.

1987-01-01

A FORTRAN 77 version of the PL/1 computer program for the geochemical model WATEQ2, which computes major and trace element speciation and mineral saturation for natural waters has been developed. The code (WATEQ4F) has been adapted to execute on an IBM PC or compatible microcomputer. Two versions of the code are available, one operating with IBM Professional FORTRAN and an 8087 or 89287 numeric coprocessor, and one which operates without a numeric coprocessor using Microsoft FORTRAN 77. The calculation procedure is identical to WATEQ2, which has been installed on many mainframes and minicomputers. Limited data base revisions include the addition of the following ions: AlHS04(++), BaS04, CaHS04(++), FeHS04(++), NaF, SrC03, and SrHCO3(+). This report provides the reactions and references for the data base revisions, instructions for program operation, and an explanation of the input and output files. Attachments contain sample output from three water analyses used as test cases and the complete FORTRAN source listing. U.S. Geological Survey geochemical simulation program PHREEQE and mass balance program BALANCE also have been adapted to execute on an IBM PC or compatible microcomputer with a numeric coprocessor and the IBM Professional FORTRAN compiler. (Author 's abstract)

Geochemical modeling of trivalent chromium migration in saline-sodic soil during Lasagna process: impact on soil physicochemical properties.

PubMed

Lukman, Salihu; Bukhari, Alaadin; Al-Malack, Muhammad H; Mu'azu, Nuhu D; Essa, Mohammed H

2014-01-01

Trivalent Cr is one of the heavy metals that are difficult to be removed from soil using electrokinetic study because of its geochemical properties. High buffering capacity soil is expected to reduce the mobility of the trivalent Cr and subsequently reduce the remedial efficiency thereby complicating the remediation process. In this study, geochemical modeling and migration of trivalent Cr in saline-sodic soil (high buffering capacity and alkaline) during integrated electrokinetics-adsorption remediation, called the Lasagna process, were investigated. The remedial efficiency of trivalent Cr in addition to the impacts of the Lasagna process on the physicochemical properties of the soil was studied. Box-Behnken design was used to study the interaction effects of voltage gradient, initial contaminant concentration, and polarity reversal rate on the soil pH, electroosmotic volume, soil electrical conductivity, current, and remedial efficiency of trivalent Cr in saline-sodic soil that was artificially spiked with Cr, Cu, Cd, Pb, Hg, phenol, and kerosene. Overall desirability of 0.715 was attained at the following optimal conditions: voltage gradient 0.36 V/cm; polarity reversal rate 17.63 hr; soil pH 10.0. Under these conditions, the expected trivalent Cr remedial efficiency is 64.75%.

Geochemical Modeling of Trivalent Chromium Migration in Saline-Sodic Soil during Lasagna Process: Impact on Soil Physicochemical Properties

PubMed Central

Bukhari, Alaadin; Al-Malack, Muhammad H.; Mu'azu, Nuhu D.; Essa, Mohammed H.

2014-01-01

Trivalent Cr is one of the heavy metals that are difficult to be removed from soil using electrokinetic study because of its geochemical properties. High buffering capacity soil is expected to reduce the mobility of the trivalent Cr and subsequently reduce the remedial efficiency thereby complicating the remediation process. In this study, geochemical modeling and migration of trivalent Cr in saline-sodic soil (high buffering capacity and alkaline) during integrated electrokinetics-adsorption remediation, called the Lasagna process, were investigated. The remedial efficiency of trivalent Cr in addition to the impacts of the Lasagna process on the physicochemical properties of the soil was studied. Box-Behnken design was used to study the interaction effects of voltage gradient, initial contaminant concentration, and polarity reversal rate on the soil pH, electroosmotic volume, soil electrical conductivity, current, and remedial efficiency of trivalent Cr in saline-sodic soil that was artificially spiked with Cr, Cu, Cd, Pb, Hg, phenol, and kerosene. Overall desirability of 0.715 was attained at the following optimal conditions: voltage gradient 0.36 V/cm; polarity reversal rate 17.63 hr; soil pH 10.0. Under these conditions, the expected trivalent Cr remedial efficiency is 64.75 %. PMID:25152905

Geochemical study of groundwater at Sandia National Laboratories/New Mexico and Kirtland Air Force Base

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

The U.S. Department of Energy (DOE) Grand Junction Projects Office (GJPO) and its contractor, Rust Geotech, support the Kirtland Area Office by assisting Sandia National Laboratories/New Mexico (Sandia/NM) with remedial action, remedial design, and technical support of its Environmental Restoration Program. To aid in determining groundwater origins and flow paths, the GJPO was tasked to provide interpretation of groundwater geochemical data. The purpose of this investigation was to describe and analyze the groundwater geochemistry of the Sandia/NM Kirtland Air Force Base (KAFB). Interpretations of groundwater origins are made by using these data and the results of {open_quotes}mass balance{close_quotes} and {open_quotes}reactionmore » path{close_quote} modeling. Additional maps and plots were compiled to more fully comprehend the geochemical distributions. A more complete set of these data representations are provided in the appendices. Previous interpretations of groundwater-flow paths that were based on well-head, geologic, and geochemical data are presented in various reports and were used as the basis for developing the models presented in this investigation.« less

Carbon sequestration via reaction with basaltic rocks: geochemical modeling and experimental results

USGS Publications Warehouse

Rosenbauer, Robert J.; Thomas, Burt; Bischoff, James L.; Palandri, James

2012-01-01

Basaltic rocks are potential repositories for sequestering carbon dioxide (CO2) because of their capacity for trapping CO2 in carbonate minerals. We carried out a series of thermodynamic equilibrium models and high pressure experiments, reacting basalt with CO2-charged fluids over a range of conditions from 50 to 200 °C at 300 bar. Results indicate basalt has a high reactivity to CO2 acidified brine. Carbon dioxide is taken up from solution at all temperatures from 50 to 200 °C, 300 bar, but the maximum extent and rate of reaction occurs at 100 °C, 300 bar. Reaction path simulations utilizing the geochemical modeling program CHILLER predicted an equilibrium carbonate alteration assemblage of calcite, magnesite, and siderite, but the only secondary carbonate identified in the experiments was a ferroan magnesite. The amount of uptake at 100 °C, 300 bar ranged from 8% by weight for a typical tholeite to 26% for a picrite. The actual amount of CO2 uptake and extent of rock alteration coincides directly with the magnesium content of the rock suggesting that overall reaction extent is controlled by bulk basalt Mg content. In terms of sequestering CO2, an average basaltic MgO content of 8% is equivalent to 2.6 × 108 metric ton CO2/km3 basalt.

Coupling between geochemical reactions and multicomponent gas and solute transport in unsaturated media: A reactive transport modeling study

USGS Publications Warehouse

Molins, S.; Mayer, K.U.

2007-01-01

The two‐way coupling that exists between biogeochemical reactions and vadose zone transport processes, in particular gas phase transport, determines the composition of soil gas. To explore these feedback processes quantitatively, multicomponent gas diffusion and advection are implemented into an existing reactive transport model that includes a full suite of geochemical reactions. Multicomponent gas diffusion is described on the basis of the dusty gas model, which accounts for all relevant gas diffusion mechanisms. The simulation of gas attenuation in partially saturated landfill soil covers, methane production, and oxidation in aquifers contaminated by organic compounds (e.g., an oil spill site) and pyrite oxidation in mine tailings demonstrate that both diffusive and advective gas transport can be affected by geochemical reactions. Methane oxidation in landfill covers reduces the existing upward pressure gradient, thereby decreasing the contribution of advective methane emissions to the atmosphere and enhancing the net flux of atmospheric oxygen into the soil column. At an oil spill site, methane oxidation causes a reversal in the direction of gas advection, which results in advective transport toward the zone of oxidation both from the ground surface and the deeper zone of methane production. Both diffusion and advection contribute to supply atmospheric oxygen into the subsurface, and methane emissions to the atmosphere are averted. During pyrite oxidation in mine tailings, pressure reduction in the reaction zone drives advective gas flow into the sediment column, enhancing the oxidation process. In carbonate‐rich mine tailings, calcite dissolution releases carbon dioxide, which partly offsets the pressure reduction caused by O2 consumption.

Geobiochemistry: Placing Biochemistry in Its Geochemical Context

NASA Astrophysics Data System (ADS)

Shock, E.; Boyer, G. M.; Canovas, P. A., III; Prasad, A.; Dick, J. M.

2014-12-01

Goals of geobiochemistry include simultaneously evaluating the relative stabilities of microbial cells and minerals, and predicting how the composition of biomolecules can change in response to the progress of geochemical reactions. Recent developments in theoretical geochemistry make it possible to predict standard thermodynamic properties of proteins, nucleotides, lipids, and many metabolites including the constituents of the citric acid cycle, at all temperatures and pressures where life is known to occur, and beyond. Combining these predictions with constraints from geochemical data makes it possible to assess the relative stabilities of biomolecules. Resulting independent predictions of the environmental occurrence of homologous proteins and lipid side-chains can be compared with observations from metagenomic and metalipidomic data to quantify geochemical driving forces that shape the composition of biomolecules. In addition, the energetic costs of generating biomolecules from within a diverse range of habitable environments can be evaluated in terms of prevailing geochemical variables. Comparisons of geochemical bioenergetic calculations across habitats leads to the generalization that the availability of H2 determines the cost of autotrophic biosynthesis relative to the aquatic environment external to microbial cells, and that pH, temperature, pressure, and availability of C, N, P, and S are typically secondary. Increasingly reduced conditions, which are determined by reactions of water with mineral surfaces and mineral assemblages, allow many biosynthetic reactions to shift from costing energy to releasing energy. Protein and lipid synthesis, as well as the reverse citric acid cycle, become energy-releasing processes under these conditions. The resulting energy balances that determine habitability contrast dramatically with assumptions derived from oxic surface conditions, such as those where human biochemistry operates.

Development of a Model of Geophysical and Geochemical Controls on Abiotic Carbon Cycling on Earth-Like Planets

NASA Astrophysics Data System (ADS)

Neveu, M.; Felton, R.; Domagal-Goldman, S. D.; Desch, S. J.; Arney, G. N.

2017-12-01

About 20 Earth-sized planets (0.6-1.6 Earth masses and radii) have now been discovered beyond our solar system [1]. Although such planets are prime targets in the upcoming search for atmospheric biosignatures, their composition, geology, and climate are essentially unconstrained. Yet, developing an understanding of how these factors influence planetary evolution through time and space is essential to establishing abiotic backgrounds against which any deviations can provide evidence for biological activity. To this end, we are building coupled geophysical-geochemical models of abiotic carbon cycling on such planets. Our models are controlled by atmospheric factors such as temperature and composition, and compute interior inputs to atmospheric species. They account for crustal weathering, ocean-atmosphere equilibria, and exchange with the deep interior as a function of planet composition and size (and, eventually, age).Planets in other solar systems differ from the Earth not only in their bulk physical properties, but also likely in their bulk chemical composition [2], which influences key parameters such as the vigor of mantle convection and the near-surface redox state. Therefore, simulating how variations in such parameters affect carbon cycling requires us to simulate the above processes from first principles, rather than by using arbitrary parameterizations derived from observations as is often done with models of carbon cycling on Earth [3] or extrapolations thereof [4]. As a first step, we have developed a kinetic model of crustal weathering using the PHREEQC code [5] and kinetic data from [6]. We will present the ability of such a model to replicate Earth's carbon cycle using, for the time being, parameterizations for surface-interior-atmosphere exchange processes such as volcanism (e.g., [7]).[1] exoplanet.eu, 7/28/2017.[2] Young et al. (2014) Astrobiology 14, 603-626.[3] Lerman & Wu (2008) Kinetics of Global Geochemical Cycles. In Kinetics of Water

Multivariate analysis of ATR-FTIR spectra for assessment of oil shale organic geochemical properties

USGS Publications Warehouse

Washburn, Kathryn E.; Birdwell, Justin E.

2013-01-01

In this study, attenuated total reflectance (ATR) Fourier transform infrared spectroscopy (FTIR) was coupled with partial least squares regression (PLSR) analysis to relate spectral data to parameters from total organic carbon (TOC) analysis and programmed pyrolysis to assess the feasibility of developing predictive models to estimate important organic geochemical parameters. The advantage of ATR-FTIR over traditional analytical methods is that source rocks can be analyzed in the laboratory or field in seconds, facilitating more rapid and thorough screening than would be possible using other tools. ATR-FTIR spectra, TOC concentrations and Rock–Eval parameters were measured for a set of oil shales from deposits around the world and several pyrolyzed oil shale samples. PLSR models were developed to predict the measured geochemical parameters from infrared spectra. Application of the resulting models to a set of test spectra excluded from the training set generated accurate predictions of TOC and most Rock–Eval parameters. The critical region of the infrared spectrum for assessing S1, S2, Hydrogen Index and TOC consisted of aliphatic organic moieties (2800–3000 cm−1) and the models generated a better correlation with measured values of TOC and S2 than did integrated aliphatic peak areas. The results suggest that combining ATR-FTIR with PLSR is a reliable approach for estimating useful geochemical parameters of oil shales that is faster and requires less sample preparation than current screening methods.

Kriging - a challenge in geochemical mapping

NASA Astrophysics Data System (ADS)

Stojdl, Jiri; Matys Grygar, Tomas; Elznicova, Jitka; Popelka, Jan; Vachova, Tatina; Hosek, Michal

2017-04-01

Geochemists can easily provide datasets for contamination mapping thanks to recent advances in geographical information systems (GIS) and portable chemical-analytical instrumentation. Kriging is commonly used to visualise the results of such mapping. It is understandable, as kriging is a well-established method of spatial interpolation. It was created in 1950's for geochemical data processing to estimate the most likely distribution of gold based on samples from a few boreholes. However, kriging is based on the assumption of continuous spatial distribution of numeric data that is not realistic in environmental geochemistry. The use of kriging is correct when the data density is sufficient with respect to heterogeneity of the spatial distribution of the geochemical parameters. However, if anomalous geochemical values are focused in hotspots of which boundaries are insufficiently densely sampled, kriging could provide misleading maps with the real contours of hotspots blurred by data smoothing and levelling out individual (isolated) but relevant anomalous values. The data smoothing can thus it results in underestimation of geochemical extremes, which may in fact be of the greatest importance in mapping projects. In our study we characterised hotspots of contamination by uranium and zinc in the floodplain of the Ploučnice River. The first objective of our study was to compare three methods of sampling: random (based on stochastic generation of sampling points), systematic (square grid) and judgemental sampling (based on judgement stemming from principles of fluvial deposition) as the basis for pollution maps. The first detected problem in production of the maps was the reduction of the smoothing effect of kriging using appropriate function of empirical semivariogram and setting the variation of at microscales smaller than the sampling distances to minimum (the "nugget" parameter of semivariogram). Exact interpolators such as Inverse Distance Weighting (IDW) or Radial

Geochemical Interpretation of Collision Volcanism

NASA Astrophysics Data System (ADS)

Pearce, Julian

2014-05-01

Collision volcanism can be defined as volcanism that takes place during an orogeny from the moment that continental subduction starts to the end of orogenic collapse. Its importance in the Geological Record is greatly underestimated as collision volcanics are easily misinterpreted as being of volcanic arc, extensional or mantle plume origin. There are many types of collision volcanic province: continent-island arc collision (e.g. Banda arc); continent-active margin collision (e.g. Tibet, Turkey-Iran); continent-rear-arc collision (e.g. Bolivia); continent-continent collision (e.g. Tuscany); and island arc-island arc collision (e.g. Taiwan). Superimposed on this variability is the fact that every orogeny is different in detail. Nonetheless, there is a general theme of cyclicity on different time scales. This starts with syn-collision volcanism resulting from the subduction of an ocean-continent transition and continental lithosphere, and continues through post-collision volcanism. The latter can be subdivided into orogenic volcanism, which is related to thickened crust, and post-orogenic, which is related to orogenic collapse. Typically, but not always, collision volcanism is preceded by normal arc volcanism and followed by normal intraplate volcanism. Identification and interpretation of collision volcanism in the Geologic Record is greatly facilitated if a dated stratigraphic sequence is present so that the petrogenic evolution can be traced. In any case, the basis of fingerprinting collision terranes is to use geochemical proxies for mantle and subduction fluxes, slab temperatures, and depths and degrees of melting. For example, syn-collision volcanism is characterized by a high subduction flux relative to mantle flux because of the high input flux of fusible sediment and crust coupled with limited mantle flow, and because of high slab temperatures resulting from the decrease in subduction rate. The resulting geochemical patterns are similar regardless of

Geochemical modeling of fluid-fluid and fluid-mineral interactions during geological CO2 storage

NASA Astrophysics Data System (ADS)

Zhu, C.; Ji, X.; Lu, P.

2013-12-01

The long time required for effective CO2 storage makes geochemical modeling an indispensable tool for CCUS. One area of geochemical modeling research that is in urgent need is impurities in CO2 streams. Permitting impurities, such as H2S, in CO2 streams can lead to potential capital and energy savings. However, predicting the consequences of co-injection of CO2 and impurities into geological formations requires the understanding of the phase equilibrium and fluid-fluid interactions. To meet this need, we developed a statistical associating fluid theory (SAFT)-based equation of state (EOS) for the H2S-CO2-H2O-NaCl system at 373.15 modeling of fluid-mineral interactions must confront unresolved uncertainties of silicate dissolution - precipitation reaction kinetics. Most prominent among these uncertainties is the well-known lab-field apparent discrepancy in dissolution rates. Although reactive transport models that simulate the interactions between reservoir rocks and brine, and their attendant effects on porosity and permeability changes, have proliferated, whether these results have acceptable uncertainties are unknown. We have conducted a series of batch experiments at elevated temperatures and numerical simulations of coupled dissolution and precipitation reactions. The results show that taking into account

A graphical method to evaluate predominant geochemical processes occurring in groundwater systems for radiocarbon dating

USGS Publications Warehouse

Han, Liang-Feng; Plummer, Niel; Aggarwal, Pradeep

2012-01-01

A graphical method is described for identifying geochemical reactions needed in the interpretation of radiocarbon age in groundwater systems. Graphs are constructed by plotting the measured 14C, δ13C, and concentration of dissolved inorganic carbon and are interpreted according to specific criteria to recognize water samples that are consistent with a wide range of processes, including geochemical reactions, carbon isotopic exchange, 14C decay, and mixing of waters. The graphs are used to provide a qualitative estimate of radiocarbon age, to deduce the hydrochemical complexity of a groundwater system, and to compare samples from different groundwater systems. Graphs of chemical and isotopic data from a series of previously-published groundwater studies are used to demonstrate the utility of the approach. Ultimately, the information derived from the graphs is used to improve geochemical models for adjustment of radiocarbon ages in groundwater systems.

Hydrologic and geochemical approaches for determining ground-water flow components

USGS Publications Warehouse

Hjalmarson, H.W.; Robertson, F.N.

1991-01-01

Lyman Lake is an irrigation-storage reservoir on the Little Colorado River near St. Johns, Arizona. The main sources of water for the lake are streamflow in the Little Colorado River and ground-water inflow from the underlying Coconino aquifer. Two approaches, a hydrologic analysis and a geochemical analysis, were used to compute the quantity of ground-water flow to and from Lyman Lake. Hydrologic data used to calculate a water budget were precipitation on the lake, evaporation from the lake, transpiration from dense vegetation, seepage through the dam, streamflow in and out of the lake, and changes in lake storage. Geochemical data used to calculate the ground-water flow components were major ions, trace elements, and the stable isotopes of hydrogen and oxygen. During the study, the potentiometric level of the Coconino aquifer was above the lake level at the upstream end of the lake and below the lake level at the downstream end. Hydrologic and geochemical data indicate that about 10 percent and 8 percent, respectively, of the water in the lake is ground-water inflow and that about 35 percent of the water in the Little Colorado River 6 miles downgradient from the lake near Salado Springs is ground water. These independent estimates of ground-water flow derived from each approach are in agreement and support a conceptual model of the water budget.

Mineral and Geochemical Classification From Spectroscopy/Diffraction Through Neural Networks

NASA Astrophysics Data System (ADS)

Ferralis, N.; Grossman, J.; Summons, R. E.

2017-12-01

Spectroscopy and diffraction techniques are essential for understanding structural, chemical and functional properties of geological materials for Earth and Planetary Sciences. Beyond data collection, quantitative insight relies on experimentally assembled, or computationally derived spectra. Inference on the geochemical or geophysical properties (such as crystallographic order, chemical functionality, elemental composition, etc.) of a particular geological material (mineral, organic matter, etc.) is based on fitting unknown spectra and comparing the fit with consolidated databases. The complexity of fitting highly convoluted spectra, often limits the ability to infer geochemical characteristics, and limits the throughput for extensive datasets. With the emergence of heuristic approaches to pattern recognitions though machine learning, in this work we investigate the possibility and potential of using supervised neural networks trained on available public spectroscopic database to directly infer geochemical parameters from unknown spectra. Using Raman, infrared spectroscopy and powder x-ray diffraction from the publicly available RRUFF database, we train neural network models to classify mineral and organic compounds (pure or mixtures) based on crystallographic structure from diffraction, chemical functionality, elemental composition and bonding from spectroscopy. As expected, the accuracy of the inference is strongly dependent on the quality and extent of the training data. We will identify a series of requirements and guidelines for the training dataset needed to achieve consistent high accuracy inference, along with methods to compensate for limited of data.

Geochemical Exploration Techniques Applicable in the Search for Copper Deposits

USGS Publications Warehouse

Chaffee, Maurice A.

1975-01-01

Geochemical exploration is an important part of copper-resource evaluation. A large number of geochemical exploration techniques, both proved and untried, are available to the geochemist to use in the search for new copper deposits. Analyses of whole-rock samples have been used in both regional and local geochemical exploration surveys in the search for copper. Analyses of mineral separates, such as biotite, magnetite, and sulfides, have also been used. Analyses of soil samples are widely used in geochemical exploration, especially for localized surveys. It is important to distinguish between residual and transported soil types. Orientation studies should always be conducted prior to a geochemical investigation in a given area in order to determine the best soil horizon and the best size of soil material for sampling in that area. Silty frost boils, caliche, and desert varnish are specialized types of soil samples that might be useful sampling media. Soil gas is a new and potentially valuable geochemical sampling medium, especially in exploring for buried mineral deposits in arid regions. Gaseous products in samples of soil may be related to base-metal deposits and include mercury vapor, sulfur dioxide, hydrogen sulfide, carbon oxysulfide, carbon dioxide, hydrogen, oxygen, nitrogen, the noble gases, the halogens, and many hydrocarbon compounds. Transported materials that have been used in geochemical sampling programs include glacial float boulders, glacial till, esker gravels, stream sediments, stream-sediment concentrates, and lake sediments. Stream-sediment sampling is probably the most widely used and most successful geochemical exploration technique. Hydrogeochemical exploration programs have utilized hot- and cold-spring waters and their precipitates as well as waters from lakes, streams, and wells. Organic gel found in lakes and at stream mouths is an unproved sampling medium. Suspended material and dissolved gases in any type of water may also be useful

Subsurface Reactive Transport Modelling of the Lateritic Ni mineralization in New Caledonia: A coupled Thermo-Hydro-Geochemical Approach

NASA Astrophysics Data System (ADS)

Myagkiy, Andrey; Golfier, Fabrice; Truche, Laurent; Cathelineau, Michel

2017-04-01

This research proposes a subsurface reactive geochemical transport modelling of the development of a nickel laterite profile in New Caledonia over the past few million years. Such a regolith formation from ultramafic bedrock was not yet modelled and gives new profound insights into the Ni vertical mobility, its retention processes in a soil profile and relative enrichment, that are still poorly studied. The downward progression of the lateritization front is allowed by the leaching of the soluble elements (Si, Mg and Ni) through drainage system, represented by porous column of peridotite. Particular emphasis is placed on the detailed understanding of Ni redistribution as a function of time and depth triggered by Ni-bearing silicate precipitation (i.e. garnierite) and by sorption or recrystallization process with goethite. Current work consists of the following models: i) 1-D calculations that are done at 25oC with the code PHREEQC associated with the llnl thermodynamic database and ii) 2-D model that handles coupled thermo-hydro-chemical processes and is calculated on the interface Comsol-Phreeqc (iCP, Nardi et al., 2014). The impact of i) fluid flow in fractures and ii) recharge rate along with iii) hydraulic and iv) geothermal gradients are considered here. While the first model gives profound insights into the vertical mobility of metals upon the formation of laterite (Myagkiy et al, submitted), the latter one additionally allows to describe heterogeneities of mineralizing distributions due to the influence of preferential pathways (fractures), convective flows and lateral transfers. Our long-term 1-D simulations (10 Ma) clearly demonstrate that the Ni enrichment and thickening of iron-rich zone are governed by the vertical progression of the pH front. At the same time 2-D modelling shows reactivation of Ni from oxide zone and it subsequent redistribution and concentration in saprolite. Such a model appears to be of importance in attempt of explanation Ni

A Watched Ocean World Never Boils: Inspecting the Geochemical Impact on Ocean Worlds from Their Thermal Evolution

NASA Astrophysics Data System (ADS)

Spiers, E. M.; Schmidt, B. E.

2018-05-01

I aim to acquire better understanding of coupled thermal evolution and geochemical fluxes of an ocean world through a box model. A box model divides the system into plainer elements with realistically-solvable, dynamic equations.

The stabilization of the rock mass of the wieliczka salt mine through the backfilling of the witos chamber with the use of injection methods / Stabilizacji górotworu kopalni soli "wieliczka" poprzez likwidację komór "witos" z zastosowaniem metod iniekcji

NASA Astrophysics Data System (ADS)

D'Obyrn, Kajetan

2012-10-01

The Wieliczka Salt Mine is the most famous and the most visited mining industry monument in the world and it requires modern methods to ensure rock mass stability and tourists' security. Both for conservation and tourism organization reasons, the group of Warszawa-Wisla-Budryk-Lebzeltern-Upper Witos Chambers (Photo. 1, 2. 3) located the Kazanów mid-level at a depth of 117 m underground is extremely important. Discontinuous deformation occurring in this Chamber complex was eliminated by comprehensive securing work with anchor housing, but their final securing and stability is conditioned by further backfilling and sealing the Witos Chambers situated directly beneath. In the 1940s and 1950s, the Witos Chamber was backfilled with slag from the mine boilerhouse. However, slags with 80% compressibility are not backfilling material which would ensure the stability of the rock mass. The chambers were exploited in the early nineteenth century in the Spizit salts of the central part of the layered deposit. The condition of the Upper Witos, Wisla, Warszawa, Budryk, and Lebzeltern Chambers is generally good. The western part if the Lebzeltern Chamber (Fig. 1), which was threatened with collapse, was backfilled with sand. In all the chambers of the Witos complex, local deformation of ceiling rock of varying intensity is observed as well as significant destruction of the side walls of pillars between chambers. No hydrogeological phenomena are observed in the chambers. It has been attempted to solve the problem of stability of the rock mass in this region of the mine by extracting the slag and backfilling with sand, erecting concrete supporting pillars, backfilling the voids with sand, anchoring the ceiling and the side walls, the use of the pillar housing. The methods have either not been applied or have been proved insufficient to properly protect the excavation situated above. In order to select the optimal securing method, a geomechanical analysis was conducted in order to

TrigDB back-filling method in EEW for the regional earthquake for reducing false location of the deep focus earthquake event by considering neighborhood triggers and forced association.

NASA Astrophysics Data System (ADS)

Park, J. H.; Chi, H. C.; Lim, I. S.; Seong, Y. J.; Pak, J.

2017-12-01

During the first phase of EEW(Earthquake Early Warning) service to the public by KMA (Korea Meteorological Administration) from 2015 in Korea, KIGAM(Korea Institute of Geoscience and Mineral Resources) has adopted ElarmS2 of UC Berkeley BSL and modified local magnitude relation, travel time curves and association procedures so called TrigDB back-filling method. The TrigDB back-filling method uses a database of sorted lists of stations based on epicentral distances of the pre-defined events located on the grids for 1,401 × 1,601 = 2,243,001 events around the Korean Peninsula at a grid spacing of 0.05 degrees. When the version of an event is updated, the TrigDB back-filling method is invoked. First, the grid closest to the epicenter of an event is chosen from the database and candidate stations, which are stations corresponding to the chosen grid and also adjacent to the already-associated stations, are selected. Second, the directions from the chosen grid to the associated stations are averaged to represent the direction of wave propagation, which is used as a reference for computing apparent travel times. The apparent travel times for the associated stations are computed using a P wave velocity of 5.5 km/s from the grid to the projected points in the reference direction. The travel times for the triggered candidate stations are also computed and used to obtain the difference between the apparent travel times of the associated stations and the triggered candidates. Finally, if the difference in the apparent travel times is less than that of the arrival times, the method forces the triggered candidate station to be associated with the event and updates the event location. This method is useful to reduce false locations of events which could be generated from the deep (> 500 km) and regional distance earthquakes happening on the subduction pacific plate boundaries. In comparison of the case study between TrigDB back-filling applied system and the others, we could get

Numerical simulation of in-situ chemical oxidation (ISCO) and biodegradation of petroleum hydrocarbons using a coupled model for bio-geochemical reactive transport

NASA Astrophysics Data System (ADS)

Marin, I. S.; Molson, J. W.

2013-05-01

Petroleum hydrocarbons (PHCs) are a major source of groundwater contamination, being a worldwide and well-known problem. Formed by a complex mixture of hundreds of organic compounds (including BTEX - benzene, toluene, ethylbenzene and xylenes), many of which are toxic and persistent in the subsurface and are capable of creating a serious risk to human health. Several remediation technologies can be used to clean-up PHC contamination. In-situ chemical oxidation (ISCO) and intrinsic bioremediation (IBR) are two promising techniques that can be applied in this case. However, the interaction of these processes with the background aquifer geochemistry and the design of an efficient treatment presents a challenge. Here we show the development and application of BIONAPL/Phreeqc, a modeling tool capable of simulating groundwater flow, contaminant transport with coupled biological and geochemical processes in porous or fractured porous media. BIONAPL/Phreeqc is based on the well-tested BIONAPL/3D model, using a powerful finite element simulation engine, capable of simulating non-aqueous phase liquid (NAPL) dissolution, density-dependent advective-dispersive transport, and solving the geochemical and kinetic processes with the library Phreeqc. To validate the model, we compared BIONAPL/Phreeqc with results from the literature for different biodegradation processes and different geometries, with good agreement. We then used the model to simulate the behavior of sodium persulfate (NaS2O8) as an oxidant for BTEX degradation, coupled with sequential biodegradation in a 2D case and to evaluate the effect of inorganic geochemistry reactions. The results show the advantages of a treatment train remediation scheme based on ISCO and IBR. The numerical performance and stability of the integrated BIONAPL/Phreeqc model was also verified.

Assessment of groundwater quality: a fusion of geochemical and geophysical information via Bayesian neural networks.

PubMed

Maiti, Saumen; Erram, V C; Gupta, Gautam; Tiwari, Ram Krishna; Kulkarni, U D; Sangpal, R R

2013-04-01

Deplorable quality of groundwater arising from saltwater intrusion, natural leaching and anthropogenic activities is one of the major concerns for the society. Assessment of groundwater quality is, therefore, a primary objective of scientific research. Here, we propose an artificial neural network-based method set in a Bayesian neural network (BNN) framework and employ it to assess groundwater quality. The approach is based on analyzing 36 water samples and inverting up to 85 Schlumberger vertical electrical sounding data. We constructed a priori model by suitably parameterizing geochemical and geophysical data collected from the western part of India. The posterior model (post-inversion) was estimated using the BNN learning procedure and global hybrid Monte Carlo/Markov Chain Monte Carlo optimization scheme. By suitable parameterization of geochemical and geophysical parameters, we simulated 1,500 training samples, out of which 50 % samples were used for training and remaining 50 % were used for validation and testing. We show that the trained model is able to classify validation and test samples with 85 % and 80 % accuracy respectively. Based on cross-correlation analysis and Gibb's diagram of geochemical attributes, the groundwater qualities of the study area were classified into following three categories: "Very good", "Good", and "Unsuitable". The BNN model-based results suggest that groundwater quality falls mostly in the range of "Good" to "Very good" except for some places near the Arabian Sea. The new modeling results powered by uncertainty and statistical analyses would provide useful constrain, which could be utilized in monitoring and assessment of the groundwater quality.

Evaluation of geochemical and hydrogeological processes by geochemical modeling in an area affected by evaporite karstification

NASA Astrophysics Data System (ADS)

Acero, P.; Auqué, L. F.; Galve, J. P.; Gutiérrez, F.; Carbonel, D.; Gimeno, M. J.; Yechieli, Y.; Asta, M. P.; Gómez, J. B.

2015-10-01

The Ebro Valley in the outskirts of Zaragoza (NE Spain) is severely affected by evaporite karstification, leading to multiple problems related to subsidence and sinkhole formation. In this work, a combination of inverse (mixing + mass-balance) and forward (reaction-path) geochemical calculations is applied for the quantification of the main karstification processes and seasonal variations in this area. The obtained results prove the suitability of the applied methodology for the characterization of similar problems in other areas with scarce geological and hydrogeological information. The hydrogeology and hydrochemistry of the system can be mainly attributed to the mixing of variable proportions of concentrated groundwater from the evaporitic aquifer and more dilute water from the overlying alluvial aquifer. The existence of a good connection between these aquifers is supported by: (1) the fast changes in the hydrochemistry of the karst aquifer related to recharge by irrigation, and (2) the deduced input of evaporitic groundwater in the alluvial materials. The evolution in some parts of the alluvial/evaporitic aquifer system is clearly dominated by the seasonal variations in the recharge by dilute irrigation waters (up to 95% of water volume in some sinkhole ponds), whereas other points seem to be clearly determined by the hydrochemistry of the concentrated evaporitic aquifer groundwater (up to 50% of the water volume in some springs). The following reactions, previous or superimposed to mixing processes, explain the observed hydrochemistry in the studied area: dissolution of halite (NaCl), gypsum (CaSO4ṡ2H2O)/anhydrite (CaSO4) and dolomite (CaMg(CO3)2), CO2(g) input and degassing and calcite (CaCO3) dissolution/precipitation. The modeling results suggest the existence of a large spatial variability in the composition of the evaporitic groundwater, mainly caused by large differences in the availability of halite in contact with the groundwater. Active subsidence

Biokinetics of yttrium and comparison with its geochemical twin holmium

DOE PAGES

Leggett, Rich

2017-06-01

The transition metal yttrium (Y, atomic number 39) is chemically similar to elements in the lanthanide family (atomic numbers 57-71, lanthanum through lutetium) and is always present with the lanthanides in rare earth ores. Yttrium and the lanthanide holmium are particularly close chemical and physical analogues and are referred to as geochemical twins because they typically show little fractionation in geological material. Extensive measurements on rocks, soils, and meteorites indicate that the Y/Ho mass concentration ratio rarely falls far from the “chondritic” or “solar system” ratio of ~26. Our paper presents a new biokinetic model for yttrium in adult humansmore » and examines whether yttrium and holmium may be biological as well as geochemical twins. Collected data on yttrium and holmium in plants and human tissues do not allow precise derivations of Y/Ho concentration ratios but with occasional exceptions yield ratios that are reasonably consistent with chondritic values. Predictions of the time-dependent behavior of yttrium in adult humans based on the yttrium model presented here closely approximate predictions of the behavior of holmium based on a previously developed model for holmium. We know that yttrium and holmium are close biological analogues, but the available comparative data are too limited and imprecise to reveal whether there are any significant differences in their biological behavior.« less

Mineral Precipitation in Fractures: Multiscale Imaging and Geochemical Modeling

NASA Astrophysics Data System (ADS)

Hajirezaie, S.; Peters, C. A.; Swift, A.; Sheets, J. M.; Cole, D. R.; Crandall, D.; Cheshire, M.; Stack, A. G.; Anovitz, L. M.

2017-12-01

For subsurface energy technologies such as geologic carbon sequestration, fractures are potential pathways for fluid migration from target formations. Highly permeable fractures may become sealed by mineral precipitation. In this study, we examined shale specimens with existing cemented fractures as natural analogues, using an array of imaging methods to characterize mineralogy and porosity at several spatial scales. In addition, we used reactive transport modeling to investigate geochemical conditions that can lead to extensive mineral precipitation and to simulate the impacts on fracture hydraulic properties. The naturally-cemented fractured rock specimens were from the Upper Wolfcamp formation in Texas, at 10,000 ft depth. The specimens were scanned using x-ray computed tomography (xCT) at resolution of 13 microns. The xCT images revealed an original fracture aperture of 1.9 mm filled with several distinct mineral phases and vuggy void regions, and the mineral phase volumes and surface areas were quantified and mapped in 3D. Specimens were thin-sectioned and examined at micron- and submicron-scales using petrographic microscopy (PM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and small angle X-ray scattering (SAXS). Collectively these methods revealed crystals of dolomite as large as 900 microns in length overlain with a heterogeneous mixture of carbonate minerals including calcite, dolomite, and Fe-rich dolomite, interspersed at spatial scales as small as 5 microns. In addition, secondary precipitation of SiO2 was found to fill some of the void space. This multiscale imaging was used to inform the reactive transport modeling employed to examine the conditions that can cause the observed mineral precipitation in fractures at a larger scale. Two brines containing solutions that when mixed would lead to precipitation of various carbonate minerals were simulated as injectants into a fracture domain. In particular, the competing

Geochemical and mineralogical methods of prospecting for mineral deposits

USGS Publications Warehouse

Fersman, A. Ye; Borovik, S. A.; Gorshkov, G.V.; Popov, S.D.; Sosedko, A.F.; Hartsock, Lydia; Pierce, A.P.

1952-01-01

Fersman's book "Geochemical and mineralogical methods of prospecting for mineral deposits" (Geokhimicheskiye i mineralogicheskiye metody poiskov poleznykh iskopayemykh) covers all petrographic, mineralogical, and geochemical techniques that are used either directly or indirectly in mineral exploration. Chapter IV is of particular interest because it describes certain geochemical methods and principles that have not been widely applied outside of the Soviet Union. The original contained a number of photographs that have been omitted; the titles of the photographs are given in the body of the text. Wherever possible, bibliographic references have been checked, and the full titles given. References given in footnotes in the original have been collected and added at the end of each section as a bibliography.

Inverse geochemical modeling of groundwater evolution with emphasis on arsenic in the Mississippi River Valley alluvial aquifer, Arkansas (USA)

USGS Publications Warehouse

Sharif, M.U.; Davis, R.K.; Steele, K.F.; Kim, B.; Kresse, T.M.; Fazio, J.A.

2008-01-01

Inverse geochemical modeling (PHREEQC) was used to identify the evolution of groundwater with emphasis on arsenic (As) release under reducing conditions in the shallow (25-30 m) Mississippi River Valley Alluvial aquifer, Arkansas, USA. The modeling was based on flow paths defined by high-precision (??2 cm) water level contour map; X-ray diffraction (XRD), scanning electron microscopic (SEM), and chemical analysis of boring-sediments for minerals; and detailed chemical analysis of groundwater along the flow paths. Potential phases were constrained using general trends in chemical analyses data of groundwater and sediments, and saturation indices data (MINTEQA2) of minerals in groundwater. Modeling results show that calcite, halite, fluorite, Fe oxyhydroxide, organic matter, H2S (gas) were dissolving with mole transfers of 1.40E - 03, 2.13E - 04, 4.15E - 06, 1.25E + 01, 3.11, and 9.34, respectively along the dominant flow line. Along the same flow line, FeS, siderite, and vivianite were precipitating with mole transfers of 9.34, 3.11, and 2.64E - 07, respectively. Cation exchange reactions of Ca2+ (4.93E - 04 mol) for Na+ (2.51E - 04 mol) on exchange sites occurred along the dominant flow line. Gypsum dissolution reactions were dominant over calcite dissolution in some of the flow lines due to the common ion effect. The concentration of As in groundwater ranged from <0.5 to 77 ??g/L. Twenty percent total As was complexed with Fe and Mn oxyhydroxides. The redox environment, chemical data of sediments and groundwater, and the results of inverse geochemical modeling indicate that reductive dissolution of Fe oxyhydroxide is the dominant process of As release in the groundwater. The relative rate of reduction of Fe oxyhydroxide over SO42 - with co-precipitation of As into sulfide is the limiting factor controlling dissolved As in groundwater. ?? 2007 Elsevier B.V. All rights reserved.

Geochemical heterogeneity in a small, stratigraphically complex moraine aquifer system (Ontario, Canada): Interpretation of flow and recharge using multiple geochemical parameters

USGS Publications Warehouse

Stotler, R.L.; Frape, S.K.; El Mugammar, H.T.; Johnston, C.; Judd-Henrey, I.; Harvey, F.E.; Drimmie, R.; Jones, J.P.

2011-01-01

The Waterloo Moraine is a stratigraphically complex system and is the major water supply to the cities of Kitchener and Waterloo in Ontario, Canada. Despite over 30 years of investigation, no attempt has been made to unify existing geochemical data into a single database. A composite view of the moraine geochemistry has been created using the available geochemical information, and a framework created for geochemical data synthesis of other similar flow systems. Regionally, fluid chemistry is highly heterogeneous, with large variations in both water type and total dissolved solids content. Locally, upper aquifer units are affected by nitrate and chloride from fertilizer and road salt. Typical upper-aquifer fluid chemistry is dominated by calcium, magnesium, and bicarbonate, a result of calcite and dolomite dissolution. Evidence also suggests that ion exchange and diffusion from tills and bedrock units accounts for some elevated sodium concentrations. Locally, hydraulic "windows" cross connect upper and lower aquifer units, which are typically separated by a clay till. Lower aquifer units are also affected by dedolomitization, mixing with bedrock water, and locally, upward diffusion of solutes from the bedrock aquifers. A map of areas where aquifer units are geochemically similar was constructed to highlight areas with potential hydraulic windows. ?? 2010 Springer-Verlag.

ASSESSING THE GEOCHEMICAL FATE OF DEEP-WELL-INJECTED HAZARDOUS WASTE: A REFERENCE GUIDE

EPA Science Inventory

The geochemical fate of deep-well-injected wastes must be thoroughly understood to avoid problems when incompatibility between the injected wastes and the injection-zone formation is a possibility. An understanding of geochemical fate will be useful when a geochemical no-migratio...

Principles of landscape-geochemical studies in the zones contaminated by technogenical radionuclides for ecological and geochemical mapping

NASA Astrophysics Data System (ADS)

Korobova, Elena; Romanov, Sergey

2013-04-01

Efficiency of landscape-geochemical approach was proved to be helpful in spatial and temporal evaluation of the Chernobyl radionuclide distribution in the environment. The peculiarity of such approach is in hierarchical consideration of factors responsible for radionuclide redistribution and behavior in a system of inter-incorporated landscape-geochemical structures of the local and regional scales with due regard to the density of the initial fallout and patterns of radionuclide migration in soil-water-plant systems. The approach has been applied in the studies of distribution of Cs-137, Sr-90 and some other radionuclides in soils and vegetation cover and in evaluation of contribution of the stable iodine supply in soils to spatial variation of risk of thyroid cancer in areas subjected to radioiodine contamination after the Chernobyl accident. The main feature of the proposed approach is simultaneous consideration of two types of spatial heterogeneities: firstly, the inhomogeneity of external radiation exposure due to a complex structure of the contamination field, and, secondly, the landscape geochemical heterogeneity of the affected area, so that the resultant effect of radionuclide impact could significantly vary in space. The main idea of risk assessment in this respect was to reproduce as accurately as possible the result of interference of two surfaces in the form of risk map. The approach, although it demands to overcome a number of methodological difficulties, allows to solve the problems associated with spatially adequate protection of the affected population and optimization of the use of contaminated areas. In general it can serve the basis for development of the idea of the two-level structure of modern radiobiogeochemical provinces formed by superposition of the natural geochemical structures and the fields of technogenic contamination accompanied by the corresponding peculiar and integral biological reactions.

Linking the climatic and geochemical controls on global soil carbon cycling

NASA Astrophysics Data System (ADS)

Doetterl, Sebastian; Stevens, Antoine; Six, Johan; Merckx, Roel; Van Oost, Kristof; Casanova Pinto, Manuel; Casanova-Katny, Angélica; Muñoz, Cristina; Boudin, Mathieu; Zagal Venegas, Erick; Boeckx, Pascal

2015-04-01

Climatic and geochemical parameters are regarded as the primary controls for soil organic carbon (SOC) storage and turnover. However, due to the difference in scale between climate and geochemical-related soil research, the interaction of these key factors for SOC dynamics have rarely been assessed. Across a large geochemical and climatic transect in similar biomes in Chile and the Antarctic Peninsula we show how abiotic geochemical soil features describing soil mineralogy and weathering pose a direct control on SOC stocks, concentration and turnover and are central to explaining soil C dynamics at larger scales. Precipitation and temperature had an only indirect control by regulating geochemistry. Soils with high SOC content have low specific potential CO2 respiration rates, but a large fraction of SOC that is stabilized via organo-mineral interactions. The opposite was observed for soils with low SOC content. The observed differences for topsoil SOC stocks along this transect of similar biomes but differing geo-climatic site conditions are of the same magnitude as differences observed for topsoil SOC stocks across all major global biomes. Using precipitation and a set of abiotic geochemical parameters describing soil mineralogy and weathering status led to predictions of high accuracy (R2 0.53-0.94) for different C response variables. Partial correlation analyses revealed that the strength of the correlation between climatic predictors and SOC response variables decreased by 51 - 83% when controlling for geochemical predictors. In contrast, controlling for climatic variables did not result in a strong decrease in the strength of the correlations of between most geochemical variables and SOC response variables. In summary, geochemical parameters describing soil mineralogy and weathering were found to be essential for accurate predictions of SOC stocks and potential CO2 respiration, while climatic factors were of minor importance as a direct control, but are

Geochemical response to hydrologic change along land-sea interfaces

NASA Astrophysics Data System (ADS)

Michael, H. A.; Yu, X.; LeMonte, J. J.; Sparks, D. L.; Kim, K. H.; Heiss, J.; Ullman, W. J.; Guimond, J. A.; Seyfferth, A.

2016-12-01

Coastal groundwater-surface water interfaces are hotspots of geochemical activity, where reactants contributed by different sources come in contact. Reactions that occur along these land-sea boundaries have important effects on fluxes and cycling of carbon, nutrients, and contaminants. Hydrologic perturbations can alter interactions by promoting mixing, changing redox state, and altering subsurface residence times during which reactions may occur. We present examples from field and modeling investigations along the Delaware coastline that illustrate the impacts of hydrologic fluctuations on geochemical conditions and fluxes in different coastal environments. Along the highly populated Wilmington coastline, soils are contaminated with heavy metals from legacy industrial practices. We show with continuous redox monitoring and sampling over tidal to seasonal timescales that arsenic is mobilized and immobilized in response to hydrologic change. Along a beach, modeling and long-term monitoring show the influence of tidal to seasonal changes in the mixing zone between discharging fresh groundwater and seawater in the intertidal beach aquifer and associated impacts on biogeochemical reactivity and denitrification. In a saltmarsh, hydrologic changes alter carbon dynamics, with implications for the discharge of dissolved organic carbon to the ocean and export of carbon dioxide and methane to the atmosphere. Understanding the impacts of hydrologic changes on both long and short timescales is essential for improving our ability to predict the global biogeochemical impacts of a changing climate.

Effect of desliming of sulphide-rich mill tailings on the long-term strength of cemented paste backfill.

PubMed

Ercikdi, Bayram; Baki, Hakan; İzki, Muhammet

2013-01-30

This paper presents the effect of desliming on the short- and long-term strength, stability and rheological properties of cemented paste backfill (CPB) produced from two different mill tailings. A 28-day unconfined compressive strength (UCS) of ≥1.0 MPa and the maintenance of stability over 224 days of curing were selected as the design criteria for the evaluation of paste backfill performance. Desliming induced some changes in the physical, chemical, mineralogical and rheological properties of the tailings. CPB mixture of the deslimed tailings achieved the required consistency at a lower water to cement ratio. The short-term UCSs of CPB samples of the deslimed tailings were found to be 30-100% higher than those samples of the reference tailings at all the binder dosages and curing times. CPB samples of the deslimed tailings achieved the long-term stability at relatively low binder dosages (e.g. 5 wt% c.f. ≥6.1% for the reference tailings). It was also estimated that desliming could allow a 13.4-23.1% reduction in the binder consumption depending apparently on the inherent characteristics of the tailings. Over the curing period, generation of sulphate and acid by the oxidation of pyrite present in the tailings was also monitored to correlate with the strength losses observed in the long term. Scanning electron microscope (SEM) and Mercury Intrusion Porosimetry (MIP) analyses provided an insight into the microstructure of CPB and the formation of secondary mineral phases (i.e. gypsum) confirming the beneficial effect of desliming. These findings suggest that desliming can be suitably exploited for CPB of sulphide-rich mill tailings to improve the strength and stability particularly in the long term and to reduce binder consumption. Copyright © 2012 Elsevier Ltd. All rights reserved.

InSAR Surface Deformation and Source Modelling at Semisopochnoi Island During the 2014 and 2015 Seismic Swarms with Constraints from Geochemical and Seismic Analysis

NASA Astrophysics Data System (ADS)

DeGrandpre, K.; Pesicek, J. D.; Lu, Z.

2017-12-01

During the summer of 2014 and the early spring of 2015 two notable increases in seismic activity at Semisopochnoi Island in the western Aleutian islands were recorded on AVO seismometers on Semisopochnoi and neighboring islands. These seismic swarms did not lead to an eruption. This study employs interferometric synthetic aperture radar (InSAR) techniques using TerraSAR-X images in conjunction with more accurately relocating the recorded seismic events through simultaneous inversion of event travel times and a three-dimensional velocity model using tomoDD. The InSAR images exhibit surprising coherence and an island wide spatial distribution of inflation that is then used in Mogi, Okada, spheroid, and ellipsoid source models in order to define the three-dimensional location and volume change required for a source at the volcano to produce the observed surface deformation. The tomoDD relocations provide a more accurate and realistic three-dimensional velocity model as well as a tighter clustering of events for both swarms that clearly outline a linear seismic void within the larger group of shallow (<10 km) seismicity. The source models are fit to this void and pressure estimates from geochemical analysis are used to verify the storage depth of magmas at Semisopochnoi. Comparisons of calculated source cavity, magma injection, and surface deformation volumes are made in order to assess the reality behind the various modelling estimates. Incorporating geochemical and seismic data to provide constraints on surface deformation source inversions provides an interdisciplinary approach that can be used to make more accurate interpretations of dynamic observations.

Estimation of the geochemical threshold and its statistical significance

USGS Publications Warehouse

Miesch, A.T.

1981-01-01

A statistic is proposed for estimating the geochemical threshold and its statistical significance, or it may be used to identify a group of extreme values that can be tested for significance by other means. The statistic is the maximum gap between adjacent values in an ordered array after each gap has been adjusted for the expected frequency. The values in the ordered array are geochemical values transformed by either ln(?? - ??) or ln(?? - ??) and then standardized so that the mean is zero and the variance is unity. The expected frequency is taken from a fitted normal curve with unit area. The midpoint of an adjusted gap that exceeds the corresponding critical value may be taken as an estimate of the geochemical threshold, and the associated probability indicates the likelihood that the threshold separates two geochemical populations. The adjusted gap test may fail to identify threshold values if the variation tends to be continuous from background values to the higher values that reflect mineralized ground. However, the test will serve to identify other anomalies that may be too subtle to have been noted by other means. ?? 1981.

Geochemical investigation of UMTRAP designated site at Durango, Colorado

DOE Office of Scientific and Technical Information (OSTI.GOV)

Markos, G.; Bush, K.J.

1983-09-01

This report is the result of a geochemical investigation of the former uranium mill and tailings site at Durango, Colorado. This is one in a series of site specific geochemical investigations performed on the inactive uranium mill tailings included in the UMTRA Project. The objectives of the investigation are to characterize the geochemistry, to determine the contaminant distribution resulting from the former milling activities and tailings, and to infer chemical pathways and transport mechanisms from the contaminant distribution. The results will be used to model contaminant migration and to develop criteria for long-term containment media such as a cover systemmore » which is impermeable to contaminant migration. This report assumes a familiarity with the hydrologic conditions of the site and the geochemical concepts underlying the investigation. The results reported are based on a one-time sampling of waters and solid material from the background, the area adjacent to the site, and the site. The solid samples are water extracted remove easily soluble salts and acids extracted to remove cabonates and hydroxides. The water extracts and solid samples were analyzed for the major and trace elements. A limited number of samples were analyzed for radiological components. The report includes the methods of sampling, sample processing, analysis, and data interpretation. Three major conclusions are: (1) carbonate salts and low TDS characterize the tailings; (2) the adjacent area and raffinate ponds contain contaminants deposited by a single event of fluid permeation of the soils; and (3) the Animas River adjacent to the site has elevated gross alpha activity attributed to /sup 226/Ra in the sediments derived from the tailings or milling activities.« less

Geochemical and Sm-Nd isotope-geochemical patterns of metavolcanic rocks, diabase, and metagabbroids on the northeastern flank of the South Mongolian-Khingan orogenic belt

NASA Astrophysics Data System (ADS)

Smirnov, Yu. V.; Sorokin, A. A.

2017-05-01

The first results of geochemical and Sm-Nd isotope-geochemical studies of metavolcanic rocks, metagabbroids, and diabase of the Nora-Sukhotino terrane, the least studied part of the South Mongolian-Khingan orogenic belt in the system of the Central Asian orogenic belt are reported. It is established that the basic rocks composing this terrane include varieties comparable with E-MORB, tholeiitic, and calc-alkaline basalt of island arc, calc-alkaline gabbro-diabase, and gabbroids of island arcs. Most likely, these formations should be correlated with metabasalt and associated Late Ordovician gabbro-amphibolite of the Sukdulkin "block" of the South Mongolian-Khingan orogenic belt, which are similar to tholeiite of intraplate island arcs by their geochemical characteristics.

Leveling data in geochemical mapping: scope of application, pros and cons of existing methods

NASA Astrophysics Data System (ADS)

Pereira, Benoît; Vandeuren, Aubry; Sonnet, Philippe

2017-04-01

Geochemical mapping successfully met a range of needs from mineral exploration to environmental management. In Europe and around the world numerous geochemical datasets already exist. These datasets may originate from geochemical mapping projects or from the collection of sample analyses requested by environmental protection regulatory bodies. Combining datasets can be highly beneficial for establishing geochemical maps with increased resolution and/or coverage area. However this practice requires assessing the equivalence between datasets and, if needed, applying data leveling to remove possible biases between datasets. In the literature, several procedures for assessing dataset equivalence and leveling data are proposed. Daneshfar & Cameron (1998) proposed a method for the leveling of two adjacent datasets while Pereira et al. (2016) proposed two methods for the leveling of datasets that contain records located within the same geographical area. Each discussed method requires its own set of assumptions (underlying populations of data, spatial distribution of data, etc.). Here we propose to discuss the scope of application, pros, cons and practical recommendations for each method. This work is illustrated with several case studies in Wallonia (Southern Belgium) and in Europe involving trace element geochemical datasets. References: Daneshfar, B. & Cameron, E. (1998), Leveling geochemical data between map sheets, Journal of Geochemical Exploration 63(3), 189-201. Pereira, B.; Vandeuren, A.; Govaerts, B. B. & Sonnet, P. (2016), Assessing dataset equivalence and leveling data in geochemical mapping, Journal of Geochemical Exploration 168, 36-48.

Baseline and premining geochemical characterization of mined sites

USGS Publications Warehouse

Nordstrom, D. Kirk

2015-01-01

A rational goal for environmental restoration of new, active, or inactive mine sites would be ‘natural background’ or the environmental conditions that existed before any mining activities or other related anthropogenic activities. In a strictly technical sense, there is no such thing as natural background (or entirely non-anthropogenic) existing today because there is no part of the planet earth that has not had at least some chemical disturbance from anthropogenic activities. Hence, the terms ‘baseline’ and ‘pre-mining’ are preferred to describe these conditions. Baseline conditions are those that existed at the time of the characterization which could be pre-mining, during mining, or post-mining. Protocols for geochemically characterizing pre-mining conditions are not well-documented for sites already mined but there are two approaches that seem most direct and least ambiguous. One is characterization of analog sites along with judicious application of geochemical modeling. The other is reactive-transport modeling (based on careful synoptic sampling with tracer-injection) and subtracting inputs from known mining and mineral processing. Several examples of acidic drainage are described from around the world documenting the range of water compositions produced from pyrite oxidation in the absence of mining. These analog sites provide insight to the processes forming mineralized waters in areas untouched by mining. Natural analog water-chemistry data is compared with the higher metal concentrations, metal fluxes, and weathering rates found in mined areas in the few places where comparisons are possible. The differences are generally 1–3 orders of magnitude higher for acid mine drainage.

Reply to 'Comments on upscaling geochemical reaction rates usingpore-scale network modeling' by Peter C. Lichtner and Qinjun Kang

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Li; Peters, Catherine A.; Celia, Michael A.

2006-05-03

Our paper "Upscaling geochemical reaction rates usingpore-scale network modeling" presents a novel application of pore-scalenetwork modeling to upscale mineral dissolution and precipitationreaction rates from the pore scale to the continuum scale, anddemonstrates the methodology by analyzing the scaling behavior ofanorthite and kaolinite reaction kinetics under conditions related to CO2sequestration. We conclude that under highly acidic conditions relevantto CO2 sequestration, the traditional continuum-based methodology may notcapture the spatial variation in concentrations from pore to pore, andscaling tools may be important in correctly modeling reactive transportprocesses in such systems. This work addresses the important butdifficult question of scaling mineral dissolution and precipitationreactionmore » kinetics, which is often ignored in fields such as geochemistry,water resources, and contaminant hydrology. Although scaling of physicalprocesses has been studied for almost three decades, very few studieshave examined the scaling issues related to chemical processes, despitetheir importance in governing the transport and fate of contaminants insubsurface systems.« less

Geochemical evaluation of Niger Delta sedimentary organic rocks: a new insight

NASA Astrophysics Data System (ADS)

Akinlua, Akinsehinwa; Torto, Nelson

2011-09-01

A geochemical evaluation of Niger Delta organic matter was carried out using supercritical fluid extraction (SFE) sample preparation procedure. Comparison of geochemical significance of gas chromatographic data of rock extracts of SFE with those of Soxhlet extraction method from previous studies was made in order to establish the usefulness of SFE in geochemical exploration. The assessment of geochemical character of the rock samples from the comparison and interpretation of other geochemical parameters were used to give more insights into understanding the source rocks characteristics of onshore and shelf portions of the Niger Delta Basin. The results of the gas chromatographic (GC) analysis of the rock extracts across the lithostratigraphic units show that Pr/Ph, Pr/nC17, Pr/nC18, CPI and odd/even preference ranged from 0.07 to 12.39, 0.04 to 6.66, 0.05 to 13.80, 0.12 to 8.4 and 0.06 to 8.12, respectively. The Rock-Eval pyrolysis data and geochemical ratios and parameters calculated from the GC data showed that most of the samples are mature and have strong terrestrial provenance while a few samples have strong marine provenance. The few marine source rocks are located in the deeper depth horizon. Pr/Ph and standard geochemical plots indicate that most of samples were derived from organic matter deposited in less reducing conditions, i.e. more of oxidizing conditions while a few samples have predominantly influence of reducing conditions. The results of trace metal analysis of older samples from Agbada Formation also indicate marine and mixed organic matter input deposited in less reducing conditions. The results obtained in this study are comparable with those obtained from previous studies when Soxhlet extraction method was used and also indicated the presence of more than one petroleum systems in the Niger Delta.

Merging Hydrologic, Geochemical, and Geophysical Approaches to Understand the Regolith Architecture of a Deeply Weathered Piedmont Critical Zone

NASA Astrophysics Data System (ADS)

Cosans, C.; Moore, J.; Harman, C. J.

2017-12-01

Located in the deeply weathered Piedmont in Maryland, Pond Branch has a rich legacy of hydrological and geochemical research dating back to the first geochemical mass balance study published in 1970. More recently, geophysical investigations including seismic and electrical resistivity tomography have characterized the subsurface at Pond Branch and contributed to new hypotheses about critical zone evolution. Heterogeneity in electrical resistivity in the shallow subsurface may suggest disparate flow paths for recharge, with some regions with low hydraulic conductivity generating perched flow, while other hillslope sections recharge to the much deeper regolith boundary. These shallow and deep flow paths are hypothesized to be somewhat hydrologically and chemically connected, with the spatially and temporally discontinuous connections resulting in different hydraulic responses to recharge and different concentrations of weathering solutes. To test this hypothesis, we combined modeling and field approaches. We modeled weathering solutes along the hypothesized flow paths using PFLOTRAN. We measured hydrologic gradients in the hillslopes and riparian zone using piezometer water levels. We collected geochemical data including major ions and silica. Weathering solute concentrations were measured directly in the precipitation, hillslope springs, and the riparian zone for comparison to modeled concentration values. End member mixing methods were used to determine contributions of precipitation, hillslopes, and riparian zone to the stream. Combining geophysical, geochemical, and hydrological methods may offer insights into the source of stream water and controls on chemical weathering. Previous hypotheses that Piedmont critical zone architecture results from a balance of erosion, soil, and weathering front advance rates cannot account for the inverted regolith structure observed through seismic investigations at Pond Branch. Recent alternative hypotheses including weathering

Alaska Geochemical Database - Mineral Exploration Tool for the 21st Century - PDF of presentation

USGS Publications Warehouse

Granitto, Matthew; Schmidt, Jeanine M.; Labay, Keith A.; Shew, Nora B.; Gamble, Bruce M.

2012-01-01

The U.S. Geological Survey has created a geochemical database of geologic material samples collected in Alaska. This database is readily accessible to anyone with access to the Internet. Designed as a tool for mineral or environmental assessment, land management, or mineral exploration, the initial version of the Alaska Geochemical Database - U.S. Geological Survey Data Series 637 - contains geochemical, geologic, and geospatial data for 264,158 samples collected from 1962-2009: 108,909 rock samples; 92,701 sediment samples; 48,209 heavy-mineral-concentrate samples; 6,869 soil samples; and 7,470 mineral samples. In addition, the Alaska Geochemical Database contains mineralogic data for 18,138 nonmagnetic-fraction heavy mineral concentrates, making it the first U.S. Geological Survey database of this scope that contains both geochemical and mineralogic data. Examples from the Alaska Range will illustrate potential uses of the Alaska Geochemical Database in mineral exploration. Data from the Alaska Geochemical Database have been extensively checked for accuracy of sample media description, sample site location, and analytical method using U.S. Geological Survey sample-submittal archives and U.S. Geological Survey publications (plus field notebooks and sample site compilation base maps from the Alaska Technical Data Unit in Anchorage, Alaska). The database is also the repository for nearly all previously released U.S. Geological Survey Alaska geochemical datasets. Although the Alaska Geochemical Database is a fully relational database in Microsoft® Access 2003 and 2010 formats, these same data are also provided as a series of spreadsheet files in Microsoft® Excel 2003 and 2010 formats, and as ASCII text files. A DVD version of the Alaska Geochemical Database was released in October 2011, as U.S. Geological Survey Data Series 637, and data downloads are available at http://pubs.usgs.gov/ds/637/. Also, all Alaska Geochemical Database data have been incorporated into

Hydrothermal gases in a shallow aquifer at Mt. Amiata, Italy: insights from stable isotopes and geochemical modelling.

PubMed

Pierotti, Lisa; Cortecci, Gianni; Gherardi, Fabrizio

2016-01-01

We investigate the interaction between hydrothermal gases and groundwater in a major aquifer exploited for potable supply in the geothermal-volcanic area of Mt. Amiata, Central Italy. Two springs and two wells located on different sides of the volcanic edifice have been repeatedly sampled over the last 11 years. More than 160 chemical analyses and 10 isotopic analyses of total dissolved carbon (δ(13)C - total dissolved inorganic carbon (TDIC) = -15.9 to -7.8 ‰ vs. V-PDB) and sulphate (δ(34)S-SO4 = -6.9 to 5.1 ‰ vs. V-CDT) have been processed with geochemical modelling techniques. Best-fitting conditions between analytical data and model outputs have been achieved by numerical optimization, allowing for a quantitative description of gas-water-rock interactions occurring in this aquifer. Numerical calculations support a conceptual model that considers water-rock interactions to occur in the volcanic aquifer after inflow of deep-seated gases (CO2(g) and H2S(g)), and total conversion of H2S(g) to SO4, in the absence of mixing with geothermal waters from reservoirs currently exploited for electricity generation.

Generic Procedure for Coupling the PHREEQC Geochemical Modeling Framework with Flow and Solute Transport Simulators

NASA Astrophysics Data System (ADS)

Wissmeier, L. C.; Barry, D. A.

2009-12-01

Computer simulations of water availability and quality play an important role in state-of-the-art water resources management. However, many of the most utilized software programs focus either on physical flow and transport phenomena (e.g., MODFLOW, MT3DMS, FEFLOW, HYDRUS) or on geochemical reactions (e.g., MINTEQ, PHREEQC, CHESS, ORCHESTRA). In recent years, several couplings between both genres of programs evolved in order to consider interactions between flow and biogeochemical reactivity (e.g., HP1, PHWAT). Software coupling procedures can be categorized as ‘close couplings’, where programs pass information via the memory stack at runtime, and ‘remote couplings’, where the information is exchanged at each time step via input/output files. The former generally involves modifications of software codes and therefore expert programming skills are required. We present a generic recipe for remotely coupling the PHREEQC geochemical modeling framework and flow and solute transport (FST) simulators. The iterative scheme relies on operator splitting with continuous re-initialization of PHREEQC and the FST of choice at each time step. Since PHREEQC calculates the geochemistry of aqueous solutions in contact with soil minerals, the procedure is primarily designed for couplings to FST’s for liquid phase flow in natural environments. It requires the accessibility of initial conditions and numerical parameters such as time and space discretization in the input text file for the FST and control of the FST via commands to the operating system (batch on Windows; bash/shell on Unix/Linux). The coupling procedure is based on PHREEQC’s capability to save the state of a simulation with all solid, liquid and gaseous species as a PHREEQC input file by making use of the dump file option in the TRANSPORT keyword. The output from one reaction calculation step is therefore reused as input for the following reaction step where changes in element amounts due to advection

Hydrogeological modeling constraints provided by geophysical and geochemical mapping of a chlorinated ethenes plume in northern France

NASA Astrophysics Data System (ADS)

Razafindratsima, Stephen; Guérin, Roger; Bendjoudi, Hocine; de Marsily, Ghislain

2014-09-01

A methodological approach is described which combines geophysical and geochemical data to delineate the extent of a chlorinated ethenes plume in northern France; the methodology was used to calibrate a hydrogeological model of the contaminants' migration and degradation. The existence of strong reducing conditions in some parts of the aquifer is first determined by measuring in situ the redox potential and dissolved oxygen, dissolved ferrous iron and chloride concentrations. Electrical resistivity imaging and electromagnetic mapping, using the Slingram method, are then used to determine the shape of the pollutant plume. A decreasing empirical exponential relation between measured chloride concentrations in the water and aquifer electrical resistivity is observed; the resistivity formation factor calculated at a few points also shows a major contribution of chloride concentration in the resistivity of the saturated porous medium. MODFLOW software and MT3D99 first-order parent-daughter chain reaction and the RT3D aerobic-anaerobic model for tetrachloroethene (PCE)/trichloroethene (TCE) dechlorination are finally used for a first attempt at modeling the degradation of the chlorinated ethenes. After calibration, the distribution of the chlorinated ethenes and their degradation products simulated with the model approximately reflects the mean measured values in the observation wells, confirming the data-derived image of the plume.

The geochemical transformation of soils by agriculture and its dependence on soil erosion: An application of the geochemical mass balance approach.

PubMed

Yoo, Kyungsoo; Fisher, Beth; Ji, Junling; Aufdenkampe, Anthony; Klaminder, Jonatan

2015-07-15

Agricultural activities alter elemental budgets of soils and thus their long-term geochemical development and suitability for food production. This study examined the utility of a geochemical mass balance approach that has been frequently used for understanding geochemical aspect of soil formation, but has not previously been applied to agricultural settings. Protected forest served as a reference to quantify the cumulative fluxes of Ca, P, K, and Pb at a nearby tilled crop land. This comparison was made at two sites with contrasting erosional environments: relatively flat Coastal Plain in Delaware vs. hilly Piedmont in Pennsylvania. Mass balance calculations suggested that liming not only replenished the Ca lost prior to agricultural practice but also added substantial surplus at both sites. At the relatively slowly eroding Coastal Plain site, the agricultural soil exhibited enrichment of P and less depletion of K, while both elements were depleted in the forest soil. At the rapidly eroding Piedmont site, erosion inhibited P enrichment. In similar, agricultural Pb contamination appeared to have resulted in Pb enrichment in the relatively slowly eroding Coastal Plain agricultural soil, while not in the rapidly eroding Piedmont soils. We conclude that agricultural practices transform soils into a new geochemical state where current levels of Ca, P, and Pb exceed those provided by the local soil minerals, but such impacts are significantly offset by soil erosion. Copyright © 2015 Elsevier B.V. All rights reserved.

Geochemical Characterization of the Upper and Middle Floridan Aquifer System, South Florida

NASA Astrophysics Data System (ADS)

Mirecki, J.; Richardson, E.; Bennett, M.; Hendel, J.

2008-05-01

Our study focus is to characterize the water quality and geochemical environment of the Floridan Aquifer System (FAS) throughout the regional flowpath. A synoptic survey of 21 wells (n=15, upper FAS; n=6 middle FAS) was supplemented by additional samples (n=11) obtained during exploratory well development at 4 aquifer storage recovery (ASR) pilot sites. Synoptic survey samples were analyzed intensively, yielding a dataset that consists of major and trace dissolved constituents (including metals), stable isotopes (δ18O, δ13C, δD, δ34S in sulfate and sulfide), carbon species (carbonate alkalinity and organic carbon), uranium-series radionuclides, nutrients, and selected microbes and pathogens. The objectives of this study are three-fold: 1) to provide baseline water-quality and geochemical information prior to initiation of ASR activities that are part of the Comprehensive Everglades Restoration Plan; 2) to quantify the major controls on geochemical evolution along upper and middle FAS flowpaths using geochemical modeling methods; and 3) to identify areas where water- quality may limit the feasibility of ASR methods in the FAS. Preliminary interpretations water quality changes along the regional FAS flowpath can be summarized as follows. Concentrations of dissolved constituents increase from north to south along the flow path; generally, the upper FAS has lower total dissolved solids than the middle FAS at locations where well pairs were analyzed. The redox environment changes from oxic to strongly anoxic, very close to the recharge area. Redox measurements, dissolved iron, sulfide, and sulfur isotope data are consistent with sulfate-reducing conditions. Uranium-series isotope concentrations and activities generally are below regulatory criteria, with few exceptions in both the upper and middle FAS. Areas with greater radionuclide activity occur primarily at distal flowpath locations or at the coast.

Geochemical effects on the behavior of LLW radionuclides in soil/groundwater environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krupka, K.M.; Sterne, R.J.

1995-12-31

Assessing the migration potential of radionuclides leached from low-level radioactive waste (LLW) and decommissioning sites necessitates information on the effects of sorption and precipitation on the concentrations of dissolved radionuclides. Such an assessment requires that the geochemical processes of aqueous speciation, complexation, oxidation/reduction, and ion exchange be taken into account. The Pacific Northwest National Laboratory (PNNL) is providing technical support to the U.S. Nuclear Regulatory Commission (NRC) for defining the solubility and sorption behavior of radionuclides in soil/ground-water environments associated with engineered cementitious LLW disposal systems and decommissioning sites. Geochemical modeling is being used to predict solubility limits for radionuclidesmore » under geochemical conditions associated with these environments. The solubility limits are being used as maximum concentration limits in performance assessment calculations describing the release of contaminants from waste sources. Available data were compiled regarding the sorption potential of radionuclides onto {open_quotes}fresh{close_quotes} cement/concrete where the expected pH of the cement pore waters will equal to or exceed 10. Based on information gleaned from the literature, a list of preferred minimum distribution coefficients (Kd`s) was developed for these radionuclides. The K{sub d} values are specific to the chemical environments associated with the evolution of the compositions of cement/concrete pore waters.« less

Preliminary Reactive Geochemical Transport Modeling Study on Changes in Water Chemistry Induced by CO2 Injection at Frio Pilot Test Site

NASA Astrophysics Data System (ADS)

Xu, T.; Kharaka, Y.; Benson, S.

2006-12-01

A total of 1600 tons of CO2 were injected into the Frio ~{!0~}C~{!1~} sandstone layer at a depth of 1500 m over a period of 10 days. The pilot, located near Dayton, Texas, employed one injection well and one observation well, separated laterally by about 30 m. Each well was perforated over 6 m in the upper portion of the 23-m thick sandstone. Fluid samples were taken from both wells before, during, and after the injection. Following CO2 breakthrough, observations indicate drops in pH (6.5 to 5.7), pronounced increases in concentrations of HCO3- (100 to 3000 mg/L), in Fe (30 to 1100), and dissolved organic carbon. Numerical modeling was used in this study to understand changes of aqueous HCO3- and Fe caused by CO2 injection. The general multiphase reactive geochemical transport simulator TOUGHREACT was used, which includes new fluid property module ECO2N with an accurate description of the thermophysical properties of mixtures of water, brine, and CO2 at conditions of interest for CO2 storage. A calibrated 1-D radial well flow model was employed for the present reactive geochemical transport simulations. Mineral composition used was taken from literatures relevant to Frio sandstone. Increases in HCO3- concentration were well reproduced by an initial simulation. Several scenarios were used to capture increases in Fe concentration including (1) dissolution of carbonate minerals, (2) dissolution of iron oxyhydroxides, (3) de-sorption of previously coated Fe. Future modeling, laboratory and field investigations are proposed to better understand the CO2-brine-mineral interactions at the Frio site. Results from this study could have broad implication for subsurface storage of CO2 and potential water quality impacts.

Modelling of the petroleum formation in the Mahakam sediments (Indonesia): Organic geochemical controls of the results

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brosse, E.; Burris, J.; Ouidin, J.L.

1990-06-01

Since the Miocene, the delta of the Mahakam River has accumulated thousands of meters of sediments in the eastern part of the Kutei Basin (Kalimantan, Indonesia). Source-rock candidates are the coals of the deltaic plain and several types of shales, mainly the delta front/prodelta area. Organic matter basically derives from higher plants, but each source facies presents important intrinsic variations of petroleum potential. These variations are overprinted by subsequent maturation trends. Geochemical and petrographical data are integrated on the general framework provided by a new synthetic interpretation of the sedimentary sequences, relying upon the concepts of seismic stratigraphy. From coremore » samples at a given level of maturation, the variations of several organic parameters are discussed in relation to the depositional paleoenvironment and to the possible precursors. 1D and 2D numerical routines are used to reconstruct the maturation history of source rocks. These tools are based upon a kinetic modeling of kerogen cracking. Model outputs are compared with observed maturation trends. The understanding of the initial organic facies distribution provides precise constraints in the selection of a homogenous samples set for this comparison purpose.« less

Model-Based Analysis of the Role of Biological, Hydrological and Geochemical Factors Affecting Uranium Bioremediation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Jiao; Scheibe, Timothy D.; Mahadevan, Radhakrishnan

2011-01-24

Uranium contamination is a serious concern at several sites motivating the development of novel treatment strategies such as the Geobacter-mediated reductive immobilization of uranium. However, this bioremediation strategy has not yet been optimized for the sustained uranium removal. While several reactive-transport models have been developed to represent Geobacter-mediated bioremediation of uranium, these models often lack the detailed quantitative description of the microbial process (e.g., biomass build-up in both groundwater and sediments, electron transport system, etc.) and the interaction between biogeochemical and hydrological process. In this study, a novel multi-scale model was developed by integrating our recent model on electron capacitancemore » of Geobacter (Zhao et al., 2010) with a comprehensive simulator of coupled fluid flow, hydrologic transport, heat transfer, and biogeochemical reactions. This mechanistic reactive-transport model accurately reproduces the experimental data for the bioremediation of uranium with acetate amendment. We subsequently performed global sensitivity analysis with the reactive-transport model in order to identify the main sources of prediction uncertainty caused by synergistic effects of biological, geochemical, and hydrological processes. The proposed approach successfully captured significant contributing factors across time and space, thereby improving the structure and parameterization of the comprehensive reactive-transport model. The global sensitivity analysis also provides a potentially useful tool to evaluate uranium bioremediation strategy. The simulations suggest that under difficult environments (e.g., highly contaminated with U(VI) at a high migration rate of solutes), the efficiency of uranium removal can be improved by adding Geobacter species to the contaminated site (bioaugmentation) in conjunction with the addition of electron donor (biostimulation). The simulations also highlight the interactive

Geochemical sampling in arid environments by the U.S. Geological Survey

USGS Publications Warehouse

Hinkle, Margaret E.

1988-01-01

The U.S. Geological Survey (USGS) is responsible for the geochemical evaluations used for mineral resource assessments of large tracts of public lands in the Western United States. Many of these lands are administered by the Bureau of Land Management (BLM) and are studied to determine their suitability or nonsuitability for wilderness designation. Much of the Western United States is arid or semiarid. This report discusses various geochemical sample media that have been used for evaluating areas in arid environments and describes case histories in BLM wilderness study areas in which stream-sediment and heavy-mineral-concentrate sample media were compared. As a result of these case history studies, the nonmagnetic fraction of panned heavy-mineral concentrates was selected as the most effective medium for reconnaissance geochemical sampling for resources other than gold, in arid areas. Nonmagnetic heavy-mineral-concentrate samples provide the primary analytical information currently used in geochemical interpretations of mineral resource potential assessment of BLM lands.

A geochemical and geophysical reappraisal to the significance of the recent unrest at Campi Flegrei caldera (Southern Italy)

NASA Astrophysics Data System (ADS)

Moretti, Roberto; De Natale, Giuseppe; Troise, Claudia

2017-03-01

Volcanic unrest at calderas involves complex interaction between magma, hydrothermal fluids, and crustal stress and strain. Campi Flegrei caldera (CFc), located in the Naples (Italy) area and characterized by the highest volcanic risk on Earth for the extreme urbanization, undergoes unrest phenomena involving several meters of uplift and intense shallow microseismicity since several decades. Despite unrest episodes display in the last decade only moderate ground deformation and seismicity, current interpretations of geochemical data point to a highly pressurized hydrothermal system. We show that at CFc, the usual assumption of vapor-liquid coexistence in the fumarole plumes leads to largely overestimated hydrothermal pressures and, accordingly, interpretations of elevated unrest. By relaxing unconstrained geochemical assumptions, we infer an alternative model yielding better agreement between geophysical and geochemical observations. The model reconciles discrepancies between what observed (1) for two decades since the 1982-1984 large unrest, when shallow magma was supplying heat and fluids to the hydrothermal system, and (2) in the last decade. Compared to the 1980's unrest, the post-2005 phenomena are characterized by much lower aquifers overpressure and magmatic involvement, as indicated by geophysical data and despite large changes in geochemical indicators. Our interpretation points out a model in which shallow sills, intruded during 1969-1984, have completely cooled, so that fumarole emissions are affected now by deeper, CO2-richer, magmatic gases producing the modest heating and overpressure of the hydrothermal system. Our results have important implications on the short-term eruption hazard assessment and on the best strategies for monitoring and interpreting geochemical data.