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At least 577 records · Page 32Linked to original sources
USGS1953

Systematic variation of rare earths in monazite

Ten monazites from widely scattered localities have been analyzed for La, Ce, Pr, Nd, Sm, Gd, Y and Th by means of a combined chemical and emission spectrographic method. The analytical results, calculated to atomic percent of total rare earths (thorium excluded), show a considerable variation in the proportions of every element except praseodymium, which is relatively constant. The general variation trends of the elements may be calculated by assuming that the monazites represent different stages in a fractional precipitation process, and by assuming that there is a gradational increase in the precipitability of rare earth elements with decreasing ionic radius. Fractional precipitation brings about an increase in lanthanum and cerium, little change in praseodymium, and a decrease in neodymium, samarium, gadolinium, and yttrium. Deviations from the calculated lines of variation consist of a simultaneous, abnormal increase or decrease in the proportions of cerium, praseodymium, and neodymium with antipathetic decrease or increase in the proportions of the other elements. These deviations are ascribed to abnormally high or low temperatures that affect the precipitability of the central trio of elements (Ce, Pr, Nd) relatively more than that of the other elements. The following semiquantitative rules have been found useful in describing the composition of rare earths from monazite: 1. The sum of lanthanum and neodymium is very nearly a constant at 42 ± 2 atomic percent. 2. Praseodymium is very nearly constant at 5 ± 1 atomic percent. 3. The sum of Ce, Sm, Gd, and Y is very nearly a constant at 53 ± 3 atomic percent. No correlation could be established between the content of Th and that of any of the rare earth elements.

Geochimica et Cosmochimica Acta↗
USGS2008

Dissolved and labile concentrations of Cd, Cu, Pb, and Zn in the South Fork Coeur d'Alene River, Idaho: Comparisons among chemical equilibrium models and implications for biotic ligand models

In order to evaluate thermodynamic speciation calculations inherent in biotic ligand models, the speciation of dissolved Cd, Cu, Pb, and Zn in aquatic systems influenced by historical mining activities is examined using equilibrium computer models and the diffusive gradients in thin films (DGT) technique. Several metal/organic-matter complexation models, including WHAM VI, NICA-Donnan, and Stockholm Humic model (SHM), are used in combination with inorganic speciation models to calculate the thermodynamic speciation of dissolved metals and concentrations of metal associated with biotic ligands (e.g., fish gills). Maximum dynamic metal concentrations, determined from total dissolved metal concentrations and thermodynamic speciation calculations, are compared with labile metal concentrations measured by DGT to assess which metal/organic-matter complexation model best describes metal speciation and, thereby, biotic ligand speciation, in the studied systems. Results indicate that the choice of model that defines metal/organic-matter interactions does not affect calculated concentrations of Cd and Zn associated with biotic ligands for geochemical conditions in the study area, whereas concentrations of Cu and Pb associated with biotic ligands depend on whether the speciation calculations use WHAM VI, NICA-Donnan, or SHM. Agreement between labile metal concentrations and dynamic metal concentrations occurs when WHAM VI is used to calculate Cu speciation and SHM is used to calculate Pb speciation. Additional work in systems that contain wide ranges in concentrations of multiple metals should incorporate analytical speciation methods, such as DGT, to constrain the speciation component of biotic ligand models.

Idaho↗
USGS2012

Review and update of the applications of organic petrology: Part 1, geological applications

Organic petrology developed as coal petrology at the beginning of the 20th century dedicated mainly to the study of coals because of their utilization in industry. Coal petrology was then considered a branch of coal science. Later, with the development of specialized nomenclature, classification of coal components, and the standardization and improvement of analytical (microscopical) methods, this discipline expanded in interests and name, becoming organic petrology. Organic petrology carries a broader context, being as well a tool applied in the study of dispersed organic matter in sedimentary rocks due to its importance in exploration for fossil fuel resources. At present, organic petrology is a discipline widely recognized for its role in fundamental and applied research with respect to both coal utilization and in geosciences. Throughout the 20th century several important monographs have been published on the discipline of organic petrology, including “Stach's textbook of coal petrology” (1st edition 1935, 2nd 1975, 3rd 1982), updated as the more general “Organic petrology” by Taylor et al. (1998). More recently, the text “Applied coal petrology: the role of petrology in coal utilization” was published by Suárez-Ruiz and Crelling (2008). This review is the first in a two-part review series that describes and updates the role of organic petrology in geosciences. A second part complementing this one and focused on the applications of organic petrology to other scientific fields will follow.

International Journal of Coal Geology↗
USGS2021

A systematic review of potential habitat suitability for the jaguar Panthera onca in central Arizona and New Mexico, USA

In April 2019, the U.S. Fish and Wildlife Service (USFWS) released its recovery plan for the jaguar Panthera onca after several decades of discussion, litigation and controversy about the status of the species in the USA. The USFWS estimated that potential habitat, south of the Interstate-10 highway in Arizona and New Mexico, had a carrying capacity of c. six jaguars, and so focused its recovery programme on areas south of the USA–Mexico border. Here we present a systematic review of the modelling and assessment efforts over the last 25 years, with a focus on areas north of Interstate-10 in Arizona and New Mexico, outside the recovery unit considered by the USFWS. Despite differences in data inputs, methods, and analytical extent, the nine previous studies found support for potential suitable jaguar habitat in the central mountain ranges of Arizona and New Mexico. Applying slightly modified versions of the USFWS model and recalculating an Arizona-focused model over both states provided additional confirmation. Extending the area of consideration also substantially raised the carrying capacity of habitats in Arizona and New Mexico, from six to 90 or 151 adult jaguars, using the modified USFWS models. This review demonstrates the crucial ways in which choosing the extent of analysis influences the conclusions of a conservation plan. More importantly, it opens a new opportunity for jaguar conservation in North America that could help address threats from habitat losses, climate change and border infrastructure.

Arizona, New Mexico↗
USGS2003

Pumping‐induced leakage in a bounded aquifer: An example of a scale‐invariant phenomenon

A new approach is presented for calculation of the volume of pumping‐induced leakage entering an aquifer as a function of time. This approach simplifies the total leakage calculation by extending analytical‐based methods developed for infinite systems to bounded aquifers of any size. The simplification is possible because of the relationship between drawdown and leakage in aquifers laterally bounded by impermeable formations. This relationship produces a scale‐invariant total leakage; i.e., the volume of leakage as a function of time does not change with the size of the aquifer or with the location of the pumping well. Two examples and image well theory are used to demonstrate and prove, respectively, the generality of this interesting phenomenon.

Water Resources Research↗
USGS2013

TanA: a fluorogenic probe for thiaminase activity

A fluorogenic thiamine analogue is presented as a fluorescent probe for thiaminase activity. The emission of the fluorophore is quenched by photoinduced electron transfer (PET) to the N-substituted pyridinium portion of the probe. Action of the enzyme releases the free pyridine group causing a substantial increase in fluorescence.

Analytical Methods↗
USGS2003

Post-seismic relaxation theory on laterally heterogeneous viscoelastic model

Investigation was carried out into the problem of relaxation of a laterally heterogeneous viscoelastic Earth following an impulsive moment release event. The formal solution utilizes a semi-analytic solution for post-seismic deformation on a laterally homogeneous Earth constructed from viscoelastic normal modes, followed by application of mode coupling theory to derive the response on the aspherical Earth. The solution is constructed in the Laplace transform domain using the correspondence principle and is valid for any linear constitutive relationship between stress and strain. The specific implementation described in this paper is a semi-analytic discretization method which assumes isotropic elastic structure and a Maxwell constitutive relation. It accounts for viscoelastic-gravitational coupling under lateral variations in elastic parameters and viscosity. For a given viscoelastic structure and minimum wavelength scale, the computational effort involved with the numerical algorithm is proportional to the volume of the laterally heterogeneous region. Examples are presented of the calculation of post-seismic relaxation with a shallow, laterally heterogeneous volume following synthetic impulsive seismic events, and they illustrate the potentially large effect of regional 3-D heterogeneities on regional deformation patterns.

Geophysical Journal International↗
USGS2017

Water-quality sampling plan for evaluating the distribution of bigheaded carps in the Illinois Waterway

The two nonnative invasive bigheaded carp species (bighead carp Hypophthalmichthys nobilis and silver carp H. molitrix ) that were accidentally released in the 1970s have spread widely into the rivers and waterways of the Mississippi River Basin. First detected in the lower reaches of the Illinois Waterway (IWW, the combined Illinois River-Des Plaines River-Chicago Area Waterway System) in the 1990s, bighead and silver carps moved quickly upstream, approaching the Chicago Area Waterway System. The potential of substantial negative ecological and economic impact to the Great Lakes from the presence of these species is a concern. However, since 2006, the population front of bigheaded carps has remained in the vicinity of Joliet, Illinois, near river mile 278. This reach of the IWW is characterized by stark changes in habitat, water quality, and food resources as the waterway transitions from a primarily agricultural landscape to a metropolitan and industrial canal system. This report describes a 2015 plan for sampling the IWW to establish water-quality conditions that might be contributing to the apparent stalling of the population front of bigheaded carps in this reach. A detailed description of the study plan, Lagrangian-style sampling approach, selected analytes, sampling methods and protocols are provided. Hydrographs from streamflow-gaging stations show IWW conditions during the 2015 sampling runs.

Illinois↗
USGS1991

Reconnaissance geochemical survey of the Farah Garan-Kutam mineral belt, Kingdom of Saudi Arabia

Wadi-sediment samples were collected from 450 sites in a 580-km 2 area (sample density 1.5 per km 2 ) as part of an exploration program designed to assess the mineral potential of the Farah Garan - Kutam mineral belt and to evaluate mineralization at the Farah Garan ancient working (DGMR Project 3.03.10). Demagnetized panned-concentrate and sieved minus-80-mesh fractions were prepared from each bulk sample of approximately 5 kg. The fractions were analyzed for silver, arsenic, copper, lead, and zinc by atomic-absorption methods and for gold by an atomic-absorption graphite-furnace method. The analytical results for the panned-concentrate samples delineate 21 anomalies, and the results for the minus-80-mesh samples delineate 24. Of the latter, 14 are coincident with panned-concentrate anomaly areas, whereas 10 are uniquely defined. The analytical results of the panned-concentrate samples uniquely define two areas. Overall, the panned-concentrate samples yielded threshold values higher than the threshold values for the minus-80-mesh samples (for gold, 10 times higher), and delineate anomalous areas larger than those for the minus-80-mesh samples. This observation is consistent with the results of similar surveys elsewhere in the Arabian Shield, which indicate that panned-concentrate samples more effectively outline geochemical anomalies than sieved fine-grained samples. In the present survey, geochemical anomalies locate all the sites of mineralization known from previous work. The survey is therefore technically a success. However, a large number of these anomalies probably result from contamination of the wadi systems by metal dispersed from ancient mine workings, and this particular survey, overall, may be of limited value as a guide to the discovery of hitherto unknown mineralization. Nevertheless, the survey outlines two areas that may mark extensions to known mineralization, and a number of other areas in which no mineralization is known. Based on a consideration of the character of the bedrock geology, the value of each reported analytical result in relation to the respective element thresholds, and the number of anomalous samples that cluster in any given area, four areas are recommended for high-priority follow-up sampling.

Open-File Report↗
USGS2018

Estimating metal concentrations with regression analysis and water-quality surrogates at nine sites on the Animas and San Juan Rivers, Colorado, New Mexico, and Utah

The purpose of this report is to evaluate the use of site-specific regression models to estimate metal concentrations at nine U.S. Geological Survey streamflow-gaging stations on the Animas and San Juan Rivers in Colorado, New Mexico, and Utah. Downstream users could use these regression models to determine if metal concentrations are elevated and pose a risk to water supplies, agriculture, and recreation. Multiple linear-regression models were developed by relating metal concentrations in discrete water-quality samples to continuously monitored streamflow and surrogate parameters (specific conductance, pH, turbidity, and water temperature) collected at the U.S. Geological Survey stations. Models were developed for dissolved and total concentrations of aluminum, arsenic, cadmium, copper, iron, lead, manganese, and zinc using water-quality samples collected from 2005 to 2017 by several Federal, State, Tribal, and local agencies using different collection methods and analytical laboratories. Model performance varied but, in general, models for dissolved metals did not perform as well as those for total metals. Dissolved metals generally were correlated to specific conductance or streamflow and total metals generally were better correlated with turbidity. Explanatory variables in the models reflected hydrologic and geochemical processes within the basin. A larger number of regression models were statistically significant for the most upstream sites, where metal concentrations were elevated by drainage from abandoned mines and mineralized bedrock. Models generally did not perform as well at downstream sites, especially for dissolved metals, which occurred at lower concentrations than at the upstream sites. In the lower reaches of the rivers, the input of more alkaline water from tributaries and groundwater reduced metal solubility and diluted metal concentrations. The number and distribution of samples in the calibration datasets also may have been a factor in model development. At some sites on the San Juan River, calibration datasets were more limited and did not represent the full range of observed hydrologic and water-quality conditions, especially during storm events in summer and fall. Recommendations for model use are given based on estimates of model precision, biases, and adequacy of the calibration datasets in terms of the number of samples and representativeness of the observed range of streamflow and water-quality conditions.

Colorado, New Mexico, Utah↗
USGS2023

Assessing environmental oil spill based on fluorescence images of water samples and deep learning

Measuring oil concentration in the aquatic environment is essential for determining the potential exposure, risk, or injury for oil spill response and natural resource damage assessment. Conventional analytical chemistry methods require samples to be collected in the field, shipped, and processed in the laboratory, which is also rather time-consuming, laborious, and costly. For rapid field response immediately after a spill, there is a need to estimate oil concentration in near real time. To make the oil analysis more portable, fast, and cost effective, we developed a plug-and-play device and a deep learning model to assess oil levels in water using fluorescent images of water samples. We constructed a 3D-printed device to collect fluorescent images of solvent-extracted water samples using an iPhone. We prepared approximately 1,300 samples of oil at different concentrations to train and test the deep learning model. The model comprises a convolutional neural network and a novel module of histogram bottleneck block with an attention mechanism to exploit the spectral features found in low-contrast images. This model predicts the oil concentration in weight per volume based on fluorescence image. We devised a confidence interval estimator by combining gradient boosting and polymodal regressor to provide a confidence assessment of our results. Our model achieved sufficient accuracy to predict oil levels for most environmental applications. We plan to improve the device and iPhone application as a near-real-time tool for oil spill responders to measure oil in water.

Journal of Environmental Informatics↗
USGS2014

Sampling and monitoring for the mine life cycle

Sampling and Monitoring for the Mine Life Cycle provides an overview of sampling for environmental purposes and monitoring of environmentally relevant variables at mining sites. It focuses on environmental sampling and monitoring of surface water, and also considers groundwater, process water streams, rock, soil, and other media including air and biological organisms. The handbook includes an appendix of technical summaries written by subject-matter experts that describe field measurements, collection methods, and analytical techniques and procedures relevant to environmental sampling and monitoring. The sixth of a series of handbooks on technologies for management of metal mine and metallurgical process drainage, this handbook supplements and enhances current literature and provides an awareness of the critical components and complexities involved in environmental sampling and monitoring at the mine site. It differs from most information sources by providing an approach to address all types of mining influenced water and other sampling media throughout the mine life cycle. Sampling and Monitoring for the Mine Life Cycle is organized into a main text and six appendices that are an integral part of the handbook. Sidebars and illustrations are included to provide additional detail about important concepts, to present examples and brief case studies, and to suggest resources for further information. Extensive references are included.

Book↗
USGS2016

Determination of pesticides and pesticide degradates in filtered water by direct aqueous-injection liquid chromatography-tandem mass spectrometry

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for determination of 229 pesticides compounds (113 pesticides and 116 pesticide degradates) in filtered water samples from stream and groundwater sites. The pesticides represent a broad range of chemical classes and were selected based on criteria such as current-use intensity, probability of occurrence in streams and groundwater, and toxicity to humans or aquatic organisms. More than half of the analytes are pesticide degradates. The method involves direct injection of a 100-microliter (μL) sample onto the LC-MS/MS without any sample preparation other than filtration. Samples are analyzed with two injections, one in electrospray ionization (ESI) positive mode and one in ESI negative mode, using dynamic multiple reaction monitoring (MRM) conditions, with two MRM transitions for each analyte. The LC-MS/MS instrument parameters were optimized for highest sensitivity for the most analytes. This report describes the analytical method and presents characteristics of the method validation including bias and variability, detection levels, and holding-time studies. Mean recoveries of most analytes (223 of 229) were within data-quality objectives of 100±30 percent at spike concentrations above method detection levels (MDLs) in all four matrices. The calculated MDLs ranged from 1 to 103 nanograms per liter (ng/L) for 182 analytes analyzed in the ESI positive mode, and from 2 to 106 ng/L for 42 analytes analyzed in the ESI negative mode. Five analytes had MDLs between 100 and 250 ng/L. The stability studies in reagent water demonstrated that the largest number of the pesticide compounds (227 of 229) were stable after 14 days of storage at 4 degrees Celsius, so these were selected as the practical holding time and storage temperature for routine sample processing. The use of antimicrobial reagent citric acid to adjust the sample pH to about 4 also resulted in lower recoveries of some analytes, so it should not be used as a routine sample preservative.

Techniques and Methods↗
USGS1989

Estimation of the recharge area contributing water to a pumped well in a glacial-drift, river-valley aquifer

The highly permeable, unconfined, glacial-drift aquifers that occupy most New England river valleys constitute the principal source of drinking water for many of the communities that obtain part or all of their public water supply from ground water. Recent events have shown that these aquifers are highly susceptible to contamination that results from a number of sources, such as seepage from wastewater lagoons, leaking petroleum-product storage tanks, and road salting. To protect the quality of water pumped from supply wells in these aquifers, it is necessary to ensure that potentially harmful contaminants do not enter the ground in the area that contributes water to the well. A high degree of protection can be achieved through the application of appropriate land-use controls within the contributing area. However, the contributing areas for most supply wells are not known. This report describes the factors that affect the size and shape of contributing areas to public supply wells and evaluates several methods that may be used to delineate contributing areas of wells in glacial-drift, river-valley aquifers. Analytical, two-dimensional numerical, and three-dimensional numerical models were used to delineate contributing areas. These methods of analysis were compared by applying them to a hypothetical aquifer having the dimensions and geometry of a typical glacial-drift, river-valley aquifer. In the model analyses, factors that control the size and shape of a contributing area were varied over ranges of values common to glacial-drift aquifers in New England. The controlling factors include the rate of well discharge, rate of recharge to the aquifer from precipitation and from adjacent till and bedrock uplands, distance of a pumping well from a stream or other potential source of induced recharge, degree of hydraulic connection of the aquifer with a stream, horizontal hydraulic conductivity of the aquifer, ratio of horizontal to vertical hydraulic conductivity, and degree of well penetration. Analytical methods proved easiest to apply but gave results that are considered to be less accurate than those obtainable by means of numerical-model analysis. Numerical models have the capability to more closely reflect the variable geohydrologic conditions typical of glacial-drift valley aquifers. For average conditions in the hypothetical aquifer, the analytical method predicts a contributing area limited to the well side of the river because a constant-head boundary simulated by image wells is used in the analytical model. For typical glacial-drift, river-valley aquifers, this simulation is unrealistic because drawdowns, caused by a pumping well, and the contributing area of the well can extend beneath and beyond a river or stream. A wide range of hydrologic conditions was simulated by using the two-dimensional numerical model. The resulting contributing area for a well pumped at 1.0 million gallons per day--a common pumping rate--ranged from about 0.9 to 1.8 square miles. Model analyses also show that the contributing area of pumped wells may be expected to extend to the opposite side of the river and to include significant areas of till uplands adjacent to the aquifer on both sides of the valley. Simulations done with the three-dimensional model allow a full three-dimensional delineation of the zone of contribution for a pumped well. For the relatively thin (100 feet or less) unconfined aquifers considered in this analysis, the three-dimensional model showed that the zone of contribution extended throughout the entire saturated thickness of aquifer; therefore, the two-dimensional simulations were considered adequate for delineating contributing areas in this particular hydrologic setting. For thicker aquifers, especially those having partially penetrating wells, three-dimensional models are preferable. Values for several of the factors that affect the size and shape of contributing recharge areas cannot be det

Water Supply Paper↗
USGS1988

Methods for delineating flood-prone areas in the Great Basin of Nevada and adjacent states

The Great Basin is a region of about 210,000 square miles having no surface drainage to the ocean; it includes most of Nevada and parts of Utah, California, Oregon, Idaho, and Wyoming. The area is characterized by many parallel mountain ranges and valleys trending north-south. Stream channels usually are well defined and steep within the mountains, but on reaching the alluvial fan at the canyon mouth, they may diverge into numerous distributary channels, be discontinuous near the apex of the fan, or be deeply entrenched in the alluvial deposits. Larger rivers normally have well-defined channels to or across the valley floors, but all terminate at lakes or playas. Major floods occur in most parts of the Great Basin and result from snowmelt, frontal-storm rainfall, and localized convective rainfall. Snowmelt floods typically occur during April-June. Floods resulting from frontal rain and frontal rain on snow generally occur during November-March. Floods resulting from convective-type rainfall during localized thunderstorms occur most commonly during the summer months. Methods for delineating flood-prone areas are grouped into five general categories: Detailed, historical, analytical, physiographic, and reconnaissance. The detailed and historical methods are comprehensive methods; the analytical and physiographic are intermediate; and the reconnaissance method is only approximate. Other than the reconnaissance method, each method requires determination of a T-year discharge (the peak rate of flow during a flood with long-term average recurrence interval of T years) and T-year profile and the development of a flood-boundary map. The procedure is different, however, for each method. Appraisal of the applicability of each method included consideration of its technical soundness, limitations and uncertainties, ease of use, and costs in time and money. Of the five methods, the detailed method is probably the most accurate, though most expensive. It is applicable to hydraulic and topographic conditions found in many parts of the Great Basin. The historical method is also applicable over a wide range of conditions and is less expensive than the detailed method. However, it requires more historical flood data than are usually available, and experience and judgement are needed to obtain meaningful results. The analytical method is also less expensive than the detailed method and can be used over a wide range of conditions in which the T-year discharge can be determined directly. Experience, good judgement, and thorough knowledge of hydraulic principles are required to obtain adequate results, and the method has limited application in other than rigid-channel situations. The physiographic method is applicable to rigid-boundary channels and is less accurate than the detailed method. The reconnaissance method is relatively imprecise, but it may be the most rational method to use on alluvial fans or valley floors with discontinuous channels. In general, a comprehensive method is most suitable for use with rigid-bank streams in urban areas; only an approximate method seems justified in undeveloped areas.

Water Supply Paper↗
USGS2011

The Alaska Geochemical Database: v. 1.0 - Geologic Materials

What is the AGDB?: The Alaska Geochemical Database (AGDB) is a new, comprehensive compilation of geologic, spatial, descriptive, mineralogical, and analytical geochemical data for samples collected in Alaska and surrounding waters by the U.S. Geological Survey (USGS) from 1962 to 2009. Data for geologic materials (rocks, minerals and mineral separates, soils, lake sediments, bulk stream sediments, and a variety of heavy-mineral concentrates) will be released as a two-sided DVD (USGS Digital Data Series DS 637 v. 1.0) in October of 2011. Future data releases will include water, organic and leachate samples. The AGDB contains all Alaskan data from USGS legacy databases (for example, the RASS and PLUTO systems), and all results produced by USGS in-house and contract chemistry laboratories through December 2009. The database includes geochemical data resulting from the reanalysis of archived materials, such as those from the Alaska Mineral Resource Assessment (AMRAP) and National Uranium Resource Evaluation (NURE) programs, for additional elements and by newer methods. Reanalyses include samples collected statewide as part of the National Geochemical Survey, and samples from a project across the Alaska Range (data released in 2010). The AGDB also contains data for geologic materials from Alaska submitted by USGS researchers to non-USGS and non-contract labs, and a variety of other Alaskan geologic materials samples. Quality Control: Data in the AGDB have undergone extensive quality control screening including searching field notes and maps for accurate location information, verifying media and sample type, linking analytical data to geologic parameters recorded by the submitter, and documenting sample preparation and analytical methods. Data Files The AGDB v. 1.0 two-sided DVD includes: * a 4.3 GB Microsoft Access® 2007 relational database (as two linked .mdb files); * the same database in Microsoft Access® 2003; * Microsoft Excel® spreadsheet tables (.xls files) and ASCII text files that display the results of common queries to the database (for example, Ag-Cr values for concentrate samples; rock samples by quadrangle); * references for analytical methods; * references to published data; and * metadata in three file formats. Data Availability: * The Alaska Geochemical Database will be available in a searchable, spatially referenced, online format at http://mrdata.usgs.gov/; estimated availability early 2012. * A 2012 update (AGDB v. 2.0) will include water, organic, leachate, and miscellaneous sample media. For More Information: On sample media or analytical methods: http://minerals.cr.usgs.gov/projects/analytical_chem/references.html Text prepared by Jeanine M. Schmidt and Matt Granitto Figure prepared by Nora Shew; Layout by Jeanine Schmidt Artwork on page 1 by Daniel Granitto (used by permission) The USGS Mineral Resources Program is the sole Federal provider of research and information on nonfuel mineral resources.

Fact Sheet↗
USGS1971

Interstitial water studies on small core samples, deep sea drilling Project, leg 7

The sediments cored on Leg 7 are predominantly deep sea biogenic oozes and chalks; only rarely were significant quantities of pelagic clays and volcanic detritus encountered. The biogenic sections include both siliceous and calcareous deposits. At three sites the drilling terminated in basalt, one of which (Site 62) is interpreted as being intrusive on the basis of intense alteration of the overlying sediment. With the exception of Ca++ and Sr , compositional changes in the pore waters are characteristically small relative to those reported previously for rapidly deposited, non-biogenic sediments. Ca++ and Sr + , however, exhibit concentrations of up to three times and ten times, respectively, those found in sea water. In several instances, constant concentration gradients as a function of depth have been found. The sampling, storage and analytical procedures employed have been briefly described in an earlier report (Sayles et al, 1970) and are detailed in a manuscript in preparation (Manheim and Chan). Sodium has been calculated as the difference between the summation of the anions and the summation of the major cations exclusive of sodium; to date, this method has proven more accurate than direct analytical methods. Agreement between the two types of silica determination used (emission spectrometric and colorimetric) is poor; the values obtained by emission spectrometry are characteristically higher. The colorimetric technique measures only "reactive" silica (monomeric and possibly dimeric) while the emission spectrometric technique will determine all of the silica in solution and in suspension. The silica content of most of the solutions is high (60 ppm) and polymerization is likely. We are currently investigating this discrepancy. The pH and water content data reported were obtained aboard the Glomar Challenger immediately after sampling

Initial reports of the Deep Sea Drilling Project↗