Search USGS⌕ Search

SEARCH · Search USGS

Results for “Chemical Physics”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,099 records · Page 61Linked to original sources
USGS1988

Water-quality data for the Boise River, Boise to Star, Idaho, January to March 1988

Physical and chemical data were collected at six sites and biological data were collected at five sites on the Boise River between Veterans Memorial Parkway in Boise and Star, Idaho, from January to March 1988. Data were collected to determine the effect of sewage effluent from two Boise wastewater treatment facilities on the water and biological quality of the Boise River. Similar data were collected from October to December 1987. Results of all data analyses will be discussed in an interpretive report.

Idaho↗
USGS1988

Models, data available, and data requirements for estimating the effects of injecting saltwater into disposal wells in the greater Altamont-Bluebell oil and gas field, northern Uinta Basin, Utah

Permits for disposing of salty oil-production water have been issued for 19 wells in the Greater Altamont-Bluebell field. During 1986 more than 500 million gallons of production water were injected into the Duchesne River, Uinta, and Green River Formations through 18 of these wells. The physical and chemical effects of injecting this water into aquifers containing potable water are poorly understood. Interfingering and the structural configuration of these formations add complexity to the description of the geometry and hydrogeology of the ground-water system. A preliminary assessment of the problem indicates that numerical modeling may offer a method of determining the effects of injection. Modeling possibilities include variable-density, three-dimensional flow, sectionaltransport, and areal-transport models. Data needed to develop these models can be derived from a synthesis of geologic, hydrologic, and hydrochemical data already available in the files of State and Federal agencies, oil companies, and private companies. Results from each modeling phase would contribute information for implementing the following phase. The result will be a better understanding of how water moves naturally through the groundwater system, the extent of alterations of both vertical and horizontal flow near the disposal wells, and an overall concept of the effects of deep injection on near-surface aquifers.

Utah↗
USGS1990

Hydrogeochemical data from an acidic deposition study at McDonalds Branch basin in the New Jersey Pinelands, 1983-86

Data from a 1983-86 acidic-deposition study at McDonalds Branch basin, a small (2.35-sq-mi) forested watershed in Lebanon State Forest, New Jersey include mineralogy of soil and depositional clays; physical and chemical analyses of soils; hydrologic measurements (precipitation and throughfall amounts, stream stage and discharge, and water-table altitudes); and water quality data from precipitation, throughfall, soil water, surface water, and groundwater. Site locations, collector designs, and well- construction data also are presented. The pH of bulk precipitation to McDonalds Branch basin over the sampling period (January 1985 to March 1986) ranged from 4.0 to 4.7, with a mean of approximately 4.3. Stream pH ranged from 3.2 to 4.8 and generally increased in a downstream direction. In general sulfate was the dominant anion throughout the basin. Aluminum concentrations commonly were elevated in surface and groundwaters, and were as high as 10,000 micrograms/L at one upstream site on McDonalds Branch. Dissolved organic carbon was an important component of stream waters in some locations and ranged in concentration from 1/1 to 37 mg/L. (USGS)

Open-File Report↗
USGS1991

Sediments, nutrients, and oxygen-demanding substances in the Minnesota River: Selected water-quality data, 1989-90

This report presents selected physical and chemical data collected by the U.S. Geological Survey for the Minnesota River Assessment Project, a four-year interagency study coordinated by the Minnesota Pollution Control Agency. Water samples were collected at 12 sites on the Minnesota River and at the mouths of 10 major tributary streams located from the outlet of Lac qui Parle Reservoir to Henderson, Minnesota. Sampling from August 1989 through September 1990 resulted in collection of 171 stream-water samples. This report includes data on streamflow, total suspended solids, nitrite plus nitrate nitrogen, total phosphorus, biochemical oxygen demand, and chlorophyll a .

Iowa, Minnesota, South Dakota↗
USGS1993

Methods for collecting benthic invertebrate samples as part of the National Water-Quality Assessment Program

Benthic invertebrate communities are evaluated as part of the ecological survey component of the U.S. Geological Survey's National Water-Quality Assessment Program. These biological data are collected along with physical and chemical data to assess water-quality conditions and to develop an understanding of the factors that affect water-quality conditions locally, regionally, and nationally. The objectives of benthic invertebrate community characterizations are to (1) develop for each site a list of tax a within the associated stream reach and (2) determine the structure of benthic invertebrate communities within selected habitats of that reach. A nationally consistent approach is used to achieve these objectives. This approach provides guidance on site, reach, and habitat selection and methods and equipment for qualitative multihabitat sampling and semi-quantitative single habitat sampling. Appropriate quality-assurance and quality-control guidelines are used to maximize the ability to analyze data within and among study units.

Open-File Report↗
USGS1993

Guidelines for the processing and quality assurance of benthic invertebrate samples collected as part of the National Water-Quality Assessment Program

Benthic invertebrate samples are collected as part of the U.S. Geological Survey's National Water-Quality Assessment Program. This is a perennial, multidisciplinary program that integrates biological, physical, and chemical indicators of water quality to evaluate status and trends and to develop an understanding of the factors controlling observed water quality. The Program examines water quality in 60 study units (coupled ground- and surface-water systems) that encompass most of the conterminous United States and parts of Alaska and Hawaii. Study-unit teams collect and process qualitative and semi-quantitative invertebrate samples according to standardized procedures. These samples are processed (elutriated and subsampled) in the field to produce as many as four sample components: large-rare, main-body, elutriate, and split. Each sample component is preserved in 10-percent formalin, and two components, large-rare and main-body, are sent to contract laboratories for further processing. The large-rare component is composed of large invertebrates that are removed from the sample matrix during field processing and placed in one or more containers. The main-body sample component consists of the remaining sample materials (sediment, detritus, and invertebrates) and is subsampled in the field to achieve a volume of 750 milliliters or less. The remaining two sample components, elutriate and split, are used for quality-assurance and quality-control purposes. Contract laboratories are used to identify and quantify invertebrates from the large-rare and main-body sample components according to the procedures and guidelines specified within this document. These guidelines allow the use of subsampling techniques to reduce the volume of sample material processed and to facilitate identifications. These processing procedures and techniques may be modified if the modifications provide equal or greater levels of accuracy and precision. The intent of sample processing is to determine the quantity of each taxon present in the semi-quantitative samples or to list the taxa present in qualitative samples. The processing guidelines provide standardized laboratory forms, sample labels, detailed sample processing flow charts, standardized format for electronic data, quality-assurance procedures and checks, sample tracking standards, and target levels for taxonomic determinations. The contract laboratory (1) is responsible for identifications and quantifications, (2) constructs reference collections, (3) provides data in hard copy and electronic forms, (4) follows specified quality-assurance and quality-control procedures, and (5) returns all processed and unprocessed portions of the samples. The U.S. Geological Survey's Quality Management Group maintains a Biological Quality-Assurance Unit, located at the National Water-Quality Laboratory, Arvada, Colorado, to oversee the use of contract laboratories and ensure the quality of data obtained from these laboratories according to the guidelines established in this document. This unit establishes contract specifications, reviews contractor performance (timeliness, accuracy, and consistency), enters data into the National Water Information System-II data base, maintains in-house reference collections, deposits voucher specimens in outside museums, and interacts with taxonomic experts within and outside the U.S. Geological Survey. This unit also modifies the existing sample processing and quality-assurance guidelines, establishes criteria and testing procedures for qualifying potential contract laboratories, identifies qualified taxonomic experts, and establishes voucher collections.

Open-File Report↗
USGS1994

Hydrologic data collection at Crowders Creek and Steele Creek, York County, South Carolina, 1991-92

Rapid industrial and urban growth is anticipated in the vicinity of Crowders Creek near Clover, S.C., and Steele Creek near Fort Mill, S.C. These subbasins are in the Catawba River Basin in York County, S.C. To obtain baseline information on these basins prior to urbanization, gaging stations 02145642 (Crowders Creek near Clover, S.C.) and 021467801 (Steele Creek near Fort Mill, S.C.) were established to collect streamflow and water-quality data. Continuous stream-stage and streamflow data were collected during the periods of March 23, 1991 to September 30, 1992, and May 29, 1991 to September 30, 1992, for stations 02145642 and 021467801, respectively. Average streamflows for stations 02145642 and 021467801 for the study period were 80.5 cubic feet per second and 28.6 cubic feet per second, respectively. Water-quality data were collected on four separate occasions at each gage site; two samplings during low-flow events and two samplings during high-flow events. Fecal coliform concentrations exceeded minimum standards for freshwater with other physical and chemical constituents meeting South Carolina Department of Health and Environmental Control standards.

South Carolina↗
USGS1995

Water-quality assessment of the Albemarle-Pamlico drainage basin, North Carolina and Virginia environmental setting and water-quality issues

The Albemarle-Pamlico drainage study unit is one of 60 units of the U.S. Geological Survey's National Water-Quality Assessment Program, and includes the large river basins which drain into the Albemarle and Pamlico Sounds-the Chowan, Roanoke, Tar-Pamlico, and Neuse River Basins. The study unit includes about 28,000 square miles and has an interrelated set of environmental characteristics which strongly influence water quality. The chemical and physical nature of these characteristics are the dominant controls on baseline water quality in the study area. About 50 percent of the study area is forested, slightly more than 30 percent is agricultural, about 15 percent is wetlands, and less than 5 percent is developed. Three million people live in the study area, and activities related to agriculture and development have caused increased concentrations of constituents such as nutrients, pesticides, and suspended sediment. About two-thirds of the 36 to 52 inches of precipitation in the area reenters the atmosphere by evapotranspiration. About one-third of the remaining precipitation reaches streams by overland runoff; the remainder recharges the water table aquifer, where much of the water eventually discharges to streams as ground water. Thus, ground-water quality has a substantial influence on surface-water quality, particularly during dry weather. In 1990, about 152,900 tons of elemental nitrogen and 10,500 tons of elemental phosphorus either were applied to crops as fertilizer or fixed by biological processes, and in 1987, about 43,500 tons of nitrogen and 12,200 tons of phosphorus were produced as animal wastes. In addition, about 1,300 tons of selected herbicides and 400 tons of selected insecticides were applied to crops in 1990. Some 249 permitted point sources discharged 410 million gallons per day, containing an annual load of 5,800 tons of nitrogen and 1,800 tons of phosphorus, to the study area in 1990. Data from 1970-79 indicate that mean annual suspended-sediment yields for selected forested, agricultural, and developed urban basins in North Carolina are 50, 250, and 550 tons per square mile, respectively. In order to facilitate comparisons, much of the data were compiled by hydrologic unit. Homogeneous areas, or strata, representing the most prevalent combinations of environmental factors, such as land use, soils, and geology, were defined. Future data collection and analyses will be designed to answer objective-related concerns about the relations between important water-quality conditions and these study-unit strata.

North Carolina, Virginia↗
USGS1995

Sampling design and procedures for fixed surface-water sites in the Georgia-Florida coastal plain study unit, 1993

The implementation of design guidelines for the National Water-Quality Assessment (NAWQA) Program has resulted in the development of new sampling procedures and the modification of existing procedures commonly used in the Water Resources Division of the U.S. Geological Survey. The Georgia-Florida Coastal Plain (GAFL) study unit began the intensive data collection phase of the program in October 1992. This report documents the implementation of the NAWQA guidelines by describing the sampling design and procedures for collecting surface-water samples in the GAFL study unit in 1993. This documentation is provided for agencies that use water-quality data and for future study units that will be entering the intensive phase of data collection. The sampling design is intended to account for large- and small-scale spatial variations, and temporal variations in water quality for the study area. Nine fixed sites were selected in drainage basins of different sizes and different land-use characteristics located in different land-resource provinces. Each of the nine fixed sites was sampled regularly for a combination of six constituent groups composed of physical and chemical constituents: field measurements, major ions and metals, nutrients, organic carbon, pesticides, and suspended sediments. Some sites were also sampled during high-flow conditions and storm events. Discussion of the sampling procedure is divided into three phases: sample collection, sample splitting, and sample processing. A cone splitter was used to split water samples for the analysis of the sampling constituent groups except organic carbon from approximately nine liters of stream water collected at four fixed sites that were sampled intensively. An example of the sample splitting schemes designed to provide the sample volumes required for each sample constituent group is described in detail. Information about onsite sample processing has been organized into a flowchart that describes a pathway for each of the constituent groups.

Florida, Georgia↗
USGS1995

Water-quality conditions of inflow, outflow, and impounded water at Rathbun Reservoir, Iowa, Clinton and Pomona Lakes, Kansas, and Harlan County Reservoir, Nebraska, May through August 1993

During May through August 1993, water-quality samples were collected twice from selected sites in Rathbun Reservoir, Iowa, Clinton and Pomona Lakes, Kansas, and Harlan County Reservoir, Nebraska. Samples were analyzed for selected physical and chemical properties, bacteria, major ions, nutrients, selected metals, total organic carbon, selected herbicides, and chlorophyll-a and -b. During May through August 1993, precipitation at all four reservoirs exceeded mean precipitation at nearby long-term precipitation gages; precipitation ranged from 7.76 inches above the long-term mean at Pomona Lake to 12.62 inches above the long-term mean at Rathbun Reservoir. Reservoir water-surface elevations exceeded flood-pool elevation by 4 feet in Clinton Lake, by 19 feet in Pomona Lake, and by 2 feet in Harlan County Reservoir in July. Thermal stratification of water occurred at one site in Rathbun Reservoir in August, at two sites in Clinton Lake in May, at one site in Pomona Lake in June, and at one site in Harlan County Reservoir in June. Total triazine herbicide concentrations in water samples from all four reservoirs ranged from 0.2 to 19 micrograms per liter and were largest water samples from Rathbun Reservoir in June. Concen- trations of atrazine exceeded the U.S. Environmental Protection Agency's Maximum Contaminant Level of 3.0 micrograms per liter for drinking water in at least one sample each from Rathbun Reservoir, Clinton Lake, and Pomona Lake. Concentrations of cyanazine exceeded the U.S. Environmental Protection Agency's Maximum Contaminant Level of 1.0 microgram per liter in water samples from Rathbun Reservoir.

Open-File Report↗
USGS1996

Water-quality and lake-stage data for Wisconsin lakes, water year 1995

The U.S. Geological Survey (USGS), in cooperation with local and other agencies, collects data at selected lakes throughout Wisconsin. These data, accumulated over many years, provide a data base for developing an improved understanding of the water quality of lakes. To make these data available to interested parties outside the USGS, the data are published annually in this report series. The location of surface water-quality and lake-stage stations in Wisconsin for water year 1995 are shown in figure 1. A water year is the 12-month period from October 1 through September 30. It is designated by the calendar year in which it ends and which includes 9 of the 12 months. Thus the period October 1, 1994 through September 30, 1995, is called "water year 1995." The purpose of this report is to provide information about the physical and chemical characteristics of Wisconsin lakes. Data that have been collected at specific lakes, and information to aid in the interpretation of those data, are included in this report. Data collected includes measurements of lake stage and in-lake water quality. Graphs of Secchi depths, and surface total-phosphorus and chlorophyll-a concentrations versus time are included for lakes with two or more years of data. Descriptive information for each lake includes: location of the lake, drainage area of the lake's watershed, period for which data are available, revisions to previously published records, and pertinent remarks. Additional data, such as streamflow and water quality in tributary and outlet streams of some of the lakes, are published in another volume: "Water Resources Data-Wisconsin, 1995."

Wisconsin↗
USGS1996

MUDMASTER: A Program for Calculating Crystalline Size Distributions and Strain from the Shapes of X-Ray Diffraction Peaks

Particle size may strongly influence the physical and chemical properties of a substance (e.g. its rheology, surface area, cation exchange capacity, solubility, etc.), and its measurement in rocks may yield geological information about ancient environments (sediment provenance, degree of metamorphism, degree of weathering, current directions, distance to shore, etc.). Therefore mineralogists, geologists, chemists, soil scientists, and others who deal with clay-size material would like to have a convenient method for measuring particle size distributions. Nano-size crystals generally are too fine to be measured by light microscopy. Laser scattering methods give only average particle sizes; therefore particle size can not be measured in a particular crystallographic direction. Also, the particles measured by laser techniques may be composed of several different minerals, and may be agglomerations of individual crystals. Measurement by electron and atomic force microscopy is tedious, expensive, and time consuming. It is difficult to measure more than a few hundred particles per sample by these methods. This many measurements, often taking several days of intensive effort, may yield an accurate mean size for a sample, but may be too few to determine an accurate distribution of sizes. Measurement of size distributions by X-ray diffraction (XRD) solves these shortcomings. An X-ray scan of a sample occurs automatically, taking a few minutes to a few hours. The resulting XRD peaks average diffraction effects from billions of individual nano-size crystals. The size that is measured by XRD may be related to the size of the individual crystals of the mineral in the sample, rather than to the size of particles formed from the agglomeration of these crystals. Therefore one can determine the size of a particular mineral in a mixture of minerals, and the sizes in a particular crystallographic direction of that mineral.

Open-File Report↗
USGS1997

Water-quality and lake-stage data for Wisconsin lakes, water year 1996

The U.S. Geological Survey (USGS), in cooperation with local and other agencies, collects data at selected lakes throughout Wisconsin. These data, accumulated over many years, provide a data base for developing an improved understanding of the water quality of lakes. To make these data available to interested parties outside the USGS, the data are published annually in this report series. The location of surface water-quality and lake-stage stations in Wisconsin for water year 1996 are shown in figure 1. A water year is the 12-month period from October 1 through September 30. It is designated by the calendar year in which it ends and which includes 9 of the 12 months. Thus the period October 1, 1995 through September 30, 1996, is called "water year 1996." The purpose of this report is to provide information about the physical and chemical characteristics of Wisconsin lakes. Data that have been collected at specific lakes, and information to aid in the interpretation of those data, are included in this report. Data collected includes measurements of lake stage and in-lake water quality. Graphs of Secchi depths, surface totalphosphorus and chlorophyll-a concentrations versus time are included for lakes with two or more years of data. Graphs of vertical profiles of temperature, dissolved oxygen, pH, and specific conductance are included for sites where these parameters were measured. Descriptive information for each lake includes: location of the lake, drainage area of the lake's watershed, period for which data are available, revisions to previously published records, and pertinent remarks. Additional data, such as streamflow and water quality in tributary and outlet streams of some of the lakes, are published in another volume: "Water Resources Data-Wisconsin, 1996."

Wisconsin↗
USGS1998

Water-quality and lake-stage data for Wisconsin lakes, water year 1997

The U.S. Geological Survey (USGS), in cooperation with local and other agencies, collects data at selected lakes throughout Wisconsin. These data, accumulated over many years, provide a data base for developing an improved understanding of the water quality of lakes. To make these data available to interested parties outside the USGS, the data are published annually in this report series. The location of water-quality and lake-stage stations in Wisconsin for water year 1997 are shown in figure 1. A water year is the 12-month period from October 1 through September 30. It is designated by the calendar year in which it ends. Thus, the period October 1, 1996 through September 30, 1997 is called 'water year 1997'. The purpose of this report is to provide information about the physical and chemical characteristics of Wisconsin lakes. Data that have been collected at specific lakes, and information to aid in the interpretation of those data, are included in this report. Data collected include measurements of lake stage and in-lake water quality. Graphs of Secchi depths, surface total-phosphorus and chlorophyll-a concentrations versus time are usually included for lakes with two or more years of data. Graphs of vertical profiles of temperature, dissolved oxygen, pH, and specific conductance are included for sites where these parameters were measured. Descriptive information for each lake includes: location of the lake, area of the lake's watershed, period for which data are available, revisions to previously published records, and pertinent remarks. Additional data, such as streamflow and water quality in tributary and outlet streams of some of the lakes, are published in another volume: 'Water Resources Data-Wisconsin, 1997'.

Wisconsin↗
USGS1999

Water-quality and lake-stage data for Wisconsin lakes, water year 1998

The U.S. Geological Survey (USGS), in cooperation with local and other agencies, collects data at selected lakes throughout Wisconsin. These data, accumulated over many years, provide a data base for developing an improved understanding of the water quality of lakes. To make these data available to interested parties outside the USGS, the data are published annually in this report series. The location of water-quality and lake-stage stations in Wisconsin for water year 1998 are shown in figure 1. A water year is the 12-month period from October 1 through September 30. It is designated by the calendar year in which it ends. Thus, the period October 1, 1997 through September 30, 1998 is called "water year 1998." The purpose of this report is to provide information about the chemical and physical characteristics of Wisconsin lakes. Data that have been collected at specific lakes, and information to aid in the interpretation of those data, are included in this report. Data collected include measurements of in-lake water quality and lake stage. Time series of Secchi depths, surface total phosphorus and chlorophyll a concentrations collected during non-frozen periods are usually included for lakes with two or more years of data. Graphs of vertical profiles of temperature, dissolved oxygen, pH, and specific conductance are included for sites where these parameters were measured. Descriptive information for each lake includes: location of the lake, area of the lake's watershed, period for which data are available, revisions to previously published records, and pertinent remarks. Additional data, such as streamflow and water quality in tributary and outlet streams of some of the lakes, are published in another volume: "Water Resources Data- Wisconsin, 1998."

Wisconsin↗
USGS1998

Transport, behavior, and fate of volatile organic compounds in streams

Volatile organic compounds (VOCs) are compounds with chemical and physical properties that allow the compounds to move freely between the water and air phases of the environment. VOCs are widespread in the environment because of this mobility. Many VOCs have properties making them suspected or known hazards to the health of humans and aquatic organisms. Consequently, understanding the processes affecting the concentration and distribution VOCs in the environment is necessary. The U.S. Geological Survey selected 55 VOCs for study. This report reviews the characteristics of the various process that could affect the transport, behavior, and fate of these VOCs in streams.

Professional Paper↗
USGS2012

Weathering, landscape equilibrium, and carbon in four watersheds in eastern Puerto Rico: Chapter H in Water quality and landscape processes of four watersheds in eastern Puerto Rico

The U.S. Geological Survey's Water, Energy, and Biogeochemical Budgets (WEBB) program research in eastern Puerto Rico involves a double pair-wise comparison of four montane river basins, two on granitic bedrock and two on fine-grained volcaniclastic bedrock; for each rock type, one is forested and the other is developed. A confounding factor in this comparison is that the developed watersheds are substantially drier than the forested (runoff of 900–1,600 millimeters per year compared with 2,800–3,700 millimeters per year). To reduce the effects of contrasting runoff, the relation between annual runoff and annual constituent yield were used to estimate mean-annual yields at a common, intermediate mean-annual runoff of 1,860 millimeters per year. Upon projection to this intermediate runoff, the ranges of mean-annual yields among all watersheds became more compact or did not substantially change for dissolved bedrock, sodium, silica, chloride, dissolved organic carbon, and calcium. These constituents are the primary indicators of chemical weathering, biological activity on the landscape, and atmospheric inputs; the narrow ranges indicate little preferential influence by either geology or land cover. The projected yields of biologically active constituents (potassium, nitrate, ammonium ion, phosphate), and particulate constituents (suspended bedrock and particulate organic carbon) were considerably greater for developed landscapes compared with forested watersheds, consistent with the known effects of land clearing and human waste inputs. Equilibrium rates of combined chemical and physical weathering were estimated by using a method based on concentrations of silicon and sodium in bedrock, river-borne solids, and river-borne solutes. The observed rates of landscape denudation greatly exceed rates expected for a dynamic equilibrium, except possibly for the forested watershed on volcaniclastic rock. Deforestation and agriculture can explain the accelerated physical erosion in the two developed watersheds. Because there has been no appreciable deforestation, something else, possibly climate or forest-quality change, must explain the accelerated erosion in the forested watersheds on granitic rocks. Particulate organic carbon yields are closely linked to sediment yields. This relation implies that much of the particulate organic carbon transport in the four rivers is being caused by this enhanced erosion aided by landslides and fast carbon recovery. The increase in particulate organic carbon yields over equilibrium is estimated to range from 300 kilomoles per square kilometer per year (6 metric tons carbon per square kilometer per year) to 1,700 kilomoles per square kilometer per year (22 metric tons carbon per square kilometer per year) and is consistent with human-accelerated particulate-organic-carbon erosion and burial observed globally. There is no strong evidence of human perturbation of silicate weathering in the four study watersheds, and differences in dissolved inorganic carbon are consistent with watershed geology. Although dissolved organic carbon is slightly elevated in the developed watersheds, that elevation is not enough to unambiguously demonstrate human causes; more work is needed. Accordingly, the dissolved organic carbon and dissolved inorganic carbon yields of tropical rivers, although large, are of secondary importance in the study of the anthropgenically perturbed carbon cycle.

Professional Paper↗
USGS2017

Niobium and tantalum

Niobium and tantalum are transition metals that are almost always found together in nature because they have very similar physical and chemical properties. Their properties of hardness, conductivity, and resistance to corrosion largely determine their primary uses today. The leading use of niobium (about 75 percent) is in the production of high-strength steel alloys used in pipelines, transportation infrastructure, and structural applications. Electronic capacitors are the leading use of tantalum for high-end applications, including cell phones, computer hard drives, and such implantable medical devices as pacemakers. Niobium and tantalum are considered critical and strategic metals based on the potential risks to their supply (because current production is restricted to only a few countries) and the significant effects that a restriction in supply would have on the defense, energy, high-tech industrial, and medical sectors. The average abundance of niobium and tantalum in bulk continental crust is relatively low—8.0 parts per million (ppm) niobium and 0.7 ppm tantalum. Their chemical characteristics, such as small ionic size and high electronic field strength, significantly reduce the potential for these elements to substitute for more common elements in rock-forming minerals and make niobium and tantalum essentially immobile in most aqueous solutions. Niobium and tantalum do not occur naturally as pure metals but are concentrated in a variety of relatively rare oxide and hydroxide minerals, as well as in a few rare silicate minerals. Niobium is primarily derived from the complex oxide minerals of the pyrochlore group ((Na,Ca,Ce) 2 (Nb,Ti,Ta) 2 (O,OH,F) 7 ), which are found in some alkaline granite-syenite complexes (that is, igneous rocks containing sodium- or potassium-rich minerals and little or no quartz) and carbonatites (that is, igneous rocks that are more than 50 percent composed of primary carbonate minerals, by volume). Tantalum is derived mostly from the mineral tantalite ((Fe,Mn)(Ta,Nb) 2 O 6 ), which is found as an accessory mineral in rare-metal granites and pegmatites that are also enriched in lithium and cesium (termed lithium-cesium-tantalum (LCT)-type pegmatites). Brazil and Canada are the leading nations that produce niobium mineral concentrates, but Brazil is by far the leading producer, accounting for about 90 percent of production, which comes mostly from weathered material derived from carbonatites. Brazil and Canada also have the largest identified niobium resources; additional resources, although they are less well reported, occur in Angola, Australia, China, Greenland, Malawi, Russia, and South Africa. Australia and Brazil have been the leading producers of tantalum mineral concentrates, although recently Ethiopia and Mozambique have also been significant suppliers of tantalum. Artisanal mining of columbite-tantalite (also called coltan) is practiced in many countries, particularly Burundi, the Democratic Republic of the Congo (Congo [Kinshasa]), Nigeria, Rwanda, and Uganda. Brazil has about 40 percent of the identified tantalum resources; other countries and regions with identified tantalum resources include, in decreasing order of resources, Australia, Asia, Russia and the Middle East, Africa, North America, and Europe. Identified niobium and tantalum resources in the United States are small, low grade, and difficult to recover and process, and are thus not commercially recoverable at current prices. Consequently, the United States meets its current and expected future needs for niobium and tantalum through imports of primary mineral concentrates and alloys and through recovery from foreign and domestic alloy scrap that contain the metals. Environmentally, the main issues related to niobium and tantalum mining are land disruptions, the volume of waste materials and their disposal, and the radioactivity of some tailings and waste materials that contain thorium and uranium. Because of the relative biological inertness of niobium and tantalum, human and ecological health concerns are generally minimal under most natural conditions. Demand for both niobium and tantalum is expected to increase as the world economy continues to recover from the downturn that began in 2008. Increased demand for niobium is linked to increased consumption of microalloyed steel, which is used in the manufacture of cars, buildings, ships, and refinery equipment. Demand for these steels will likely increase with continued economic development in such countries as Brazil, China, and India. In addition, increased global demand for cars, cell phones, computers, superconducting magnets, and other high-tech devices will likely spur increased demand for both niobium and tantalum. The estimated global reserves and resources of niobium and tantalum are large and appear more than sufficient to meet global demand for the foreseeable future, possibly the next 500 years. The sale of “conflict coltan” attributed to rebel forces waging a civil war in Congo (Kinshasa) has been of recent concern and has highlighted the need for a transparent and traceable global supply chain that can exclude illegal columbite-tantalite from the conventional market while discerning legitimate artisanal mine production in central Africa.

Professional Paper↗