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Saturday, June 01, 2013

Direct estimation of diffuse gaseous emissions from coal fires: current methods and future directions

Outside Publication: International Journal of Coal Geology
Coal fires occur in nature spontaneously, contribute to increases in greenhouse gases, and emit atmospheric toxicants. Increasing interest in quantifying coal fire emissions has resulted in the adaptation and development of specialized approaches and adoption of numerical modeling techniques. Overview of these methods for direct estimation of diffuse gas emissions from coal fires is presented in this paper.

Tuesday, November 13, 2012

Mercury and Halogens in Coal

Their Role in Determining Mercury Emissions From Coal Combustion

USGS Publication: Fact Sheet 2012–3122
The USGS domestic and international coal databases and research on trace elements in coal contain much information that is relevant to understanding how Hg in coal occurs and why some coals contain more Hg than others.

Tuesday, May 01, 2012

Minor element distribution in iron disulfides in coal

A geochemical review

Outside Publication: International Journal of Coal Geology
Electron beam microanalysis of coal samples in U.S. Geological Survey labs confirms that arsenic is the most abundant minor constituent in iron disulfides in coal and that selenium, nickel, and other minor constituents are present less commonly and at lower concentrations than those for arsenic.

Tuesday, March 06, 2012

Gas emissions, minerals, and tars associated with three coal fires, Powder River Basin, USA

Outside Publication: Science of The Total Environment
Ground-based surveys of three coal fires and airborne surveys of two of the fires were conducted near Sheridan, Wyoming. The fires occur in natural outcrops and in abandoned mines, all containing Paleocene-age subbituminous coals.

Sunday, December 04, 2011

Geochemical Database of Feed Coal and Coal Combustion Products

From Five Power Plants in the United States

USGS Publication: Data Series 635
The principal mission of the U.S. Geological Survey (USGS) Energy Resources Program (ERP) is to (1) understand the processes critical to the formation, accumulation, occurrence, and alteration of geologically based energy resources; (2) conduct scientifically robust assessments of those resources; and (3) study the impacts of energy resource occurrence and (or) their production and use on both the environment and human health.

Tuesday, October 25, 2011

Quantifying greenhouse gas emissions from coal fires using airborne and ground-based methods

Outside Publication: International Journal of Coal Geology
This study demonstrates the ability to estimate CO2 and CH4emissions for the Welch Ranch coal fire, Powder River Basin, Wyoming, USA, using two independent methods:  heat flux calculated from aerial thermal infrared imaging and direct, ground-based measurements. Both approaches offer the potential for conducting inventories of coal fires to assess their gas emissions and to evaluate and prioritize fires for mitigation.

Tuesday, September 13, 2011

Quality Assurance and Quality Control of Geochemical Data

A Primer for the Research Scientist

USGS Publication: Open-File Report 2011–1187
Geochemistry is a constantly expanding science. More and more, scientists are employing geochemical tools to help answer questions about the Earth and earth system processes. Scientists may assume that the responsibility of examining and assessing the quality of the geochemical data they generate is not theirs but rather that of the analytical laboratories to which their samples have been submitted.

Monday, June 20, 2011

Assessing Effects of Energy Development in Colorado and New Mexico

USGS Publication: Fact Sheet 2011–3053
Increased demand for energy is driving rapid development of oil and gas, uranium, geothermal, wind, and solar sources of energy throughout the Western United States. By collaborating with decisonmakers to identify the most pressing information needs, an interdisciplinary team of USGS scientists is developing a multistep analytical process, or framework, for evaluating the cumulative effects and tradeoffs of energy development. The framework for analysis of the various energy types, spatial information, and analytical tools will be synthesized for end users in the form of an online Interactive Energy Atlas for Colorado and New Mexico.

Monday, September 27, 2010

Decision Analysis Framing Study

In-Valley Drainage Management Strategies for the Western San Joaquin Valley, California

USGS Publication: Open-File Report 2009-1121
Constraints on drainage management in the western San Joaquin Valley and implications of proposed approaches to management were recently evaluated by the U.S. Geological Survey (USGS).



Environmental Geochemistry assesses the impacts of energy resources on the environment using a primarily geochemical/geologic approach. Energy resources contain substances that, when mobilized into air, or natural waters (surface and ground water), deposited/adsorbed on soils or sediments, or incorporated into foodstuffs, pose a potential environmental and human health risk. The project examines environmental impacts of toxic substances mobilized from: (1) energy resources in the geologic environment, (2) the extraction, transport, storage, and utilization of energy resources, and (3) the disposal of energy waste products.

Bill Orem
Project Chief

Mercury (Hg) is a toxic pollutant with a complex biogeochemical cycle allowing it to be transferred between different ecosystem reservoirs and occur in different chemical forms that control its behavior and toxicity. In its elemental form, gaseous Hg has a long residence time in the atmosphere, up to a year, allowing it to be transported long distances from emission sources. Mercury can be emitted from natural sources such as volcanoes, or from anthropogenic sources, such as coal-fired power plants. In addition, Hg on the Earth’s surface from all sources can be re-emitted from land and sea back to the atmosphere, and then re-deposited. Mercury in the atmosphere is present in such low concentrations that it is not considered harmful. However, once Hg enters the aquatic environment, it can undergo a series of biochemical transformations that convert a portion of the Hg originally present to methylmercury, a highly toxic organic form that accumulates in fish and birds. In the U.S., consumption of fish with high levels of methylmercury is the most common Hg exposure pathway for people, leading to fish consumption advisories in every state (Fig. 1). Researchers in the USGS Eastern Energy Resources Science Center and their colleagues are actively involved in studying the behavior and occurrence of mercury in the environment, and especially, mercury sources and control from energy use (Kolker et al., 2012).U.S. water bodies for which the Environmental Protection Agency has issued mercury fish consumption advisories in 2010Figure 1. U.S. water bodies for which the Environmental Protection Agency has issued mercury fish consumption advisories in 2010.

Allan Kolker
Project Chief

Selenium is a naturally occurring element and an important micronutrient essential for all living organisms. Selenium is also used in many commercial applications including glass decolorizing, metallurgical additives, machining of ferrous and nonferrous alloys, pigments, copier photoreceptors, and in semiconductor and photocell industries.

Although selenium is essential, large concentrations can be toxic, particularly to aquatic wildlife. Human activities such as coal mining, industrial processing, agricultural runoff and leaching of natural soluble selenium can concentrate selenium in excess of the regulatory limits of 5 micrograms per liter (µg/L) and affect wetland habits. The USGS Energy Resources Program researches the geologic location, extent and distribution, and environmental affects on human health and the landscape and provides this information to decision-makers.

Frequently Asked Questions Pertaining to Selenium

Decision Analysis

Frank Dulong
Lead Scientist

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​​Mercury in Coal
Mercury in Coal

Mercury in Coal

Mercury is a potent neurotoxin that impacts ecosystems and ultimately, human health. Under the U.S. EPA Mercury and Air Toxics Standards (MATS), emissions limits for mercury and associated constituents from U.S. coal-fired utilities are being introduced (EPA, 2011a). To assist stakeholders in the U.S. and throughout the world the USGS, provides detailed information on the occurrence and distribution of Hg and other trace elements in... [+]

coal. Combustion-sourced elemental mercury is recognized as global problem due to its long residence time in the atmosphere and resulting global transport. The USGS has unique capabilities to quantify the origin and distribution of mercury in coal, its capture by power plant air pollution controls, or emission and re-distribution of Hg in the environment. These capabilities allow the USGS to help engineers and regulators find workable approaches to mercury reduction

USGS and EPA Coal Databases

While USGS results were not used in developing the U.S. EPA MATS standards, the USGS, through its U.S. and international coal databases and research on trace elements in coal, has much information that is relevant to understanding how Hg in coal occurs and why some coals have more Hg than others. Since the 1980s, the USGS has compiled data on the quality and chemical composition of U.S. coals using samples that represent the entire thickness of a coal bed in the ground. This database, known as COALQUAL, contains data for more than 7,000 U.S. coal samples. Using COALQUAL, a mean mercury concentration of 0.17 parts per million (ppm) was determined for in-ground coal for the entire U.S. (Tewalt et al., 2001). In 1999 and again in 2010, the U.S. EPA compiled data for coal shipments delivered to U.S. power stations. The 2010 data were used in developing the MATS standards (EPA, 2011b, 2011c). These results give a mean Hg concentration of about 0.12 ppm, much less than USGS results for coal in the ground (Fig. 2).

The difference between the USGS and U.S. EPA results is explained by the fact that some coals, especially those high in sulfur, undergo preparation (cleaning) prior to delivery. As one of the benefits of coal cleaning, Hg associated with mineral matter is reduced in many cases and this is reflected in lower average Hg values for the U.S.EPA databases when compared to USGS results. In addition, COALQUAL contains a greater proportion of samples from the U.S. Appalachian Basin which in general, have higher mercury contents than low-sulfur western coals from Powder River Basin (PRB) of Wyoming and Montana. Use of PRB coals has increased markedly in the last two decades, and this trend is reflected in the U.S. EPA databases for delivered coal when compared to values for in-ground coal determined from COALQUAL. Nonetheless, COALQUAL is very useful in showing how U.S. coals differ by location and rank, and in comparing U.S. coal with international samples.

In addition to the USGS COALQUAL database for domestic coal samples, the USGS maintains a small international database known as the World Coal Quality Inventory (WoCQI) which contains 1,580 samples of coal from 57 countries (Tewalt et al., 2010). One of the largest groups of samples in the WoCQI database is for China (328 samples). Excluding 23 samples of cleaned coal, the remaining 305 samples of in-ground Chinese coal, representing 25 provinces and autonomous regions, give a mean mercury content of 0.16 ppm Hg, similar to the average for in-ground U.S. coal in COALQUAL and identical to that determined for China by Dai et al. (2012), using a larger group of 1,666 samples.

Plots of the mercury distribution of U.S. coal

Figure 2. Plots of the mercury distribution of U.S. coal compiled in USGS COALQUAL database and U.S. EPA databases from 1999, and 2010 data used to inform the EPA MATS standards (Kolker et al., 2012).

Mercury Mode of Occurrence in Coal

USGS laser ablation
Photo: USGS laser ablation (foreground)
ICP-MS (background) laboratory in Denver
used for micro-scale mercury analysis.
Photo by Allan Kolker, USGS.

USGS research on U.S. and international coal samples provides information on the amount and forms of mercury and other elements present. USGS studies using various approaches show that pyrite is the primary host of mercury in many bituminous coals, whereas the proportion of mercury present in organic parts of coal is generally greater in low-rank (lignite and sub-bituminous) coal (Kolker et al., 2006; Fig. 3). Many Eastern U.S. bituminous coals are cleaned prior to use in utility power stations, to reduce sulfur emissions. This coal preparation reduces sulfur content, primarily by removing pyrite from coal. In doing so, a portion of the mercury present may also be removed, a co-benefit of sulfur reduction. With introduction of more stringent Hg standards under MATS, various engineering approaches, including addition of flue gas desulphurization (FGD) scrubbers will likely be required. This will also allow higher sulfur coals to be used without cleaning, by capturing sulfur emissions. By understanding the mode of occurrence of mercury in coal, and the concentration of constituents that affect capture of mercury, such as chlorine, the USGS provides information needed to help predict and control mercury emissions.

Plot of mercury in pyrite of a South African coal determined by laser ablation ICP-MS in USGS labs
Figure 3. Plot of mercury in pyrite of a South African coal determined by laser ablation ICP-MS in USGS labs (inset). Mean concentration for more than 250 pyrite analyses is approximately 10 times the mercury content of the whole coal (UNEP, 2014). Data represent individual laser analysis points that are 20 (blue) or 25 (red) micrometers in diameter.


Dai, S., Ren, D., Chou, C.-L., Finkelman, R.B., Seredin, V.V., and Zhou, Y., 2012, Geochemistry of trace elements in Chinese coals: A review of abundances, genetic types, and impacts on human health and industrial utilization: International Journal of Coal Geology, v. 94, p. 3-21.

Kolker, A., Senior, C. L., and Quick, J. C., 2006, Mercury in coal and the impact of coal quality on mercury emissions from combustion systems: Applied Geochemistry, v. 21, p. 1821-1836.

Kolker, A., Quick, J.C., Senior, C.L., and Belkin, H.E., 2012, Mercury and halogens in coal- Their role in determining mercury emissions from coal combustion: U.S. Geological Survey Fact Sheet 2012-3122, 6 p.

Tewalt, S.J., Bragg, L.J., and Finkelman, R.B., 2001, Mercury in U.S. coal- Abundance, distribution, and modes of occurrence: U.S. Geological Survey Fact Sheet FS-095-01, 4 p.

Tewalt , S. J., Belkin, H.E., SanFilipo, J.R., Merrill, M.D., Palmer, C.A., Warwick, P.D., Karlsen, A.W., Finkelman, R.B., and Park, A.J., 2010, Chemical analyses in the world coal quality inventory, vers. 1: U.S. Geological Survey Open File Report 2010-1196, 4 p. and data files.

UNEP, 2014, Collaborative studies for mercury characterization in coal and coal combustion products, Republic of South Africa, United Nations Environment Programme Project Report prepared by U.S. Geological Survey (USGS), Reston, Virginia, January, 2014, in press.

U.S. EPA, 2011a, Mercury and Air Toxics Standards (MATS):

U.S. EPA, 2011b, Air Toxics Standards for Utilities – MATS ICR Data (EGU_ICR_PartI_and_PartII): Online,, ACCESS data file.

U.S. EPA 2011c, Air Toxics Standards for Utilities – MATS ICR Data (EGU ICR Part III): Online,, ACCESS data file.

Source Characterization and Identification of Natural and Anthropogenic Harmful Materials
Source Characterization
and Identification

Source Characterization and Identification of Natural and Anthropogenic Harmful Materials

Energy resources like coal, oil and natural gas are the pillars of our modern industrial society and they are the major catalyst for the fast paced technological advancement. However, their exploitation has side effects whose magnitude has triggered widespread concerns in the recent years, as the public has become more aware of the concept of global warming or the increasing incidence... [+]

of diseases like cancer or asthma. At the forefront of geomedical research, the USGS has the role to provide the public and the policymakers with the scientific information needed to account for the environmental and human health consequences of energy resource extraction, processing, transportation and use. The USGS is addressing these issues in an interdisciplinary context, through a dedicated project entitled “Impacts of Energy Resources on Human Health and Environmental Quality”. Several research topics include: Balkan Endemic Nephropathy (BEN), “panendemic nephropathy” (i.e., diseases similar to BEN but outside the Balkans), environmental contamination related to mountain top mining (MTM) and coal slurry in the Appalachian Basin and the release of toxic substances in energy combustion products.

Mountain top mining (MTM) in the Appalachian Basin
Figure 1. Mountain top mining (MTM) in the
Appalachian Basin has adverse consequences
on the environment and human and
ecosystems health. USGS in collaboration with
West Virginia University in Morgantown is
addressing issues as water, air and soil
pollution caused by MTM. Enlarge Image

Coal, in native or processed form, is a major source of organic pollutants
Figure 2. Coal, in native or processed form, is
a major source of organic pollutants that can
leach into groundwater or streams and affects
humans or aquatic organisms. This photo
shows a seam of Pliocene lignite from
Romania; such low rank coal deposits are
widespread in the Balkan endemic nephropathy
(BEN) areas and are supposed to contain
nephrotoxic and carcinogenic organic
substances that contaminate drinking
groundwater and are causing the fatal kidney
disease and urinary tract cancers.
Enlarge Image


Orem W., Tatu C., Pavlovic N., Bunnell J., Kolker A., Engle M. and Ben Stout (2009) Health Effects of Energy Resources. U.S. Geological Survey Fact Sheet 2009-3096.

Kolker A., Engle, M., Stracher G., Hower J., Prakash A., Radke L., ter Schure A., Heffern E (2009) Emissions from coal fires and their impact on the environment: U.S. Geological Survey Fact Sheet 2009-3084.

Orem W.H., Bunnell J.E. Tatu C.A., Pavlovic N., and (2009) Toxicological pathways of relevance to medical geology. In: Encyclopedia of Environmemntal Health (Nriagu J., editor), Elsevier Science 2011.

Contact: William H. Orem

Movement and Alteration of Disease-causing Agents
Movement and Alteration of
Disease-causing Agents

Movement and Alteration Predictions of Chemical, Infectious, and other Disease-causing Agents over Time and Space

Air can be a significant source of all sorts of human health hazards and compared to water and soil, transport of noxious chemicals and particulates or pathogenic microorganisms occurs much faster and can affect populational groups on a larger scale. USGS has been involved in several projects exploring the links between human health and air... [+]

quality alterations due to fossil fuel extraction/mining and combustion.

The presence in air of fine particulate matter 2.5 micrometers in size, called PM2.5, and originating from coal combustion and other sources, is a serious health concern. This material is small enough to be readily lodged in small interstices (alveoli) in the lungs. The U.S. Environmental Protection Agency (USEPA) air-quality regulatory standards are based on limits in the amount of PM2.5, while the USGS can provide more detailed knowledge on the chemistry, mineralogy, surface characteristics and potential toxicity of such particles.

A multi-agency study in the Navajo Nation of New Mexico has focused on the extent of human exposure to contaminants in particulate matter derived from domestic coal combustion and links to respiratory disease. The study was based on both epidemiological data examining the incidence of respiratory diseases as well as on field studies measuring indoor and outdoor air quality, including PM2.5. Air sampling in the Navajo Nation has shown that in winter, when coal stoves are in use, some homes exceed the USEPA 24-hour ambient (outdoor) PM2.5 standard. Analysis of PM2.5 samples from Navajo homes burning coal shows an abundance of organic compounds indicative of a coal source.


Orem W., Tatu C., Pavlovic N., Bunnell J., Kolker A., Engle M. and Ben Stout (2009) Health Effects of Energy Resources. U.S. Geological Survey Fact Sheet 2009-3096.

Kolker A., Engle, M., Stracher G., Hower J., Prakash A., Radke L., ter Schure A., Heffern E (2009) Emissions from coal fires and their impact on the environment: U.S. Geological Survey Fact Sheet 2009-3084.

Bunnell J. E., Garcia L.V, Furst J.M., Lerch H., Olea R.A., Suitt S.E., and Kolker A. (2010) Navajo coal combustion and respiratory health near shiprock, new Mexico. J Environ Public Health. 2010:260525.

Contact: William H. Orem


USGS CoreCast:

Mercury Contamination in Fish
USGS Podcast (Episode 102)

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Coal and Human Health
USGS Podcast (Episode 103)

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Page Last Modified: Tuesday, October 28, 2014


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