Environmental physics

Definition:Environmental physics is a multidisciplinary field that investigates the physical principles underlying environmental phenomena and the relationship between the biota (organisms living on the earth) and the nonliving components of the environment. Specifically, environmental physicists attempt to describe environmental processes—such as nutrient or elemental cycling, radiation, and the movement of energy—using the principles of classical physics, including thermodynamics and mechanics. Environmental physics is essential to ongoing efforts to study climate change and is also used widely in energy industry research, meteorology, atmospheric science, hydrology, and the development of green technology.

Basic Principles

Environmental physics grew out of the natural philosophy of the eighteenth and nineteenth centuries, when scientists and philosophers attempted to derive the mathematical relationships underlying environmental phenomena, including weather patterns and tidal movements. Swedish chemist and physicist Svante Arrhenius is one of the fathers of the field, having discovered, in 1896, the physical relationship between greenhouse gases and increases in surface temperature of the earth.

Throughout the twentieth century, physicists made major contributions to the scientific understanding of the environment, coupled with major developments in technology for physical research. Mass spectrometry, a technique used to investigate the relationship between energy and matter, was developed by British physicist Joseph J. Thompson in the 1920s and became an essential technique in physics and chemical research. In the 1930s and 1940s, environmental physicists worked to develop radioisotope dating, which provided scientists with the ability to accurately measure the age of geological specimens. Environmental physics has also been used in the effort to create physical models used to predict the development of global circulation and climate systems. In 1969, Japanese meteorologist Syukuro Manabe used data from atmospheric and oceanic physics to develop the first model of the combined circulation patterns of the ocean and atmosphere.

In the twenty-first century, environmental physics has become a distinct area of research and an important part of environmental science, a field that combines efforts from a variety of related sciences to develop a full scientific understanding of environmental processes. Environmental physics can also be divided into a number of more specific disciplines, including geophysics, which studies the physical principles of the earth’s lithosphere, and atmospheric physics, which creates models of physical interactions within the atmosphere. Environmental physics has also been essential to ongoing efforts to develop sustainable energy technology.

Core Concepts

Radiometry. Radiometry is a series of techniques used to measure and study radiation, or the dispersion of energy. Physicists use radiometry to study radioisotopes, which are variations of an atom that are unstable due to the presence or absence of neutrons within their atomic structure. Radioisotopes decay by releasing energized particles in the form of radiation, and thereby transform into more stable isotopes. Decay counting is a technique used in radiometry to measure the distribution and activity of radioisotopes within an environmental sample. Decay counting involves first measuring the number of decays that occur during a certain period of time. This data can then be used to estimate the abundance of certain isotopes.

There are a number of methods used for decay counting, including liquid scintillation counting (LSC) a method that utilizes liquid solvents, like benzene or toluene, to dissolve samples of material containing radioisotopes. These liquids fluoresce—or release visible light—when they come into contact with charged particles. As radioactive decay occurs, releasing alpha and beta particles, light is produced and transmuted into electromagnetic pulses, which can be detected and measured to provide an estimate of the activity and abundance of radioactive material within the sample.

Spectroscopy. Spectroscopy is the study of how radiated energy interacts with matter. There are a variety of techniques used to study spectroscopic principles, including spectrometry, which is a collection of methods used to study the behavior of certain spectrums of energy. A spectrum is the variation within a certain form of energy that can be separated according to measurements of intensity, wavelength, or a variety of other factors. Spectroscopy primarily studies radiated energy in terms of its wavelength.

One of the most important spectrographic techniques in environmental physics is differential optical absorption spectroscopy (DOAS), which is a technique developed by environmental physicists to measure trace gases within a gas sample. A typical DOAS device consists of a chamber containing a gas sample that is subjected to a continuous source of light. Measurements then show how gases in the sample absorb some of the light passed through the sample, thus providing a measurement of the amount of trace gases within the material.

Mass Spectrometry.Mass spectrometry is a series of techniques used to measure the physical composition of a mixture or a sample of material. The basic principle is to separate ions—or charged particles—within a mixture based on their mass and electrical charge ratio and then to use a detector to measure proportions of different ions within the mixture.

Accelerator mass spectrometry (AMS) is one of the major techniques used by environmental chemists and physicists to measure the physical abundance and activity of isotopes in the environment. The basic technique involves using a specialized device to accelerate ions to high speeds, thus increasing the kinetic energy of the sample, before analyzing the sample. Acceleration serves to separate various types of ions from the sample and is useful in attempts to separate and analyze proportions of rare isotopes within a sample. AMS measurement techniques are also used in radioisotope dating.

Eddy Covariance. Eddy covariance is a method used to study turbulence or variation within the layers of the atmosphere. Physicists and meteorologists use eddy covariance to measure the flux—or physical movement over time—of atmospheric components like carbon dioxide, oxygen, and water vapor by comparing the vertical movement of these materials with their horizontal movement through the atmosphere. Measurements are typically achieved through eddy covariance flux towers, which are tall structures equipped with mechanisms used to measure the movement of materials in atmospheric currents, including infrared detectors and kinetic motion detectors.

Eddy covariance is important to meteorology and atmospheric science, helping to develop models of atmospheric movement that help explain meteorological and atmospheric changes over time. Eddy covariance has also been used in the development of oceanographic modeling and technology for weather monitoring used in the agricultural industry. In addition to detection and measurement equipment, eddy covariance also utilizes specialized computer programs to analyze and interpret the results of atmospheric measurements; these computer programs utilize contributions from environmental physicists and computer scientists.

Time-Domain Reflectometry. Time-domain reflectometry (TDR) is a technique used to measure the conductivity of electricity within electrically active systems. The basic technique involves subjecting a soil sample to an electrical charge and measuring conductivity within the soil. The system is advantageous because it measures moisture and salinity in a soil sample in a nondestructive way, thereby preserving the environment. Since the development of environmental TDR, environmental physicists and electrical engineers have been developing new software and sensing equipment to enhance the function of TDR for environmental research. Modern TDR equipment is able to provide highly accurate measurements of soil salinity and water content, which is useful in agricultural and geological research and development.

Ground Penetrating Radar. Ground penetrating radar (GPR) devices emit electromagnetic waves into the earth, which reflect off the surfaces of materials buried within the earth’s crust before returning to the surface, where the reflected waves are analyzed. GPR measurements can be used to study the distribution of subterranean water or ice as well as to search for buried fossils and other materials of interest to geoscientists. GPR development is essential to the petroleum industry, where the technique is often used to search for petroleum reservoirs; it is also used in the mining industry to search for deposits of ore and other minerals before drilling into the substrate. Geophysicists use GPR to study a variety of phenomena, including seismic activity and the movement and extent of subterranean water.

Applications Past & Present

Radiometric Dating.Radiometric dating is a technique utilizing the principles of radiometry to determine the age of geological samples by detecting proportions of different isotopes within the sample. Radioactive isotopes decay at specific rates, producing stable isotopes in the process. By measuring the proportion of unstable and stable isotopes within a sample, physicists and geologists can estimate the amount of time that has passed since the sample was formed within the earth. Newly formed rocks and geological formations contain higher levels of radioactive isotopes, which begin to decay as the rock solidifies and cools.

One of the most important methods for radiometric dating is radiocarbon dating, which evolved out of research by American physicist Willard F. Libby in 1949. Carbon-14 is a radioisotope of carbon that decays at a relatively constant rate to produce more stable varieties of carbon. To determine the amount of carbon-14 within a sample, scientists use decay counting techniques including liquid scintillation counting. Radiocarbon dating is useful for analyzing the age of samples of relatively recent origin, dating back to between 55,000 and 65,000 years before the present. In samples older than 65,000 years, radioactive isotopes of carbon are largely absent, having been replaced by stable carbon isotopes.

Uranium-lead radiometric dating is a technique used to estimate the age of older geological samples, and was most notably used to obtain one of the first scientifically accurate estimates regarding the age of the earth. Uranium-lead dating analyzes the proportion of uranium within minerals like zircon compared to the proportion of lead, which is the product of uranium decay.

Climate Modeling. The circulation patterns of air and water responsible for generating the earth’s climate are due in part of the transfer of energy between the sun and the materials that make up the planet’s environment. General circulation models (GCMs) use complex equations representing physical interactions to create detailed models of circulation patterns in either the oceanic or atmospheric environments. Physicists have also played a role in combining ocean GCMs with atmospheric GCMs to create atmosphere-ocean general circulation models (AOGCMs), which attempt to model the complex physical and energetic relationships between circulation patterns in both the ocean and atmosphere.

Climate modeling is important to meteorology, helping to predict both proximate and long-term developments in weather patterns. Climate models utilize detailed equations to describe the basic thermodynamic relationships and physical interactions that fuel climate change and the development of weather patterns. For instance, to accurately model tropical storm development, climate models must be programmed with the physical laws that govern the formation of storm systems.

Climate Change. Climate change science is an interdisciplinary branch of scientific inquiry that investigates physical, chemical, and biological factors that influence the earth’s climate in an effort to predict and model potential future changes in global climate patterns. One of the major issues in climate change science concerns the role of anthropogenic—or human-caused—factors affecting the earth’s climate, such as the release of greenhouse gases like carbon dioxide and methane from the burning of fossil fuels. Environmental physics research is used in determining how changes in the levels of greenhouse gases and other pollutants affect circulation patterns that might lead to global changes in climate.

The Intergovernmental Panel on Climate Change (IPCC), a group of scientists and researchers representing sixty countries, was formed by the United Nations in 1988 to coordinate international research on climate change. The IPCC funds and supports a variety of climate research programs around the world and publishes annual reports on the state of the earth’s climate and current theories regarding the future of climate change. Environmental physics plays a major role in IPCC research, helping to develop climate and atmospheric models and creating better sensing equipment to detect fluctuations in temperature and gas concentrations.

Wind and Water Power. Modern environmental physics research is often used in the development of sustainable energy technology, including wind and water power systems. Eddy covariance and other measurement systems used to study turbulence are essential in the effort to design machines to capture the kinetic energy of wind currents, which can be used to generate commercial and residential electricity. In the twenty-first century, wind power was used to generate more than 2 percent of the power used around the world and remained a major area of sustainable energy research. Environmental physicists contribute to the industry by helping to design more efficient technology for harvesting wind currents and work with electrical engineers to design systems for storing energy collected from wind farms.

Similarly, environmental physics research plays a role in modeling oceanic tide patterns, which aids in developing tidal and oceanic current energy systems. Utilizing hydroelectric dams, tidal dams, and wave power turbines, engineers capture the kinetic energy of ocean waves and water currents and transition this energy to electricity for commercial applications. Environmental physicists and engineers design equipment to more effectively harness energy from the hydrosphere (all the water of the earth). In the twenty-first century, environmental physics research has been utilized in the development of wave farms, an emerging field of hydropower generation that utilizes special machines to harness continual kinetic motion of waves near the surface of the water and transitions this power into electrical currents through the use of hydraulic pumps. Wave power is currently one of the major areas of research in sustainable energy.

Geothermal Energy Development.Geothermal energy is a type of heat energy that emerges from the earth’s core, radiating from molten rock (magma) and water heated by the radioactive decay of elements at the core. In some regions, including hot springs and areas near active volcanoes, geothermal energy rises close to the earth’s surface and can be used directly to provide heating. Heat arising from these naturally occurring formations can also be captured and utilized through heat pumps to provide heat for distant settlements. In addition, heat captured from geothermal sources can be used to generate electricity by utilizing the kinetic energy of steam to power electrical generators.

Engineered geothermal systems (EGS) use drilling to tap into geothermal sources that lie between three and seven kilometers beneath the earth’s surface. The resulting heat is then filtered into a system of reservoirs and used to create steam or heated water, which can be used to generate electricity. Environmental physics research is an important part of the ongoing effort to develop and refine EGS technology, which is expected to provide an important source of sustainable energy in the twenty-first century.

Geologists and geophysicists use ground penetrating radar and other geological exploration techniques to search for areas where geothermal pockets rise close enough to the surface to be useful for energy development. Environmental physicists also help to develop more accurate radar imaging techniques for subterranean exploration and help to develop physical models of convection currents beneath the earth’s surface, thereby enhancing efforts to more efficiently harvest geothermal energy.

Social Context and Future Prospects

Climate change research is at the forefront of scientific and political development in the United States and around the world, and this has created increased opportunities for specialists working in the environmental sciences. The environmental sciences industry as a whole is growing 3 to 4 percent faster than the average for all types of occupations in the United States. Much of this development comes from ongoing efforts to create better systems for monitoring environmental fluctuations and for developing green and sustainable energy sources.

Given growing international concern over climate change, atmospheric chemistry, physics, and climatology research has become a major priority in scientific development. Private, university, and government research programs around the world are seeking new ways to monitor greenhouses gases and environmental pollutants; environmental physics plays a major role in this endeavor. One of the most important areas of research concerns the continuing efforts to improve and refine climate models in order to make more precise predictions regarding the future of climate change given current conditions and expected future developments in pollutant levels. Environmental physics research is used both in the design of climate monitoring equipment and directly in the development of computer systems to model climate change on a regional and global scale.

As environmental consciousness has increased, in both the public and private spheres, there have been a variety of new regulatory systems put in place to control pollution, industrial emissions, and waste. The potential for increasingly stringent environmental legislation and restrictions has created a need for private and public research institutions to develop better monitoring and pollution control equipment. Environmental physics research will play an important role in the development of technology used to help meet these guidelines, including strategies for more efficient waste disposal, water purification, soil conservation, and land management.

Bibliography

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About the Author

Micah L. Issitt (BS) is a professional freelance writer and journalist specializing in writing on the life sciences and sociology. Issitt has written numerous articles covering environmental sciences and the history of environmental science in America.