# AN INTRODUCTION TO THE FIELD OF ENVIRONMENTAL PHYSICS

Imagine you’re walking down a picturesque street. Trees line the sides of the walkway, there’s a breeze blowing, the sun is shining – maybe a little too hard. It’s just a little too humid for that time of the year. The birds that fly overhead around this time, migrating from the south, are nowhere to be seen. And all the flowers have bloomed, just a little earlier than usual.

We live in an age where the greatest threat to our future is, for once, not war, but climate change. Scientists and engineers across the world, from various fields in STEM, are working together to solve the problems this looming environmental catastrophe poses. In light of this situation, the field of environmental physics – an interdisciplinary field of science that involves exploring environmental phenomena from a physics perspective – is undeniably relevant.

Although it seems unlikely that two vastly different fields such as physics and environmental science could be connected, that is not the case. The principles of physics can be used to determine the energy and heat flowing in and out of ecosystems, the way water carries sediments, how warm and cold ocean currents circulate and influence aquatic ecosystems, and yes, how pollutants and greenhouse gases are transported through our atmosphere and environment.

This field is divided into various subfields like atmospheric physics and soil and sediment physics[1]. Atmospheric physicists apply mathematical and physical models, such as fluid dynamics theory and heat transfer, to the layers of the Earth’s atmosphere in order to analyse weather systems [2]. Their work involves calculations of atmospheric tides, weather phenomena such as thunderstorms and cyclones [2]. The National Aeronautics and Space Administration (NASA) has its own Atmospheric Physics and Weather Group, which studies processes such as the ENSO (El Nino Southern Oscillation) effect, cyclones and storms, and monsoons, using superlative satellite technology to record observations[3].

Soil physics deals with the physical properties of soil, including its components – like mineral matter, organic matter, liquid, and air[4], phases, and how energy or heat moves through the soil. It also includes sedimentation physics, which involves the flow of soil particles in rivers and streams, and the factors affecting this flow. This field can also be applied to agricultural land use as well, in which case it is called physical edaphology[4]: the use of the principles of soil physics to develop better agricultural practices and increase crop yield. Other subcategories in environmental physics include ocean physics. Ocean physics examines the gain and loss of heat through ocean waters and the interaction of the ocean with the atmosphere[10]. Scientists at NASA also study ocean currents and sea ice, as well as other factors like sea surface temperature and winds, to determine their effect on global weather patterns[12]. Monitoring such activity often provides valuable insights on how recent climate change is disrupting weather patterns. Just like in any other field of science, gaining information is critical – only when we understand how our activities have changed climate and weather patterns can we begin to solve the problem.

There are several real-life examples of how physics models have been applied to an environmental context. Though they may not fall in any of the subcategories of environmental physics, they are evidence of the potential this field could have in the future. The following examples highlight how the principles of physics can be used to develop a deeper understanding of our environment. As in any scientific field, gathering information and data is necessary, especially in order to calibrate our response to the climate change situation. Fortunately, physics provides us with the tools to do just that.

One significant example of using physics in environmental matters is the COMSOL Multiphysics software. It allows users to examine solutions to various problems, using multiphysics modelling[5]. In other words, this software analyses a particular situation in two or more physical fields: in physics, a field is a region in space where a particular quantity has a certain value – for example, the gravitational field. These variables are affected by fundamental laws in physics – for example, energy transfer uses the law of conservation of energy. COMSOL uses these laws and variables to simulate real-world problems. Founded in Stockholm in 1986 by Svante Littmarck and Farhad Saeid[5], this technology has been used in numerous situations that could potentially benefit our environment: for example, designing more efficient ways to clean up oil spills using hydrophobic (water-repelling) meshes, developed by the engineers at Amphos 21[6].

And that’s not all. Researchers at the National Renewable Energy Laboratory are using COMSOL to analyze the manufacturing process of biofuel (a renewable energy source that involves converting plant matter, known as biomass, into fuel) in order to make it cost-effective[7]. Several factors affect biofuel costs, such as the source of biomass (mainly corn in the U.S.), but the key bar for comparison is the corresponding cost of production of fossil fuel[13]. The average price for biodiesel (B-99-B-100) in January 2020 was $3.72 per gallon,$2.28 per gallon for ethanol, and \$2.59 for gasoline[14]. However, biofuel cost production may fluctuate with rising crude oil prices (which occurred in the U.S. data for 2017), as the production of biofuel itself may involve use of fossil fuels[13]. Separating fossil fuel usage from biofuel production would therefore significantly contribute to making it an independent, more renewable energy source. This particular research focused on mass and heat transfer in biomass, while further plans included studying the chemical reactions involved in the manufacturing process. The ultimate aim is to use the findings to build better biofuel producing reactors[7]. A separate analysis of biodiesel (a substitute for petroleum diesel) performed by Argonne National Laboratory, from its production stage to usage, revealed that use of 100% biodiesel reduced carbon emissions by 74% as opposed to regular petroleum diesel[11]. Clearly, increasing biofuel production efficiency would have a global impact on our current environmental crises.

Another, more technical, example is the technique of Accelerator Mass Spectroscopy, or AMS. AMS is a method of radiocarbon dating that relies on directly measuring the carbon-14 content (as well as other radioactive isotopes) in samples[8], made possible by the principles of nuclear physics.This is done in two steps: accelerating the rare ions or isotopes to extremely high kinetic energies using nuclear accelerators, and then analysing their masses[8]. Using this method, it’s possible to carbon-date, and therefore estimate the age of objects as small as seeds and leaves[8]. AMS has made crucial contributions to our understanding of the environment. In the field of oceanography, it has been used to measure carbon-14 content in the oceans in order to increase understanding of how ocean waters circulate[9], transfer heat and affect our climate. Since ocean currents play an integral role in determining wind and weather patterns, more information on them could lead to further understanding of how and why climate and weather conditions have shifted due to the greenhouse effect. AMS technology has also been used to analyse ice cores[9]. Ice cores from ancient glaciers contain small bubbles of air trapped from when they froze, allowing us to examine the composition of the atmosphere over one hundred thousand years ago. This technique allows scientists to compare today’s climate and solar activity to those in the past – and perhaps even surmise how and why they are changing. AMS’s superiority lies in its high precision compared to other methods of radiocarbon dating.

Fig. Accelerator Mass Spectroscopy

Some people say that physics is the mother of all sciences, and others, that our environment is the mother of all life: our Mother Nature. It is fitting then that the solution to the current environmental issues we face just might lie in the concepts of physics: in the field of environmental physics. Hopefully, researchers and scientists in this discipline will help create a more environment-friendly, sustainable way of life for the near future.

## References:

[1] Lochinov, Vasil and Tsakoski, Stefan:  ‘Multivariate statistical approaches as applied to environmental physics studies’, pgs 277-298 of  The Central European Journal of Physics 4(2),2006: www.degruyter.com/downloadpdf/j/phys.2006.4.issue-2/s11534-006-0012-3/s11534-006-0012-3.pdf

[3] Atmospheric Physics and Weather(329E), National Aeronautics and Space Administration: science.jpl.nasa.gov/EarthScience/AtmosphericPhysicsWeather/index.cfm

[4] R.Lal, M.Shukla: Chapter 1 of ‘The Principles of Soil Physics’, CRC press(2004)

[5] The COMSOL Group: The Origin of Multiphysics Software, the COMSOL Group: www.comsol.co.in/company

[6] Jorge Molinero, Addressing Oil-Spill cleanup Using  Hydrophobic Meshes, Amphos 21: www.comsol.com/story/addressing-oil-spill-cleanup-using-hydrophobic-meshes-54621

[7] Peter Ciesielski, Making Biofuel a Cost Effective Source of Energy, National Renewable Energy Laboratory: www.comsol.com/story/making-biofuel-a-cost-effective-renewable-source-of-energy-31791

[8] Accelerator Mass Spectroscopy(AMS)Dating, Beta Analytic: www.radiocarbon.com/accelerator-mass-spectrometry.htm

[9] National Research Council. 1999. Nuclear Physics: The Core of Matter, The Fuel of Stars. Washington, DC: The National Academies Press

[10] Marine Physics and Ocean Climate.National Oceanography Centre: https://www.noc.ac.uk/science/research-areas/marine-physics-ocean-climate

[11] Alternative Fuels Data Center: Biodiesel Vehicle Emissions and Life Cycle Emissions: https://afdc.energy.gov/vehicles/diesels_emissions.html

[12] Physical Ocean. NASA Science: https://science.nasa.gov/earth-science/oceanography/physical-ocean

[13] How competitive is biofuel production in Brazil and the United States International Energy Agency: https://www.iea.org/articles/how-competitive-is-biofuel-production-in-brazil-and-the-united-states

[14] Alternative Fuels Data Center: Fuel Prices: https://afdc.energy.gov/fuels/prices.html