George Mason University

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Our research focuses on the study of transport and diffusion of pollutants in the atmosphere. The main goal is to gain a better understanding of how contaminants move (transport) from their source and how they spread (dispersion) into the atmosphere. Why is the study of air pollution important? The health of any living creature is affected by the contaminants present in the air. Levels of contamination are defined as levels of concentration of a given substance in the atmosphere, where normal levels are assumed not to be harmful for life and any important deviation from these levels can produce a negative effect. In the last twenty years the increased level of chlorofluorocarbons (CFCs) and hydro-chlorofluorocarbons (HCFCs) has depleted the ozone layer in the southern hemisphere. With the depletion, ultra-violet radiation coming from the sun is not filtered, leading to an increase in the number of skin cancer cases for people living in that part of the planet. These two chemical components were in most of the aerosols commonly used. CFCs were expected to be phased-out in the year 2000 and HCFCs are expected to be phased-out in the year 2030 following the Montreal Protocol.

Accidents in chemical or nuclear plants are a main concern in modern society. A terrible example is Chernobyl, the Soviet nuclear power plant in Ukraine, where a meltdown of the fourth reactor occurred on April 26th of 1986. A controlled experiment went wrong, sending high levels of radiation into the atmosphere. The Chernobyl disaster affected 15 million people. Two cases of accidental spillage occurred recently at the city of Baltimore, Maryland. The first case, a spill of chlorine closed four lanes of a major highway on July 5th of 1999. The second case, more recently, was on July 18th of 2001. In this opportunity, a train carrying hazardous chemicals derailed and caught fire shutting down Baltimore's downtown area. Cases of accidental releases with the resulting emissions and dispersion of contaminants is common these days as more chemicals, toxic materials, biological substances are produced, used, stored and transported.

Health effects due to pollution from the daily activities of humans and accidents occurs without intention. However, there is a whole different class of pollution based on the intention of harming the health of people. The intentional release of pollutants can be done in two different circumstances: act of war, and terrorism.

The use of chemicals was common during World War I. After the end of the war their use was banned by the Geneva Protocol of 1925. The 1972 Biological and Toxin Weapons Convention went further banning development, production, acquisition and stockpiling of chemical and biological weapons. The 1993 Chemical Weapons Convention established a set of guidelines for verification and non-proliferation of such weapons. However, biological and chemical weapons remain a constant threat. Many countries still concentrate heavily on their development and production.

The terrorist threat is serious and has to be approached responsibly. An example of the harm that a terrorist attack can exert on society is the attack in Tokyo on March 20th of 1995, when a terrorist group released diluted Sarin gas in a subway. The death toll was twelve, and the number of injured people reached over 5,000.

Although the sources or reasons of air pollution can be so different, ranging from the release of sulfur gas in a volcano eruption to the release of sarin gas in a terrorist attack, they all share the same laws of physics that explain the process of transport and diffusion of contaminants into the atmosphere. A proper determination and prediction of levels of concentration can make the difference in saving lives or not. For instance, given any scenario where a harmful substance can be released, the ability to immediately pinpoint this region will enable authorities to determine both a proper evacuation route/plan while simultaneously monitoring neighboring regions for air quality. In addition, a clear understanding of how pollutants are transported and mixed with air helps to establish policies and rules for the industrial activities in order to control emissions of contaminants.