HONR 297 Environmental Models Chapter 3: Air Quality Modeling 3.3: Typical Quantitative Issues

Typical Scenario Let’s consider the following typical (imaginary) situation. A large city has been shipping its garbage to a landfill in a nearby suburb for burial, but the landfill’s capacity is running out. Furthermore, the city is concerned about environmental problems related to the landfill that have popped up – they worry about increased liability due to shipping more garbage to the landfill. 2

Possible Solutions A consultant has been hired to find solutions to the landfill for trash disposal – three of the leading alternatives are: ◦ Build a new landfill in an unspecified location. ◦ Build a trash incinerator within the city limits. ◦ Build a trash incinerator at an unspecified location outside of the city. Bids have been taken on all three proposed options – all bids include both a specified level of recycling and either the burial or incineration of substantial amounts of trash! 3

Option Two Let’s focus on the second option – building a trash incinerator in the city. Suppose an extensive bid has been presented, with hundreds of pages that deals with many environmental issues, including air pollution issues, such as ◦ Exhaust gas composition, ◦ Control technologies, ◦ Concentration calculations, ◦ Health impacts due to emissions. 4

Bottom Line While most people wouldn’t have the time or technical expertise to wade through all of the details presented in the report, they most likely would want to know what is the report’s “bottom line”, i.e. what are the basic conclusions one can draw. What “key questions” could or should one ask to reach these conclusions? 5

Key Questions 1. What would be the “worst case” level of air pollution to be experienced by city residents as a result of this facility? 2. Where would this worst case pollution condition be expected to occur? 3. What would be the average level of air pollution expected to be encountered by residents in various parts of the city as a result of this facility? 6

Key Questions 4. Might any further development within the city have a significant impact on the amount of pollution caused by this facility? ◦ For example, what if more tall buildings are built in the city, near the incinerator? ◦ Could this lead to changes in air currents and cause downwash of pollution on city residents? 5. What types of weather conditions would lead to the highest pollution levels from this facility, and how likely are they to occur? 7

Constituents Who might be interested in these questions (and corresponding answers)? ◦ City leaders – mayor, city council members, other leaders from nearby suburbs and cities. ◦ Politicians – local, nearby, state, or federal. ◦ City agencies, nearby agencies, state, or federal. ◦ People who will work on the project or in the facility once completed – construction workers, scientists, engineers, plant managers and workers. 8

Constituents ◦ Facility neighbors – businesses, schools, homeowners, renters. ◦ Concerned citizens – city residents, neighboring suburb residents, people from nearby cities. ◦ Environmental agencies. ◦ Voters – possibly the plant construction or funds to build it will need to be approved in some sort of referendum. ◦ The bottom line is that there are many, many constituents involved! 9

Basic Principles In order to make informed decisions, even without detailed technical knowledge and understanding, it is a good idea to be familiar with basic principles related to any environmental issue of concern, whenever possible! For air pollution, one of the keys will be being familiar with and understanding equations such as the one on the next slide, which uses exponential functions to model plume concentration! 10

Basic Plume Model As we will soon see, the mathematical model given above can be used to determine concentration of material in a plume. This equation gives the concentration C of pollutant within a plume at essentially any location downwind, at any elevation! In order to understand this equation, we will need to review the basics of exponential functions – this will be done in the next section! 11

Resources Charles Hadlock, Mathematical Modeling in the Environment – Chapter 3, Section 3 12