Environmental Science 102 Summer 2004 Set 5

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Exercises, problems, and questions highlighted in green are your assignments in addition to the reading.  Unless I indicate that these are to be turned in, they are to be treated as exercises to help you learn the material.

Words in bold type are terms you should remember for definitions, fill in the blanks. Warning: I'm not saying that a term or definition can't be asked about unless it's in bold type. This is to help you see the important terms.

Global warming and the greenhouse effect

First, these are not the same thing. The greenhouse effect is the natural, normal phenomenon by which the earth is as warm as it is. "Life as we know it" needs the greenhouse effect. Global warming is an exaggeration of the greenhouse effect, a warming far more than normal.

Normal warming, called the greenhouse effect, involves the absorption of outgoing infrared (heat) energy from the earth's surface by two gases in the atmosphere: water vapor and carbon dioxide.

Many of the charts and graphs linked in this section come from a National Oceanic and Atmospheric Administration website.

The carbon cycle
Because carbon dioxide in the atmosphere is a key component of the greenhouse effect and is also strongly implicated in the possible global warming, a review of the ways carbon dioxide enters and exits the atmosphere as part of the carbon cycle is needed.

How carbon dioxide enters the atmosphere

• Respiration, the oxidation of carbon compounds with the production of carbon dioxide. This is photosynthesis run backwards. All animal life that use oxygen produces carbon dioxide via respiration. This includes humans, microorganisms (biodegradation), and vegetation. In reaction form: carbon compound + oxygen --> carbon dioxide and water vapor.

• Combustion of carbon compounds with the production of carbon dioxide. This is the same reaction as respiration.

How carbon dioxide exits the atmosphere

• Photosynthesis, the production of carbon compounds and oxygen by green plants using chlorophyll, carbon dioxide, and water. In reaction form: carbon dioxide + water --> carbon compounds + oxygen

• Dissolving in water. Carbon dioxide gas dissolves in rainfall (natural acidity of rainfall) and in surface waters: streams, lakes, and, especially because of their size, the oceans. The reaction is carbon dioxide + water --> carbonic acid. Now the carbonic acid (H₂CO₃) will break apart somewhat to yield H⁺ (hydrogen ion- think acidity) and HCO₃^-1(bicarbonate ion). The bicarbonate will also break apart somewhat to yield H⁺ and CO₃^-2 (carbonate ion). In the ocean (mainly) the carbonate ions are used by marine life to make shells, combining calcium and magnesium ions with the carbonate to make calcium carbonate and magnesium carbonate (solids). The reactions: CO₃^-2 + Ca⁺² --> CaCO₃ and CO₃^-2 + Mg⁺² --> MgCO₃. The shells from marine life eventually sink to the ocean bottom and are buried. This sequesters (out of the active cycle) carbon for a long time.

Where carbon is stored in the biosphere: the atmosphere, in the bodies of living creatures (animals and plants, with forests being much longer term storage reservoirs), and in the water (especially the ocean, the single largest carbon storage area).

Know: how carbon enters, exits the atmosphere

See the Woods Hole web pages on the carbon cycle and know the answers to these questions:

1. What percent of our bodies are carbon?

2. How much carbon was released to the atmosphere from changes in land use, worldwide, between 1850 and 1990? How much is a petagram?

3. The boxed equation shows annual additions and subtractions of carbon from the atmosphere. What is the source of the largest addition per year? What is the main subtraction (sink)? Don't worry about the missing sink discussion, although you may find it interesting.

The earth's radiation balance

Incoming radiation is from the sun. The primary types of electromagnetic energy in solar radiation are ultraviolet, visible, and infrared (heat), with the sun's peak wavelength in the visible part of the spectrum. In percentage terms, about nine percent of incoming sunlight is ultraviolet, and the rest in split between visible and infrared energy. The peak energy, remember is in the visible.

Outgoing radiation (which must equal incoming) is from the earth. The earth's outgoing energy is all in the form of infrared.

Why the sun's peak energy is in the visible and the earth's is in the infrared part of the electromagnetic spectrum is explained by Wien's Law which states that the peak wavelength of a radiating body is equal to a constant divided by the absolute temperature of the body. In equation form:

peak wavelength (nanometers) = 2,898,000 / K (2.8 million divided by the absolute temperature, in K)

Where K is the absolute temperature in kelvins.
K = Celsius + 273

The sun's radiating temperature is about 6000 K; therefore its peak wavelength is 2,898,000/6000 or about 480 nanometers. This is in the visible part of the spectrum, which runs from about 400 nanometers to about 750 nanometers (see Set 4). The earth's radiating temperature is about 300 K; therefore its peak wavelength is 2,898,000 divided by 300 or about 10,000 nanometers. This is in the infrared part of the spectrum.

Therefore the earth absorbs solar energy (combination of ultraviolet, visible, and infrared) and reradiates it as infrared energy (only).

Infrared absorption

Heat energy, on its way out of the earth's atmosphere, is absorbed by gases. The two most important of these absorbing gases are water vapor and carbon dioxide. If it were not for the IR absorption by water vapor and carbon dioxide, the earth's average temperature would be much lower, about zero degrees Celsius. This natural absorption of outgoing IR energy and the consequent warming of the planet is the greenhouse effect.

Gases in the atmosphere (other than water vapor) that absorb infrared energy are called greenhouse gases. (Water vapor is normally excluded from the list of greenhouse gases, but don't forget that it is a strong absorber of infrared radiation and contributes greatly to the normal warming of the earth.) Besides carbon dioxide, methane, nitrous oxide (N₂O, not NO₂), ozone, and chlorofluorocarbons are strong IR absorbers. Carbon dioxide is the most important greenhouse gas, contributing about 50% of the IR absorption; the others, together, account for the other 50%. See the following chart.

Greenhouse gases' potential contribution to global warming:

This article discusses global warming and the greenhouse gases in turn. Know the answers to the questions below. The answers are in chapter 6, which is the URL I gave you in the previous sentence. An exception is question #1.

1. What is climate (radiative) forcing? See http://www.ace.mmu.ac.uk/Resources/gcc/2-3.html

2. What is the effect of an increase in radiative forcing?

3. What units are used for radiative forcing?

4. What does GWP stand for?

5. What is an atmospheric sink? What is the main sink for methane?

6. Which gas has contributed most to the total increase in radiative forcing? What percent of the total does this gas account for?

Changes in greenhouse gas concentrations

Although water vapor concentrations fluctuate greatly in space and time, overall the amount of water vapor in the earth's atmosphere is not changing. The greenhouse gases are increasing in air concentration:

Carbon dioxide has been increasing during the last century, according to many estimates. Accurate long term measurements have been collected in Hawaii for the last 40 years. Methane, nitrous oxides, and CFCs have increased also. This table shows the rates of increase for the greenhouse gases. This table from the Carbon Dioxide Information Analysis Center has more extensive lists of gases, warming potentials, and atmospheric residence times. The data from Hawaii are discussed in the CDIAC pages. Know the answers to these questions from the CDIAC:

1. What is the name of the instrument used to measure carbon dioxide?

2. How often are the Mauna Loa measurements taken?

3. Click on the Digital Data icon at the top of the page. When did these measurements begin?

The links show carbon dioxide and methane trends.

Carbon dioxide trends

Methane trends

All things global warming are found at http://globalchange.gov/

Human Actions

There is strong evidence of human actions being the cause of the increased carbon dioxide levels. Combustion of fossil fuels (petroleum, coal, natural gas) produces carbon dioxide and of course their use has increased dramatically during the last century. Also, worldwide, more vegetation (forest) is being removed than is being replanted. This deforestation results in less carbon being held as part of trees and more carbon dioxide transfer to the air. The deforestation is mainly the result of clearing additional land for crops or grazing, and the vegetation is burnt (combustion conversion to carbon dioxide) or is allowed to rot (biodegradation = respiration, conversion to carbon dioxide by the decomposers).

The greenhouse gases and their humans sources are listed in the table.

Prediction

If greenhouse gases absorb outgoing infrared energy and this causes the greenhouse effect, then additional greenhouse gases should absorb more infrared energy and increase the greenhouse effect beyond its normal bounds (global warming).

The computer models project a 1.5 - 4.5 degree Celsius increase in global temperature if the carbon dioxide levels in the atmosphere double (from about 350 ppm to 700 ppm). According to mid-range projections by the models, carbon dioxide levels will reach 700 ppm by the year 2100.

This chart shows projections of global average temperatures calculated by computer models.

Adverse effects of global warming

1. A change in weather patterns. The current rainfall levels seen (and expected for agriculture) in the American Midwest could shift northward into Canada.

2. Rising sea levels, due to the thermal expansion of the oceans and the melting of the polar icecaps and the Greenland Ice Sheet, flooding coastal areas and damaging estuaries.

Here is the USEPA list of possible adverse effects. See the sidebar listing various effects.

Uncertainties (aspects of global warming that should be acknowledged as not completely understood).

1. The actual temperature record. The earth's temperature increased about 0.5 degrees Celsius during the period 1880-1940, prompting commentators during the 1930s to coin the term "greenhouse effect". From 1940-1970, temperatures decreased about 0.2 degrees C, and there was talk of a possible small ice age. From 1970 to the present the trend has been up, about 0.3 degrees C. A question arises: why should the most pronounced increase occur 1880-1940, when the greenhouse gases were increasing only slowly and why did global temperatures decrease during 1940-1970, when greenhouse gas concentrations were increasing rapidly?

2. Temperature record bias. Temperatures that are used for tracking global trends have come from meteorological stations. These stations were usually located on the edge of an urban area; in the United States during the 20th century it has been common for the National Weather Service to be at the airport. So in many cases 50 years or more of temperature readings for an urban area have come from the airport weather station. Now, urban areas are warmer than the surrounding countryside because in the city a smaller area is covered by grass and trees, which have a cooling effect and a greater area is covered by buildings, asphalt, and concrete, all of which absorb and retain heat. Also, the urban area will have many heat sources itself, from fuel combustion mainly. This phenomenon is called the urban heat island ( FYI see, e.g., Project ATLANTA - Urban Heat Island Study and Heat Island Group Home Page). Well, cities have grown during the time that the weather station has been recording temperatures and the urban heat island has approached (or surrounded) the weather station. The weather station has recorded higher temperatures, but why? Because the city has grown toward it, not because it has detected a global warming. The statisticians studying global temperature trends acknowledge this upward bias in the temperature record; the question is what correction factor to apply, i.e., can the urban heat island explain all or only part of the observed higher air temperatures?

3. Computer simulation models, although powerful, are only as good as the relationships that are coded in them and the data they use as input. The atmosphere is incredibly complex and the models used to predict changes in the weather, much less the climate, are primitive compared with the phenomenon they are trying to simulate.

4. Feedback effects in the computer simulation models. This is an extension of the model discussion above. How the model handles changes in its variables as time proceeds can greatly affect its long-term prediction. For example, how does the model treat clouds? If the earth gets warmer, then more evaporation will create more clouds. More clouds in the atmosphere mean more heat-absorbing water vapor, which means more atmospheric warming, which means more evaporation, more clouds, etc. But clouds also increase the albedo of the earth. The albedo is the percent of the incoming solar radiation that is reflected back to space. More cloud cover, more albedo, more reflection. With more reflection, less solar radiation gets to the ground to be absorbed and reradiated as infrared. Less infrared, less warming. So do clouds increase or decrease warming? The model will simulate both effects; which of the two will predominate is a matter of the relationships in the computer code. Another potentially important factor is the type of clouds, which can either cool or warm the earth.

5. Long term trends. As with ozone layer depletion, the data set we are using to make predictions to the middle and end of the 21st century are limited. The earth's temperature fluctuates naturally, we know. On what time scale and by how much and when is uncertain. Are the changes in temperature that we are seeing the result of natural fluctuations? (yes, but we don't know how much). Are they the result of human activity? (probably, but by how much we don't know).

6. Other pollutant gases are cooling the atmosphere. Sulfates formed from sulfur dioxide emissions exert a cooling effect on the atmosphere by blocking incoming solar energy. For a period after Mount Pinatubo erupted, which sent millions of tons of sulfur compounds into the atmosphere, the earth's temperature declined (1991-1993).

Solutions

Most of the solutions put forward against global warming are focused on CO₂.

• Lower fossil fuel consumption, which will lower carbon dioxide emissions.

• Reforestation. Plant more trees, which will remove carbon dioxide from the atmosphere and keep the carbon in the vegetation for several decades (as opposed to an annual plant which dies and is decomposed within one year).

International agreements to work against global warming: Global Warming: Actions -- Global.

The most recent of the international agreements is the Kyoto Protocol (Read the summary for the basics) (full text , FYI). The UN Framework on Climate Change has a beginner's guide that is useful.
Know these basics of the Kyoto Protocol:

• binding greenhouse gas emissions targets,

• credit given for planting trees,

• developed countries have different requirements than developing countries,

• international emissions trading allowed. This is similar to the U.S. sulfur dioxide emissions trading under the acid rain control provisions of the Clean Air Act.

The Intergovernmental Panel on Climate Change produces periodic reports which have influenced the debate on global warming. Know what the IPCC is and its basic purpose.

For further reading

• The Carbon Dioxide Information Analysis Center at Oak Ridge, Tennessee has a comprehensive set of information. See their FAQs, for example.

• Globalchange.gov A comprehensive site.

• The USEPA global warming page: The EPA Global Warming Site

• The National Oceanic & Atmospheric Administration climate site: The Climate Diagnostics Center

• Is global warming for real? Science Has Spoken: Global Warming Is a Myth

• Other explanations The Iceman Cometh and Goeth

• Another skeptical article (includes the urban heat island discussion) National Policy Analysis #218: Buenos Aires Conference On Global Warming: Much Ado About Nothing - October 1998

• Global Climate Web Sites This Australian site has a wealth of information.

Waste management

I. Waste generation rates

Municipal solid waste (from homes, businesses - nonhazardous) in the United States: about 230 million tons in 2001.
How many pounds per day per capita (person) is this?

Read these waste generation facts.
1. What is the largest category of municipal solid waste?
2. Describe the change in municipal solid waste generated, in pounds per capita in the U.S., 1960-2001.
Household hazardous waste.
1. The U.S. produced about 40 million tons of hazardous waste in 2001. The waste came from about 20,000 hazardous waste "generators", as the USEPA calls them. Municipal solid waste generated by you and me can also contain hazardous waste. Know a few examples of consumer products that can contain hazardous waste.

II. Definitions

The difference between a hazardous and a nonhazardous waste is a matter of regulatory definition, which is based on provisions of the key federal statute concerning waste management, the Resource Conservation and Recovery Act (RCRA). The USEPA defines a solid waste and then within the category of solid wastes the regulations define which wastes are hazardous. If a waste isn't hazardous, then it is nonhazardous. Get it?

What is a solid waste? Directly from the USEPA web pages:
[a] solid waste means any garbage, or refuse, sludge from a wastewater treatment plant, water supply treatment plant, or air pollution control facility and other discarded material, including
solid, liquid, semi- solid, or contained gaseous material resulting from industrial, commercial, mining, and agricultural operations, and from community activities.
Notice that a solid waste can be a "solid, liquid, semi-solid, or contained gaseous material".

And solid wastes are classed as either hazardous or not.

A. Hazardous waste

A waste is hazardous if (from the USEPA again):
[Wastes that] exhibit certain characteristics may be regulated by RCRA. A waste may be considered hazardous if it is ignitable (i.e., burns readily), corrosive, or reactive (e.g., explosive). Waste may also be considered hazardous if it contains certain amounts of toxic chemicals. In addition to these characteristic wastes, EPA has also developed a list of over 500 specific hazardous wastes. Hazardous waste takes many physical forms and may be solid, semi-solid, or even liquid.

A waste can be hazardous, then if:

1. It possesses certain characteristics:

• ignitability

• corrosivity

• reactivity

• toxicity

The first three characteristics are measured by standard laboratory tests published by the USEPA. The fourth, toxicity, is checked by a standard procedure, too, but I want you to see how "toxicity" is defined here. It is not done using test organisms, but is, rather, a test that mimics how toxic materials might escape from waste (dissolve in a liquid, represented by an acid) and then measures whether too much of a toxic material is present in the escaping liquid.. This involves washing the waste with an acid solution and then testing the solution for the presence of various chemicals. If any of the chemicals are present in the acid solution at concentrations exceeding the USEPA thresholds, the waste is considered to possess the toxicity characteristic. Many industries pay an outside lab to conduct these tests. If a waste is defined as hazardous by one of these four tests it is called a characteristic hazardous waste.

USEPA test methods information.

Or a waste is considered to be hazardous if:

2. It is on an EPA list

If a waste is determined to be hazardous because is on a list of chemicals or industrial processes that the EPA has defined being hazardous by nature, is is called a listed hazardous waste.

A short USEPA guide for waste identification.

In any case, the generator is responsible for determining whether a waste is hazardous or not.

B. Nonhazardous waste
Any waste not defined as hazardous by the methods discussed above: municipal solid waste may contain some waste that is actually hazardous (by EPA definition) but there is no requirement for domestic waste to be tested or classified; it is treated as nonhazardous waste.

IV. Waste treatment and disposal methods

• Landfill

• Incineration

From the waste generation facts again, know what percent of U.S. municipal solid waste is recycled/composted, what percent is landfilled, and what percent is incinerated.

A. Landfill (aka a sanitary landfill, one following Resource Conservation and Recovery Act regulations). USEPA landfill pages.

1. Potential problems

a. Groundwater contamination by leachate. USEPA glossary definition of leachate. (A much better source of definitions of all kinds is the Facts On File Dictionary of Environmental Science, by Bruce Wyman and Harold Stevenson.)

b. Gas migration (methane, an explosive gas, and hydrogen sulfide, which is highly odorous and toxic, are produced by anaerobic decomposition of organic matter.

c. Litter, dust, odors.

2. Solutions to the potential problems

a. Leachate controls: "impermeable" liner on bottom of landfill, prevents (greatly slows) the escape of leachate. Liner materials include compressed clay and various synthetics. Impermeable is within quotation marks because all liner materials are (very slightly) permeable, actually. The rate required by government regulations is quite slow, however: 1 ten-millionth of one centimeter per second. ( But figure out how far leachate could penetrate at that rate in 30 years.) For more background, see this article on synthetic liners and this article on Why Landfills Leak.

USEPA glossary definition of liner: Liner - Structure of natural clay or manufactured material (plastic) which
serves as a barrier to restrict leachate from reaching or mixing with ground water in landfills, lagoons, etc.

Landfills install leak detection systems (scan through the article to see what is possible) and incorporate leachate controls. Leachate collection systems, installed on the bottom of the landfill, this is a layer of sand or gravel into which are sunk pipes connected to the surface. Any leachate that seeps to the bottom of the landfill (and could, over a long time, get through the liner) is pumped up to the surface, keeping the bottom of the landfill relatively free of liquid.

Leachate controls: rainwater runoff is diverted away from the landfill to minimize the water that might seep into the waste, producing leachate. Also, the completed parts of the landfill are capped with an impermeable material to prevent water infiltration from the top.

b. Gas migration controls. This usually is a network of plastic pipes sunk into the landfill to provide a path for the gas produced underground to get to the surface. The gas is either just allowed to mix into the atmosphere or, at times, the methane is collected and used as an energy source.

c. Litter, dust, odor controls. A daily cover of approved soil is applied to a minimum depth to the top of the buried waste.

This USEPA guide for landfill operators covers these controls.

What is flow control? What economic purpose does flow control have? What the the U.S. Supreme Court decide about flow control?

A tipping fee is the cost per ton of waste assessed by a waste disposal facility. This site has U.S. tipping fees, by region, 1985-2002. What was the average landfill tipping fee in the U.S. In 2002? Where are the highest tipping fees? What was the tipping fee in the South Central Region in 2002?

B. Incineration

This method's biggest advantage is volume reduction. For municipal solid waste (a mixture of many different items, some combustible, some not), the reduction is 80-90%. For specialized, homogeneous waste streams, well over 99.9% of the waste will be gasified. Remember, matter can't be destroyed, so we are changing its form. Also note: because incineration of municipal solid waste doesn't destroy it all, there's still a need to landfill the noncombustible items, as much as 20 percent of the total waste by weight.

V. Recycling

Consult the waste facts pages again. What kind of waste has the highest recycling rate? What percent of paperboard is recycled? What percent of all municipal solid waste was recycled in the year 2001?

Why does this article think that recycling rates are slowing?

These are two industrial goods recycling pages. As you can see, they're not feel-good participants; this is a big business.

1. The Recycler's Exchange

2. The National Recycle Coalition

From the Recycler's Exchange pages (Click on the RecycleNet Composite Index at the top of the introductory page, then scroll down to Waste Paper Index. Click there and find the price of waste newsprint, per ton. How much is that per pound?

Find a recycling center near you.

1. Find one place in Lake Charles that recycles car batteries.

2. Where is the nearest place to McNeese that accepts used motor oil? (If the page says you need a plug-in, you don't need to install it. Also, the distances are apparently computed from a central Lake Charles spot. Just look at the addresses and you'll see the one closest to McNeese.)

3. Note the value of scrap passenger tires. On Wednesday, July 7^th, the (March 2004) value was -1.75. The minus sign means that they have a negative value; i.e., the party with scrap used tires must pay someone to take them.

Copyright © 1998-2004 Bruce Wyman, Ph.D.
Last modification: 7/7/2004
http://www.faculty.mcneese.edu/wyman/102w/ensc102wSet5.htm

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