Examination Procedures

All exams are graded on a 0 - 100% scale.

A.   Science

There will be two quizzes, date for each quiz announced in advance. The grade for each quiz will count toward 33.3% of the final grade (i.e., total 66.6%).

B.   Ethics

The ethics portion of the course (one quiz) will count as 33.3% of the overall course grade – equal to one quiz in the science part of the course.

C. Final Grade

A (quizzes # 1and 2) + B (quiz # 3) + 10 points (if class attendance is 90% or better) = Total number of points / 3 = Final letter grade, according to the "Uniform Grading" policy listed below.

SAMPLE QUESTIONS IN THE QUIZZES

The quizzes will be based on the contents of the textbook, reading assignments and the additional materials discussed in the class.

Please carefully read all the questions and provide the appropriate answers. Values in parentheses indicate the number of points carried by that question.

(30)    Define the following terms: air pollutant, troposphere, ---- ----------

(24)    Provide 2 major sources for each of the following air pollutants: SO₂, ------ ---

(16)    Compare how ozone is produced in the stratosphere versus the troposphere.

(30)    List important differences between London fog and Mexico City smog.

(25)    Define a public issue and provide 3 examples related to air pollution.

(15)    List 3 risk perception factors which affect public acceptability of an environmental hazard.

(30)    For each of the following, give one brief example of how an air pollution issue creates conflict between each pair of public ethical considerations:

—individual autonomy and the common good;

—professional/expert paternalism; and

—individual/citizen responsibility

Perspectives

Course Information

Exams

EXAM DATES

Quiz # 1: October 8

Quiz #2: November 14

Quiz # 3: December 12

Interactive Communication

A. Science

Response to unanswered questions in the class and answers to the questions in the quizzes (after each quiz) will be posted on this web site.

B. Ethics

Information similar to the science portion can also be found at the web site.

UNIFORM GRADING POLICY*

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Supplemental Reading assignment: Chapter 6

The Minamata Disease: A Case Study

http://www.env.go.jp/en/topic/minamata2002/

Summary Notes:

I.

1. Rapid industrial growth with no environmental concern (US, 1940 - versus Japan, 1940 -)

2. Symptoms seen, but cause unknown (Minamata, 1956 versus stipple of grape, 1952)

3.Methyl mercury (acetaldehyde production, primary pollutant) versus ozone (photochemical smog, secondary pollutant)

II.

Disease of the Central nervous system

A. Sensory, visual disturbance

B. Impairment of hearing

C. Loss of equilibrium

D. Cerebral infantile paralysis

Bhopal Disaster Comparison

Pulmonary Edema

III.

Methyl mercury content in the body = Intake – Exclusion = Steady state or

threshold = ~ amount of continuous intake

IV.

Indicators of Hg Accumulation: Fish, Shell Fish, Human hair

Consequence:

1956 - Minamata (2,955 people, symptomatic) versus
1984 - Bhopal (2,000 dead + 150,000-600,000 injured, 6,000 chronic mortality)

Cause:

Methyl mercury (water transport) versus methyl isothiocynate ? cyanide (atmospheric transport)

V.

Comparison of post-mortem costs in million $

Minamata: 2,955 cases (disease). ~ Ave. $26,000/capita/year

Bhopal: 600,000 survivors. Ave. $550/capita/one time

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Supplemental Notes

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Notes # 1.   

Textbook: Air Pollution, People and Plants by Krupa

Chaper 4: Transport of Air Pollution Across Regional, National and International Boundaries

1.   The occurrence of acidic precipitation is a classic example of trans-boundary transport of air pollution. It is a regional, inter-regional and continental scale environmental concern.

2.   Acidic precipitation is defined as precipitation with a pH value of less than 5.68. That is considered as the value for distilled water in equilibrium with atmospheric carbon dioxide at 25 °C at the sea level. However, that definition is questionable because:  (a) A pH value of 5.68 will be produced by the dissolution of ~330 ppm carbon dioxide in water. The present day carbon dioxide concentration is ~370 ppm. That will result in a pH value of ~5.4, and (b) Rain is a very dilute, highly unbuffered, complex mixture of chemical constituents that represents more than simply carbon dioxide in its dissolved state. Nevertheless, rain in general is acidic.

3.   The acidity of precipitation has been mainly related to the emissions of sulfur dioxide (being converted to sulfuric acid) and the oxides of nitrogen (being converted to nitric acid). However, the contribution of those acids to the acidity of rainfall is highly variable in space and in time.

4.   A particular precipitation event will vary in its composition between locations and no two-precipitation events at a particular location will have a similar chemical composition.

5.   Rainfall contains both insoluble and soluble chemical constituents. The soluble constituents exist as ions (positively charged cations, e.g., hydrogen or H⁺ and negatively charged anions, e.g., sulfate or SO₄^2–.

6.   Statistical correlations are used to establish relationships between the cations and the anions. Correlations (–1 to + 1 scale) are based on the variability in one parameter against the corresponding variability in another parameter.

—The square (R²) of the correlation coefficient (r) provides the numerical relationship. For example, the square of a correlation coefficient (R²) of 0.8 or 0.8²  =  0.64 or 64% of the variability of one parameter is explained by the corresponding positive variability in another parameter. Negative values show the opposite direction or in other words, while values of one parameter are increasing the corresponding values of the other parameter are decreasing.

—Thus, if the R² between H⁺ and SO₄^2– is 0.8, it simply means that 80% of the variability in H⁺ concentration is explained by the corresponding positive variability in SO₄^2– concentration. Negative value means that t two parameters are negatively correlated, in other words their variation proceed in opposite directions. When one parameter increases, the other decreases or vice versa.

—Analogously, in general the continuous speeds at which you drive a car are correlated to the amounts of gas consumed by that car (MPG or miles per gallon). Such information is calculated by many measurements of speed and gas consumption and then relating the two by correlation.

—Conversely, with negative correlation, more the number of questions a student fails to answer correctly, less the number of merit points a student will receive.

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Types of Acidity (H⁺)*

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(1)   Atmospheric or Environmental Acidity

H₂SO₄  ——>    2H⁺ + SO₄^2–

H₂SO₄   +   2NH₃  ——>   (NH₄)₂SO₄

(NH₄)₂SO₄  ——>     2NH_4⁺   +   SO₄^2–

(2)   Biological Acidity

2NH₄⁺   +   3O₂   ——>   2NO₂^–   +   2H₂O + 4H⁺   +   Energy

2NO₂^–   +   O₂   ——>   2NO₃^–   +   Energy

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H₂SO₄    =   Sulfuric acid               SO₄^2–          =   Sulfate ion

NH₃       =   Ammonia                   (NH₄)₂SO₄   =   Ammonium sulfate

NH₄⁺     =   Ammonium ion             NO₂^–          =    Nitrite ion

NO₃^–     =   Nitrate ion

* Alkalinity is represented by OH^–

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ACIDIC PRECIPITATION

(Summary of Conclusions)

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1.     Should the pH of unpolluted rain be considered to be 5.68? (Equilibrium of 330 ppm CO₂ in water at 25 °C and 1 atmospheric pressure or 740 mm Hg).

2.     Evidence from several publications suggest that the background pH of rain should be between 5.2 and 5.4.

3.     There are a number of insoluble and soluble chemical constituents in rain.

4.     It is the soluble constituents that are of immediate interest in ecological effects assessments.

5.     Acidic rain is considered to be largely due to the presence of H₂SO₄ and HNO₃.

6.     Such a conclusion is drawn from statistical correlations between the ions in rainfall.

7.     Overall, there is a spatial gradient of increasing rainfall activity from the west to the east in the US.

8.     There is a spatial gradient of increasing rainfall activity from the southwest to the northeast in Minnesota.

9.     There are significant spatial variabilities in the concentrations of ions in rainfall.

10.   There are significant spatial variabilities in the correlations between ions in rainfall. Thus, different locations may have different degrees of correlations between H and SO₄ and NO₃ ions.

11.   In Minnesota from 65 to 85% of SO₄ and NO₃ are in a non-acid form (essentially neutralized by other chemical constituents in the atmosphere, e.g., ammonium ion).

12.   There are differences in the composition of the rainfall, depending on the meteorological relationships between emission and receptor regions.

13.   The relationship between pH and ion concentrations in rainfall is parabolic in its nature, governed by regional scale climatology.

14.   There is a distinct seasonality in the occurrence of high SO₄ (summer) and NO₃ (winter) in precipitation.

15.   In Minnesota there are weak acids (organic) in rainfall at concentrations higher than strong acids.

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Notes # 2.

Textbook: Air Pollution, People and Plants by Krupa

Chapter 5: Air Pollution and Global Climate Change

Vegetation Responses:

I. There are three types of terrestrial plants: C3, C4 and CAM (Crassulacean Acid Metabolism)

C3 plants:   Plants that use rubisco (Ribulosebiphosphate carboxylase) to make a three-carbon compound as the first stable product of carbon fixation. These plants may lose up to 50% of their recently fixed carbon through photorespiration. More than 95% of earth's plant species can be characterized as C3 plants.

C4 plants:   Plants that use PEP (phosphoenol pyruvate) carboxylase during initial carbon fixation to make a four-carbon compound that is subsequently transferred to specialized cells where carbon dioxide is internally released and refixed using rubisco. This phenomenon greatly reduces carbon loss by photorespiration, and in many cases, it completely inhibits it. Less than 1% of earth's plant species can be characterized as C4 plants.

CAM plants:   Plants that close their stomata during the day to reduce water loss and open them at night for carbon uptake. PEP carboxylase nocturnally fixes carbon into a four-carbon compound that is accumulated within vacuoles. During the day, this compound internally releases carbon dioxide, which is then re-fixed using rubisco. This phenomenon also effectively inhibits carbon loss by photorespiration. Only about 3 to 4% of earth's plant species can be characterized as CAM plants. Examples include – Cacti, Pineapple.


The following figure illustrates structural differences between C3 and C4 leaves.

(Figure Credit:  http://tidepool.st.usm.edu/crswr/c3vsc4.html)


Parts of the leaves are as follows:

1.   Vein: Site of transport of materials to and from the leaf.

2.   Air space: In contact with the mesophyll in C3 plants, thus permitting photorespiration. Not in contact with the bundle sheath cells which are the sites of the carbon fixation in C4 plants.

3.   Mesophyll cells: Sites of photosynthesis and photorespiration in C3 plants. Non-photosynthetic cells where carbon dioxide is incorporated into organic acids in C4 plants.

4.   Bundle sheath cells: In C3 leaves, these cells surrounding the vein are non-photosynthetic In C4 leaves these cells are the sites of the carbon fixation.

5.   Stoma: One of the many openings on the undersurface of the leaf through which air enters the mesophyll.


Some Differences Between C3 and C4 Plants

Based on many of the characteristics mentioned in the Table, responses of C3 plants to elevated carbon dioxide will be higher than C4 plants.



II. Plants as a Sink and a Source of Atmospheric Carbon Dioxide

(Figure Credit: http://www.woodrow.org/teachers/esi/1999/princeton/projects/c3_c4/Group3web.html)



1.   During photosynthesis (in the daylight hours), carbon dioxide is absorbed and assimilated and oxygen is released from the leaves.

2.   During respiration, in the presence of oxygen, carbohydrate initially obtained through photosynthesis is metabolized to produce chemical energy and carbon dioxide is released.

3.   There are two types of respiration in plants: photorespiration and dark respiration.

4.   Photorespiration occurs in the presence of sunlight in the chloroplasts (cellular organelles that contain chlorophyll and conduct photosynthesis) found in the mesophyll cells on the upper side of the leaf.

5.   Dark respiration occurs in all cells (shoots and roots), in their mitochondria (cellular organelles generating the needed power to maintain cellular activities), both during daylight and at night.

6.   During photosynthesis, plants take up carbon dioxide through pores on the leaves known as “stomata”. Stomata serve in gas and water vapor exchange between the plant and the atmosphere.

7.   To conserve water and due to a lack of sunlight, plants close their stomata at night, but not completely by 100%. There are over 200 temperate plant species that have been shown to have open stomata, to varying degrees, at night.

8.   Plants contain stomata on their leaves (one or both sides) and on green stems. In woody plants, hardened stomata like structures called “lenticels” are found on the exterior cell layer of the trunk.

9.   In as much as plants absorb carbon dioxide during the day through photosynthesis, it is released at night through respiration.

10.  Carbon dioxide concentrations in the air within and immediately above plant canopies can be substantially high during the night. They are products of plant + soil respiration (includes plant roots and soil microorganisms).

11.  There are different mechanisms by which plants release carbon dioxide into the atmosphere at night.

(A)   Since the stomata are not closed 100% at night, some carbon dioxide is released through that pathway, depending on the internal and external resistance.

(B)   The main physical barrier on the leaf is its cuticle. The cuticle is never formed or maintained perfectly. Some internal carbon dioxide is lost by diffusion through that pathway, particularly since there is a build-up of carbon dioxide concentrations in the air spaces between cells in the leaf. That diffusion will continue until the internal plant and external atmospheric carbon dioxide concentrations reach equilibrium.

(C)   The lenticels (hardened stomata) also serve as an outlet for carbon dioxide, since they are open all day.

(D)   In addition to the shoots, the roots are a major source of nighttime carbon dioxide evolution from plants.

12.  The actual or specific contribution of each pathway (with the exception of soils and roots) to the night-time carbon dioxide concentrations have not been quantified due to a lack of appropriate experimental methods, but they have been calculated.

13.  The results vary with the growth stage, environmental conditions (living and non-living), plant species and its type (C3, C4 or CAM).



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Additional Notes

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Sulfur and Plants
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1.   Sulfur is an essential element for plant growth (normal range of roughly 0.2 – 0.4% of the leaf dry weight, depending on the species).

2.   Soil is the predominant source of sulfur for plants (soil sulfur is taken-up as sulfate).

3.   All plants accumulate the required amounts of sulfur in their foliage to achieve sulfur sufficiency.

4.   Symptoms of sulfur deficiency resemble those of nitrogen deficiency (chlorosis of older leaves).

5.   Sulfur in plants exists both as organic (proteins, vitamin B2, etc.) and inorganic (sulfate) molecules.

6.   While organic sulfur is essential for growth, excess sulfur is stored in the inorganic form (sulfate).

7.   In plants that have their sulfur requirement satisfied, additional overload due to exposure to sulfur dioxide from the air can lead to injury and growth and yield losses.

8.   Primarily, sulfur dioxide diffuses into leaves through stomata, although some entry may occur directly through the cuticle.

9.   Within the cell:

(Sulfur dioxide)  —>  (bisulfite ion)  —>  (sulfite ion)  —>  (sulfate ion)
                            (1)                            (2)                       (3)

[Sulfur dioxide = SO₂; Bisulfite = HSO₃^–; Sulfite = SO₃^– and Sulfate = SO₄^2–]

If reaction # (2) occurs faster than reaction # (3), resulting in the accumulation of sulfite, then there will be negative effects.
If reaction # (3) occurs faster than reaction # (2), resulting in the accumulation of sulfate, then there will be no negative effects.

10.  In sulfur deficient soils, low levels of sulfur dioxide can stimulate plant growth.

11.  Acute Exposure:

E.g., one-half to a few ppm for several hours. Will frequently lead to foliar injury symptoms within days. However, injury may or may not result in growth effects and yield loss.

12.  Chronic Exposure:

Several ppb for days, weeks and whole growth season, with periodic, random occurrences of short-term (e.g., few to several minutes) peaks or episodes. May or may not result in injury symptoms, but can result in growth and yield reductions.

The frequency of occurrences of the peaks or episodes and the cumulative exposure (concentration X duration) fit best with observed effects.

13.  List of some agronomic and horticultural crops that are relatively sensitive to SO₂:

14.   Selected examples of agricultural crop species that have exhibited visible foliar injury under ambient conditions due to sulphur (SO2) contaminants from industrial point or source complexes:

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Some approaches to the recognition of air pollutant effects on crops and native vegetation

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1.   Mostly typical foliar symptoms of acute injury. Not systemic; does not spread (time course studies required).

2.   Similar symptoms on unrelated plant species growing in an affected area. Listings of sensitive plant species known for major air pollutants.

3.  Correlation between foliar injury and soil moisture availability (differences between irrigated vs. non-irrigated fields).

4.   Maximum crop or plant sensitivity during 2-3 months after onset of growth.

5.   Foliar injury on leaves at full expansion or 2nd and 3rd year needles on conifers.

6.   Random distribution of injured plants in a field. Infectious diseases start and spread from infection centers. Further, specific infectious pathogens in general are genus/family specific, there are exceptions, however [e.g., specific – late blight of potato does not spread to soybean or corn; exception – Pseudomonas (bacterial wilt) can spread to tobacco or to potato (same host family) or Verticillium albo-atrum wilt can spread to potato or maple (different host families)].

7.   Use of biological indicators and/or native vegetation.

8.   Foliar analysis (e.g., sulfur; fluorine occur in elevated levels in stressed plants). Negative results in microscopy and Koch's postulate (step 1; isolation). Negative results in re-inoculation with extracts of injured plant tissue.

9.   Comparisons of charcoal-filtered versus unfiltered treatments and/or comparisons of differences in geographic space.

10.  Crop cultivar and intra-species differences in response.

11.  Chemical spray tests for protection vs. no protection against air pollution injury.

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Factors governing the joint effects of air pollutants on plants

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1.   The physical form of the pollutant.

2.   The chemistry of the pollutant.

3.   Pollutant dose (concentration and exposure duration) and uptake.

4.   Co-occurrence of a pollutant with the others (simultaneous, inverse, sequential, random etc.).

5.   Toxicological properties of the pollutant.

6.   Ratios between pollutant concentrations.

7.   Growth conditions of the plant.

8.   Growth stage of the plant.

9.   Avoidance – compensation – repair – stress.

10.  No effect – hormesis – negative effects.

11.  Nature of the plant response parameter measured.

12.   Positive X negative effect interactions.

13.   Intra- and interspecies effects.

14.  Biotic and abiotic stress or stimulation factors.

15.  Pre-disposition (decrease versus increase) in response and time series of exposure and response.

16.   Holistic approach.