Ecology Study Questions: History, Lead, Mercury, Soil, pH and Nutrients

IES Winter 2003

 

Note: This only refers to the ecology portion of the exam—for the policy portion, please review your notes and readings, and for the chemistry review your homework.

 

History of Ecology

1)    According to ecosystem ecologists what are the three dominant patterns of ecosystems?  Briefly describe each one.  Check a dictionary of ecology or ecology text, like Odum, if you are unsure.

Energy flow-The one-way movement of energy through the different trophic levels of a food chain from the sun to entropy.

Nutrient cycling- The circular movements of elements between the different components (abiotic and biotic) of an ecosystem.

Succession-  The chronological sequence of species within a habitat or community, e,g vegetational succession, the sequential change of different plant species over time on a given piece of land.

2)    Describe the contribution of two early ecologists.  For me Ellen Swallow was one of the most interesting and visionary (in her interdisciplinary and systems level focus) and Odum one of the most influential and organizational (especially in defining ecosystems ecology and systemitizing energy flow and nutrient cycling concepts).  A complete answer would include more than this one sentence!  There is no right answer—just one that is well-supported.

3)    What is the Green Revolution?

The Green Revolution started post-WWII in response to the fear of famine in various parts of the world.  The goal of the GR was to increase production of basic grains through breeding varieties that are responsive to irrigation, fertilizers and pesticides.  The latter were mainly developed as a by-product of WWII.  Rice and corn were the first green revolution crops.  In the 1960s some of the ecological problems with this approach were exposed (Silent Spring) and in the 70s the sociological results of this strategy(land tenure in the Punjab of India) were documented.

What is its relationship to Rachel Carson’s, Silent Spring?   The book is in response to the ecological and human health effects of pesticides, corner stone of green revolution methods.

4)    Do you think humans are part of nature? Why or why not?

Write your own opinion.

 

Jude VanBuren

Lead (Pb)

1)    If the lead level in blood exceeds 10 ug/dL it is considered poisoning.  What is 10 ug/dL in ppm? ppb?  Show your work.  One dL is 1/10th of a liter = 100ml.  Assuming the density of blood is roughly that of water 100 ml = 100g since (1 ml=1cc=1g of water).  Conversion factor 1ug/g = 1ppm.   10ug/100g = .1ppm or 100ppb

2)    Why are children less than 6 years old most at risk for lead poisoning? Hint: there are physiological as well as environmental reasons.  Children eat dirt and chew on painted surfaces that might have lead paint on them.  They absorb a greater percent of what they ingest than adults and have a higher respiration rate so that if Pb is present in dust from remodelling or soil it has a greater chance that it would be absorbed.  They are more susceptible because their brains are developing.  Why are pregnant women at risk? Pregnant women can transfer Pb from their bones to the fetus, since Pb acts like Ca in the human body.  Since the baby is developing neurologically it can be more influenced by Pb as it affects the nervous system.  Low birth weight and premature birth are common.

3)    What are the symptoms of lead poisoning? Mentally slow and learning disabilities also affects peripheral nervous system, damages heart, and raises blood pressure.  There is also evidence of greater aggressivity and other behavioral changes in children.  Can children have a high lead level but lack symptoms? Yes, and it is common.

4)    What kinds of nutrients can mitigate prevent absorption of Pb? Ca Fe, low fat diet.

5)    Since the year1750 there has been an exponential rise in Pb in the environment.  What are the major sources of exposure to Pb at present?  Though lead paint was banned in 1977, lead in gasoline in 1980s and PbAs stopped being extensively used in the 1950s due to a more effective insecticide (DDT) adoption and was completely banned in 1988, Pb is still prevalent in our environment.  Pb in paint is still present in old housing, as PbAs pesticide or deposition from gasoline exhaust in soil.  A piece of lead paint as big as a fingernail can cause intoxification.  Ceramics from China with acidic foods, leaded crystal, drinking water especially where delivered by lead pipes, solder from overseas canning with acidic fruits, old stained glass or vegetables are also sources. Foundries, battery manufacturers and recyclers, radiator repair shops all can release lead in the environment.  She did not mention toxic waste in fertilizer but it should be here.

6)    Explain why did various ag groups lobbied to include a clause that land in pear and apple orchards from the 1940s should not be planted to root and tuber crops in land transfer contracts.  Pear and apple trees were sprayed with PbAs pesticide starting in the late 1930s.  Roots and tubers such as carrots and potatoes are efficient in the uptake of Pb.  Two million dollars of carrots were disposed of because they contained overly high lead levels.

7)    What ion does Pb mimic in the mammalian body?  Calcium.  What are the route of Pb movement and the half time of ingested lead in various parts of the body?  It is ingested or comes through lungs in the case of inhalation and is for a 30d half life (hl) in the blood.  Then it moves into the brain (~7 years hl) and bones (~27 years hl) controlled by the parathyroid and other factors. Why is it transferred to the fetus?  Acts as Ca and is mobilized from the mother’s bones.

8)    If the effects of Pb were known to the Greeks, why did it take so long to ban it? The Greek physician Hypocrites knew of the abdominal cramping associated with high lead exposure.  But it was useful to developing industry and effective in agriculture. Humm, what do you think?   When did lead use as a pesticide begin in the US and when did it end?  First used early in 1900s as PbAs until mid-century and completely banned in 1988.

9)    Why do a higher % of Hispanic children in the “high risk” area of the Yakima valley have elevated Pb levels in comparison with the state average?  Two reasons.  They are exposed to PbAs in soil from previous fungicide spraying and paint in old housing.

10) How does globalization/free trade as it is currently practiced contribute to increase of Pb in the US environment?   It was a surprise to me that goods from abroad do not have to meet the US minimum levels of Pb—so ceramics with high Pb in glazes and canned food may have high and unregulated lead levels.

 

 

 

Mercury (Hg)

1)    What form of mercury is most toxic?  Methylated (mono- or di-methylated mercury) (90-95%)> mercuric or mercurous Hg (7%)  > elemental (0.01%) What organisms can take elemental mercury and change its chemical state? Anaeobic microbes Where are they found? In wetlands or GI track.

2)    Describe the mercury cycle. Elemental mercury falls from volcanic ask or coal burning or waste incineration or via streams draining industrial agricultural sources (used as a microbiocide) into lakes and wetlands.  Anaerobic microbes methylate and taken up by protozoa, then small zooplankton or crustacea (like small shrimps) etc. then on up the food chain until predatory fish, which we eat.  What are the natural sources of Hg in the environment?  Volcanoes and rock.  The presence of Hg in the environment has been estimated to increase five times over the background.  What are the anthropogenic sources of Hg in the environment? Landfill from discarded products, including fluorescent light bulbs, thermometers and thermostats; particulates from coal-burning; toxic industrial waste, some of which is put in fertilizers; dental amalgam; sewage sludge.

3)    What are the main three routes of exposure to Hg for adults and which is most important? According to Jude they are eating long-lived predatory fish #1, then inhaling Hg from liquid spills that are then heated (e.g. vacuumed to form vapor) and skin absorption through contact with elemental Hg and mercury containing skin creams (for burns).

4)    Where is mercury stored in the body?  Stored in fat.  What are the health effects of Hg for adults? Affects central nervous system and cardiovascular system.  For fetuses in the womb and children? Affects developing nervous system.

5)    What is a fish advisory?  A warning that a certain fish from a certain body of water contains contaminants. What Washington lakes have advisories for Hg? Whatcom lake for bass and perch. Roosevelt Lake for walleye, whitefish, sturgeon. Also swordfish, shark, tilefish, King mackerel and tuna steak.   

6)    Do the number of fish advisories reflect the amount of contamination in Washington State? No it reflects what they have tested!

7)    How many cans of tuna/week can you safely eat according to the fish advisory for tuna? One can for 125lb person.

8)    How does the Mercury Bill that has been introduced in the Washington legislation propose to reduce the sources of mercury in the environment? Removes items from the market for which there is a good substitute and take-back for products that contain mercury for which there is no easy substitute. Washington government is required to use items that contain mercury is a substitute is available.  Labeling for florescent lights so that people dispose of them properly. Which sources does it not propose to regulate? Dental amalgam, toxic wastes from coal burning or products in fertilizers, though hopefully the product take-back would ultimately impact this.

9)    Extra credit: Why does the seafood industry lobbyist oppose this Mercury bill on the basis that China is the source of the pollution? (This is truly the lobbyist’s point of view and it would be useful to know if there is data to back this up.)

 

Soil

1)    What is the difference between soil structure and soil texture?  Soil structure describes how the soil is aggregated; soil texture the % sand, silt and clay.

2)    What are the 4 components of soil and why are they important with respect to a plant?  Mineral component, organic matter component, water and air.  The mineral component anchors the plant and provides nutrients, water is necessary for the plant; air provide oxygen for respiring roots and organic matter provides nutrient to plant and nutrients and energy for the soil biota.

3)    What is a soil profile? A vertical crossection of the soil showing its layers.  What are the 4 common horizons and their characteristics? O is the litteror organic matter layer on top of mineral soil, A is the zone of elution or where the leachates (clay and salts like Ca) come from, root zone with higher organic matter, B is the zone that the leachates go to, PM or C parent material or rock.

4)    What is soil organic matter and what is its role in the soil?  Soil organic matter is decomposing plant and animal material in various stages of decomposition. 

5)    What is the parent material of soil in the south Puget Sound area?  Glacial till (leftover rocks, sand and gravel from the glacier.  How does it affect gardening and farming?  Rocks and gravel impede root growth, but the soil variability is the most difficult.

6)    What are the four soil orders found in Washington and what are their characteristics?  Inceptisols (Sound area), Ultisols (old red soil  just S of Olympia), Andisols (around volcanoes), Mollisols (Southeast and Central WA loess)

 

Soil pH and Nutrients

1)    Only 5% of the plant’s atoms that are not C, H or O and are called plant “nutrients”.  The nutrients in greatest concentration are called “macronutrients”. Which nutrients are macronutrients, and what are their cationic and/or anionic forms? NH4+ NO3-, PO4-3, HPO4-2, H2PO4-1, K+, SO2-2, Ca+2, Mg+2

2)    What are the micronutrients and what are their cationic and/or anionic forms (Note: I didn’t give you the cationic and anionic forms in lecture so don’t worry about this but I did include it here for your edification)? Zn+2, Mn+2, Cu+2, Cl-, Mo as MoO4-2, Fe+2, B as H3Bo4-.  Also Co+2, Ni+2 which were not mentioned in lecture, are other micronutrients that I am mentioning now because Duff Wilson mentioned Ni.   What is their general role? Catalysts for enzymes or one atom in the molecule.

3)    How much elemental N, P and K does a 12(N)-24(P)-12(K) fertilizer contain?  Show your work.  12% elemental N;  24% P  as P2O5=  .24*.44 = 10% elemental P;  12%K as K2O =  .12*.82 = 10% elemental K, where the molecular weight of P=31, O=16 and K=39

4)    What are the four ways that nutrients (or heavy metals) are held in soils? From less available to more available: as structural framework of mineral compounds, or structural framework of colloids (fine mineral particles), on the cation exchange complex (cations (like Ca++) are loosely adsorbed so available to plants) and in soil solution.   Which hold nutrients in a more available form? CEC and in soil solution.

7)    Define pH.  –log (H+]  What is an acid? A molecule that dissociates in water resulting in H+ ion formation. A base? A molecule that when it reacts with water an OH- is formed.  Why is soil pH called a master variable?  Because it influences all aspects of the soil—physical, chemical, biological.  The availability of soil nutrients, aggregation and directly affects the soil biota and plant vegetation.

5)    At what pH are most of the nutrients plants need available?  pH = 5.5-7  Which nutrients are most available at a low pH?  Fe, Zn, Mn At a high pH?  Ca, Mg, Mo

6)    What are the natural and human causes of soil acidity?  Decomposing organic matter and conifer residues (like pine needles) and plant uptake are natural, also soil weathering.  Human causes are nitrate fertilizers, mulch and acid rain.

7)    What is the role of nitrogen in the plant (animals too)? Important part of amino acids that make proteins.  How does a root absorb nitrogen? Nitrate nitrogen comes to the root in its uptake of water (mass flow).  Why is the symptom of nitrogen deficiency in plants chlorosis (yellowing) of leaves? Nitrogen is part of every enzyme including those that facilitate the formation of chlorophyll for photosynthesis.

8)    What is biological nitrogen fixation of legumes?  Nitrogen is taken from the air by bacteria  and put into a form that the plant can use through bacteria (or actinomycetes).  Why is it important?  It is the major way that nitrogen enters the biosphere from the air reservior.

9)  What is the role of phosphorus in the plant?   In nucleic acids, membranes, ATP.   How does the root absorb it (two ways)? Through growing towards it and by diffusion.  Mycorrhizae also brings P to the plant.  Mycorrhizae are beneficial fungi living symbiotically with the roots of plants and important in the uptake of P and water.  What are common P deficiency symptoms?  Purpling of leaves or stems.

10)      What is the role of potassium in the plant? Regulation of stomata (under conditions water stress), prevention of plant disease.  How does the root absorb it? It comes to the roots with the water.  What are common K deficiency symptoms? Yellowing, wilting, ie disruption in water balance, disease.

1)11) When purchasing a fertilizer, but trying to avoid heavy metals and other hazardous compounds, what steps might you take?  Check the WA government website to determine the heavy metal content www.wa.gov/agr/PestFert/Fertilizers/ProductDatabase.htm

12) What fertilizer may contain naturally occurring but high levels of which heavy metal?  Rock phosphate from the Western states may contain cadmium (Cd).

13) Check yourself on the nutrient deficiency symptoms.  Answers are in the “notes” mode of viewing the screen (so you can see the screen and a note pad below).

 H