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Chem 321 > Chem Quiz 3 > Flashcards

Chem Quiz 3 Flashcards

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1
Q

What can ice cores tell us about GBCE?

A

Provide info about changes in cycles that have happened in the distant past

We have found that:
-Hg conc elevated during the last glacial maximum
- so we can infer that oceanic productivity was higher than it is today

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2
Q

How do bird feathers or peat bog help us identify changes in cycles? Case study?

A

Shows Recent and local changes

Sweden:
- analysis of bird feathers show a measure of cumulative Hg exposure to sea birds
- leads to the discovery of (Hg coated) seed dressing causing the biggest case of mercuric poisoning

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3
Q

What are redox reactions?

A

‣ Chemical processes in which electrons are transferred from one molecule to another

Not every rxn is a redox

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4
Q

How do you establish a redox equation?

A

‣ To establish a redox equation:
◦ 1. Determine oxidation state of involved ions
◦ 2. For both oxidation and reduction, establish separate equations
◦ 3. Apply the electro neutrality principle (changes on the left = changes on the right)
◦ 4. Add both half reactions

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5
Q

What is BOD?

A

Biological oxygen demand.

The mg of O2 required to carry out an organic carbon in 1L of water

2.7mg O2 dissolved in water oxidizes 1,g of organic carbon

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6
Q

Where can O2 be depleted ?

A

Rivers (O2 is replenished by contact with air)

Standing water (lakes, ponds) (dissolution of O2 in water is low compared to microbial mediated decomposition of dead biomass

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7
Q

Categorizing BOD

A

• Very clean: 1 mg O2 L-1
• Fairly clean: 1-3 mg O2L-1
• Doubtful purity: 3-5 mg O2 L-1
• Contaminated: >5mg O2 L-1

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8
Q

BOD in industry

A

◦ the BOD of industrial effluent as are measured to assess the extent to which their discharge could promote anoxic conditions when released into water

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9
Q

Methods to find BOD

A

◦ Methods
• Consist of filling an airtight bottle with sample (to overflowing). Then incubating the bottle at a specified temperature for 5 days. Now we can find dissolved O2 (DO) which is used to calculate BOD
• BOD = final (DO) - initial (DO)

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10
Q

______ of O2 concentration in a river can help us detect_______

A

Longitudinal analysis

pollution of oxidizable organic matter/pollution

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11
Q

What are the four equations of the diurnal cycle of water in Pine Creek, 2003

A

a. CO2 +H2O —> O2 +CH2O
B. HCO3-+ H+ —> CO2 +H2O
C. CO32- +H+ —> HCO3-
D. 1/2CaMg(CO3)2 (dolomite) —> 1/2Ca2+ + 1/2Mg2+ +CO32-

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12
Q

What do sewage treatment plants do?

A

Oxidize organic matter

Rate at which this occurs is important

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13
Q

How does aerobic respiration occur?

A

when lake/pond becomes depleted of O2, and aerobic organisms cannot survive, anaerobic organisms dominate. They use alternative oxidants that don’t produce as much energy, but anaerobic organisms require less energy.

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14
Q

What are alternate oxidants used in the biosphere?

A

• NO3-, -MnO2, -Fe(OH)3, -SO42-, CO2
• (In decreasing order of energy produced)
• These are catalyzed by microorganisms

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15
Q

What is pE?

A

• to catagorize the extent to which natural waters are chemically reducing in nature, environmental scientists use the concept pE

• Measure acidity in aqueous solutions, pE is defined as the negative logarithm of electron activity

• PE = -loga e

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16
Q

What does a large negative pE value indicate?

A

implies large electron activity in solution

‣ Reducing conditions
‣ Anoxic water bodies

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17
Q

What do large positive pE values indicate?

A

‣ Low electron activity in solution
‣ Oxidizing conditions
‣ Well aerated surface water

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18
Q

What occurs in a flooding event?

A

• Aerobes decrease
• Anaerobes increase
• PE decreases
• O2 decreases
• CH4 increases
• CO2 increases

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19
Q

What happens when oxygen is depleted?

A

• microbial populations first use oxidant that produces the most energy (O2) until it is depleated. Then another oxidant is used, where redox potential of a body of water tends to fall in stepwise pattern as Bioogical oxygen demndad (BOD) increases

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20
Q

What are the effects of microorganisms on the chemistry of water in nature

A

• CO2 to biomass by algae in sunlight
• Dead algal biomass degraded by bacteria
• CH2O degraded to CO2 by bacteria in the presence of O2
• Reduced forms of some elements are produced by bacteria in anaerobic conditions
‣ Ex. SO4 —> H2S

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21
Q

What are pE/pH diagrams?

A

• A two dimensional plot pE (y-axis) and pH (x-axis) to show water stability boundaries
• H2O has a limited range of pE and pH values within which it is stable
• Highly reducing conditions (low pE):
‣ 2H2O +2e- —> H2 + 2OH-
• highly oxidizing conditions (high pE)
‣ 6H2O —> 4H3O +O2 +4e-

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22
Q

How is pE related to mine wastes?

A

pH 2.5 and well aerated (pE=15)
• most important sulfur species in solution would be sulfate

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23
Q

How is pE related to swamps/paddy rice fields?

A

• soil has high content of organic matter (OM) which acts as a reducing agent
• Low pE
• Ex. H2S

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24
Q

What is the iron system?

A

Below pH 3, Fe3+ may exist in equilibrium with Fe2+. The boundary line : [Fe3+] = [Fe2+]. likewise depends on both pE and pH, but it does not depend on an assumed value for total soluble iron.

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25
What is a pollutant ?
• A pollutants is a substance or effect that adversely alters the environment by changing the growth rate of species, interferes with the food chain, is toxic, or interferes with health, comfort, amenities, or property values of people • The quality of the surface/ groundwater of concern with regard to human health & welfare and the heath of aquatic ecosystems • Inorganic pollutants can have natural OR anthropogenic sources ‣ Ex. The biggest mass poisoning that occurred in India/Bangladesh, arsenic poisoning
26
Inorganic vs organic pollutants?
• the most important difference between organic and inorganic pollutants: ‣ Inorganic pollutants have geologic origins ‣ Organic pollutants can be broken down by CO2 and water
27
What are the types of ubiqutious water pollutants?
• Industrial chemicals • Industrial products • Consumer products • Geogenic/natural chemicals • Disinfection/oxidation • Transformation products
28
Industrial chemicals as water pollutants
Drinking water contamination Solvents and intermediates
29
Industrial products as water pollutants
Lubricants, additives, flame retardants Problems with bio magnification and long range transport
30
Consumer products as water pollutants
‣ Detergents, pesticides, hormones, personal care products ‣ Ex. Antibiotics ‣ Problems with Endocrine transformations, feminization of fish, multitude of other effects
31
Biocides as water pollutants
‣ Pesticides ‣ Ex. DDT, atrazine ‣ effects primary producers
32
Geogenic/ natural chemicals as water pollutants
Heavy metals, inorganic, human hormones Lead, cadmium, mercury, arsenic, fluoride, etc Risks for human health and drinking water quality
33
Disinfection/oxidation as water pollutants
Disinfection by-products Drinking water quality, human heath problems
34
Transformation products
Metabolites Drinking water problems, bioaccumulation
35
What are DNAPL’s
• Dense non aqueous phase liquid • Density greater than 1g/ml (combines with ground water ) • Imiscible with water • Ex. Trichloroethylene (TCE)
36
What are TCE’s ?
Trichloroethylene (TCE) ‣ Used for rocket engine flushing/metal cleaning/degreasing of equipment/ electronics, and heavy machinery ‣ 1970: 80% of degreasers used TCE ‣ 1976: 42% of degreasers used TCE ‣ Jet engine testing equipment at a military site was cooled with TCE. The site is now used to study the fate of TCE that leaked into the fractured rock
37
What are LNAPL’s
• Light non aqueous phase liquid • Sparingly solvable in water • Density is less than that of water (float on water) • Ex. Petroleum hydrocarbon pollution in groundwater ‣ Gas station leaks, spreading LNAPL into ground’s unsaturated zone. Due to being less dense than water, it rests on the saturated zone (water table) until it is volatilized.
38
What does a model of the subsurface contaminant plume’s microbial geochemistry look like?
• oil DNAPL spill —> methanogenesis —> sulphate reduction —> iron reduction —-> NO3 and Mn production ——> aerobic degradation
39
Organic chemicals in relation to fatty tissues
• This is because their fat solubility is greatly than their water solubility • 1-octanal is very similar in solubility to fat, so scientists use the octagon/water participial coefficient to determine log10Kow • The solubility of a compound termites how dangerous it is! • Log10Kow is a chemicals ability to enrich itself in cells (of fatty tissue normally) • DDT is so dangerous because it is hydrophobic, but it loves fat.
40
Bioconcentrations and water contaminants
• The tendency to bioaccumulate is expressed as a bioconcentration factor • Bioconcetration = ratio between [chemical] in organism : [chemical] in water • Almost the same as what log10Kow argues
41
What are the guidelines for Canadian drinking water quality?
* Maximum acceptable concentration (MAC) in mg/l (pH 6.5-8.5) * Has established arsenic, cadmium and chromium as carcinogenic * Low MACs for cadmium, arsenic, lead, chromium and mercury indicate that a small amount of the pollutant can have adverse affects on large quantities of water
42
What is sewage sludge?
Can be found in water treatment plants along side the treated water * Disposal at sea, landfills, incineration or soil amendment * Contains nutrients but also environmental pollutants ◦ Soil amendment: products, usually meaning organic matter, added to the soil to improve the soil condition
43
What are some of the toxic contents of sewage sludge? How can it be filtered?
◦ Giardia lambilia ◦ Pathogenic microorganisms ◦ DDT and DDD present ◦ Cryptosporidium parvium (gives you the shits) ‣ Filtration and disinfection ◦ Must remove or inactivate 99.9% of giardia lamblia and 99% of all viruses
44
What is coal combustion fly ash (CFA)?
◦ By product of burning coal at electric utility plants ◦ Magnitude is the issue ◦ Consists primarily of metals, and Si, Al, Fe, and CaO In 2011: US power plants produced 130 million tons of CFA ◦ Chemical composition of CFA depends on the composition of coal and combustion process ‣ Burning the same coal can result in CFA with different morphologies depending on combustion technology ‣ Potential for leaching of metals depends on crystallinity (glasshouse or crystalline phase) ‣ Glasshouse phase: metals leach at much lower rate
45
What is CFA used for?
‣ US = 68% of CFA goes to landfills ‣ 32% is used for: ◦ Cement production ◦ Structural fills/embankments ◦ Stabilization of waste materials ◦ Road base/ sub base materials ◦ Grouting miles ◦ Mineral filler in asphalt paving
46
What is the “dead zone” in the Gulf of Mexico? Why has it formed?
◦ 18,000 km^2 area where O2 concentration is too low to support aquatic life ◦ Caused by fertilizer runoff into the Mississippi ◦ Due to nutrient enrichment from land use activities in teh drainage basin of the Mississippi ◦ We need to cut the amounts of nitrogen and phosphorous by at least 45% to shrink the dead zone ◦ The number of dead zones increased from 46 (1995) to 400 (2008) ◦ Not all dead zones are next to the ocean, can be done through precipitation
47
How do natural disasters contribute to environmental contamination?
‣ causes environmental contamination ‣ Hurricane Katrina causing oil spills, lead and fecal spreading
48
How do chemical disasters contribute to environmental contamination?
‣ Since WW1 ◦ 1) accidents with sudden catastrophic * Ex. Ammonia, arsenic, dioxins * Methyl isocyanate ◦ Worlds worst industrial disaster: ◦ Occurred in Bhopal/India 1984 ◦ 40 tins of CH3NCO released when water entered a storage tank. An exothermic reaction occurred, causing pressure to rise, leading to a rupturable disk burst. As a result, gas was released and instantly killed 5295 people, and fatally complicated 10,000 people (who eventually died of complications form cyanide lesions ◦ 2)direct contamination of food and drinking water. * Health problems over days or weeks ◦ 3) insidious contamination of food chain/water supply * Health problems over months/ years
49
What are point sources?
‣ Point sources ◦ Landfills ◦ Underground storage tanks ◦ Septic systems ◦ Factories, industrial, military installations ◦ Snow dumps * Inorganic contamination in soils at a snow dump: * Cl, cu, lead, arsenic
50
What are non point sources?
‣ non point sources: ◦ Agricultural fertilizer ◦ Pesticide applications ◦ Road De-icing salts ◦ Emissions from vehicles * a much harder problem to solve
51
What did the 3rd national report on human exposure to environmental chemicals find?
About 40 organic pollutants and 10 metals are detected in human blood
52
can you give an example of when life was powered by redox equations?
respiration and photosynthesis : Sun + CO2 + H2O <---> CH2O +O2
53
What major processes does soil have a role in? Why?
‣ global carbon (organic matter decomposition) ‣ Global nitrogen (nitrifictaion and denitrofication) ‣ Phosphorus and sulphur cycle
54
What are the soil horizons?
O - organic (humus) A - Topsoil (minerals & humus) E- Evulvian (leached minerals and tonic matter) B - subsoil c - parent rock R - bedrock
55
To what is soil reactivity dependant?
Rely on particle size Soils react much more readily with environmental agents than rocks Reactive soils are those that swell on wetting and shrink on drying (clays)
56
What are the key clay minerals?
Kaolinite Illite Montmorillonite
57
What are the characteristics of clays?
• (Aluminosilicatesare some of the most important/ubiquitous minerals • Natural water barrier and used as landfill liners • Constitute a large component of soils • Are important in interaction between inorganic and organics • Form sheet-like structure
58
What is kaolinite ?
◦ Two layer clay ◦ Each sheet made up of Si-O tetrahedra attached to one side of an Al-O octahedral shee to to form a 1:1 layer
59
What is illite?
Non expanding, clay sized, dioctehedral, micaceaous minerlas
60
What is montmorillonite?
◦ An Al sheet sandwiched between two Si sheets ◦ Negative change due to isomorphous substitution of Al for for Si atoms Fe(II) and Mg (II) for Al ◦ The negative charge is located in the interior of the layer ◦ The cations that balance this negative changer are loosely held at the surface, making them exchangeable. ◦ This large cation exchange capacity means that it can bind wth water and swell. Important for agricultural soils
61
What are the ways soils are formed?
Weathering (physical, chemical) Hydrolysis Complexation Oxidation and reduction
62
How does weathering contribute contribute to the formation of the mineral matter of soil?
When rocks are weathered (physical, chemical) and results in the production of mine materials (soils)
63
How does hydrolysis contribute contribute to the formation of the mineral matter of soil? ?
◦ Hydrolysis is a general term for the processes in which water is an essential reactant. • Agents of weathering: ◦ Kaolinite, gibbsite, silicic acid
64
How does complexation contribute to contribute to the formation of the mineral matter of soil? ?
• iron and aluminum are insoluable hydroxides but have substantial solubilization in soil due to the formation of solvable organic complexes (from soil organic matter)
65
How do oxidation and reduction contribute to the formation of the mineral matter of soil?
• Primary minerals contain elements in low oxidation states. When these minerals are exposed to air, the oxidation state increases and disturbs the charge balance. This results in the loss of other elements as the mineral tries to maintain neutrality (secondary mineral production) ◦ Oxidiation of iron in biotite produces the clay mineral vermiculite and potassium is lost
66
How is the organic component of soil formed?
Physical decay —-> chemical decay ——> soil production Primacy sources being Poland tissues in various takes of decay due to chemical/microbial processes The top 15cm of soil contains up to 5% of microorganisms + worms.
67
The processes of genesis of ______ and ____ components of the soil are consider separately
Organic and inorganic
68
What are capillary forces?
Holds water in micropores between and inside soil particles
69
How are soil horizons formed?
Rain water percolates through the soil, and carries solvable and colloidal material lower into the soil. This results in the banded lays that create soil stratification
70
What are the properties of soils?
Physical properties: - texture, particle size, permeability Chemical properties: - total elements, organic matter, available elements, cation exchange capacity, soil pH
71
What are the environmental issues associated with soils?
Metal contamination (acid mine drainage) Salinity Acidification Nutrient leaching Soil erosion
72
What does particle size entail as a soil property?
Soil is made up of particles with differing chemical compositions and sizes, which can then be divided into categories based on particle size Clay, silt, sand, gravel Sand has good drainage (poor water retention) and is readily aerated
73
What is the difference between clay minerals and clay sized particles?
Clay minerals are: kaolinite, montmorillonite Particle may be composed of clay minerals, organic matter, or other minerals
74
What does texture entail as a soil property?
Collective term that defines soil by the portions of particle sizes it contains
75
What does permeability entail as a soil property?
Measure of the ability of a soil to conduct the flow of water
76
What is the most common mineral composition of soils? (Generally)
Silicon — 30-40% Aluminum — 2.4-7.4 Iron Titanium Calcium Magnesium Potassium Sodium
77
What is organic matter as a soil property?
Plays an important role in Usually decreases with depth Composed of humic and non humic material (polysaccharides, cellulose, hemicellulose, pectin) Temperature agricultural soils have the most organic matter (1-5%)
78
What is elemental availability as a soil property?
If soil is deficient in essential elementals, our food produced will be elementally deficient The availability/extractability of essential nutrients is important
79
What is the cation exchange capacity as a soil property?
A measure of how many cations can be retain on soil particle surfaces Influences a soils ability to hold onto essential nutrient and provides a buffer against soil acidification Most important cations: ca, mg, k, na Hydronium ions pose a potential problem (making soils more acidic)
80
How do we calculate base saturation?
Number of exchange sites occupied by Ca, Mg, k,Na Divided by Total number of exchange sites Large base saturations are desirable (soils with low CEC or BS are susceptible to acidification)
81
What is soil pH as a soil property?
Soils rich in carbonate minerals, as wells also soils with large amounts of humic matter tend to be acidic . Acidity arises from microbial decomposition of organic matter Soil ph is also affected by the redox status of the soil As H3O is consumed, ph rises. Flooded soils tend to have a higher pH than their upland counterparts
82
How is soil erosion considered an environmental issue?
Ex. The corn belt (mid US) averages 25t/hectare loss in topsoil each year Perturbs the global carbon cycle Too little or too UCS water affects soil productivity
83
How is nutrient leaching considered an environmental issue? What determines the extent of leaching?
The downward movement of dissolved nutrients down the soil profile by percolating water Extent of leaching determined by the flux of water, soil texture, naturalness of plant cover Chemically inhibited by CEC of soil and physically through plant uptake Soils with high CEC hold cations and prevent leaching
84
How is acidifaction considered an environmental issue?
Soil acidification is the buildup of hydrogen cations which reduces the soils pH, happens when a proton donor is added to the soil. Accumulation of acids faster than they can be neutralized
85
How is soil salinity considered an environmental issue?
Refers to the salt content in the soil Saltination of the soil can be caused by mineral weathering or gradual withdrawal from the ocean Affects plant development
86
How is soil metal contamination considered an environmental issue?
Metal ions can accumulate in teh soil under certain environmental circumstances; ore deposits (mining), human activities Lead, arsenic, cadmium, mercury are persist at and toxic in the environment, and can accumulate in the soil over time
87
What is acid mine drainage?
The formation and movement of highly acidic water rich in heavy metals Occurs when rainwater seeps through a mine or mine wastes and carries sulphuric acids into nearby streams and groundwater

Chem 321 (6 decks)

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