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EESC456 > 15. Pollution > Flashcards

15. Pollution Flashcards

1
Q

3 types of organic contaminants

A
  1. industrial organics
  2. hydrocarbons (petro-chemicals)
  3. Pesticides
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2
Q

4 types of pesticides

A
  1. insecticides
  2. fungicides
  3. herbicides
  4. nematocides
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3
Q

6 solutions for organic contaminants

A
  1. excavate + remove soil
  2. phytoremediation
  3. bioremediation
  4. green waste compost
  5. soil washing
  6. in-situ oxidation: soil vapour extraction
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4
Q

Phytoremediation

A

use plants that take up contaminants, using plants in bioremediation

a. phytoextraction (remove As + Se):
accumulate chemicals, hyperaccumulators

b. phytostabilisation (phytoexclusion) (metals + As):
tying chemicals up in soils, any kind of plant cover is grown in order to stabilize the contaminant and reduce its movement into the wider environment

c. rhizodegradation of organic pollutants:
enhanced break down activities close to root system (rhizosphere), plants feeding sugars in soil for microbes that will breakdown contaminants

d. rhizodegradation (rhizofiltration) + phytodegradation of organics in constructed wetlands:
artificial pond + series of vegetation treated water so when gets to bottom of system = clean

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5
Q

Bioremediation

A

microbes degrading contaminants
technology uses enhanced plant and/or microbial action to degrade organic contaminants into harmless metabolic products

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6
Q

application of green waste compost: increases the…

A

availability of metals to plants

mixing soil with o.m./compost + heat = accelerated biogeochemical processes

high- temperature compost mixed and aerated by a special compost- turning machine in order to accelerate the breakdown of organic compounds. = accelerated degradation of organic pollutants in soil material excavated from a contaminated site, mixed with decomposable organic materials, and made into windrows.

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7
Q

Toxic inorganic substances (heavy metals) sources

A

burning fossil fuels
smelting
gasoline additives
wood preservatives
insecticides
heavy metals in sewage sludge from industrial water treatments
other processing techniques release elements in the atmosphere + deposited on vegetation/carried through rain and snow/global drift, accumulating in soils + going through food chain (ingested by humans)

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8
Q

Toxic inorganic substances (heavy metals) examples

A

Arsenic (wood preservative + insecticide + defoliant)

Lead, nickel, boron (gas additives) lead: lead-batteries
boron: detergents, fertilizers, forest fire retardants

cadmium, copper, manganese, nickel, zinc (soil amendments-phosphate fertilizer+limestone)
Cadmium: plating metals, rechargeable batteries.

ALL = specific organic substances +domestic/industrial sewage sludge.

Mercury: gold mining, chemical manufacturing industries, burning coal.

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9
Q

3 solutions for soil contamination by toxic inorganic compounds

A
  1. Eliminate/greatly reduce soil application of toxins (prevention)
  2. Immobilize toxin (soil mgmt so it doesn’t move into food/water supplies)
  3. Remove toxin by chemical, physical, biological remediation (for localized contamination)
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10
Q

Hyperaccumulator plants

A

Plants taking up and accumulating high concentration of metals

–> pose serious health hazard if eaten by animals/people. should harvest/bury or treated

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11
Q

2 types of landfills

A
  1. Natural Attenuation Landfills
  2. Containment/Secured Landfills
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12
Q

Natural attenuation landfills (for mild contamination)

A

letting nature slowly breakdown

soil ecosystem may be able to destroy the contaminant and heal itself, unaided, by the process of natural attenuation, may allow the soil ecosystem to recover its function and diversity over a reasonable period using any or all 8 processes

chemicals leaching to bottom of landfill:
monitoring well–> contaminants not in local groundwater

Vegetative cover (daily + final) so evaporates rain back into atmosphere (no percolation to pit because it would ass to leaching, helping contaminants getting to the bottom)

Methane recovery systems to collect gas from decomposition

–> contamination may be so serious that natural attenuation will occur too slowly to be a practical solution and more active technological interventions may be called for.

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13
Q

soil requirements for final cover (landfill cap)

A

Topsoil for vegetation (evaporates water + supports vegetation cover)
Sand layer for drainage (allows for lateral movement of water, guiding water horizontally over clay, off landfill)
Clay layer for sealing (prevents infiltration of water, minimizing leaching)

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14
Q

Containment landfills

A

designed to collect all leachate + pump it out for storage and treatment

landfill bottom is sealed with waterproof geomembrane (protected by covering of geotextile + gravel)
–> smectite clay (seals)
–>plastic geotextile (industrial)

Gravel around pipes so leachate flows easily into them

Cap/cover to keep water out of the pit

–>construction and function are much less dependent on the nature of the soils at the site.

–> The principal soil-related concerns are the requirement for suitable sources of sand and gravel, of soil for daily cover, for clayey material to form the final cover, and for topsoil to support protective vegetation.

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15
Q

3 major conclusions about soils in relation to environmental quality

A
  1. soils = valuable resources–>should be protected from environmental contamination (especially that which does permanent damage)
  2. Soils = promising mechanisms for disposal + processing + utilization of wastes (otherwise would contaminate enviro.)
    –> soils = vastness and remarkable capacities to absorb, bind, and break down added materials
    –> using soil ecosystem to digest/recycle materials
  3. soil contaminants + breakdown products can be toxic to humans/animals (go into food chain)
    –>ingested
    –>moving from soil into plants, soil fauna, air, water supplies
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16
Q

Most promising advances: bioremediation: biological processes of the soil harnessed to effect soil cleanup BUT must know:

A

a. chemical properties (Kd, Koc, solubility, adsoprtion, density)
b. soil properties (depth, clay, O.M. content, hydraulic properties–how readily water flows through soil)
c. climate (leaching pulse, rain vs dry)
d. depth to groundwater (space for contaminants to move?)
e. aquifer properties (how quickly water moves through aquifers, if contaminated = BAD)
f. knowledge of bacterias, fungi, plants (which contaminants they can breakdown, how much, etc.)

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17
Q

4 types of plant responses to metal contamination

A
  1. sensitive: accumulate metals, but no tolerance for high levels
    –> show immediate signs of toxicity
  2. indicator (of soil metal concentrations):
    steadily take up the metal in proportion to how much is available in the soil, tolerate moderately high levels of metal . sequestering the metal nonsensitive plant parts or by binding the metals in organic compounds that reduce the toxicity.

–> bioremediation: phytostabilization

  1. Excluder:
    does not pick up contaminants, survive despite it
    can tolerate quite high levels of metal contamination, may exhibit a high bioconcen- tration factor in the root (BCF root > 1), but not in the shoot (BCF shoot = 1). useful in stabilizing the metal in the soil, but does not facilitate the removal of the metal altogether.
    –> bioremediation: phytostabilization
    –> rhizosphere remediation
  2. Hyperaccumulator:
    tolerate extremely high metal concentrations in soils, efficiently extract the metal from the soil, translocate the metal to aboveground parts from their roots, and continue to grow unimpaired with ex- tremely high metal concentrations in their shoot tissues
    –> bioremediation : phytoextraction
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18
Q

Effects of pH on metal adsorption

A

different pH = different pH-dependent charges
–> free them up = higher CEC (more adsorbed)

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19
Q

In-situ bioremediation of soil/groundwater contaminated with volatile organic solvents:

A

adding nutrients, oxygen, cometabolites that improve soil enviro. for growth of native bacteria that can metabolize contaminant (stimulation of organic contaminant breakdown)

–> assume knowledge of groundwater system + microbes = complex, $$

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20
Q

6 types pollution

A
  1. spills
  2. industrial sites
  3. industrial/commercial properties
  4. agricultural lands
  5. brownfields
  6. organic/inorganic pollutants
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21
Q

8 important processes affecting the dissipation of organic
chemicals (OC) in soils

A
  1. Volatilization (soil to atmosphere)
    –> transfer process, OC remains intact
  2. Absorption
    –> transfer process, OC remains intact
  3. Leaching
    –> transfer process, OC remains intact
  4. Chemical decomposition
    –> altering o.c.
  5. Aerobic biological degradation
    –> destroy o.c.
  6. Anaerobic biological degradation
    –> destroy o.c.
  7. Runoff
    –> transfer process, OC remains intact
  8. Absorption + exudation
    –> transfer process, OC remains intact
    –> then = detoxication with plants

*Photo-decomposition (light + chemical rx)
–> alters o.c.

  • Capillary flow
    –> transfer process, OC remains intact

*Crop removal
–> transfer process, OC remains intact

and degradation by microorganisms, indicating that
these processes alter or destroy the organic chemical. In transfer processes, the
OC remains intact

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22
Q

Organic compounds (e.g. petroleum product or
pesticide) each have characteristic tendency to
adsorb to soil.

A
  • Kd (humus most important) + Koc
  • Low Kd or Koc indicates high leaching risk
  • Also a risk of bio-molecules being sorbed but still
    active
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23
Q

Distribution coefficient, Kd

A

(mass sorbed/kg soil) / (conc. chemical)

ratio between the sorbed and solution portions of the organic compound
–> indicates degree of sorption of organic compounds by soil colloids

The Kd for the adsorption of many nonpolar organic compounds on untreated clays = very low (clays =hydrophilic (water-loving), their adhering water films repel the hydrophobic, nonpolar organic compounds.

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24
Q

Koc

A
  • Koc = (mass adsorbed / mass of o.c.) / (initial conc.)
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25
Q

Risks of environmental pollution are higher with chemicals with greater…

A

persistence: net result of all their reactions, movements, and degradations

*how long remains in soil
–> PCBs; 2-10 years–> herbicides kill weed BUT high enviro. costs

26
Q

The effects of an insecticide on the soil fauna can be both direct and indirect:

A

Predators such as certain mites are often rapidly killed by a toxin, freeing their prey
populations, such as saprophytic collembolan, from the constraints of predation. Depending on
soil conditions and the persistence of the chemical, the time scale could be in days or months

27
Q

The specific environmental fate of each chemical will be determined at least in part by its particular …. (2)

A

chemical structure and properties.

28
Q

Soil organic matter and high-surface-area clays tend to be the …adsorbents for some compounds, while oxide coatings on soil particles strongly adsorb others. Everything else being equal, … organic molecules with … charged sites adsorb more strongly.

A

strongest

larger

many

29
Q

The degree to which an organic compound will be immobilized by adsorption to soil particles is determined largely by characteristics of both …

A

the chemical and the soil

30
Q

The tendency of organic chemicals to leach from soils is closely related to their…(2) Some compounds, such as chloroform and phenoxyacetic acid, are a million times more water soluble than others, such as DDT and PCBs, which are quite soluble in oil but not in water.

A

solubility in water and their potential for adsorption.
–>High water solubility favors leaching losses.

31
Q

…adsorbed molecules are not likely to move down the profile. Leaching is apt to be favored by …, the greatest leaching hazard occurring in …

Periods of …. around the time of application of the chemical promote both leaching and runoff losses.

….seem to be somewhat more mobile than most fungicides or insecticides, and therefore are more likely to find their way to groundwater supplies and streams, even when applied at normal rates

A

Strongly

highly permeable, sandy soils that are also low in organic matter.

water movement

high rainfall

herbicides

32
Q

Continued use of the same … on the same land can increase the rate of … of that pesticide.

Apparently, having a constant food source allows a … of those microbes equipped with the enzymes needed to break down the compound.

A

pesticide

microbial breakdown

population buildup
–> principle sometimes applied in environmental cleanup of toxic organic compounds, but the breakdown may become sufficiently rapid to reduce a compound’s effectiveness as a pesticide.

33
Q

Ex situ treatment

A

physical and/or chemical treatment of the soil by moving the soil to a treatment site (ex situ).

-excavating the soil to treatment containers (incinerated - high-temperature chemical decomposition)

-vacuum extraction or leaching (pushing or pulling air or water through the soil)

quite effective at destroying the contaminants
expensive ($ + energy)
site is highly disrupted
treated soil is destroyed as a living system (must be replaced or deposited in a landfill)

34
Q

In-situ treatments

A

physical and/or chemical treatment of the soil in place (in situ)

preferred if viable technologies are available.
The soil is left in place, thereby reducing excavation, treatment, and disposal costs and providing greater flexibility in future land use.
The contaminants are either removed from the soil (decontamination) or are sequestered (bound up) in the soil matrix (stabilized).
involves some of the same techniques of water flushing, leaching, vacuum extraction, and heating used in ex situ processes.

35
Q

Water washing treatments are not effective for oils and other nonpolar compounds that are repelled by water. To help remove such compounds, compounds called surfactants (similar to detergents) maybe sprayed onto the soil surface or injected into the soil.

A

As the surfactants move downward in the soil, they dissolve organic contaminants, which can then be pumped out of the soil as in the water washing systems.

36
Q

Surface soil horizons containing significant quantities of humus often exhibit a much …Kd because of the sorption of the organic contaminant into
the …. This is the reason that Koc is often a better measure of a compound’s tendency to become immobilized in various surface soils. Deeper soil layers, especially near and below the water table, generally contain little humus, and so have limited capacity to immobilize organic contaminants.

A

higher

organic matter coatings

37
Q

landfill filled to capacity = closed.

A

long-term management requires the application of soils’ knowledge at all stages.
→ final engineered soil cover+ installation of landscaping vegetation, to be maintained to prevent erosion, landslides, and exposure of wastes.
→ indefinite leachate treatment and monitoring of runoff and groundwater
→Gas collection and utilization will continue for decades.

closed landfill sites = opportunities for beneficial land uses. Limitations.
→ hazards for buildings: presence of leachate and landfill gases (from anaerobic decompo-methane)
→ land subsidence as the wastes inside the landfill settle and decay (slowest for organic waste components)- land surface typically settles by 25–30% of the thickness of the layers of compacted waste inside the finished landfill. = physical instability

38
Q

site with suitable soil characteristics is critical for a natural attenuation landfill.

A

-at least 1.5 m of soil material between the bottom of the landfill and the highest groundwater level.
–>should be only moderately permeable. If too permeable (sandy, gravelly, or highly structured), it will allow the leachate to pass through so quickly that little attenuation of contaminants will take place. If the soil is too impermeable, the leachate will build up, flood the landfill, and seep out laterally.

  • soil must have sufficient cation exchange capacity to adsorb , K+, Na+, Cd2+, Ni2+, other cations released from wastes

-soil should also adsorb and retard organic contaminants long enough to allow a high degree of microbial degradation.

-site should also provide soils suitable for daily and final cover materials.

39
Q

3 basic layers of the landfill cap.

A
  1. A compacted clay layer seal prevents infiltration of water so as to minimize formation of landfill leachate.
  2. A layer of loose, clean, medium sand was installed above the clay as a drainage layer to guide water horizontally over the clay and off the landfill cell to a collection pond
  3. On top, a layer of sandy loam Ap horizon material hauled in from a distant site serves as growing medium for the grassy vegetative cover that protects and stabilizes the landfill cap.
40
Q

Pit can reveal signs of in situ soil development and acid sulfate weathering in … horizons from unfortunate use of high …

A

2Bs
sulfide clay.

41
Q

Bioaugmentation

A

microbes specifically selected for their ability to degrade the contaminants are introduced into the polluted soil zone to augment the natural microbial populations

(mostly with native microorganisms)

42
Q

Biostimulation

A

use of technology that assists the naturally occurring microbial populations in breaking down chemicals

Once it is determined that organisms are present that are capable of metabolizing the contaminant, biostimulation techniques work to address one or more of four fundamental conditions limiting the effective rate of contaminant biodegradation:

a. Inaccessibility of the contaminant to the organisms that could degrade it. make contaminants accessible to bacterial degradation by desorbing mineral- bound contaminants or by dissolving hydrophilic contaminants in a way that allows bacteria to attach themselves to the molecules.

b.Lack of nutrients may restrict organism growth and metabolism. This is especially likely in low organic matter sandy soils and where the contaminant is a hydrocarbon such as a petroleum product. In these cases, adding fertilizer (especially nitrogen and phosphorus) in suitable form may greatly stimulate biodegradation rate

c. Electron donor substances (food) may be inadequate for rapid bacteria growth. In some cases, readily available energy sources such as molasses (for respiring organisms) or methane (for methanotrophs) have been added with success (see below).

d. Electron acceptor substances may be inadequate for effective metabolism. For aerobic breakdown, this situation may call for adding oxygen by pumping air into the contaminated soil or groundwater zone. For other organisms, pumping in nitrate may allow denitrifiers to degrade the compound.

43
Q

Compared to fine- textured soil with high clay contents and low permeability, ….. soils are much easier to bioremediation because their high permeability allows …. to be relatively easily pumped through the soil to the contaminated zone.

A

coarse-textured, sandy

nutrients and other additives

44
Q

In phytostabilization, plants provide several services: (4)

The main shortcoming of the phytostabilization approach is that the contaminant is….

A

(1) provide groundcover to reduce the movement of contaminated soil and dust by water and wind erosion;

(2) their transpiration reduces the amount of rainwater moving through the contaminated soil and thus also reduces the production of contaminated leachate;

(3) the plants may absorb the contaminant and sequester it in their root systems;

(4) the plant root may cause the precipitation of the contaminant in the rhizosphere.

not removed or destroyed, but remains in the soil.

45
Q

In enhanced rhizosphere phytoremediation, the plants do not take up the contaminant. Instead, the plant roots excrete substances that stimulate the… in the rhizosphere soil, speeding their …. Transpiration-driven movement of …to the enhanced rhizosphere zone improves the system’s effectiveness.

A

microbes

degradation of organic contaminants

water and dissolved contaminants

46
Q

enhanced rhizosphere phytodegradation: the plants do not take up the contaminant. Instead, the plant roots excrete into the soil … that serve as microbial substrates and growth regulators. These compounds stimulate the growth of the … that, in turn, degrade the organic contaminant. The transpiration of water by the plant causes soil water, with its load of dissolved contaminant molecules, to …, thus increasing the efficiency of the rhizosphere reactions.

A

carbon compounds

rhizosphere bacteria

move toward the roots

47
Q

Phytoremediation is particularly advantageous where …are contaminated with only …concentrations of organic pollutants located at ….depths in the soil. Phytoremediation causes little … and is relatively …, but also commonly takes a … to remove large quantities of contaminants than do the more costly engineering procedures.

A

large areas of land

moderate

shallow

site disturbance

inexpensive

longer time

48
Q

Unlike most organic contaminants, the inorganic toxins do not …; rather they usually ….

A

decompose and degrade

remain in the soil and so accumulate from year to year

–> In many places, the metal contamination is historical, resulting from polluting activities that are no longer practiced.

–> may leave a legacy of pollution in various soil layers, especially common in old urban areas where cycles of building, demolition, and rebuilding have occurred through centuries

49
Q

Irrespective of their sources, people everywhere are exposed to these toxic elements every day, either through the … or through…, Toxic metals can and do reach the soil by direct or indirect deposition, and from there they become part of the food chain: soil– plant–animal–human. Unfortunately, once the elements become part of this cycle, they may …

A

air

ingestion of food, water

accumulate in animal and human body tissue to toxic levels.

50
Q

Industrial sludges—or municipal sewage sludges from systems that treat both industrial and human wastes—commonly carry significant quantities of …that can have harmful environmental or human health effects. The sludge contaminants that have received the most attention are the …

A

inorganic as well as organic chemicals

heavy metals.

–> The domestic and industrial sewage sludges considered as nutrient sources can be important sources of potentially toxic chemicals.

51
Q

Many studies have suggested that if only moderate amounts of sludge are added, and the soil is not very …., these elements are generally bound by soil constituents; they do not then easily leach from the soil, nor are they readily available to plants.

Only in …soils have most studies shown significant movement down the profile from the layer of application of the sludge.

… and using judicious applications of lime have been widely recommended to prevent leaching into groundwater and minimize uptake by plants.

A

acid (pH > 6.5)

moderately to strongly acid

Monitoring soil acidity

52
Q

It is fortunate that most soil-applied heavy metals are not readily absorbed by plants and that they are not easily leached from the soil. However, the …of the metals means that they will … in soils if repeated sludge applications are made.

The uncertainties as to the nature of many of the organic chemicals found in the sludge, as well as the …of the metals problem, dictate continued caution in the regulations governing application of sludge to croplands.

A

immobility

accumulate

cumulative nature

–> Care must be taken not to add such large quantities that the capacity of the soil to react with a given element is exceeded. It is for this reason that regulations set maximum cumulative loading limits for each metal

–> Farmers must be assured that the levels of inorganic chemicals in sludge are not toxic to plants or to humans and other animals who consume the plants. For relatively low-metal municipal sludges, application at rates just high enough to supply needed nitrogen seems to be quite safe

53
Q

Liming of …reduces metal mobility; hence, regulations require that the pH of sludge-treated land be maintained at …

A

acid soils

6.5 or higher.

54
Q

Draining wet soils can be beneficial, since the … of the several toxic elements are generally …and ..available for plant uptake than are the reduced forms.

A

oxidized forms

less soluble

less

55
Q

Heavy phosphate applications may reduce the .. of metal cations such as lead that react with P to form insoluble compounds.

A

availability

56
Q

Application of organic matter, especially heavy applications of compost, generally ..the mobility and …of many of the inorganic toxins. The stabilized organic matter seems to strongly ..preventing their bioconcentration in plants.

A

reduces

bioavailability

adsorb many elements

–> That is, plants species differ in their ability to take up metals such that the contaminant may be many times more or many time less concentrated in the plant tissue than in the soil from which it was taken up.

57
Q

Bioconcentration factor

A

(mg/kg plant) / (mg/kg soil)

high bioconcentration factor (BCF) are likely to be more toxic to consuming organisms further up the food chain than plants with lower BCF values.

For example, contaminated urban gardens = the bioconcentration factor was much higher for lead than for arsenic and about 10 times as great for carrot as for lettuce or tomato. Amending the soil with very large amounts of biosolids and sawdust-based compost reduced the BCF by a modest but significant degree in most cases.

58
Q

Care should be taken in selecting food plants to be grown on metal-contaminated soil. Generally, plants translocate much …to their leaves than to their fruits or seeds. Root vegetables can also be problematic. Fruits or grains only rarely accumulate high concentration of metals. The greatest risk for food-chain contamination with metals is therefore through …, (2)

A

larger quantities of metals

leafy vegetables (spinach, lettuce) or forage crops eaten by livestock

59
Q

To be useful in remediating metal-contaminated soils by phytoextraction, a plant must not only take up large amounts of the metal, but must also …

A

translocate the metal to the aboveground plant parts for practical metal removal with plant harvest.

60
Q

In addition to manipulating soil pH and redox conditions, as already mentioned, organic materials, composts, and biochars of various kinds are being experimented with to enhance phytoremediation. One way these material increase plant metal uptake is by chelation. The natural materials or synthetic chelating agents can be applied to soils to enhance the removal of … by phytoremediation. Lead in soils is strongly bound by both …colloids and is thus only very sparingly available to plants. In a form of …, added chelates solubilize the lead, and plants are used to remove it.

A

lead and other metals

mineral and organic

enhanced rhizosphere bioremediation

61
Q

Encouraging an active soil faunal community may also play a role. Earthworms have been found to make lead more …from soils during bioremediation effort

A

easily taken up by plants and leached

EESC456 (11 decks)

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