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envs3238 > week 2 - inorganic contam > Flashcards

week 2 - inorganic contam Flashcards

1
Q

what are metals

A

lose electrons to form positive ions (cations), great electrical and heat conductivity.

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2
Q

what are non metals

A

gain electrons to form negative ions (anions). poor conductors of heat and electricity. tend to form acidic compounds and are brittle.

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3
Q

what are metalloids

A

exhibit both metallic and non metallic behaviour

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4
Q

what are examples of metalloids

A

arsenic and antimony

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5
Q

what general purpose screen for inorganics contam in soil or water include what elements

A

vanadium, chrominium, maganese, cobalt, nickel, copper, zinc, cadmium, tin, tunteen, mercury, thalium and lead

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6
Q

what does a Eh-pH (ORP) diagram help indicate metal in what

A

metal species in solution, what happens when conditions change and solubility/stability of species

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7
Q

what is EC

A

electrical conductivity, the ability of a material to conduct electrical current, using milliSiemens per cm (mS/cm)

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8
Q

what is DO

A

dissolved oxygen, the amount of gaseous oxygen dissolved in water, measured in milligram per litre (mg/L) = ppm or percentage of saturation

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9
Q

when do DO concentrations decrease

A

higher temperature, salinity and altitude

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10
Q

how does temperature affect elements in water

A

higher temperature increases reaction rates and increase the amount of a solid that can be dissolved

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11
Q

what do acidic conditions help

A

dissolve metals and keep them in solution

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12
Q

what do buffers do for pH

A

minimise changes or raise pH

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13
Q

what happens when you add the buffer superphosphate fertliser

A

it lowers pH, mobilising metals in solution then dissolves and raises pH and metal concentrations drop

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14
Q

where do contaminants reside in solid phase

A

within crystalline materials (silicates, oxides, carbonates and sulfates)
or
sorbed to mineral surfaces
or
onto organic compounds

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15
Q

where do contaminants reside in liquid phase

A

free phase and dissolved in pore water

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16
Q

what are the controls on reaction rates in soil

A

moisture, temperature, particle size and chemical speciation

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17
Q

what are colloids and what do they do

A

particles too small to naked eye but not dissolved, metals can be transported by absorbing into them.

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18
Q

what conditions can increase concentration of colloids

A

oxidising conditions and charge colloids can attract metals and continue flowing through pore water flow.

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19
Q

what are sequential extractions and why is it important

A

5 step extraction can show whether or not total metal values might be environmentall or biologically meaningful
1. exchangeable
2. carbonates
3. organics
4. sulfates and Fe-Mn oxides
5. silicate hosted metals

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20
Q

what are the drawbacks of sequential extractions

A

expensive and no single extraction is perfect because boundaries between the reservoids overlap

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21
Q

what is the most widely known sequential extraction

A

the 5 step method

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22
Q

what are the two leaching tests

A

batch and dynamic

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23
Q

what are the two most relevant leaching tests in Aus

A

toxicity chracteristics leaching procedure (TCLP) and australian standard leaching procedure (ASLP)

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24
Q

metals at contaminated sites can be ? (how can they transform)

A

transformed into insoluble or sparingly soluble forms, their mobility and environmental risk will be reduced

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25
Q

what are the 6 steps to classify waste

A
  1. is material special waste
  2. liquid
  3. pre classified
  4. hazardous
  5. determing wastes classification using chemical tests
  6. general solid waste
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26
Q

how to get rid of solid waste

A

contaminated soil/sediment can be removed and disposed in landfills, clean fill may be implaced

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27
Q

what problems can arise from removing contaminated sediment/soil

A

oxidisation, more soluble and bioavailable

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28
Q

how can solid waste be contained

A

impermeable capping and liners, compacted clay, geosynthetic liners

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29
Q

how can solid waste be stabilised

A

macroencapsulation using cement to mix with contaminated material over 1-2 weeks keeping it moist.

30
Q

what is silica microencapsulation

A

SME uses a metal silicate around contaminate to eliminate migration. can be used on mixed metals or hydrocarbon waste.

31
Q

solid waste fixation?

A

orthophosphate reacts with metals to form insoluble metal phosphate salts

32
Q

solid waste chemical fixation?

A

orthophosphate can be added as superphosphate and because its acidic, add a buffer such as magnesium carbonate. because SP is soluble it may help slow metal reactions

33
Q

what is a MEP

A

multiple extraction procedure which simulates 1000 years of leaching

34
Q

what is one method of bioremediation for solid waste

A

phytoextraction is the use of plants to extract and accumulate contaminants.

35
Q

what is phytostabilisation

A

works by not taking up contaminants but stabilises the ground causing less erosion, more roughness on the surface and reducing metal solubility.

36
Q

what is phytodegradation

A

degrades analytes as they are taken up and metabolised and can work with some organics such as pesticides, explosives, solvents and oils

37
Q

microbial remediation?

A

works for inorganics such as cyanide. solutions readily bond to gold and silver.

38
Q

how to treat water ex situ

A

coagulation/flocculation - additives to colloids such as aluminium sulfate reduce the negative surface charge allowing them to floc out.

settling/sedimentation - hydroclones use centrifugal accelation of water to spin grit to the side of chamber to settle and trap

39
Q

what else is in the water treatment train

A

filtration, ultra filtration (using membranes - forming semi permeable barrier to remove materials from water), adsorption (using activated carbon) and disinfection (UV treatment and chlorination to decrease microbial activity)

40
Q

what is permeable reactive barriers

A

a barrier with reactive filling contructed underground in the flow path of contaminated groundwater

41
Q

what does the barrier media have in PRB

A

filters particulates and has ion exchange characteristics that allow it to remediate soil water plume. usually iron, carbon or limestone and can be mixed with sand to promote flow through

42
Q

when are sequences barriers used

A

for mainly hydrocarbons

43
Q

what reactive media used in PRB

A

granulated activated carbon, processed to increase surface area, granulated to keep permeability reasonable and prevent clogging of precipitates.

44
Q

what is zero valent iron and when is it used

A

iron powder. It reduces and precipitates metals as it provides electrons (makes it negatively charged) to the contaminant for degradation. Used as ex situ water treatment

45
Q

what is zero valent iron used for

A

soprtion of metals by reduction and precipitates metals of oxidised species

46
Q

what environments help dissolve metals

A

acidic and oxidising environments.

47
Q

what is a EC measurement used for

A

estimate the salt content in a sample

48
Q

what are the controls on reaction rates in soil for contaminants

A

moisture, temperature, particle size and chemical speciation

49
Q

what general screen for inorganic contaminants in soil

A

chromium, manganese, nickel, copper, zinc, arsenic, cadmium, mercury and lead

50
Q

what general screen for inorganic contaminants in water

A

chromium, nickel, copper, zinc, arsenic, cadmium, mercury and lead

51
Q

how can you remove exchangeables in soil/sediment

A

removed by deionised water rinse or acidic chelating agent

52
Q

how can you extract carbonates

A

moderate acid such as HCI

53
Q

how can you extract sulfates and Fe-Mn oxides

A

nitric acid or aqua regia to help break bonds because they hold metals tightly

54
Q

how can you extract silicate hosted metals

A

need really strong acids to break down (hydrofluoric acid), but some minerals wont break down such as chromite.

55
Q

what are the cons of sequential extraction

A

expensive, no single extraction procedure is perfect because of the boundaries between the reservoirs overlap.

56
Q

why is a leachability test important

A

because contaminants in soil can leach into groundwater

57
Q

what are water quality probes measuring

A

pH, ORP (Eh), EC, DO and temperature

58
Q

what are the NEPM guidelines investigation and screening levels meant for

A
  • provide the concentrations of a contaminant above which further investigation and evaluation is required
  • applicably in the first stage of a site assessment
  • use a CSM
  • intended to help assess contam and to trigger site specific risk based approach or risk managment
59
Q

what are the HIL

A

health investigation level:
exceeding a HIL means further investigation is required not that risk is present.
it was developed for a broad range of metals and organics in soil
its applicable for assessing human health risk

60
Q

what is phytoextraction

A

used for solid waste such as metals and arsenic in the vadose zone by using plants to extract and accumulate contaminants. g

61
Q

what is a method for inorganics such as cyanide

A

microbial, cyanide bonds readily bond to gold, silver etc. and commonly applied to vats or piles of crushed ore to heap leach precious metals.

gentle fertilisation and stimulation of microbes can break cyanide.

62
Q

what can be used on industrial sites for ex situ water treatment

A

settling/sedimentation using a hydrocyclone which removes particulates by centrifugal forcing.

63
Q

what are the pros to PRB

A

low cost, energy, maintenance, supervision, power, no dewatering and can work for years. can be <5 m long to 100s m long

64
Q

what is a technique of PRB in situ for water

A

the fence or hanging wall where the waste at the surface contaminants groundwater and it flows through the wall to be treated.

65
Q

what is a technique of PRB in situ for water

A

funnel and gate, which direct the flow of water towards cages that contain the reactive media (gate)

66
Q

when do you use sequences barriers of PRB

A

with hydrocarbons where several treatments are required eg;

nutrient removal followed by reductive dissolution of chlorinated organics (using sawdust, sand to remove nitrate and then using the ZVI to dissolve trichloroethene

67
Q

what are some reactive media for water treatment in situ

A

carbon, zeolites and organics. GAC is largely used to remove metals and organics from water

Zero valent iron (ZVI) is used to sorb metals and reductive dissolution of organics.

68
Q

what is braggs law

A

describes the principles of XRF - The angle of the incoming radiation with respect to the crystal lattice
controls the direction and intensity of the diffracted radiation.

69
Q

what is the term for disordered solids that are difficult to identify or impossible using XRF

A

amorphous

70
Q

what is the preparation for using XRF

A

<10um size crystals of the sample material are grounded down using a mortar and pestle or McCrane mill

71
Q
A

envs3238 (7 decks)

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