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HDSO Environmental Chemistry > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

Why are small particles important

A
  • more mobile
  • nano properties
  • surface area is much larger
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2
Q

Dissolved versus Particulate

A
  • operational definition - dissolved passes through 0.45um filter
  • larger are particulate
  • deposit particles as the velocity of water decreases
  • aqueous will continue downstream
  • nanoparticles are 1-100 nm
  • by the filter definition nanoparticles are dissolved
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3
Q

Specific surface area

A
  • normalized to per unit mass (m2/g)
  • can use density and cube shape to find the surface area
  • 1 g/mL is 6 cm2/g
  • 10-4 cm cubes = 1 um per side
  • 1012 particles * 6 x 10-8 per particle = 60,000 cm2/g or 6 m2/g
  • actually greater SA because rough edges will increase SA
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4
Q

Colloids

A
  • particles diameter between 10 nm - 10 um
    • falls under 0.45 um filter
    • also in range of nanoparticles
  • larger particles settle and smaller particles suspend in solution
  • stokes law accounts for density to determine suspention
  • colloids suspend indefinitely
  • sand 20um - 2mm
  • silt 2-20 um
  • clay < 2um
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5
Q

Adsorption

A
  • electrostatic attraction of a species to a surface
    • reversible
    • if irreversible (covalent) then called specific adsorption
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6
Q

Absorption

A
  • allows for internalization of an attracted species. Not just a surface
  • sorption allows for adsorption AND absorption
  • nonpolar solute may attach to nonpolar area of OM
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7
Q

Ion exchange and binding affinity

A
  • Na+ < K+ < Mg2+ < Ca2+
  • binding and releasing equilibrium
  • ion chromatography - ion mixture passes through a -COOH rich column
  • Ca2+ will have the longest retention time
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8
Q

Clay

A
  • aluminosilicates, oxides of Al and Si in lattice with occasional transition metals
  • Kaolinite - 2 layer clay
  • Montmorillonite - 3 layers
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9
Q

Clay surface charge

A
  • isomorphous substitution - different charge metal substitutes for a metal in the lattice
  • results in a new charge that is not balanced
  • can also occur due to terminal -OH groups
    • can become positive or negative
    • Si pulls in e- density and weakens OH bond
      • net negative charge
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10
Q

Environmental Materials

A
  • Fe and Al oxides
    • Iron oxyhydroxides Fe(O)OH
      • at interface of aerobic and anaerobic
    • Alumina Al2O3
    • terminal groups with variable charge depending on pH
  • Organic matter
    • -COOH, NH2, phenol
    • ionization dependent on pH
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11
Q

Point of Zero Charge

A
  • function of pH when the surface is net neutral
  • pHo or pHzpc
  • pH > pHo then negative
  • pH < pHo then positive
  • Glassware in the lab - pHo = 2
    • when analyzing metal, it will complex to the sides
    • rinse with nitric acid to protonate the surface
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12
Q

ICP-MS

A
  • sample becomes aerosol due to glass nebullizer
    • must be acidified
  • glass torch 5000K Ar plasma
  • M+ then Ms
  • Metal samples stored in plastic with hydrophobic surfaces
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13
Q

Salt effect on pH in storm water ponds

A
  • urban soil (background soil) and bioretention soil (artificial)
  • pH of storm water is 7 because CO32- in concrete increases pH
  • emphasize pH, major ions, Zn2+
  • Important to note that H+ can bond to the surface
  • salt effects pH because it displaces H+. pH decreases
    • without salt - water is OH- and H+. OH- wash out and H+ sticks
    • return to pH 7
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14
Q

leachate

A

water that has infiltrated through the soil

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15
Q

Salt effect on trace metals in stormwater soil

A
  • Mg in water increases as the salt displaces it in the soil. More becomes free ions in the water
  • No salt - Mg binds to the soil again and the water conc decreases
  • Sometimes all of the Mg will run off and the graph will have a distinct spike
  • Ca2+ causes Mg to decrease (zero) before Na because it is more aggressive at replacing Mg
  • One Mg can be replaced with 2 Na
    • Na2Surface + Ca2+ = Ca-Surface + 2Na+
  • important because plants need Mg
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16
Q

Cation Exchange Capacity

A
  • cations can be attracted to positively charged sites on variably chraged soil particles
  • measured in mol/kg of soil
  • Na < K < Mg < Ca
  • reversible attractions
  • high conc of a low affinity can displace high affinity ions
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17
Q

Binding series of ions

A
  • Salt added (high Na+) and displaces Ca, K, Mg. Sodium rich soils
    • Na2Surface + Ca2+ = Ca-Surface + 2Na+
    • wash away aq. ions that were displaced
    • less competition for binding sites
  • Transition metals displace Na+
  • Ca salt added and greater competition displaces transition metals
  • leach metals into the water
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18
Q

Zinc in soil

A
  • articifial soils highly subject to cation-induced leaching of Zn
    • Ca > Na
  • Less leaching of Cu and Pb
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19
Q

Quantitative Treatment of Sorption

A
  • Aqueous concentration - Caq
  • Sorbed concentration on a solid material - Cs
  • models have assumptions
  • show molecular level interactions
  • sorbtion isotherms are only valid for a given temperature
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20
Q

Langmuir Model

A
  • assumes finite number of binding sites that can interact with aq species
  • assume all binding sites are equivalent (same binding energy)
  • similar to enzyme kinetics of Michaelis Menten
  • Cs/Caq = b*Csm / (1+b*Caq)
    • b is the Langmuir binding constant
    • Csm is the sorption capacity - may relate to CEC
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21
Q

Linearize Langmuir

A

1/Cs = 1/Csm + (1/(b*Csm*Caq))

y = mx + b

y = 1/Cs

x = 1/Caq

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22
Q

Freudlich Model

A
  • empirical - just math model to fit data. no assumptions
  • Cs = Kf*Caqn
  • interpretations based on value of n
    • n = 1 then y int = 0 and linear
    • exponential when n > 1
      • possible when nonpolar org molecules bind and change the surface characteristics. Adds larger OM layer
      • attempt to decrease the nonpolar surface area in water
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23
Q

Freundlich linearized

A

log Cs = log Kf + n log Caq

y = mx + b

unitless values

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24
Q

Phosphorus Geochemistry

A
  • can be limiting nutrient for plant growth
    • Redfield Ratio 106:16:1 C:N:P
  • No chemical forms of P are unavailable for plants to use
    • different than N
  • Inorganic: PO4
  • Organic: ATP, DNA, phosphorylated proteins
  • Org P to PO4 (decomp) and PO4 to organic (assimilation)
  • PO4 is mined from minerals
  • Can be physically removed from the environment, but not chemically
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25
Q

Sources and problems from P

A
  • Anthropogenic sources: detergents to decrease water hardness, wastewater, agriculture
  • excess P leads to eutrophication - lack of O2
  • PO4 binds to + particles, on sediment at the bottom
    • requires geological time scale in order to return to original mined location
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26
Q

Decease P in Surface Water

A
  • ban P in detergents
  • wastewater treatment plants
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27
Q

PO4 and Fe oxides

A

Fe(O)OH is an iron oxyhydroxide

  • alternating redox conditions
  • anaerobic conditions promote dissolution of Fe(O)OH particles and release sorbed phosphate
  • Fe(O)OH to Fe2O3
  • Fe3+ from Fe(O)OH to Fe2+ that is aqueous
  • PO4 binds to Fe(O)OH when negative, dependent on pH and point of zero charge
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28
Q

Rock in water

A
  • red layer on the bottom of the sediment
  • O2 is available on the interface between the rock and the soil
  • Fe2+ comes up from the sediment to form Fe(O)OH then Fe2O5 (rust)
  • Fe2+ equil with Fe3+ but the production of 3+ is faster than the reduction to 2+ so 3+ accumulates
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29
Q

Lake Apopka

A
  • heavy ag area - lots of P applied
  • wetlands drained for ag - dig ditches to drop water level
    • must apply more P because some will stick to Fe3+
    • restore wetlands around the lake, increase water table
    • Fe3+ to Fe2+ and PO4 released
    • high P in the late
30
Q

River to Bay deposition of P

A
  • PO4 in aq or on particle
  • particles settle and over time become deeper and deeper in the sediment
  • becomes anaerobic and Fe3+ to Fe2+
  • PO4 off the particles and moves up into the water column
31
Q

Distribution Coefficients

A
  • describe partitioning of organic molecules between solid and aq phase
  • Kd = Cs / Caq or Cs = Kd * Caq
  • Kd is the slope
  • valid at low conc and when n = 1 in Freundlich
  • Cs is mineral matter (charged) and organic matter (nonpolar)
  • Cs = fomCom + fmmCmm
  • Cmm = 0 so Cs = fomCom
32
Q
  • KOM = COM / Caq
  • KOC = COC / Caq
  • OC is organic carbon and OM is organic matter
    • OM = 1.7 OC
  • Com = mol solute / kg OM and Coc = mol solute / kg OC
  • Coc > Com
  • Also Koc > Kom
  • Kd = fomKom therefore Kom > Kd
  • Kd is site specific and Kom is universal because it is the property of how the chemical interacts w/OM assuming OM behaves similar at all sites
A
33
Q

Kow

A
  • distribution coefficient for biological applications
  • measures distribution between octanol and water where octanol is analogous to animal lipids
  • Kow = Coct/Cw
  • Kow is very high for nonpolar molecules
  • below 1 for highly polar molecules
34
Q

Environmental partitioning

A
  • air
  • water
  • soil/sediment
  • biota
35
Q

Air

A
  • vapor pressure
  • intermolecular forces
  • molecular mass - london dispersion forces
  • high polarity will have low VP
36
Q

Water

A
  • aq solubility
  • Kow
  • Koc / Kom / Kd
37
Q

Soil/Sediment

A
  • ionic state
  • charge / pH
  • neutral nonpolar Kow /Kd
  • DOM % in soil
38
Q

Biota

A

based on lipid content

favorable for nonpolar

39
Q

DDT

A
  • ag and mosquito applications
  • egg shell thinning - offspring die before hatching
  • mimics estrogen
  • band due to eco effects and insect resistance
  • C-Cl bonds are very resistant to degradation, very long t1/2
40
Q

Persistent molecules

A
  • Organochlorides - DDT
  • PCB - polychlorinated biphenyls log Kow = 6
  • PBDE - polybrominated diphenyl ethers
41
Q

Accumulation of Persistent Chemicals

A
  • high conc compared to other media
  • nonpolar and persistent
  • bioconcentration - increase in conc in an organism compared to the abiotic environmental medium
  • bioaccumulation - bio conc including uptake via diet
  • biomagnification - accumulation along trophic levels
  • burden of chemical increases as it eats and increases up the food chain
42
Q

Global distillation

A
  • few molecules are energentic enough to go into the gas phase, but it happens slowly
  • follows the Maxwell Boltzman distribution
  • Industrial chemicals applied in warmer areas
  • decrease volatility in cold arctic air
  • chemicals accumulate in arctic water then to fish then seals then whales and polar bears
  • high conc in breastmilk for native woman
43
Q

Microbial processes

A
  • functional
  • transformations
  • element cycling
  • bacteria, algae, fungi, archae
44
Q

Organic Carbon as a contaminant

A
  • Biological Oxygen Demand (BOD)
  • amount of oxygen consumed in the microbial degradation of readily mineralizable organic matter in a water sample
    • measure as mg O2 per L sample
    • BOD < 1 mg/L is very low
    • BOD > 5 is high and contaminated with organic matter
    • Max )2 in water at 25C is 8 mg/L
  • Elevated OM depletes dissolved O2
  • most common cause of fish kills
45
Q

BOD levels

A

< 5 mg/L is stressful to sensitive species

< 2 mg/L is hypoxic

0 is anoxic

46
Q

Sources of BOD

A

Human waste

food waste

animal agriculture waste

Eutrophication - internally generated organic matter

47
Q

Sources of C

A
  • Autotrophs - inorganic C (CO2 or CO32- to CH2O)
  • heterotrophs - use CH2O that was generated somewhere else
48
Q

Aerobic microbes

A
  • when O2 is present
    • CH2O + water = CO2 + 4H+ + 4e-
    • O2 + 4 H3O + 4e + 6 H2O
    • the sum is aerobic respiration
    • ADP + P = ATP
49
Q

Respiration using N

A

2NO3 + 12H+ +10e = N2 + 18water (denitrification)

CH2O + water = CO2 + 4H+ + 4e-

less productive than aerobic respiration

50
Q

Fermentation

A

CH2P + 2H+ = CH3OH (reduction)

much lower delta G than N or O respiration

51
Q

Terminal Electron Acceptor Series

A

O2 > NO3 > CH2O > SO4 > CO2

  • CO2 becomes CH4 - methanogenesis
52
Q

summer time dead zones

A

higher temperatures have less O2 dissolved

microbes are slower in the winter and less algae and decomp occurs

53
Q

O2 maps of water

A
  • less O2 at depth because salty water at depth with fresh water on top. Gradient does not allow for great O2 diffusion to lower layers
  • org matter sinks and consumes O2
  • rainy spring washes in nutrients from ag
  • dry summer limits removal
54
Q

Chemical Oxygen Demand

A
  • utilize chemical oxidant instead of microbial oxidation
  • chromic acid: K2Cr2O7 strongly oxidizing
  • COD can oxidize more types of organic matter than BOD so typically the value is highing
  • Measured as TOC (total organic carbon)
  • BOD will oxidize the more mineralizable (to make inorganic) sources
55
Q

N cycling

A

N2

N2O -

NH3 / NH4+

NO3 -

NO2 -

56
Q

Nitrogen Gas

A

stable

triple bond

generally biologically unavailable

sink for N

N2 + O2 = 2NO = NO2 (nitrogen dioxide gas)

  • only occurs under heat in an industrial setting
57
Q

Nitrous Oxide

A

N2O

greenhouse gas in small amounts

very high heat retention that is 210 times that of CO2

laughing gas

58
Q

Ammonia and Ammonium

A

NH3 and NH4+

pH dependent

NH3 is toxic to aq organisms

sorption to soils when protonated

Highly soluble in water

NH4+ is highly available to plants

59
Q

Nitrate

A

NO3 -

very soluble

low sorption to soils

very mobile

highly available to plants

60
Q

Nitrate

A

NO2 -

intermediate

very soluble

low sorption

high motility

toxic to aq organisms at low conc

61
Q

Fixation

A

N2 = NH3

becomes bioavailable

reduction process

associated with roots of legumes

bacteria receive C source from roots

N2 + 3H2 = 2NH3

  • H2 from methane
  • industry fixation equals or exceeds natural fixation
62
Q

Nitrification

A

NH3 = NO3 -

oxidation

aerobic environments

large increase in motility

63
Q

Assimilation

A

NH3 and NO3 - to Organic N (immobilized)

  • reverse is decomposition mostly towards NH3

– amine groups in amino acid

64
Q

Denitrification

A
  • NO3- to No2- to N2O to N2
    • reduction via a microbe
    • CH2O to CO2 and water
    • uses N as a terminal electron acceptor
    • requires microbes, OM, and anaerobic
    • go from most mobile to N2 that leaves aq and terrestial environment (unavailable)
    • Produce N2 when forced to completion, when excess then only reach N2O
    • likely in wetlands
65
Q

Methemoglobinemia

A

blue baby syndrome

-in gut NO3- to NO2-

NO2- ligand to Fe on hemeglobin

adults have an enzyme to reverse the NO2-binding to Fe

66
Q

Riparian Zones

A
  • between terrestrial and aquatic systems
  • wetland environment
    • denitrification NO3- to N2 gas
    • limited diffusion of O2, OM, bacteria
  • goal is to intercept nutrient enrichment in water
67
Q

Processes to remove nitrogen (Riparian Zones)

A
  • Assimilation - NO2- and NH4+ to organic N
  • Infiltration into the ground water
    • sorption for NH4+
  • Denitrification - permenant sink of N
68
Q

Effect of Riparian Zones on Phosphorous

A
  • Assimilation - used as nutrient for biomass
  • no similar denitrification process
  • sorption dependent on pH
    • high pH0 will have a more + charge
    • Fe(O)OH
    • dependent on redox Fe(O)OH in aerobic and Fe2+ for anaerobic
    • accumulation of Fe3+
  • can be saturated
69
Q

P versus N in Riparian Zones

A

P only has temporary options

N has a permanent removal process

Short term the PO4 is held by sorption

Long term the vegatation uptakes PO4 for biomass

70
Q

Denitrification Potential Assay

A
  • Acetylene stops N2O to N2 by occupying the binding site on the enzyme
  • Chloramphenicol - bacteriostatic that inhibits protein synthesis
    • no new enzymes
  • optimized for max denitrification
  • N2O versus time graph in order to find rate
71
Q

Urban Stream Syndrome

A
  • increase impervious surface which increases fraction of runoff
  • decrease water infiltrating surface
  • large volume enters stream and increases velocity
  • erosive power that changes the shape of the stream
  • decreases Riparian function
  • lower ground water level - soils less saturated and more aerobic
  • higher OM near surface that becomes aerobic and denitrification decreases
  • more N enters surface water
72
Q

Stream Restoration

A

lower velocity

improve chemistry in soil

HDSO Environmental Chemistry (6 decks)

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