Exam 2 Flashcards Preview

Environmental Chemistry > Exam 2 > Flashcards

Flashcards in Exam 2 Deck (72):

Why are small particles important


  • more mobile
  • nano properties
  • surface area is much larger


Dissolved versus Particulate

  • 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


Specific surface area

  • 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



  • 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



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



  • 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


Ion exchange and binding affinity

  • 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



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


Clay surface charge

  • 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


Environmental Materials

  • 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


Point of Zero Charge

  • 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



  • 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


Salt effect on pH in storm water ponds

  • 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



water that has infiltrated through the soil


Salt effect on trace metals in stormwater soil

  • 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


Cation Exchange Capacity

  • 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


Binding series of ions

  • 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


Zinc in soil

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


Quantitative Treatment of Sorption


  • 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


Langmuir Model

  • 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


Linearize Langmuir

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

y = mx + b

y = 1/Cs

x = 1/Caq


Freudlich Model

  • 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


Freundlich linearized

log Cs = log Kf + n log Caq

y = mx + b

unitless values


Phosphorus Geochemistry

  • 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


Sources and problems from P

  • 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


Decease P in Surface Water

  • ban P in detergents
  • wastewater treatment plants


PO4 and Fe oxides

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


Rock in water

  • 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


Lake Apopka

  • 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


River to Bay deposition of P

  • 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


Distribution Coefficients

  • 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


  • 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




  • 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


Environmental partitioning

  • air
  • water
  • soil/sediment
  • biota



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



  • aq solubility
  • Kow
  • Koc / Kom / Kd



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



based on lipid content

favorable for nonpolar



  • 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


Persistent molecules

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


Accumulation of Persistent Chemicals

  • 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


Global distillation

  • 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


Microbial processes

  • functional
  • transformations
  • element cycling
  • bacteria, algae, fungi, archae


Organic Carbon as a contaminant

  • 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


BOD levels

< 5 mg/L is stressful to sensitive species

< 2 mg/L is hypoxic

0 is anoxic


Sources of BOD

Human waste

food waste

animal agriculture waste

Eutrophication - internally generated organic matter



Sources of C

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


Aerobic microbes


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


Respiration using N


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

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

less productive than aerobic respiration




CH2P + 2H+ = CH3OH (reduction)

much lower delta G than N or O respiration


Terminal Electron Acceptor Series

O2 > NO3 > CH2O > SO4 > CO2

- CO2 becomes CH4 - methanogenesis



summer time dead zones

higher temperatures have less O2 dissolved

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


O2 maps of water

  • 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


Chemical Oxygen Demand

  • 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


N cycling


N2O -

NH3 / NH4+

NO3 -

NO2 -


Nitrogen Gas


triple bond

generally biologically unavailable

sink for N

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

- only occurs under heat in an industrial setting


Nitrous Oxide


greenhouse gas in small amounts

very high heat retention that is 210 times that of CO2

laughing gas


Ammonia and Ammonium

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



NO3 -

very soluble

low sorption to soils

very mobile

highly available to plants



NO2 -


very soluble

low sorption

high motility

toxic to aq organisms at low conc




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



NH3 = NO3 -


aerobic environments

large increase in motility



NH3 and NO3 - to Organic N (immobilized)

- reverse is decomposition mostly towards NH3

-- amine groups in amino acid



  • 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



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


Riparian Zones

  • 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


Processes to remove nitrogen (Riparian Zones)

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


Effect of Riparian Zones on Phosphorous

  • 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


P versus N in Riparian Zones

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


Denitrification Potential Assay

  • 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


Urban Stream Syndrome

  • 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


Stream Restoration

lower velocity

improve chemistry in soil