Transcript Contaminant Hydrogeology V

Гидрогеология Загрязнений
и их Транспорт в
Окружающей Среде
Yoram Eckstein, Ph.D.
Fulbright Professor 2013/2014
Tomsk Polytechnic University
Tomsk, Russian Federation
Fall Semester 2013
Selected Topics in
Environmental
Chemistry
Acid Base Properties
• Water auto dissociates (self
dissociation)
– 2H2O ↔ H3O+(aq) + OH–(aq)
Kw = 1.01 x10‐14@ 25 °C
• Neutral water has a pH = 7.0
Acid Base Properties
• Amphiprotic (Brǿnsted acid or base )
- pH < 7 can be due to organic acids from
decaying organic matter
– (COOH)2 + H2O ↔ H3O+(aq) + COOHCOO–(aq)
Ka = 5.6 ×10‐2
- pH>7 can be due to soluble carbonates
from rocks and/or other sources
Redox Chemistry
in Natural Waters
Oxidation and reduction (Redox) reactions play an
important role in the geochemical processes that occur
in surface- and ground-water. Redox reactions are
defined as reactions in which electrons are transferred.
The species receiving electrons is reduced, that
donating electrons is oxidized. Redox reactions
determine the mobility of many inorganic compounds
as well as biologically important materials such as
nitrogen and sulfur. In addition, redox conditions
govern the particulars for the biological degradation of
complex hydrocarbon contaminants
Redox Chemistry
in Natural Waters
• Most important oxidizing agent in natural
waters is dissolved molecular oxygen
Half‐reaction in Acidic Solutions
O2+4H++4e-
2H2O
Half‐reaction in Basic Solutions
O2+2H2O+4e-
4OH-
Redox Chemistry
in Natural Waters
• [O2] in water is small
• Henry’s law ~ “The concentration of a gas in a liquid
at a specific temperature is proportional to the
partial pressure of the gas above the liquid”.
• The equilibrium constant for the gas/ liquid system
is given by Henry’s Law Constant KH
• O2(g)
O2(aq)
𝑲𝑯 =
KH = 1.3 x10‐3 mol L‐1 atm‐1
𝑶𝟐 𝒂𝒒
𝑷𝑶
𝟐 𝒈
REDOX Reactions
in Aquatic Environments
Many elements can exist in a number of oxidation states
in near-surface geologic environments, including the
macroelements C, N, O, S, Mn and Fe, and important
contaminants including As, Se, Cr, Hg, U, Mo, V, Sb, W, Cu,
Ag, and Pb. The oxidation state of these elements, in large
part, determines the speciation and biogeochemical fate
of these elements.
Generally, pH and Eh (pE) are considered the master
geochemical variables controlling the geochemical reactions
of elements in geologic and aquatic environments.
REDOX Reactions
in Aquatic Environments
Redox potential is a an intensity parameter of overall redox reaction
potential in the system (similar in concept to pH), not the capacity of
the system for specific oxidation or reduction reactions. The redox
value of standard half reactions (Eo) and details of how to calculate
redox capacity can be found in any elementary chemistry text.
The following inorganic oxidation reactions consume dissolved
oxygen in surface- or ground-water:
Sulfide Oxidation
2O2 + HS- = SO42- + H+
Iron Oxidation
O2 + 4Fe+2 + 4H+ = 4Fe3+ + 2H2O
Nitrification
2O2 + NH4+ = NO3- + 2H+ + H2O
Manganese (II) Oxidation O2 + 2Mn2+ + 2H2O = 2MnO2 + 4H+
Iron Sulfide Oxidation
15O2 + 4FeS2 + 14H2O = 4Fe(OH)3 + 8SO42- + 16H+
REDOX Reactions
in Aquatic Environments
The following redox reactions consume organic matter in surfaceor ground-water:
(1) Aerobic Degradation
CH2O + O2 = CO2 + H2O
(2) Denitrification
5CH2O + 4NO3- = 2N2 + 5HCO3- + H+ + 2H2O
(3) Manganese (IV) Reduction
(4) Ferric Iron Reduction
CH2O + 2MnO2 + 3H+ = 2Mn2+ + HCO3-+ 2H2O
CH2O + 4Fe(OH)3 + 7H+ = 4Fe2+ + HCO3- + 10H2O
(5) Sulfate Reduction
2CH2O + SO42- = HS- + 2HCO3- + H+
(6) Methane Fermentation
2CH2O + H2O = CH4 + HCO3- + H+
Redox Classification
of Natural Waters
 Oxic waters - waters that contain measurable dissolved
oxygen.
 Suboxic waters - waters that lack measurable oxygen
or sulfide, but do contain significant
dissolved iron (> ~0.1 mg L-1).
 Reducing waters (anoxic) - waters that contain both
dissolved iron and sulfide.
The Redox ladder
O2
Oxic
Post - oxic
Sulfidic
H 2O
Aerobes
NO3- Dinitrofiers
N2
MnO2 Maganese reducers
Mn2+
Fe(OH)3 Iron reducers
Fe2+
SO42- Sulfate reducers
H 2S
Methanic
CO2
CH4
Methanogens
H 2O
H2
The redox-couples are shown on each stair-step, where the
most energy is gained at the top step and the least at the bottom step.
(Gibb’s free energy becomes more positive going down the steps)
BOD and COD
BOD and
Aquatic
Ecosystems
Biochemical Oxygen Demand
(BOD)
 The capacity ofthe organic and biological matter in
a sample of natural water to consume oxygen
via catalytic processing of microorganisms
present
or
 The amount of oxygen required by aerobic microorganisms to decompose the organic matter in a sa
mple of water
 Easily determined by measuring O2
before and after sealing a water sample seeded
with bacteria
Chemical Oxygen Demand
(COD)
 Indirectly measures amount of oxygen needed to
decompose all organic substances (artificial
and natural) by using dichromate ion to
oxidize biological and organic matter in a
natural water sample
 Since stable organics, & anything that can be
oxidized are targeted too – so it has always
larger values than BOD
BOD and Aquatic Ecosystems
BOD and Aquatic
Ecosystems
Rate of the BOD decay in a stream
(typically 0.2/day)
d  BOD 
   K BOD  BODt 
dt
BODt  BODo  e
tkBOD
Anaerobic Decomposition of
Organic Matter
Anaerobic (O2 free) decomposition of organic
matter by microorganisms (fermentation) can
produce CH4 and CO2
2CH2 O
Bacteria
CH4 + CO2
organic matter
– In swamps the methane bubbles up to the surface
and may ignite
– In some rural communities (India, China), ‘digestor
units’ convert bio‐organic waste to methane
– Process can also occur in landfills
Anaerobic Decomposition of
Organic Matter
In lakes the lack of oxygen creates a reducing
environment at the bottom
• Insoluble Fe3+ (+e‐)
Soluble Fe2+
• Mixing does occur with seasons
Sulfur in Natural Waters
Hydrogen sulfide: Sources include, volcanoes, hot
springs, swamps (anaerobic bacteria), 10 – 15%
from anthropogenic sources (oil refinery, natural
gas wells, paper mills, ore smelting, etc)
Sulfur in Natural Waters
H2S Solubility
H2S + 2O2
H2SO4 4370 ml/L at 0 °C;
1860 ml/L at 40 °C
Some anaerobic bacteria can decompose various
sulfur containing organic matter (amino acids,
etc) and produce, amongst other things,
hydrogen sulfide, CH3SH, CH3SSCH3, etc.
2SO42-+3CH2O+4H+
2S+3CO2+5H2O
Overall reaction showing how some anaerobic bacteria
can use sulfate ion as the oxidizing agent to decompose
organic matter (important in seawater , where sulfate
concentration is much higher than fresh water
Acid Mine Drainage
(AMD)
“Outflow of acidic water
(pH<3.0) from abandoned
coal or metal/ore mines”
– Typically occurs when
certain geology is exposed
(mining, construction etc)
to water or air resulting in
the oxidation of these
minerals
FeS2 Pyrite
FeS2 Marcasite
FexSx Pyrrhotite
Cu2S Chalcocite
CuS Covellite
CuFeS2 Chalcopyrite
MoS2 Molybdenite
NiS Millerite
PbS Galena
ZnS Sphalerite
FeAsS Arsenopyrite
Acid Mine Drainage (AMD)
2FeS2 + 7O2 + 2H2O
4Fe2+ + O2+ 4H+
2Fe2+ + 3SO42- + 4H+
(I)
First step produces acidity
2H2O + 4Fe3+
(II)
Second step is usually slow, but can be catalyzed by acidic
bacteria, & consumes some of the H produced in (I)
4Fe3+ + 12H2O
4Fe(OH)3 + 12H+
(III)
3rd step the Fe3+ is soluble in high pH water initially produced;
however as AMD becomes more diluted the hydroxide
precipitates, giving the yellowish brown color (kills!!)
Acid Mine Drainage (AMD)
4FeS2 + 14Fe3+ + 8H2O
15Fe2+ + 2SO42- + 16H+
Fe3+ then catalyses further production
of acidity, without the need for O2
Consequences and
Some Solution to AMD
Consequences
• High acidity leads to leaching of various metals
– Heavy metals (Fe, Cu, Pb, Zn, Cd, Co, Cr, Ni, and Hg)
– Metalloids (As Sb)
– Other metals & elements Al, Mn, Si, Ca, Na, K, Mg
and Ba
– Whatever maybe present
• Can get pH < 0!
• Discoloration of waterways, choking & killing of
aquatic organisms (fish, plant, microorganisms,
etc)
Consequences and
Some Solution to AMD
Solutions
• Some mines near natural limestone deposits which
can neutralize the AMD
• Limestone chips can be added
• Addition of calcium oxide or hydroxide
• Anaerobic bacteria
• Sealing the mines
The pE Scale
Used to characterize the reducing nature of natural
water
• Low pE ~ lots of electrons available thus water is very
reducing
• High pE ~ few electrons available so dominant
species are oxidizing in nature
• It is defined as – log10 of the effective concentration
(or activity of) electrons in water
– Analogous to pH scale, recall you really don’t have
bare protons, so don’t really have bare electrons’,
– Dimensionless numbers (i.e. no units)
• Along with pH it can be used to determine the
dominant species in a body of water
Example Using pE
Scenario: Traditional leather tanning industries soak
the hides in an aqueous solution of chromium (III).
Suppose the waste water from the tannery contains 26
mg/L chromium (III). As it enters a river, the dissolved
oxygen can oxidize the chromium (III) to dichromate.
If the water in the river is well aerated and has a pH of
7.0, what’s the dominant species?
Step I
O2 + 4H+ + 4e-
2H2
Large amounts of dissolved
O2 in H2O; dominant
O process is reduction of O2
pE = pEo – (1/n) logQ
Example Using pE
O2 + 4H+ + 4e-
2H2O
Step I
pE = pEo – (1/n) logQ
pEo = Eo/(0.0591) = 1.229/0.0591 =
= 20.795
pE = 20.795 – (1/4)log{1/(PO2 [H+]4)} =
= 14.63
• Can use this step for any well aerated water system, as long
as you know the pH
• Assumption O2 in equilibrium with the water
• Assumption is no dissolved CO2
Example Using pE
Cr2O72-(aq) + 14H+(aq) + 6e-
2Cr3+(aq) + 7H2O
Step 2: Calculate pEo
pEo = Eo/0.0591 = 1.33/0.0591 = 22.504
Step 3: set up the correct expression for Q, &
substitute in your known values
14.63 = 22.504 –
- (1/6)log{[Cr3+]/([Cr2O72-][10-7]14)}
The chromium and oxygen are in the same water
system, so they are at equilibrium i.e. same pE!!!
Example Using pE
Step 4: Simple rule of logs re‐arrange the
expression
14.63 = 22.504 – (1/6)log(1/[10-7]14) –
- (1/6)log([Cr3+]/([Cr2O72-][10-7]14)
Step 5: Simplify the expression
14.63 = 8.504 - (1/6)log([Cr3+]/[Cr2O72-])
-36.756 = log([Cr3+]/[Cr2O72-])
and finally: 1.75 × 10-37 = [Cr3+]/[Cr2O72-]
This small number means the dichromate dominates!
Which is very toxic, and carcinogenic
Acid Base Chemistry
in Natural Waters
Natural waters contain lots of CO2
– Source mostly from air, but can be from
decomposition of organics
– Easily forms carbonic acid
– Acid easily dissociates
– Reason rain water slightly acidic
– the pH of CO2 saturated water is 5.6 @ 25 °C,
given that the [CO2] is 365 ppm
Carbon Cycling in Ecosystems
Carbon Dioxide and Water
CO2 + H2O ↔ H2CO3
(KH= 10-1.5 mol/atm·L)
H2CO3 ↔ HCO3- + H+
(H1a≈ 10-6.3 mol/L)
HCO3- ↔ CO32- + H+
(H2a≈ 10-10.3 mol/L)
Acid Base Chemistry
in Natural Waters
Oceans are a large sink for atmospheric CO2
– Sequestration of CO2 in the ocean would
increase the acidity of surrounding
waters
– Increased acidity could be detrimental to
some ocean life
– Increase in atmospheric CO2 has decreased
ocean pH ~ 0.1
Biotransformation
and
Biodegradation
Aerobic
Anaerobic
Biotransformation
 Biotransformation is the chemical
modification (or modifications) made
by an organism on chemical compounds
such as (but not limited to) nutrients,
amino acids, toxins, etc.
 If this modification ends in mineral
compounds like CO2, NH4+, or H2O, the
biotransformation is called
mineralisation.
Biotransformation
 Biotransformation of various pollutants is a
sustainable way to clean up contaminated
environments. These bioremediation and
biotransformation methods harness the
naturally occurring, microbial catabolic
diversity to degrade, transform or accumulate
a huge range of compounds including
hydrocarbons (e.g. oil), polychlorinated
biphenyls (PCBs), polyaromatic
hydrocarbons (PAHs), pharmaceutical
substances, radionuclides and metals.
Biotransformation
 Biological processes play a major role in the
removal of contaminants and pollutants from
the environment. Some microorganisms
possess an astonishing catabolic versatility to
degrade or transform such compounds. New
methodological breakthroughs in
sequencing, genomics, proteomics,
bioinformatics and imaging are
producing vast amounts of
information.
Biotransformation
 As we learn more through functional genomic
analysis of various bacterial species, biological
processes are gradually replacing some older
physico-chemical methods;
 Some technologies that have been used are:
 high-temperature incineration
 various types of chemical decomposition
(e.g., base-catalyzed dechlorination)
 UV oxidation.
Biotransformation
Class of contaminants
Specific examples
Chlorinated solvents
Trichloroethylene
Perchloroethylene
Aerobic Anaerobic Potential sources

Drycleaners
Chemical manufacturing
Electrical manufacturing
Polychlorinated biphenyls
4-Chlorobiphenyl
4,4-Dichlorobiphenyl

Power stations,
Railway yards
Chlorinated phenol
Pentachlorophenol

Wood treatment, Landfills
“BTEX”
Benzene
Toluene
Ethylbenzene
Xylenes

Oil production and storage
Gas work sites, Airports
Paint manufacture
Port facilities, Railway yards,
Chemical manufacture
Polyaromatic hydrocarbons
(PAHs)
Naphtalene
Antracene
Fluorene
Pyrene
Benzo(a)pyrene
Pesticides
Atrazine, Carbaryl
Carbofuran, 2,4-D,
Coumphos, Diazinon
Glycophosphate
Parathion, Propham

Oil production and storage
Gas work sites
Coke plants (кокс)
Machine works
Landfills, Power stations
Tar production and storage
Boiler ash dump sites



Agriculture, Landfills
Wood treatment
Pesticide manufacture
Recreational areas
Biotransformation
 Microbes will adapt and grow at subzero
temperatures, as well as extreme heat, desert
conditions, in water, with an excess of oxygen, and
in anaerobic conditions, with the presence of
hazardous compounds or on any waste stream.
 The main requirements are an energy source and a
carbon source.
 Because of the adaptability of microbes and other
biological systems, these can be used to degrade or
remediate environmental hazards.
Biotransformation
We can subdivide these microorganisms
into the following four groups:
 Aerobic
 Anaerobic
 Ligninolytic fungi
 Methylotrophs
Biotransformation
 Aerobic bacteria
 In the presence of oxygen.
 Examples of aerobic bacteria recognized for their
degradative abilities are Pseudomonas,
Alcaligenes, Sphingomonas, Rhodococcus, and
Mycobacterium. These microbes have often been
reported to degrade pesticides and hydrocarbons,
both alkanes and polyaromatic compounds.
 Many of these bacteria use the contaminant as the
sole source of carbon and energy.
Biotransformation
 Anaerobic bacteria
 In the absence of oxygen.
 Anaerobic bacteria are not as frequently used
as aerobic bacteria.
 There is an increasing interest in anaerobic
bacteria used for bioremediation of
polychlorinated biphenyls (PCBs) in river
sediments, dechlorination of the solvent
trichloroethylene (TCE), and chloroform.
Biotransformation
 Ligninolytic fungi
 Fungi such as the white rot fungus
Phanaerochaete chrysosporium have the ability
to degrade an extremely diverse range of
persistent or toxic environmental pollutants.
 Common substrates used include straw, saw
dust, or corn cobs.
Biotransformation
 Methylotrophs
 Aerobic bacteria that grow utilizing methane for
carbon and energy.
 The initial enzyme in the pathway for aerobic
degradation, methane monooxygenase, has a
broad substrate range and
 is active against a wide range of compounds,
including the chlorinated aliphatics
trichloroethylene and 1,2-dichloroethane.
Environmental Factors in
Biotransformation
 Nutrients
 Although the microorganisms are present in
contaminated soil, they cannot necessarily be there
in the numbers required for ioremediation of the
site. Their growth and activity must be stimulated.
 Biostimulation usually involves the addition of
nutrients and oxygen to help indigenous
microorganisms.
Environmental Factors in
Biotransformation
 These nutrients are the basic building blocks of
life and allow microbes to create the necessary
enzymes to break down the contaminants.
 All of them will need nitrogen, phosphorous, and
carbon
 Carbon is the most basic element of living forms
and is needed in greater quantities than other
 elements. In addition to hydrogen, oxygen, and
nitrogen it constitutes about 95% of the weight of
cells.
Composition of
a microbial cell
Element
%
Element
%
Carbon
Nitrogen
Oxygen
Hydrogen
Phosphorus
Sulfur
Potassium
50
14
20
8
3
1
1
Sodium
Calcium
Magnesium
Chlorine
Iron
All others
1
0.5
0.5
0.5
0.2
0.3
Optimum environmental conditions
for the degradation of contaminants
Parameters
Condition required for
microbial activity
Optimum value
for an oil
degradation
Soil moisture
25–28% of water
30–90%
5.5–8.8
6.5–8.0
Oxygen content
Aerobic, minimum airfilled pore space of 10%
10–40%
Nutrient content
N&P
C:N:P = 100:10:1
T (°C)
15–45
20-30
Contaminants
Not too toxic
5–10% of dry
weight of soil
Heavy metals
Total content 2000 ppm
700 ppm
Type of soil
Low clay or silt content
Soil pH
Oil biodegradation
 Petroleum oil is toxic for most life forms and
episodic and chronic pollution of the
environment by oil causes major ecological
perturbations. Marine environments are
especially vulnerable, since oil spills of coastal
regions and the open sea are poorly containable
and mitigation is difficult.
 In addition to pollution through human
activities, millions of tons of petroleum enter
the marine environment every year from
natural seepages.
Oil biodegradation
Structural
classification
of some
crude oil
components
Oil biodegradation
Sources of oil
into the sea.
Oil biodegradation
The fate of oil in the marine environment
Oil biodegradation
Crude-oil degrading micro-organisms
Bacteria
Yeast
Fungi
Bacteria
Yeast
Fungi
Achromobacter
Candida
Aspergillus
Corynebacterium
Sporobolomyces
Luhworthia
Acinetobacter
Cryptococcus
Cladosporium
Flavobacterium
Torulopsis
Penicillium
Alcanivorax
Debaryomyces
Corollasporium
Mycobscterium
Trichosporon
Varicospora
Alcaligenes
Hamsenula
Cunninghamella
Nocardia
Yarrowia
Verticillium
Bacillus
Pichia
Dendryphiella
Pseudomonas
Brevibacterium
Rhodotorula
Fusarium
Rhodococcus
Burkholderia
Saccharomyces
Gliocladium
Sphingomonas
Streptomyces
Oil biodegradation
Aerobic degradation
of crude oil
hydrocarbons with
its environmental
impact.
Biodegradation of nalkanes: metabolism
begins with the
activity of a
monooxygenase
which introduces a
hydroxyl group into
the aliphatic chain.
[A]-monoterminal
oxidation,
[B]-biterminal
oxidation,
[C]- subterminal
oxidation); TCAtricarboxylic acid
cycle
Oil biodegradation
Biodegradation of
aromatic
hydrocarbons:
metabolism begins
with the activity of a
monooxygenase or a
dioxygenase which
introduce one or
two atoms of
oxygen; it can also
begin with
unspecific reactions
Oil biodegradation
Proposed pathway for
anaerobic degradation
of n-alkanes; activation
via addition of a C1moiety (subterminal
carboxylation at C3).
Pathway according to
So et al. (2003); TCA
tricarboxylic acid cycle
Oil biodegradation
Proposed pathways
of anaerobic
degradation of
aromatic
hydrocarbons;
activation via
addition of
fumarate, [1]—
succinate.
Pathways according
to Spormann and
Widdel (2000), and
Wilkes et al.
(2002); TCA—
tricarboxylic acid
cycle
Oil biodegradation
 Despite its toxicity, a considerable fraction of
petroleum oil entering marine systems is
eliminated by the hydrocarbon-degrading
activities of microbial communities, in
particular by a remarkable recently discovered
group of specialists, the so-called
hydrocarbonoclastic bacteria (HCB).
 Alcanivorax borkumensis, a paradigm of HCB
and probably the most important global oil
degrader, was the first to be subjected to a
functional genomic analysis.
Oil biodegradation
 The functional genomic analysis of Alcanivorax
borkumensis has yielded important new
insights into its capacity for
(i) n-alkane degradation including
metabolism, biosurfactant production and
biofilm formation,
(ii) scavenging of nutrients and cofactors in
the oligotrophic marine environment, as well
as
(iii) coping with various habitat-specific
stresses.
Oil biodegradation
Compound
Reaction
Naphthalene (C10H8)
C10H8 + 20H2O → 10CO2 + 48H+ + 48e-
1-Methylnaphthalene (C11H10)
C11H10 + 22H2O → 11CO2 + 54H+ + 54e-
2-Methylnaphthalene (C11H10) C11H10 + 22H2O → 11CO2 + 54H+ + 54e2-Ethylnaphtalene (C12H12)
C12H12 + 24H2O → 12CO2 + 60H+ + 60e-
Phenanthrene (C14H10)
C14H10 + 28H2O → 14CO2 + 66H+ + 66e-
Anthracene (C14H10)
Pyrene (C16H10)
C14H10 + 28H2O → 14CO2 + 66H+ + 66eC-16H10 + 32H2O → + 16CO2 + 74H+ + 74
e
Benzene (C6H6)
C6H6 + 12H2O → + 6CO2 + 30H+ + 30e-
Toluene (C7H8)
C7H8 + 14H2O → + 7CO2 + 36H+ + 36e-
Xylene (C8H10)
C8H10 + 16H2O → + 8CO2 + 42H+ + 42e-
Mycoremediation
 Mycoremediation is a form of bioremediation,
the process of using mushrooms to return an
environment (usually soil) contaminated by
pollutants to a less contaminated state.
 In an experiment a plot of soil contaminated
with diesel oil was inoculated with mycelia of
oyster mushrooms; traditional bioremediation
techniques (bacteria) were used on control
plots. After four weeks, more than 95% of many
of the PAH (polycyclic aromatic hydrocarbons)
had been reduced to non-toxic components in
the mycelial-inoculated plots.
Other biodegradation
processes
 The bacterium Deinococcus radiodurans (the
most radioresistant organism known) has been
modified to consume and digest toluene and
ionic mercury from highly radioactive nuclear
waste.
Energy and Mass Cycling in
Ecosystems
we all are eating
solar energy
In most ecosystems, sunlight is absorbed and converted
into usable forms of energy via photosynthesis. These
usable forms of energy are carbon-based.
Energy and Mass Cycling in
Ecosystems
A Throphic Pyramide (a)
and a Simplified
Community Food Web (b)
Nitrogen Cycling in Ecosystems
Phosphorus Cycling
in Ecosystems
Bioaccumulation and
Biomagnification
Bioconcentration
factor
Bioaccumulation
Methyl Mercury
Biomagnification
DDT
Hg
Bioaccumulation
Bioconcentration factor
C(in the organism)
BCF =
C(water)
Regression Equations for Estimating
BCF for Varieties of Fish
log[BCF] = 0.76 · log[Kow] - 0.23
Rainbow Trout, Moskitofish, Bluegill sunfish
log[BCF] = 2.791 - log[S]
S – water solubility (ppm)*
Brook Trout, Carp, Rainbow Trout, Fathead Minnow
log[BCF] = log[Kow] - 1.32
log[BCF] = 1.119 · log[Kow] - 1.579
*ppm – parts per million
Various
Various
Kinetics of
Biotransformation
 A simple biodegradation model is one in which
microorganisms are in contact with water
containing a dissolved organic chemical that
serves as the energy substrate.
 Because chemical uptake of the organic
chemical into a cell of the microorgamism is
followed by enzymatic biotransformation, rates
of biodegradation and uptake rates are
equivalent (steady-state)
Kinetics of
Biotransformation
Michaelis-Menten enzyme kinetics
V  V max 
C
C  Ks
where:
V is the rate of chemical uptake per cell [M/(cell time)]
Vmax is the maximum possible chemical uptake rate
C is the concentration of dissolved chemical [M/L3]
Ks is the 0.5 saturation constant [M/L3]
[C]
Kinetics of
Biotransformation
Michaelis-Menten enzyme kinetics
if Ks >> C (i.e. at low
concentrations)
V ≈ (V(max)/Ks)∙C
if Ks << C (i.e. at
high concentrations)
V ≈ V(max)
Kinetics of
Biotransformation
Michaelis-Menten enzyme kinetics
*************
therefore
dC
V  X
dt
Ct
 kt
e
Co
&
where X is the cell density
Kinetics of
Biotransformation
Michaelis-Menten enzyme kinetics
and in the same way
Xt
dC
t
e
V  X
&
Xo
dt
where X is the cell density
and μ is specific growth rate
Kinetics of
Biotransformation
Examples of aerobic degradation rate
constants
COMPOUND
ANTHRACENE
RATE CONSTANT [day-1]
0.007-0.055
ATRAZINE (N-PHOSPHORYLATED)
0.22
BENZENE
0.11
CHLOROBENZENE
PARATHION
0.0045
<0.00016
PHENOL
0.079
2,4,5-TETRACHLOROETHYLENE
0.001
1,4,5-TRICHLOROPHENOACETIC ACID
0.0005
Kinetics of
Biotransformation
Examples of anaerobic degradation
rate constants
COMPOUND
CARBOFURAN
DDT
ENDRIN
LINDANE
PENTACHLOROPHENOL
RATE CONSTANT [day-1]
0.026
0.0033
0.03
0.0046
0.07
TRIFURALIN
0.025
TRICHLOROETHENE
0.009
1,1-DICHLOROETHENE
0.0063
Abiotic chemical transformations
Photodegradation – the nature of light
*********************
Light is a type of electromagnetic waves
ν = c/λ
where ν is wave frequency [sec-1]
c is speed of all electromagnetic waves (light
included) = 3.0∙108m/sec
λ is the wave length [m]
Abiotic chemical transformations
Photodegradation – the nature of light
Abiotic chemical transformations
Photodegradation – the nature of light
Solar radiation spectrum
100 nm < λ < 3000 nm
Visible light
400 nm < λ < 700 nm
λ < 400 nm
λ > 700 nm
ultraviolet
infrared
ozone
partial absorbtion
water
Abiotic chemical transformations
Photodegradation – the nature of light
Light penetration into surface waters
Iz = Io
-ηz
e
where I is the light intensity [watts/m2]
η is the extinction coefficient [m-1]
Abiotic chemical transformations
Photodegradation (photodissociation,
photolysis, or photodecomposition)
 Photodegradation is decomposition of a
compound by radiant energy
It is a chemical reaction in which a chemical
compound is broken down by photons.
Photodegradation includes
photodissociation, the breakup of molecules
into smaller pieces by photons
Abiotic chemical transformations
Photolysis of water
The bulk of our Earth's oxygen does not come
from photosynthesis, but from photodissociation
- that is, the breaking down of water into its
component parts by ultraviolet light.
 H2O + 2 photons (light) → 2 e- + 2 H+ + ½O2
This happens to water vapor in the upper
atmosphere. The lighter hydrogen escapes into
space and is lost, the oxygen - being heavier settles to the Earth.
Abiotic chemical transformations
Photodegradation – the nature of light
Solar radiation energy
E = h∙ν
where E is the photon energy
h is Plank’s constant = 6.6∙10-34 J∙sec
and ν is wave frequency [sec-1]
Abiotic chemical transformations
Photodegradation (photodissociation,
photolysis, or photodecomposition)
The photochemical transformation of a
molecule into lower molecular weight
fragments, usually in an oxidation proces.
This term is widely used in the destruction
(oxidation) of pollutants by UV-based
processes.
Abiotic chemical transformations
Photodegradation (photodissociation,
photolysis, or photodecomposition)
It is not limited to visible light.
Any photon with sufficient energy can affect
the chemical bonds of a chemical compound.
Since a photon's energy is inversely
proportional to its wavelength, electromagnetic
waves with the energy of visible light or higher,
such as ultraviolet light, x-rays and gamma
rays are usually involved in such reactions.
Abiotic chemical transformations
Direct and indirect photodissociation of
organic compounds in water
Direct photolysis is a process in which
molecules get excited by the absorption of a
photon, and that results in a chemical reaction,
usually oxidation.
The direct effects of UV irradiation include
transformation of organic compounds into
other substances, breaking of chemical bonds,
or even complete degradation of organic
substances.
Abiotic chemical transformations
Direct and indirect photodissociation of
organic compounds in water
Also, UV radiation causes dissociation of
oxidizing compounds and formation of highly
reactive radicals that are capable of degrading
organic pollutants.
Indirect photolysis of substances occurs
through a reaction with OH-radicals, ozone or
NO3-; these three chemicals are considered the
most important photo-oxidizing agents present
in the environment.
Abiotic chemical transformations
Photodegradation
Schematic
presentation of
phenol degradation
in aqueous
solutions
Abiotic chemical transformations
Kinetics of Photodegradation
-dC/dt = kp∙I
Ct = Co∙e-kpI(t-to)
log(co/ct) = kp∙I∙(t-to)
Abiotic chemical transformations
Kinetics of Photodegradation
Examples of Half-Lives for Degradation via
Direct Photolysis
Pesticides
λ (nm) t½
PAHs
λ (nm) t½
Parathion
5
10 days
Anthracene
366
0.73 hrs
Mirex
5
1 year
Benz[a]Anthracene
5
3.3 hrs
Methyl Parathion
5
30 days Benzo[a]Pyrene
5
1 hr
Methoxychlor
5
29 days Chrysene
313
4.4 hrs
Malathion
5
15 hrs
Fluoranthene
313
21 hrs
DDE
5
22 hrs
Naphtalene
313
70 hrs
2,4-D, Methyl ester
5
62 days Phenanthrene
313
8.4 hrs
12 days
313, 366 0.68 hrs
2,4-D, Butoxyethyl
Carbaryl
ester 5
5
50 hrs
Pyrene
Abiotic chemical transformations
Hydrolysis
H2O + R X
R OH +
+
H
+
X
where R is a hydrocarbon group
and X is an anionic group (commonly halogen atom)
Abiotic chemical
transformations
Examples of
Hydrolysis
Rates of Hydrolysis
dC/dt = -kH2O × C × [H2O] = -k’n × C
Ct = Co × e-k’n t