Transcript Organic Chemicals In The Environment

Environmental Chemistry of
Organic Substances
CHEM 651
Spring 2008
1
Course Objectives
Objectives
– identify primary sources of important classes of
organic substances of environmental interest
– understand and predict processes which
govern the behavior and fate (phase transfer
and reaction) of organic chemicals in the
environment
– obtain or derive important physicochemical
properties of organic compounds
– Rapidly assess the holistic environmental
distribution of organic chemicals using simple
distribution models
2
Organic Substances In The Environment
• Environmental Organic Chemicals: Chemicals released
into the environment as a result of human activities that
affect human and ecosystem health at very low
concentrations (i.e., ppm concentrations or lower); or natural
(biogenic) organic substances that are useful as molecular
markers of environmental processes.
• S2ET2: the most important issues to study in environmental
organic chemistry are sources, sinks, exposure, transport
and transformation.
Regulatory Chemistry
• Various laws relate to the protection of environmental and
human health. These laws are passed by Congress and
signed by the President. A summary of the various laws is
provided below. EPA is charged with administering these
laws and develops technical, operational and the legal
details.
3
Environmental Laws
•
•
•
•
•
•
•
•
•
•
•
•
Important Environmental Legislation to Minimize Risk
Atomic Energy Act
Clean Air Act
Clean Water Act
Comprehensive Environmental Response, Compensation and
Liability Act
Emergency Planning and Community Right to Know Act
(EPCRA)
Endangered Species Act
Energy Policy Act
Federal Food, Drug and Cosmetic Act
Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA)
Federal Water Pollution Control Amendments
Marine Protection, Research, and Sanctuaries Act
National Environmental Policy Act
4
Environmental Laws (cont’)
•
•
•
•
•
•
•
•
Nuclear Waste Policy Act
Occupational Safety and Health
Ocean Dumping Act
Oil Pollution Act
Pollution Prevention Act
Resource Conservation and Recovery Act
Safe Drinking Water Act
Toxic Substances Control Act (TSCA)
For more details, go to the following URL:
http://www.epa.gov/lawsregs/laws/index.html
5
Regulatory Chemistry: Examples
– Clean Air Act: Established funding and study for air
pollutants in 1963; Congress passed legislation in 1970, and
revised in 1990; EPA sets limits on certain air pollutants
– Clean Water Act: Establishes limits of chemicals
discharged into water bodies; first passed in 1972;
established water quality criteria and TMDLs
– Federal Insecticide, Fungicide, and Rodenticide Act
(FIFRA): Established to provide federal control of pesticide
distribution, sale, and use; EPA was given authority under
FIFRA not only to study the consequences of pesticide
usage but also to require users (farmers, utility companies,
and others) to register when purchasing pesticides
– Toxic Substances Control Act (TSCA): Established to
give EPA the ability to track the 75,000 industrial chemicals
currently produced or imported into the United States. EPA
repeatedly screens these chemicals and can require
reporting or testing of those that may pose an environmental
or human-health hazard. EPA can ban the manufacture and
import of those chemicals that pose an unreasonable risk.
6
Regulatory Chemistry (cont’)
• Emergency Planning & Community Right-to-Know Act
(EPCRA): Enacted by Congress in 1986 as the national
legislation on community safety; this law is designed to help
local communities protect public health, safety, and the
environment from chemical hazards
• Federal Food, Drug, and Cosmetic Act (FFDCA): Defines
"pesticide chemical" to be any substance that is a pesticide
under FIFRA, including all active and inert ingredients. Definition
in previous law was limited to pesticides used in the production
of a raw agricultural commodity; defines "pesticide chemical
residue" to be a residue of a pesticide chemical, its metabolites,
and degradates in or on raw or processed foods; allows EPA to
except a substance from these definitions, if its origin in food is
primarily natural or resulting from non-pesticidal use
• Environmental regulations drive research
• New regulations need to be scientifically based
7
Hazard & Risk and Risk Reduction
• The purpose of environmental chemistry is to minimize the risks
associated with chemicals used by society
• Hazard is a function of toxicity and exposure and related to
potential harm
Hazard = fn{Toxicity x Exposure}
• Toxicity relates to the inherent sensitivity of the organism to a
chemical and the mechanism of biological effect
• Exposure is related to the following scheme:
Structure of chemical  Physical and Chemical Properties
 Chemical Reactivity in Environment (distribution and
degradation)  Transport to Biological Receptor
• Risk relates magnitude of hazard and probability of its
occurrence
Risk = fn{hazard x probability of occurrence}
8
Role for Environmental Chemistry
• TSCA inventory contains 70,000 substances that
have not been fully evaluated; list is growing rapidly
• How do you ensure risk minimization with such a
large inventory of chemicals?
• Many chemical properties are not available through
empirical measurements
• Chemical design: how can we better design
chemicals to be environmentally friendly and nontoxic? Green Chemistry
9
Leading Environmental Pollutants
• Silt (erosion from farmlands and
urban/suburban regions)
• Nutrients (agricultural/urban runoff)
• Metals (urban runoff, industrial discharge,
energy production, transportation)
• Toxic Organics (agricultural/urban runoff,
energy production, transportation;
industry)
• Pathogens (feed lots, wastewater)
• Organic matter: (wastewater, runoff)
10
Emissions & Source Terms
• Emissions: mode of entry of organic
contaminants in the environment and
quantity of inputs
• Point sources: specific and determinable
sites of entry that can be regulated, e.g.,
pipe discharge, smokestack plumes
• Non-point sources: diffuse or multiple
sites of entry that are not easily regulated,
e.g., agricultural runoff, atmospheric
deposition, volatilization from land
surfaces
11
Some Critical Observations on Organics
• Egg shell thinning in Pelicans by DDT (1960’s) led to Rachel Carson’s book “Silent Spring”
• Ozone depletion by CFCs (1970’s – Nobel prize by
Rowland and Molina)
• Food chain biomagnification of synthetic
chemicals (1970’s)
• Global dispersal of organochlorines (1980’s)
• Health problems in polar Aboriginal populations
(1990’s)
• Nature versus nurture in public health issues
(present): causes of cancer, hormonal regulation
and other diseases
12
Toxics Loading and Release Inventory
• EPCRA
– TLRI: toxics loading and release inventory.
Industries required to document use and releases
of chemicals to the environment. Information is
available on the web (http://www.epa.gov/tri).
– Each year TRI inventory is compiled and
eventually published.
13
Coal Mining
0.2%
Metal
Mining
47.3%
Utilities
16.2%
Petroleum
0.1%
Chem
Distrib
0.0%
Mfg
32.2%
TLRI 2000 Figures
Total releases of chemicals
regulated according to TRI
7.1 billion pounds (2000)
Haz Waste
4.0%
Other
Pesticides
Dioxins
PCBs
Mercury
Total PBT releases
12 million pounds (2000)
PAHs
Source: www.epa.gov/tri
14
Water Quality Conditions in the US
A profile from the 1998 national water quality
Inventory report to congress
• ~40% of lakes, streams and estuaries sampled
were not clean enough to support fishing and
swimming activities throughout the US
• Rivers: 842,426 mi assessed, 35% polluted
• Lakes: 17,390,370 acres assessed, 45% polluted
• Estuaries: 28,687 sq mi assessed, 44% polluted
15
Water Quality is Affected
by Land Use Pressure
•~4 million people live in
Metro DC region
•By 2030 ~19 million
people will reside in Bay
watershed
•Human development
has substantially altered
the nature of
watersheds
•Watershed land use is
divided between natural
forested, urban, and
agricultural
Source: http://chesapeake.usgs.gov/
Principal Sources - Identifying
where chemicals come from
Energy Production
Ag Fertilizers
Urban Horticulture
Auto emissions
Sewage Discharge
Example Watersheds in Chesapeake
Bay Showing Land Use Diversity
Susque R. Chesterville Br. Anacos R.
Basin Area (km2) 70,000
Land Use Cover (%)
Agricultural
31
Mixed Urban
5
Forest
62
15.8
93
<1
6.8
440
<5
54
25
Forested Land
Agricultural Land Use
Suburban Land Use
Urban Land Use: Substantially Altered Landscape
Example Source Profile: N Sources to The Bay
Atmospheric
32%
Nonpoint
Source
48%
Point Source
20%
•70-75% of N is NO3•Basin states contribute
~50% of atmospheric N
•Atmospheric emissions
derived from up to 36
states
Source: Deposition of
Nitrogenous
Pollutants in the
Chesapeake Bay
Watershed (2002)
State Advisory Board
on Air Pollution
Industry
7%
Area Sources
21%
Vehicles
35%
utilities
37%
Comparison of Land Use v. Runoff
Ag fertilizer application
often occurs in fall
Urban runoff
comparable to Ag but
sustained through the
year; multiple sources
Forests act to buffer N
runoff through
denitrification; very low
N loadings in streams
Source: http://ww.cbf.org
Hydrosphere
Atmosphere
Biota
“The environment” is
defined by 4 major
compartments
Geosphere
Major compartments are
further divided into subcompartments
Air – air, aerosols
Water – water, particles, colloids
Soil – soil, air, water, colloids
•Chemicals can be introduced into atmosphere, hydrosphere or
geosphere
•Chemicals move between 4 major compartments through bulk or
diffusive transport processes (arrows)
•Bulk transport depends on mass transport of phase (air, water
particles, etc.) and chemical concentration in phase
•Diffusive transport depends on physical and chemical properties
25
and concentration differential between compartments
Chemical Fate Cartoon
Arrows indicate pathways
26
Global Air Circulation & Global Distribution
Net PCB
Transport is
toward poles;
grasshopper
effect;
dependent on
physical &
chemical
properties
Source:
27
http://www.newmediastudio.org/DataDiscovery/Hurr_ED_Center/Easterly_Waves/Trade_Winds/Trade_Winds.html
Chemicals of Concern
• Persistent, bioaccumulative, and toxic substances (PBTs)
– Example PBTs
• PAHs (polycyclic aromatic hydrocarbons)
• PCBs (polychlorinated biphenyls)
• Dioxins and Furans
• Pesticides
• PBDEs (Polybrominated diphenyl ethers)
• Phthalate Esters
• Emerging Contaminants
– Pharmaceuticals (human and vet) & Personal Care Products
– Perfluorinated acids (derived from Teflon)
– Fragrances
– Detergents
• Biogenic Substances
– Steroids
– Aromatic hydrocarbons
28
Xenoestrogens
• Some contaminants interfere with the normal
hormonal regulation of estrogen
• Evidence becoming more widespread of
“feminization” effect in males of aquatic species
• Examples of important environmental estrogens
– Organohalogen compounds (esp. those that
bind strongly to the AH receptor)
– Pesticides
– n-Nonyl phenol (detergents)
– Pharmaceuticals (esp. some steroids)
29
Polycyclic Aromatic Hydrocarbons (PAHs)
Naphthalene
Phenanthrene
Benzo(a)pyrene
Pyrene
30
Rules for PAH Nomenclature
1. The structural formula is written with the greatest possible number of rings lying in a
horizontal row.
2. Horizontal and vertical axes are drawn through the center of the longest horizontal
row in such a way that maximal number of rings (those which are not lined up
horizontally) are placed in the upper right quadrant and the minimal number of rings in
the lower left quadrant.
3. Carbon atoms are numbered in a clockwise direction starting with the carbon atom
that is not a part of another ring and is in the most counterclockwise position of the
uppermost ring or, if there is a choice, of the uppermost ring farthest to the right. Carbon
atoms common to two or more rings are not numbered.
4. Ring faces, which are not common to two rings, are lettered in alphabetical order with
the side between carbon atoms 1 and 2 designated "a". Alphabetical order is continued
clockwise around the molecule.
5. Compounds (or isomers) formed by the addition of a component are named with
numbers and letters enclosed in brackets. These are placed immediately after the name
of the added component to describe where a substituent group is attached or where a
ring is fused to the face of the molecule. Appropriate letters are used where a ring is
fused to more than one face of the molecule.
6. The structural formulas used show aromatic rings as plain hexagons and a methylene
group as CH2
Example: benzo(a)pyrene
p 12 q r 1 a
12a
11
2
b
l 10 m o
12b
10a 10b
3
9
n
c
12c
3a
k
d
4
8
6a
5a
j 7 i h6 g f 5 e
32
Sample Problems
Draw the following structures:
1. Benzo{e}pyrene [contrast with benzo(a)pyrene];
propose another way to name this chemical
2. Dibenz{a,h}anthracene
3. Fluoranthene (hint = benzo{j,k}fluorene)
3. Benzo{b}fluoranthene & benzo{k}fluoranthene
33
Major PAH Sources
•Fossil Fuels (runoff & discharges)
–Petroleum spills
–Coal piles
•Pyrolysis (carbon combustion)
•Coking operations
•Utilities (energy production)
•Automobiles (transportation)
•Incineration (waste reduction)
•Asphalt (weathering of paved surfaces)
•Natural Sources
– Diagenesis
– Catagenesis
34
Free Radical Condensation
C
C
C
C
C
C
C
C
C
C
C
High Temperature
Anoxygenic Free Radical
Condensation
C
naphthalene
• Formation of PAHs by pyrolysis
• Reaction scheme proposed by Connell
• Occurs in industrial furnaces
35
Polychlorinated Biphenyls (PCBs)
Cl
Cl
4
5
3
Cl
Cl
Cl
6
2
6'
2'
Cl
5'
Cl
3'
4'
IUPAC
Nomenclature
Cl
Cl
Cl
Cl
General Molecular
Formula
C12H10-nCln
Cl
Cl
36
Polychlorinated Biphenyls (PCBs)
• Uses
– Large capacitors & transformers: dielectrics
(~90%)
– Hydraulic & lubricating fluids
– Plasticizer and/or fireproofing agent
• Sources
– Incomplete combustion of PCB waste
– Vaporization of PCB in open use applications
– Leakage from closed systems (transformers)
– Illegal disposal
37
PCB Facts
• 2x109 kg produced worldwide commercially; production
peaked in 1960’s
• Banned in July 1979 (TSCA)
• Solely of anthropogenic origin
• Industrial applications used Aroclor mixtures, e.g., 1242,
1248, 1254, and 1260
12 = # C atoms
42 = average wt% chlorine in technical mixture
• Congener distribution (10 homologues)
mono = 2
di = 12
tri = 24
tetra = 42
penta = 46
hexa = 42
hepta = 24
octa = 12
nona = 2
deca = 1
209 Congeners +
atropisomers
38
PCBs in the Environment
• PCBs are globally distributed, and tend to be highly
concentrated in polar organisms
• PCBs have low water solubilities, favoring uptake into
sediments and biota
• PCBs are lipophilic and bioconcentrate
• PCBs are a particular problem in Arctic regions
because of reliance of endemic populations on high
fat diets
• PCBs are a “toxics of concern” in the Chesapeake
Bay region because of a high bioconcentration in
aquatic organisms and potential health effects in
humans
39
GC-ECD Chromatogram of PCBs
PCBs present as a complex
mixture and are difficult to
separate and analyze in
environmental samples
counts
80000
Response
70000
60000
50000
40000
30000
20000
10000
0
10
20
30
40
Time, min
50
60
70
min
40
Dioxins and Dibenzofurans
• Dioxin & Dibenzofuran Sources
– Municipal incineration (C + Cl-)
– Paper mill pulp waste (2 Cl2-Ar-OH yields
2,3,7,8-TCDD)
– Combustion of organic matter; can be derived
from natural sources
41
Chlorodibenzo-p-dioxins
9
Chlorodibenzofurans
1
9
8
O
2
7
O
3
6
8
2
7
4
O
Cl
Cl
Cl
O
Cl
Cl
3
O
6
Cl
2,3,7,8-TCDD
1
4
Cl
O
Cl
2,3,7,8-TCDF
42
Phthalate Esters
• Used to increase flexibility
of PVC-based polymers as
a softener
• Up to 50% (wt/wt) content
in some plastics
• 5-20 millions tons
produced annually
• There are 18 commercially
important PEs
• Most of high MW PEs used
in PVC products (>DBP)
• Some phthalates show
estrogenic effects (DBP)
• DEHP makes up ~50% of
phthalate ester use
O
CH2CH3
C OCH2CH2CH2CH2CHCH3
C OCH2CH2CH2CH2CHCH3
O
CH2CH3
DEHP- Di-(2-ethylhexyl) phthalate
O
C OCH2CH2CH2CH3
C OCH2CH2CH2CH3
O
DBP – Di-(n-butyl) phthalate
43
Pesticides
• Very biologically active and diverse group of compounds
used in crop protection and horticulture
– Herbicides
• Triazines
• Chloroacetamides
• Ureas & thioureas
• Thiocarbamates
• Phenoxy acids
• Oximes
– Insecticides
• Organochlorines
• Organophosphorus derivatives
• Carbamates
• Pyrethroids
44
CH3
CH3
H3C
S
C
O
CH N O C NH CH3
N
O
H5C2
O
CH3
P
O
N
O
Aldicarb (oxime carbamate)
C2H5
Diazinon (organophosphorus)
H7C3
HN
N
Cl
NH C2H5
Cl
Cl
N
N
Cl
C
Cl
Cl
Cl
Atrazine (triazine)
OCH3
Cl
Chlordane (organochlorine)
C2H5 CH2
N C
Cl
O
CH2Cl
NH C N
OCH3
O
C2H5
Alachlor (chloracetamide)
CH3
Cl
Cl
Linuron (urea)
45
Polybromodiphenyl Ethers
• High production volume chemicals used primarily as fire
retardants in many common clothing items, upholstery, and
hardware
• 132,000 t/year produced globally in 2002; amounts
increasing
• 30% of brominated flame retardants are BDPEs
Br
Br
Br
O
Br
O
Br
Br
BDE 47
Br
Br
Br
BDE 99
Br
Br
Br
Br
O
Br
Br Br
Br
Br
Br
BDE 209
BDE 47 2,2’,4,4’-tetrabromo DPE
BDE 99 2,2’4,4’,5 -pentabromo DPE
BDE 209 decabromo DPE
46
PDBE Production and Properties
• PBDE products produced by brominating
diphenyl ether in the presence of a catalyst (e.g.,
FeBr3)
• There are theoretically 209 PBDE congeners (like
PCBs)
• Major technical products contain mainly
pentaBDEs octaBDEs and decaBDE
• Log Kow values for PBDEs range from 5.9 to 10
• Vapor pressures are very low
• Very low water solubilities
• PBDEs have potential for global dispersal
47
Pharmaceutical Chemicals
• Divided into human and veterinary
pharmaceuticals
• Primary source to surface waters is wastewater
discharge or runoff from animal feedlots
• Trends in population and demographics correlate
with increasing drug use
• Many drugs are excreted intact or as liable
conjugates
• Important class of emerging contaminants
• Tend to have high solubilities in water and have
rapid degradation rates
• High potential biological activity in non-target
organisms is greatest concern
48
Naproxen
(+)-2-(6-Methoxy-2naphthyl)-propionic
acid
HO
CH3
OH
H
N(CH3)2
OH
Ibuprofen
(+)-2-(4-Isobutylphenyl)
propionic acid
C
OH
OH
O
OH
O
NH2
O
Oxytetracycline
Triclosan
5-chloro-2-(2,4dichlorophenoxy)
phenol
4-(dimethylamino)1,4,4a,5,5a, 6,11,12a-octahydro-3,5,6,10,12,12a-hexahydroxy-6-methyl-1,11-dioxonaphthacenecarboxamide
49
Fluorinated Organic Chemicals
• Derived from the degradation of perfluorinated
polymers, such as Teflon, and are used as
surfactants, fire retardants and lubricants
F
F
F
F
F
F
F
F
O
O
C C C C C C C C OH
F
F
F
F
F
F
R CF2 S
F
NH2
O
Perfluorooctanesulfonamide
R
Perfluorooctanoic Acid
(fluoropolymer
production, foams and
varnishes)
O
R CF2 S O
-
O
Perfluorooctanesulfonic Acid
(surfactants & fire retardants)
50
Perfluoroalkyl Carboxylates (PFCAs)
• Structural formula of PFCAs is F(CF2)nCO2, n  7
• Production began in 1947 using electrochemical
fluorination
• Properties include chemical stability, surface tension
lowering, ability to create stable foams, flame
retarding, varnishes, water repellants
• Estimates of total global production, 1975 to 2004,
range from 4400 to 8000 tons
• Most PFCAs used in the production of fluoropolymers
and foams
• Estimates of total source emissions from 1960 to
2004 range from 3200 to 7300 tons; direct emissions
(manufacture) at 3200 to 6900 while indirect
(impurities & degradation of product) at 30 to 350
51
Perfluoroalkyl Carboxylates (PFCAs)
• Predominant PFCAs include perfluorooctanoate (C8)
and perfluorononanote (C9)
• The pKa of PFOA is 2-3 and is acidic, mostly
dissociated in surface waters in the form of PFO
• PFO is water soluble (9.5 g/L @ 25 oC) and tends to
form miscelles
• PFOA has an estimated vapor pressure of 4.2 Pa
(very low)
• Increasing concentrations seen for some PFCAs
Arctic in seals, sea birds and polar bears
52
Fatty Acids and Sterols
•Important molecular marker compounds for
sources of natural organic matter
•Molecular marker compounds are source specific,
conservative, and relatively unreactive
•Sterols – alcohols of the steroid family (steroids
are 4 ring aliphatic hydrocarbons of biological
origin)
•Fatty acids – long chain carboxylic acids
O
C23H47
HO
Cholesterol
C OH
Tetracosanoic Acid
53