Environmental Chemistry of Organic Substances

CHEM 651

Spring 2008

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Course ObjectivesObjectives

– 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

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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.

Environmental LawsImportant 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

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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.

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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

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

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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 non-toxic? Green Chemistry

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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)

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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

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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

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.

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Metal Mining47.3%

Mfg32.2%

Coal Mining0.2%

Chem Distrib0.0%

Haz Waste4.0%

Utilities16.2%

Petroleum 0.1%

Dioxins

PCBs

Pesticides

Other

PAHs

Mercury

Total releases of chemicals regulated according to TRI7.1 billion pounds (2000)

Total PBT releases 12 million pounds (2000)

TLRI 2000 Figures

Source: www.epa.gov/tri

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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

Source: http://chesapeake.usgs.gov/

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

Principal Sources - Identifying where chemicals come from

Ag Fertilizers

Energy Production

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 15.8 440

Land Use Cover (%)

Agricultural 31 93 <5

Mixed Urban 5 <1 54

Forest 62 6.8 25

Forested Land

Agricultural Land Use

Suburban Land Use

Urban Land Use: Substantially Altered Landscape

Atmospheric32%

Point Source20%

Nonpoint Source

48%

Example Source Profile: N Sources to The Bay

Vehicles35%

utilities37%

Area Sources21%

Industry7%

•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

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

Comparison of Land Use v. Runoff

Source: http://ww.cbf.org

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Atmosphere Hydrosphere

Geosphere

Biota

•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 and concentration differential between compartments

“The environment” is defined by 4 major compartments

Major compartments are further divided into sub-compartmentsAir – air, aerosolsWater – water, particles, colloidsSoil – soil, air, water, colloids

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Chemical Fate CartoonArrows indicate pathways

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Global Air Circulation & Global Distribution

Source: http://www.newmediastudio.org/DataDiscovery/Hurr_ED_Center/Easterly_Waves/Trade_Winds/Trade_Winds.html

Net PCBTransport is toward poles;grasshopper effect; dependent on physical & chemical properties

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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

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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)

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Naphthalene

Phenanthrene

Benzo(a)pyrene

Pyrene

Polycyclic Aromatic Hydrocarbons (PAHs)

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

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12

3

4

567

8

9

10

12

3a

5a6a

10a 10b

11 12a

12b

12c

Example: benzo(a)pyrene

a

b

cd

efghij

k

l m

n

o

p q r

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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

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•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

Major PAH Sources

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Free Radical Condensation

• Formation of PAHs by pyrolysis• Reaction scheme proposed by Connell• Occurs in industrial furnaces

C

C

CC

CC

CC C

C

CC

naphthalene

High Temperature Anoxygenic Free Radical

Condensation

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Cl

Cl

Cl

Cl

Cl

ClCl

Cl

Cl

Cl

Cl

Cl

Cl

Polychlorinated Biphenyls (PCBs)

2

3

4

5

6

6'

5'

4'

3'

2'

IUPACNomenclature

General Molecular Formula C12H10-nCln

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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

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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 penta = 46 nona = 2

di = 12 hexa = 42 deca = 1

tri = 24 hepta = 24

tetra = 42 octa = 12 209 Congeners +

atropisomers

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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

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min10 20 30 40 50 60 70

counts

0

10000

20000

30000

40000

50000

60000

70000

80000

Time, min

Res

po

nse

GC-ECD Chromatogram of PCBsGC-ECD Chromatogram of PCBs

PCBs present as a complex mixture and are difficult to separate and analyze in environmental samples

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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

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O

O

1

2

3

9

8

7

6 4

O

O

Cl

Cl

Cl

Cl

O

1

2

3

46

7

8

9

O

Cl

ClCl

Cl

Chlorodibenzo-p-dioxins Chlorodibenzofurans

2,3,7,8-TCDD 2,3,7,8-TCDF

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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

C

C

OCH2CH2CH2CH2CHCH3

O

O

OCH2CH2CH2CH2CHCH3

CH2CH3

CH2CH3

DEHP- Di-(2-ethylhexyl) phthalate

C

C

OCH2CH2CH2CH3

O

O

OCH2CH2CH2CH3

DBP – Di-(n-butyl) phthalate

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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

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H3C S C CH

CH3

CH3

N O C NH

O

CH3

N N

N

Cl

HN NH C2H5H7C3

C2H5

C2H5

N C

CH2

O

CH2Cl

OCH3

N

N

CH3

OPO

O

O

C2H5

H5C2

Cl

Cl

Cl

Cl

Cl

Cl

C ClCl

NH

Cl

Cl

C

O

NCH3

OCH3

Aldicarb (oxime carbamate)

Atrazine (triazine)

Alachlor (chloracetamide)

Diazinon (organophosphorus)

Chlordane (organochlorine)

Linuron (urea)

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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

O

Br Br

BrBr

O

Br Br

BrBr

Br

O

Br Br

Br Br

Br

Br

Br

Br

Br

Br

BDE 47BDE 99

BDE 209

BDE 47 2,2’,4,4’-tetrabromo DPE

BDE 99 2,2’4,4’,5 -pentabromo DPE

BDE 209 decabromo DPE

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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

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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

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Ibuprofen(+)-2-(4-Isobutylphenyl) propionic acid

Naproxen(+)-2-(6-Methoxy-2-naphthyl)-propionic acid

Triclosan5-chloro-2-(2,4-dichlorophenoxy) phenol

OH

CH3HOOH

H N(CH3)2

OH

C

OOH

OHO

NH2

O

Oxytetracycline4-(dimethylamino)-1,4,4,5,5, 6,11,12a-octa-hydro-3,5,6,10,12,12a-hexa-hydroxy-6-methyl-1,11-dioxo-naphthacenecarboxamide

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Fluorinated Organic Chemicals

• Derived from the degradation of perfluorinated polymers, such as Teflon, and are used as surfactants, fire retardants and lubricants

C C C C C C C C OH

O

F

F

F

F

F

F

F

F

F

F

F

F

F

F

F

Perfluorooctanoic Acid(fluoropolymer production, foams and varnishes)

R

R CF2 S O-

O

O

Perfluorooctanesulfonic Acid (surfactants & fire retardants)

R CF2 S

O

O

NH2

Perfluorooctanesulfonamide

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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

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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

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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

HO

Cholesterol

C23H47 C

O

OH

Tetracosanoic Acid