chemical properties & contaminant...
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Chemical Properties & Contaminant ClassesAN ENVIRONMENTAL CHEMISTRY INTRO
Lecture 5 – Fall 2016
MSC-210 – Marine Environmental Sampling & Analysis
Environmental Chemistry• Environmental Chemistry:
The study of sources, reactions, transport, and fate of chemical entities in the air, water, and soil of environments, as well as their effects on human health and the natural environment.
• Antoine-Laurent de Lavoisier (1743-1794)• Paris, France
• 1789, published Elementary Book of Chemistry
• Atmospheric environment
• Animal Respiration
• Combustion
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Role of Environmental ChemistryCharacteristics of the Molecule
• Surface area, molecular weight (mw), functional groups, chemical bonds, etc.
Physical-Chemical Properties of the Compound
• Aqueous solubility, vapor pressure (vp), melting point (mp), Octanal/Water partitioning, etc
Transformation & Distribution in the Environment
• Persistence, transportation, bioaccumulation, biomagnification, etc.
Biological Effects
• Lethal toxicity, reduction in growth, reduction in reproduction, etc.
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Behavior of Chemicals• Governed by:• Physical-Chemical properties
• Transformation processes
• Degradation processes
• Physical-Chemical Properties include:• Molecular weight (mw)
• Boiling point (bp)
• Melting point (mp)
• Solubility in water
• Vapor pressure (vp)
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Basic ChemistryCRASH COURSE
The Atom
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• Nucleus contains Protons & Neutrons:◦ Protons: positively charged
◦ Neutrons: no charge
• Electron shells contain Electrons:◦ Electrons: negatively charged
◦ Very small, almost negligible mass
◦ Valence Shell: outer electron shell
p+n
p+p+
p+
p+
np+
n
nnn
e-
e-
e-
e-
e-
e-
Not to scale
p+
n
e-
The Atom
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• Atomic Number: number of protons in the nucleus
• Atomic Mass: mass of the atom
Molecules
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Physical States of Matter• Solids• Definite volume & shape
• Molecules have a fixed relationship to one another
• Liquids• Definite volume, but variable shape
• Molecules free to move among each other
• Gases• Indefinite volume, indefinite shape
• Molecules free to move among each other
• Molecules far apart
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Increasin
g Energy
Physical-Chemical Properties:• Melting Point (mp):• The temperature at which a substance changes from solid to
liquid at atmospheric pressure.• At the melting point, the solid and liquid phase exist in
equilibrium
• Boiling Point (bp):• The temperature at which a substance changes from liquid to
gas at atmospheric pressure.• At the boiling point, the vapor pressure of the liquid becomes
sufficient to overcome atmospheric pressure and allow bubbles of vapor to form inside the liquid.
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Physical-Chemical Properties:• Vapor Pressure (vp):• The pressure that is exerted by a liquid
• Directly related to bp
• Aqueous Solubility:• How soluble a substance is in water
• Solubility tables
• Solute
• Solvent
• Solution
• Precipitant
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• Hydrophilic• Lipophobic
Physical-Chemical Properties:• Lipid Solubility:• How soluble a substance is in lipids/fats
• Hydrophobic
• Lipophilic
• Bioaccumulation
• Biomagnification
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Properties of SubstancesSubstance
Molecular Formula
Environmental Occurrence
Physical State
Melting Point (°C)
Boiling Point (°C)
Oxygen O2
21% of atmosphere
Gas -218 -183
Nitrogen N2
78% of atmosphere
Gas -210 -196
Water H2OOceans, lakes, rivers
Liquid 0 100
CommonSalt
NaCl 3.5% of seawater Solid 801 1413
Quartz SiO2
Rocks, sand, geological strata
Solid 1610 2230
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Organic vs. Inorganic
Organic Compounds Inorganic Compounds
Formed mainly of Carbon (C), Hydrogen (H), Oxygen (O), andNitrogen (N) – having a “backbone” of Carbon and Hydrogen
Simple molecules formed by atoms of any element; typically do not contain both Carbon (C) and Hydrogen (H)
Lower melting points Higher melting points
Lower boiling points Higher boiling points
Generally, less soluble in water Generally, more soluble in water
Examples: Sugars, Lipids, Amino Acids
Examples: H2O, CO2, NaCl
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Contaminant Classifications LEGACY POLLUTANTS & EMERGING CONTAMINANTS
MAJOR CHEMICAL -USE CLASSES
MAJOR ENVIRONMENTAL CONTAMINANT GROUPS
Legacy Pollutants
Well known pollutants that were introduced in the past (many of which have since been banned, or strictly regulated), that are still present and causing problems in the environment today.
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Key Characteristics of Legacy Pollutants• Persistence
• Bioaccumulation
• Biomagnification
• Global Fate & Transport
• Bioavailability
• Bioaccessibility
• Acute Toxicity and/or carcinogenicity
• Endocrine Modulations
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Legacy Pollutants: Examples
Organic Inorganic
PCBs Mercury
DDT Sulfur
Chlorinated Hydrocarbons Nitrate
Petrol, Fuel Oil Arsenic
Explosives Copper
Herbicides Lead
Insecticides Chromium
Rodenticides Radioactive Waste
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Contaminants of Emerging Concern (CECs)
Pollutants that either:
- have only recently been detected in the environment due to advances in analytical instrumentation;
or
- are from more recently developed materials and products with widespread use in everyday life.
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CECs: Examples
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Persistent Organic Pollutants (POPs)
Polybrominated Diphenyl Ethers (flame retardants, foams, plastics, etc.)
Perfluorinated Organic Acids
Organochlorine pesticides
Pharmaceuticals & Personal Care Products (PPCPs)
Human prescribed drugs and over-the-counter medications
Bactericides, antimicrobials, antibiotics, anti-fungals
Sunscreens
Veterinary medications
Endocrine-Disrupting Chemicals (EDCs)
Synthetic and natural estrogens and androgens
Nanomaterials
Cosmetics, Sunscreens, Carbon Nanotubes
Environmental Compartments & Chemical FugacityCHEMICAL TRANSPORT & FATE
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Environmental Compartments
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ParticulatesAir
WaterParticulates
Porewater
Soil Biota
Sediment
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Environmental Chemodynamics
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FugacityFugacity: ◦ the tendency of a compound to escape from
one environmental compartment into another one
◦ Latin term fugere, “to flee”
◦ Chemicals escape from compartments in which they have high fugacities to those of low fugacity
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Two-Phase Partitioning Partitioning of a chemical into two adjacent, immiscible phases
(compartments) can be described mathematically as:
C1 = K(C2)n
or
LogC1 = LogK + nLogC2
Using these equations, partitioning coefficients for different phase interactions can be calculated…
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Partition Coefficients
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Media Partition
Coefficient & Equation
Description
Air-Water KH
KH = Pair
Cwater
Relationship between the partial pressure of the chemical in air & the corresponding concentration in water
Octanol-Water
KOW
Kow = Coctanol
Cwater
Relationship between hydrophilic & hydrophobic phases
Biota-Water
(BioconcentrationFactor)
KB (BCF)
KB = Cbiota
Cwater
Characterizes the magnification of concentrations through the food chain; hydrophobicity important
Particle-Water
(Soil Sorption)
KOC
KOC = Corg carbon
Cwater
Characterizes relationship between solid & liquid phases to determine mobility in soils, sediments, and particles; solubility important
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Partition CoefficientsFortunately, these values can be looked up…and modeled!
For general physical-chemical property information regarding common hazardous contaminants:◦ ATSDR – Toxicological Profile Sheets
For physical-chemical properties and environmental fate estimation:◦ US EPA – Estimation Program Interface (EPI)
For estimating chemical fates and exposures:◦ US EPA – Exposure & Fate Assessment Screening Tool (E-FAST)
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Trends• Persistent & Bioaccumulating Organic Pollutants:
◦ Low aq. solubility
◦ High logKOW
◦ High logBCF
◦ High logKOC
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Let’s look at some chemical profiles…ATSDR Toxicological Profiles:
• DDT, DDE, DDD
• PCBs
• Pyridine
• Formaldehyde (CH2O)
• Mercury
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Let’s look at some chemical profiles…ATSDR Toxicological Profiles:
Chemical Aq. Sol. logKOW logBCF logKOC
DDT
PCBs
Pyridine
CH2O
Mercury
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ReferencesLecture Content
• Connell, D.W. (2005). Basic Concepts of Environmental Chemistry, 2nd ed. Boca Raton, FL: CRC Press, Taylor & Francis Group.
Images
• Title Slide: • Drawing Chemical Formula
http://www.presentermedia.com
• Slide 5: • Chemistry Lab clipart
http://www.openclipart.org
• Slide 8:• O2 – http://www.ck12.org
• H2O – http://www.openstudy.com
• Slide 9: • H2O bonds - http://commons.wikimedia.org
• Ionic bonding – http://study.com
• Slide 10: • States of Matter http://www.britannica.com
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ReferencesImages (cont’d)
• Slide 25: ◦ Block Diagram
www.usgs.gov
• Slide 26: • Green fish
www.iconshut.com
•Slide 27:• Contaminant transport/Chemodynamics
www.simmakers.com
•Slide 28:◦ Chemical movement
www.usgs.gov
Slide 29◦ Boiling in beaker
www.fallriverschools.org
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