common toxic pollutants and analytical methods
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Common Toxic Pollutants and Analytical Methods
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Characteristics of “Contaminants of Concern”
TOXIC - Makes you sick.- Kills you.- Gives you cancer.- Endangers plants/animals
PERSISTENT - Remains in the environment for “a long time”: Months, years.-Breaks down slowly or not at all
BIOACCUMULATIVE
-“Builds up” in the tissues of organisms. Accumulates.-- May amplify up a food chain-(e.g., Hg in ocean -> tuna)
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Toxicity
ACUTE Short-term, high dose
CHRONIC Long-term, low dose
EXPOSURE - Dose + Duration
TOXIC ACTION Example
Somatic failure Kidney, liver failure, nervous system damage
Carcinogenesis Cancer
Teratogenesis Birth defects
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Classes of Toxic Contaminants
Inorganic materials
Synthetic organic compounds
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Inorganic Toxic Materials
Metals: Transition metals on the periodic table Mode of toxicity: Often substitute for or
interrupt function of normal biological metals (e.g., Fe, Ca, Zn)
Main Toxic Metals in ~Order of Toxicity Hg Cd Pb (Ag) Cu Zn
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Other Toxic Inorganics
Metalloids Arsenic (As) Selenium (Se)
“Transient” compounds (easily break down, rarely persistent) Ammonia (NH3) Hydrogen sulfide (H2S) Cyanide (CN-)
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Inorganics:Key Characteristics
Cannot degrade or break down E.g., Pb is Pb is Pb
Hence inherently “persistent”
“Speciation” often important A metal may occur in various chemical
forms or “species” E.g., different redox states, or bound to
various other materials Different species may have very different
properties
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Examples of Speciation Effects
Metal Species Toxicity Mobility
Hg2+
Hg0 Hg(CH3)2
Less toxicToxicExtremely toxic
Low mobilityVolatile gas~High mobility
Cr3+ (trivalent)CrO4
2- (hexavalent)
Low toxicityHigh toxicity
Low mobilityHigh mobility
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Total Metal vs Species
Total metal = “analytical concentration”
More complicated: Individual species may be analyzed
Or, sometimes easier or necessary to calculate species with chemistry tools or computer model
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AAS: Atomic Absorption Spectrometry
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Flame AAS
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Gas Chromatography
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Gas Chromatography
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Typical GC
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GC Autosampler
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GC
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GC-Mass Spectrometry GCMS
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GC (with Mass Spectrometry)
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GCMS “Fingerprint”
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