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Common Toxic Pollutants and Analytical Methods
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)
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
Classes of Toxic Contaminants
Inorganic materials
Synthetic organic compounds
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
Other Toxic Inorganics
Metalloids Arsenic (As) Selenium (Se)
“Transient” compounds (easily break down, rarely persistent) Ammonia (NH3) Hydrogen sulfide (H2S) Cyanide (CN-)
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
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
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
AAS: Atomic Absorption Spectrometry
Flame AAS
Gas Chromatography
Gas Chromatography
Typical GC
GC Autosampler
GC
GC-Mass Spectrometry GCMS
GC (with Mass Spectrometry)
GCMS “Fingerprint”