Common Toxic Pollutants and Analytical Methods

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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”