Download ES 120 TOXICS IN THE ENVIRONMENT

ES 120 TOXICS IN THE
ENVIRONMENT
LECTURE 3: ELEMENTS
SCOPE OF LECTURE
• Important elements in ecotoxicology
KEEP IN MIND THAT:
• Elements are neither created nor destroyed
• Elements are non-degradable
• Human activity increases bioavailability of
elements by:
– Release from lithosphere into biosphere
– Redistribution in biosphere
– Changing the form of elements (e.g. from Cr(III) to
Cr(VI) or N2 into NOx)
– Changing environmental conditions (e.g. a decreased
pH caused by acid rain facilitates assimilation of
aluminum)
MERCURY
• AKA quick silver
• Neurotoxin, especially organomercury compounds
(methylmercury)
• Most applications are obsolete
(pigments, fungicides,
thermometers, dental amalgams,
batteries)
• Still used in gold mining and
released at coal burning
• Complex environmental cycling
Cinnabar
CADMIUM
• Rare element, most
common in zinc ores
• Resembles zinc, which in
part explains its toxicity
• Binds strongly to ligands,
especially S containing
• Applications: Ni-Cad
batteries, plastics
stabilizer, rubber
vulcanization, pigments
Greenockite
LEAD
Galena
• Abundant in earth crust and
widely distributed because of
past uses
• Very malleable, heavy, low
melting point.
• Common past applications:
plumbing, pigment, insecticide
(lead arsenate) anti-knock
additive (tetra-ethyl lead)
• Present applications include
crystal, ceramics, weights, car
batteries.
COPPER
• Important since antiquity
• Alloys: bronze, brass, gold (<24K)
• Good conductor: high end cooking pots,
electronics
• Used as pesticide (antifouling,
bactericide) and wood preservative
Chalcopyrite,
CuFeS2
Navajo jewelry
with turquoise
Copper and gold plated
roofs, Alexander Nevski
cathedral, Sofia
NICKEL
• Common element in earth
crust
• Used in alloys to prevent
corrosion, such as in
coins and in stainless
steel (with iron,
chromium, molybdenum
and/or vanadium)
• Some nickel compounds
are carcinogenic; may
cause dermatitis in
sensitive individuals
Limonite, (Fe,Ni)O(OH)
Pentlandite, (Fe,Ni)9S8
CHROMIUM
Crocoite, PbCrO4
Chromite, FeCr2O4
• Occurs predominantly as Cr(III)
and Cr(VI)
• Cr(III) is essential micronutrient
• Cr(VI) is especially toxic
• Toxicant in Erin Brokovitz
movie
• Used in alloys (stainless steel),
chrome plating, paints, tanning
and wood preservation
TIN
• Very malleable, low melting
point, metal pulverizes below
13oC
• Used since antiquity as metal
(utensils, toys, foil – now
mostly replaced by
aluminum) and in bronze
(weaponry, statues)
• Used as anticorrosive (tin
plating)
• Of most environmental
concern are the organo-tin
compounds, such as tri-butyltin (TBT, antifouling agent)
Casserite, SnO2
Medieval tin plate
Arsenic
• High levels in some ores and
water sources (Bangladesh)
• King of poisons and poison of
kings since antiquity
• Used as wood preservative
and in metal alloys
• Past uses: pesticide (lead
arsenate), rat poison, pigment.
Arsenopyrite, FeAsS
Victim of arsenic?
HALOGENS
• Reactive elements: F2, Cl2, Br2, I2
• When covalently bound to organic compounds,
they increase the persistence and toxicity of
those compounds – see next lecture
• Cl2 is a major industrial base chemical
• House hold uses: disinfectant (bleach, betadine)
and discoloring agent (bleach), carbonate
remover (hydrochloric acid in bath tub & tile
cleaners)
PHOSPHORUS
Dead zone in the Gulf of Mexico
Red tide, massive growth of
toxic dinoflagellates
• Major nutrient
• Fertilizer (phosphate),
causes algal blooms
and anoxia in aquatic
and marine
environments
NITROGEN
• Major nutrient
• Fertilizer (nitrate,
ammonium), causes
algal blooms and
anoxia in aquatic and
marine environments
• As NOx major
airpollutant causing
smog and contributing
to the weathering of
alkaline stone
Smog in Los Angeles
SULFUR
• Ancient pesticide
(SO2)
• Preservative (sulfite)
• Major air pollutant
(SO2), released with
the burning of sulfur
rich fuel (coal)
• Causes acid rain
(SO2 turns into
sulfuric acid)
RADIOACTIVE POLLUTANTS
• Radioactive isotopes disintegrate to form
eventually stable elements while emitting
- a radiation (helium ions),
- b radiation (high energy electrons)
- g radiation (photons with extremely small wave
lengths) and/or
- neutrons
DAMAGE POTENTIAL
Damage due to radioactivity depends on:
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Type of emission
Energy content of emission
Rate of disintegration
Potential of an isotope to accumulate in
the body
PLEASE NOTE THAT
• Radiation does not lead to contamination
• A short half-life implies a lot of radiation
and potential damage in a short time;
waste management is easy
• A long half-life implies relatively little
radiation over an extended period; waste
management is problematic
EXAMPLES
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14C,
naturally formed in the atmosphere, long half life,
used in dating
3H (tritium), low energy, medium half life, used in tracer
studies
131I, short half life, used to assess the functioning of the
thyroid gland
Radioactive isotopes of essential elements, used in
biochemical studies
60C, used in radiotherapy
Cs, Sr and I isotopes of major concern in nuclear fall out
U and Pu isotopes, nuclear fuel, extremely toxic as
chemicals
LATEST CONCERN:
NANOPARTICLES
• Size is in the nanometer range
• Size and shape are determinants for
toxicity
• Metal oxides and fullerenes (“bucky balls”)
• Explosive increase in production,
applications
EXAMPLES OF NANOPARTICLES
• ZnO – antibacterial, antifungal,
anti-corrosion, catalytic, and UV
filtering properties:
In paint, plastic, textiles; catalyst
for methanol synthesis, personal
care products, sunscreen
• TiO2 - high UV absorption,
photocatalytic activity
germicidal, and thermal
stability:
In pigments, cosmetics
cosmetics, hard coatings,
plastics, toners
Next Lecture
• Organic Toxicants
• Homework:
– PE: 1.2, 1.3
– Assignment: Table on Metals, Metalloids and
Non-Metals due next week but start now: it is
a long assignment you don’t want to complete
in one session