Flashcards in Metal pollution Deck (17):
Heavy metal definition
Specific gravity 5x that of water
Metal element toxic in nature
List some major heavy metals
Antimony - Sb
Arsenic - As
Mercury - Hg
Lead - Pb
Cadmium - Cd
Chromium - Cr
Nickel - Ni
Zinc - Zn
Mining as a source of metal pollution
Many sources are sulphides so release metals when oxidized. Smelting can release emissions.
Agriculture as a source of heavy metal pollution
Impurities in fertilisers - pesticides - wood preservatives.
Animal production - sewage sludge - compost manure - Corrosion of metals (corrugated iron/barbed wire)
Sources of heavy metal pollution in industry
Alloys and steels - manufacture/disposal/recycling
Paints (especially lead-Pb)
Stages of a geochemical investigation
Interpretation - assess quality of sample - geochemical interpretation
Conclusions - recommended action
What are some effects of Cu and Zn?
Cu - deficiency = changes in ossification, anemia
Cu - Excess = Cirrhosis of liver
Zn - deficiency = Growth retardation/appetite loss
Zn - Excess = Nausea, anemia
What is bioavailability?
The ABSOLUTE CONCENTRATION of an element is less important than the form in which its found in the environment. Quantity of element absorbed
What are chemical extractions?
A separation process consisting of a separation of a substance from a matrix.
What is partitioning of the chemical
Defined as the ration of the element between phases. The partition co-efficient depends on composition, temperature and pressure but is independent of element concentration.
So different elements are in different fractions
River example of partitioning
Different elements in different fractions - so they can be
Held in metallic coatings
Incorporated in residual structures.
How does grain size effect elemental concentration
Strong correlation between sed grain size and metal conc.
As grain size DECREASES surface area to volume ratio INCREASES so for processes like - ion exchange - absorption and coating particles, the smaller particles predominate.
Important fine sediments include..
Organic humic acids (principal component of human substances)
Oxyhydroxides of Fe and Al
(humic acids tend to bind to clay)
Clay sediment explained
As grain size decreases, the fraction of silica content decreases, surface area increases and clay mineral content increases.
Sampling only small grains reduces variation, but all processes take place on smaller particles so its justifiable.
METALS CONCENTRATED INTO FINER FRACTIONS OF SEDIMENTS
Mo - Molybdenum example
More mobile in alkaline conditions
Concentrated in certain soils overlying shales
What are eH pH diagrams
Maps out possible stable (equilibrium) phases of an aqueous electrochemical system (soils)
Predictions made on form of element in different environments.