Metal pollution

Question 1

Heavy metal definition

Answer 1

Specific gravity 5x that of water

Metal element toxic in nature

Question 2

List some major heavy metals

Answer 2

Antimony - Sb
Arsenic - As
Mercury - Hg
Lead - Pb
Cadmium - Cd
Chromium - Cr
Nickel - Ni
Zinc - Zn

Question 3

Mining as a source of metal pollution

Answer 3

Many sources are sulphides so release metals when oxidized. Smelting can release emissions.

Question 4

Agriculture as a source of heavy metal pollution

Answer 4

Impurities in fertilisers - pesticides - wood preservatives.

Animal production - sewage sludge - compost manure - Corrosion of metals (corrugated iron/barbed wire)

Question 5

Sources of heavy metal pollution in industry

Answer 5

Alloys and steels - manufacture/disposal/recycling
Batteries
Paints (especially lead-Pb)
Printing

Question 6

Stages of a geochemical investigation

Answer 6

Thinking
Sampling
Analysis
Interpretation - assess quality of sample - geochemical interpretation
Conclusions - recommended action

Question 7

What are some effects of Cu and Zn?

Answer 7

Cu - deficiency = changes in ossification, anemia
Cu - Excess = Cirrhosis of liver
Zn - deficiency = Growth retardation/appetite loss
Zn - Excess = Nausea, anemia

Question 8

What is bioavailability?

Answer 8

The ABSOLUTE CONCENTRATION of an element is less important than the form in which its found in the environment. Quantity of element absorbed

Question 9

What are chemical extractions?

Answer 9

A separation process consisting of a separation of a substance from a matrix.

Question 10

What is partitioning of the chemical

Answer 10

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
http://en.wikipedia.org/wiki/Extraction_%28chemistry%29

Question 11

River example of partitioning

Answer 11

Different elements in different fractions - so they can be
Dissolved
Particulate
Held in metallic coatings
Organically associated
Incorporated in residual structures.

Question 12

How does grain size effect elemental concentration

Answer 12

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.

Question 13

Important fine sediments include..

Answer 13

Organic humic acids (principal component of human substances)
Clays
Oxyhydroxides of Fe and Al
(humic acids tend to bind to clay)

Question 14

Clay sediment explained

Answer 14

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

Question 15

Mo - Molybdenum example

Answer 15

More mobile in alkaline conditions

Concentrated in certain soils overlying shales

Question 16

What are eH pH diagrams

Answer 16

Maps out possible stable (equilibrium) phases of an aqueous electrochemical system (soils)
Predictions made on form of element in different environments.
http://www.wou.edu/las/physci/ch412/pourbaix.htm

Question 17

What is diagenesis

Answer 17

‘post depositional changes’ can move elements around specially is oxygen conditions change.
Need to be careful concentrations that might be found are POLLUTION and not NATURAL CONCENTRATION of elements from geochemical migration.