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Flashcards in Metal pollution Deck (17):
1

Heavy metal definition

Specific gravity 5x that of water
Metal element toxic in nature

2

List some major heavy metals

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

3

Mining as a source of metal pollution

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

4

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)

5

Sources of heavy metal pollution in industry

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

6

Stages of a geochemical investigation

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

7

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

8

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

9

What are chemical extractions?

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

10

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

11

River example of partitioning

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

12

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.

13

Important fine sediments include..

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

14

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

15

Mo - Molybdenum example

More mobile in alkaline conditions
Concentrated in certain soils overlying shales

16

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.
http://www.wou.edu/las/physci/ch412/pourbaix.htm

17

What is diagenesis

'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.