Vern. Lecture 4.

Question 1

What was produced in Wheel Jane?

Answer 1

Tin from fine grained casserite

Question 2

What were the dangers of mining Wheel Jane?

Answer 2

Very susceptible to flooding

Question 3

When and why was Wheel Jane abandoned?

Answer 3

June 1991 as price of tin dropped from 3-4k/ton to 1k/ton

Question 4

What happened after Wheel Jane closed?

Answer 4

Heavy rain and cessation of pumping flooded nearby mines.

Groundwater rebound, water seeped into river Carnon.

Mine water was acidic (pH 2-3).

320 million litres of toxic mine slurry into Falmouth bay.

Cadmium levels were 600x the limit.

Question 5

Who paid for the treatment of the mine water in the Wheel Jane case?

Answer 5

Taxpayers as mine was abandoned. Cost £10 million.

Question 6

What was done to treat Wheel Jane?

Answer 6

In 1994 a passive treatment plant was installed. Toxic elements in the mine water were reduced by passive methods such as limestone and reed beds. Water is now cleanest its been since mining began.

Question 7

The goal of remediation is to reduce dangerous chemical to less dangerous ones. Express this in terms of chromium.

Answer 7

Chromium VI is carcinogenic, soluble and mobile. THis is treated by reducing it to Chromium III. This is less toxic and mobile and forms a precipitate. The success of this is determined by the formation and stability of the precipitates.

Question 8

List the 11 major elements

Answer 8

H, O, C, N, Ca, Mg, K, Na, P, S, Cl

Question 9

What are micronutrients and give examples?

Answer 9

Essential in trace amounts. Used in enzymes which catalyse reactions in important physiological processes. Fe, Mn, Ni, Cu, Co, Zn, V, Sn, Mo, Se, I, F

Question 10

What are the 5 purely toxic elements?

Answer 10

As, Cd, Pb, Hg, Al

Question 11

What are the differences between As V and As III?

Answer 11

As V is less toxic and less mobile as it adsorbs more readily to iron minerals. As III is more toxic.

Question 12

Why were water wells dug in Bangladesh and by who?

Answer 12

In the 1970s the government of Bangladesh and WHO started shallow ground water well programme to supply the country with water.

Question 13

How did aresnic concentrations vary with depth in Bangladesh?

Answer 13

Very high arsenic concentrations between 0-100m subsurface. From 150m on the arsenic concentrations were safe

Question 14

Why did the Holocene aquifers contain so much arsenic?

Answer 14

Contains 6% organic material, anoxic, reducing condiotion. Deposited less than 11,000 years ago and has not been flushed by last glaciation.

Question 15

What causes As mobilisation?

Answer 15

Microbial reduction of Fe minerals and release of As.this process makes use of anoxic and organic rich system

Question 16

How does the ‘pyrite theory’ account for As mobilisation?

Answer 16

Water table drops exposing FeAsS to air in vadose zones. Causing the Fe, As and S to oxidise. This generates Fe(OH)3 and releases As (V). As (V) however rapidly adsorbs onto Fe(OH)3. During recharge of aquifer anoxic water rises which induces microbial release mechanism.

Question 17

How do phosphate fertilisers allow arsenic to flow into water?

Answer 17

They outcompete the As (V) for adsorption onto Fe(OH)3 thus releasing the arsenic into the water.

Question 18

How does the ‘SONO’ filter work?

Answer 18

Question 19

What does an excess of fluorine cause and where is it a particular concern?

Answer 19

Excess in flourine causes skeletal fluorosis. This limits joint movement and causes muscle wasting. In China 2.7 million people are affected and in India 6 million.