Australian Science Illustrated — Issue 54 2017

40 | SCIENCE ILLUSTRATED

unfiltered into the blood stream, which will

carry them to all body tissue.

In 1991, American scientists, who had

observed 8,111 individuals for 17 years,

showed that early deaths were not evenly

distributed among the populations of eight

cities. There were more deaths in areas with

considerable air particle pollution. In 1999,

scientists were able to make another ground-

breaking conclusion: cities which had done a

lot to combat pollution in the previous eight

years had reduced the number of early

deaths considerably.

The positive message: it is worthwhile

doing something – even in the short term.

In recent decades, scientists have also

realised that the tinier the smog particles,

the more hazardous they are. Tiny particles

are more likely to produce reactive and

highly oxidising peroxides. Oxidation is a

harmful process for body cells, speeding up

ageing and possibly converting healthy cells

into cancer cells. In the cells, peroxides

could harm other chemical compounds by

oxidising them, so they can no longer

function as intended, such as DNA and other

cellular structures.

So, today efforts are focused on

measuring and minimizing the number of

harmful particles sized “PM2.5”. PM is short

for particulate matter such as fine dust

particles, and 2.5 refers to the diameter of

the particles, which average 2.5 micrometres

ENERGY

The burning of coal emits a toxic cocktail of mercury,

NOx, and sulphur. In China, at least 400,000 people

die annually due to sulphur air pollution.

Coal is getting less cheap, but it's not getting any less polluting. That is, not unless

power companies adopt "clean coal" technology that, while it might not reduce CO 2

that much, certainly does lower the amount of other toxins produced.

New coal-fi red power stations are clean(ish)

1 Coal is gasified and mixed with water and oxygen at a temperature

of about 1,400 °C. The result is synthesis

gas consisting of carbon monoxide and

hydrogen. Slag is screened out.

2 The gas passes through a calcareous solution, in which

solid and liquid waste such as sulphur

and mercury are filtered out. Pure

sulphur is used by chemical companies.

3 The remaining gas is burned with pure oxygen instead of

atmospheric air. The lack of atmospheric

nitrogen in the combustion reduces

the smoke's content of NOX gases.

Pure smoke in the chimney

About half of the world’s coal burning takes place in China, but the huge country also has one of

the most ambitious schemes for converting its energy generation into clean and green energy.

Now

SMOG REDUCTION:

60-90 %

CLAUS LUNAU

COARSE MATERIAL

SCREENED OUT

GASIFIER

SEPARATEDSULPHUR

HEAT EXCHANGER

SLAG

WATER

OXYGEN

COAL

COMBUSTION CHAMBER

TECHNOLOGY SMOG