Introduction - Principles of Chemical Separations with Environmental Applications - page 8

Radium

10 6

Vitamin B-12

10 4

Mined Gold

Penicillin

10 2

Factor of 2
differential in price

Uranium from Ore
Magnesium from Seawater
Bromine from Seawater
Sulfur from Stack Gas

1

Copper
Mined Sulfur
Oxygen

10 − 2

100 percent 1 percent 1 thousandth of

1 percent

1 millionth of
1 percent

1 billionth of
1 percent

DILUTION (expressed as percent concentration)

Figure 1.2 Sherwood plot [1]. Reproduced with permission of National Academy
Press.

1.6 Historic perspective of environmental pollution

Rainwater is acidic due to atmospheric CO 2 ,SO 2 and nitrogen oxides; its pH is typically
5.6. Measurements of 4.6 are found in some regions of the US and values of 4.0 (and
even 3.0) have been documented. Since pH is a log scale, these low pH values represent
much stronger acids than occur naturally. The effects of these stronger acids on plants,
animals, and materials have been well documented. Acid deposition can initially be dry.
Gases and/or salts can be deposited. They can cause damage “as is,” such as uptake by
plants, or when hydrated [8]. In addition to contributing to acid rain, CO 2 also acts as a
“greenhouse gas” and contributes to global warming.
The issue of chemical emissions and their effect on the environment is not limited
to recent history. As shown below, acid rain was first documented in the 1600s. The
chronology below lists some important events in the identification, monitoring, and steps
to reduce emissions for acid rain and global warming [9].
1661-2 English investigators John Evelyn and John Graunt publish separate studies

speculating on the adverse influence of industrial emissions on the health of
plants and people. They mention the problem of transboundary exchange of
pollutants between England and France. They also recommend remedial mea-
sures such as locating industry outside of town and using taller chimneys to
spread “smoke” into “distant parts.”

1734 Swedish scientist C. V. Linne describes a 500-year-old smelter at Falun, Sweden:

“ ... we felt a strong smell of sulfur ... rising to the west of the city ... a

poisonous, pungent sulphur smoke, poisoning the air wide around ... corroding

the earth so that no herbs can grow around it.”

1872 English scientist Robert Angus Smith coins the term “acid-rain” in a topic called

Air and Rain: The Beginnings of a Chemical Climatology . Smith is the first to