Acid Deposition - Air Pollution and Global Warming: History, Science, and Solutions - page 221

Chapter 10

Acid Deposition

Acid deposition occurs when an acid - primarily sul-
furic acid, nitric acid, or hydrochloric acid - is emit-
ted into or produced in the air and deposits to soils,
lakes, grass, forests, or buildings. Acid deposition can
be dry or wet. Dry acid deposition is the direct depo-
sition of acid gases to surfaces. Wet acid deposition is
the deposition to the surface of acids dissolved in rain-
water ( acid rain ), fog water ( acid fog ), or liquid aerosol
particles ( acid haze ). On the Earth's surface, acids have
avariety of environmental impacts, including damage
to microorganisms, fish, forests, agriculture, and struc-
tures. When breathed in, acids in high concentrations
are harmful to humans and animals. Acid deposition
problems have occurred since coal was first combusted
and increased during the Industrial Revolution in the
eighteenth century. The problems became more severe
with the growth of the alkali industry in nineteenth-
century France and the UK. In this chapter, the history,
science, and regulatory control of acid deposition prob-
lems are discussed.

phase sulfuric acid, and NO x (g) oxidize to nitric acid.
Humans have combusted coal for thousands of years. In
the 1200s, sea coal was brought to London and used in
lime kilns and forges (Section 4.1). It was later burned
in furnaces to produce glass and bricks, in breweries
to produce beer and ale, and in homes to provide heat.
Beginning with the eighteenth-century Industrial Rev-
olution , coal combustion provided energy for the steam
engine.
During the late eighteenth century, a second major
source of atmospheric acids emerged. In France and
England, the demand for soaps, detergents, cleansers,
glass, paper, bleaches, and dyes was increasing rapidly.
Soap wasproduced by combining an alkali, such as
potash [ potassium carbonate ,K 2 CO 3 (s)] or soda ash
[ sodium carbonate ,Na 2 CO 3 (s)], with animal fat. The
source of potash was the ashes of wood fires (pot
ashes) from which the potash was extracted using
hot water. Because England and France were largely
deforested, wood for potash was imported from North
America, Scandinavia, or Russia, increasing the cost
of potassium carbonate. Sodium carbonate was also
expensive. It could be extracted from coastal barilla
plants in Spain and the Canary Islands, mined from
mineral deposits in Egypt's Lakes of Natron (Section
1.2.1.6), or extracted from sea kelp washing up on
the beaches of Scotland and Ireland. However, these
sources were either far (Mediterranean and Egypt) or
labor intensive (sea kelp). For example, more than
100,000 seasonal workers were required to collect and
process sea kelp along Scotland's shores in order to

10.1. Historical Aspects of Acid Deposition
Acid deposition is caused by the emission or atmo-
spheric formation of gas- and aqueous-phase sulfuric
acid (H 2 SO 4 ), nitric acid (HNO 3 ), or hydrochloric
acid (HCl). Historically, coal was the first and largest
source of anthropogenically produced atmospheric
acids. Coal combustion emits gas-phase sulfur diox-
ide [SO 2 (g)], hydrochloric acid [HCl(g)], and nitrogen
oxides [NO x (g)]. SO 2 (g) oxidizes to gas- and aqueous-