An Introduction to Environmental Chemistry

these SVOCs will condense from the atmosphere back into, or on to, soils, water
and vegetation. Given the global poleward movement of air masses (see Section
1.3.2), SVOCs can be transported large distances from their place of manufac-
ture and used in temperate industrial areas to remote polar regions. The low tem-
peratures in polar environments promote condensation of the SVOCs trapping
them on the cold land surface and in its vegetation. The overall process has been
likened to a global ‘distillation system’ (Fig. 7.26). Most SVOCs probably require
a number of transportation ‘hops’ to arrive in polar regions, although more
volatile organic compounds in rapidly moving air masses may make the journey
in a single ‘hop’ (Fig. 7.26).

Global Change 275

500 1000 1500 2000

Depth (m)

MSA concentration (ppb)

50

25

0

nss–SO

2 –

aerosol

concentration (ppb)

4

300

Temperature

Age (thousands of years)

Present

Warmer

Colder

13 33 56 66 107 141

0

Fig. 7.24150 000-year record of methane sulphonic acid (MSA) concentration, non-sea-salt-
sulphate (nss-SO 42 - ) aerosol concentration and temperature reconstruction (from oxygen
isotope data) from an Antarctic ice core. MSA and nss-SO 42 - aerosol concentrations are both
high during very cold conditions, e.g. the last glacial period between 18 and 30 thousand
years ago (see text for discussion). After Legrand et al.(1991).