Chemistry Reference
In-Depth Information
2.1.2 Artificial Soil Sealing by Man-made Infrastructure
Artificial soil sealing is the direct loss of soil by its covering with urban
infrastructure in the form of roads, buildings and recreation areas, etc. This
generally results in a loss of function, though some storage functions may be
maintained. The amount of soil sealed globally is not known, but urban land
cover, as of 2000,
44
has been estimated to be 0.4 Mkm
2
. With increasing
urbanisation, it is projected that urban infrastructure will cover a land area of
ca. 1 Mkm
2
by 2030. Estimates of sealing in Europe suggest that 9% of
European land area is now covered by some form of impermeable
infrastructure.
45
Sealed soils are changed because they no longer interact
freely with the other compartments of the Earth system. Thus the movement of
matter and energy is severely inhibited, as is the ability to deliver ecosystem
services, other than perhaps the protection of heritage as a cultural service.
d
n
1
r
2
n
g
|
1
2.2 Indirect Drivers of Soil Change
Mankind is transforming the Earth system through climate and land-use
change as well as the movement of invasive species. Soils, forming the thin
interface at the Earth's surface, interact with the atmosphere, hydrosphere,
lithosphere and biosphere, so that as they alter, soils are often also altered.
2.2.1 Changes in the Atmosphere
The composition of the atmosphere changes, due to both natural phenomena
and man's activities. The industrial era has been marked not only by increasing
atmospheric CO
2
concentrations, but also by more SO
2
, reactive N species,
organics, heavy metals and dust in the atmosphere than in pre-industrial
times.
46
Global emissions of NO, NH
3
and SO
2
are estimated to have increased
by more than a factor of 3 since the pre-industrial era, largely due to the use of
fossil fuels and agricultural production.
47
Modelling global deposition
estimates that 36-51% of all NO
y
,NH
x
,andSO
x
are deposited over the
ocean and that 50-80% of that deposited on land falls on non-agricultural
vegetation. The 'critical load' threshold, if taken to be ca. 1000 mg(N) m
22
yr
21
, is considered to be exceeded on 11% of the world's non-agricultural
vegetation. Two major consequences for soil change are increased acidification
and enhanced ecosystem productivity, with implications for the carbon cycle
and biodiversity.
47
Soils also accumulate materials from aerosol deposition occurring from both
marine and terrestrial sources as mineral aerosols (e.g. dust).
48
The major ions
contained in marine aerosols are Na
+
,K
+
,Mg
2+
,Ca
2+
,SO
4
22
and Cl
2
, and the
addition of these to soils through precipitation can be important, especially in
nutrient-depleted soils near coastal regions, but also in soils of the continental
interior. Mineral aerosols occur due to wind erosion of soils and sediments. At
one time, agricultural soils were considered to contribute as much as 50% of
