Environmental Engineering Reference
In-Depth Information
Table 1.
Relative contributions to total wet and dry deposition of NH
x
, NO
y
and SO
x
in the UK
from different emissions sources (%)
NH
x
dry
NO
y
dry
SO
x
dry
NH
x
wet
NO
y
wet
SO
x
wet
Power stations (%)
-
9
29
-
14
45
Road transport (%)
-
42
-
-
12
-
Livestock (%)
52
-
-
26
-
-
Shipping (%)
-
10
11
-
17
21
Import (%)
6
9
0
41
35
31
Total deposition (Gg)
66
66
51
105
82
106
Following enforcement of the International Maritime Organisation agreement
to reduce the sulphur content in marine fuel from 2.7% to 0.5%, the contribution
of international shipping emissions to sulphur deposition will be significantly reduced
by the year 2020. A number of sample deposition 'footprints' are illustrated in Figs.
emissions (with deposition highest in the south-east near the busy shipping lanes
of the English Channel); dry deposition of oxidised nitrogen from road transport
emissions in England (with deposition highest near the major motorways and
urban areas); wet deposition of sulphur from European sources (with deposition
highest over the high rainfall upland regions of Wales and the Pennines) and dry
deposition of SO
x
from a single power station (with dry deposition highest within
a few tens of km from the point source). Analysis of the contribution of UK and
international sources to the national wet and dry deposition budgets for nitrogen
and sulphur is illustrated in
Table 1.
This reveals that the power generating industry
continues to make a significant contribution to sulphur deposition, accounting for
29% of dry deposited and 45% of wet deposited sulphur. Emissions of NO
x
from
road transport in the UK account for 42% of dry deposited and 12% of wet
deposited NO
y
. Emissions of ammonia from livestock make a major contribution
to deposition of reduced nitrogen, accounting for 52% of dry and 26% of wet
deposition.
These summary statistics illustrate that whilst national policy to abate emissions
of low level sources (i.e. NO
x
and NH
3
) can be effective in reducing dry deposition
of nitrogen in the local area, efforts to control wet deposition in sensitive upland
regions require international cooperation due to the trans-boundary transport of
aerosol with emissions sources originating in Europe and from international
shipping
(Fig. 2,
right hand plot).
Further work will employ these maps to estimate the contribution of the
emissions sources to exceedance of critical loads for acid deposition and nitrogen
deposition as well as cost effective abatement measures to protect the environment
using the UK Integrated Assessment Model (Oxley et al., 2003). In addition a
comparison between footprints of deposition from point sources will be under-
taken between FRAME and more complex Eulerian models.
