The Davis Strait - DCE - Nationalt Center for Miljø og Energi

202
Another matter is the contribution of greenhouse gases from combustion of
the oil produced, which depending on the amounts will contribute to the
global increase of CO2 in the atmosphere.
Emissions of SO2 and NOx contribute, among other effects, to acidification
of precipitation and may impact particularly on nutrient-poor vegetation
types inland far from the release sites. The large Norwegian field Statfjord
emitted almost 4,000 tonnes NOx in 1999. In the Norwegian strategic EIA on
petroleum activities in the Lofoten-Barents Sea area, NOx emissions even
from a large-scale scenario were considered to have an insignificant impact
on the vegetation on land. However, it was also considered that there was
no knowledge about tolerable deposition of NOx and SO2 in Arctic habitats
where nutrient-poor habitats are widespread (Anon 2003b). This lack of
knowledge also applies to the terrestrial environment of the assessment area.
Emission of black carbon (BC) from combustion is another matter especially
of concern in the Arctic, because the black particles reduce albedo from
snow and ice surfaces increasing the melt. Emission of BC is particularly
problematic when using heavy fuel oil. Use of this, however, is not permitted
in Greenland waters in relation to oil activities, and only low-sulphur (<
1.5% by weight) gas oils may be used.
The international Convention on Long-Range Transboundary Air Pollution
(LRTAP) includes all the above emissions, but when Denmark signed the
protocols covering NOx and SO2 some reservations were made in the case of
Greenland.
10.3.6 Cumulative impacts
Cumulative impacts are changes to the environment that are caused by an
action in combination with other past, present and future human actions.
Impacts from a single activity can be insignificant, but the sum of impacts
from the same activity carried out at many sites at the same time and/or
over time can develop to be significant. Cumulative impacts also include interactions
with other human activities impacting the environment, such as
hunting and fishing; moreover, climate change is also often considered in
this context (Anon 2003a).
An example could be many seismic surveys carried out at the same time in a
restricted area. A single survey will leave many alternative habitats available,
but extensive activities in several locations may exclude, for instance, baleen
whales from key habitats. This could reduce their food uptake and their
fitness due to decreased storage of the lipids needed for the winter migration
and breeding activities.
The concentration of oil discharged within produced water is low. But the
amounts of produced water from a single production platform are considerable,
and many platforms will release even more.
Bioaccumulation is an issue of concern when dealing with cumulative impacts
of produced water. The low concentrations of PAH, trace metals and
radionuclides all have the potential to bioaccumulate in fauna on the seafloor
and in the water column. This may occur in the benthic population and
subsequently be transferred to the higher levels of the food web, i.e. seabird
and marine mammals feeding on benthic organisms (Lee et al. 2005).