|dc.description.abstract||Many onshore windfarms in Scotland are being built on peatlands. As a
consequence, the impacts of development activities on the peatland and
downstream environments are an important emerging issue. For example, a
reduction of the quantity of carbon (C) stored in the peatland and increased
phosphorus (P) and nitrogen (N) concentrations in streams may cause changes
in the peatland carbon sink strength and aquatic carbon emissions, and
exceedance of EU Water Framework Directive (WFD) P threshold values,
respectively. To further assess the impacts from peatland-based windfarm
development, the following four research questions were posed:
1. Which specific development activities have the greatest impact on
concentrations of C, N and P in streams? How long does it take for C,
N and P concentrations to return to baseline conditions?
2. Which specific windfarm development activities caused the greatest
aquatic export of carbon and nutrients?
3. What are the controls on concentration and export of aquatic C, N and
P in streams draining peatland developments?
4. How effective are site-derived adsorbent materials and an iron ochre at
preventing phosphorus from entering upland streams on peatland?
Presented in this thesis, are the results from 3-weekly spatial streamwater
sampling of 18 sub-catchments (ranging 0.03 - 12 km2) – from October 2011 to
March 2013 – which covers the majority of the peatland-based development
and one year beyond, of the Whitelee windfarm Phase 2 extension 16 km south
of Glasgow, Scotland.
Dissolved and particulate organic carbon (DOC/POC), soluble reactive
phosphorus (SRP) and total oxidised nitrogen (TON) concentrations were
measured and exports were calculated from stream gauging.
The spatial catchment controls on stream water chemistry were investigated
through a multiple linear regression analysis. Fraction of sub-catchment area
that was subject to forest felling was found to be significantly positively
correlated with concentrations and exports of DOC, POC, SRP and TON; with
TON specifically by felling that had occurred more than one year previously.
Density of tracks / cable trenches / turbines, and fraction non-forested area in
general exerted a negative control on exports. Evidence of SRP attenuation
processes in addition to dilution were found in some streams. While neither
river sediment nor track or cable trench gravels were very effective at
removing SRP, from the results of batch adsorption experiments, a sample of
mineral subsoil was. SRP was attenuated in areas where there was a greater
proportion of peaty gleys, in the riparian zone along the main stream, and the
outcome of the batch adsorption experiments points to attenuation of SRP onto
mineral subsoils, where present.
Comparing long-term (seven year) time series of the original Whitelee
windfarm directly north of the site, with the extension site (this study) it was
possible to estimate the time required for recovery to pre-development
concentrations. Mean annual [DOC] increased to 31.4 mg l-1 during
development of the extension site. While it took five years for the DOC to
recover at the original site, in the year following development at the extension
site, mean annual [DOC] was still above the baseline. Mean annual [POC]
increased to a maximum of 2.6 mg l-1 during development of the extension site,
and as with the original site it returned to the baseline the year following
development. The mean annual [SRP] increased to a maximum of 50.5 μg l-1
during development, leading to a reduction in water quality from ‘good’ to
‘moderate’ based on comparison with Environmental Quality Standards
(EQS). It took four years for the SRP to recover at the original site, and mean
annual [SRP] was still above baseline at the extension site in the year following
The streamwater C, N and P has not been measured as close to, and for such a
range of, windfarm development activities. This research has demonstrated
links between windfarm development, forest felling in particular, and
increased concentrations and exports of DOC, POC, SRP and TON in streams.
While the increases were localised within the site itself, investigation of
attenuation processes point to peaty gley soils along the main stream, and
tracks, cable trenches and turbines – and their associated settling lagoons and
silt fences – as potentially mitigating the increased dissolved carbon and
Outcomes of this research are suggested improvements to the guidance for
developing peatlands, especially with regards to monitoring streamwater
carbon for a sufficient period post-development, and for the removal of brash
on peat soils. Further research could investigate the use of adsorption
materials to mitigate phosphorus mobilisation from brash sources to streams,
over a time scale of at least two years at the field scale. Laboratory-based
environmental fate studies of the increased streamwater carbon could
investigate the rates of CO2 efflux with time and with varying concentrations
of nutrients, which would help to improve the Scottish Government's carbon
calculator estimates of carbon loss from peatland-based windfarm