Organic soils play an important role in the fluvial carbon cycle through production and export of dissolved organic carbon (DOC) from the breakdown of plant material. However little is known about the changes in organic soil-derived fluvial DOC composition and its potential impacts on in-stream DOC breakdown dynamics. This research explores how aquatic DOC composition is influenced by land use, and how the biological utilisation of DOC may be influenced by its composition. Specifically, this research focusses on peat- rich catchments, subject to disturbance for wind farm construction to:
1. explore for how long the disturbance from wind farm development affects water chemistry in peaty catchments through analysing the long-term trends in fluvial DOC and nutrient concentrations in the draining streams;
2. assess if different wind farm-associated land uses, (construction and deforestation), exert different influences on fluvial DOC quantity and composition in peatland catchments;
3. investigate relationships between total dissolved iron (Fe) concentration [Fe] and concentrations of DOC and nutrients (phosphorus and nitrate), as this interaction may ultimately shape the DOC biodegradability during fluvial transport.
4. quantify how much DOC is biodegraded in peatland streams and what controls this.
To examine the wind farm disturbance on fluvial DOC concentration, [DOC], and spectrophotometric composition, streamwater samples from five peatland catchments draining the south of the Whitelee wind farm in Scotland were analysed monthly from 2014 to 2016. To further understand the impacts of wind farm-associated land uses, spatial and temporal variation of DOC concentration and composition were assessed between sub-catchments D-WF and D-FF within a small catchment, Drumtee. D-WF was draining the wind farm construction areas and D-FF draining the felled forestry. The concentrations of soluble reactive phosphorus, [SRP], and total oxidised nitrogen, [TON], were also measured.
Using existing and data new to this study, a long-term [DOC] increase (2006 – 2016) was observed in the Whitelee catchments since the start of wind farm development (October 2006, with the associated felling activities starting in November 2006). The increase may be a result of wind farm long-term disturbance, by generating more DOC which could be exported when discharge increases. Immediate impacts from wind farm were observed, with [DOC] and [SRP] increasing quickly after the construction began at the catchments most affected by the original wind farm development and its extension. Within Drumtee
catchment (WL13), greater mean [DOC] was observed in D-FF than D-WF. This may suggest
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Abstract
Abstract
that wind farm-related deforestation led to more peat decomposition and greater DOC release than the construction activities.
DOC is dominated by humic substances (HS), which generally can be further divided into humic acids (HAs) and fulvic acids (FAs). In WL13, DOC was less aromatic and humic than the other Whitelee catchments, with smaller SUVA410 (an indicator for more-complex aromatic C) and larger E2/E4 (an indicator for proportion of humic substances) (p