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Greenhouse gas emissions associated with non gaseous losses of carbon - fate of particulate and dissolved carbon - SP1205

Peatlands hold the UK`s largest single store of carbon. In good condition, they can contribute to attempts to offset climate change due to fossil fuel burning, steadily drawing down CO2 from the atmosphere and storing it securely over millenia. On the other hand, if they are destabilised by poor land-management, pollution, warming or drying, they can release CO2 back to the atmosphere, exacerbating climate change. In addition, peatlands `leak` some of the carbon they hold into the rivers that drain them, as dissolved organic carbon (DOC), particulate organic carbon (POC) and inorganic carbon (IC). Although this riverine loss occurs from all peatland systems (it is the DOC which gives peaty rivers their characteristic brown colour), the amount of carbon released can increase if peatlands become unstable, for example through the gully erosion seen in areas such as the Peak District.

At present, we do not know where all the carbon transported from peatlands into rivers goes. If it is passively transported down rivers and back into sediments in lakes, reservoirs or coastal waters, this relocation of carbon from one secure store to another will not affect the climate. If, on the other hand, it is actively processed in the river system, and decomposed to CO2 or to the more powerful greenhouse gas methane, this will contribute to global warming. By establishing how much of the total river carbon flux is converted into greenhouse gases, we hope to be able to complete our understanding of the greenhouse gas balance of peatlands. We will then be better able to manage the UK`s peatlands so that they can make a positive contribution to global climate by helping to lock up greenhouse gases.

To determine the fate of the riverine carbon released from peatlands, we will study how the different forms of river carbon are processed at a range of critical locations within river systems. These range from small headwater streams, lakes and reservoirs, the confluences between streams draining peatlands and other streams with different chemistry, down to the estuary. We will also consider the role of drinking water treatment works where this carbon is removed by a variety of methods. The approaches used will combine a programme of laboratory experiments designed to identify the processes which remove DOC, POC and IC from the water, where and how fast they occur, with a parallel programme of field-based experiments and measurements at a range of peatland sites across England and Wales. Ultimately, we hope to be able to determine what proportion of each of these forms of carbon is ultimately emitted to the atmosphere as greenhouse gases, and to identify methods of managing the land, or water supply systems, which could help to reduce these emissions.
The project is designed to deliver in full the research requirements listed in the call to tender, with the following overarching goals:

1) To identify the mechanisms by which peat-derived fluvial C is cycled between different forms within the river network, focusing on DOC and POC but also considering inorganic C
2) To evaluate the influence of biological, chemical and physical conditions at different locations within the river network on fluvial C transformations
3) To quantify rates of C transfer between pools and the ultimate fate of C exported from peatlands, as a function of these chemical, physical and biological controls
4) To determine downstream changes in peat-derived fluvial C as it mixes with water of contrasting character or passes through water treatment works
5) To consider the role that climate change may have on fluvial C dynamics.

These overarching goals will be met through an integrated set of in-situ measurements, laboratory and field experiments. Work will be structured around the following specific technical objectives:

1) To identify ‘hotspots’ of peat-derived DOC, POC and IC processing in river systems
2) To identify and quantify controls on DOC processing under controlled laboratory conditions
3) To verify laboratory-derived controls on DOC processing by field experiments
4) To identify and quantify controls on POC processing under laboratory and field conditions
5) To investigate whether freshwater and estuarine POC deposition leads to CH4 emission
6) To evaluate the impact of water treatment processes on fluvial C processing
7) To integrate results and to derive GHG emission factors for peat-derived DOC, POC and IC.
Project Documents
• FRP - Final Report : Final report SP1205 2013   (3559k)
Time-Scale and Cost
From: 2010

To: 2013

Cost: £299,988
Contractor / Funded Organisations
Centre for Ecology and Hydrology
Environmental Protection