Peatlands represent a large global store of carbon which may be under threat from anthropogenic and climatic pressures. Factors such as lowered water-tables, nitrogen deposition, grazing and burn management are threatening Sphagnum dominated bogs which are known for their peat-forming capability. To counter this, many peatlands are being actively managed for ecosystem services, such as drinking water provision, by promoting the dominance of Sphagnum. There is therefore interest in how different vegetation types will affect dissolved organic carbon (DOC) flux, as this must be removed by water utilities during treatment. A six-week drought simulation was performed on four peatland vegetation types (Sphagnum spp., Calluna vulgaris, Molinea caerulea, Juncus effusus) and a peat soil collected from Exmoor National Park, UK. The samples were incubated and subject to different levels of drought at the 50th, 25th, 10th and 5th percentiles of the mean July/August monthly rainfall. At the end of the simulation DOC was extracted and characterised using UV, fluorescence and amenity to removal via coagulation/flocculation with ferric sulphate. All DOC sources produced significantly different amounts of DOC (Tukey HSD p&lt;0.05) in the order Molinia&gt;Juncus&gt;Calluna&gt;Sphagnum&gt;peat. The source also had a significant effect on coagulation removal efficiency (ANOVA p&lt;0.001) with Juncus DOC proving the easiest to remove whilst Sphagnum DOC was the most difficult. Sphagnum DOC had the lowest ratio of humic-like to protein-like fluorescence, which is indicative of DOC which is poorly removed by coagulation. The medium (10th percentile) drought treatment gave significant increases in DOC production (Dunnet’s test p=0.002) and specific UV absorbance at 254nm (SUVA) (Dunnet’s test p=0.009). Comparisons between the two factors (DOC source and drought) suggest DOC source to be more important than drought conditions for SUVA and overall flux. These results suggest that increased frequency of droughts due to climate change may lead to a greater flux of DOC from peatlands and that the DOC may be of higher aromaticity. The source of DOC, however, will likely be more important than the conditions under which it was produced. Catchment management programmes to support Sphagnum prevalence should lead to decreased DOC flux, although the DOC produced from Sphagnum is harder to remove via coagulation than that of vascular plants.

Dissolved organic carbon (DOC) release following drought: influence of DOC source and drought severity on drinking water treatment

249th National Meeting (2015)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.