Reservoirs are hotspots of nitrogen cycling in peatland catchments

Abstract

This study presents input–output budgets of total dissolved nitrogen (TDN), dissolved organic N (DON) and dissolved inorganic N (DIN) for a reservoir in a peatland catchment in the south Pennines (UK). This site receives high levels of atmospheric inorganic N deposition, in the range of 26 kg N ha−1 yr−1. The results show that the reservoir retains ~21 to 31% of the annual TDN input (8806 ± 741 kg N). Approximately 39 to 55% of DON (3782 ± 653 kg N) and 6 to 13% of DIN (5024 ± 349 kg N) were retained/processed. A long water retention time (104 days), average annual pH of 6.5, high concentrations of DIN in the reservoir water and a deep water column suggest that denitrification is potentially a key mechanism of N retention/removal. The results also demonstrate that DON is potentially photodegraded and utilized within the reservoir, particularly during the summer season when 58 to 80% of DON input (682 ± 241 kg N) was retained, and a net export of DIN (~34 kg N) was observed. The findings therefore suggest that DON may play a more crucial role in the biogeochemistry of peat‐dominated acid sensitive upland freshwater systems than previously thought. Reservoirs, impoundments and large lakes in peatland catchments may be important sites in mediating downstream N transport and speciation. Copyright © 2016 John Wiley & Sons, Ltd.

Fluvial organic carbon composition and concentration variability within a peatland catchment—Implications for carbon cycling and water treatment

“…For further information on the reservoir inlet (KR, BC, and WC) and outlet (VH and KRO) sampling points see Stimson, Allott, Boult, and Evans (). Additionally, the study was conducted alongside work to understand nitrogen dynamics (see Edokpa, Evans, & Rothwell, , ). To capture changes throughout the catchment, three locations were considered: (a) the major feeder stream to the reservoir draining a large area of blanket peat, (b) the reservoir, and (c) the 10‐km pipe from the reservoir to the water treatment works.…”