Weathering below Irish blanket bogs and impacts on carbon dynamics

Abstract

This research investigates CO2 consumption by chemical weathering related to mineral soils and bedrock underlying peatland catchments in Ireland via measurement of major ion fluxes and runoff. Influence of peatland condition and substrate composition is investigated by comparison of catchments with varied land use and geological conditions. 
 
Research demonstrates that traditional models of blanket bog hydrology neglect the influence of substrate flow originating in underlying soil and rock. Stream baseflow from substrate sources is a significant input to catchment streams during periods of limited precipitation. The chemistry of base flow is highly influenced by the composition of the underlying material in each catchment. In periods of higher flow, when precipitation and peat flow inputs increase, dilution effects result in stream runoff more reflective of peat and rainfall chemistry.
Weathering rates in catchment substrate do not appear to be influenced by the condition of the peat in these catchments. Data show no significant difference in major ion fluxes between more intact and degraded catchments in two of the study locations: Garron and Cuilcagh. In the third location, Letterunshin, fluxes were greater in the degraded catchment compared to the intact, however, this was as a result of increased upwelling of groundwater, rather than an influence of higher weathering rates. The most significant influence on base flow runoff chemistry is the composition of the substrate material. The same is true for CO2 consumption values. Good quality peatland does not result in greater CO2 consumption values compared to those areas where degradation has occurred.

Despite this, substrate weathering in these catchments is consuming atmospheric carbon, in both the long and short term. Short term (<3ka) carbon consumption is comparable to values from Alpine catchments where weathering rates are high. In the long term (>3ka) carbon consumption is more limited due to the significance of carbonate weathering in these locations.

Date of Award	Jul 2022
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	Northern Ireland Department for the Economy
Supervisor	Raymond Flynn (Supervisor) & Donal Mullan (Supervisor)