Combined use of geophysical and geochemical methods to assess areas of active, degrading and restored blanket bog

Laura Mcanallen,Rory Doherty,Shane Donohue,Panagiotis Kirmizakis,Carlos Mendonça

doi:10.1016/j.scitotenv.2017.11.300

Laura Mcanallen, Rory Doherty + Show 3 more

Open Access

https://doi.org/10.1016/j.scitotenv.2017.11.300

Copy DOI

Abstract

Here we combine the use of geo-electrical techniques with geochemical analysis of the solid and liquid phase to determine subsurface properties and general peatland health. Active, degrading and restored peat locations were analysed from the same blanket bog site (ensuring they were under the same environmental conditions, such as rainfall and temperature) at the Garron Plateau, Northern Ireland. A normalized chargeability (ratio of resistivity (inverse of conductivity) and chargeability) profile was compared with organic composition analysis of the solid and liquid phases from active, degrading and restored locations. Results show that the degrading location is undergoing high rates of decomposition and loss of organic matter into the interstitial water, whereas the opposite is true for the active location. The restored peat is showing low rates of decomposition however has a high concentration of organic material in the porewater, primarily composing long chain aliphatic compounds, sourced from vascular plants. The ingression of vascular plants permits the diffusion of oxygen via roots into the subsurface and supports the oxidation of phenols by phenol oxidase, which produces phenoxy radicals and quinones (CO double bonds). This production of conjugated quinones, which are characterized by a CO double bond, in the aerated degrading and restored locations, increase the polarity, cation exchange capacity, and the normalized chargeability of the peat. This higher chargeability is not evident in the active peat due to decreased aerobic decomposition and a domination of sphagnum mosses.

Highlights

Ombrotrophic peatlands are valuable yet vulnerable ecosystems whose ecology and degradation status are closely linked to the movement and storage of water (Rezanezhad et al, 2016)
There is a low resolution of the data at the surface as a result of the relatively large spacing between electrodes, we expected to see greater differences in Induced Polarization (IP) sections
The opposite was true for the active location, which was shown to have low decomposition rates and low concentrations of organic material in the porewater, indicating a more stable and closed system

Summary

Introduction

Ombrotrophic peatlands are valuable yet vulnerable ecosystems whose ecology and degradation status are closely linked to the movement and storage of water (Rezanezhad et al, 2016). L. McAnallen et al / Science of the Total Environment 621 (2018) 762–771 accumulating bogs form natural organic matter (NOM) by the humification of plants under water saturated and anoxic conditions. Drainage introduces oxygen into the previously anoxic environment, causing rapid aerobic decomposition and loss of organic carbon. Drainage can allow the ingression of oxygen to the subsurface promoting aerobic degradation of organic matter. One of the dominant mechanisms proposed for this aerobic degradation is the ‘enzymatic latch hypothesis’ (Freeman et al, 2001) where the normally constrained phenol oxidase enzyme is able to freely degrade in aerated conditions. The ingression of vascular plants due to overgrazing can influence oxygen availability and enzymatic activity by allowing oxygen diffusion to deep roots (Romanowicz et al, 2015)

Methods

Results

Conclusion