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Title: Investigating carbon flux variability in subtropical peat soils of the Everglades using hydrogeophysical methods†
Date: 23-Jul-2014
Category: Article
Source/Author: WILEY ONLINE LIBRARY


Keywords:

GPR;
methane flux;
hydrogeophysics;
biogenic gas

Abstract

The spatial and temporal variability in accumulation and release of greenhouse gases (mainly methane and carbon dioxide) to the atmosphere from peat soils remains very uncertain. The use of near surface geophysical methods such as Ground Penetrating Radar (GPR) has proven useful during the last decade to expand scales of measurement as related to in-situ gas distribution and dynamics beyond traditional methods (i.e. gas chambers). However, this approach has focused exclusively on boreal peatlands, while no studies in subtropical systems like the Everglades using these techniques exist. In this paper GPR is combined with gas traps, time lapse cameras, gas chromatography, and surface deformation measurements to explore biogenic gas dynamics (mainly gas build-up and release) in two locations in the Everglades. Similar to previous studies in northern peatlands, our data in the Everglades show a statistically significant correlation between: 1) GPR estimated gas content and gas fluxes; 2) GPR estimated gas content and surface deformation; and 3) atmospheric pressure and both GPR estimated gas content and gas flux. From these results several gas releasing events ranging between 33.8 and 718.8 mg CH4 m−2 d−1 were detected as identified by: 1) decreases in GPR estimated gas content within the peat matrix; 2) increases in gas fluxes captured by gas traps and time-lapse cameras; 3) decreases in surface deformation. Furthermore, gas releasing events corresponded to periods of high atmospheric pressure. Changes in gas accumulation and release were attributed to differences in seasonality and peat soil type between sites. These results suggest that biogenic gas releases in the Everglades are spatially and temporarily variable. For example flux events measured at hourly scales were up to threefold larger when compared to daily fluxes, therefore suggesting that flux measurements decline when averaged over longer time-spans. This research therefore questions what the appropriate spatial and temporal scale of measurement is necessary to properly capture dynamics of biogenic gas release in subtropical peat soils.

onlinelibrary.wiley.com/doi/10.1002/2013JG002601/abstract



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