TY - JOUR
T1 - Impacts of Shallow Geothermal Energy Production on Redox Processes and Microbial Communities
AU - Bonte, Matthijs
AU - Roling, Wilfred F. M.
AU - Zaura, Egija
AU - van der Wielen, Paul W. J. J.
AU - Stuyfzand, Pieter J.
AU - van Breukelen, Boris M.
PY - 2013
Y1 - 2013
N2 - Shallow geothermal systems are increasingly being used to store or harvest thermal energy for heating or cooling purposes. This technology causes temperature perturbations exceeding the natural variations in aquifers, which may impact groundwater quality. Here, we report the results of laboratory experiments on the effect of temperature variations (5–80 °C) on redox processes and associated microbial communities in anoxic unconsolidated subsurface sediments. Both hydrochemical and microbiological data showed that a temperature increase from 11 °C (in situ) to 25 °C caused a shift from iron-reducing to sulfate-reducing and methanogenic conditions. Bioenergetic calculations could explain this shift. A further temperature increase (>45 °C) resulted in the emergence of a thermophilic microbial community specialized in fermentation and sulfate reduction. Two distinct maxima in sulfate reduction rates, of similar orders of magnitude (5 × 10–10 M s–1), were observed at 40 and 70 °C. Thermophilic sulfate reduction, however, had a higher activation energy (100–160 kJ mol–1) than mesophilic sulfate reduction (30–60 kJ mol–1), which might be due to a trade-off between enzyme stability and activity with thermostable enzymes being less efficient catalysts that require higher activation energies. These results reveal that while sulfate-reducing functionality can withstand a substantial temperature rise, other key biochemical processes appear more temperature sensitive.
AB - Shallow geothermal systems are increasingly being used to store or harvest thermal energy for heating or cooling purposes. This technology causes temperature perturbations exceeding the natural variations in aquifers, which may impact groundwater quality. Here, we report the results of laboratory experiments on the effect of temperature variations (5–80 °C) on redox processes and associated microbial communities in anoxic unconsolidated subsurface sediments. Both hydrochemical and microbiological data showed that a temperature increase from 11 °C (in situ) to 25 °C caused a shift from iron-reducing to sulfate-reducing and methanogenic conditions. Bioenergetic calculations could explain this shift. A further temperature increase (>45 °C) resulted in the emergence of a thermophilic microbial community specialized in fermentation and sulfate reduction. Two distinct maxima in sulfate reduction rates, of similar orders of magnitude (5 × 10–10 M s–1), were observed at 40 and 70 °C. Thermophilic sulfate reduction, however, had a higher activation energy (100–160 kJ mol–1) than mesophilic sulfate reduction (30–60 kJ mol–1), which might be due to a trade-off between enzyme stability and activity with thermostable enzymes being less efficient catalysts that require higher activation energies. These results reveal that while sulfate-reducing functionality can withstand a substantial temperature rise, other key biochemical processes appear more temperature sensitive.
U2 - 10.1021/es4030244
DO - 10.1021/es4030244
M3 - Article
SN - 0013-936X
VL - 47
SP - 14476
EP - 14484
JO - Environmental science & technology
JF - Environmental science & technology
IS - 24
ER -