wAbstract
@What role does mineralized organic C and sulfide oxidation play
in weathering of silicate minerals in deep groundwater aquifers?
In this study, how H2CO3,
produced as a result of mineralization of organic matter during
groundwater transport, affects silicate weathering in the saturated
zone of the mineral soil along a 70 m-long boreal hillslope is
demonstrated. Stream water measurements of base cations and ย18O
are included to determine the importance of the deep groundwater
system for downstream surface water. The results suggest that
H2CO3 generated from
organic compounds being mineralized during the lateral transport
stimulates weathering at depths between 0.5 and 3 m in the soil.
This finding is indicated by progressively increasing concentrations
of base cations-, silica- and inorganic C (IC) in the groundwater
along the hillslope that co-occur with decreasing organic C (OC)
concentrations. Protons derived from sulfide oxidation appear
to be an additional driver of the weathering process as indicated
by a build-up of SO42- in the
groundwater during lateral transport and a ย34S๑ value
of +0.26-3.76๑ in the deep groundwater indicating S inputs from
pyrite. The two identified active acids in the deep groundwater
are likely to control the base-flow chemistry of streams draining
larger catchments (1 km2) as evident by ย18O
signatures and base cation concentrations that overlap with that
of the groundwater.x
1. Introduction
2. material and methods
@2.1. Soil-water and deep groundwater sampling along the hillslope
gradient
@2.2. Stream water and precipitation sampling
@2.3. Analysis
@2.4. Conceptual view of the studied hillslope system
@2.5. Statistics
3. Result
@3.1. Groundwater chemistry and weathering processes
@3.2. Deep groundwater and its impact on base-flow chemistry
4. Discussion
@4.1. Chemical weathering processes in deep groundwater
@4.2. Groundwater chemistry and its importance for stream chemistry
@4.3. Implications for the conceptual view of chemical weathering
Acknowledgements
References