Abstract
Hydrogen (H2) gas acts as a secondary greenhouse gas, indirectly
increasing the lifetime of methane in the atmosphere by competing for
hydroxyl radicals that would otherwise react with methane to convert it
to carbon dioxide and water. Soils are a major sink for atmospheric
hydrogen, so it is important to predict hydrogen uptake at regional
scales to understand its potential impact on atmospheric chemistry.
Process-based models have been developed that estimate soil hydrogen
uptake, primarily focusing on abiotic factors, such as soil moisture and
temperature. Previous models relied on accurate porosity data, limiting
their applicability for regional simulations. Later approaches used soil
texture to estimate moisture influence but neglected soil organic
carbon’s role in controlling microbial activity. Our study introduces a
new model of hydrogen release and uptake by soils (HORUS) for use at
field to global scale, shifting from existing models by including the
pivotal role of soil organic carbon in controlling microbial activity.
Leveraging the power of established soil organic matter models to
simulate potential microbial activity, we integrate soil moisture,
temperature and potential microbial activity into the model. We evaluate
the performance of HORUS using measurements from four studies of soil
hydrogen uptake and compare predictions to established models. Our
approach improves estimates of hydrogen deposition velocity (uptake
rates) across datasets. Results demonstrate that incorporating potential
microbial activity significantly improves the accuracy and
transferability of hydrogen deposition velocity estimates between
different soil types, underscoring the vital role of soil organic matter
and microorganisms in this process.