Most of the Earth’s carbon is held in the soil. Scientists used to think that the compounds that potentially contribute to climate warming would be safely stored there for centuries. However, a new experiment casts doubt on this theory.
A new study from Princeton University shows that carbon molecules can leave the soil much faster than previously thought. The findings suggest a key role for certain types of soil bacteria that can produce certain enzymes. They break down large carbon molecules and release carbon dioxide into the atmosphere.
Soil stores more carbon than all plants and the planet’s atmosphere combined. It absorbs about 20% of human carbon emissions. However, the factors affecting the accumulation and release of carbon from soil are difficult to study, which limits the relevance of climate models. The new results confirm environmental concerns that large carbon molecules may be released from the soil faster than conventional models suggest.
In an article published Jan. 27 in Nature Communications, scientists have developed soil-on-a-chip experiments. The goal is to mimic the interactions between soil, carbon compounds and soil bacteria. The researchers used synthetic transparent clay as a substitute for soil components that play the largest role in the absorption of carbon-containing molecules.
The “chip” was a modified microscope slide, or microfluidic device. It contained channels with silicone walls half a centimeter long and several times the width of a human hair (about 400 micrometers). Inlet and outlet pipes at each end of the channels allowed researchers to pump in a synthetic clay solution and then slurries containing carbon molecules, bacteria, or enzymes.
After covering the channels with clear clay, the researchers added fluorescently labeled sugar molecules to mimic the carbon-containing nutrients that seep from plant roots, especially when it rains. The experiments allowed researchers to directly observe the location of carbon compounds in clay and their movements in response to fluid flow in real time.