Southern California dryland soil sampled for nitrogen deposition study. Credit: Johann Püspök/UCR
New UC Riverside research suggests nitrogen released by gas-powered machines causes dry soil to let go of carbon and release it back into the atmosphere, where it can contribute to climate change.
Industrial manufacturing, agricultural practices, and significantly, vehicles, all burn fossil fuels that release nitrogen into the air. As a result, levels of nitrogen in Earth’s atmosphere have tripled since 1850. The research team wanted to understand whether this extra nitrogen is affecting soil’s ability to hold onto carbon and keep it from becoming a greenhouse gas.
“Because nitrogen is used as a fertilizer for plants, we expected additional nitrogen would promote plant growth as well as microbial activity, thereby increasing carbon put into soils,” said Peter Homyak, study co-author and assistant professor in UCR’s Department of Environmental Sciences.
In dryland soil, the type that covers much of Southern California, this is not what they saw.
Instead, the team found that under certain conditions, extra nitrogen causes dryland soil to acidify and leach calcium. Calcium binds to carbon, and the two elements then leave the soil together. This finding is detailed in the journal Global Change Biology.
To obtain their results, the research team sampled soil from ecological reserves near San Diego and Irvine that have been fertilized with nitrogen in long-term experiments. This allowed them to know precisely how much nitrogen was being added, and account for any effects they observed.
In many cases, nitrogen can affect biological processes that in turn influence how soil stores carbon. Such processes include the fueling of plant growth, as well as slowing down the microbes that…
2023-02-01 05:18:58 Soil tainted by air pollution expels carbon
Post from phys.org Air pollution is a growing concern in cities across the world. Scientists are studying how air pollution affects the environment, and one surprising discovery is that soil itself can be tainted by air pollution and expel carbon.
Researchers from the University of Washington published a paper in Nature: Climate Change demonstrating that air pollutants from the burning of fossil fuels can affect the way soil particles interact with water and the amount of carbon dioxide that is emitted.
The team examined the soil of three different continents: Asia, Europe and North America. They found that soil particles in locations with high levels of air pollution had more oxygen lingering on their surfaces, resulting in water being repelled instead of absorbed. This reaction caused a ‘hydrophobic’ response, resulting in soil particles expelling more carbon dioxide.
This unexpected reaction suggests that climate models should take into consideration the role that urban air pollution plays in adding to the carbon levels in soil. The study’s authors noted that regions with higher levels of air pollution include some of the most densely populated cities on the planet, and the findings could change the way we understand the global carbon cycle.
Most of the soil carbon expelled from air pollution is released in the form of carbon dioxide, a major contributor to climate change. The findings underscore the critical importance of addressing air pollution, especially in urban areas and regions that are faced with higher levels of contamination.
As the world continues to focus on ways to limit climate change, it is essential to recognize how both natural and man-made pollutants can contribute to higher levels of emissions, and take steps to reduce emissions from these sources. Studies such as this one provide a valuable insight into how air pollution is impacting our environment and may help decision-makers craft strategies to reduce the amount of air pollution entering our soil.
