Study Reveals: Climate Change and Fertilization Boost Soil Nitrous Acid Emissions, Intensifying Global Ozone Pollution

Ozone pollution is an urgent issue. It impacts human health, crops, and contributes to global warming. While many people think of factories and cars as the main culprits, new studies show that our soils also play a significant role.

Researchers at Hong Kong Polytechnic University (PolyU) have dug into data from 1980 to 2016 about soil emissions of nitrous acid (HONO). Their work reveals how these emissions are linked to rising ozone levels that affect air quality and vegetation.

Dr. Yanan Wang, a lead author of the study published in Nature Communications, explains that certain farming practices, especially the use of fertilizers, can release various gases from soil into the atmosphere. In fact, soil HONO emissions may contribute to as much as 80% of atmospheric HONO levels.

HONO interacts with other pollutants to produce ozone, particularly by raising levels of nitrogen oxides (NO_x), which are precursors to ozone formation.

Under the guidance of Prof. Tao Wang, the PolyU team compiled a comprehensive dataset on these emissions. They combined multiple factors—like soil temperature, moisture, and fertilizer types—into a new model that accurately predicts the influence of soil emissions on air quality.

Data shows that from 1980 to 2016, soil HONO emissions have risen from 9.4 to 11.5 Tg N. Using their chemistry-climate model, the researchers observed an annual average increase of 2.5% in global surface ozone, with some areas experiencing increases of up to 29%.

This trend poses several problems: more ozone can harm plant health, lower crop yields, and lessen vegetation’s ability to absorb CO₂, worsening climate change.

Interestingly, the impact of soil HONO emissions hits hardest in regions with lower pollution levels. In these areas, ozone formation relies heavily on local nitrogen oxides, meaning increases in HONO can lead to more substantial ozone growth.

According to recent statistics, over the past few years, many regions have seen a decline in pollution from human activities. As this trend continues, areas previously less affected may experience a shift toward being more “sensitive” to soil emissions.

Prof. Wang highlights the urgency: “Climate change and increased fertilizer use will lead to higher HONO emissions. This could undermine the progress made by reducing industrial pollution. To achieve sustainable development, it’s essential to manage soil emissions effectively.”

The researchers also emphasized the importance of continuing to expand the global observational network for soil HONO emissions. They seek a deeper understanding of how microbes in the soil contribute to these emissions. This knowledge could help develop better farming strategies that maintain productivity while reducing harmful emissions.

Ozone pollution is an intricate issue tied to many factors, including soil health and agricultural practices. As the world grapples with climate change, it’s vital to address all aspects of pollution, not just those that are immediately visible.

For more detailed information, refer to the complete study by Yanan Wang et al. in Nature Communications [DOI: 10.1038/s41467-025-57161-6](https://dx.doi.org/10.1038/s41467-025-57161-6).

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