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PolyU research reveals rising soil nitrous acid emissions driven by climate and fertilisation change accelerate global ozone pollution

28 May 2025

Research Results

A study led by Prof. WANG Tao, Executive Committee member of the Research Institute for Sustainable Urban Development (RISUD), Chair Professor of Atmospheric Environment in the Department of Civil and Environmental Engineering, along with his research team, has unveiled the pivotal role that soil nitrous acid (HONO) emissions play in the increase of the ozone mixing ratio in the air and their negative impact on vegetation.

The team analysed global soil HONO emissions data from 1980 to 2016. The researchers found that soil HONO emissions have increased from 9.4 Tg N in 1980 to 11.5 Tg N in 2016. Using the chemistry-climate model to simulate the impact of these emissions on atmospheric composition, they discovered an average 2.5% rise annually in the global surface ozone mixing ratio, with localised increases reaching up to 29%. The team pointed out that soil HONO emissions are influenced by the combined effects of nitrogen fertiliser usage and climate factors such as soil temperature and soil water content, resulting in seasonal and geographical variations.

The research established a comprehensive dataset by integrating multiple variables, including climate factors like soil temperature, soil water content, and fertiliser type and application rates into the parameterisation scheme. For unquantifiable factors such as microbial activities, land use, and soil texture, the team applied diverse parameters based on latitude, longitude, and land use data of the corresponding soil samples. The findings have been published in Nature Communications.

Read the full paper: https://www.nature.com/articles/s41467-025-57161-6


Research Units Research Institute for Sustainable Urban Development

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