Ammonia is one of the most abundant alkaline gases in the atmosphere. When released into the air, it reacts with acidic compounds to form fine particulate matter known as PM2.5, which contributes to air pollution, climate effects, and human health risks. Identifying where ammonia originates from is essential for designing effective emission control strategies. Researchers have long relied on nitrogen isotope signatures, commonly expressed as δ15N, to distinguish between ammonia released from sources such as fertilizers, livestock waste, and agricultural activities. However, uncertainties during sample collection have limited the precision of these measurements.
In a new study published in Nitrogen Cycling, researchers evaluated how different acidic absorption solutions influence ammonia collection and isotope measurement accuracy. The research demonstrates that sulfuric acid provides significantly higher ammonia recovery and more stable isotope results than boric acid, which is also widely used in sampling techniques.
"Our goal was to improve the reliability of ammonia isotope measurements so researchers can better identify pollution sources," said corresponding author Chaopu Ti. "By optimizing the collection process, we can generate more precise data to support environmental management and agricultural sustainability."
To investigate the issue, the research team compared two commonly used absorption solutions, sulfuric acid and boric acid, using laboratory experiments and field sampling. They found that sulfuric acid achieved an average ammonia recovery rate exceeding 95 percent. In contrast, boric acid captured less than 90 percent of ammonia, increasing the risk of isotope distortion during sampling. The study also showed that sulfuric acid maintained stable isotope measurements even when ammonia concentrations were very low, a condition often encountered in real environmental monitoring.
Accurate isotope measurements depend heavily on preventing isotope fractionation, a process in which lighter and heavier nitrogen atoms are unevenly captured during sampling. Because sulfuric acid is a strong acid, it converts ammonia gas into stable ammonium more efficiently than weaker acids. This rapid conversion minimizes fractionation and improves measurement reliability across a wide range of sample concentrations.
The researchers further tested the optimized method in field studies involving major agricultural ammonia sources, including croplands, livestock facilities, orchards, and vegetable production systems. The results revealed clear differences in nitrogen isotope signatures among these emission sources. Cropland and livestock ammonia emissions displayed lower δ15N values compared with orchard and vegetable production systems, demonstrating the method's effectiveness for distinguishing pollution sources in real-world environments.
The findings have important implications for air pollution control and sustainable agriculture. Ammonia emissions are a leading contributor to PM2.5 formation, which is associated with respiratory disease and reduced visibility in many regions. Improved source identification can help policymakers design targeted emission reduction strategies, optimize fertilizer use, and reduce environmental nitrogen losses.
"This work provides a practical and accurate approach for tracking ammonia emissions in the atmosphere," Ti said. "Better identification of emission sources allows for more precise management practices that protect air quality and environmental health."
Beyond air pollution control, the improved method may also help scientists better understand nitrogen cycling in agricultural ecosystems. Nitrogen plays a central role in soil fertility and crop productivity, but excessive nitrogen losses can harm ecosystems and contribute to climate change. Reliable isotope analysis provides a powerful tool for studying nitrogen transformations and evaluating mitigation strategies.
The researchers conclude that sulfuric acid absorption offers a robust and efficient approach for measuring ammonia isotope signatures across diverse environmental conditions. By improving data accuracy, the method provides stronger scientific support for reducing ammonia emissions and managing nitrogen pollution at regional and global scales.
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Journal Reference: Peng L, Ti C, Bai X, Li M, Wang X, et al. 2026. The effect of acidic solutions on the determination of the natural abundance of nitrogen isotopes in ammonia. Nitrogen Cycling 2: e005 doi: 10.48130/nc-0025-0017
https://www.maxapress.com/article/doi/10.48130/nc-0025-0017
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About Nitrogen Cycling :
Nitrogen Cycling (e-ISSN 3069-8111) is a multidisciplinary platform for communicating advances in fundamental and applied research on the nitrogen cycle. It is dedicated to serving as an innovative, efficient, and professional platform for researchers in the field of nitrogen cycling worldwide to deliver findings from this rapidly expanding field of science.
