A Framework for Gridded Estimates of Ammonia Emissions from Agriculture in South Asia

Tomlinson, Samuel James; Carnell, Edward James; Pearson, Clare; Sutton, Mark A.; Jain, Niveta; Dragosits, Ulrike

doi:https://doi.org/10.5194/essd-2025-75

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https://doi.org/10.5194/essd-2025-75

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09 Apr 2025

| 09 Apr 2025

Status: this preprint is currently under review for the journal ESSD.

A Framework for Gridded Estimates of Ammonia Emissions from Agriculture in South Asia

Samuel James Tomlinson, Edward James Carnell, Clare Pearson, Mark A. Sutton, Niveta Jain, and Ulrike Dragosits

Abstract. Emissions of ammonia (NH₃) from agricultural activities are a major threat to ecosystems and human health. Its quantification via emissions inventories is vital to the understanding of mitigation strategies and policy formation. South Asia, specifically the South Asian Association for Regional Cooperation (SAARC), is a global hotspot of NH₃ emissions from agriculture but also an area of great uncertainty due to a lack of data that are representative of local practices. This study presents a framework into which indigenous data can be ingested to adjust such estimates, to provide spatially distributed (0.1° × 0.1°) emissions in five agricultural sectors for improved input data for atmospheric chemistry transport models, by moving away from Tier 1 methods for emission inventories. Results incorporate data such as lower emission factors of NH₃ following the application of Urea (13 % of total nitrogen lost as NH₃-N) to provide a total estimated emission of NH₃ in the SAARC of ~6 Tg, with high values (> 5 g NH₃ m^-2 a^-1) in the Indian states Haryana, Punjab and Uttar Pradesh in the Indo-Gangetic Plain (IGP).

Received: 11 Feb 2025 – Discussion started: 09 Apr 2025

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Samuel James Tomlinson, Edward James Carnell, Clare Pearson, Mark A. Sutton, Niveta Jain, and Ulrike Dragosits

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RC1:
'Comment on essd-2025-75', Anonymous Referee #1, 13 Aug 2025 reply
This manuscript presents a comprehensive and regionally tailored framework for estimating agricultural ammonia (NH₃) emissions in South Asia, an area critical for understanding reactive nitrogen pollution, yet underrepresented in high-resolution emission inventories. The proposed framework uses a hybrid Tier 1/2 methodology, incorporating national and subnational data (e.g., fertilizer use, livestock systems, crop distribution) at a high spatial resolution of 0.1° x 0.1°. The dataset offers significant value due to its spatial granularity, region-specific emission factors (particularly for urea), and transparent methodology. This makes it a promising tool for atmospheric modeling, policy planning, and future updates. However, several issues need to be addressed to ensure that the dataset meets the standards of accessibility, reproducibility, and robustness required by ESSD.
Key Concerns:
Data Accessibility: The gridded dataset lacks direct accessibility due to the absence of a persistent identifier (e.g., DOI) or a direct link to a stable, publicly accessible data repository.

Emission Factor (EF) Consistency: The manuscript applies a uniform emission factor for urea without considering pH variability, which could affect the accuracy of NH₃ emissions estimates.

Uncertainty Analysis: The manuscript does not provide a quantitative uncertainty analysis for the final gridded product, including error propagation and uncertainty ranges, which is critical for evaluating the reliability of the estimates.

Reproducibility of Input Data: The manuscript relies on "personal communication" for certain input data, raising concerns regarding the reproducibility and transparency of the study.

Given the manuscript's valuable methodological contribution and the importance of the estimates, major revisions are required to align with ESSD's standards for data accessibility, reproducibility, and rigorous uncertainty quantification.
List of Major Revisions Required:
Data Accessibility: The manuscript should provide a persistent identifier (e.g., DOI) or a direct link to a publicly accessible and stable data repository for the 0.1° x 0.1° gridded dataset.

Uncertainty Analysis: A quantitative uncertainty analysis is needed for the final gridded estimates, including error propagation and uncertainty ranges.

Reproducibility of Input Data: Any data cited as "personal communication" must either be made available as supplementary material or detailed justifications should be provided, including a discussion of the implications for reproducibility.

Urea EF Consistency: The uniform application of the urea emission factor without accounting for pH variability should be clarified and justified, or the potential impacts on accuracy should be discussed.

Specific Comments:
Table 1 Correction: The "Maldives 1.2" formatting error in Table 1 should be corrected.

Abbreviations List: It is suggested to include a list of abbreviations to improve readability.

Metadata Enhancement: The dataset in EIDC should be accompanied by a README file, including:

Explanation of the file structure

Units of measurement

Reference to this manuscript

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Citation: https://doi.org/10.5194/essd-2025-75-RC1

Samuel James Tomlinson, Edward James Carnell, Clare Pearson, Mark A. Sutton, Niveta Jain, and Ulrike Dragosits

Data sets

Gridded emissions of ammonia (NH3) from agricultural sources in South Asia at 0.1 degrees resolution, 2015 S. J. Tomlinson et al. https://doi.org/10.5285/e0114a4f-32c2-41d9-9c2a-c46f365d4c30

Samuel James Tomlinson, Edward James Carnell, Clare Pearson, Mark A. Sutton, Niveta Jain, and Ulrike Dragosits

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Apr 2025	142	28	6	176
May 2025	71	14	5	90
Jun 2025	35	8	1	44
Jul 2025	45	19	4	68
Aug 2025	204	15	3	222
Sep 2025	817	17	3	837
Oct 2025	24	2	0	26

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Short summary

The release of ammonia into the air poses a serious risk to ecosystems and human health and so it is important to characterise where this polluting gas originates from. It is known that agriculture is an important source of ammonia (e.g. using fertilisers) and that South Asia is a global hotspot of this pollutant. It is, therefore, important to refine methods used to estimate how much ammonia is released in South Asia to be then used in advanced chemistry models for air quality assessments.


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A Framework for Gridded Estimates of Ammonia Emissions from Agriculture in South Asia

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