# Evolving global oceanic nitrogen deposition under future emission pathways and responses to nitrogen emission reductions

Jialin Deng, Yixin Guo, Ni Lu, Xingpei Ye, Yuanhong Zhao, Jiayu Xu, Lei Liu, Lin Zhang

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## To cite this version:

Jialin Deng, Yixin Guo, Ni Lu, Xingpei Ye, Yuanhong Zhao, et al.. Evolving global oceanic nitrogen deposition under future emission pathways and responses to nitrogen emission reductions. Nitrogen Cycling, 2026, 2 (1), pp.e013. 10.48130/nc-0025-0025. hal-05502969

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Submitted on 3 Mar 2026

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# Evolving global oceanic nitrogen deposition under future emission pathways and responses to nitrogen emission reductions

Jialin Deng¹, Yixin Guo², Ni Lu¹, Xingpei Ye¹, Yuanhong Zhao³, Jiayu Xu⁴, Lei Liu⁵ and Lin Zhang¹*

Received: 3 November 2025

Revised: 20 December 2025

Accepted: 30 December 2025

Published online: 29 January 2026

## Abstract

Atmospheric nitrogen deposition is an important external nutrient source to the global ocean, with significant impacts on marine ecosystems and biogeochemical cycles. However, its future evolution under changing anthropogenic emissions and the consequences for ocean productivity and climate-relevant gases such as N₂O remain unclear. Here, the global atmospheric chemistry model GEOS-Chem is used to evaluate changes in global oceanic nitrogen deposition between 2015 and 2050 under three representative future emission scenarios and to assess their responses to multiple levels of NH₃ and NOₓ emission reductions. Global oceanic nitrogen deposition is projected to change by -24% to +6% between 2015 and 2050, with a substantially increasing share contributed by reduced nitrogen across all scenarios. There is strong chemical compensation between reduced and oxidized nitrogen deposition: reducing emissions of one species (e.g., NH₃ or NOₓ) can enhance dry deposition of the other to the oceans, particularly in coastal regions, suggesting that joint control of NH₃ and NOₓ is required to reduce total nitrogen deposition effectively. The potential ocean productivity induced by nitrogen deposition may decrease from 290 Tg C in 2015 to 222 Tg C under SSP1-RCP2.6, or increase to 306 Tg C under SSP3-RCP7.0 by 2050, while concurrent changes in oceanic N₂O emissions largely offset the associated climatic effects. These results highlight overlooked impacts of future climate mitigation and nitrogen abatement on marine ecosystems via altered atmospheric nitrogen deposition, and call for more holistic assessments of nitrogen impacts across the air, terrestrial, and ocean systems.

**Keywords:** Nitrogen emissions, Nitrogen deposition, CMIP6 emissions, Oceanic deposition, Ammonia

## Highlights

* Global oceanic nitrogen deposition is projected to change by -24% to +6% between 2015 and 2050, with a notable increase in the contribution of NH₃-N across all scenarios.

* Reducing emissions of a single species (e.g., NH₃ or NOₓ) suppresses the dry deposition of the other due to gas-particle interconversion, revealing complex chemical interactions and the need for coordinated NH₃ + NOₓ controls.

* Future changes in nitrogen deposition are projected to affect both ocean primary productivity and N₂O emissions, highlighting a trade-off in biogeochemical feedbacks.

<footnote>* Correspondence: Lin Zhang (zhanglg@pku.edu.cn)
Full list of author information is available at the end of the article.</footnote>
**Graphical abstract**

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**Introduction**

Atmospheric nitrogen deposition is a key component of the global nitrogen cycle, acting as a sink for reactive nitrogen (Nr) in the atmosphere and as an external nutrient source for both terrestrial and marine ecosystems[1–3]. A substantial fraction of global nitrogen deposition enters the ocean, where it provides additional reactive nitrogen to phytoplankton and can influence marine productivity and the global carbon cycle[4–6]. Previous studies have suggested that anthropogenic nitrogen deposition has already made a measurable contribution to marine new production and the uptake of atmospheric CO₂[5,7], although recent work points to large regional variations and substantial uncertainties associated with biogeochemical feedbacks and co-limitation by other nutrients such as phosphorus and iron[8,9]. Understanding the spatial variations and future evolution of atmospheric nitrogen deposition to oceans will help better constrain the interconnected carbon and nitrogen cycles.

Oceanic nitrogen deposition is ultimately controlled by reactive nitrogen emissions from both anthropogenic activities (e.g., fossil fuel combustion, agricultural fertilizer use, and livestock production) and natural sources (e.g., soils, lightning, and the ocean itself)[10–12]. These sources emit nitrogen primarily in reduced (NH₃) and oxidized (NOₓ) forms and participate in atmospheric chemical processes that lead to the formation of nitrogen-containing aerosols, with implications for climate and air quality[13–17]. NH₃ rapidly partitions with acidic species to form ammonium aerosols (NH₄⁺), while NOₓ is oxidized to gas-phase nitric acid (HNO₃) and particulate nitrate (NO₃⁻). The reduced nitrogen family is collectively referred to as NHₓ (NH₃ + NH₄⁺), and the oxidized family as NOᵧ (including NOₓ, HNO₃, NO₃⁻, and related species)[18,19]. These gases and aerosols are eventually removed by wet and dry deposition, delivering NHₓ and NOᵧ to the surface ocean.

Over the past decades, anthropogenic Nr emissions have undergone strong regional trends driven by changes in energy use, agricultural activities, and environmental policies, leading to notable trends and variability in oceanic nitrogen deposition[17,20,21]. Recent modelling studies have shown that global oceanic NHₓ deposition increased by 89% during 1970–2018, while NOᵧ deposition increased by 43% during 1970–2010 and then declined by 6% over

2010–2018 in response to anthropogenic NOₓ controls in developing countries[20]. Future emission pathways under different socioeconomic and climate-mitigation scenarios are expected to substantially alter atmospheric nitrogen deposition. Most existing studies on future nitrogen deposition have focused on global land-atmosphere budgets or regional air quality and ecosystem impacts[19,22,23], whereas comprehensive assessments of oceanic nitrogen deposition under shared socioeconomic pathways and its implications for marine productivity and climate-relevant gases such as N₂O remain limited.

Meanwhile, there is growing policy interest in managing nitrogen pollution to achieve cleaner air, reduced biodiversity loss, and co-benefits for the climate[24–27]. Recent work has highlighted that ambitious nitrogen interventions can yield substantial benefits for PM₂.₅ air quality, biodiversity protection, and greenhouse gas mitigation[28–32]. Stringent nitrogen controls may also alter the strength and spatial distribution of nitrogen deposition to the oceans. Yet, it is still unclear how different combinations of NH₃ and NOₓ emission reductions would propagate through the atmosphere to affect oceanic nitrogen deposition, and to what extent single-pollutant vs multi-pollutant control strategies differ in their impacts on oceanic nitrogen deposition.

In this study, the knowledge gaps are addressed using the global atmospheric chemistry transport model GEOS-Chem to: (1) quantify changes in global and regional oceanic nitrogen deposition between 2015 and 2050 under three CMIP6 future emission scenarios; (2) disentangle the atmospheric mechanisms by which NH₃ and NOₓ emissions jointly determine NHₓ and NOᵧ deposition to the oceans; and (3) estimate the potential impacts of these changes on ocean primary productivity and oceanic N₂O emissions following an established biogeochemical framework[5]. By focusing specifically on the chemical compensation between NHₓ and NOᵧ and its consequences for oceanic nitrogen inputs, it is found that the coordinated and joint control of NH₃ and NOₓ is essential for effectively reducing total nitrogen deposition to the oceans. The results provide an earth-system-scale perspective on how future emission mitigation and nitrogen management strategies may unintentionally reshape marine ecosystems.
# Methods

## Model and scenario settings

The Goddard Earth Observing System Chemistry (GEOS-Chem) 3-D global atmospheric chemistry transport model, version 12.9.3, was used to simulate global nitrogen deposition for 2015 and 2050 under various future emission scenarios. The model is driven by NASA MERRA-2 meteorological data, with a horizontal resolution of 2° × 2.5° and a vertical resolution of 47 layers extending from the surface to 0.01 hPa. The model employs a full chemistry mechanism that incorporates tropospheric ozone, nitrogen oxides, hydrocarbons, and aerosol chemistry[33].

GEOS-Chem links surface emissions of NH₃ and NOₓ to their deposition through coupled chemical and physical processes. Emitted NH₃ undergoes rapid gas-particle partitioning with sulfate and nitrate to form ammonium aerosols (NH₄⁺), while NOₓ is oxidized by OH, O₃, and HO₂ to produce nitric acid (HNO₃) and particulate nitrate (NO₃⁻). Heterogeneous reactions, including N₂O₅ hydrolysis and aerosol-phase oxidation, further regulate the partitioning between oxidized nitrogen species. These chemical transformations, along with interactions with other atmospheric constituents, determine the forms and distributions of nitrogen available for deposition. Nitrogen is subsequently removed from the atmosphere via wet and dry deposition. Wet deposition, including convective scavenging, large-scale precipitation removal, and rainout, follows the parameterization of Liu et al.[34], whereas dry deposition of gases and aerosols is calculated using the standard resistance-in-series model[35].

Anthropogenic emissions are from the Coupled Model Intercomparison Project Phase 6 (CMIP6) emission inventory, which includes NH₃, NOₓ, black carbon (BC), methane (CH₄), carbon monoxide (CO), organic carbon (OC), sulfur dioxide (SO₂), and various VOC species emissions from agricultural, energy, transportation, and industry sectors. To project future nitrogen deposition under representative emission pathways, three scenarios are selected, including SSP1-RCP2.6 (abbreviated as SSP126; low-emission scenario), SSP3-RCP7.0 (abbreviated as SSP370; high-emission scenario), and SSP4-RCP3.4 (abbreviated as SSP434; moderate-emission scenario). SSP126 represents a sustainable development pathway, assuming strict global emission-reduction policies that significantly lower greenhouse gas and NOₓ emissions[36]. SSP370 reflects rapid economic growth with insufficient environmental policies, leading to medium-to-high emissions[37]. SSP434 represents a moderate mitigation pathway with balanced climate and development goals, falling between SSP126 and SSP370[38]. Natural emission sources, including NOₓ from soil and lightning, NH₃ emissions from seabirds and soils, and biomass burning emissions from the GFED4 fire database, are fixed at 2015 levels in future simulations[39,40].

A baseline simulation was conducted with the 2015 anthropogenic emissions, and three simulations with future-scenario (2050) emissions (SSP126, SSP434, and SSP370). The year 2015 was selected as the baseline year to align with the historical period of the CMIP6 emission inventories. Sensitivity experiments are conducted to evaluate the individual and combined effects of reductions in anthropogenic NH₃ and NOₓ emissions on nitrogen deposition. Emissions of NH₃ and NOₓ are reduced by 25%, 50%, and 100% as described in an earlier study[30]. Each simulation is run for one year and four months, with the first four months as a spin-up to achieve equilibrium. To focus on the impacts of changing anthropogenic emissions, all simulations are driven by the same meteorological fields, fixed for 2015.

Here, to characterize regional nitrogen deposition in both coastal and open oceans, four representative coastal regions (China coast, Indian coast, European coast, and US coast) and four adjacent open ocean regions (North Pacific Ocean, North Indian Ocean, East Atlantic Ocean, and Western Atlantic Ocean) are focused on as shown in Supplementary Fig. S1 following Liu et al.[20]. The simulated wet deposition fluxes of NH₄⁺ and NO₃⁻ are validated in the 2015 baseline scenario against observational data from available global monitoring networks, including the National Trends Network (NTN, http://nadp.slh.wisc.edu/data/NTN), the Atmospheric Integrated Research Monitoring Network (AIRMoN, https://nadp2.slh.wisc.edu/data/AIRMoN), the European Monitoring and Evaluation Program (EMEP, https://ebas-data.nilu.no/Default.aspx), and the Monitoring Network in East Asia (EANET, www.eanet.asia).

## Estimates of atmospheric nitrogen deposition induced potential oceanic productivity and N₂O emissions

This study follows the approach of Duce et al.[5] to quantify the contribution of atmospheric nitrogen deposition to oceanic primary production and N₂O emissions. The Redfield ratio (C : N : P = 106:16:1), which describes the typical elemental composition of marine organic matter in the proportion of 106 moles carbon (C), 16 moles nitrogen (N), and 1 mole phosphorus (P), is applied to estimate the potential oceanic productivity associated with new nitrogen inputs, assuming other nutrients (P and Fe) are adequate[5,41-44]. For N₂O emissions, a linear scaling factor is adopted based on the estimate of mean global oceanic N₂O flux (5.0 Tg N a⁻¹) resulting from the total new nitrogen input to the surface ocean (167 Tg N a⁻¹ from N₂ fixation and atmospheric deposition)[5].

The impact of nitrogen deposition on new production (NP) is evaluated, which refers to productivity supported by new nutrients entering the euphotic zone. NP can be estimated by net primary productivity (NPP) using Eppley and Peterson's empirical formula[45]:

$$NP = \begin{cases} 0.0025 \times NPP^2, & NPP \le 200 \text{ mg C m}^{-2} \text{ d}^{-1} \\ 0.5 \times NPP, & NPP > 200 \text{ mg C m}^{-2} \text{ d}^{-1} \end{cases} \quad (1)$$

Here, the dataset of marine NPP estimated by the Vertically Generalized Production Model is obtained, a widely-used chlorophyll-based model (VGPM, http://orca.science.oregonstate.edu/1080.by.2160.monthly.hdf.vgpm.v.chl.v.sst.php). The ratio of nitrogen deposition-induced production and the new production provides a more relevant estimate of the extent to which atmospheric nitrogen deposition potentially supports new oceanic production.

# Results

## Changes in nitrogen emissions and deposition between 2015 and 2050

Global reactive nitrogen (Nr; NH₃ and NOₓ) emissions in 2015 are estimated to be 133.1 Tg N a⁻¹ and marine emissions contribute 21.1 Tg N a⁻¹ (16%) (Fig. 1). Marine N emissions include 10.4 Tg N a⁻¹ as NH₃ mostly from natural sources (e.g., phytoplankton activity and microbial processes) and 10.7 Tg N a⁻¹ as NOₓ from anthropogenic sources such as shipping activities. It is demonstrated that the model simulated NH₄⁺ and NO₃⁻ wet deposition fluxes are in reasonable agreement with ground-based observations (Supplementary Fig. S2; Fig. 2), with correlation coefficients of 0.75 for NH₄⁺ deposition and 0.73 for NO₃⁻ deposition and normalized mean biases of 0.3% for NH₄⁺ deposition and 15.6% for NO₃⁻ deposition. Model biases in Asia and
<figure><img src="image_4.png" /><figcaption>(a) Global NH₃ emission in 2015</figcaption></figure>

<figure><img src="image_5.png" /><figcaption>(b) Global NOₓ emission in 2015</figcaption></figure>

<figure><img src="image_6.png" /><figcaption>(c) Oceanic NH₃ emission in 2015</figcaption></figure>

<figure><img src="image_7.png" /><figcaption>(d) Oceanic NOₓ emission in 2015</figcaption></figure>

<figure><img src="image_8.png" /><figcaption>**Fig. 2** Comparisons of observed and simulated wet nitrogen deposition fluxes. The first row shows NO₃⁻ wet deposition, and the second row shows NH₄⁺ wet deposition in units of kg N ha⁻¹ a⁻¹. Model results are sampled along the observational stations from the NADP, EMEP, EANET, and combined networks.</figcaption></figure>

Europe are slightly larger, with NH₄⁺ wet deposition fluxes underestimated by 14.6%–19.2%. Such underestimation may result from inaccuracies in bottom-up NH₃ estimations and NH₃-NH₄⁺ partitioning affected by aerosol precursor emissions and chemistry.

The global oceanic nitrogen deposition in 2015 was estimated at 51.0 Tg N a⁻¹, accounting for 39% of the global total nitrogen

deposition (131 Tg N a⁻¹) (Fig. 3a). Global oceanic nitrogen deposition is substantially greater than oceanic emissions, reflecting the dominant contributions from terrestrial nitrogen sources. Of nitrogen deposited over the ocean, reduced nitrogen deposition accounts for 48.7% (24.9 Tg N a⁻¹), and wet deposition contributes 47.5% (28.9 Tg N a⁻¹). Intense oceanic nitrogen deposition fluxes
<figure><img src="image_9.png" /><figcaption>**Fig. 3** (a) Model simulated spatial distribution of oceanic nitrogen deposition in 2015 and projected changes under future 2050 emission scenarios, including (b) SSP126, (c) SSP370, and (d) SSP434. The inset values are the total global oceanic nitrogen deposition or total changes (percentage changes in parentheses) relative to the 2015 condition.</figcaption></figure>

occur along the coasts of East Asia, India, the Eastern United States, Western Europe, Southeastern Brazil, and Western Africa. These high nitrogen deposition rates in coastal regions are due to shipping emissions and transport of upwind terrestrial emissions, while those in equatorial and subtropical oceans are also largely influenced by natural oceanic $NH_3$ emissions.

Across three future emission scenarios for the year 2050, global oceanic nitrogen deposition exhibits significant variations ranging from 39 to 54 Tg N a⁻¹ (–24% to +6%, Fig. 3b–d). In the low-emission SSP126 scenario, total oceanic nitrogen deposition decreases by 12 Tg N a⁻¹ (24%) compared to the 2015 baseline simulation, primarily driven by stringent $NO_x$ emission reductions (–38.6%, –24 Tg N a⁻¹) while global $NH_3$ emissions remain nearly unchanged (–0.2%, –0.1 Tg N a⁻¹, Supplementary Fig. S3). In contrast, in the high-emission SSP370 scenario, total oceanic nitrogen deposition increases slightly (5.6%, 2.9 Tg N a⁻¹) associated with substantial growth in $NH_3$ emissions (16.9%, 11.6 Tg N a⁻¹) and increases in net global $NO_x$ emissions (6.4%, 4.0 Tg N a⁻¹). For the moderate-emission SSP434 scenario, substantial increases in global $NH_3$ emissions (28%, 19.6 Tg N a⁻¹) are offset by $NO_x$ emission reductions (–27.6%, –17.2 Tg N a⁻¹), while global oceanic nitrogen deposition declines by 6.5% (–3.3 Tg N a⁻¹). These differences partly reflect a nonlinear response of global oceanic nitrogen deposition to global nitrogen emissions, likely driven by interactions between $NH_3$ and $NO_x$ chemistry, and will be discussed later.

Deposition characteristics in different ocean regions

Figure 4 shows regional mean nitrogen deposition components (wet and dry; reduced $NH_x$ and oxidized nitrogen, $NO_y$) across eight oceanic

regions for 2015 and three 2050 future emission scenarios. Coastal areas exhibit significantly higher nitrogen deposition rates (2.4–19.5 kg N ha⁻¹ a⁻¹) compared to open oceans (0.9–1.8 kg N ha⁻¹ a⁻¹). Among coastal regions, deposition rates along China and Indian coasts (9.5–19.5 kg N ha⁻¹ a⁻¹) are much higher than the coasts of Europe and the United States (2.4–5.6 kg N ha⁻¹ a⁻¹). $NO_y$ depositions in the year 2015 account for 63% of the nitrogen deposition to China's coasts, 40% to the Indian coasts, 46% to the European coasts, and 63% to the US coasts, respectively. Their contributions typically increase over the adjacent open oceans, i.e., $NO_y$ deposition contributions of 40% to 45%, 46% to 65%, and 63% to 64%, respectively, reflecting longer lifetimes and thus transport distances for $NO_y$ than $NH_x$. Deposition pathways also differ considerably between coastal regions and open oceans. Wet deposition dominates in open oceans, while dry deposition is the main pathway in coastal areas. For example, 58%–62% of nitrogen is deposited through wet deposition in the North Pacific Ocean, compared to 46%–53% along the China coast.

Under all three future emission scenarios, the share of $NH_x$ deposition in total deposition increases across all ocean regions. The CMIP6 emission scenarios primarily represent socioeconomic development (e.g., increasing food demand and agricultural activities) and climate mitigation policies, while nitrogen interventions (e.g., substantially improving the nitrogen use efficiency of agricultural systems through technological advancements) are not explicitly addressed[46–48]. The CMIP6 emission projections thus reflect, under the low-emission scenario, co-benefits of clean energy transitions for $NO_x$ reductions; $NH_3$ emissions, however, are projected to stabilize or increase, driven by increasing food demand and somewhat simplified, moderate advancements in agricultural management[49]. Therefore, the increase in $NH_x$ deposition share is most pronounced under SSP126 (from 37% to 64% along China's coast and from 54%
<figure><img src="image_10.png" /><figcaption>**Fig. 4** Nitrogen deposition characteristics in representative ocean regions for 2015 and three 2050 scenarios. The underlying map shows geographic locations of ocean regions (also shown in Supplementary Fig. S1) investigated, including coastal areas (1st row from left to right: US coast, European coast, Indian coast, and China coast) and open oceans (2nd row from left to right: Western Atlantic Ocean, East Atlantic Ocean, North Indian Ocean, and North Pacific Ocean). In each panel, bars represent nitrogen deposition components (dry NHₓ, wet NHₓ, dry NOᵧ, and wet NOᵧ deposition) for 2015 and three future emission scenarios (SSP126, SSP370, and SSP434 for 2050). Pie charts show shares of dry vs wet deposition (1st row) and NHₓ vs NOᵧ deposition (2nd row). All deposition values are expressed in kg N ha⁻¹ a⁻¹.</figcaption></figure>

to 80% along the European coast), where climate mitigation policies and NOₓ reductions are the most ambitious. In contrast, NH₃ deposition share increases only moderately under SSP370 (from 47% to 49% in the North Pacific), where NOₓ emissions remain high in developing regions.

Furthermore, the deposition-to-emission (DTE) ratios are calculated as the regional-integrated annual total nitrogen deposition divided by regional emissions for both NH₃ and NOₓ across different ocean regions (Supplementary Fig. S4). DTE ratios for NH₃ and NOₓ are generally greater than 1 in ocean regions, as expected. The DTE ratio for NH₃ is consistently higher than that for NOₓ in coastal areas, where NH₃ deposition is more efficient due to shorter transport distances. The DTE ratios for NH₃ show minor variations across open and coastal areas and future scenarios (values of 3.02 ± 0.69). In contrast, the DTE ratios for NOₓ can exhibit distinct changes, e.g., increases from the China coast (1.65) to the North Pacific Ocean (3.90) and from the Indian coast (2.49) to the Indian Ocean (4.84), reflecting long-range transport of NOᵧ. The most notable future change occurs under SSP126, with significant increases in the North Pacific Ocean (from 3.90–9.92) and the North Indian Ocean (from 4.84–9.45), largely due to substantial NOₓ emission reductions from shipping sources.

## Responses of nitrogen deposition to nitrogen emission reductions

Figure 5 illustrates the impacts of individual NH₃ or NOₓ emission reductions and joint reactive nitrogen (Nr; NH₃ + NOₓ) emission reductions on oceanic nitrogen deposition in the European coast and the East Atlantic Ocean based on a series of sensitivity simulations with 25%, 50%, and 100% anthropogenic emission reductions under the SSP126 scenario. Results for other oceanic regions are shown in

Supplementary Figs S5–S7. The responses of nitrogen deposition to different emission reduction levels are close to linear for most deposition components, but the magnitudes and directions of response differ significantly across components. In coastal regions, reducing NOₓ emissions tends to increase dry NHₓ deposition, while reducing NH₃ emissions increases dry NOᵧ deposition.

Coastal regions are more sensitive to reductions in anthropogenic NH₃ and NOₓ emissions than open oceans. For the European coast, a hypothetical 100% reduction in anthropogenic NOₓ emissions results in a 94.3% decrease in total NOᵧ deposition, and a hypothetical 100% reduction in anthropogenic NH₃ emissions leads to a 90.5% reduction in total NHₓ deposition. In contrast, the East Atlantic Ocean exhibits weaker responses (than seen along the European coast), e.g., a 60% decrease in NHₓ deposition from 100% anthropogenic NH₃ reductions, reflecting contributions from natural oceanic NH₃ emissions.

Changes in emissions of an individual nitrogen species (NH₃ or NOₓ) can affect the spatial patterns of the other nitrogen species' deposition. This is most distinct through the dry deposition process. Reducing terrestrial NH₃ emissions tends to shift total nitrate from the aerosol phase to the gas phase as nitric acid, spreading it from source regions to coastal areas (Supplementary Fig. S8). As the dry deposition velocity of nitric acid gas is much larger than its aerosol component, this shift would enhance NOᵧ dry deposition over the coasts (Fig. 5). It would also decrease NOᵧ wet deposition over the coasts and depositions over the open oceans, as less NOᵧ can be transported in the free troposphere and to further distances. Such NOᵧ dry deposition increases associated with terrestrial NH₃ emission reductions are observed over the European and Chinese coasts, but not over the Indian and eastern US coasts, likely because all the enhanced nitric acid is deposited over terrestrial lands.
<figure><img src="image_11.png" /><figcaption>**Fig. 5** Responses of oceanic nitrogen deposition to varying levels of anthropogenic NH₃, NOₓ, and Nr emission reductions over the European coast (1st row) and Eastern Atlantic Ocean (2nd row) under the SSP126 2050 scenario. Relative changes in each nitrogen deposition component, including dry NHₓ (blue solid), wet NHₓ (blue dashed), dry NOᵧ (red solid), and wet NOᵧ (red dashed) driven by individual NH₃ emission reductions (left column), NOₓ emission reductions (middle column), and joint Nr (NOₓ and NH₃) emission reductions (right column). The inset numbers show the corresponding percentage changes for the specific reduction levels.</figcaption></figure>

Similarly, reducing terrestrial NOₓ emissions would notably increase NHₓ dry deposition along coasts, as reduced nitrate concentrations inhibit the conversion of gaseous ammonia to aerosol ammonium (Supplementary Fig. S8), and the former phase can be more readily dry deposited than the latter. This effect is increasingly evident with greater reductions in NOₓ emissions. For example, Fig. 5 shows that NHₓ dry deposition to the Western European coast may increase by 4.0% when anthropogenic NOₓ emissions are reduced by 25%, but increase by 20.8% with 100% anthropogenic NOₓ emission reductions. A high level of NOₓ emission reduction may significantly reduce tropospheric ozone and atmospheric oxidation capacity, thereby decreasing sulfate aerosol formation and further shifting NHₓ partitioning toward its gaseous form. It was found that Joint NH₃ and NOₓ emission controls appear to suppress the interaction of NH₃ and NOₓ chemistry, and lead to substantial decreases in both wet and dry deposition of NHₓ and NOᵧ.

## Impacts on oceanic productivity and N₂O emissions

The baseline of 51.0 Tg N a⁻<fnref n="1" /> atmospheric nitrogen deposition to the oceans would account for a global productivity of 290 Tg C a⁻<fnref n="1" /> based on the Redfield ratio. It is estimated that the global marine net primary productivity (NPP) was 45.6 Pg C a⁻<fnref n="1" /> and the global new production was 22.2 Pg C a⁻<fnref n="1" /> in 2015 based on the method described in the Methods section (Supplementary Fig. S9a). Atmospheric nitrogen deposition thus potentially supports approximately 1.3% of global new production, but with significant regional variations (Supplementary Fig. S9b). In nitrogen-limited oceans, such as the Northwest Atlantic Ocean, nitrogen deposition contributes around 8%.

Projected changes in oceanic nitrogen deposition under future emission scenarios may influence both ocean productivity and N₂O emissions (Table 1). In the SSP126 scenario, a decline in nitrogen

deposition would decrease the global ocean productivity from 290 Tg C to 222 Tg C, a 23% (68 Tg C a⁻<fnref n="1" />) decrease. According to estimates by the US Environmental Protection Agency (EPA) and the International Energy Agency (IEA), this reduction is roughly equivalent to annual CO₂ emissions of 54.25 million cars or 57.98 million people, or carbon stored in approximately 9.94 billion trees (~0.3% of the current global tree population)[⁵⁰]. Atmospheric nitrogen deposition contributing to oceanic productivity is projected to decrease by 19 Tg C a⁻<fnref n="1" /> under the SSP434 scenario and increase by 16 Tg C a⁻<fnref n="1" /> under the SSP370 scenario, relative to the 2015 baseline. Following the approach of Duce et al.[⁵], it is estimated that anthropogenic nitrogen deposition contributes approximately 1.5 (1.16–1.89) Tg N a⁻<fnref n="1" /> of N₂O-N under 2015 conditions, accounting for roughly one-third of the total oceanic N₂O emissions. The projected N₂O-N emissions from nitrogen deposition would decrease to ~1.2 (0.89–1.45) Tg N a⁻<fnref n="1" /> under SSP126, increase to ~1.6 (1.23–2.00) Tg N a⁻<fnref n="1" /> under SSP370, and reach ~1.4 (1.1–1.77) Tg N a⁻<fnref n="1" /> under SSP434 by 2050 (Table 1). Considering the global warming potential of N₂O (GWP = 298 over 100 years), changes in

<table><caption>**Table 1** Potential impacts of atmospheric nitrogen deposition on global ocean productivity and N₂O emissions</caption><thead><tr><th>Scenarios</th><th>Nitrogen deposition (Tg N a<sup>-1</sup>)</th><th>Potential oceanic productivity (Tg C a<sup>-1</sup>)</th><th>N<sub>2</sub>O-N emissions (Tg N a<sup>-1</sup>)</th></tr></thead><tbody><tr><td>Base (2015)</td><td>51.0</td><td>290</td><td>1.53 (1.16-1.89)<sup>1</sup></td></tr><tr><td>SSP1-RCP2.6 (2050)</td><td>39.0</td><td>222</td><td>1.17 (0.89-1.45)</td></tr><tr><td>SSP3-RCP7.0 (2050)</td><td>53.9</td><td>306</td><td>1.61 (1.23-2.00)</td></tr><tr><td>SSP4-RCP3.4 (2050)</td><td>47.7</td><td>271</td><td>1.43 (1.1-1.77)</td></tr></tbody></table>

<footnote n="1">¹The N₂O emission range reflects the uncertainty in present-day N₂O emission estimates given in Duce et al.[⁵].</footnote>
the oceanic N₂O emissions would offset ~60% of the climatic effects of changing oceanic productivity, as suggested in Duce et al.[⁵].

It should be noted that these estimates are subject to significant uncertainties. The Redfield Ratio provides a convenient method to estimate the contribution of nitrogen deposition to ocean productivity. Still, the assumption of a fixed ratio may introduce significant uncertainty by neglecting regional and ecosystem-specific variations[⁵¹]. For example, in regions where phytoplankton productivity is limited by iron or phosphorus, the actual contribution of nitrogen inputs may be lower than theoretical estimates[⁵²]. Furthermore, studies have reported a wide range of estimates of nitrogen deposition's impacts on ocean productivity, ranging from 180 Tg C a⁻¹ to 400 Tg C a⁻¹ globally[⁷,⁵³]. These discrepancies stem primarily from differences in nutrient limitation conditions and regional ecosystem responses, and from the fact that NH₄⁺ and NO₃⁻ can influence marine productivity through different mechanisms, which are not considered in this study. Similarly, the calculations of N₂O emission changes assume linear scaling and steady-state conditions, and thus do not capture regional variations or potential nonlinear microbial responses to changes in nitrogen supply.

## Conclusions and discussion

The results provide a quantitative and process-based assessment of how future anthropogenic emissions will reshape oceanic nitrogen deposition and its impacts on marine biogeochemistry. Between 2015 and 2050, global oceanic nitrogen deposition is projected to change by ~24% to +6% across three CMIP6 emission scenarios, with a substantially increasing share contributed by reduced nitrogen (NH₄). A key finding is the strong chemical interactions between reduced and oxidized nitrogen. Reducing emissions of one species (NH₃ or NOₓ) enhances the dry deposition of the other species to the oceans through a combination of gas-particle partitioning and changes in oxidant levels. Jointly controlling NH₃ and NOₓ emissions would be more effective than managing individual nitrogen species in reducing oceanic nitrogen deposition.

Projected changes in nitrogen deposition also affect marine productivity and climate-relevant gases. The current (2015) atmospheric nitrogen deposition is expected to support ~290 Tg C a⁻¹ of potential ocean productivity (about 1.3% of global new production), consistent with earlier estimates of the contribution of atmospheric nitrogen to marine production[²,⁵,⁷]. Under the low-emission SSP126 scenario, the decline in nitrogen deposition reduces the potential productivity by ~68 Tg C a⁻¹, whereas under the high-emission SSP370 scenario, it increases by ~16 Tg C a⁻¹. However, the associated changes in oceanic N₂O emissions offset a substantial fraction of the climatic effects of the productivity response, highlighting a trade-off between carbon uptake and N₂O forcing that is intrinsic to nitrogen-driven biogeochemical feedbacks.

The findings have several policy-relevant implications for nitrogen management. First, the diagnosed chemical interaction implies that traditional single-pollutant strategies targeting either NH₃ or NOₓ alone may lead to unintended increases in oceanic dry deposition of the uncontrolled species, especially in coastal regions downwind of major terrestrial sources. This suggests that coordinated, multi-pollutant control strategies that jointly reduce NH₃ and NOₓ are needed to robustly decrease total nitrogen deposition to the oceans, in line with recent calls for integrated nitrogen management frameworks[²²,²⁸⁻³²]. Second, decarbonization and air-quality policies embedded in SSP1-type pathways primarily reduce NOₓ

emissions, thereby shifting oceanic nitrogen deposition toward a greater NH₄⁺ contribution. Without explicit NH₃ controls, such pathways may unintentionally increase the relative importance of reduced nitrogen deposition to sensitive coastal ecosystems, thereby partly offsetting the benefits of NOₓ abatement for marine eutrophication and N₂O mitigation.

In addition to the impact estimates discussed above, several uncertainties must be considered. Fixing all model simulations to 2015 meteorological conditions does not account for potential changes in meteorological factors and natural emissions under the projected 2050 climate. This assumption may omit potentially important climate-driven feedbacks, such as changes in atmospheric circulation, precipitation, oxidant fields, and biogenic emissions, which could influence nitrogen deposition patterns[⁵⁴]. Previous studies suggested that changes in anthropogenic emissions primarily drove long-term trends in nitrogen deposition, whereas climate change mostly influenced the interannual variability of nitrogen deposition[⁵⁵]. Nonetheless, regional-scale or process-specific sensitivities to future climate conditions may still introduce additional uncertainties to the estimates and should be assessed in future work using coupled chemistry-climate simulations.

Furthermore, the CMIP6 emission scenarios used here do not explicitly include ambitious NH₃ controls or deep nitrogen management policies, even though such measures are increasingly discussed in global mitigation efforts[⁵⁶]. Current environmental policies still lack stringent controls on NH₃ emissions[⁵⁷]; however, various nitrogen intervention strategies, such as improving nitrogen-use efficiency and promoting low-emission livestock management practices, have the potential to reduce NH₃ emissions and agricultural N₂O and nitrate leaching[²³]. The inclusion of such policies in future emission pathways, as demonstrated by the INMS scenarios[³¹], could yield more realistic projections of nitrogen emissions and their effects on ecosystems and should be incorporated into future studies.

Despite these limitations, the study provides a comprehensive, process-oriented picture of how future changes in anthropogenic NH₃ and NOₓ emissions may reshape oceanic nitrogen deposition and its biogeochemical and climatic consequences. This study's results complement existing research on nitrogen deposition responses to changes in emissions and provide new insights into the broader impacts of nitrogen management, particularly on ocean ecosystems. These findings highlight the need for holistic, Earth-system-scale assessments of nitrogen management and for coordinated control strategies to mitigate future nitrogen impacts on marine ecosystems effectively.

## Supplementary information

It accompanies this paper at: https://doi.org/10.48130/nc-0025-0025.

## Author contributions

The authors confirm their contributions to the paper as follows: Jialin Deng: data collection, analysis and draft manuscript writing; Yixin Guo: data collection and draft manuscript revision; Ni Lu: valuable advice input; Xingpei Ye: valuable advice input; Yuanhong Zhao: valuable advice input; Jiayu Xu: valuable advice input; Lei Liu: data collection and valuable advice input; Lin Zhang: study framework design and draft manuscript revision. All authors reviewed the results and approved the final version of the manuscript.
Data availability

The datasets generated during and/or analyzed during the current
study are available from the corresponding author upon reasonable
request.

Acknowledgments

The work is also supported by the High-performance Computing
Platform of Peking University.

Funding

This work is supported by the National Key Research and Development Program of China (Grant No. 2023YFC3707404), and the National Natural Science Foundation of China (Grant Nos 42275106, 42371324).

Declarations

Competing interests

The authors declare that they have no conflict of interest.

Author details

¹Laboratory for Climate and Ocean-Atmosphere Studies, Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871, China; ²Earth, Ocean and Atmospheric Sciences Thrust, Hong Kong University of Science and Technology, Guangzhou 511453, China; ³College of Oceanic and Atmospheric Sciences, Ocean University of China, Qingdao 266100, China; ⁴Laboratoire des Sciences du Climat et de l'Environnement (LSCE), CEA-CNRS-UVSQ, Université Paris-Saclay, Gif-sur-Yvette 91191, France; ⁵State Key Laboratory of Lake and Watershed Science for Water Security, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 211135, China

References

[1] Dentener F, Drevet J, Lamarque JF, Bey I, Eickhout B, et al. 2006. Nitrogen and sulfur deposition on regional and global scales: a multimodel evaluation. *Global Biogeochemical Cycles* 20:2005GB002672

[2] Jickells TD, Buitenhuis E, Altieri K, Baker AR, Capone D, et al. 2017. A reevaluation of the magnitude and impacts of anthropogenic atmospheric nitrogen inputs on the ocean. *Global Biogeochemical Cycles* 31:289–305

[3] Ren H, Chen YC, Wang XT, Wong GTF, Cohen AL, et al. 2017. 21st-century rise in anthropogenic nitrogen deposition on a remote coral reef. *Science* 356:749–752

[4] Young RW, Carder KL, Betzer PR, Costello DK, Duce RA, et al. 1991. Atmospheric iron inputs and primary productivity: phytoplankton responses in the North Pacific. *Global Biogeochemical Cycles* 5:119–134

[5] Duce RA, LaRoche J, Altieri K, Arrigo KR, Baker AR, et al. 2008. Impacts of atmospheric anthropogenic nitrogen on the open ocean. *Science* 320:893–897

[6] Xiu P, Chai F. 2021. Impact of atmospheric deposition on carbon export to the deep ocean in the subtropical Northwest Pacific. *Geophysical Research Letters* 48:e2020GL089640

[7] Krishnamurthy A, Moore JK, Mahowald N, Luo C, Doney SC, et al. 2009. Impacts of increasing anthropogenic soluble iron and nitrogen deposition on ocean biogeochemistry. *Global Biogeochemical Cycles* 23:2008GB003440

[8] Okin GS, Baker AR, Tegen I, Mahowald NM, Dentener FJ, et al. 2011. Impacts of atmospheric nutrient deposition on marine productivity: Roles of nitrogen, phosphorus, and iron. *Global Biogeochemical Cycles* 25:2010GB003858

[9] Moore CM, Mills MM, Arrigo KR, Berman-Frank I, Bopp L, et al. 2013. Processes and patterns of oceanic nutrient limitation. *Nature Geoscience* 6:701–710

[10] Vitousek PM, Aber JD, Howarth RW, Likens GE, Matson PA, et al. 1997. Human alteration of the global nitrogen cycle: sources and consequences. *Ecological Applications* 7:737–750

[11] Galloway JN, Dentener FJ, Capone DG, Boyer EW, Howarth RW, et al. 2004. Nitrogen cycles: past, present, and future. *Biogeochemistry* 70:153–226

[12] Phoenix GK, Hicks WK, Cinderby S, Kuvlenstierna JCI, Stock WD, et al. 2006. Atmospheric nitrogen deposition in world biodiversity hotspots: the need for a greater global perspective in assessing N deposition impacts. *Global Change Biology* 12:470–476

[13] Galloway JN, Townsend AR, Erisman JW, Bekunda M, Cai Z, et al. 2008. Transformation of the nitrogen cycle: recent trends, questions, and potential solutions. *Science* 320:889–892

[14] Erisman JW, Galloway J, Seitzinger S, Bleeker A, Dise NB, et al. 2013. Consequences of human modification of the global nitrogen cycle. *Philosophical Transactions of the Royal Society of London Series B, Biological Sciences* 368:20130116

[15] Hutchins DA, Capone DG. 2022. The marine nitrogen cycle: new developments and global change. *Nature Reviews Microbiology* 20:401–414

[16] Gong C, Tian H, Liao H, Pan N, Pan S, et al. 2024. Global net climate effects of anthropogenic reactive nitrogen. *Nature* 632:557–563

[17] Zhu J, Jia Y, Yu G, Wang Q, He N, et al. 2025. Changing patterns of global nitrogen deposition driven by socioeconomic development. *Nature Communications* 16:46

[18] Gruber N, Galloway JN. 2008. An Earth-system perspective of the global nitrogen cycle. *Nature* 451:293–296

[19] Fowler D, Coyle M, Skiba U, Sutton MA, Cape JN, et al. 2013. The global nitrogen cycle in the twenty-first century. *Philosophical Transactions of the Royal Society B: Biological Sciences* 368:20130164

[20] Liu L, Xu W, Wen Z, Liu P, Xu H, et al. 2023. Modeling global oceanic nitrogen deposition from food systems and its mitigation potential by reducing overuse of fertilizers. *Proceedings of the National Academy of Sciences of the United States of America* 120:e2221459120

[21] Liu S, Zhao Y, Lin Y, Wang J, Li Q, et al. 2025. Atmospheric reactive nitrogen deposition to the global ocean during the 2010s: interannual variation and source attribution. *Journal of Geophysical Research: Atmospheres* 130:e2024JD042789

[22] Shang F, Liu M, Song Y, Lu X, Zhang Q, et al. 2024. Substantial nitrogen abatement accompanying decarbonization suppresses terrestrial carbon sinks in China. *Nature Communications* 15:7738

[23] Zhu H, Chen Y, Zhao Y, Zhang L, Zhang X, et al. 2022. The response of nitrogen deposition in china to recent and future changes in anthropogenic emissions. *Journal of Geophysical Research: Atmospheres* 127:e2022JD037437

[24] Erisman JW, Dammers E, Van Damme M, Soudzilovskaia N, Schaap M. 2015. Trends in EU nitrogen deposition and impacts on ecosystems. EM: Air and Waste Management Association's Magazine for Environmental Managers 65:31–35

[25] Winiwarter W, Grizzetti B, Sutton MA. 2015. Nitrogen pollution in the EU: Best management strategies, regulations, and science needs. EM: Air and Waste Management Association's Magazine for Environmental Managers 65:18–23

[26] Schmalensee R, Stavins RN. 2019. Policy Evolution under the Clean Air Act. *Journal of Economic Perspectives* 33:27–50

[27] Zhang Q, Zheng Y, Tong D, Shao M, Wang S, et al. 2019. Drivers of improved PM₂.₅ air quality in China from 2013 to 2017. *Proceedings of the National Academy of Sciences of the United States of America* 116:24463–24469

[28] Pozzer A, Tsimpi ID, Karydis VA, de Meij A, Lelieveld J. 2017. Impact of agricultural emission reductions on fine-particulate matter and public health. *Atmospheric Chemistry and Physics* 17:12813–12826

[29] Pan SY, He KH, Lin KT, Fan C, Chang CT. 2022. Addressing nitrogenous gases from croplands toward low-emission agriculture. *npj Climate and Atmospheric Science* 5:43
[30] Guo Y, Zhang L, Winiwarter W, Grinsven HJM van, Wang X, et al. 2024. Ambitious nitrogen abatement is required to mitigate future global PM<sub>2.5</sub> air pollution toward the World Health Organization targets. *One Earth* 7:1600–1613

[31] Guo Y, Zhao H, Winiwarter W, Chang J, Wang X, et al. 2024. Aspirational nitrogen interventions accelerate air pollution abatement and ecosystem protection. *Science Advances* 10:eado0112

[32] Duan J, Liu H, Zhang X, Ren C, Wang C, et al. 2024. Agricultural management practices in China enhance nitrogen sustainability and benefit human health. *Nature Food* 5:378–389

[33] Park RJ, Jacob DJ, Field BD, Yantosca RM, Chin M. 2004. Natural and transboundary pollution influences on sulfate-nitrate-ammonium aerosols in the United States: implications for policy. *Journal of Geophysical Research: Atmospheres* 109:2003JD004473

[34] Liu H, Jacob DJ, Bey I, Yantosca RM. 2001. Constraints from 210Pb and 7Be on wet deposition and transport in a global three - dimensional chemical tracer model driven by assimilated meteorological fields. *Journal of Geophysical Research: Atmospheres* 106:12109–12128

[35] Wesely ML. 1989. Parameterization of surface resistances to gaseous dry deposition in regional-scale numerical models. *Atmospheric Environment* 23:1293–1304

[36] van Vuuren DP, Stehfest E, Gernaat DEHJ, Doelman JC, van den Berg M, et al. 2017. Energy, land-use and greenhouse gas emissions trajectories under a green growth paradigm. *Global Environmental Change* 42:237–250

[37] Fujimori S, Hasegawa T, Masui T, Takahashi K, Herran DS, et al. 2017. SSP3: AIM implementation of Shared Socioeconomic Pathways. *Global Environmental Change* 42:268–283

[38] Calvin K, Bond-Lamberty B, Clarke L, Edmonds J, Eom J, et al. 2017. The SSP4: a world of deepening inequality. *Global Environmental Change* 42:284–296

[39] Hudman RC, Moore NE, Mebust AK, Martin RV, Russell AR, et al. 2012. Steps towards a mechanistic model of global soil nitric oxide emissions: implementation and space based-constraints. *Atmospheric Chemistry and Physics* 12:7779–7795

[40] Randerson JT, Van Der Werf GR, Giglio L, Collatz GJ, Kasibhatla PS. 2015. *Global Fire Emissions Database*, Version 4.1 (GFEDv4). Oak Ridge National Laboratory DAAC (ORNL DAAC) doi: 10.3334/ORNLDAAC/1293

[41] Redfield AC. 1958. The biological control of chemical factors in the environment. *American Scientist* 46(3):205–221

[42] Zhang Y, Yu Q, Ma W, Chen L. 2010. Atmospheric deposition of inorganic nitrogen to the Eastern China seas and its implications to marine biogeochemistry. *Journal of Geophysical Research: Atmospheres* 115:2009JD012814

[43] Singh A, Gandhi N, Ramesh R. 2012. Contribution of atmospheric nitrogen deposition to new production in the nitrogen limited photic zone of the northern Indian Ocean. *Journal of Geophysical Research: Oceans* 117:2011JC007737

[44] Qi JH, Shi JH, Gao HW, Sun Z. 2013. Atmospheric dry and wet deposition of nitrogen species and its implication for primary productivity in

coastal region of the Yellow Sea, China. *Atmospheric Environment* 81:600–608

[45] Eppley RW, Peterson BJ. 1979. Particulate organic matter flux and planktonic new production in the deep ocean. *Nature* 282:677–680

[46] Bodirsky BL, Popp A, Lotze-Campen H, Dietrich JP, Rolinski S, et al. 2014. Reactive nitrogen requirements to feed the world in 2050 and potential to mitigate nitrogen pollution. *Nature Communications* 5:3858

[47] O'Neill BC, Kriegler E, Ebi KL, Kemp-Benedict E, Riahi K, et al. 2017. The roads ahead: narratives for shared socioeconomic pathways describing world futures in the 21st century. *Global Environmental Change* 42:169–180

[48] Xu P, Li G, Zheng Y, Fung JCH, Chen A, et al. 2024. Fertilizer management for global ammonia emission reduction. *Nature* 626:792–798

[49] Gidden MJ, Riahi K, Smith SJ, Fujimori S, Luderer G, et al. 2019. Global emissions pathways under different socioeconomic scenarios for use in CMIP6: a dataset of harmonized emissions trajectories through the end of the century. *Geoscientific Model Development* 12:1443–1475

[50] Crowther TW, Glick HB, Covey KR, Bettigole C, Maynard DS, et al. 2015. Mapping tree density at a global scale. *Nature* 525:201–205

[51] Somes CJ, Landolfi A, Koeve W, Oschlies A. 2016. Limited impact of atmospheric nitrogen deposition on marine productivity due to biogeochemical feedbacks in a global ocean model. *Geophysical Research Letters* 43:4500–4509

[52] Galbraith ED, Martiny AC. 2015. A simple nutrient-dependence mechanism for predicting the stoichiometry of marine ecosystems. *Proceedings of the National Academy of Sciences of the United States of America* 112:8199–8204

[53] Kanakidou M, Myriokefalinakis S, Daskalakis N, Fanourgakis G, Nenes A, et al. 2016. Past, present, and future atmospheric nitrogen deposition. *Journal of the Atmospheric Sciences* 73:2039–2047

[54] Wang X, Zhang L, Deng J, Shao M. 2025. Climate-driven perturbations on land emissions and deposition of atmospheric nitrogen. *Science Bulletin* 70:3943–3946

[55] Ma M, Zheng B, Xu W, Cao J, Zhou K, et al. 2023. Trend and interannual variations of reactive nitrogen deposition in China during 2008–2017 and the roles of anthropogenic emissions and meteorological conditions. *Journal of Geophysical Research: Atmospheres* 128:e2022JD037489

[56] Kanter DR, Winiwarter W, Bodirsky BL, Bouwman L, Boyer E, et al. 2020. A framework for nitrogen futures in the shared socioeconomic pathways. *Global Environmental Change* 61:102029

[57] Bai Z, Winiwarter W, Klimont Z, Velthof G, Misselbrook T, et al. 2019. Further improvement of air quality in China needs clear ammonia mitigation target. *Environmental Science & Technology* 53:10542–10544

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