Using stable isotopes to distinguish atmospheric nitrate production and its contribution to the surface ocean across hemispheres

2021 ◽  
Vol 564 ◽  
pp. 116914
Author(s):  
Guitao Shi ◽  
Hongmei Ma ◽  
Zhuoyi Zhu ◽  
Zhengyi Hu ◽  
Zhenlou Chen ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Surface Ocean ◽  
Nitrate Production ◽  
Atmospheric Nitrate

scholarly journals The importance of alkyl nitrates and sea ice emissions to atmospheric NO<sub>x</sub> sources and cycling in the summertime Southern Ocean marine boundary layer

2021 ◽  
Author(s):  
Jessica Mary Burger ◽  
Julie Granger ◽  
Emily Joyce ◽  
Meredith Galanter Hastings ◽  
Kurt Angus McDonald Spence ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Southern Ocean ◽  
Sea Ice ◽  
Marine Boundary Layer ◽  
Weddell Sea ◽  
Alkyl Nitrates ◽  
Air Mass ◽  
Surface Ocean ◽  
Alkyl Nitrate ◽  
Atmospheric Nitrate

Abstract. Atmospheric nitrate originates from the oxidation of nitrogen oxides (NOx = NO + NO2) and impacts both tropospheric chemistry and climate. NOx sources, cycling, and NOx to nitrate formation pathways are poorly constrained in remote marine regions, especially the Southern Ocean where pristine conditions serve as a useful proxy for the preindustrial atmosphere. Here, we measured the isotopic composition (δ15N and δ18O) of atmospheric nitrate in coarse-mode (> 1 μm) aerosols collected in the summertime marine boundary layer of the Atlantic Southern Ocean from 34.5° S to 70° S, and across the northern edge of the Weddell Sea. The δ15N-NO3− decreased with latitude from −2.7 ‰ to −43.1 ‰. The decline in δ15N with latitude is attributed to changes in the dominant NOx sources: lightning at the low latitudes, oceanic alkyl nitrates at the mid latitudes, and photolysis of nitrate in snow at the high latitudes. There is no evidence of any influence from anthropogenic NOx sources or equilibrium isotopic fractionation. Using air mass back trajectories and an isotope mixing model, we calculate that oceanic alkyl nitrate emissions have a δ15N signature of −22.0 ‰ ± 7.5 ‰. Given that measurements of alkyl nitrate contributions to remote nitrogen budgets are scarce, this may be a useful tracer for detecting their contribution in other oceanic regions. The δ18O-NO3− was always less than 70 ‰, indicating that daytime processes involving OH are the dominant NOx oxidation pathway during summer. Unusually low δ18O-NO3− values (less than 31 ‰) were observed at the western edge of the Weddell Sea. The air mass history of these samples indicates extensive interaction with sea ice covered ocean, which is known to enhance peroxy radical production. The observed low δ18O-NO3− is therefore attributed to increased exchange of NO with peroxy radicals, which have a low δ18O, relative to ozone, which has a high δ18O. This study reveals that the mid- and high-latitude surface ocean may serve as a more important NOx source than previously thought, and that the ice-covered surface ocean impacts the reactive nitrogen budget as well as the oxidative capacity of the marine boundary layer.

scholarly journals δ<sup>18</sup>O water isotope in the <i>i</i>LOVECLIM model (version 1.0) – Part 3: A paleoperspective based on present-day data-model comparison for oxygen stable isotopes in carbonates

2013 ◽  
Vol 6 (1) ◽  
pp. 1527-1558
Author(s):  
T. Caley ◽  
D. M. Roche
Keyword(s):  
Stable Isotopes ◽  
Data Model ◽  
Model Comparison ◽  
Oceanic Circulation ◽  
Three Dimensional Model ◽  
Secondary Importance ◽  
Surface Ocean ◽  
The Past ◽  
Oxygen Stable Isotopes ◽  
Comparison Exercise

Abstract. Oxygen stable isotopes (18O) are among the most usual tools in paleoclimatology/paleoceanography. Simulation of oxygen stable isotopes allows testing how the past variability of these isotopes in water can be interpreted. By modelling the proxy directly in the model, the results can also be directly compared with the data. Water isotopes have been implemented in the global three-dimensional model of intermediate complexity iLOVECLIM allowing fully coupled atmosphere-ocean simulations. In this study, we present the validation of the model results for present day climate against global database for oxygen stable isotopes in carbonates. The limitation of the model together with the processes operating in the natural environment reveal the complexity of use the continental calcite 18O signal of speleothems for a data-model comparison exercise. On the contrary, the reconstructed surface ocean calcite δ18O signal in iLOVECLIM does show a very good agreement with late Holocene database (foraminifers) at the global and regional scales. Our results indicate that temperature and the isotopic composition of the seawater are the main control on the fossil δ18O signal recorded in foraminifer shells and that depth habitat and seasonality play a role but have secondary importance. We argue that a data-model comparison for surface ocean calcite δ18O in past climate, such as the last glacial maximum (&amp;approx;21 000 yr), could constitute an interesting tool for mapping the potential shifts of the frontal systems and circulation changes throughout time. Similarly, the potential changes in intermediate oceanic circulation systems in the past could be documented by a data (benthic foraminifers)-model comparison exercise whereas future investigations are necessary in order to quantitatively compare the results with data for the deep ocean.

scholarly journals Atmospheric Δ<sup>17</sup>O(NO<sub>3</sub><sup>−</sup>) reveals nocturnal chemistry dominates nitrate production in Beijing haze

2018 ◽  
Vol 18 (19) ◽  
pp. 14465-14476 ◽  
Author(s):  
Pengzhen He ◽  
Zhouqing Xie ◽  
Xiyuan Chi ◽  
Xiawei Yu ◽  
Shidong Fan ◽  
...  
Keyword(s):  
Fine Particle ◽  
Driving Force ◽  
Sampling Period ◽  
Field Observations ◽  
Relative Importance ◽  
Nitrate Production ◽  
Atmospheric Nitrate ◽  
Particle Pollution ◽  
Mass Increase ◽  
Rapid Mass

Abstract. The rapid mass increase of atmospheric nitrate is a critical driving force for the occurrence of fine-particle pollution (referred to as haze hereafter) in Beijing. However, the exact mechanisms for this rapid increase of nitrate mass have not been well constrained from field observations. Here we present the first observations of the oxygen-17 excess of atmospheric nitrate (Δ17O(NO3-)) collected in Beijing haze to reveal the relative importance of different nitrate formation pathways, and we also present the simultaneously observed δ15N(NO3-). During our sampling period, 12 h averaged mass concentrations of PM2.5 varied from 16 to 323 µg m−3 with a mean of (141±88(1SD)) µg m−3, with nitrate ranging from 0.3 to 106.7 µg m−3. The observed Δ17O(NO3-) ranged from 27.5 ‰ to 33.9 ‰ with a mean of (30.6±1.8) ‰, while δ15N(NO3-) ranged from −2.5 ‰ to 19.2 ‰ with a mean of (7.4±6.8) ‰. Δ17O(NO3-)-constrained calculations suggest nocturnal pathways (N2O5+H2O/Cl- and NO3+HC) dominated nitrate production during polluted days (PM2.5≥75 µg m−3), with a mean possible fraction of 56–97 %. Our results illustrate the potentiality of Δ17O in tracing nitrate formation pathways; future modeling work with the constraint of isotope data reported here may further improve our understanding of the nitrogen cycle during haze.

scholarly journals δ<sup>18</sup>O water isotope in the <i>i</i>LOVECLIM model (version 1.0) – Part 3: A palaeo-perspective based on present-day data–model comparison for oxygen stable isotopes in carbonates

2013 ◽  
Vol 6 (5) ◽  
pp. 1505-1516 ◽  
Author(s):  
T. Caley ◽  
D. M. Roche
Keyword(s):  
Stable Isotopes ◽  
Data Model ◽  
Model Comparison ◽  
Individual Species ◽  
Oceanic Circulation ◽  
Three Dimensional Model ◽  
Surface Ocean ◽  
The Past ◽  
Oxygen Stable Isotopes ◽  
Comparison Exercise

Abstract. Oxygen stable isotopes (δ18O) are among the most useful tools in palaeoclimatology/palaeoceanography. Simulation of oxygen stable isotopes allows testing how the past variability of these isotopes in water can be interpreted. By modelling the proxy directly in the model, the results can also be directly compared with the data. Water isotopes have been implemented in the global three-dimensional model of intermediate complexity iLOVECLIM, allowing fully coupled atmosphere–ocean simulations. In this study, we present the validation of the model results for present-day climate against the global database for oxygen stable isotopes in carbonates. The limitation of the model together with the processes operating in the natural environment reveal the complexity of use the continental calcite-δ18O signal of speleothems for a global quantitative data–model comparison exercise. On the contrary, the reconstructed surface ocean calcite-δ18O signal in iLOVECLIM does show a very good agreement with the late Holocene database (foraminifers) at the global and regional scales. Our results indicate that temperature and the isotopic composition of the seawater are the main control on the fossil-δ18O signal recorded in foraminifer shells when all species are grouped together. Depth habitat, seasonality and other ecological effects play a more significant role when individual species are considered. We argue that a data–model comparison for surface ocean calcite δ18O in past climates, such as the Last Glacial Maximum (≈ 21 000 yr), could constitute an interesting tool for mapping the potential shifts of the frontal systems and circulation changes throughout time. Similarly, the potential changes in intermediate oceanic circulation systems in the past could be documented by a data (benthic foraminifers)-model comparison exercise whereas future investigations are necessary in order to quantitatively compare the results with data for the deep ocean.

scholarly journals Atmospheric Δ<sup>17</sup>O(NO<sub>3</sub><sup>−</sup>) reveals nocturnal chemistry dominates nitrate production in Beijing haze

2018 ◽  
Author(s):  
Pengzhen He ◽  
Zhouqing Xie ◽  
Xiyuan Chi ◽  
Xiawei Yu ◽  
Shidong Fan ◽  
...  
Keyword(s):  
Fine Particle ◽  
Isotopic Exchange ◽  
Sampling Period ◽  
Relative Importance ◽  
Nitrate Production ◽  
Atmospheric Nitrate ◽  
Particle Pollution ◽  
The Mean ◽  
Mass Increase ◽  
Rapid Mass

Abstract. The rapid mass increase of atmospheric nitrate is a critical driving force for the occurrence of fine-particle pollution (referred to as haze hereafter) in Beijing. However, the exact mechanisms for this rapid increase of nitrate mass has been not well constrained from field observations. Here we present the first observations of the oxygen-17 excess of atmospheric nitrate (Δ17O(NO3−)) collected in Beijing haze to reveal the relative importance of different nitrate formation pathways, and we also present the simultaneously observed δ15N(NO3−). During our sampling period, 12 h-averaged mass concentrations of PM2.5 varied from 16 to 323 μg m−3 with a mean of (141 ± 88 (1σ)) μg m−3, with nitrate ranging from 0.3 to 106.7 μg m−3. The observed Δ17O(NO3−) ranged from 27.5 ‰ to 33.9 ‰ with a mean of (30.6 ± 1.8) ‰ while δ15N(NO3−) ranged from −2.5 ‰ to 19.2 ‰ with a mean of (7.4 ± 6.8) ‰. Δ17O(NO3−)-constrained calculations suggest nocturnal pathways (N2O5 + H2O/Cl− and NO3 + HC) dominated nitrate production during polluted days (PM2.5 ≥ 75 μg m−3) with the mean possible fraction of 56 − 97 %. For δ15N(NO3−), we found that a combined effect of variability in NOX sources and isotopic exchange between NO and NO2 is likely to be most responsible for its variations. Our results illustrate the potentiality of isotope in tracing NOX sources and nitrate formation pathways, future modelling work with the constraint of isotope data reported here may further improve our understanding of nitrogen cycle during haze.

Disentangling the role of shared ancestry and the environment on leaf stable isotopes

2019 ◽  
Author(s):  
Marko J. Spasojevic ◽  
Sören Weber1
Keyword(s):  
Stable Isotopes ◽  
Environmental Conditions ◽  
Evolutionary History ◽  
Environmental Control ◽  
Phylogenetic Signal ◽  
Individual Species ◽  
Habitat Types ◽  
Δ13c And Δ15n ◽  
Environmental Controls ◽  
Shared Ancestry

Stable carbon (C) and nitrogen (N) isotopes in plants are important indicators of plant water use efficiency and N acquisition strategies. While often regarded as being under environmental control, there is growing evidence that evolutionary history may also shape variation in stable isotope ratios (δ13C and δ15N) among plant species. Here we examined patterns of foliar δ13C and δ15N in alpine tundra for 59 species in 20 plant families. To assess the importance of environmental controls and evolutionary history, we examined if average δ13C and δ15N predictably differed among habitat types, if individual species exhibited intraspecific trait variation (ITV) in δ13C and δ15N, and if there were a significant phylogenetic signal in δ13C and δ15N. We found that variation among habitat types in both δ13C and δ15N mirrored well-known patterns of water and nitrogen limitation. Conversely, we also found that 40% of species exhibited no ITV in δ13C and 35% of species exhibited no ITV in δ15N, suggesting that some species are under stronger evolutionary control. However, we only found a modest signal of phylogenetic conservatism in δ13C and no phylogenetic signal in δ15N suggesting that shared ancestry is a weaker driver of tundra wide variation in stable isotopes. Together, our results suggest that both evolutionary history and local environmental conditions play a role in determining variation in δ13C and δ15N and that considering both factors can help with interpreting isotope patterns in nature and with predicting which species may be able to respond to rapidly changing environmental conditions.

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