Regional characterization of N2O isotopic composition emitted from soils in view of land cover, agricultural management and annual cycles based on measurements and modeling

2020 ◽  
Author(s):  
Benjamin Wolf ◽  
Edwin Haas ◽  
David Kraus ◽  
Ralf Kiese ◽  
Klaus Butterbach-Bahl
Keyword(s):  
Isotopic Composition ◽  
Annual Cycle ◽  
Agricultural Soils ◽  
Temporal Trends ◽  
Agricultural Management ◽  
Biogeochemical Model ◽  
High Temporal Resolution ◽  
Global Budget ◽  
Model Based ◽  
Regional Estimates

<p>While the global budget of nitrous oxide (N<sub>2</sub>O) is rather well constrained from a “top-down” perspective considering the change in the atmospheric burden and stratospheric N<sub>2</sub>O destruction, estimates of the various sources such as natural/agricultural soils, coastal areas or fossil fuel burning and industry remain uncertain. The isotopic composition of N<sub>2</sub>O, i.e., the relative abundances of the four most abundant isotopic species (<sup>14</sup>N<sup>14</sup>N<sup>16</sup>O, <sup>15</sup>N<sup>14</sup>N<sup>16</sup>O, <sup>14</sup>N<sup>15</sup>N<sup>16</sup>O, and <sup>14</sup>N<sup>14</sup>N<sup>18</sup>O) have been identified as instrumental tools for attributing emissions to the corresponding production-consumption processes and to estimate the global budget. During the past two decades, N<sub>2</sub>O isotopic composition of individual sources has been investigated, and temporal trends in the isotopic composition of atmospheric N<sub>2</sub>O have been studied using and firn air and archived air samples collected in Antarctica. With regard to <sup>15</sup>N and <sup>18</sup>O in atmospheric N<sub>2</sub>O, a decreasing trend was consistently observed across studies, but contradictory results have been obtained for site preference (SP), i.e., the difference in the abundances of <sup>15</sup>N<sup>14</sup>N<sup>16</sup>O and <sup>14</sup>N<sup>15</sup>N<sup>16</sup>O relative to <sup>14</sup>N<sup>14</sup>N<sup>16</sup>O. In addition, N<sub>2</sub>O isotopic composition for natural or agricultural soils rely on a limited amount of studies and usually cover only parts of the annual cycle.</p><p>Since instruments used for optical isotope ratio spectroscopy (OIRS) can be deployed in the field, OIRS offers the opportunity to better characterize individual sources through long-term data in high temporal resolution. However, application of OIRS is challenging and, thus, remains scarce with regard to spatial resolution. For this reason, model-based regional estimates are pertinent to overcome the lack of regional estimates of N<sub>2</sub>O isotopic composition, to analyze trends, and to provide data for a refinement of the global budget.</p><p>To obtain regional-scale (Switzerland) model-based estimates of N<sub>2</sub>O isotopic composition, we used data sets of measured N<sub>2</sub>O isotopic composition of two sites that are based on OIRS, and applied the <strong>S</strong>table <strong>I</strong>sotope <strong>MO</strong>del for <strong>N</strong>utrient cycl<strong>E</strong>s, SIMONE in conjunction with the biogeochemical model LandscapeDNDC. Our results show that SIMONE/LandscapeDNDC was capable of reflecting especially SP, but also <sup>15</sup>N-N<sub>2</sub>O at sites with different soil properties. For agricultural soils, our simulations revealed an annual cycle in SP, with higher values during the growing season, but not for <sup>15</sup>N-N<sub>2</sub>O. We will also discuss effects of agricultural management on N<sub>2</sub>O emissions as well as temporal trends.</p>

scholarly journals Real-time observations of stable isotope dynamics during rainfall and throughfall events

2018 ◽  
Author(s):  
Barbara Herbstritt ◽  
Benjamin Gralher ◽  
Markus Weiler
Keyword(s):  
Isotopic Composition ◽  
Real Time ◽  
Temporal Resolution ◽  
Tree Canopy ◽  
Dead Volume ◽  
High Temporal Resolution ◽  
Time Lags ◽  
Mixing Processes ◽  
Hydrologic System ◽  
Time Observation

Abstract. The isotopic composition of throughfall is affected by complex exchange, enrichment, and mixing processes in the tree canopy. All interception processes occur simultaneously in space and time generating a complex pattern of throughfall in amount and isotopic composition. This pattern ultimately cascades through the entire hydrologic system and is therefore crucial for studies in catchment hydrology where recharge areas are often forested while reference meteorological stations are generally in the open. For the quasi real-time observation of the isotopic composition of both gross precipitation and throughfall we developed an approach combining an off-the-shelf membrane contactor (Membrana) with a laser-based Cavity Ring-Down Spectrometer (CRDS, Picarro), obtaining isotope readings every two seconds. For the continuous observation of the temporal effect of interception processes two setups with two CRDS instruments in parallel were used analysing gross precipitation and throughfall simultaneously. All devices were kept small to minimize dead volume and thereby, with time-lags of only four minutes, to increase the temporal resolution of isotope observations. Complementarily, meteorological variables were recorded in high temporal resolution at the same location. Comparing these high temporally resolved continuous measurements with discrete liquid or event-based bulk samples, this approach proves to be a powerful tool towards more insight in the very dynamic processes contributing to interception during rainfall events.

scholarly journals Model-Based Evaluation of Hydroelectric Dam’s Impact on the Seasonal Variabilities of POC in Coastal Ocean: A Case Study of Three Gorges Project

2019 ◽  
Vol 7 (9) ◽  
pp. 320 ◽  
Author(s):  
Chen ◽  
Liu ◽  
Xu ◽  
Wang
Keyword(s):  
Coastal Region ◽  
Surface Region ◽  
Changjiang Estuary ◽  
Biogeochemical Model ◽  
Three Gorges Project ◽  
Three Gorges ◽  
Organic Detritus ◽  
The Changjiang Estuary ◽  
Chl A ◽  
Model Based

Particulate organic carbon (POC) plays an important role in the global carbon cycle. The POC in the Changjiang Estuary and adjacent coastal region of the East China Sea (ECS) is dominated by riverine input and marine production and is significantly influenced by the three gorges project (TGP). A coupled physical–biogeochemical model was used to evaluate TGP’s impact on POC. The results demonstrate that TGP regulates the area influenced by diluted water and POC through direct river and sediment discharge and affects the ecosystem. From the early to later TGP construction periods, the surface region with high-POC concentration (>40 μmol L−1) decreases by 20.5% in area and 11.5% in concentration. Meanwhile, POC in the whole water column decreases from 19.5 to 17.8 μmol L−1. By contrast, the concentrations of chlorophyll-a (Chl-a) and related nutrients increase. A three end-member mixing model based on quasi-conservative temperature and salinity is used to quantify relative contributions of different water sources to POC in our research area. We also estimate the biological POC production by the difference between the physical-biogeochemical model predicted POC and three end-member model mixing POC. The result demonstrate that under the regulation of TGP in the later period, the decrease of sediment load increases water transparency, which favors photosynthesis and oceanic biological produced POC. In addition, over 70% of the areas have C/Chl-a > 200 and high C/N ratios, which are circumstantial evidences that organic detritus and terrestrial input sources still dominate in the Changjiang Estuary and adjacent coastal ECS but are influenced by TGP’s regulation.

scholarly journals Evolution of Severe and Nonsevere Convection Inferred from GOES-Derived Cloud Properties

2013 ◽  
Vol 52 (9) ◽  
pp. 2009-2023 ◽  
Author(s):  
John L. Cintineo ◽  
Michael J. Pavolonis ◽  
Justin M. Sieglaff ◽  
Andrew K. Heidinger
Keyword(s):  
Temporal Trends ◽  
Weather Radar ◽  
Severe Weather ◽  
False Alarms ◽  
High Temporal Resolution ◽  
Convective Initiation ◽  
Temporal Sampling ◽  
Cloud Properties ◽  
Storm Evolution ◽  
Echo Threshold

AbstractGeostationary satellites [e.g., the Geostationary Operational Environmental Satellite (GOES)] provide high temporal resolution of cloud development and motion, which is essential to the study of many mesoscale phenomena, including thunderstorms. Initial research on thunderstorm growth with geostationary imagery focused on the mature stages of storm evolution, whereas more recent research on satellite-observed storm growth has concentrated on convective initiation, often defined arbitrarily as the presence of a given radar echo threshold. This paper seeks to link the temporal trends in robust GOES-derived cloud properties with the future occurrence of severe-weather radar signatures during the development phase of thunderstorm evolution, which includes convective initiation. Two classes of storms (severe and nonsevere) are identified and tracked over time in satellite imagery, providing distributions of satellite growth rates for each class. The relationship between the temporal trends in satellite-derived cloud properties and Next Generation Weather Radar (NEXRAD)-derived storm attributes is used to show that this satellite-based approach can potentially be used to extend severe-weather-warning lead times (with respect to radar-derived signatures), without a substantial increase in false alarms. In addition, the effect of varying temporal sampling is investigated on several storms during a period of GOES super-rapid-scan operations (SRSOR). It is found that, from a satellite perspective, storms evolve significantly on time scales shorter than the current GOES operational scan strategies.

scholarly journals Effects of fertilization and stand age on N<sub>2</sub>O and NO emissions from tea plantations: A site-scale study in a subtropical region using a modified biogeochemical model

2020 ◽  
Author(s):  
Wei Zhang ◽  
Zhisheng Yao ◽  
Xunhua Zheng ◽  
Chunyan Liu ◽  
Rui Wang ◽  
...  
Keyword(s):  
Soil Ph ◽  
Process Model ◽  
Early Stage ◽  
Stand Age ◽  
Biogeochemical Model ◽  
N2o Emissions ◽  
Model Based ◽  
Ph Reduction ◽  
Tea Plantations ◽  
No Emissions

Abstract. To meet increasing demands, tea plantations are rapidly expanding in China. Although the emissions of nitrous oxide (N2O) and nitric oxide (NO) from tea plantations may be substantially influenced by soil pH reduction and intensive nitrogen fertilization, process model-based studies on this issue are still rare. In this study, the process-oriented biogeochemical model, Catchment Nutrient Management Model – DeNitrification-DeComposition (CNMM-DNDC), was modified by adding tea growth-related processes that may induce a soil pH reduction. Using a dataset for intensively managed tea plantations at a subtropical site, the performances of the original and modified models for simulating the emissions of both gases subject to different fertilization alternatives and stand ages were evaluated. Compared with the observations in early stage of a tea plantation, the original and modified models showed comparable performances for simulating the daily gas fluxes (with Nash-Sutcliffe index (NSI) of 0.10 versus 0.18 for N2O and 0.32 versus 0.33 for NO), annual emissions (with NSI of 0.81 versus 0.94 for N2O and 0.92 versus 0.94 for NO) and annual direct emission factors (EFds). The observations and simulations consistently demonstrated that short-term replacement of urea with oilcake stimulated N2O emissions by ~ 62 % and ~ 36 % and mitigated NO emissions by ~ 25 % and ~ 14 %, respectively. The model simulations resulted in a positive dependence of EFd of either gas against nitrogen doses, implicating the importance of model-based quantification of this key parameter for inventory. In addition, the modified model with pH-related scientific processes showed overall inhibitory effects on the gases emissions in the mid to later stages during a full tea lifetime. In conclusion, the modified CNMM-DNDC exhibits the potential for quantifying N2O and NO emissions from tea plantations under various conditions. Nevertheless, wider validation is still required for simulation of long-term soil pH variations and emissions of both gases from tea plantations.

scholarly journals Evaluation of a Model-Based Hemodynamic Monitoring Method in a Porcine Study of Septic Shock

2013 ◽  
Vol 2013 ◽  
pp. 1-17 ◽  
Author(s):  
James A. Revie ◽  
David Stevenson ◽  
J. Geoffrey Chase ◽  
Chris J. Pretty ◽  
Bernard C. Lambermont ◽  
...  
Keyword(s):  
Septic Shock ◽  
Right Ventricular ◽  
Temporal Trends ◽  
Systemic Resistance ◽  
Monitoring Method ◽  
Average Decrease ◽  
Model Based ◽  
Cardiovascular Models ◽  
Left And Right ◽  
Improved Model

Introduction. The accuracy and clinical applicability of an improved model-based system for tracking hemodynamic changes is assessed in an animal study on septic shock.Methods. This study used cardiovascular measurements recorded during a porcine trial studying the efficacy of large-pore hemofiltration for treating septic shock. Four Pietrain pigs were instrumented and induced with septic shock. A subset of the measured data, representing clinically available measurements, was used to identify subject-specific cardiovascular models. These models were then validated against the remaining measurements.Results. The system accurately matched independent measures of left and right ventricle end diastolic volumes and maximum left and right ventricular pressures to percentage errors less than 20% (except for the 95th percentile error in maximum right ventricular pressure) and allR2>0.76. An average decrease of 42% in systemic resistance, a main cardiovascular consequence of septic shock, was observed 120 minutes after the infusion of the endotoxin, consistent with experimentally measured trends. Moreover, modelled temporal trends in right ventricular end systolic elastance and afterload tracked changes in corresponding experimentally derived metrics.Conclusions. These results demonstrate that this model-based method can monitor disease-dependent changes in preload, afterload, and contractility in porcine study of septic shock.

Stocks and changes in organic carbon in Danish agricultural soils – role of bulk density and stone fractions

2021 ◽  
Author(s):  
Laura Sofie Harbo ◽  
Jørgen Eivind Olesen ◽  
Zhi Liang ◽  
Lars Elsgaard
Keyword(s):  
Organic Carbon ◽  
Bulk Density ◽  
Management Practices ◽  
Agricultural Soils ◽  
Soil Bulk Density ◽  
Agricultural Management ◽  
Specific Information ◽  
High Productivity ◽  
Soc Estimation ◽  
Sampling Campaign

&lt;p&gt;Soil organic carbon (SOC) is essential for soil fertility and further represents a global carbon stock with potential to control atmospheric CO&lt;sub&gt;2&lt;/sub&gt; concentrations. Due to intense agricultural management, SOC is decreasing in many parts of the world, meaning that the soils act as CO&lt;sub&gt;2&lt;/sub&gt; sources rather than CO&lt;sub&gt;2&lt;/sub&gt; sinks, which they could have the capacity to be. Therefore, it is important to identify pertinent agricultural management practices that allow for high productivity, but at the same time allow for carbon sequestration and increase in SOC.&lt;/p&gt;&lt;p&gt;In order to document changes in SOC, it is necessary to monitor SOC over decadal time scales, since changes occur slowly and are small as compared with existing stocks. The SOC content in Danish agricultural soils has been monitored at approx. 10-yr intervals (1986, 1997, 2009) since the first systematic national observations in 1986, where soils were sampled from a national 7 km x 7 km grid.&lt;/p&gt;&lt;p&gt;In 2018, a new sampling campaign was conducted from the national 7 km x 7 km grid and soils were analysed for SOC to 1 m depth. The procedures applied in 2018 allowed for more precise relocation of the sampling points from 2009 as compared to precision obtained during the period from 1986-2009. Further, measurements in 2018 included assessment of soil bulk density and stone content in the upper 0-50 cm, which was not measured previously. Thus, one of the aims of the study was to evaluate how more precise point-specific information on bulk density and stone fractions affected the calculated SOC stocks across different soil types and management practices.&lt;/p&gt;&lt;p&gt;The point-specific bulk density measured in 2018 were on average lower than the bulk densities used previously, which were retrieved from a database of texture-based soil classes. The volumetric stone fraction in the upper 0-50 cm was found to be &lt;5% for roughly 90% of the soils, whereas &lt;3% of the soils had stone fractions of &gt;10%. On average, the inclusion of point-specific bulk density and stone fractions lead to approx. 5% lower SOC estimation, with equal approximmately contribution from the two variables.&lt;/p&gt;

scholarly journals Convergent modelling of past soil organic carbon stocks but divergent projections

2015 ◽  
Vol 12 (14) ◽  
pp. 4373-4383 ◽  
Author(s):  
Z. Luo ◽  
E. Wang ◽  
H. Zheng ◽  
J. A. Baldock ◽  
O. J. Sun ◽  
...  
Keyword(s):  
Field Experiments ◽  
Environmental Changes ◽  
Agricultural Soils ◽  
Terrestrial Ecosystems ◽  
C Sequestration ◽  
Biogeochemical Model ◽  
Data Set ◽  
Soil C ◽  
C Stocks ◽  
Drying Conditions

Abstract. Soil carbon (C) models are important tools for understanding soil C balance and projecting C stocks in terrestrial ecosystems, particularly under global change. The initialization and/or parameterization of soil C models can vary among studies even when the same model and data set are used, causing potential uncertainties in projections. Although a few studies have assessed such uncertainties, it is yet unclear what these uncertainties are correlated with and how they change across varying environmental and management conditions. Here, applying a process-based biogeochemical model to 90 individual field experiments (ranging from 5 to 82 years of experimental duration) across the Australian cereal-growing regions, we demonstrated that well-designed optimization procedures enabled the model to accurately simulate changes in measured C stocks, but did not guarantee convergent forward projections (100 years). Major causes of the projection uncertainty were due to insufficient understanding of how microbial processes and soil C pool change to modulate C turnover. For a given site, the uncertainty significantly increased with the magnitude of future C input and years of the projection. Across sites, the uncertainty correlated positively with temperature but negatively with rainfall. On average, a 331 % uncertainty in projected C sequestration ability can be inferred in Australian agricultural soils. This uncertainty would increase further if projections were made for future warming and drying conditions. Future improvement in soil C modelling should focus on how the microbial community and its C use efficiency change in response to environmental changes, and better conceptualization of heterogeneous soil C pools and the C transformation among those pools.

scholarly journals First on-line isotopic characterization of N<sub>2</sub>O above intensively managed grassland

2015 ◽  
Vol 12 (8) ◽  
pp. 2517-2531 ◽  
Author(s):  
B. Wolf ◽  
L. Merbold ◽  
C. Decock ◽  
B. Tuzson ◽  
E. Harris ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Temporal Resolution ◽  
Isotopic Signature ◽  
Repeated Measurements ◽  
Spectrometric Analysis ◽  
High Temporal Resolution ◽  
Site Preference ◽  
Nitrifier Denitrification ◽  
Isotopic Characterization ◽  
Intensively Managed

Abstract. The analysis of the four main isotopic N2O species (14N14N16O, 14N15N16O, 15N14N16O, 14N14N18O) and especially the intramolecular distribution of 15N ("site preference", SP) has been suggested as a tool to distinguish source processes and to help constrain the global N2O budget. However, current studies suffer from limited spatial and temporal resolution capabilities due to the combination of discrete flask sampling with subsequent laboratory-based mass-spectrometric analysis. Quantum cascade laser absorption spectroscopy (QCLAS) allows the selective high-precision analysis of N2O isotopic species at trace levels and is suitable for in situ measurements. Here, we present results from the first field campaign, conducted on an intensively managed grassland site in central Switzerland. N2O mole fractions and isotopic composition were determined in the atmospheric surface layer (at 2.2 m height) at a high temporal resolution with a modified state-of-the-art laser spectrometer connected to an automated N2O preconcentration unit. The analytical performance was determined from repeated measurements of a compressed air tank and resulted in measurement repeatability of 0.20, 0.12 and 0.11‰ for δ15Nα, δ15Nβ and δ18O, respectively. Simultaneous eddy-covariance N2O flux measurements were used to determine the flux-averaged isotopic signature of soil-emitted N2O. Our measurements indicate that, in general, nitrifier-denitrification and denitrification were the prevalent sources of N2O during the campaign and that variations in isotopic composition were due to alterations in the extent to which N2O was reduced to N2 rather than to other pathways, such as hydroxylamine oxidation. Management and rewetting events were characterized by low values of the intramolecular 15N site preference (SP), δ15Nbulk and δ18O, suggesting that nitrifier-denitrification and incomplete heterotrophic bacterial denitrification responded most strongly to the induced disturbances. The flux-averaged isotopic composition of N2O from intensively managed grassland was 6.9 ± 4.3, −17.4 ± 6.2 and 27.4 ± 3.6‰ for SP, δ15Nbulk and δ18O, respectively. The approach presented here is capable of providing long-term data sets also for other N2O-emitting ecosystems, which can be used to further constrain global N2O inventories.

Bioaccessible selenium in Italian agricultural soils: Comparison of the biogeochemical approach with a regression model based on geochemical and pedoclimatic variables

2007 ◽  
Vol 376 (1-3) ◽  
pp. 160-177 ◽  
Author(s):  
Massimo Spadoni ◽  
Mario Voltaggio ◽  
Marina Carcea ◽  
Ettore Coni ◽  
Andrea Raggi ◽  
...  
Keyword(s):  
Regression Model ◽  
Agricultural Soils ◽  
Model Based

scholarly journals Precipitation regime and stable isotopes at Dome Fuji, East Antarctica

2016 ◽  
Vol 16 (11) ◽  
pp. 6883-6900 ◽  
Author(s):  
Anna Dittmann ◽  
Elisabeth Schlosser ◽  
Valérie Masson-Delmotte ◽  
Jordan G. Powers ◽  
Kevin W. Manning ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Annual Cycle ◽  
Source Region ◽  
Precipitation Event ◽  
Deuterium Excess ◽  
Antarctic Plateau ◽  
Moisture Source ◽  
The Antarctic ◽  
The Impact ◽  
Precipitation Events

Abstract. A unique set of 1-year precipitation and stable water isotope measurements from the Japanese Antarctic station, Dome Fuji, has been used to study the impact of the synoptic situation and the precipitation origin on the isotopic composition of precipitation on the Antarctic Plateau. The Antarctic Mesoscale Prediction System (AMPS) archive data are used to analyse the synoptic situations that cause precipitation. These situations are investigated and divided into five categories. The most common weather situation during a precipitation event is an upper-level ridge that extends onto the Antarctic Plateau and causes strong northerly advection from the ocean. Most precipitation events are associated with an increase in temperature and wind speed, and a local maximum of δ18O. During the measurement period, 21 synoptically caused precipitation events caused 60 % of the total annual precipitation, whereas the remaining 40 % were predominantly attributed to diamond dust. By combining the synoptic analyses with 5-day back-trajectories, the moisture source regions for precipitation events were estimated. An average source region around a latitude of 55° S was found. The atmospheric conditions in the source region were used as initial conditions for running a Rayleigh-type isotopic model in order to reproduce the measured isotopic composition of fresh snow and to investigate the influence of the precipitation source region on the isotope ratios. The model represents the measured annual cycle of δ18O and the second-order isotopic parameter deuterium excess reasonably well, but yields on average too little fractionation along the transport/cooling path. While simulations with an isotopic general circulation model (GCM) (ECHAM5-wiso) for Dome Fuji are on average closer to the observations, this model cannot reproduce the annual cycle of deuterium excess. In the event-based analysis, no evidence of a correlation of the measured deuterium excess with the latitude of the moisture source region or the corresponding conditions was identified. Contrary to the assumption used for decades in ice core studies, a more northerly moisture source does not necessarily mean a larger temperature difference between source area and deposition site, thus a more depleted precipitation in heavy isotopes with a higher deuterium excess.

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