Three methods to estimate N2O fluxes as impacted by agricultural management

1997 ◽  
Vol 77 (2) ◽  
pp. 125-134 ◽  
Author(s):  
D. L. Burton ◽  
D. W. Bergstrom ◽  
J. A. Covert ◽  
C. Wagner-Riddle ◽  
E. G. Beauchamp
Keyword(s):  
Flux Measurement ◽  
Soil Management ◽  
Surface Flux ◽  
Growing Season ◽  
Ex Situ ◽  
Concentration Gradients ◽  
Order Of Magnitude ◽  
Key Words Nitrous Oxide ◽  
Precipitation Events ◽  
Made In

This study examines three methods of evaluating N2O flux and accumulation in soil profile over a growing season under three soil management regimes (fallow, fallow with manure addition and cropped to alfalfa). Estimates of N2O flux were made based on measured soil atmosphere concentration gradients in the top 15 cm and compared to flux estimates based on ex situ cores and micro-meteorological measurements made in parallel studies. All methods indicated strong seasonal trends relating to precipitation events. The amounts of N2O accumulating the profile decreased in the order alfalfa < fallow < fallow/manure. The amounts of N2O accumulating in the profile ranged from ambient (0.35 µL L−1) to 490 µL L−1. Diffusion of N2O to the lower profile was shown to provide temporary storage of N2O and thereby provide the opportunity for further reduction to N2 prior to efflux from the surface. In comparing the estimates of surface flux, all three methods were of the same order of magnitude for the fallow site but profile-based estimates were much lower and much higher for fallow/manure and alfalfa sites, respectively. Differences were attributed to the location and timing of carbon addition in each system. Key words: Nitrous oxide, N2O, flux, measurement, soil, management

scholarly journals Tunable In Situ 3D-Printed PVDF-TrFE Piezoelectric Arrays

Sensors ◽  
2021 ◽  
Vol 21 (15) ◽  
pp. 5032
Author(s):  
Alec Ikei ◽  
James Wissman ◽  
Kaushik Sampath ◽  
Gregory Yesner ◽  
Syed N. Qadri
Keyword(s):  
3D Printing ◽  
Polyvinylidene Fluoride ◽  
Vinylidene Fluoride ◽  
Mechanical Strain ◽  
Pressure Sensors ◽  
Strain Ratio ◽  
Ex Situ ◽  
Order Of Magnitude ◽  
3D Printed

In the functional 3D-printing field, poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) has been shown to be a more promising choice of material over polyvinylidene fluoride (PVDF), due to its ability to be poled to a high level of piezoelectric performance without a large mechanical strain ratio. In this work, a novel presentation of in situ 3D printing and poling of PVDF-TrFE is shown with a d33 performance of up to 18 pC N−1, more than an order of magnitude larger than previously reported in situ poled polymer piezoelectrics. This finding paves the way forward for pressure sensors with much higher sensitivity and accuracy. In addition, the ability of in situ pole sensors to demonstrate different performance levels is shown in a fully 3D-printed five-element sensor array, accelerating and increasing the design space for complex sensing arrays. The in situ poled sample performance was compared to the performance of samples prepared through an ex situ corona poling process.

scholarly journals Surface flux measurement and modeling at a semi-arid Sonoran Desert site

1996 ◽  
Vol 82 (1-4) ◽  
pp. 119-153 ◽  
Author(s):  
Helene E. Unland ◽  
Paul R. Houser ◽  
William J. Shuttleworth ◽  
Zong-L. Yang
Keyword(s):  
Sonoran Desert ◽  
Flux Measurement ◽  
Surface Flux ◽  
Semi Arid

scholarly journals Increasing Crop Water Productivity through Local Crops and Technologies: A Case from the Ethnic Chepang Community of Nepal

2012 ◽  
pp. 50-53
Author(s):  
Bed P. Khatiwada ◽  
Rajan Ghimire ◽  
Rabindra Adhikari ◽  
Surendra Osti
Keyword(s):  
Indigenous Knowledge ◽  
Water Productivity ◽  
Soil Management ◽  
Special Issue ◽  
Crop Water ◽  
Crop Water Productivity ◽  
Sustainable Soil Management ◽  
Research And Education ◽  
Made In ◽  
Production Resource

Water is the most important and scarce production resource, and with changing climate the importance of this resource increases significantly. Increasing efforts are being made in research and education to maximize the water use efficiently with the concept of ‘crop per drop’ to increase crop water productivity with a good blend of science and indigenous knowledge. Nepalese farmers are adapting the best to water scarcity through adoption of sustainable soil management and the use of crops with minimum water requirement, among other options. This paper attempts to deal with the neglected issues of using local crops and indigenous knowledge and technologies for increasing water productivity.DOI: http://dx.doi.org/10.3126/hn.v11i1.7204 Hydro Nepal Special Issue: Conference Proceedings 2012 pp.50-53

Low Temperature Photoluminescence Studies of Narrow Bandgap Gaassbn Quantum Wells on GaAs

2002 ◽  
Vol 744 ◽  
Author(s):  
K.E. Waldrip ◽  
E.D. Jones ◽  
N.A. Modine ◽  
F. Jalali ◽  
J.F. Klem ◽  
...  
Keyword(s):  
Low Temperature ◽  
Quantum Wells ◽  
Band Gap ◽  
First Principles ◽  
Structure Calculation ◽  
Ex Situ ◽  
Band Structure Calculation ◽  
Narrow Bandgap ◽  
Order Of Magnitude ◽  
Photoluminescence Studies

We present low-temperature (T = 4K) photoluminescence studies of the effect of adding nitrogen to 6-nm-wide single-strained GaAsSb quantum wells on GaAs. The samples were grown by both MBE and MOCVD tech-niques. The nominal Sb concentration is about 30%. Adding about 1 to 2% N drastically reduced the bandgap energies from 1 to 0.75 eV, or 1.20 to 1.64 μm. Upon performing ex situ rapid thermal anneals, 825°C for 10s, the band gap energies as well as the photoluminescence intensities increased. The intensities increased by an order of magnitude for the annealed samples and the band gap energies increased by about 50 - 100 meV, depending on growth temperatures. The photoluminescence linewidths tended to decrease upon annealing. Preliminary results of a first-principles band structure calculation for the GaAsSbN system are also presented.

scholarly journals Multifrequency target strength of northern krill (Meganyctiphanes norvegica) swimming horizontally

2011 ◽  
Vol 69 (1) ◽  
pp. 119-130 ◽  
Author(s):  
Lucio Calise ◽  
Tor Knutsen
Keyword(s):  
Length Distribution ◽  
Ex Situ ◽  
Target Strength ◽  
Acoustic Backscatter ◽  
Acoustic Measurements ◽  
Acoustic Beams ◽  
Meganyctiphanes Norvegica ◽  
Acoustic Identification ◽  
Made In

Abstract Calise, L., and Knutsen, T. 2012. Multifrequency target strength of northern krill (Meganyctiphanes norvegica) swimming horizontally. – ICES Journal of Marine Science, 69: 119–130. Multifrequency acoustic measurements on ex situ horizontally swimming krill were made in a novel experimental setting. An ensemble of northern krill (Meganyctiphanes norvegica) was introduced to a large enclosure (a mesocosm), and acoustic backscatter was sampled using a multifrequency (70, 120, and 200 kHz) echosounder (Simrad EK60). Two submerged lamps were placed at opposite sides of the mesocosm and switched on and off to induce the krill, by light attraction, to swim horizontally through the acoustic beams. By tracking echoes, animal displacement, swimming speed, and target strength (TS) by frequency were estimated. The dominant and secondary modes of the total-length distribution were 21.8 ± 3.0 and 27.8 ± 2.7 mm, respectively. Although krill orientation was assumed stable and the ping rate was high, the range and inter-ping variability of the average TS values were large, decreasing and increasing with frequency, respectively. The overall TS frequency response observed and concurrent measurements at 120 and 200 kHz confirm the theoretical expectation that the acoustic backscatter from the investigated organisms were confined to the Rayleigh and Geometric scattering regions, a finding that might both aid acoustic identification and size-group separation of in situ northern krill.

Comparisons of surface flux measurement systems used in FIFE 1989

1992 ◽  
Vol 97 (D17) ◽  
pp. 18697 ◽  
Author(s):  
L. J. Fritschen ◽  
P. Qian ◽  
E. T. Kanemasu ◽  
D. Nie ◽  
E. A. Smith ◽  
...  
Keyword(s):  
Flux Measurement ◽  
Surface Flux ◽  
Measurement Systems

scholarly journals Almond Leaf Scorch Disease Development on Almond Branches High-Grafted on Peach Rootstock

Plant Disease ◽  
2013 ◽  
Vol 97 (2) ◽  
pp. 277-281 ◽  
Author(s):  
Tiesen Cao ◽  
Theodore M. DeJong ◽  
Bruce C. Kirkpatrick
Keyword(s):  
Xylella Fastidiosa ◽  
Average Distance ◽  
Winter Season ◽  
Growing Season ◽  
Prunus Dulcis ◽  
Leaf Scorch ◽  
Second Year ◽  
Peach Rootstocks ◽  
Almond Leaf Scorch ◽  
Made In

Development of almond leaf scorch (ALS) disease was monitored on young almond (Prunus dulcis ‘NePlus’ and ‘Peerless’) shoots produced from almond scion wood that was high-grafted on peach rootstocks (P. persica ‘Queencrest/Nemaguard’), after the almond shoots were mechanically inoculated with Xylella fastidiosa. The objective of this study was to evaluate the potential movement of X. fastidiosa through almond–peach graft unions. ALS symptoms developed on both X. fastidiosa-inoculated and uninoculated almond shoots that were high-grafted on different peach limbs of the same tree in September following inoculations with X. fastidiosa made in June and July 2002, respectively, when the average distance in peach rootstock between the two almond–peach graft unions was 30.5 cm or shorter. No ALS symptoms were observed on uninoculated almond shoots late in the growing season of the second year. The incidence of ALS-affected leaves on shoots inoculated with X. fastidiosa decreased in the second year on the inoculated shoots of Peerless as determined by the number of inoculated shoots showing ALS symptoms in 2002 versus 2003. No visible ALS symptoms were observed in NePlus late in the growing season of the second year, suggesting that survival of X. fastidiosa in NePlus was less than in Peerless. These data demonstrate that movement of X. fastidiosa through two almond–peach graft unions was possible during the year of inoculation when the peach rootstock stem distance between the two almond–peach graft unions was minimal. However, X. fastidiosa may not survive the winter season or survived so poorly as not to be able to produce ALS symptoms in the second growing season on the uninoculated shoots that previously showed ALS symptoms in the fall of the year when an adjacent shoot was inoculated. The results suggest that high-grafting almond scion wood on multiple peach rootstock limbs may provide a means to limit movement of X. fastidiosa from one almond limb to another on the same tree.

scholarly journals Determining the sea-air flux of dimethylsulfide by eddy correlation using mass spectrometry

2009 ◽  
Vol 2 (4) ◽  
pp. 1973-2025 ◽  
Author(s):  
B. W. Blomquist ◽  
B. J. Huebert ◽  
C. W. Fairall
Keyword(s):  
Internal Standard ◽  
Flux Measurement ◽  
Surface Flux ◽  
Ambient Air ◽  
Eddy Correlation ◽  
Mass Spectrometric Measurement ◽  
Instrument Response Function ◽  
Measured Flux ◽  
True Surface ◽  
Significant Difference

Abstract. Mass spectrometric measurement of DMS by atmospheric pressure ionization with an isotopically labeled standard (APIMS-ILS) is a sensitive method with sufficient bandpass for direct flux measurements by eddy correlation. Use of an isotopically labeled internal standard greatly reduces instrumental drift, improving accuracy and precision. APIMS-ILS has been used in several recent campaigns to study ocean-atmosphere gas transfer and the chemical budget of DMS in the marine boundary layer. This paper provides a comprehensive description of the method and errors associated with DMS flux measurement from ship platforms. The APIMS-ILS instrument used by most groups today has a sensitivity of 100–200 counts s−1 pptv−1, which is shown to be more than sufficient for flux measurement by eddy covariance. Mass spectral backgrounds (blanks) are determined by stripping DMS from ambient air with gold. The instrument is found to exhibit some signal loss, with a half-power frequency of ≈1 Hz, but a correction based on an empirically determined instrument response function is presented. Standard micrometeorological assumptions of steady state and horizontal uniformity are found to be appropriate for DMS flux measurement, but rapid changes in mean DMS mixing ratio serve as a warning that measured flux may not represent the true surface flux. In addition, bias in surface flux estimates arising from the flux gradient are not generally significant, but conditions of lowered inversion and high surface flux may lead to a significant difference between measured flux and true surface flux. The effects of error in motion corrections and of vertical motion within the surface layer concentration gradient are discussed and the estimated maximum error from these effects is ≤18%.

scholarly journals The imprint of surface fluxes and transport on variations in total column carbon dioxide

2011 ◽  
Vol 8 (4) ◽  
pp. 7475-7524 ◽  
Author(s):  
G. Keppel-Aleks ◽  
P. O. Wennberg ◽  
R. A. Washenfelder ◽  
D. Wunch ◽  
T. Schneider ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Large Scale ◽  
Carbon Sink ◽  
Potential Temperature ◽  
Surface Flux ◽  
Growing Season ◽  
Temporal Variations ◽  
Surface Fluxes ◽  
Synoptic Scale ◽  
Meridional Gradient

Abstract. New observations of the vertically integrated CO2 mixing ratio, ⟨CO2⟩, from ground-based remote sensing show that variations in ⟨CO2⟩ are primarily determined by large-scale flux patterns. They therefore provide fundamentally different information than observations made within the boundary layer, which reflect the combined influence of large scale and local fluxes. Observations of both ⟨CO2⟩ and CO2 concentrations in the free troposphere show that large-scale spatial gradients induce synoptic-scale temporal variations in ⟨CO2⟩ in the Northern Hemisphere midlatitudes through horizontal advection. Rather than obscure the signature of surface fluxes on atmospheric CO2, these synoptic-scale variations provide useful information that can be used to reveal the meridional flux distribution. We estimate the meridional gradient in ⟨CO2⟩ from covariations in ⟨CO2⟩ and potential temperature, θ, a dynamical tracer, on synoptic timescales to evaluate surface flux estimates commonly used in carbon cycle models. We find that Carnegie Ames Stanford Approach (CASA) biospheric fluxes underestimate both the ⟨CO2⟩ seasonal cycle amplitude throughout the Northern Hemisphere midlatitudes as well as the meridional gradient during the growing season. Simulations using CASA net ecosystem exchange (NEE) with increased and phase-shifted boreal fluxes better reflect the observations. Our simulations suggest that boreal growing season NEE (between 45–65° N) is underestimated by ~40 % in CASA. We describe the implications for this large seasonal exchange on inference of the net Northern Hemisphere terrestrial carbon sink.

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