bLS Technique Research Articles

Measuring N2O Emissions from Multiple Sources Using a Backward Lagrangian Stochastic Model

Nitrous oxide (N2O) emissions from agricultural soil are substantially influenced by nitrogen (N) and field management practices. While routinely soil chambers have been used to measure emissions from small plots, measuring field-scale emissions with micrometeorological methods has been limited. This study implemented a backward Lagrangian stochastic (bLS) technique to simultaneously and near-continuously measure N2O emissions from four adjacent fields of approximately 1 ha each. A scanning open-path Fourier-transform infrared spectrometer (OP-FTIR), edge-of-field gas sampling and measurement, locally measured turbulence, and bLS emissions modeling were integrated to measure N2O emissions from four adjacent fields of maize production using different management in 2015. The maize N management treatments consisted of 220 kg NH3-N ha−1 applied either as one application in the fall after harvest or spring before planting or split between fall after harvest and spring before planting. The field preparation treatments evaluated were no-till (NT) and chisel plow (ChP). This study showed that the OP-FTIR plus bLS method had a minimum detection limit (MDL) of ±1.2 µg m−2 s−1 (3σ) for multi-source flux measurements. The average N2O emission of the four treatments ranged from 0.1 to 2.3 µg m−2 s−1 over the study period of 01 May to 11 June after the spring fertilizer application. The management of the full-N rate applied in the fall led to higher N2O emissions than the split-N rates applied in the fall and spring. Based on the same N application, the ChP practice tended to increase N2O emissions compared with NT. Advection of N2O from adjacent fields influenced the estimated emissions; uncertainty (1σ) in emissions was 0.5 ± 0.3 µg m−2 s−1 if the field of interest received a clean measured upwind background air, but increased to 1.1 ± 0.5 µg m−2 s−1 if all upwind sources were advecting N2O over the field of interest. Moreover, higher short-period emission rates (e.g., half-hour) were observed in this study by a factor of 1.5~7 than other micrometeorological studies measuring N2O-N loss from the N-fertilized cereal cropping system. This increment was attributed to the increase in N fertilizer input and soil temperature during the measurement. We concluded that this method could make near-continuous “simultaneous” flux comparisons between treatments, but further studies are needed to address the discrepancies in the presented values with other comparable N2O flux studies.

Computerized data mining analysis of keywords as indicators of the concepts in AHA-BLS guideline updates

IntroductionCardiopulmonary resuscitation (CPR) guidelines have been updated every 5 years since 2000. Significant changes have been made in each update, and every time a guideline is changed, the instructors of each country that ratify the American Heart Association (AHA) must review the contents of the revised guideline to understand the changes made in the concept of CPR. The purpose of this study was to use a computerized data mining method to identify and characterize the changes in the key concepts of the AHA-Basic Life Support (BLS) updates between 2000 and 2015. MethodsWe analyzed the guidelines of the AHA-BLS provider manual of 2000, 2005, 2010, and 2015 using a computerized data mining method and attempted to identify the changes in keywords along with changes in the guideline. ResultsIn particular, the 2000 guideline has focused on the detailed BLS technique of an individual health care provider, whereas the 2005 and 2010 guidelines have focused on changing the ratio of chest compressions and breathing and changing the BLS sequence, respectively. In the most recent 2015 guideline, the CPR team was the central topic. We observed that as the guidelines were updated over the years, keywords related to CPR and automated external defibrillators (AED) associated with co-occurrence network continued to appear. ConclusionsAnalysis revealed that keywords related to CPR and AED associated with the co-occurrence network continued to appear. We believe that the results of this study will ultimately contribute to optimizing AHA's educational strategies for health care providers.

Novel and effective arthroscopic extracapsular stabilization technique for anterior shoulder instability-BLS.

Arthroscopic Bankart repair for the treatment of anterior shoulder instability is associated with a high rate of recurrent instability. Extracapsular stabilization of the glenohumeral joint with enhancement of anterior wall soft tissues may be an effective alternative treatment technique. The aim of this study is to retrospectively assess clinical outcomes in the treatment of anterior shoulder instability using a novel technique of anterior extracapsular stabilization-"between glenohumeral ligaments and subscapularis tendon" (BLS). Patients with anterior shoulder instability who underwent surgical treatment with a novel arthroscopic BLS technique between 2008 and 2016 were eligible for inclusion. According to the level of glenoid bone loss, patients were separated into four groups. Group 1 comprised patients with GBL equal to or less than 5%, group 2 patients with GBL 6-10%, group 3 patients with GBL 11-15%, and group 4 patients with GBL > 15%. A positive outcome in this study was defined as full restoration of joint stability. To evaluate clinical results, preoperative range of ER and IR measured in 90 degrees of abduction were compared with ER and IR measured at final follow-up. Additional outcome instruments used consisted of the Constant Score and the Walch-Duplay Score. A total of 150 patients underwent arthroscopic BLS surgery. During the study period, 50 patients were lost to follow-up and 100 patients were available for final analysis. Mean patient age was 27.5 (± 10.3) years at the time of surgery. Mean duration of follow-up was 82.9 (± 29.4) months. At final assessment, 86 patients (86%) were categorized as having a positive outcome, with full restoration of joint stability. Recurrence of shoulder instability was observed in 14 (14%) patients, including 6 (6%) cases that were associated with major trauma. At final follow-up, the mean Constant Score was 88.2 ± 10.1, compared to 82.9 ± 9.1 preoperatively (p < 0.05). The mean final and mean preoperative Walch-Duplay Scores were 81.5 ± 18.9 and 52.2 ± 11.9, respectively (p < 0.05). There was no statistically significant limitation of external or internal rotation. The BLS technique has been shown to be an effective method to anterior shoulder instability in patients without significant glenoid bone loss. It was shown that this technique provides significant improvement in shoulder function without reducing shoulder range of motion. IV.

Comparing emissions from a cattle pen as measured by two micrometeorological techniques

Accurate measurement of ammonia (NH3) emissions from livestock pens is challenging. Two micrometeorological techniques, the integrated horizontal flux (IHF) and the backward Lagrangian stochastic (bLS) dispersion techniques were used to measure NH3 emissions from an isolated cattle pen (20 × 20 m) in Victoria, Australia. The bLS technique is simple and insensitive to the presence of animals, but typically gives discontinuous measurements due to the need for target wind directions and wind conditions above accepted thresholds. In contrast, the IHF technique as implemented here gives near-continuous measurements with no restriction on wind directions. However, IHF needs more complex field measurements, and there are ambiguities when applied to an animal pen due to the presence of animals. Over the 29 days of our experiment, we collected 124 coincidental bLS and IHF emission measurements from the pen (30−min each). We found no statistical difference in the bLS and IHF calculations when the IHF turbulent flux correction factor (TFcor) was set to 15%. Our results confirm that the IHF and bLS techniques, using independent sensors and having very different equipment layouts, gives nearly equivalent results. This suggests the choice of the two methods in future experiments can focus on their different strengths and weaknesses.

Ammonia and greenhouse gases emission from impermeable covered storage and land application of cattle slurry to bare soil

Handling a large volume of livestock wastes in intensive farm systems could lead to adverse environmental effects, such as excessive load of nutrients to the soil and gaseous losses into the atmosphere. Land spreading of animal manure is one of the sources of ammonia (NH3) volatilization in Europe. Livestock emissions from manure management in the form of greenhouse gases (GHG), i.e., methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O), amount to 15% of the total agricultural emissions. Therefore, it is important to address gas emissions during storage and following slurry land application to reduce the swapping of emissions from one stage of the manure management continuum to the next one. In this study, NH3 and GHG emissions were estimated from flexible bag storage and following cattle slurry band spreading and incorporation to soil. For this, the mass-balance integrated horizontal flux (IHF) technique was used based on NH3 concentration measurements from masts supporting passive flux samplers (PFS) at different heights and GHG concentrations from grab air samples. Furthermore, the backward Lagrangian stochastic (bLS) technique was compared with NH3 emission estimates from the IHF technique along the manure management continuum. On the whole, NH3 and GHG emissions were considered low from the flexible bag storage compared to those from uncovered lagoons reported in the literature. Slurry removal from storage led to higher NH3 and N2O emissions, representing 73% and 75% of total loss in storage, respectively. After slurry band application to soil, NH3 emission peaked within the first 10h. In overall, lower NH3 emissions were registered in land in the current study in comparison with studies testing broadcast application. Slurry land application led to higher CO2 and N2O emissions than covered storage, contributing to 75% and 99% of total emissions, respectively. Regarding results from the bLS technique, NH3 estimates were lower than expected, possibly due to the low emissions found following NH3 abatement strategies carried out in storage and fertilization stages, and insufficient plot coverage by the PFS under changing wind directions. Under occasional NH3 emissions due to manure management operations, the use of multiple downwind points in bLS resulted in more accurate results and better plot coverage compared to a single point. Average NH3 concentration and wind direction within 24h could result in uncertain bLS estimates under changing wind directions. Overall, the flexible bag storage was an effective method of gas emission mitigation in outdoor slurry storage. Slurry band spreading to bare soil lowered NH3 emissions, but a delay in incorporating slurry to soil could have reduced the efficacy of incorporation on NH3 abatement.

Optimal sensor locations for the backward lagrangian stochastic technique in measuring lagoon gas emission.

This study evaluated the impact of gas concentration and wind sensor locations on the accuracy of measuring gas emission rates from a lagoon environment using the backward Lagrangian stochastic (bLS) inverse-dispersion technique. Path-integrated concentrations (PICs) and three-dimensional (3D) wind vector data were collected at different locations within the lagoon landscape. A floating 45 m × 45 m perforated pipe network on an irrigation pond was used as a synthetic distributed emission source for the controlled release of methane. A total of 961 15-min datasets were collected under different atmospheric stability conditions over a 2-yr period. The PIC location had a significant impact on the accuracy of the bLS technique. The location of the 3D sonic anemometer was generally not a factor for the measured accuracies with the PIC positioned on the downwind berm. The PICs across the middle of the pond consistently produced the lowest accuracy with any of the 3D anemometer locations (<69% accuracy). The PICs located on the downwind berm consistently yielded the best bLS accuracy regardless of whether the 3D sonic anemometer was located on the upwind, side, or downwind berm (accuracies ranged from 79 to 108%). The accuracies of the emission measurements with the berm PIC-berm 3D setting were statistically similar to that found in a more ideal homogeneous grass field. Considering the practical difficulties of setting up equipment and the accuracies associated with various sensor locations, we recommend that wind and concentration sensors be located on the downwind berm.

Measuring methane emissions from two dairy farms: Seasonal and manure-management effects

There is a need to improve the understanding of methane (CH4) emissions on multiple spatial and temporal scales, and on a sector basis. Livestock are significant contributors to the CH4 budget, with emissions coming from enteric fermentation by ruminants and management of liquid manure. Inventory estimates for methane emissions are based on methodology that needs to be verified with actual on-farm measurements. Responding to these needs, the objectives of this study were to apply the backward Lagrangian Stochastic (bLS) technique on small dairy farms (50-100 lactating cows) and to examine its suitability to determine CH4 emissions from whole farms and partition emissions from cattle and manure. Measurement campaigns were selected to characterize the emission response to farm management activities and seasonal changes. At both farms the whole-farm emission rate was measured when the liquid manure storages were either full or emptied. Emissions from manure were substantial, and in the fall when the manure storage was full, 60% of the whole farm emissions came from the manure storage. Substantial seasonal differences in whole-farm emissions were observed, with fall season emissions being ∼40% higher than in the spring due to much higher manure emissions in the fall (673glactating-cow−1d−1) than the spring (249glactating-cow−1d−1). Peak emissions from stored manure were 47kgCH4h−1, (730glactating-cow−1h−1) during agitation. The enteric emission rate from the animals (after subtracting estimated barn floor emissions) showed clear diurnal variation and on a daily basis was similar for both seasons, ranging between 270 and 380glactating cow−1d−1. Implied Ym values were lower than the IPCC default value. Methane emissions from manure exhibited pronounced temporal variation on multiple time-frames and as a result, more research is needed to fully describe annual CH4 emissions from liquid manure management.

Large-chamber methane and nitrous oxide measurements are comparable to the backward lagrangian stochastic method.

Measurement of individual emission sources (e.g., animals or pen manure) within intensive livestock enterprises is necessary to test emission calculation protocols and to identify targets for decreased emissions. In this study, a vented, fabric-covered large chamber (4.5 × 4.5 m, 1.5 m high; encompassing greater spatial variability than a smaller chamber) in combination with on-line analysis (nitrous oxide [NO] and methane [CH] via Fourier Transform Infrared Spectroscopy; 1 analysis min) was tested as a means to isolate and measure emissions from beef feedlot pen manure sources. An exponential model relating chamber concentrations to ambient gas concentrations, air exchange (e.g., due to poor sealing with the surface; model linear when ≈ 0 m s), and chamber dimensions allowed data to be fitted with high confidence. Alternating manure source emission measurements using the large-chamber and the backward Lagrangian stochastic (bLS) technique (5-mo period; bLS validated via tracer gas release, recovery 94-104%) produced comparable NO and CH emission values (no significant difference at < 0.05). Greater precision of individual measurements was achieved via the large chamber than for the bLS (mean ± standard error of variance components: bLS half-hour measurements, 99.5 ± 325 μg CH s and 9.26 ± 20.6 μg NO s; large-chamber measurements, 99.6 ± 64.2 μg CH s and 8.18 ± 0.3 μg NO s). The large-chamber design is suitable for measurement of emissions from manure on pen surfaces, isolating these emissions from surrounding emission sources, including enteric emissions.

Evaluation of backward Lagrangian stochastic (bLS) model to estimate gas emissions from complex sources based on numerical simulations

The focus of the paper is application of an inverse-dispersion technique based on a backward Lagrangian stochastic (bLS) model in order to calculate gas-emission rates from industrial complexes. While the bLS technique is attractive for these types of sources, the bLS calculation must assume a spatial configuration for the source. Therefore, results are presented herein of numerical simulations designed to study the sensitivity of emissions calculations to the assumption of source configuration for complex industrial sources. We discuss how measurement fetch, concentration sensor height, and optical path length influence the accuracy of emission estimation. Through simulations, we identify an improved sensor configuration in order to reduce emission-calculation errors caused by an incorrect source-configuration assumption. It is concluded that, with respect to our defined source, the optimal measurement fetch may be between 200 m and 300 m; also, the ideal measurement height is probably between 2.0 m and 2.5 m. With choices within these two ranges, a path length of about 200 m is adequate, and greater path lengths, above 200 m, result in no substantial improvement in emission calculations.

Measuring Trace Gas Emission from Multi-Distributed Sources Using Vertical Radial Plume Mapping (VRPM) and Backward Lagrangian Stochastic (bLS) Techniques

Two micrometeorological techniques for measuring trace gas emission rates from distributed area sources were evaluated using a variety of synthetic area sources. The vertical radial plume mapping (VRPM) and the backward Lagrangian stochastic (bLS) techniques with an open-path optical spectroscopic sensor were evaluated for relative accuracy for multiple emission-source and sensor configurations. The relative accuracy was calculated by dividing the measured emission rate by the actual emission rate; thus, a relative accuracy of 1.0 represents a perfect measure. For a single area emission source, the VRPM technique yielded a somewhat high relative accuracy of 1.38 ± 0.28. The bLS technique resulted in a relative accuracy close to unity, 0.98 ± 0.24. Relative accuracies for dual source emissions for the VRPM and bLS techniques were somewhat similar to single source emissions, 1.23 ± 0.17 and 0.94 ± 0.24, respectively. When the bLS technique was used with vertical point concentrations, the relative accuracy was unacceptably low.

Use of an inverse dispersion technique for estimating ammonia emission from surface-applied slurry

Ammonia (NH 3) emission from land application of manure is typically measured using the integrated horizontal flux (IHF) micrometeorological method. However, there are some situations in which alternative techniques (such as an inverse dispersion modelling technique) might be preferable, for example when measuring from large or irregularly shaped source areas. In this study, an inverse dispersion technique using the backward Lagrangian stochastic (bLS) model, with 2 different experimental configurations, was compared with the Integrated Horizontal Flux method (i.e. IHF), which was used as reference technique. Pig slurry was surface-applied at 125 kg N ha −1 to bare soil on a large plot (80 × 125 m). Cumulative emissions were 19.3, 21.2 and 18.4 kg N ha −1 from the IHF and the bLS technique (experimental configurations I and II), respectively. Mean flux within each sampling period as estimated by the two techniques compared extremely well, with a slope not significantly different from 1 and r 2 of 0.99. Although limited in extent, this dataset agree with a previous study in demonstrating the use of the bLS technique with longer period time-averaged concentration measurements.

Comparison of a simplified micrometeorological mass difference technique and an inverse dispersion technique for estimating methane emissions from small area sources

In order to examine methodologies to quantify methane emissions from small surface sources, methane emissions from a ground level grid (3 m × 3 m) were estimated using a simplified micrometeorological mass difference (MMD) and an inverse dispersion technique (backward Lagrangian Stochastic model, bLS). Results indicated that the MMD and bLS techniques both provided accurate ensemble recoveries of 1.01 ( σ QMMD/ Q = 0.06) and 1.03 ( σ QbLS/ Q = 0.16), respectively. It was shown that in order to obtain accurate MMD estimates one must account for the turbulent component of the horizontal flux. This requires instantaneous measurements of wind speed and methane concentrations. Without this component (which is not typically measured), the MMD calculations overestimated the actual emissions by about 12% under very unstable conditions, 10% under moderately unstable conditions, and 7 and 8% under slightly unstable and near neutral conditions. Dispersion model simulations corroborated the overestimation with atmospheric stabilities and also indicated that this value varies with the distance between the source and the laser path. This study demonstrated that the MMD and the bLS techniques are both suitable for quantifying gas emissions from small area sources but the number of sensors required for the bLS technique is considerably less than for the MMD technique.

Simple use of the backwards Lagrangian stochastic dispersion technique for measuring ammonia emission from small field-plots

This study evaluates some simple procedures for measuring ammonia (NH 3) emission from wind speed, NH 3 concentration and an estimate of atmospheric stability using the backward Lagrangian stochastic (bLS) dispersion technique. The bLS technique, which requires measurements from only one height may prove useful when carrying out experiments simultaneously in a small field with several small plots. Commercial software exists that facilitates easy use of the bLS technique. Our study shows the bLS to be reliable using average wind speed at one height and average NH 3 concentration derived from horizontal flux measurements of NH 3 using passive flux samplers. The bLS technique underestimated the emission by 16–24% when applied at a measurement height of 0.5–1.55 m, but the inclination of bLS estimates versus integrated horizontal flux estimates was not different from 1 ( P < 0.01). The emission of NH 3 from urea applied to dry prairie soil was 29% of the nitrogen applied, emphasising the need of developing techniques for reducing NH 3 emission from zero tillage arable soils.

Techniques for measuring gas emissions from a composting stockpile of cattle manure

Abstract Feedlot manure is a source of atmospheric ammonia (NH 3 ), carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O), gases that are considered a risk to the environment. However, accurate estimates of emission of these gases from stockpiled manure are sparse due the lack of suitable measuring techniques. In our study, the integrated horizontal flux (IHF) and the backwards Lagrangian stochastical (bLS) dispersion micrometeorological techniques were adapted to measure gas emissions (NH 3 , CH 4 , N 2 O and CO 2 ) from a manure pile. The results were compared with measurements using the static chamber technique. Net horizontal gas fluxes were determined by mounting passive NH 3 samplers, gas intakes for CO 2 and CH 4 , and anemometers on poles that were always located up- and downwind of the pile as controlled by a wind vane. Further, NH 3 emission was estimated with the bLS technique using NH 3 concentration measured with a laser downwind of the pile. NH 3 emission measured with the IHF and bLS techniques were similar. Periodic measurements of emissions of CO 2 with the IHF technique by taking air samples with syringes and measuring CO 2 and CH 4 concentrations on a gas chromatograph, were similar to continuous measurements with the IHF technique measuring gas concentrations with an infrared gas monitor. Emissions of CO 2 , CH 4 and N 2 O measured with the static vented chamber technique were 12–22% of that measured with the IHF technique. Our results show that measurements of gas emission from stockpiled manure depend on the measuring technique and emphasizes the need for further validation of these techniques.