Chamber Methodology Research Articles

Human enteroid monolayers as a potential alternative for Ussing chamber and Caco-2 monolayers to study passive permeability and drug efflux.

After oral administration, the intestine is the first site of drug absorption, making it a key determinant of the bioavailability of a drug, and hence drug efficacy and safety. Existing non-clinical models of the intestinal barrier in vitro often fail to mimic the barrier and absorption of the human intestine. We explore if human enteroid monolayers are a suitable tool for intestinal absorption studies compared to primary tissue (Ussing chamber) and Caco-2 cells. Bidirectional drug transport was determined in enteroid monolayers, fresh tissue (Ussing chamber methodology) and Caco-2 cells. Apparent permeability (Papp) and efflux ratios for enalaprilat (paracellular), propranolol (transcellular), talinolol (P-glycoprotein (P-gp)) and rosuvastatin (Breast cancer resistance protein (BCRP)) were determined and compared between all three methodologies and across intestinal regions. Bulk RNA sequencing was performed to compare gene expression between enteroid monolayers and primary tissue. All three models showed functional efflux transport by P-gp and BCRP with higher basolateral to apical (B-to-A) transport compared to apical-to-basolateral (A-to-B). B-to-A Papp values were similar for talinolol and rosuvastatin in tissue and enteroids. Paracellular transport of enalaprilat was lower and transcellular transport of propranolol was higher in enteroids compared to tissue. Enteroids appeared show more region- specific gene expression compared to tissue. Fresh tissue and enteroid monolayers both show active efflux by P-gp and BCRP in jejunum and ileum. Hence, the use of enteroid monolayers represents a promising and versatile experimental platform to complement current in vitro models.

An Experimental Protocol for the Boyden Chamber Invasion Assay With Absorbance Readout.

The phenomenon of cell invasion is an essential step in angiogenesis, embryonic development, immune responses, and cancer metastasis. In the course of cancer progression, the ability of neoplastic cells to degrade the basement membrane and penetrate neighboring tissue (or blood vessels and lymph nodes) is an early event of the metastatic cascade. The Boyden chamber assay is one of the most prevalent methods implemented to measure the pro- or anti-invasive effects of drugs, investigate signaling pathways that modulate cell invasion, and characterize the role of extracellular matrix proteins in metastasis. However, the traditional protocol of the Boyden chamber assay has some technical challenges and limitations. One such challenge is that the endpoint of the assay involves photographing and counting stained cells (in multiple fields) on porous filters. This process is very arduous, requires multiple observers, and is very time-consuming. Our improved protocol for the Boyden chamber assay involves lysis of the dye-stained cells and reading the absorbance using an ELISA reader to mitigate this challenge. We believe that our improved Boyden chamber methodology offers a standardized, high-throughput format to evaluate the efficacy of various drugs and test compounds in influencing cellular invasion in normal and diseased states. We believe that our protocol will be useful for researchers working in the fields of immunology, vascular biology, drug discovery, cancer biology, and developmental biology. Key features • Measurement of tumor invasion using human cancer cells. • Ability to measure the pro-invasive/anti-invasive activity of small molecules and biological modifiers. • Measurement of chemotaxis, chemokines, trafficking of immune cells, and proteolytic activity of matrix metalloproteinases, lysosomal hydrolysates, collagenases, and plasminogen activators in physiological and pathological conditions. • Investigation of the role of extracellular matrix proteins in the crosstalk between endothelial, epithelial, muscle, or neuronal cells and their adjacent stroma.

9 Use of new technology to measure methane emissions

Abstract Over recent decades, the impact of human-induced climate change and the role of ruminant agriculture has been of growing concern for both the public and the scientific community. This has led to rapid advancements in technology needed to measure methane emissions accurately and precisely. Primarily, these advancements have been focused on measurements of enteric methane, with the proliferation of GreenFeed emission measurement systems (GEM; C-Lock, Inc; Rapid City, SD) being utilized by animal scientists across the world. The GEM relies on spot measurements collected in a portable head-box, either in a freestall or on a trailer. The GEM uses bait feed to entice animals to place their head into the head-box to collect measurements. Use of respiration chambers or head-boxes are still considered the “gold standard”, but the GEM allows for quantification in production environments and with greater number of animals. While enteric emissions are the primary source of methane from ruminant agriculture, manure methane emissions account for 15.8% of direct emissions from cattle in the U.S. This emission source is a significant contributor to confined feeding operations’ greenhouse gas emissions (GHG), where consolidation and changes in manure handling practices have occurred over the last several decades. From 2010 to 2020, manure methane emissions were a larger contributor to climate warming than enteric methane (90.8 MMT CO2-we vs. 89.2 MMT CO2-we, respectively) when calculated using the new GWP* metric. However, few advancements have been made in quantifying emissions from manure, with the cost-effective static chamber methodology still widely used. This technique allows for the determination of temporal gas concentration change in a known volume of air with a PVC cylinder, inserted 5-10 cm in the soil and posteriorly closed with a PVC lid to generate “known volume” headspace. However, this method does have known limitations on spatial and temporal flux calculations. These limitations include: the PVC chamber may alter the soil microenvironment thereby altering soil GHG flux estimates; they have potential for technician bias; and are short term monitoring, limiting interpretations to that snapshot in time and making comparisons across experiments difficult. Differing measuring techniques, such as eddy covariance and dual-comb, that more accurately and precisely monitor the soil-atmosphere interface may help better understand gas fluxes from livestock systems. Key Word: cattle, enteric, manure, methane

Controlled-release testing of the static chamber methodology for direct measurements of methane emissions

Abstract. Direct measurements of methane emissions at the component level provide the level of detail necessary for the development of actionable mitigation strategies. As such, there is a need to understand the magnitude of component-level methane emission sources and to test methane quantification methods that can capture methane emissions at the component level used in national inventories. The static chamber method is a direct measurement technique that has been applied to measure large and complex methane sources, such as oil and gas infrastructure. In this work, we compile methane emission factors from the Intergovernmental Panel on Climate Change (IPCC) Emission Factor Database in order to understand the magnitude of component-level methane flow rates, review the tested flow rates and measurement techniques from 40 controlled-release experiments, and perform 64 controlled-release tests of the static chamber methodology with mass flow rates of 1.02, 10.2, 102, and 512 g h−1 of methane. We vary the leak properties, chamber shapes, chamber sizes, and use of fans to evaluate how these factors affect the accuracy of the static chamber method. We find that 99 % of the component-level methane emission rates from the IPCC Emission Factor Database are below 100 g h−1 and that 77 % of the previously available controlled-release experiments did not test for methane mass flow rates below 100 g h−1. We also find that the static chamber method quantified methane flow rates with an overall accuracy of +14/-14 % and that optimal chamber configurations (i.e., chamber shape, volume, and use of fans) can improve accuracy to below ±5 %. We note that smaller chambers (≤20 L) performed better than larger-volume chambers (≥20 L), regardless of the chamber shape or use of fans. However, we found that the use of fans can substantially increase the accuracy of larger chambers, especially at higher methane mass flow rates (≥100 g h−1). Overall, our findings can be used to engineer static chamber systems for future direct measurement campaigns targeting a wide range of sources, including landfills, sewerage utility holes, and oil and natural gas infrastructure.

Active glucose transport varies by small intestinal region and oestrous cycle stage in mice.

What is the central question of this study? Body mass and food intake change during the female ovarian cycle: does glucose transport by the small intestine also vary? What is the main finding and its importance? We have optimised Ussing chamber methodology to measure region-specific active glucose transport in the small intestine of adult C57BL/6 mice. Our study provides the first evidence that jejunal active glucose transport changes during the oestrous cycle in mice, and is higher at pro-oestrus than oestrus. These results demonstrate adaptation in active glucose uptake, concurrent with previously reported changes in food intake. Food intake changes across the ovarian cycle in rodents and humans, with a nadir during the pre-ovulatory phase and a peak during the luteal phase. However, it is unknown whether the rate of intestinal glucose absorption also changes. We therefore mounted small intestinal sections from C57BL/6 female mice (8-9weeks old) in Ussing chambers and measured active ex vivo glucose transport via the change in short-circuit current (∆Isc ) induced by glucose. Tissue viability was confirmed by a positive ∆Isc response to 100µM carbachol following each experiment. Active glucose transport, assessed after addition of 5, 10, 25 or 45mM d-glucose to the mucosal chamber, was highest at 45mM glucose in the distal jejunum compared to duodenum and ileum (P<0.01). Incubation with the sodium-glucose cotransporter 1 (SGLT1) inhibitor phlorizin reduced active glucose transport in a dose-dependent manner in all regions (P<0.01). Active glucose uptake induced by addition of 45mM glucose to the mucosal chamber in the absence or presence of phlorizin was assessed in jejunum at each oestrous cycle stage (n=9-10 mice per stage). Overall, active glucose uptake was lower at oestrus compared to pro-oestrus (P=0.025). This study establishes an ex vivo method to measure region-specific glucose transport in the mouse small intestine. Our results provide the first direct evidence that SGLT1-mediated glucose transport in the jejunum changes across the ovarian cycle. The mechanisms underlying these adaptations in nutrient absorption remain to be elucidated.

Nitrous oxide flux from soil with Urochloa brizantha under nitrogen fertilization in Honduras

The emission of nitrous oxide is considerable in livestock systems, influenced by nitrogen fertilization and edaphoclimatic conditions. The aim of the research was to measure the flux of nitrous oxide (N2O) from the soil under Urochloa brizantha with nitrogen fertilization. In the pastures, a randomized complete block design was established with four replicates and three treatments, consisting of 2 m2 plots with U. brizantha fertilized with urea, bokashi and without fertilizer application. The gas samples were collected over three months between the rainy and dry seasons using the static closed chamber methodology. The samples related to the soil and plants were taken at a depth of 15 cm under undisturbed conditions every month, to quantify: gravimetric moisture, ammonium, nitrate, total carbon, total nitrogen, carbon/nitrogen ratio, and plant dry matter (DM). The ANAVA registered a significant difference between treatments for N2O, with the application of urea promoting higher accumulated flows (0.37 mg N2O m-2 h-1), followed by bokashi (0.34 mg N2O m-2 h-1) and lastly by the control (0.27 mg N2O m-2 h-1). The daily emission of the gas fluctuated in the rainy season, when soil moisture promoted higher emission peaks compared to the dry season. The fractions of nitrogen, carbon and DM were not affected by the treatments. The use of urea and the anaerobic conditions of soil due to the rains generated higher N2O values, while the organic amendment, bokashi, was the best alternative for the greenhouse gas mitigation and soil conservation.

190 Effects of Flooding on Grazed Pastures: Forage Quality, GHG Emissions and C Stocks

Abstract Manure creates hot spots of nutrients concentration, and consequently nutrient losses to air and water. In flood-prone areas these losses represent a major concern for environment. However, there is a gap on the understanding of the effects of recurring, short-term flooding on environmental and forage characteristics. This study evaluated the effects flooding on soil carbon (C) stock; and greenhouse gas (GHG) emissions (methane, CH4; nitrous oxide, N2O; and carbon dioxide, CO2) from soil; and forage dry matter and quality in flooded and non-flooded grazed pastures during four sampling periods (spring, early summer, late summer, and fall) of 2021. Soil samples were collected from 0-100cm, forage samples were cut at stubble height and soil greenhouse gases (GHG) emissions were monitored using the static chamber methodology. Preliminary results show trends of reduced forage digestibility in flooded pastures. No differences were observed on forage dry matter. Overall, there was no differences between CO2 emission from soil in flooded and non-flooded areas. Soil CH4 fluxes were primarily negative, and flooding seems to reduce the sink potential for CH4 from soil, except during early summer. For N2O the effects of season were very pronounced, increased emissions from spring to early summer and throughout fall in both flooded and non-flooded pastures. We did not observe any N2O sinks, and no difference between treatments. Flood-prone pastures had decreased C stock in comparison with non-flood pastures. Preliminary results show that forage production may represent a good option for flooded areas, since no effects were observed on mass and few effects on quality. However, flooding reduced C stock potential and CH4 sinks. A second sampling season will be performed in 2022 to further observe these results and allow for C-equivalent flux calculations. The balance between productivity and environmental impacts of flood-prone pastures will then be assessed.

PSI-3 Balance between Productivity and Environmental Impacts of Grazed and hay Fields

Abstract Animal production has been associated with environmental impacts, but meat and dairy demand continuously increases. Grazed and hayfields have been responsible for enteric methane emissions, but also identified as great C stocks. Sustainable intensification, or balance between sustainability and productivity, is sought and we need to better understand the trade-offs to design appropriate management strategies. This study evaluated effects of grazed pastures and hayfields on carbon (C) stocks; and on soil GHG emissions (methane, CH4; nitrous oxide, N2O; and carbon dioxide, CO2), and forage dry matter and quality during four sampling periods (spring, early summer, late summer, and fall) of 2021. Forage samples were cut at stubble height, soil GHG emissions were monitored using static chamber methodology, and soil samples were collected from 0-100 cm. During the growing season, hayfields presented higher forage quality and lower forage production than grazed pastures. In addition, grazed pastures presented higher soil C stocks than hayfields. Hayfields presented lower CO2 emissions from soil in comparison to grazed pastures, suggesting slower decomposition of organic matter, which could be associated to lower C stocks. On the other hand, hayfields presented lower GHG emissions in comparison to grazed pastures, when considering CH4 and N2O emissions. Overall, a clear trade-off between the two types of fields is observed. Grazed pastures seem to be adding more C stocks over time, but also emitting more GHG emissions. Forage quality was also reduced. Hayfields had lower GHG emissions, but also lower C stocks. Forage quality was greater. In terms of long-term ecosystems' resilience and climate change mitigation, C addition from grazed pastures is more beneficial. In an eventual C market development, where C credits could be used or sold, grazing systems would be in advantage, again due to greater C stocks even if emitting slightly higher GHG emissions.

A proof of concept using the Ussing chamber methodology to study pediatric intestinal drug transport and age-dependent differences in absorption.

Little is known about the impact of age on the processes governing human intestinal drug absorption. The Ussing chamber is a system to study drug transport across tissue barriers, but it has not been used to study drug absorption processes in children. This study aimed to explore the feasibility of the Ussing chamber methodology to assess pediatric intestinal drug absorption. Furthermore, differences between intestinal drug transport processes of children and adults were explored as well as the possible impact of age. Fresh terminal ileal leftover tissues from both children and adults were collected during surgery and prepared for Ussing chamber experiments. Paracellular (enalaprilat), transcellular (propranolol), and carrier‐mediated drug transport by MDR1 (talinolol) and BCRP (rosuvastatin) were determined with the Ussing chamber methodology. We calculated apparent permeability coefficients and efflux ratios and explored their relationship with postnatal age. The success rate for the Ussing chamber experiments, as determined by electrophysiological measurements, was similar between children (58%, N = 15, median age: 44 weeks; range 8 weeks to 17 years) and adults (67%, N = 13). Mean serosal to mucosal transport of talinolol by MDR1 and rosuvastatin by BCRP was higher in adult than in pediatric tissues (p = 0.0005 and p = 0.0091). In contrast, within our pediatric cohort, there was no clear correlation for efflux transport across different ages. In conclusion, the Ussing chamber is a suitable model to explore pediatric intestinal drug absorption and can be used to further elucidate ontogeny of individual intestinal pharmacokinetic processes like drug metabolism and transport.

Effect of nitrification inhibitor (DMPP) on nitrous oxide emissions from agricultural fields: Automated and manual measurements

Nitrogen fertilisation contributes significantly to the atmospheric increase of nitrous oxide (N2O). Application of nitrification inhibitors (NIs) is a promising strategy to mitigate N2O emissions and improve N-use efficiency in agricultural systems. This study investigated the effect of NI, 3,4-dimethylpyrazol phosphate (DMPP) on N2O mitigation from spring barley and spring oilseed rape. Manual and automatic chamber methodologies were used to capture spatial and temporal variability in N2O emissions. In a second experiment, we study the effect of N fertiliser levels without NI (0 %, 50 %, 100 %, 150 % and 200 % of recommended amount of N fertiliser), as well as 100 % of N with NI on N2O emissions in spring barley. The automated chamber measurements showed dynamics of N2O changes throughout the season, including positive and negative peaks that were unobservable with manual chambers due to low temporal resolution. Although not significant, application of NI tended to reduce N2O emissions. The reduction was on average 16 % in spring barley and 58 % in spring oilseed rape in manual chamber measurements. However, N2O reduction was 108 % in continuous automatic chamber measurements in spring barley. The N2O EFs for the growing season were very low (0.025 % to 0.148 %), with a greater reduction in EF in spring oilseed rape (76 %) than in spring barley (32 %) with NI application. A positive correlation (R = 80 %) was observed between N fertiliser levels and N2O emissions. Crop yield and crop N uptake were not significantly affected by the use of NI. This study highlighted that NI can reduce N2O emissions, but the reduction effects are plot, crop and microclimate specific. Long-term experiments with continuous plot-scale measurements are needed to capture and optimise N2O mitigation effect of NIs across wide variability in soils and microclimates in agroecosystems.

Low Omega-3 Levels in the Diet Disturbs Intestinal Barrier and Transporting Functions of Atlantic Salmon Freshwater and Seawater Smolts.

Due to a limited access to marine raw materials from capture fisheries, Atlantic salmon feeds are currently based on mainly plant ingredients (75%) while only 25% come from traditional marine ingredients including marine fish meal and fish oil. Thus, current feeds contain less of the essential omega-3 fatty acids. The aim of the study was to assess the impact of different omega-3 levels in fish feed on intestinal barrier and transporting functions of Atlantic salmon freshwater and seawater smolts. Atlantic salmon were fed three levels of omega-3 (2, 1 and 0.5%) and fish performance was followed through smoltification and the subsequent seawater acclimation. Intestinal barrier and transporting functions were assessed using Ussing chamber methodology and combined with transcript analysis of tight junction related proteins and ion transporters. A linear decrease in growth was observed with decreasing omega-3 levels. Low (0.5%) inclusion of omega-3 impaired the barrier function of the proximal intestine compared to 2% inclusion. Further, low levels of omega-3 decrease the transepithelial electrical potential across the epithelium indicating disturbed ion transport. It can be concluded that low dietary levels of omega-3 impair somatic growth and intestinal function of Atlantic salmon.

How to Improve Cumulative Methane and Nitrous Oxide Flux Estimations of the Non‐Steady‐State Chamber Method?

AbstractThe flux calculation schemes (FCSs) and gas sampling schemes (GSSs) determine the accuracy and representativeness of non‐steady‐state chamber measurements. The study aimed to provide guidelines on FCSs and GSSs to improve cumulative flux estimations of the non‐steady‐state chamber method. Based on a dataset obtained from automated chamber measurements in a permafrost‐affected wetland in northeast China, we evaluated the effects of FCSs and GSSs on cumulative methane and nitrous oxide flux estimates at the field scale. The evolution of chamber headspace gas concentrations was classified into five patterns, presenting the measurement disturbance and variation of non‐steady‐state chamber method. Three FCSs, that is, the sole use of linear model and hybrid use of linear with empirical quadratic and theoretical exponential models, were established on the basis of evolution patterns of chamber headspace gas concentrations. The hybrid FCSs were more robust for cumulative flux estimates than the sole FCS of the linear model. The flux dataset with the high spatiotemporal resolution was subsampled to simulate datasets obtained with different GSSs. The subsampling of flux dataset proved optimization of GSSs by allocating limited measurement resources to preferentially promote the spatial representativeness of measurements (e.g., with more replicate chambers and stratified chamber placement according to microtopographies), characterize the small‐scale spatiotemporal variability of fluxes (e.g., diurnal variation and spatial heterogeneity due to microtopographies), and capture the evolution pattern of chamber headspace gas concentrations, could effectively improve cumulative flux estimates at the field scale. Our guidelines on FCSs and GSSs can serve to the improvement of non‐steady‐state chamber methodology.

Nitrous oxide emissions in silvopastoral systems: Key driving variables and seasonality

Silvopastoral systems are suggested to be important strategies for mitigating greenhouse gas emissions. However, little information is available on the effects of these systems on soil nitrous oxide (N2O) production. Expanding the knowledge of N2O emissions and the responses of key variables that drive N2O production are essential for understanding nitrogen loss. To quantify these factors in the silvopastoral system (Eucalyptus grandis × Megathyrsus maximus) and the monoculture (Megathyrsus maximus Guinea Massai grass), we conducted a 4-year field assessment. The experimental design was a completely randomized block with two factors: (1) monoculture (MONO) and silvopastoral systems with tree rows of 12 m (SP1) and 6 m (SP2), and (2) two seasons (rainy and dry), with 5 repetitions. Emissions were quantified using the closed static chamber methodology and gas chromatography analysis. In the wet summer, the silvopasture system differed from MONO, while in the dry winter, only the SP1 group differed from the monoculture; N2O emissions were higher during the rainy season. The MONO treatment revealed larger N2O fluxes in the first year of evaluation, whereas the silvopasture systems peaked in a later year. A significant positive Pearson correlation was found between N2O fluxes and soil moisture (r=0.89; P < 0.001) and soil temperature (r=0.76; P< 0.01). Our study showed that the effect of the silvopastoral system was season-dependent. N2O emissions increased over the years in silvopastoral systems, as opposed to the monoculture, and were driven by soil moisture and temperature.

Checking the progress of using the static chamber method for the measurement of greenhouse gases in Latin America

Manual static chamber is one of the most widespread methods for the quantification of greenhouse gases (GHGs) emissions from agricultural systems. But there are concerns about the reliability of measurements and a necessity to assess the static chambers used in the studies performed in the countries of Latin America. Thus, this study aims to investigate the quality of the characteristics from the static chamber methodology, the confidence level of the GHG measurements, and recommend what should be improved. We conducted a systematic review of databases to identify peer-reviewed articles that used the static chamber method in Latin America. A total of 90 articles were analyzed and separated according to the publication year (2000-2008, 2009-2015, 2016-2020). We evaluated eight design and deployment chamber characteristics. The depth of base insertion and type of storage vial received the lowest scores, and the number of samples received the highest score. The description and reporting of the methodological procedures in the studies should be improved. The percentage of articles with high and medium confidence levels increased within the time, and the number of articles with low and very low confidence levels reduced. Scientists/Researchers should continue to follow the protocols, especially the most updated ones.

Abiotic and biotic factors contribute to CO2 exchange variation at the hourly scale in a semiarid maize cropland

Understanding the variables influencing the carbon budget in agricultural ecosystems is crucial for the prediction of future carbon dynamics. The purpose of this study was to identify the biotic and abiotic determinants of the net ecosystem CO2 exchange (NEE) and net assimilation rate (NPP) in a semiarid maize cropland. The CO2 exchange (NEE and NPP) was measured at different growth stages of maize plants using an improved chamber methodology. Heat map clustering of the correlation coefficients between CO2 exchange and its driving factors demonstrated that soil temperature and air humidity were positively correlated with CO2 emissions regardless of daytime or nighttime, while other factors affecting CO2 exchange were negatively correlated with emissions during daytime yet positively correlated during nighttime. The machine learning algorithm random forest (RF) and structural equation modeling (SEM) were used to analyze the effects of different factors on CO2 exchange. The RF analysis results indicated that for CO2 exchange in the daytime, photosynthetically active radiation (PAR) was the most important variable and presented an importance score of 0.574 for NEE and 0.558 for NPP. The SEM results indicated that in the daytime PAR exerted significant direct and indirect effects on both NEE and NPP, and the standardized direct and indirect effects were −0.668 and 0.022, respectively, for NEE, and the effects were 0.655 and −0.011, respectively for NPP. Like PAR, soil water content also exerted significant direct and indirect effects on both NEE and NPP, but the remaining factors affecting CO2 exchange only have one of the direct or indirect effects, sometimes neither. For CO2 exchange at night, the leaf area was the most important variable and presented an importance score of 0.72 for NEE and 0.45 for NPP. At night, both the direct and indirect effects of most abiotic factors on NEE and NPP were significant.

Assessment of the accuracy of open-circuit respiration chambers for measuring enteric methane emissions in cattle

Ruminants are the main source of methane emissions from the agricultural sector. Emission inventories and mitigation strategies require reliable technics of measurement. The respiration chamber methodology is a precise approach for measuring enteric methane emissions in cattle. A set of experiments was carried out to validate two respiration chambers for measuring enteric methane emissions of cattle. The chambers were calibrated considering three main components: the methane analyzer, the air duct and air extraction system, and the chamber itself, by evaluating linearity and response time of the analyzer, plateau variability and high purity methane recoveries in chambers. Recovery test calculations carried out after releasing high purity methane into the chambers gave calibration factors of 0.95 ± 0.05 and 1.03 ± 0.03 for the complete system of respirations chambers one and two, respectively, with corresponding uncertainties of 4.87 and 2.49%. Thus, the respiration chambers for enteric methane measurements of cattle at the University of Yucatan, Mexico function with precision and accuracy. This technique can be used to establish methane inventories and methane mitigation strategies in cattle.

A statistical approach to surface renewal: The virtual chamber concept

AbstractIn the stable conditions prevailing at night, concentrations of emitted gases (e.g., radon [Rn], carbon dioxide [CO2], methane [CH4], ammonia [NH3], and nitrous oxide [N2O]) build up at the surface, with intermittent interruptions due to the passage of packets of turbulence. The applicability of conventional experimental methods is then questionable. Here, a statistical approach is proposed, in which micrometeorological field data are used to replicate the likely characteristics of a chamber experiment, yielding estimates of surface fluxes at the surface itself with reduced requirement for adequate fetch. Application of the virtual chamber methodology to two recent field studies is explored: (a) a study of nocturnal CO2 emission from a farmland area in Ohio in 2015; and (b) an investigation of NH3 effluxes from a crop previously treated with urea ammonium nitrate (UAN) in Illinois in 2014. For both datasets, the virtual chamber approach yields results in general agreement with eddy covariance (EC) data.

Application of Hydrochar, Digestate, and Synthetic Fertilizer to a Miscanthus x giganteus Crop: Implications for Biomass and Greenhouse Gas Emissions

Miscanthus x giganteus (miscanthus), a perennial biomass crop, allocates more carbon belowground and typically has lower soil greenhouse gas (GHG) emissions than conventional feedstock crops, but best practices for nutrient management that maximize yield while minimizing soil GHG emissions are still debated. This study evaluated the effects of four different fertilization treatments (digestate from a biodigester, synthetic fertilizer (urea), hydrochar from the hydrothermal carbonization of digestate, and a control) on soil GHG emissions and biomass yield of an established miscanthus stand grown on abandoned agricultural land. Soil GHG fluxes (including CH4, CO2, and N2O) were sampled in all treatments using the static chamber methodology. Average biomass yield varied from 20.2 Mg ha−1 to 23.5 Mg ha−1, but there were no significant differences among the four treatments (p &gt; 0.05). The hydrochar treatment reduced mean CO2 emissions by 34% compared to the control treatment, but this difference was only statistically significant in one of the two sites tested. Applying digestate to miscanthus resulted in a CH4 efflux from the soil in one of two sites, while soils treated with urea and hydrochar acted as CH4 sinks in both sites. Overall, fertilization did not significantly improve biomass yield, but hydrochar as a soil amendment has potential for reducing soil GHG fluxes.

Global Research Alliance Sponsors New Nitrous Oxide Chamber Methodology Guidelines

CSA NewsVolume 65, Issue 11 p. 12-15 FEATURES Global Research Alliance Sponsors New Nitrous Oxide Chamber Methodology Guidelines DJ McCauley, DJ McCauleySearch for more papers by this author DJ McCauley, DJ McCauleySearch for more papers by this author First published: 27 October 2020 https://doi.org/10.1002/csan.20318Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Volume65, Issue11November 2020Pages 12-15 RelatedInformation

Global Research Alliance N2 O chamber methodology guidelines: Recommendations for deployment and accounting for sources of variability.

Adequately estimating soil nitrous oxide (N2 O) emissions using static chambers is challenging due to the high spatial variability and episodic nature of these fluxes. We discuss how to design experiments using static chambers to better account for this variability and reduce the uncertainty of N2 O emission estimates. This paper is part of a series, each discussing different facets of N2 O chamber methodology. Aspects of experimental design and sampling affected by spatial variability include site selection and chamber layout, size, and areal coverage. Where used, treatment application adds a further level of spatial variability. Time of day, frequency, and duration of sampling (both individual chamber closure and overall experiment duration) affect the temporal variability captured. We also present best practice recommendations for chamber installation and sampling protocols to reduce further uncertainty. To obtain the best N2 O emission estimates, resources should be allocated to minimize the overall uncertainty in line with experiment objectives. Sometimes this will mean prioritizing individual flux measurements and increasing their accuracy and precision by, for example, collecting four or more headspace samples during each chamber closure. However, where N2 O fluxes are exceptionally spatially variable (e.g., in heterogeneous agricultural landscapes, such as uneven and woody grazed pastures), using available resources to deploy more chambers with fewer headspace samples per chamber may be beneficial. Similarly, for particularly episodic N2 O fluxes, generated for example by irrigation or freeze-thaw cycles, increasing chamber sampling frequency will improve the accuracy and reduce the uncertainty of temporally interpolated N2 O fluxes.