An official website of the United States government
A collection of carbon dioxide (CO2), methane (CH4) gas flux and leaf area index (LAI) datasets from a temperate salt-marsh with S. alternifloria vegetation cover (39.09 ˚N, 75.44 ˚W). Measurements were collected from May 2020 through December of 2020 with 2 separate collection times per month for a total of 16 field sampling campaigns. Measurements were performed on 5 plots located within the footprint of an eddy covariance tower which collects ecosystem scale CO2 and CH4 fluxes (Ameriflux Site ID: StJ). Supporting measurements were also performed for leaf-level photosynthesis rates and plot LAI during each chamber campaign. </p> </p> The dark and light flux chambers each occupied 1.0 m2 ground area and the vegetation stand was fully enclosed by the chambers. The sediment chambers each occupied 0.025 m2 ground area and the vegetation stand was excluded from the chambers. CO2 and CH4 fluxes from all chambers were measured with a portable greenhouse gas analyzer (LGR Los Gatos Research, Model 915-0011, San Jose, CA) for approximately 2-3 min after chamber closure. The dark and soil chambers were 100% opaque while the light chamber allowed for 90% transmission of photosynthetically active radiation. Sediment fluxes and leaf-level photosynthesis was measured from 2 points within each of the larger chamber plots. Leaf-level photosynthesis was measured with a portable photosynthesis meter (Li-6400, Licor, Lincoln, NE) and LAI was measured with a ceptometer (Accupar LP80, Meter Inc, Pullman, WA, USA). All measurements were made consecutively over the span of 2-3 hours with leaf-level measurements preformed first, followed by light chambers, dark chambers, sediment chambers and plot LAI. </p> </p> </p>
more »
« less
Carbon-13 (13C) methane from an isotopic labelling experiment in Arctic tundra, Utqiagvik, Alaska, 2019.
An isotopic labeling experiment was conducted in an Arctic coastal wet tundra ecosystem to determine how quickly acetate is transformed into methane and transported from the soil to the atmosphere. Carbon-13 (13C) labelled acetate was injected into soil chambers installed across a 131 meter (m) transect. Gas samples were periodically collected from the headspace in chambers, and analyzed for methane concentration and enrichment in 13C. Methane flux was roughly estimated from the final concentration in the chambers accumulated over a one-hour sampling period. This dataset includes methane fluxes, concentrations and 13C enrichment values from this experiment. In addition, water samples were collected from 15 centimeters (cm) depth after the final time point for measurements of residual dissolved 13C-methane in the soil after 9 days.
more »
« less
- Award ID(s):
- 1702797
- PAR ID:
- 10310648
- Publisher / Repository:
- NSF Arctic Data Center
- Date Published:
- Subject(s) / Keyword(s):
- acetate methane
- Format(s):
- Medium: X Other: text/xml
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
DeGrandpre, Mike (Ed.)Abstract Dissolved gas concentrations in surface waters can have sharp gradients across marine and freshwater environments, which often prove challenging to capture with analytical measurement. Collecting discrete samples for laboratory analysis provides accurate results, but suffers from poor spatial resolution. To overcome this limitation, water equilibrators and gas membrane contactors (GMCs) have been used for the automated underway measurement of dissolved gas concentrations in surface water. However, while water equilibrators can provide continuous measurements, their analytical response times to changes in surface water concentration can be slow, lasting tens of minutes. This leads to spatial imprecisions in the dissolved gas concentration data. Conversely, while GMCs have proven to have much faster analytical response times, often lasting only a few minutes or less, they suffer from poor accuracy and thus require routine calibration. Here we present an analytical system for the high accuracy and high precision spatial mapping of dissolved methane concentration in surface waters. The system integrates a GMC with a cavity ringdown spectrometer for fast analytical response times, with a calibration method involving two Weiss‐style equilibrators and discrete measurements in vials. Data from both the GMC and equilibrators are collected simultaneously, with discrete vial samples collected periodically throughout data collection. We also present a mathematical algorithm integrating all data collected for the routine calibration of the GMC dataset. The algorithm facilitates comparison between the GMC and equilibrator datasets despite the substantial differences in response times (0.7–2.1 and 4.1–17.6 min, respectively). This measurement system was tested with both systematic laboratory experiments and field data collected on a research cruise along the US Atlantic margin. Once calibrated, this system identified numerous sharp peaks of dissolved methane concentration in the US Atlantic margin dataset that would be poorly resolved, or outright missed with previous measurement techniques. Overall, the precision and accuracy for the technique presented here were determined to be 11.2% and 10.4%, respectively, the operating range was 0–1000 ppm methane, and thee‐folding response time to changes in dissolved methane concentration was 0.7–2.1 min.more » « less
-
Efficient and sustainable biochemical production using low-cost waste assumes considerable industrial and ecological importance. Solid organic wastes (SOWs) are inexpensive, abundantly available resources and their bioconversion to volatile fatty acids, especially acetate, aids in relieving the requirements of pure sugars for microbial biochemical productions in industries. Acetate production from SOW that utilizes the organic carbon of these wastes is used as an efficient solid waste reduction strategy if the environmental factors are optimized. This study screens and optimizes influential factors (physical and chemical) for acetate production by a thermophilic acetogenic consortium using two SOWs—cafeteria wastes and corn stover. The screening experiment revealed significant effects of temperature, bromoethane sulfonate, and shaking on acetate production. Temperature, medium pH, and C:N ratio were further optimized using statistical optimization with response surface methodology. The maximum acetate concentration of 8061 mg L−1 (>200% improvement) was achieved at temperature, pH, and C:N ratio of 60 °C, 6, 25, respectively, and acetate accounted for more than 85% of metabolites. This study also demonstrated the feasibility of using acetate-rich fermentate (obtained from SOWs) as a substrate for the growth of industrially relevant yeast Yarrowia lipolytica, which can convert acetate into higher-value biochemicals.more » « less
-
Abstract Plastic liners are sometimes used with soil samplers in order to collect and store intact soil cores. Gaps at the soil–wall interface caused by the flexibility of plastic liners can result in wall flow, preventing accurate fluid flux density measurements. A subsampling method was developed to overcome problems with wall flow from soil samples collected with plastic liners in order to measure air permeability (ka) and saturated hydraulic conductivity (Ksat) on the intact cores. Subsamples were obtained after first immobilizing the soil within plastic liners by injecting expanding foam into the gaps between the soil and the liners. Once the soil was fixed in place, the soil samples were cut to the desired length, and sharpened metal rings were inserted into the original soil sample with a vise. With the metal ring at the desired depth, the subsample was removed from the original soil sample by cutting the liner and removing excess soil from the ends of the rings. Initial attempts to measurekaandKsaton samples within the original liners led to unrealistically high values because significant wall flow occurred. However, after implementing the improved subsampling approach, the measuredkaandKsatof the subsamples were within the range of expected values based on the literature. The subsampling method effectively eliminated wall flow on soil originally collected in plastic liners and is relatively easy to implement without the need for specialized tools.more » « less
-
Semi‐arid grasslands on the Mongolian Plateau are expected to experience high inputs of anthropogenic reactive nitrogen in this century. It remains unclear, however, how soil organisms and nutrient cycling are directly affected by N enrichment (i.e., without mediation by plant input to soil) vs. indirectly affected via changes in plant‐related inputs to soils resulting from N enrichment. To test the direct and indirect effects of N enrichment on soil organisms (bacteria, fungi and nematodes) and their associated C and N mineralization, in 2010, we designated two subplots (with plants and without plants) in every plot of a six‐level N‐enrichment experiment established in 1999 in a semi‐arid grassland. In 2014, 4 years after subplots with and without plant were established, N enrichment had substantially altered the soil bacterial, fungal and nematode community structures due to declines in biomass or abundance whether plants had been removed or not. N enrichment also reduced the diversity of these groups (except for fungi) and the soil C mineralization rate and induced a hump‐shaped response of soil N mineralization. As expected, plant removal decreased the biomass or abundance of soil organisms and C and N mineralization rates due to declines in soil substrates or food resources. Analyses of plant‐removal‐induced changes (ratios of without‐ to with‐plant subplots) showed that micro‐organisms and C and N mineralization rates were not enhanced as N enrichment increased but that nematodes were enhanced as N enrichment increased, indicating that the effects of plant removal on soil organisms and mineralization depended on trophic level and nutrient status. Surprisingly, there was no statistical interaction between N enrichment and plant removal for most variables, indicating that plant‐related inputs did not qualitatively change the effects of N enrichment on soil organisms or mineralization. Structural equation modelling confirmed that changes in soil communities and mineralization rates were more affected by the direct effects of N enrichment (via soil acidification and increased N availability) than by plant‐related indirect effects. Our results provide insight into how future changes in N deposition and vegetation may modify below‐ground communities and processes in grassland ecosystems.more » « less
