Trace Gas Dynamics Research Articles

Deciphering Gas Dynamics and Star Formation in a z = 1.1 Main-sequence Spiral Galaxy with ALMA and JWST

Abstract We present a joint analysis of high-resolution CO(2–1) and Paschen-α (Paα) emission lines to trace gas dynamics and spatially resolved star formation in ASPECS-LP.3 mm.06, a z = 1.1 main-sequence galaxy. Utilizing data from the Atacama Large Millimeter/submillimeter Array and JWST NIRCam wide field slitless spectroscopy, we explore both ionized gas and molecular gas within this galaxy. With a substantial molecular gas fraction (f mol = 0.44 ± 0.02), ASPECS-LP.3 mm.06 remains on the star-forming main sequence and adheres to the Kennicutt–Schmidt relation, indicating typical gas-to-star conversion efficiency. Our analysis reveals extended structures across multiple wavelengths, suggesting regulated star formation within a stable disk. The spatially resolved star formation efficiency and kinematic analysis indicate that ASPECS-LP.3mm.06 features a smooth mass assembly process across the bulge and disk. Additionally, the galaxy exhibits modest dust extinction (A V = 0.8), potentially linked to self-regulation during bulge formation. These findings position ASPECS-LP.3mm.06 as a prototypical galaxy, offering valuable insights into the mechanisms governing normal disk galaxy growth at z ∼ 1.

Upwelling-induced trace gas dynamics in the Baltic Sea inferred from 8 years of autonomous measurements on a ship of opportunity

Abstract. Autonomous measurements aboard ships of opportunity (SOOP) provide in situ data sets with high spatial and temporal coverage. In this study, we use 8 years of carbon dioxide (CO2) and methane (CH4) observations from SOOP Finnmaid to study the influence of upwelling on trace gas dynamics in the Baltic Sea. Between spring and autumn, coastal upwelling transports water masses enriched with CO2 and CH4 to the surface of the Baltic Sea. We study the seasonality, regional distribution, relaxation, and interannual variability in this process. We use reanalysed wind and modelled sea surface temperature (SST) data in a newly established statistical upwelling detection method to identify major upwelling areas and time periods. Large upwelling-induced SST decrease and trace gas concentration increase are most frequently detected around August after a long period of thermal stratification, i.e. limited exchange between surface and underlying waters. We found that these upwelling events with large SST excursions shape local trace gas dynamics and often lead to near-linear relationships between increasing trace gas levels and decreasing temperature. Upwelling relaxation is mainly driven by mixing, modulated by air–sea gas exchange, and possibly primary production. Subsequent warming through air–sea heat exchange has the potential to enhance trace gas saturation. In 2015, quasi-continuous upwelling over several months led to weak summer stratification, which directly impacted the observed trace gas and SST dynamics in several upwelling-prone areas. Trend analysis is still prevented by the observed high variability, uncertainties from data coverage, and long water residence times of 10–30 years. We introduce an extrapolation method based on trace gas–SST relationships that allows us to estimate upwelling-induced trace gas fluxes in upwelling-affected regions. In general, the surface water reverses from CO2 sink to source, and CH4 outgassing is intensified as a consequence of upwelling. We conclude that SOOP data, especially when combined with other data sets, enable flux quantification and process studies addressing the process of upwelling on large spatial and temporal scales.

How do velocity structure functions trace gas dynamics in simulated molecular clouds?

Context. Supersonic disordered flows accompany the formation and evolution of molecular clouds (MCs). It has been argued that this is turbulence that can support against gravitational collapse and form hierarchical sub-structures. Aims. We examine the time evolution of simulated MCs to investigate: What physical process dominates the driving of turbulent flows? How can these flows be characterised? Are they consistent with uniform turbulence or gravitational collapse? Do the simulated flows agree with observations? Methods. We analysed three MCs that have formed self-consistently within kiloparsec-scale numerical simulations of the interstellar medium (ISM). The simulated ISM evolves under the influence of physical processes including self-gravity, stratification, magnetic fields, supernova-driven turbulence, and radiative heating and cooling. We characterise the flows using velocity structure functions (VSFs) with and without density weighting or a density cutoff, and computed in one or three dimensions. However, we do not include optical depth effects that can hide motions in the densest gas, limiting comparison of our results with observations. Results. In regions with sufficient resolution, the density-weighted VSFs initially appear to follow the expectations for uniform turbulence, with a first-order power-law exponent consistent with Larson’s size-velocity relationship. Supernova blast wave impacts on MCs produce short-lived coherent motions at large scales, increasing the scaling exponents for a crossing time. Gravitational contraction drives small-scale motions, producing scaling coefficients that drop or even turn negative as small scales become dominant. Removing the density weighting eliminates this effect as it emphasises the diffuse ISM. Conclusions. We conclude that two different effects coincidentally reproduce Larson’s size velocity relationship. Initially, uniform turbulence dominates, so the energy cascade produces VSFs that are consistent with Larson’s relationship. Later, contraction dominates and the density-weighted VSFs become much shallower or even inverted, but the relationship of the global average velocity dispersion of the MCs to their radius follows Larson’s relationship, reflecting virial equilibrium or free-fall collapse. The injection of energy by shocks is visible in the VSFs, but decays within a crossing time.

Spatio-temporal variability and controls on methane and nitrous oxide in the Guadalquivir Estuary, Southwestern Europe

Estuaries are significant methane (CH4) and nitrous oxide (N2O) emitters, although dynamics of both greenhouse gases in these ecosystems are regulated by complex processes. In this work, we aimed at characterizing the spatio-temporal distribution of CH4 and N2O in the Guadalquivir river estuary (SW Spain), the southernmost European estuary. During eight sampling cruises conducted between 2016 and 2017, surface water CH4 and N2O concentrations were measured along the salinity gradient of the estuary by using static-head space equilibration gas chromatography. The CH4 and N2O saturation ranges over the estuarine transect were 520–30,800% (average 2285%) and 40–390% (average 183%), respectively and air–water fluxes ranged from 13 to 1000 µmol m− 2 day− 1(average 66.2 µmol m− 2 day− 1) for CH4 and from − 7 to 35 µmol m− 2 day− 1 (average 8.5 µmol m− 2 day− 1) for N2O. A slight increase in the emissions was detected upstream and no seasonal trends were observed. Mixing between freshwater and oceanic waters influenced biogeochemistry of estuarine waters, affecting CH4 and N2O fluxes. In order to identify potential sources of CH4 and N2O, biogeochemical parameters involved in the formation pathways of both gases, such as salinity, dissolved oxygen, nutrients and organic matter were analyzed. Results suggested that sulfate inhibition and microbial oxidation played a relevant role in dissolved CH4 accumulation in the water column whereas associations found between N2O, nitrate and oxygen indicated that nitrification was a major source of this gas. Therefore, the influence of the tidal-fluvial interaction on ecosystem metabolism regulates trace gas dynamics in the Guadalquivir estuary.

Passive sampling method for high‐resolution concentration and isotopic composition of dissolved methane in Arctic lakes

AbstractLakes are important sources of methane (CH4), accounting for 6–16% of natural global CH4 emissions annually. Vertical spatial resolution of CH4 sampling in the water column of lakes is limited because of physical dimensions of sampling devices and sampling‐induced mixing. To improve pool‐size estimates of carbon, diffusive flux calculations for CH4, and detailed mechanistic understanding of CH4 dynamics in lakes, more precise vertical profiles of dissolved gases through the water column are vital. We investigate the use of commercially available passive diffusion bags (PDBs) to obtain highly resolved (0.5‐m increments) vertical profiles of dissolved CH4 concentrations and isotopic composition (δ13 ). Laboratory experiments determined PDB equilibration time was between 5 d and 9 d for both CH4 concentration and δ13 . During July 2013, PDBs were deployed at intervals of 0.5‐m depth for 5 d in two lakes located < 5 km from the southwestern margin of the Greenland ice cap. Data from PDB samples were compared with samples collected using a submersible, electric pump. In both lakes, PDB and pump samples yielded vertical profiles for CH4 concentration and δ13 that were in close agreement (CH4 concentration R2 = 0.998, p < 0.001; δ13 R2 = 0.970, p < 0.001). Overall agreement between PDB and pump samples verifies the applicability of the PDB approach to dissolved CH4 sampling. High‐vertical resolution sampling of dissolved gas concentrations and isotopic composition using PDBs can provide more accurate estimates of pool sizes and diffusive fluxes that advance understanding of production, consumption, and emission processes controlling trace gas dynamics in lacustrine environments under warming climate.

A microbial functional group‐based module for simulating methane production and consumption: Application to an incubated permafrost soil

AbstractAccurately estimating methane (CH4) flux in terrestrial ecosystems is critically important for investigating and predicting biogeochemistry‐climate feedbacks. Improved simulations of CH4 flux require explicit representations of the microbial processes that account for CH4 dynamics. A microbial functional group‐based module was developed, building on the decomposition subroutine of the Community Land Model 4.5. This module considers four key mechanisms for CH4 production and consumption: methanogenesis from acetate or from single‐carbon compounds and CH4 oxidation using molecular oxygen or other inorganic electron acceptors. Four microbial functional groups perform these processes: acetoclastic methanogens, hydrogenotrophic methanogens, aerobic methanotrophs, and anaerobic methanotrophs. This module was used to simulate dynamics of carbon dioxide (CO2) and CH4 concentrations from an incubation experiment with permafrost soils. The results show that the model captures the dynamics of CO2 and CH4 concentrations in microcosms with top soils, mineral layer soils, and permafrost soils under natural and saturated moisture conditions and three temperature conditions of −2°C, 3°C, and 5°C (R2 > 0.67; P < 0.001). The biases for modeled results are less than 30% across the soil samples and moisture and temperature conditions. Sensitivity analysis confirmed the importance of acetic acid's direct contribution as substrate and indirect effects through pH feedback on CO2 and CH4 production and consumption. This study suggests that representing the microbial mechanisms is critical for modeling CH4 production and consumption; it is urgent to incorporate microbial mechanisms into Earth system models for better predicting trace gas dynamics and the behavior of the climate system.

Pivotal roles of phyllosphere microorganisms at the interface between plant functioning and atmospheric trace gas dynamics.

The phyllosphere, which lato sensu consists of the aerial parts of plants, and therefore primarily, of the set of photosynthetic leaves, is one of the most prevalent microbial habitats on earth. Phyllosphere microbiota are related to original and specific processes at the interface between plants, microorganisms and the atmosphere. Recent –omics studies have opened fascinating opportunities for characterizing the spatio-temporal structure of phyllosphere microbial communities in relation with structural, functional, and ecological properties of host plants, and with physico-chemical properties of the environment, such as climate dynamics and trace gas composition of the surrounding atmosphere. This review will analyze recent advances, especially those resulting from environmental genomics, and how this novel knowledge has revealed the extent of the ecosystemic impact of the phyllosphere at the interface between plants and atmosphere.Highlights• The phyllosphere is one of the most prevalent microbial habitats on earth.• Phyllosphere microbiota colonize extreme, stressful, and changing environments.• Plants, phyllosphere microbiota and the atmosphere present a dynamic continuum.• Phyllosphere microbiota interact with the dynamics of volatile organic compounds and atmospheric trace gasses.

Tidal controls on trace gas dynamics in a seagrass meadow of the Ria Formosa lagoon (southern Portugal)

Abstract. Coastal zones are important source regions for a variety of trace gases, including halocarbons and sulfur-bearing species. While salt marshes, macroalgae and phytoplankton communities have been intensively studied, little is known about trace gas fluxes in seagrass meadows. Here we report results of a newly developed dynamic flux chamber system that can be deployed in intertidal areas over full tidal cycles allowing for highly time-resolved measurements. The fluxes of CO2, methane (CH4) and a range of volatile organic compounds (VOCs) showed a complex dynamic mediated by tide and light. In contrast to most previous studies, our data indicate significantly enhanced fluxes during tidal immersion relative to periods of air exposure. Short emission peaks occurred with onset of the feeder current at the sampling site. We suggest an overall strong effect of advective transport processes to explain the elevated fluxes during tidal immersion. Many emission estimates from tidally influenced coastal areas still rely on measurements carried out during low tide only. Hence, our results may have significant implications for budgeting trace gases in coastal areas. This dynamic flux chamber system provides intensive time series data of community respiration (at night) and net community production (during the day) of shallow coastal systems.

Strong spatial variability in trace gasdynamics following experimental drought in a humid tropical forest

Soil moisture is a key driver of biogeochemical processes in terrestrial ecosystems, strongly affecting carbon (C) and nutrient availability as well as trace gas production and consumption in soils. Models predict increasing drought frequency in tropical forest ecosystems, which could feed back on future climate change directly via effects on trace gasdynamics and indirectly through changes in nutrient availability. We used throughfall exclusion shelters to determine effects of short‐term (3 month) drought on trace gas fluxes and nutrient availability in humid tropical forests in Puerto Rico. Exclusion and control plots were replicated within and across three topographic zones (ridge, slope, valley) to account for spatial heterogeneity typical of these ecosystems. Throughfall exclusion reduced soil moisture in all sites and lowered exchangeable phosphorus (P) on ridges and slopes. Drought decreased soil carbon dioxide (CO2) emissions by 30% in ridge sites and 28% in slope sites, and increased net methane (CH4) consumption by 480% in valley sites. Both valley and ridge sites became net nitrous oxide (N2O) sinks in response to soil drying. Emissions of CO2 and N2O, as well as CH4 consumption were positively related to exchangeable P and the nitrate:ammonium ratio. These findings suggest that drought has the potential to decrease net trace gas emissions from humid tropical forest soils. The differential response of trace gas emissions and nutrients from different topographic zones to drought underscores the complexity of biogeochemical cycling in these ecosystems and the importance of considering spatial heterogeneity when estimating whole system responses.

Soil cycling of trace gases in response to mesquite management in a semiarid grassland

Over the last century, proliferation of velvet mesquite ( Prosopis velutina) in Southwestern grasslands has led to mesquite removal to increase livestock forage, but the effects of mesquite on the fluxes of C- and N-based gases are not well understood. We report soil surface fluxes and porespace concentrations of carbon dioxide (CO 2), nitrous oxide (N 2O), and methane (CH 4) over two monsoon seasons beneath mesquite canopy (LIVE), in open grassland (OPEN), and under a mesquite skeleton (DEAD) in Southeastern Arizona. In 2003, CO 2 production was not different among sites, but on three 2004 measurement dates, CO 2 production was greatest from LIVE. In both years, N 2O production was highest in LIVE in early monsoon, while CH 4 production dominated in OPEN and DEAD sites. CH 4 consumption increased in all sites as the summer progressed, resulting in net monsoon CH 4 fluxes near zero. Over both years, temperature and precipitation accounted for significant variability in CO 2 flux and precipitation correlated with N 2O production. Soil moisture accounted for significant variability in CH 4 flux in 2003. Observed variations in trace gas dynamics suggest that several years of measurements would be required to accurately predict mesquite management effects on trace gas flux in Southwestern rangelands.

Diversity and Structure of Bacterial Chemolithotrophic Communities in Pine Forest and Agroecosystem Soils

Obligate lithotrophs (e.g., ammonia oxidizers) and facultative lithotrophs (e.g., CO and hydrogen oxidizers) collectively comprise a phylogenetically diverse functional group that contributes significantly to carbon and nitrogen cycles in soils and plays important roles in trace gas dynamics (e.g., carbon monoxide and nitrous and nitric oxides) that affect tropospheric chemistry and radiative forcing. In spite of their diverse physiologies, facultative and obligate lithotrophs typically possess the Calvin-Benson-Bassham cycle enzyme, ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisCO). In an effort designed to understand the structure of lithotrophic communities in soil, genomic DNA extracts from surface (0 to 2 cm) and subsurface (5 to 7 cm) soils have been obtained from two sites in a Georgia agroecosystem (peanut and cotton plots) and an unmanaged pine stand (>50 years old). The extracts have been used in PCR amplifications of the cbbL gene for the rubisCO large subunit protein. cbbL PCR products were cloned, sequenced, and subjected to phylogenetic and statistical analyses. Numerous novel lineages affiliated with the form IC clade (one of four form I rubisCO clades), which is typified by facultative lithotrophs, comprised lithotrophic communities from all soils. One of the form IC clone sequences clustered with a form IC clade of ammonia-oxidizing Nitrosospira. Distinct assemblages were obtained from each of the sites and from surface and subsurface soils. The results suggest that lithotrophic populations respond differentially to plant type and land use, perhaps forming characteristic associations. The paucity of clone sequences attributed to ammonia-oxidizing bacteria indicates that even though ammonia oxidation occurs in the various soils, the relevant populations are small compared to those of facultative lithotrophs.

Effects of Changes in Climate on Landscape and Regional Processes, and Feedbacks to the Climate System

Biological and physical processes in the Arctic system operate at various temporal and spatial scales to impact large-scale feedbacks and interactions with the earth system. There are four main potential feedback mechanisms between the impacts of climate change on the Arctic and the global climate system: albedo, greenhouse gas emissions or uptake by ecosystems, greenhouse gas emissions from methane hydrates, and increased freshwater fluxes that could affect the thermohaline circulation. All these feedbacks are controlled to some extent by changes in ecosystem distribution and character and particularly by large-scale movement of vegetation zones. Indications from a few, full annual measurements of CO2 fluxes are that currently the source areas exceed sink areas in geographical distribution. The little available information on CH4 sources indicates that emissions at the landscape level are of great importance for the total greenhouse balance of the circumpolar North. Energy and water balances of Arctic landscapes are also important feedback mechanisms in a changing climate. Increasing density and spatial expansion of vegetation will cause a lowering of the albedo and more energy to be absorbed on the ground. This effect is likely to exceed the negative feedback of increased C sequestration in greater primary productivity resulting from the displacements of areas of polar desert by tundra, and areas of tundra by forest. The degradation of permafrost has complex consequences for trace gas dynamics. In areas of discontinuous permafrost, warming, will lead to a complete loss of the permafrost. Depending on local hydrological conditions this may in turn lead to a wetting or drying of the environment with subsequent implications for greenhouse gas fluxes. Overall, the complex interactions between processes contributing to feedbacks, variability over time and space in these processes, and insufficient data have generated considerable uncertainties in estimating the net effects of climate change on terrestrial feedbacks to the climate system. This uncertainty applies to magnitude, and even direction of some of the feedbacks.

The flight experiment ANITA—a high performance air analyser for manned space cabins

Analysing Interferometer for Ambient Air (ANITA) is a flight experiment as precursor for a permanent continuous trace gas monitoring system on the International Space Station (ISS). For over 10 years, under various ESA contracts the flight experiment was defined, designed, breadboarded and set up. For the safety of the crew, ANITA can detect and quantify quasi on-line and simultaneously 32 trace gases with ppm or sub-ppm detection limits. The self-standing measurement system is based on Fourier Transform Infrared Spectrometer (FTIR) technology. The system represents a versatile air monitor allowing for the first time the detection and monitoring of trace gas dynamics of a spacecraft atmosphere. It is envisaged to accommodate ANITA in a Destiny (US LAB) Express Rack on the ISS. The transportation to the ISS is planned with the first ATV ‘Jules Verne’. The options are either the Space Shuttle or the Automated Transfer Vehicle.

Microbial community structure and global trace gases

AbstractGlobal change can affect soil processes by either altering the functioning of existing organisms or by restructuring the community, modifying the fundamental physiologies that drive biogeochemical processes. Thus, not only might process rates change, but the controls over them might also change. Moreover, previously insignificant processes could become important. These possibilities raise the question ‘Will changes in climate and land use restructure microbial communities in a way that will alter trace gas fluxes from an ecosystem?’ Process studies indicate that microbial community structure can influence trace gas dynamics at a large scale. For example, soil respiration and CH4 production both show ranges of temperature response among ecosystems, indicating differences in the microbial communities responsible. There are three patterns of NH4+ inhibition of CH4 oxidation at the ecosystem scale: no inhibition, immediate inhibition, and delayed inhibition; these are associated with different CH4 oxidizer communities. Thus, it is possible that changes in climate, land‐use, and disturbance regimes could alter microbial communities in ways that would substantially alter trace gas fluxes; we discuss the data supporting this conclusion. We also discuss approaches to developing research linking microbial community structure and activity to the structure and functioning of the whole ecosystem. Modern techniques allow us to identify active organisms even if they have not been cultivated; in combination with traditional experimental approaches we should be able to identify the linkages between these active populations and the processes they carry out at the ecosystem level. Finally, we describe scenarios of how global change could alter trace gas fluxes by altering microbial communities and how understanding the microbial community dynamics could improve our ability to predict future trace gas fluxes.

The status of fish populations and management of high mountain lakes in the western United States : P. Bahls, Northwest Science, 66(3), 1992, pp 183–193

Over the last century, proliferation of velvet mesquite (Prosopis velutina) in Southwestern grasslands has led to mesquite removal to increase livestock forage, but the effects of mesquite on the fluxes of C- and N-based gases are not well understood. We report soil surface fluxes and porespace concentrations of carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) over two monsoon seasons beneath mesquite canopy (LIVE), in open grassland (OPEN), and under a mesquite skeleton (DEAD) in Southeastern Arizona. In 2003, CO2 production was not different among sites, but on three 2004 measurement dates, CO2 production was greatest from LIVE. In both years, N2O production was highest in LIVE in early monsoon, while CH4 production dominated in OPEN and DEAD sites. CH4 consumption increased in all sites as the summer progressed, resulting in net monsoon CH4 fluxes near zero. Over both years, temperature and precipitation accounted for significant variability in CO2 flux and precipitation correlated with N2O production. Soil moisture accounted for significant variability in CH4 flux in 2003. Observed variations in trace gas dynamics suggest that several years of measurements would be required to accurately predict mesquite management effects on trace gas flux in Southwestern rangelands.