| 1. |
- Bastviken, David, et al.
(författare)
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Critical method needs in measuring greenhouse gas fluxes
- 2022
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Ingår i: Environmental Research Letters. - : IOP Publishing Ltd. - 1748-9326. ; 17:10
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Tidskriftsartikel (refereegranskat)abstract
- Reaching climate goals depends on appropriate and accurate methods to quantify greenhouse gas (GHG) fluxes and to verify that efforts to mitigate GHG emissions are effective. We here highlight critical advantages, limitations, and needs regarding GHG flux measurement methods, identified from an analysis of >13 500 scientific publications regarding three long-lived GHGs, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). While existing methods are well-suited for assessing atmospheric changes and local fluxes, they are expensive and have limited accessibility. Further, we are typically forced to choose between methods for very local GHG sources and sinks and their regulation (m(2)-scaled measurements), or methods for aggregated net fluxes at >ha or km(2) scales measurements. The results highlight the key need of accessible and affordable GHG flux measurement methods for the many flux types not quantifiable from fossil fuel use, to better verify inventories and mitigation efforts for transparency and accountability under the Paris agreement. The situation also calls for novel methods, capable of quantifying large scale GHG flux patterns while simultaneously distinguishing local source and sink dynamics and reveal flux regulation, representing key knowledge for quantitative GHG flux modeling. Possible strategies to address the identified GHG flux measurement method needs are discussed. The analysis also generated indications of how GHG flux measurements have been distributed geographically and across flux types, which are reported.
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| 2. |
- Bastviken, David, et al.
(författare)
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Determination of the piston velocity for water-air interfaces using flux chambers, acoustic Doppler velocimetry, and IR imaging of the water surface
- 2013
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Ingår i: Journal of Geophysical Research - Biogeosciences. - : American Geophysical Union (AGU). - 0148-0227 .- 2156-2202 .- 2169-8953. ; 118:2, s. 770-782
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Tidskriftsartikel (refereegranskat)abstract
- The transport of gasses dissolved in surface waters across the water-atmosphere interface is controlled by the piston velocity (k). This coefficient has large implications for, e.g., greenhouse gas fluxes but is challenging to quantify in situ. At present, empirical k-wind speed relationships from a small number of studies and systems are often extrapolated without knowledge of model performance. This study compares empirical k estimates from flux chamber and surface water gas concentration measurements (chamber method), eddy cell modeling and dissipation rates of turbulent kinetic energy (dissipation method), and a surface divergence method based on IR imaging, at a fetch limited coastal observation station. We highlight strengths and weaknesses of the methods, and relate measured k values to parameters such as wave height, and surface skin velocities. The chamber and dissipation methods yielded k values in the same order of magnitude over a 24h period with varying wind conditions (up to 10ms−1, closest weather station) and wave heights (0.01–0.30m). The surface divergence method most likely did not resolve the small turbulent eddies that cause the main divergence. Flux chamber estimates showed the largest temporal variability, with lower k values than the dissipation method during calm conditions, where the dissipation method failed as waves and instrument noise dominated over the turbulence signal. There was a strong correspondence between k from chambers, the RMS of surface velocities from IR imaging, and wave height. We propose a method to estimate area integrated values of k from wave measurements.
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| 3. |
- Bastviken, David, Professor, 1971-, et al.
(författare)
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Measuring greenhouse gas fluxes : what methods do we have versus what methods do we need?
- 2022
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Appropriate methods to measure greenhouse gas (GHG) fluxes are critical for our ability to detect fluxes, understand regulation, make adequate priorities for climate change mitigation efforts, and verify that these efforts are effective. Ideally, we need reliable, accessible, and affordable measurements at relevant scales. We surveyed present GHG flux measurement methods, identified from an analysis of >11000 scientific publications and a questionnaire to sector professionals and analysed method pros and cons versus needs for novel methodology. While existing methods are well-suited for addressing certain questions, this presentation presents fundamental limitations relative to GHG flux measurement needs for verifiable and transparent action to mitigate many types of emissions. Cost and non-academic accessibility are key aspects, along with fundamental measurement performance. These method limitations contribute to the difficulties in verifying GHG mitigation efforts for transparency and accountability under the Paris agreement. Resolving this mismatch between method capacity and societal needs is urgently needed for effective climate mitigation. This type of methodological mismatch is common but seems to get high priority in other knowledge domains. The obvious need to prioritize development of accurate diagnosis methods for effective treatments in healthcare is one example. This presentation provides guidance regarding the need to prioritize the development of novel GHG flux measurement methods.
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| 4. |
- Bastviken, David, et al.
(författare)
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Synergies among the transport sector and environmental sensing in designing environmental monitoring systems for the future
- 2024
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Ingår i: Sammanställning av referat från Transportforum 2024. - Linköping : Statens väg- och transportforskningsinstitut. ; , s. 450-450
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Air pollutants, greenhouse gas emissions, and noise are affecting people worldwide. Therefore, all sectors of societies, including the transport sector, are developing capacity to reduce their contributions to these pollutants. This generates a demand for transforming environmental monitoring of air pollutants, greenhouse gases, and noise from scarcely located measurements used to investigate long-term trends in retrospect, towards frequent and abundant real-time tools that allows for planning and optimization of activities to minimize the emissions. While the transport sector generates considerable emissions and is often portrayed as a problem, this presentation explores paths towards environmental monitoring for the future along which the transport sector can instead contribute important solutions. The methodological paths presented will briefly touch on (1) the use of low-cost sensing around e.g., airports, and (2) UAV systems for trace gas mapping. Opportunities and challenges will be explored based on recent research experiences. Multiple aspects, ranging from hardware details to large system use, are of interest and will be discussed. Results from recent research on using low-cost sensors for carbon dioxide and methane, and novel multi-gas UAV mapping will be shown, and progress and remaining challenges will be discussed. While challenges remain, it is increasingly clear that deeper integration of environmental sensing and the transport sector would be highly beneficial for the development and implementation of future environmental monitoring that can empower and support societal action to minimize pollutant and greenhouse gas emissions. Such integration will require multidimensional thinking, combining transport sector and environmental sensing expertise for maximum positive impact.
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| 5. |
- Bastviken, David, et al.
(författare)
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Technical Note: Cost-efficient approaches to measure carbon dioxide (CO2) fluxes and concentrations in terrestrial and aquatic environments using mini loggers
- 2015
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Ingår i: Biogeosciences. - : European Geosciences Union (EGU) / Copernicus Publications. - 1726-4170 .- 1726-4189. ; 12:12, s. 3849-3859
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Tidskriftsartikel (refereegranskat)abstract
- Fluxes of CO2 are important for our understanding of the global carbon cycle and greenhouse gas balances. Several significant CO2 fluxes in nature may still be unknown as illustrated by recent findings of high CO2 emissions from aquatic environments, previously not recognized in global carbon balances. Therefore, it is important to develop convenient and affordable ways to measure CO2 in many types of environments. At present, direct measurements of CO2 fluxes from soil or water, or CO2 concentrations in surface water, are typically labor intensive or require costly equipment. We here present an approach with measurement units based on small inexpensive CO2 loggers, originally made for indoor air quality monitoring, that were tested and adapted for field use. Measurements of soil-atmosphere and lake-atmosphere fluxes, as well as of spatiotemporal dynamics of water CO2 concentrations (expressed as the equivalent partial pressure, pCO(2aq)) in lakes and a stream network are provided as examples. Results from all these examples indicate that this approach can provide a cost- and labor-efficient alternative for direct measurements and monitoring of CO2 flux and pCO(2aq) in terrestrial and aquatic environments.
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| 6. |
- Bastviken, David, et al.
(författare)
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The importance of plants for methane emission at the ecosystem scale
- 2023
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Ingår i: Aquatic Botany. - : ELSEVIER. - 0304-3770 .- 1879-1522. ; 184
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Tidskriftsartikel (refereegranskat)abstract
- Methane (CH4), one of the key long-lived atmospheric greenhouse gases, is primarily produced from organic matter. Accordingly, net primary production of organic matter sets the boundaries for CH4 emissions. Plants, being dominant primary producers, are thereby indirectly sustaining most global CH4 emissions, albeit with delays in time and with spatial offsets between plant primary production and subsequent CH4 emission. In addition, plant communities can enhance or hamper ecosystem production, oxidation, and transport of CH4 in multiple ways, e.g., by shaping carbon, nutrient, and redox gradients, and by representing a physical link be-tween zones with extensive CH4 production in anoxic sediments or soils and the atmosphere. This review focuses on how plants and other primary producers influence CH4 emissions with the consequences at ecosystem scales. We outline mechanisms of interactions and discuss flux regulation, quantification, and knowledge gaps across multiple ecosystem examples. Some recently proposed plant-related ecosystem CH4 fluxes are difficult to reconcile with the global atmospheric CH4 budget and the enigmas related to these fluxes are highlighted. Overall, ecosystem CH4 emissions are strongly linked to primary producer communities, directly or indirectly, and properly quantifying magnitudes and regulation of these links are key to predicting future CH4 emissions in a rapidly changing world.
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| 7. |
- Djupvik, A. A., et al.
(författare)
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A multi-wavelength census of star formation activity in the young embedded cluster around Serpens/G3-G6
- 2006
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 458:3, s. 789-803
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Tidskriftsartikel (refereegranskat)abstract
- Aims.The aim of this paper is to characterise the star formation activity in the poorly studied embedded cluster Serpens/G3-G6, located ~45 arcmin (3 pc) to the south of the Serpens Cloud Core, and to determine the luminosity and mass functions of its population of Young Stellar Objects (YSOs).Methods: .Multi-wavelength broadband photometry was obtained to sample the near and mid-IR spectral energy distributions to separate YSOs from field stars and classify the YSO evolutionary stage. ISOCAM mapping in the two filters LW2 (5-8.5 μm) and LW3 (12-18 μm) of a 19 arcmin × 16 arcmin field was combined with JHKS data from 2MASS, KS data from Arnica/NOT, and L arcmin data from SIRCA/NOT. Continuum emission at 1.3 mm (IRAM) and 3.6 cm (VLA) was mapped to study the cloud structure and the coldest/youngest sources. Deep narrow band imaging at the 2.12 μm S(1) line of H2 from NOTCam/NOT was obtained to search for signs of bipolar outflows.Results: .We have strong evidence for a stellar population of 31 Class II sources, 5 flat-spectrum sources, 5 Class I sources, and two Class 0 sources. Our method does not sample the Class III sources. The cloud is composed of two main dense clumps aligned along a ridge over ~0.5 pc plus a starless core coinciding with absorption features seen in the ISOCAM maps. We find two S-shaped bipolar collimated flows embedded in the NE clump, and propose the two driving sources to be a Class 0 candidate (MMS3) and a double Class I (MMS2). For the Class II population we find a best age of ~2 Myr and compatibility with recent Initial Mass Functions (IMFs) by comparing the observed Class II luminosity function (LF), which is complete to 0.08 Lȯ, to various model LFs with different star formation scenarios and input IMFs.
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| 8. |
- Gålfalk, Magnus, et al.
(författare)
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A detailed study of the L1641N star formation region
- 2008
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 489:3, s. 1409-1439
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Tidskriftsartikel (refereegranskat)abstract
- Aims. We search for young stellar objects (YSOs) in the L1641N cluster and characterize the star formation activity through determination of the age distribution, mass function, spatial distribution, and the star formation history.Methods. Multi-wavelength broad band photometry both from space and the ground are used to look for IR excess in order to separate field stars from YSOs and to sample the spectral energy distributions. Space-based observations were obtained using the ISO satellite (ISOCAM) in two filters, centred at 6.7 and 14.3 m, and Spitzer (IRAC) at 3.6, 4.5, 5.8, and 8.0 m. Our ground-based observations were made with the Nordic Optical Telescope (NOT) using ALFOSC (I band), NOTCam (J, and 2.12 m H2), and SIRCA (L'). More than 50 of the brightest I-band sources were then studied with follow-up optical spectroscopy (5780-8340 Å) to check for signs of accretion (H in emission) and youth (Li I in absorption) and to determine their effective temperatures. By comparing theoretical evolution tracks with our YSO sample in the H-R diagram, we calculated an age, luminosity, and mass distribution.Results. We detect a total of 216 (Spitzer or I band) sources in L1641N, 89 of which are YSO candidates. Most of the spectra are of M-type with H strongly in emission, and many have Li 6707 in absorption. The four brightest I band sources (F and G stars) are suggested as foreground stars, and the L1641N IRAS source is shown to be the combined flux of at least four sources. We find that the interstellar extinction is well-fit in the optical and near-IR by a power law with an exponent of 1.58, although in the mid-IR the Spitzer observations show a higher extinction than expected from theory. The median age of the YSO sample is ~1 Myr and the resulting MF has a flat distribution for low masses down to the completeness limit. There is evidence of a constant star formation rate of one star in 3.7 104 yr during the past few Myr. We find 11 sources older than 10 Myr and a spatial separation between younger and older YSOs, suggesting that many of the older stars formed in L1641N could have left the cluster, giving the appearance of an increased star formation rate with time.
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| 9. |
- Gålfalk, Magnus, et al.
(författare)
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Approaches for hyperspectral remote flux quantification andvisualization of GHGs in the environment
- 2017
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Ingår i: Remote Sensing of Environment. - : Elsevier. - 0034-4257 .- 1879-0704. ; 191, s. 81-94
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Tidskriftsartikel (refereegranskat)abstract
- Methane (CH4) and nitrous oxide (N2O) are two very potent greenhouse gases, with highly heterogeneous distributionsin both space and time. Mapping hot-spots and source areas, and measuring fluxes in different environmentshas so far not been possible on a local scale using direct measurements. We have developed amethod for simultaneous mapping of methane (CH4) and nitrous oxide (N2O), also including water vapor(H2O), using ground-based remote sensing on a landscape-sized scale by utilizing Imaging Fourier TransformSpectrometers (IFTS) with high spectral resolution and imaging rates. The approach uses calculated libraries oftransmission spectra at the spectroscopic resolutions of the IFTS, based on the HITRAN database of spectroscopiclines and our own line-by-line radiative transfer model (LBLRTM). For each species, 1024 spectra have beenmade, resulting in 10243 combinations of column densities. Using an adaptive grid, solutions are found foreach line of sight at a spectral resolution of up to 0.25 cm−1 using the full spectral region of the detector. Themodeling ismulti-layered, calculating temperatures of the background, air, and any additional gas layers, also accountingfor reflected cold sky. Background distances can bemapped fromthe amount of water vapor in each lineof sight. The described approach can be used to identify sources, quantify gas distributions, and to calculate fluxes.Visualizations can produce gas distribution images, as well as air motion videos, which are used to map fluxesusing the same data set, without the need for additional instruments for wind measurements.
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| 10. |
- Gålfalk, Magnus, et al.
(författare)
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Ground-based remote sensing of CH4 and N2O fluxes from a wastewater treatment plant and nearby biogas production with discoveries of unexpected sources
- 2022
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Ingår i: Environmental Research. - : Academic Press Inc - Elsevier Science. - 0013-9351 .- 1096-0953. ; 204
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Tidskriftsartikel (refereegranskat)abstract
- This study is an attempt to assess CH4 and N2O emissions from all the treatment steps of a wastewater treatment plant (WWTP) in Sweden, serving 145 000 persons, and an adjacent biogas production facility. We have used novel mid-IR ground-based remote sensing with a hyperspectral camera to visualize and quantify the emissions on 21 days during a year, with resulting yearly fluxes of 90.4 +/- 4.3 tonne CH4/yr and 10.9 +/- 1.3 tonne N2O/yr for the entire plant. The most highly emitting CH4 source was found to be sludge storage, which is seldom included in literature as in-situ methods are not suitable for measuring emissions extended over large surfaces, still contributing 90 % to the total CH4 emission in our case. The dominating N2O source was found to be a Stable High rate Ammonia Removal Over Nitrite reactor, contributing 89 % to the total N2O emissions. We also discovered several unexpected CH4 sources. Incomplete flaring of CH4 gave fluxes of at least 30 kg CH4/min, corresponding to plume concentrations of 2.5 %. Such highly episodic fluxes could double the plant-wide yearly emissions if they occur 2 days per year. From a distance of 250 m we found a leak in the biogas production facility, corresponding to 1.1 % of the CH4 produced, and that loading of organic material onto trucks from a biofertilizer storage tank contributed with high emissions during loading events. These results indicate that WWTP emissions globally may have been grossly underestimated and that it is essential to have effective methods that can measure all types of fluxes, and discover new potential sources, in order to make adequate priorities and to take effective actions to mitigate greenhouse gas emissions from WWTPs.
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