Purpose
Much progress has recently been made in modelling future background systems for LCA by including future scenario data, e.g. from Integrated Assessment Models (IAMs), into life cycle inventory ...(LCI) databases. A key problem is, however, that this yields potentially dozens of scenario LCI databases (i.e. LCI databases that represent different scenarios and reference years), instead of a single background database, which is very impractical for LCA modelling purposes. This paper proposes an approach to overcome this problem.
Methods
The approach consists of transforming all scenario LCI databases into a single superstructure database and an associated scenario difference file. The superstructure database is also a regular LCI database, but is constructed to contain all unique exchanges (elementary and intermediate flows) and processes that exist across all scenario LCI databases. The scenario difference file stores the differences between all scenarios and can be used to turn the superstructure into a specific scenario LCI database. This is very fast as it can be done in memory during LCA calculations.
Results and discussion
A key advantage of the superstructure approach is that a single LCI database can be used to represent different background systems. Therefore, the practitioner does not need to re-link a foreground system to multiple LCI databases, which is work-intensive and invites modelling errors. LCA results for all scenarios and reference years can be calculated automatically. We also illustrate how the superstructure approach has been implemented in the Activity Browser open source LCA software. Although this paper introduces the superstructure approach for background scenarios, it can also be used to model foreground scenarios, and even, as implemented in the Activity Browser, combinations of background and foreground scenarios. Finally, we briefly discuss further challenges that need to be addressed for a more widespread use of background scenarios in LCA.
Conclusions
The superstructure approach presents a practical solution for making the use of future background scenarios more wide-spread and, therefore, to overcome the problem of performing prospective LCA with temporally inconsistent foreground and background systems. The implementation in the Activity Browser makes the approach available for anyone and may serve as inspiration for other LCA software to implement the superstructure approach or a similar concept. While this may be an important technical milestone, additional coordination between data providers, scenario generators, LCA practitioners, and software developers will be required to further facilitate the use of background scenarios in prospective LCA studies.
In a natural analog study of risks associated with carbon sequestration, impacts of CO
2
on shallow groundwater quality have been measured in a sandstone aquifer in New Mexico, USA. Despite ...relatively high levels of dissolved CO
2
, originating from depth and producing geysering at one well, pH depression and consequent trace element mobility are relatively minor effects due to the buffering capacity of the aquifer. However, local contamination due to influx of brackish waters in a subset of wells is significant. Geochemical modeling of major ion concentrations suggests that high alkalinity and carbonate mineral dissolution buffers pH changes due to CO
2
influx. Analysis of trends in dissolved trace elements, chloride, and CO
2
reveal no evidence of in situ trace element mobilization. There is clear evidence, however, that As, U, and Pb are locally co-transported into the aquifer with CO
2
-rich brackish water. This study illustrates the role that local geochemical conditions will play in determining the effectiveness of monitoring strategies for CO
2
leakage. For example, if buffering is significant, pH monitoring may not effectively detect CO
2
leakage. This study also highlights potential complications that CO
2
carrier fluids, such as brackish waters, pose in monitoring impacts of geologic sequestration.
Extension orientation is a key parameter in rift tectonics. While a clockwise rotation of the extension orientation is widely accepted for the southern Rio Grande rift and the Basin and Range ...province in the western U.S., in which direction(s) the northern Rio Grande rift opened has been controversial. Moreover, slip re-orientation, a phenomenon caused by local stress rotation on weak faults under a uni-directional regional extension, imposes a serious impact on kinematic interpretations. We investigate the presently oblique Tusas-Abiquiu segment of the Rio Grande rift in north-central New Mexico to assess the rifting kinematics with the presence of pre-existing crustal weaknesses. Fault-slip data show an overall NE-SW extension on the NW-trending Tusas border faults, and WNW-ESE extension on the NNE-trending Abiquiu border and internal faults. The slip vectors on the border faults show a wide variety of oblique-slip component, whereas those on the internal faults are predominantly pure dip-slip. The majority of our field measurements can be reproduced by the slip re-orientation model, although this model's setting does not satisfy regional geological records. Clockwise rotation of the extension axes from NE-SW to WNW-ESE can also explain our fault-slip data, as well as other structures in the rift. Tectonic reactivation during the extension also influenced the landscape evolution of the early rift. The Rio Grande rift shared similar extension orientation with the southern Basin and Range during the late Oligocene. The extensional strain field of the southwestern North American plate shows a progressive, time-transgressive rotational pattern, implying that plate boundary processes, instead of asthenospheric upwelling, governed the initiation and early evolution of this intracontinental rift.
•Kinematics of early, oblique rifting is studied for the northern Rio Grande rift.•Rift border and internal faults record complex, heterogeneous fault-slip vectors.•Uni-directional extension by slip re-orientation can reproduce most fault-slips.•Clockwise rotation of extension direction from SW to WNW explains more observations.•Plate boundary processes drove the rift initiation and early evolution.
The Activity Browser is an open source software for advanced Life Cycle Assessment (LCA). The Activity Browser provides a graphical user interface (GUI) to the brightway LCA framework and makes ...common tasks such as managing projects and databases, modeling life cycle inventories, and analyzing LCA results easier and more intuitive. In addition, it provides advanced features for LCA modeling and data analyses and thus facilitates state-of-the-art LCA research. It can be extended to implement novel LCA modeling approaches and analyses as needed.
•The Activity Browser is an open source software for Life Cycle Assessment (LCA).•It builds upon and constitutes a productivity tool for the brightway framework.•It permits LCA parametrization, scenario modeling, graph exploration, and other advanced features.•It is an extendable software tool that can be tailored to the specific needs of LCA practitioners or research projects.
In a natural analog study of risks associated with carbon sequestration, impacts of CO sub(2) on shallow groundwater quality have been measured in a sandstone aquifer in New Mexico, USA. Despite ...relatively high levels of dissolved CO sub(2), originating from depth and producing geysering at one well, pH depression and consequent trace element mobility are relatively minor effects due to the buffering capacity of the aquifer. However, local contamination due to influx of brackish waters in a subset of wells is significant. Geochemical modeling of major ion concentrations suggests that high alkalinity and carbonate mineral dissolution buffers pH changes due to CO sub(2) influx. Analysis of trends in dissolved trace elements, chloride, and CO sub(2) reveal no evidence of in situ trace element mobilization. There is clear evidence, however, that As, U, and Pb are locally co-transported into the aquifer with CO sub(2)-rich brackish water. This study illustrates the role that local geochemical conditions will play in determining the effectiveness of monitoring strategies for CO sub(2) leakage. For example, if buffering is significant, pH monitoring may not effectively detect CO sub(2) leakage. This study also highlights potential complications that CO sub(2) carrier fluids, such as brackish waters, pose in monitoring impacts of geologic sequestration.
We use tectonic subsidence patterns from wells and stratigraphic sections to describe the mid-Miocene to present tectonic subsidence history of the Rio Grande rift. Tectonic subsidence and therefore ...rift opening were quite fast until ca. 8 Ma, with net subsidence rates (∼25-65 mm/k.y.) comparable to those of the prerupture phase of rifted continental margins. The rapid subsidence was followed by a late Miocene-early Pliocene unconformity that developed mainly along the flanks of most rift basins. The age of its associated lacuna is spatially variable but falls within 8-3 Ma (mostly 7-5 Ma) and thus is synchronous with eastward tilting of the western Great Plains (ca. 6-4 Ma). Tectonic subsidence rates either remained similar or decreased after the Miocene-Pliocene unconformity. North of 35°N, our analysis of geoid-to-elevation ratios suggests that, at present, topography of the Rio Grande rift region is compensated by a component of mantle-driven dynamic uplift. Previous work has indicated that this dynamic uplift is caused by focused vertical flow in the upper mantle resulting from slab descent and fragmentation of the Farallon slab, and Rio Grande rift opening, which affected the Rio Grande rift area beginning in the late Miocene. The spatial distribution and timing of the unconformity, as well as eastward tilting of the western Great Plains, can be explained by this dynamic mantle uplift, with contributions from variations in rift opening tectonics and climate. The focused mantle upwelling is not associated with increased rift opening rates.
Glucagon-like peptide 1 (GLP-1) mimetics are effective drugs for treatment of type 2 diabetes, and there is consequently extensive interest in increasing endogenous GLP-1 secretion and L-cell ...abundance. Here we identify G-protein-coupled bile acid receptor 1 (GPBAR1) as a selective regulator of intestinal L-cell differentiation. Lithocholic acid and the synthetic GPBAR1 agonist, L3740, selectively increased L-cell density in mouse and human intestinal organoids and elevated GLP-1 secretory capacity. L3740 induced expression of
and transcription factors
and
L3740 also increased the L-cell number and GLP-1 levels and improved glucose tolerance in vivo. Further mechanistic examination revealed that the effect of L3740 on L cells required intact GLP-1 receptor and serotonin 5-hydroxytryptamine receptor 4 (5-HT4) signaling. Importantly, serotonin signaling through 5-HT4 mimicked the effects of L3740, acting downstream of GLP-1. Thus, GPBAR1 agonists and other powerful GLP-1 secretagogues facilitate L-cell differentiation through a paracrine GLP-1-dependent and serotonin-mediated mechanism.
Genetic studies promise to provide insight into the molecular mechanisms underlying type 2 diabetes (T2D). Variants associated with T2D are often located in tissue-specific enhancer clusters or ...super-enhancers. So far, such domains have been defined through clustering of enhancers in linear genome maps rather than in three-dimensional (3D) space. Furthermore, their target genes are often unknown. We have created promoter capture Hi-C maps in human pancreatic islets. This linked diabetes-associated enhancers to their target genes, often located hundreds of kilobases away. It also revealed >1,300 groups of islet enhancers, super-enhancers and active promoters that form 3D hubs, some of which show coordinated glucose-dependent activity. We demonstrate that genetic variation in hubs impacts insulin secretion heritability, and show that hub annotations can be used for polygenic scores that predict T2D risk driven by islet regulatory variants. Human islet 3D chromatin architecture, therefore, provides a framework for interpretation of T2D genome-wide association study (GWAS) signals.
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