bluuebunny/crossref_metadata_2025 huggingface dataset:
Paleoarchean crustal evolution of the Singhbhum Craton, eastern India: Insights from granitoid petrology and zircon U-Pb and Lu-Hf systematics
Authors: Mitra Aniruddha , Dey Sukanta , Zong Keqing , Liu Yongsheng , Mitra Anirban
Published: March 2020

Singhbhum Craton, eastern India, exposes some of the oldest known composite Paleoarchean granitoids. These granitoids range from sodic TTGs to evolved, potassic granites.  The whole process of their formation, starting from nucleation of a juvenile continent to its evolution and final stabilization is documented. The central part of the craton started nucleating with the formation of 3.45–3.40Ga juvenile (zircon εHft=+0.6 to +7.1) TTGs. These TTGs characterized by slightly depleted HREE and Y, negligible Eu-anomaly (Eu/Eu*=0.90 to 1.00) and moderate Sr/Y (25–64), consistent with derivation from a low-K mafic crust at a pressure near the lower end of the garnet stability field, causing subordinate garnet retention in the residue and negligible role of plagioclase. During 3.32Ga, deeper melting of a juvenile mafic crust (zircon εHft=+1.3 to +5.7) caused emplacement of a second generation of TTG. Deeper melting is suggested by depleted HREE and Y, and high Sr/Y (52–155), implying significant amount of residual garnet retention. Subsequently at 3.28 and 3.25Ga, melting of moderately old to juvenile (zircon εHft=-1.9 to +4.5), mostly TTG sources at variable depths generated potassic, LILE-enriched, high-silica granites. Intrusion of these potassic granites resulted in a stable and buoyant crust that marked the final Cratonization of the Singhbhum Craton. The sequence of events is interpreted in terms of repeated intracrustal melting and granitoid generation in a gradually thickening oceanic plateau with a progressive change in granitoid source from mafic to felsic in composition. Combination of rock assemblage, regional geology, and structural pattern also supports intraplate nature of the magmatism in Singhbhum Craton, which might have been a significant mechanism of crustal growth worldwide during Paleoarchean.
Representing fault evolution by animating a drone 3D model with computer game software (Boconó Fault, Venezuelan Andes).
Authors: Rocca Riccardo
Published: March 2020

This presentation describes a workflow to enhance the 3D model of a geological outcrop cut across by a regional strike-slip fault located in the Venezuelan Andes.

This fault (Boconó Fault) has been active since the Early Holocene time and has affected the landscape by displacing the rivers course and the geometry of ancient glacial moraines.

One of these moraines (Los Zerpa) was studied in detail in 1983 by geologist C. Schubert, who described its evolution with a series of hand drawn panels.

In 2015 the same area was acquired by the author with a drone survey and rendered as a digital 3D model. More recently the same model has been improved by adding also the interpretation made in the 80’s, adapted to 3D in the form of geometrical elements (lineaments and surfaces) and animations showing the different stages of evolution.

The fault model can now be publicly accessed over the internet and the users can observe and animate its evolution in 3D and understand the geological processes more intuitively (https://riccardorocca.github.io/home/Los_Zerpa.html).

This result has been achieved by editing the original model with free software which is more typically used for computer games, namely "Blender" (a 3D editor) and "Sketchfab" (a publishing platform for 3D models). Furthermore, the “Sketchfab” display can be programmed in Javascript, adding widgets that allow the users to interact with the scene by hiding/showing/moving specific elements of the model.

This workflow is proposed as an example that can be applied to other 3D models of geological faults and other geological features, so that the geological concepts can be represented more intuitively and made accessible to a large audience. With these improvements the models would be a more valuable support to, for instance, published papers and virtual field-trips.
Co-creation processes of nature based solutions in hydrological modelling – case studies in the UK, Belgium and the Netherlands
Authors: Bogatinoska Borjana , Lansu Angelique , Floor Judith , Huitema Dave , Dekker Stefan
Published: March 2020

Climate adaptation of brook catchments is much needed in the studied regions of England, Belgium and the Netherlands. With the continuous rise of global temperatures and global change, these regions suffer from the impacts of extreme weather events such as drought and flooding. Extreme weather and climate change impacts are spatially non-uniform, uncertain and can have different strengths at local and regional level. Therefore, cities and regions need to adapt to climate change in an ambiguous way. Accordingly, there is no uniformity in the adaptive capacity of individuals, groups within society, organisations and governments or how they can respond to current and future climate change impacts.

To better understand the interlinkages in nature-based climate adaptation between the socio-economic and climate change drivers, we studied these drivers in the hydrological modelling in 3 pilot studies in the UK, the Netherlands and Belgium. Focus is on how co-creation, defined as active participation is incorporated in the hydrological modelling process, (1) within each brook catchment and (2) between the professionals, as cross border knowledge transfer. Data on the co-creation process was collected with workshops on each of the semi-annual partner meetings of each catchment. Data on the modelling process was collected by semi-structured interviews of the professionals and by using assessment of professional learning in the network (field trips). Findings on co-creation processes of nature based solutions in hydrological modelling will be compared in the UK, the Netherlands and Belgium. In the end, existing co-creation processes will be joined to a framework for co-creation which can be improved and adapted based on the gathered data. This would include: identification of stakeholder groups and their needs, the level of intended participation, the identified climate problem by the stakeholders and by the policy-makers, the planned modelling approach, the NbS etc.

Keywords: climate change, hydrology, nature-based solutions, stakeholders, climate adaptation, framework.
"Bare soil" detection addressing agricultural production optimization throughout the year: case study in Emilia Romagna using Sentinel-2 images.
Authors: Greggio Nicolas , Cimatti Martina , Spisni Andrea , Sapia Luca Domenico , Baraldi Andrea , Contin Andrea , Marazza Diego
Published: March 2020

Changes in soil practices and management policies are fundamental in order to satisfy future growing food and energy demand, limiting risks of soil depletion. To this purpose remote sensed data are proving crucial for precision farming and for soil characterization and monitoring. In regions where agronomic rotations are adopted, soils experience unproductive periods between two main crops ("bare soil"), causing nutrient leaching, erosion and acceleration of organic matter consumption. Although the presence of "bare soil" period is evident and well known, there are no studies able to provide a dedicated regional framework to draw attention to this issue.

This study aims at mapping soils cultivated but unproductive during certain times of the year ("bare soil") using satellite images. Once detected, "bare soils" are deeply investigated to define their surface and the time duration of the bare soil status. Thereafter, valorization scenarios for these "bare soil" are proposed considering an optimized mix of energy and cover crops.

The applied methodology includes Sentinel-2, 5-days-return-time optical images, with 20 m ground spatial resolution acquired during 2017. The images were pre-processed using the Satellite Image Automatic Mapper™ (SIAM™) and outputs subsequently processed on the QGIS platform and validated with ground truths provided by the regional agriculture authority.

Of the total Utilised Agricultural Area (UAA), results show that up to 20% is "bare soil" from July to October and about 10% is unproductive from November to April. The size of most plots varies from 0.5-2 ha, however, about 30% of the "bare soil" fields have surface size from 3 to 50 ha, sufficient to justify their agronomic exploitation. In a basic scenario where biomass sorghum is cultivated from July to October, 50% of the bioenergy demand can be met through anaerobic digestion.

This study proposes a digital soil mapping methodology able to answer several questions: if yields can be improved, in what period of the year, in which area, how large are the plots. Therefore, the potential of "bare soils" for increasing food or energy crops and to store more carbon in soils is highlighted.
Climate change or irrigated agriculture – what drives the water level decline of Lake Urmia?
Authors: Schulz Stephan , Darehshouri Sahand , Hassanzadeh Elmira , Schüth Christoph
Published: March 2020

Lake Urmia is one of the largest hypersaline lakes on earth with a unique biodiversity. Over the past two decades the lake water level declined dramatically, threatening the functionality of the lake’s ecosystems. There is a controversial debate about the reasons for this decline, with either mismanagement of the water resources, or climatic changes assumed to be the main cause.

During this study we gathered an extensive hydro-meteorological data set, information about the reservoirs and the lake bathymetry. This data served for a quantification of the water budget components of Lake Urmia over the last five decades. Interestingly, a comparison of the temporal patterns of the principal natural boundary conditions of streamflow (precipitation and evaporation) with the inflow to the lake revealed that the variability of the inflow can be well explained its natural drivers. With this we can show that variations of Lake Urmia’s water level during the analyzed period were mainly triggered by climatic changes.

However, under the current climatic conditions agricultural water extraction volumes are significant and often exceed the remaining surface water inflow volumes. This rather simple observation shows that something deeper needs to be dug here. Therefore, we performed a parsimonious hindcast experiment and run a set of development scenarios based on the previously developed water balance. This helped us to better quantify the human impact on the development of the water volume of Lake Urmia. We could show that changes in agricultural water withdrawal would have a significant impact on the lake volume and could either stabilize the lake, or lead to its complete collapse (Schulz et al., 2020).

 

References

Schulz, S., Darehshouri, S., Hassanzadeh, E., Tajrishy, M. and Schüth, C.: Climate change or irrigated agriculture – what drives the water level decline of Lake Urmia, Sci. Rep., 10(1), 236, doi:10.1038/s41598-019-57150-y, 2020.
Hydrological response to land use scenarios under climate change. Adaptation measures for an agricultural basin: Rapel river basin in central Chile.
Authors: González Molina María José , Vargas Mesa Haydee Ximena , Vásquez Placencia Nicolás
Published: March 2020

Faced to reduced future water availability, associated with climate change variability and population growth, it becomes important to study the hydrological response under various modifications of crop patterns currently present in an agricultural basin in Chile. The focus of this research is to improve the future water resources management knowing the behavior of the hydrological cycle under meteorological forcings during the historical period 1985 to 2015.

We selected the Rapel River basin, in Central Chile, with a relevant agricultural activity and high water consumption in the study area.

VIC (Variable Infiltration Capacity) hydrological model, was calibrated considering base land use and historical records determined with the product CR2Met (www.cr2.cl/datos-productos-grillados/) for a grid with cells of 5 km by 5 km. For the near future (2030-2060) we proposed agricultural land use scenarios, considering a set of 40 crops that are representative of the area. The variation of the future forcings was considered according to the climate change scenario RCP 8.5 for four Global Climate Models (CCSM4, CSIRO, IPSAL, and MIROC).

Results show the variation in evapotranspiration demand and runoff, according to crop class and geographical ubication. An important variation of both flows is revealed, which is mainly related to the class of crop.  For this reason, the selection of crops determines a specific hydrological response, so the study of the change in land use is crucial. Based on the hydrologic response of each class of crop over the basin,  crop arrays were obtained and patterns are recommended for future scenarios. The arrays consider the optimal location of the crop, which reduces evapotranspiration demand and increases runoff. Also, changes in the percentage of the cultivated area of each crop class are recommended.
Better constraining the CO2 plant uptake at global scale: joint assimilation of COS and CO2 atmospheric measurements into a transport model.
Authors: Remaud Marine , Chevallier Frédéric , Peylin Philippe , Berchet Antoine , Maignan Fabienne
Published: March 2020

Inverse systems that assimilate atmospheric carbon dioxide measurements (CO2) into a global atmospheric transport model, are commonly used together with anthropogenic emission inventories to infer net biospheric surface fluxes. However, when assimilating CO2 measurements only, the respiration fluxes cannot be disentangled from the gross primary production (GPP) fluxes, leaving few possibilities to interpret the inferred fluxes from a mechanistic point of view. Measurements of carbonyl sulfide (COS) may help to fill this gap: COS has similar diffusion pathway inside leaves as CO2 but is not re-emitted into the atmosphere by the plant respiration. We explore here the benefit of assimilating both COS and CO2 measurements into the LMDz atmospheric transport model to constrain GPP and respiration fluxes separately. To this end, we develop an analytic inverse system based on the 14 Plant functional Type (PFTs) as defined in the ORCHIDEE land surface model. The vegetation uptake of COS is parameterized as a linear function of GPP and of the leaf relative uptake (LRU), which is the ratio of COS to CO2 deposition velocities in plants. A new parameterization of the atmosphere soil exchanges is also included. We use the system to optimize GPP and respiration fluxes separately at the seasonal scale over the globe. The results lead to a balanced COS global budget and a seasonality of the COS fluxes in better agreement with observations. We find a large sensitivity of the partition between the ocean emissions and the COS plant uptake to the LRU parameterizations.
Atmospheric CO2 during the Mid-Piacenzian Warm Period and the M2 glaciation.
Authors: de la Vega Elwyn , Chalk Thomas B. , Wilson Paul A. , Bysani Ratna , Foster Gavin L.
Published: March 2020

The Piacenzian stage of the Pliocene (2.6 to 3.6 Ma) is the most recent past interval of sustained global warmth with mean global temperatures markedly higher (by ~2-3 oC) than today. Quantifying CO2 levels during the mid-Piacenzian Warm Period (mPWP) provides a means, therefore, to deepen our understanding of Earth System behaviour in a warm climate state. Here we present a new high-resolution record of atmospheric CO2 using the δ11B-pH proxy from 3.35 to 3.15 million years ago (Ma) at a temporal resolution of 1 sample per 3-6 thousand years. Our study interval covers both the coolest marine isotope stage of the mPWP, M2 (~3.3 Ma) and the transition into its warmest phase including interglacial KM5c (centered on ~3.205 Ma) which has a similar orbital configuration to present. We find that CO2 ranged from ca. 390 ppm to ca. 330 ppm, with CO2 during the KM5c interglacial being ca. 370 ppm. Our findings corroborate the idea that changes in atmospheric CO2 levels played a distinct role in climate variability during the mPWP. They also facilitate ongoing data-model comparisons and suggest that, at present rates of human emissions, there will be more CO2 in Earth’s atmosphere by 2025 than at any time for at least the last 3.3 million years.  
Methane hydrate saturations at the Southern Hikurangi margin (New Zealand) estimated from seismic and rock physics inversion
Authors: Turco Francesco , Gorman Andrew , Crutchley Gareth , Azevedo Leonardo , Grana Dario , Pecher Ingo
Published: March 2020

Geophysical data indicate that the Hikurangi subduction margin on New Zealand’s East Coast contains a large gas hydrate province. Gas hydrates are widespread in shallow sediments across the margin, and locally intense fluid seepage associated with methane hydrate is observed in several areas. Glendhu and Honeycomb ridges lie at the toe of the Hikurangi deformation wedge at depths ranging from 2100 to 2800 m. These two parallel four-way closure systems host concentrated methane hydrate deposits. The control on hydrate formation at these ridges is governed by steeply dipping permeable strata and fractures, which allow methane to flow upwards into the gas hydrate stability zone. Hydrate recycling at the base of the hydrate stability zone may contribute to the accumulation of highly concentrated hydrate in porous layers.
To improve the characterisation of the hydrate systems at Glendhu and Honeycomb ridges, we estimate hydrate saturation and porosity of the concentrated hydrate deposits. We first estimate elastic properties (density, compressional and shear-wave velocities) of the gas hydrate stability zone through full-waveform inversion and iterative geostatistical seismic amplitude versus angle (AVA) inversion. We then perform a petrophysical inversion based on a rock physics model to predict gas hydrate saturation and porosity of the hydrate bearing sediments along the two ridges.
Our results indicate that the high seismic amplitudes correspond to the top interface of highly concentrated hydrate deposit, with peak saturations around 35%. Because of the resolution of the seismic data we assume that the estimated properties are averaged over layers of 10 to 20 meters thickness. These saturation values are in agreement with studies conducted in other areas of concentrated hydrate accumulations in similar geologic settings.
Past and future changes in tropical climate amplified by the Indian Ocean
Authors: DiNezio Pedro
Published: March 2020

Presently, the Indian Ocean exhibits a unique climate state with subtle east-west contrasts and weak year-to-year variability. Whether these features could change in response to external forcings remains highly debated, an issue that is critical to predict future climate changes in highly populated neighboring countries. We explored this question combining climate reconstructions and numerical simulations and of the Last Glacial Maximum – the interval ca. 21,000 years ago when the Earth experienced the largest, most recent climate change. We found that the Indian Ocean exhibited radically altered rainfall patterns and oceanographic conditions across the basin, changes that according to our simulations, can only be explained by the amplifying effect of coupled ocean-atmosphere feedbacks. We also find that these changes favored the emergence of an El Niño mode driving significantly stronger climate variability. Despite different triggers in the past and the future, our results show that Indian Ocean climate could also be highly sensitive to future greenhouse forcing.
Forging the path to achieving land degradation neutrality: Global patterns and drivers of land degradation at global scales
Authors: Zvoleff Alex , Noon Monica , Daldegan Gabriel , Gonzalez-Roglich Mariano
Published: March 2020

Land degradation – the reduction or loss of the productive potential of land – is a global challenge. More than 20% of the Earth’s vegetated surface is estimated to be degraded, affecting over 1.3 billion people, with an economic impact of up to US$10.6 trillion. Land degradation reduces agricultural productivity and increases the vulnerability of those areas already at risk of impacts from climate variability and change. Addressing land degradation, Sustainable Development Goal (SDG) target 15.3, is essential to improve the livelihoods of those most affected, and to build resilience to safeguard against the most extreme effects of climate change. Drivers of land degradation include natural processes and human activities, and understanding such drivers is key for deploying effective interventions for addressing it. The parties to the United Nations Convention to Combat Desertification (UNCCD) have adopted a framework for assessing and monitoring land degradation at national scale, by measuring three sub-indicators: Changes in land cover, changes in soil organic carbon, and changes in primary productivity. In this study, we use the framework developed by the UNCCD and Trends.Earth, the most widely tool used for producing such indicators, to assess land condition globally for the period 2001-2015, the SDG 15.3.1 baseline period. Using a Bayesian hierarchical model, we then assessed the contribution of 12 drivers of land degradation, including key biophysical and anthropogenic variables, to the observed patterns to provide insight into the main drivers of land degradation at global, regional, and national scales. These results are critical for designing locally relevant plans for assessing land degradation contributing to the global goal of achieving a land degradation neutral world by 2030. The results of this analysis allow identification of not only the significant drivers in a given region, but also of those areas where unexpected trends (either improvement or degradation) are indicative of potential policy successes or failures.
Management-induced soil water erosion and nutrient losses in different land use in Mediterranean environment
Authors: Bogunovic Igor , Telak Leon Josip , Pereira Paulo
Published: March 2020

Soil erosion by water is one of the most important degradation processes. Land use has important effects on soil properties, therefore it is key to identify the type of management that have more impacts and find solutions to mitigate it. In order to understand the effects of land use management on soil and soil erosion in the Istria region (Croatia), we studied the impacts of different agriculture practices (vineyard, cropland, and olive orchard) on soil properties and runoff. The simulated rainfall was carried out at 58 mm h−1 in the summer of 2018 (30% soil water content) for 30 min on 0.785 m2 circular plots. The results showed that bulk density was significantly higher in cropland plots than in the vineyard and olive orchard. Soil organic matter, mean weight diameter, and aggregate stability were significantly higher in olive orchard plots than in the vineyard and cropland. Runoff and sediment losses were higher in olive orchard compared to vineyard plots. Carbon, nitrogen, and phosphorus losses were highest in olive orchard plots with 3.9 kg ha-1, 405.2 g ha-1 and 73.6 g ha-1, respectively, while lower values were measured in the vineyard plots, where nutrients losses were lower with 0.9 kg ha-1, 73.8 g ha-1 and 6.5 g ha-1, respectively. No runoff was observed in cropland plots. Even with the highest measured values of runoff and erosion in the herbicide treated olive orchard, results indicate that both herbicide application and tillage represent a threat to the sustainability of Istrian soils. Vegetation cover on cropland reduces the runoff generation indicating the need for adoption of conservation strategies. In current management, vegetation removal should be avoided since it contributes to practice to reduce nutrient losses and increase the sustainability of the soils.

 

Keywords: Soil water erosion, Soil tillage, Rainfall simulation, Agriculture land management, Mediterranean

 

Acknowledgements

 

This work was supported by Croatian Science Foundation through the project "Soil erosion and degradation in Croatia" (UIP-2017-05-7834) (SEDCRO).
Stable isotopic composition of CO, H2 and CH4 in the troposphere and lower stratosphere: results from the ATom-WAS samples
Authors: Popa Maria Elena , van der Veen Carina , Meinardi Simone , Blake Donald R. , Roeckmann Thomas
Published: March 2020

The NASA Atmospheric Tomography Mission (ATom) aimed to improve the understanding of atmospheric composition through global scale aircraft sampling campaigns in different seasons. The flights included continuous profiling between 0.2 and 12 km over the Atlantic and Pacific Oceans.

A large number of samples were taken using the Whole Air sampler (WAS, UC Irvine, CA). In a selection of these samples, we measured the stable isotopic composition of CO, H2 and CH4. The samples cover remote clean air from different latitudes, from troposphere and lower stratosphere, and air influenced by specific (pollution) sources or processes.

We will give an overview of the data available and the main characteristics. We observe large variations in the isotopic composition, showing the large scale influence of tropospheric sources and sinks, but also stratospheric processing. The three gas species are mainly affected by the same sources and processes but in different ways, thus giving complementary information on the atmospheric processes.
The IAEA carbonate reference materials aimed at the VPDB scale realization with low uncertainty.
Authors: Assonov Sergey , Fajgelj Ales , Gröning Manfred
Published: March 2020

The stable isotope scales of the light elements (H, C, O, S) are artefact-based (related to a primary reference material) and their practical realisation is based on several refence materials (RMs) traceable to the primary RM on a respective delta-scale. NBS19 carbonate, the primary RM for the VPDB scale introduced in 1987, exhausted in 2012, and its replacement was not available for several years. In 2016, IAEA-603 carbonate (replacement for NBS19) was released as the new primary RM having been carefully calibrated versus the remaining NBS19. The IAEA-603 uncertainty in δ13C and δ18O for the first batch (5200 ampoules produced) is ±0.010 ‰ and ±0.040 ‰ respectively (1-sigma level); the homogeneity assessment is the major component of total uncertainty which is limited by the best mass-spectrometer performance and the method (carbonate-acid reaction) reproducibility.

In 2015, monitoring of LSVEC (formerly the second scale-anchor on the VPDB scale) detected variable drifts in its δ13C value and therefore the use of LSVEC as RM for δ13C was discontinued. It was recognised that a replacement for LSVEC is needed for normalization of the δ13C measurement results, also to address the strict uncertainty requirements for δ13C observations in atmospheric CO2 and methane (≤0.01 ‰ and ≤0.02 ‰ correspondingly). Similar to IAEA-603, any new RMs will address the technical requirements for RMs laid out by ISO Guide 35: 2017 including (i) RM batch production and batch characterisation; (ii) homogeneity and stability assessment of the final product (RMs sealed off in 0.5 g ampoules) and (iii) value and uncertainty assignment based on the metrological traceability. Three new carbonate RMs are in preparation at the IAEA; the uncertainty in δ13C for all three materials due to RM’ homogeneity is already confirmed at ≤0.01 ‰ (on 10 mg aliquots), which is at the limit of the best modern mass-spectrometers. The isotopic characterisation of these new carbonate RMs is in progress; they should be released in 2020.

Together with IAEA-603, the three new RMs will provide a reliable realization of the VPDB scale with the lowest possible uncertainty. With these RMs users can (i) select RMs in a suitable δ13C range, (ii) detect any potential drift of RMs including the behaviour of daily lab-standards and (iii) detect any potential problem in applying the 17O correction at end-user laboratories. In conclusion, these new reference materials will allow laboratories worldwide to establish metrological comparability for decades.
Interannual variability of ocean surface waves in the Southeast Pacific
Authors: Aguirre Catalina , Becerra Diego , Godoy Marcelo , Silva Diego
Published: March 2020

Ocean surface (wind-driven) waves continuously shape the coastal environment and play a relevant role in ocean-atmosphere interaction processes. They are also important in operational aspects of ports and have significant energy potential. This research is focused on the interannual variability of the wind waves in the Southeast Pacific, particularly its relationship with the Southern Annular Mode (SAM) and El Niño Southern Oscillation (ENSO). We used a 38-year wave simulation (1979-2016) performed using the Wavewatch III model forced with surface winds and ice concentration from the ERA-Interim reanalysis. Additionally, a cyclone tracking software was used to analyze the trajectories of the extratropical storms which generate the wind waves that reach the coast of western South America. Time series statistics, such as correlation and composites analysis, have been applied to both wave parameters (such as significant wave height and mean period) and directional spectra. Results show a significant and positive correlation between the SAM and the significant wave height and the mean period of the wind waves. However, local storms in central Chile, which are the most damaging extreme wave events for coastal infrastructure, are less frequent during the positive phase of the SAM. Furthermore, a trend analysis shows an increase of the significant wave height during the last decades, which is consistent with the trend toward the positive phase experienced by the SAM. On the other hand, the wave energy of remote origin that travels from the North Pacific toward the Southeast Pacific, which is maximum during the austral summer, shows a significant relationship with the extreme El Niño events. These energetic swells events that reach the coast of western South America during the austral summer are more intense and frequent during the warm phase of ENSO.
Informing urban greenhouse gas quantification and mitigation using high-resolution CO2 emissions: a case study in Baltimore, USA
Authors: Roest Geoffrey , Gurney Kevin , Miller Scot , Liang Jianming
Published: March 2020

As atmospheric carbon dioxide (CO2) levels continue to rise, a global effort to mitigate greenhouse gas (GHG) emissions is underway. Urban domains, which are responsible for more than 70% of global anthropogenic CO2 emissions, are emerging as leaders in mitigation policy and planning – especially in the United States of America (US), which has formally withdrawn from the Paris Agreement. However, cities face obstacles in developing comprehensive and spatially explicit GHG inventories to inform specific actions and goals. The Vulcan emission product provides highly resolved Scope 1 fossil fuel CO2 (FFCO2) emissions in space and time for the entire US, while the Hestia emission products utilize even more granular spatiotemporal data within four US urban domains. Here, we present results from Hestia for Baltimore – a colonial-era city on the Atlantic Coast of the US. Scope 1 FFCO2 emissions are dominated by energy consumption in buildings, onroad vehicle emissions, and industrial point sources. Large, systematic differences exist between Hestia and Baltimore’s self-reported GHG inventory, which follows the Global Protocol for Community-scale Greenhouse Gas Emission Inventories (GPC). These differences include entire sectors being omitted from emissions reporting due to a determination of ownership (e.g. Scope 1 vs. Scope 3), data gaps and limitations, and a conflation of Scope 1 and Scope 2 electricity production emissions. Urban planning may be better informed by utilizing additional data sources on fuel and energy consumption – especially fuel and energy that are not provided by a centralized utility – to develop comprehensive GHG emission estimates.
The variability and covariability of dissolved and particulate metal concentrations in the Rhine River
Authors: van der Perk Marcel
Published: March 2020

To predict the transfer and fate of metal contaminants in river systems, a thorough understanding of the factors controlling metal concentrations is essential. This study examines the variability and covariability of dissolved and particulate metal concentrations in the Rhine River at the Lobith monitoring station in the Netherlands in the period 2009 -2017. The data analysis concentrated on copper and zinc as these metals were not affected by limits of detection. The total copper and zinc concentrations are significantly linearly related to the suspended sediment concentrations. The intercept of this relation represents the mean dissolved metal concentration and the gradient the mean particulate metal concentrations. The thus estimated mean dissolved and particulate concentrations of zinc and copper resemble mean measured concentrations. For both metals, the particulate concentrations are only weakly positively correlated to the dissolved concentrations. This correlation can be attributed to the fact that both the dissolved and the particulate concentrations of copper and zinc are negatively related to river discharge, where the decline of the particulate concentrations in response to increasing discharge is relatively larger than that of the dissolved concentrations. When the particulate metal concentrations are standardised for the diluting effect of discharge, the standardised particulate metal concentrations do not correlate significantly with the dissolved concentrations. This may indicate that the sediment solid/liquid partition coefficients (Kd-values) for the considered metals vary considerably in time, although this hypothesis requires further investigation.
Microplastic-Induced Changes in Soil Quality and Functioning: Field Scale Trials
Authors: Jones Davey , Chadwick David
Published: March 2020

Microplastics represent an emerging threat to terrestrial ecosystems, however, our understanding of the fate and behaviour of microplastics in the plant-soil system remains poor. In this replicated, field-scale study we added microplastics (low density polyethylene) to soil at different dose rates representing contamination levels ranging from 0 to 10 t ha-1. These levels were chosen to cover both agricultural and urban contamination levels. Over a 12 month period, we studied a range of chemical, physical and biological soil quality indicators and wheat productivity to evaluate the impact of microplastics on the delivery of soil-related ecosystem services. Overall, we found little evidence to suggest that microplastics affect plant growth even at high dose rates. In contrast, microplastics had a significant impact on soil quality. The use of PLFA profiling and 16S metabarcoding of the bacterial and archaeal community, revealed changes in key microbial taxa at high microplastic doses. In addition, physiological profiling of the microbial community using lipidomics, untargeted metabolomics and targeted nitrogen metabolomics (using GC-MS platform) revealed significant shifts in microbial physiology. No appreciable effect of microplastics was seen on soil N and P dynamics, earthworm abundance or greenhouse gas emissions (CO2, N2O and CH4). Overall, our results suggest that microplastics do induce changes in soil quality, but that this has little overall effect on the delivery of key soil-related ecosystem services. These results contrast strongly with experiments performed in laboratory mesocosms where microplastics negatively affected plant growth and soil quality, and highlight the need to study the impact of microplastics at the field scale over longer timescales.
Carbon gas cycling in supraglacial debris covers
Authors: Brock Ben , Brown Grace , Mann Paul , Dunning Stuart
Published: March 2020

Debris-covered glaciers extend over 4000 km2 in the high Asian Mountains and are significant and expanding features of most of the World’s glacierized mountain ranges. Within supraglacial debris covers, a combination of fresh mechanically-weathered rock and an abundance of water and energy during melt seasons provides an ideal environment for chemical rock weathering and microbial activity. These processes involve exchange of carbon dioxide CO2 and methane CH4 with the atmosphere, while daytime heating of debris leads to evaporation of meltwater from the debris matrix. Debris-covered glaciers may therefore play an important role in regional and global cycling of major greenhous gases. This new project aims to address 2 key questions: (i) What are the important chemical and microbiological processes affecting carbon gas exchange within supraglacial debris covers? (ii) What are the rates and controls on gas exchange and how do these rates vary in time and space? Initial direct measurements of CO2 flux have been made using an eddy covariance (EC) and gas analyser system installed over debris cover at Miage glacier in the Italian Alps, during the melt season. Under fine weather conditions, there is a strong daily cycle in downwardly-directed CO2 flux, closely linked to variation in energy input to the debris, driven by the flux of shortwave radiation. In contrast, rainfall is associated with short pulses of upwardly-directed CO2 flux to the atmosphere. In common with previously published findings, these data indicate that supraglacial debris covers are a strong summer sink of CO2. At Miage glacier the mean summer (June-August) flux is almost 0.5 g carbon per day per square metre of debris, more than 2 orders of magnitude higher than reported fluxes over cryoconite. Current gas flux data are limited to a few points and this project will extend measurements to varying lithologies, elevations and glaciers in different climatic environments using portable greenhouse gas analysers in conjunction with the EC system. Direct flux measurements will be supported by in-field analysis of debris strucure and composition and subsequent laboratory analysis to determine the minerals, carbon content and microbial communities present in debris covers to uncover controlling processes and determine the relative roles of chemical weathering and microbial activity in carbon gas cycling.
Can elevated CO2 experiments explain the magnitude of the land carbon sink?
Authors: Zhang Huanyuan , Prentice Iain Colin , Terrer César , Keenan Trevor , Franklin Oskar
Published: March 2020

Based on Free Air Carbon Dioxide Enrichment (FACE) and other raised-CO2 experiments (eCO2), new hypotheses have been proposed to explain how the magnitude of the CO2 fertilization effect on biomass and biomass production depends primarily on soil nitrogen and phosphorus availability [1,2]. To test whether these hypotheses and measurements from eCO2 could explain the land carbon sink as independently determined from data and models, we combined a CO2 response curve for biomass production with a simple two-box model of biomass and soil to simulate the evolution of the land carbon sink during the past century. Results were compared to Dynamic Global Vegetation Model (DGVM) results, as reported by the Global Carbon Project, and to results from inversion studies based on atmospheric CO2 measurements. The interannual variability of the modelled land sink was realistic, dominated by the temperature dependence of heterotrophic respiration, and similar to DGVMs results. However, the magnitude of the derived land sink based on eCO2 results was smaller, and its geographical distribution was different to DGVMs average. Sensitivity tests showed that these findings were robust to reasonable variations of parameter values. The smaller sink is due to the smaller amount of vegetation biomass increment documented by eCO2 experiments in comparison with the mean predictions of DGVMs. A land sink closer to the observed one could be produced, however, when incorporating the hypothesis that nutrient-stressed plants export “excess” carbon (generated by increased photosynthesis, but unable to be used for growth) to the soil and that only a fraction of this excess carbon returns to the atmosphere.  This hypothesis requires further exploration but hints at a reconciliation between DGVMs that explain the land carbon sink without nutrient limitations, with experimental findings of (sometimes severe) restrictions on CO2 fertilization due to nutrient stress.

[1] Terrer et al. 2016, Science, doi.org/10.1126/science.aaf4610

[2] Terrer et al. 2019, Nature Climate Change, doi.org/10.1038/s41558-019-0545-2
Lithological controls on soil formation rates and the implications for soil sustainability
Authors: Evans Daniel , Quinton John , Tye Andrew , Rodes Angel , Davies Jessica , Mudd Simon
Published: March 2020

Soils deliver multiple ecosystem services and their long-term sustainability is fundamentally determined by the rates at which they form and erode. Our knowledge and understanding of soil formation is not commensurate with that of soil erosion, but developments in cosmogenic radionuclide analysis have enabled soil scientists to more accurately constrain the rates at which soils form from bedrock. To date, all three major rock types – igneous, sedimentary and metamorphic lithologies – have been examined in such work. Soil formation rates have been measured and compared between these rock types but the impact of rock characteristics such as mineralogy or porosity on soil formation rates has seldom been explored. In this UK-based study, we addressed this knowledge gap by using cosmogenic radionuclide analysis to investigate whether the lithological variability of sandstone governs pedogenesis. Soil formation rates from two arable hillslopes underlain by different types of arenite sandstone were calculated. Rates ranged from 0.090 to 0.193 mm yr-1 and although the sandstones differed in porosity, no significant differences in soil formation rates were found between them. On the contrary, these rates significantly differed from those measured at two other sandstone-based sites in the UK, and with the rates compiled in global inventory of cosmogenic studies on sandstone-based soils. We suggest that this is due to the absence of matrix and the greater porosities exhibited at our UK sites in comparison to the matrix-abundant, less porous wackes that have been studied previously. We then used soil formation rates to calculate first-order soil lifespans for both of our hillslopes. In a worst case scenario, the lifespan of the A horizon at one of our sites could be eroded in less than 40 years, with bedrock exposure occurring in less than 190 years.  This underlines the urgency required in ameliorating rates of soil erosion. However, we also demonstrate the importance of measuring soil erosion and formation in parallel, at the site of interest, rather than calculating a mean rate from the literature, as we demonstrate soil formation rates can vary significantly among variants of the same rock type.

 
Parameters of infiltration models as affected by the measurement technique and land use
Authors: Karahan Gülay , Kim Seongyun , Pachepsky Yakov
Published: March 2020

Infiltration is strongly affected by soil structure. The measurement technique and the land use are two soil structure-related attributes that are typically available in descriptions of infiltration experiments. We hypothesized that these attributes may be good predictors of the performance of different infiltration models, and of the parameter values in those models. The international soil infiltration database SWIG assembled in the Institute of Agrosphere in Jülich, Germany, was used as the data source. The database encompasses about 5000 experiments all over the world, Texture, measurement method and land use were known for all experiments, availability of organic carbon content, bulk density, saturated hydraulic conductivity (Ksat), pH, the electrical conductivity of saturated paste, and initial water content varied. Comparison of the performance of eight infiltration models showed that Horton and Mezencev models outperformed all others and that one of these two models could be preferred based on the infiltration measurement method. The machine learning method – regression trees – was applied to find the most influential predictors of parameters of Horton and Mezencev models. The measurement method, the textural class, and the land use were the most influential predictors in 80% of cases for both models. The measurement method was the most influential input in 40% of cases. The accuracy of parameter estimates increased when only the subset of measurements with the same method was used to estimate infiltration parameters. Land use, textural class, and organic carbon content dominated as the most influential predictors for the parameters of the Mezencev model, whereas land use, textural class, Ksat, and bulk density became most important in the case of the Horton model. Overall, estimates of the infiltration equation parameters can be more accurate if they have been developed for the same measurement method as in the task in hand. Land use category and the infiltration measurement method provide useful surrogate information about the soil structure effect on infiltration. 
Hydroclimatic control on global weathering regimes
Authors: Calabrese Salvatore , Porporato Amilcare
Published: March 2020

Chemical weathering strongly impacts the evolution of the Critical Zone and the climate system. The large number of factors affecting weathering rates, however, makes it difficult to interpret measurements across different climatic and geologic settings. Here, we use the π theorem of dimensional analysis to develop a theoretical framework for global datasets of chemical weathering rates. The analysis reveals the dominant role of wetness on the chemical depletion of parent materials and provides a functional relationship to estimate the chemical depletion fraction from readily available climatic variables. Based on this finding, we calculate the spatial distribution of chemical depletion fraction and identify the areas where weathering rates are limited by the supply of fresh minerals or by water availability, and the areas where they are susceptible to future shifts in wetness.