Beaches are dynamic coastal forms. However, nowadays, natural processes are intertwined with anthropogenic influences. The island of Hvar has 247 beaches from which we selected those which evolution could be studied by means of repeat photography method using archive maps and old photographs. More than 150 old photographs dating between the 1900s and 1980s have been collected and analyzed. The recent period is studied using unmanned aerial vehicles (UAV).
In total 12 beaches have been selected for precise study. The benchmarks from old photographs were marked and geolocated during the fieldwork using GNSS Trimble receiver. In November 2020, all locations were recorded by quadcopter DJI Phantom 4 Pro v2.0 with approximately 80% overlapping. On each beach, 6 - 12 ground control points (GCP), mostly benchmarks from the old photographs, were marked and measured. Data collected from UAV has been generated by photogrammetric techniques in ESRI Drone2Map software. Orthophoto and digital surface model (DSM) has been processed with a spatial resolution of 0,02 m and 0,1 m for the digital elevation model (DEM). All analyses were made using the ArcGIS Pro software. In this work, the analysis will be presented on two sites: Mina sand beach, formed in Aeolian deposits, on the northern side of the island and Mola Milna gravel beach, found on the southern side. Beaches have been studied in three points in time, in the 19th, 20th and 21st century.
On the Franciscan Cadastre (1834), Mina beach was mapped as an individual cadastral parcel with an area of 222 Klafter Quadrimeter (written in the Cadastral supplement), that is 799 m2. Recalculating in GIS we obtained a similar value, that is, 782 m2. The beach area from the beginning of the 20th century was reconstructed from old photographs and was approximated to 450 m2. Consequently, since 1834 the beach area reduced by ~43%. In 2020, the area further drops to 226 m2, so its surface diminishes by 55% since the beginning of the 20th century or even 72% from 1834.
In 1834 the Mola Milna beach was ~1073 m2, ~900 m2 in the 1950s (16% smaller) and finally 802 m2 in 2020 (11% less than in the 1950s, or 27% smaller compared to 1834).
Thus, we observed that during the last two centuries the sand beach Mina reduced for more than 2/3 of its size since 1834, while the gravel beach Mola Milna reduced for around 1/3. Similar results have been observed previously on the Zogon gravel beach which lost ½ of its size since the 1960s. Even if the reconstructions of the beach area from the Cadaster maps and old photographs are less accurate than the model generated from UAV photos, obtained values clearly reveal the trend of beach erosion during the studied period.
This research was made with the support of the Croatian Science Foundation (HRZZ-IP-2019-04-9445).
Atmospheric brown carbon (BrC) is a highly uncertain, but potentially important contributor to light absorption in the atmosphere. Laboratory and field studies have shown that BrC can be produced from multiple sources, including primary emissions from fossil fuel combustion and biomass burning (BB), as well as secondary formation through a number of reaction pathways. It is currently thought that the dominant source of atmospheric BrC is primary emissions from BB, but relatively few studies demonstrate this in environments with complex source profiles.
A field campaign was conducted during a month-long wintertime period in 2020 on the campus of the University of Peloponnese in the southwest of Patras, Greece which represents an urban site. During this time, ambient filter samples (a total of 35 filters) were collected from which the water-soluble BrC was determined using a semi-automated system similar to Hecobian et al. (2010), where absorption was measured over a 1 m path length. To measure the BrC, a UV-Vis Spectrophotometer was coupled to a Liquid Waveguide Capillary Cell and the light absorption intensity was recorded at 365 and 700 nm. The latter was used as a reference wavelength. We found that the average BrC absorption in Patras at a wavelength of 365 nm was 8.5 ± 3.9 Mm-1 suggesting that there was significant BrC in the organic aerosol during this period. Attribution of sources of BrC was done using simultaneous chemical composition data observations (primarily organic carbon, black carbon, and nitrate) combined with Positive Matrix Factorization analysis. This analysis showed that in addition to the important role of biomass burning (a contribution of about 20%) and other combustion emissions (also close to 20%), oxidized organic aerosol (approximately 40%) is also a significant contributor to BrC in the study area.
Reference
Hecobian, A., Zhang, X., Zheng, M., Frank, N., Edgerton, E.S., Weber, R.J., 2010. Water-soluble organic aerosol material and the light-absorption characteristics of aqueous extracts measured over the Southeastern United States. Atmos. Chem. Phys. 10, 5965–5977. https://doi.org/10.5194/acp-10-5965-2010
Volcanic eruptions are natural disturbances capable of introducing large quantities of sediment into river systems as to upset the transport regime for several years. Such a disturbance can have a strong impact on the water and sediment flows and consequently on the transport capacity. Moreover, changes in morphological settings and land cover lead to an alteration of the sediment connectivity within the catchment. This study aims to investigate the changes of sediment connectivity in a catchment affected by an explosive volcanic eruption using the Index of Connectivity (IC) with a multi-temporal approach. Potential variations were analyzed at the catchment scale over a period of 6 years, before and after the eruption. The study area, located in southern Chile, is the Blanco Este River basin (39,6 km²), affected by the eruption of the Calbuco volcano (April 2015, total volume of sediment expelled of about 0,28 km³) which profoundly changed its vegetation cover, geomorphology and hydrology. IC analyses were based on low-resolution and freely available data (i.e., GDEM, Landsat 8 satellite images). Through supervised image classification and field data survey, a Manning's n coefficient for overland flow is derived as weighting factor (W) due to its suitability to represent the impedance to sediment flows in catchments characterized by land cover variations. Following the eruption, bare soil cover on the basin doubled (from 5% to 10% of total basin area). Consequently, the multi-temporal analysis results in an overall increase of IC with the median value ranges from -3,58 to -3,26 in pre-eruptive (2015) and first post-eruptive scenario (2016), respectively. The connectivity maps show that the higher IC values (i.e. range from -1,23 to 1,66) are persistently located in three areas: at the base of the volcanic dome, on the steepest slopes near the main channel and in a sub-basin on the right side of the catchment. Moreover, the Difference of IC (DoIC) among different scenarios highlighted the major variations. Such changes are found along the volcano slopes, in a flat area located in the upper part of the basin and along the lower valley of the Rio Blanco Este. The study proposes a useful methodology to evaluate the sediment connectivity, and its evolutionary trends, in environments affected volcanic eruptions starting from low-resolution data and field survey. These results may help to better define types, location and typologies of interventions to improve the river management approaches, considering the ongoing cascading processes. This research is funded by the Fondecyt 1200079 project.
Novel technologies to store hydrogen in geological formations can substantially enhance New Zealand’s renewable energy market and help mitigate climate change impacts. New Zealand already supplies about 80% of its electricity demands from renewable sources, mostly geothermal, hydro and wind power. However, over 60% of the country’s net energy consumption still comes from fossil fuels. In New Zealand, extensive production and large-volume (>50,000,000 Nm3) storage of green hydrogen will be essential to buffer diurnal and seasonal shortage of hydro and wind power generation in a future energy mix dominated by renewable sources. Geological storage, technology in use since the 1970’s, is currently considered the best large-scale option for hydrogen storage globally.
Here we present preliminary results of an ongoing study into the feasibility of storing hydrogen in sedimentary and volcanic rocks across New Zealand. The country’s varied geology and diverse cultural communities provide a unique setting to evaluate the technical capacity, socio-environmental aspirations, and costs-benefits of hydrogen geo-storage for future domestic and export markets. We draw our investigation upon a substantial legacy dataset of petroleum exploration drillholes and seismic reflection surveys coupled with information from sedimentary and volcanic outcrops to determine the most suitable geological formations for hosting large-volumes of hydrogen nationwide. Four possible types of hydrogen geo-storage are considered: (i) construction of artificial rock caves, (ii) injection of hydrogen into sedimentary rocks and aquifers, (iii) utilisation of depleted natural oil and gas reservoirs and infrastructure; and (iv) hydrogen storage in highly porous and permeable volcanic rocks, the last of which would be a world first.
New Zealand has an extensive installed petroleum infrastructure, including 2,500 km of high-pressure gas pipelines and 17,960 km of gas distribution network to support the development of new hydrogen energy enterprises. Multiple depleted or depleting petroleum fields (e.g. Ahuroa, Kapuni and Maui) contain excellent reservoirs and efficient seal rocks confined in large (>25 km2) geological structures that offer scope for hydrogen storage. Porosity and permeability in commercial reservoirs vary from 5 to 25% and often up to several thousand millidarcys (mD), respectively, with high values of up to 9900 mD reported in sandstones of the Maui field. Studies in volcanic reservoirs on Banks Peninsula, Oamaru and offshore Taranaki Basin demonstrate that large sections of volcanoes (up to 1 km3) frequently have porosities of ca 50% and permeabilities above 100 mD, which may provide opportunities for storing hydrogen at relatively shallow (ca 100 m) depths.
Further technical assessment is ongoing to determine microbiological activity, chemical stability of rock targets, and geological modelling
Lawsonite is a strongly hydrated (12 weight % H2O) Ca- and Al-rich silicate, exclusively stable along low P/T gradients, typical of subduction zones. The distribution and preservation of lawsonite at the scale of a subduction/collision belt reflect the occurrence of rocks with favourable chemical composition (mainly hydrothermally altered metabasalts and marly limestones (i.e. calcschists), two lithologies especially common in the oceanic units) and their pressure-temperature-fluid history (with preservation favoured by decreasing T during decompression).
The distribution of lawsonite in the Western Alps has been investigated since several decades. In the blueschist-facies units from the South-Western Alps (Queyras, Ubaye), lawsonite is well preserved in the external domain, at the contact with the Briançonnais domain, but is largely pseudomorphed in the more internal domain, at the contact with the Viso Unit. Further North, neither lawsonite nor lawsonite pseudomorphs have been reported in the supposedly blueschist-facies Combin Zone, taken by most studies as an equivalent of the Queyras-Ubaye units. This constitutes a paradox with respect to the overall metamorphic structure of the Alpine belt.
This study documents for the first time several occurrences of lawsonite and garnet in the calcschists from the Combin Zone. Field and metamorphic data (thermodynamic modelling and Raman spectroscopy on carbonaceous material) point to the occurrence of two tectonometamorphic units within the Combin Zone, characterised by distinct geometry, lithological content and Alpine P-T conditions.
In the higher grade unit, lawsonite and garnet were stable at peak P-T conditions (~14-16 kbar and ~460-490 °C) at very low X(CO2) values. Although lawsonite is systematically pseudomorphed, we have been able to recognize hourglass zoning in lawsonite or preservation of an internal fabric associated with the prograde ductile deformation.
The lower grade unit (~8 ± 1 kbar ~370-400 °C) is discontinuously exposed along the western base of the Dent Blanche nappe and records Alpine P-T conditions similar to those reached by the Dent Blanche nappe (Manzotti et al. 2020).
Our data show that lawsonite is not missing in the Combin Zone, and resolve a paradox about the large-scale metamorphic structure of the Alps.
Manzotti, P., Ballèvre, M., Pitra, P., Müntener, O., Putlitz, B., Robyr, M. (2020). Journal of Petrology, egaa044, https://doi.org/10.1093/petrology/egaa044.
Induced seismicity from a gas-producing region such as Groningen is believed to be caused by reservoir depletion due to long-term gas production. However, because of the complexity and uncertainty regarding the underground structure and composition, it is difficult to quantify the effect on induced seismicity due to gas production. Here we use finite-element modelling to investigate the seismogenic potential of a pre-existing fault reactivated due to fluid depletion, considering different model settings. By applying quasi-static poroelastic loading representing reservoir depletion, the stress and strain fields are derived from the resulting displacement field. The equilibrium of the fault is then evaluated using either rate-and-state or slip-weakening behaviour for friction. When the critical state is reached on the fault, where the shear stress is greater than the friction, the reactivation of the fault takes place. This reactivation is simulated by using a dynamic solver to observe the propagation and the arrest of the dynamic faulting, as well as the resultant wavefield due to seismic slip. By comparing the depletion value at both aseismic and seismic ruptures, and looking at the stress distribution on the fault, the pattern of rupture nucleation, and the resulting seismic wavefield, we are able to evaluate separately the effect of different model settings, including the geometry and material property of both caprock and reservoir, reservoir depletion pattern, and the friction law. Furthermore, by combining our study with the observed seismic wavefield, it is possible to obtain useful insights on the spatial variation in the source region.
In the last decade, a range of new remote-sensing techniques has led to a dramatic increase in terrain information, providing new opportunities to understand better Earth surface processes based on geomorphic signatures. Light detection and ranging (LiDAR) technology and, more recently, Structure from Motion (SfM) photogrammetry have the capability to produce sub-meter resolution digital elevation models (DEM) over large areas. LiDAR high-resolution topographic surveying is traditionally associated with high capital and logistical costs. Remotely Piloted Aircraft Systems (RPAS) on the other hand, offer a remote sensing tool capable of acquiring high-resolution spatial data at an unprecedented spatial and temporal resolution at an affordable cost, thus making multi-temporal surveys more flexible and easy to conduct. The scientific community is now providing a significantly increased amount of analyses on the Earth’s surface using RPAS in different environmental contexts and purpose. The goal of this talk is to provide a few useful examples of surveys through airborne LiDAR and RPAS monitoring of anthropogenic landscapes with a specific focus on mining (e.g., open-pit) and agriculture (e.g., terraces). In details, multi-temporal surveys and geomorphometric indexes (including novel landscape metrics) have been carried out and tested in key study areas in order to (i) map the extension of the investigated features, (ii) track any anthropogenic change through time, (iii) analyze the effects of the change related to changes in erosion. The proposed analysis can provide a basis for a large-scale and low-cost topographic survey for sustainable environmental planning and, for example, for the mitigation of anthropogenic environmental impacts.
References
Understanding the coastal ocean variability and quantifying its significance in the global biogeochemical cycles is crucial to our ability to project future changes. In the shallow coastal waters, the contribution of the biological activity to water chemistry can be high locally, and responsible for seasonal and diurnal variations. These variations are not yet well-understood: they are often under-estimated and the general lack of observations means that they are seldom integrated into global predictive models such as those used by the IPCC.
In this presentation, we will present results on the natural carbonate chemistry diurnal variability in tidal rock pools in Brittany (France), during emersion times. We chose tidal rock pools as to represent "mini-coastal seas": realistic small mesocosms that simulate coastal environments with extreme variability. These have the advantage to be closed systems containing a range of calcifying organisms such as coralline encrusting and non-encrusting algae, that influence and are influenced by the carbonate chemistry. We calculated calcification of the pools community by using the alkalinity anomaly method and estimated the community photosynthesis/respiration. We also compared night-time dissolution and day-time calcification. Finally, we manipulated the pools chemistry at emersion by adding CO2 to mimick future acidification changes, and explored the impact of seawater acidification on the calcification of the tidal pools' communities.
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