United States

Mercury (Hg) contamination in the Gulf of Trieste (GT, northern Adriatic Sea) is due to historical mining activity at Idrija (Slovenia) and still represents an environmental issue of great concern (Covelli et al., 2001; Covelli et al., 2021). Indeed, the freshwater inputs from the Isonzo/Soča River have been identified as the main source of Hg into the GT. At the river mouth, the element was found to be mainly associated with the suspended particulate matter, especially following periods of medium-high river discharge and river plume events in the GT (Covelli et al., 2006; 2007) The primary aim of this research is to evaluate the occurrence and distribution of both dissolved (DHg) and particulate (PHg) Hg along the water column in the northernmost sector of the GT, a shallow and sheltered embayment suitable for the accumulation of fine sediments and contaminants. In order to achieve this objective, sediment and water samples were collected at six sites which were representative of different targets, such as mussel farming and tourism activities. Moreover, different environmental conditions including unperturbed and perturbed hydrological conditions, induced by both natural and anthropogenic factors, were taken into account. The amount of Hg in the surface sediments (0.77–6.39 µg g-1) as well as the relationship between the Hg concentration and the percentage of the 2-16 µm grain size fraction from this study were found to be consistent with previous research focused on the whole Gulf, thus testifying the common origin of the sediment. Results showed a notable variability of DHg (0.07–149 ng L-1) and PHg (0.39–12.5 ng L-1) depending on the interaction between riverine and meteo-marine hydrological conditions at the time of sampling. Mercury was found to be mainly partitioned in the suspended particles and elevated values of PHg were observed following periods of high discharge from the Isonzo/Soča River confirming that the river discharge may represent an important factor in regulating the amount of PHg in the GT.

SGI 2021

Mercury in the water column of the Gulf of Trieste is still an environmental issue: the legacy of the Idrija mine twentyfive years after its closure

Welcome Seabirders!  

Welcome to Virtual World Seabird Conference 3 - vWSC3! Whether you are in your office or lab, at home, in a coffee shop or bar poaching some wifi, or at a remote field site or research vessel – we are very excited to welcome you to the third ever World Seabird Conference. 

We would like to thank ALL of you for being so patient as WSC3 was scheduled, postponed, rescheduled, revised to virtual, and scheduled again. Throughout all those iterations there was one message that remained perfectly clear – seabirders were eager to meet and share their science. If we could not meet in person then virtual it would have to be, but a 3rd WSC was something everyone wanted. That support and commitment helped the WSU Board of Directors and Member Societies sort through all of the challenges they faced to plan and hold this conference. 

The list of those that need to be thanked is long and, while we plan on recognizing many during the live closing plenary, it is important to do so here in writing as well. 

The Australasian Seabird Group was our Local Host for our plan to meet in Hobart, Tasmania. They invested substantial time and effort to find venues and plan events that we unfortunately were not able to visit. Nonetheless we appreciate their work on behalf of WSC3 and encourage all of you to thank them when you see their members in Gathertown or elsewhere during our virtual meeting. Their willingness to host created the initial excitement for WSC3 and without that our vWSC would not have been possible.

We also wish to thank the Science Program Committee, the Virtual Committee, and the Early Career Scientist Committee for their hard work planning the logistics, events, and schedule for vWSC3. These committees also had to deal with changing parameters and short timelines that made what is always a challenging task even more challenging. The Travel Awards Committee also invested time and effort in developing procedures for awarding travel funds that ultimately would not be implemented. 

Our ability to shift from an in-person to a virtual meeting, and to do so in a way that would be financially feasible, was due to the effective efforts of The International Fundraising Committee and to our financial sponsors. The IFC raised funds to support WSC3 and then, through the good relationships they built with sponsors, ensured we could re-envision how those funds could be used to support a virtual conference that would be affordable and high-quality.

We all owe the WSU Board of Directors and the Representatives of the Member Societies a great deal of thanks. They are the ones who manage the WSU and, for the past 18 months, have had to have a series of challenging meetings and conversations, have had to make a series of difficult choices, have had to do all of that while considering the short- and long-term health of WSU and the World Seabird Conferences, and did this while also managing their own challenges at their day jobs. We are grateful for their diligence, patience, foresight, and throughout all of the meetings, their collegiality. Also – a 6-year term is quite a commitment!

There would not be a WSC3 without a successful WSC1 and WSC2. Thanks go to the Pacific Seabird Group for their support of WSC1 in Victoria, Canada, and to the African Seabird Group for their support of WSC2 in Cape Town, South Africa. In each of these endeavors and for our current conference we were fortunate to work with a dependable and trustworthy partner in Podium Conferences. Michelle Smith and Marischal de Armond have become valued members of our team and have not only helped us plan conferences but have assisted and advised the WSU Chairs and Board on issues above and beyond conference planning. 

As we embark on our vWSC3 week we extend to all of you our thanks for showing up, for being patient, and most importantly for the work you do with seabirds. We are all part of a unique, global community that shares an interest, a fascination, and a passion for birds that make a living in our world’s oceans. We have advanced the science, conservation, and management of seabirds as well the ecosystems they inhabit. We are consistently impressed and motivated by the work you do. 

The WSU formed in 2010 because we saw the need for a global organization to address challenges at a global level. Over the past 11 years WSU has grown, adapted, and evolved to become the community that this week is making vWSC3 a reality. Enjoy the week, appreciate and support the friends and colleagues you have made in the community, and if you see us in a virtual hallway please stop and say hello! 

Thank you for the opportunity to serve all of you and the WSU over the past few years,

Nicholas Carlile, Interim Chair, WSU<br>
Patrick Jodice, 2nd Chair of the WSU<br><br>

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3rd World Seabird Conference

Join us for four days of science, networking and virtual engagement with delegates from around the world!

technical paper

**Attenzione, gli orari riportati nel PROGRAMMA (icona calendario) si riferiscono al fuso orario locale dell’utente. Il fuso orario ufficiale del Congresso è Central European Time (CET).**

L'Istituto Nazionale di Oceanografia e Geofisica Sperimentale - OGS e il Dipartimento di Matematica e Geoscienze dell'Università di Trieste sono orgogliosi di ospitare il 90° Congresso della Società Geologica Italiana a Trieste dal 14 al 16 settembre 2021. La modalità del congresso è interamente online.

Con il motto "Geologia senza frontiere" questo evento mira a promuovere le Scienze della Terra come disciplina scientifica proiettata nel futuro, oltre i confini geografici, politici e disciplinari, per comprendere meglio l'interno del Pianeta Terra e la struttura del sottosuolo, difendere la società da pericolosi eventi geologici, comprendere meglio la variabilità climatica, pianificare l'utilizzo delle georisorse in modo etico e nel rispetto dell'ambiente.


**Please note, times listed in the SCHEDULE tab (calendar icon) reflect YOUR LOCAL TIME ZONE. The main timezone for this conference will be Central European Summer Time.**

The National Institute of Oceanography and Experimental Geophysics - OGS and the Department of Mathematics and Geosciences of the University of Trieste are proud to host the 90th Congress of the Italian Geological Society in Trieste on 14-16 September 2021.  The Congress will be held entirely online.

With the motto "Geology Without Borders" this event aims to promote Earth Sciences as a scientific discipline projected into the future, beyond geographical, political and disciplinary boundaries, to better understand the interior of Planet Earth and the structure of the subsurface, defend society from dangerous geological events, better understand climatic variability, plan the use of geo-resources in an ethical way and respecting the environment.


Welcome to the SGI2021 virtual conference.  In order to access the conference and content, [please register for the meeting here](https://www.geoscienze.org/trieste2021/index.php/registrazioni/registrati)

Please register for the SGI conference to join the event.

Earth Sciences should be understood not only as necessary for a better understanding of the interior of the planet Earth, but also as a defense of society from dangerous geological events, for the understanding of climatic variations, for the planning and use of georesources in a ethical and respecting and protecting the environment.

On 11 and 12 October 2018, Sardinia was hit by exceptional meteorological events that particularly affected the south-eastern area, in the Sarrabus, and in particular various road infrastructures under the responsibility of the Province of Southern Sardinia. The administrative procedure of the interventions originated from the Resolution of the Council of Ministers of 8 November 2018 which declared a state of national natural disaster. Subsequently, the Ordinance of the Head of the Civil Protection Department n ° 558 of 15 November 2018 was issued, which allowed the first management activities to be started for the planning of the first interventions, the rescue and assistance to the population and the restoration of functionalities of infrastructures affected by adverse phenomena. The Province, following an inspections carried out by the geologists and the engineers of the Traffic Service, identified 9 intervention areas, particularly affected by flood events. Among these, the one in correspondence with the bridge of the Camisa locality, at Km 23 + 250 of the provincial road n ° 20, was particularly critical. The procedures for safeguarding public safety and the structure concerned were immediately activated, in conjunction with the Prefecture, the Regional Civil Protection and the municipalities concerned. The temporary interruption of the road was arranged, which at the "Ponte Camisa" was bypassed by the large flow rates of the Rio Corr'e Pruna. The bridge was affected by an exceptional flood which led to the removal of a large part of the road foundation, embankments and escarpments. In the following days an initial census was made of the serious damage caused, which led to interruptions in the road network, narrowing of the carriageway and considerable risk conditions for public safety. An estimate of the damage was made and the request for funding was forwarded to the Civil Protection of the Sardinia Region. This estimate concerned the restoration of the work of art and the complete functional recovery and safety of the road artery. The works to be designed also include the verification of the residual functionality of the bridge in the riverbed, the previously installed gabions and the geological and hydraulic study of the erosive phenomena that have occurred. Following the granting of the requested funding, the restoration work was contracted out, the artifacts were rebuilt, the embankment works and the river bed were strengthened and restructured, able to better withstand any new calamitous events. Appropriate management procedures for the work were therefore provided in the event of an alert of adverse weather conditions. A first study was therefore carried out aimed at reducing the persistent risk on the area, for which the request for funding for the execution of the mitigation of the danger parameters of the area is being investigated.

Civil protection interventions - OCDPC n. 558 of 15.11.2018 - Functional recovery of the Provincial Road No. 20 - Municipality of Castiadas (Sardinia)

On 11 and 12 October 2018, Sardinia was hit by exceptional meteorological events that particularly affected the south-eastern area, in the Sarrabus, and in particular various road infrastructures under the responsibility of the Province of Southern Sardinia. The administrative procedure of the interventions originated from the Resolution of the Council of Ministers of 8 November 2018 which declared a state of national natural disaster. Subsequently, the Ordinance of the Head of the Civil Protection Department n ° 558 of 15 November 2018 was issued, which allowed the first management activities to be started for the planning of the first interventions, the rescue and assistance to the population and the restoration of functionalities. infrastructures affected by adverse phenomena. The Province, following an inspection carried out by the geologists and engineers of the Traffic Service, identified 9 intervention areas, particularly affected by flood events. The situation of the provincial road No. 97 was particularly critical, with seven road sections affected by erosive phenomena and a great state of alteration caused by the considerable outflows that occurred during the calamitous event. The procedures for safeguarding public safety and the structure concerned were immediately activated, in conjunction with the Prefecture, the Regional Civil Protection and the municipalities concerned. Various roadway narrowings have been prepared due to strong erosion phenomena which have led to a great increase in the danger to road users. The main hydro-geomorphological erosion phenomena concerned: - at Km 2 + 600, erosion of the embankment of the road embankment on the progressive right, for about 40 meters and a height of 2.5 meters, failure of the guard rail, anomalous accumulation of materials in the docks; - at Km 3 + 200, burying of the gutter for a length of 20 meters and of a “road manhole” crossing infrastructure; - at Km 3 + 850, strong erosion of the escarpment on the right side for about 75 meters in length and for heights ranging from 1 meter to 2.5 meters in height; failure of the guard rails on both sides of the road; - at Km 4 + 300, erosion of the right escarpment for a length of 16 meters and a depth of 1 meter and consequent erosion of the gutter, partially present also on the left side; - at Km 4 + 900, erosion of the right escarpment for 23 meters in length and 1 meter depth and consequent erosion of the quay, failure of the guard rail on both sides; - at Km 5 + 200, erosion of the embankment of the right road embankment for 14 meters in length and 1 meter in height, undermining of the crossing infrastructure and damage to underground services, failure of the guard-rail on the right side, erosion of the left embankment for about 23 meters of length and 1 meter in height, failure of the left guard rail; - at Km 5 + 400, erosion of the left gutter for 25 meters in length; An estimate of the damage was then made and the request for funding was forwarded to the Civil Protection of the Sardinia Region. This estimate concerned the restoration of the entire section of provincial road No. 97, and the complete functional recovery and safety of the road artery, both in shape and along the quays and appurtenances. The works to be designed also provide for the verification of the residual functionality of the bridge in the riverbed, the previously installed gabions and the geological and hydraulic study of the erosive phenomena that have occurred. Following the granting of the requested funding, the restoration work was contracted out, the artifacts were rebuilt, the hydraulic crossing works partially reinforced, able to better withstand any new calamitous events. A first study was therefore carried out aimed at reducing the risk persisting in the area, for which the request for a loan for the implementation of the intervention to mitigate the hazard parameters of the area is in the preliminary phase.

Civil protection interventions - OCDPC n. 558 of 15.11.2018 - Restoration and functional recovery of Provincial Road No. 97 - Municipalities of Castiadas and Muravera

Shallow landslides susceptibility assessment usually relies on the parametrization of hydraulic and geotechnical features of soils. Among these, saturated hydraulic conductivity (Ks) represents one of the most important soil properties that influences infiltration rates, runoff, groundwater recharge and drainage processes, which makes it of particular concern in the prediction of natural hazards including catastrophic floods and shallow landslides. On the other hand, it is well known that vegetation may play a positive role towards slope stability and over the last decades many efforts have been done in order to quantify the role of the vegetation towards protection from shallow landsliding (Giadrossich et al., 2017). Basically, there are two main vegetation effects: hydrological (e.g., reduction of the water pore pressure through tree rainfall interception) and mechanical ones (increase of the soil strength due to the presence of roots and increase of the soil shear stress due to the vegetation load). Soil Ks is expected to be an important factor that influences plant growth, plant-available water, root system and root biomass and, therefore, this work focuses on the quantitative assessment of the relationship between vegetation characters and hydraulic conductivity. Study areas affected by shallow landslides were chosen in the Garfagnana and Cardoso basin (Northern Apennines, Italy) and in Mt. Amiata volcano (Southern Tuscany, Italy) where field measurements (about 200) of below-ground vegetation (Root Area Ratio - RAR), above-ground vegetation (Leaf Area Index-LAI and vegetation load) and Ks were carried out inside, in the neighbour and far outside shallow landslide locations. Acquisition of data within landslides areas was supported by means of a multi-temporal landslide inventory already available for study areas. Below-ground vegetation data were collected in trench profiles, while above-ground vegetation data were acquired using digital relascope and digital cover photography. Measurements of Ks were carried out by means of both constant and falling head permeameters. Results showed that RAR and soil depth affected Ks, with a decrease of Ks as the depth increases and roots decrease. Moreover, Ks varied for different vegetation types, indicating that shifts in aboveground vegetation features may strongly impact the water dynamics of soil. Above-ground vegetation plays a slight negative role on slope stability. Instead, root reinforcement to soil in terms of a root-related cohesion parameter plays a relevant role for depths involved in shallow landslides.

Influences of vegetation characters on saturated hydraulic conductivity at catchment scale

Shelves surrounding volcanic islands represent only a small portion of the entire submarine edifice that can range a few thousand meters below sea level. Despite their small area, the erosional, depositional, tectonic and volcanic processes affecting the subaerial island leave a significant imprint on the shelf morphology when compared to the slope or the submarine base of the islands (Quartau et al., 2014). Therefore, shelf morphology can be used to improve our knowledge about the island evolution, especially the more recent events. In this study, we use multibeam bathymetry, side scan sonar and seismic reflection data of the southern shelf of Porto Santo Island in Madeira Archipelago to map its seabed morphology and seismic stratigraphy from the nearshore to the shelf edge (~100m b.s.l.), aiming to better understand the evolution of mass-movements affecting the area. In general, the shelf consists of an erosive rocky surface mostly covered by sediments, and locally outcropping on the seafloor. The sedimentary cover on the shelf is highly variable both in thickness and internal architecture, mainly due to different onshore sediment supply and available accommodation space. Two main seismic units have been recognized: the lower one (U1) is interpreted as a transgressive deposit, formed during sea level rise after the Last Glacial Maximum (LGM); the upper one (U2) is interpreted as present-day highstand deposits. Based on the morphological and seismo-stratigraphic differences the study area has been divided in three sectors (Western, Central and Eastern). On the Western and Eastern sectors two sets of submerged erosional terraces have been mapped at different depths (35-45 m, 50-75 m b.s.l.). The overall arcuate shape of the southern shelf edge of Porto Santo Island strongly matches the coastline shape, suggesting the occurrence of an old large-scale landslide event (LS1),  prior to the shelf formation (Quartau et al., 2018a). Further incisions on the shelf edge of the Central sector, mapped at and upslope the shelf edge, imply more recent mass-movement processes, LS2 at least older than seismic unit U1 and LS3 formed on the late Holocene, indicating a retrogressive evolution of the instability process. The absence of erosional terraces in the Central sector supports this hypothesis, being probably removed by the LS2 event. The terraces depths and their destruction by the LS2 event suggests that these were formed/modified at least by the MIS 5a-5d stillstands or even by older ones. The estimated volume of the LS2 event (0.6 km3) suggests that it might have caused a hazardous tsunami if it failed as a single event. The recent LS3 events, due to their small magnitude were probably not hazardous. In summary, three different mass-movements were defined according to their dimension and position on the shelf: from LS1 to LS3, the scars are increasingly smaller and further upslope. These observations provided a more comprehensive understanding of the recent evolution of Porto Santo insular shelf in terms of mass-movement processes.

Small-scale instability processes affecting volcanic island shelves: the case study of the southern shelf of Porto Santo Island (Madeira Archipelago)

Assessment of the stability of rock masses is crucial in the process of risk mitigation. Among the many factors predisposing the Italian territory to geohazards, it has to be mentioned the geological and geomorphological setting, often characterized by karst processes and widespread presence of cavities, of both natural and anthropogenic origin, potentially leading to sinkholes and other instability mechanisms. For these reasons, the study of rock masses has always been of primary importance, as a primary tool to define the susceptibility to geological instability and to safeguard the environment. To solve the problems related to traditional analyses, in many cases too expensive and difficult to carry out, over the last decade the implementation of new digitalized methods, such as close- and long-range remote sensing techniques, has become essential to quantitatively describe the structural arrangement of rock masses. This necessarily requires robust and reliable methods dedicated to extracting the primitive geometries representing the discontinuities on a rock outcrop. A novel approach, combining observations made in situ with digital results, has been recently proposed (Cardia et al., 2021). This method is able to extract discontinuities clusters in a fully supervised way, thus allowing the user to evaluate every situation by determining specified tolerance angle ranges for both dip/dip direction. We provide here an ongoing development of the method, based on an algorithm that has been implemented in the software GeoDS. The algorithm takes as input a K value, representing a density threshold, from which it will start searching for coplanar points in a given range of 10° for both dip and dip direction, and a seed range value, that is the number of sample points that the system chooses randomly to evaluate each cluster. The greater this value is set, the more successful is going to be the result; however, this comes with a computation time cost, which extent depends on the computer capability. This new algorithm, called IPDE (Iterative Pole Density Estimation) is then coupled with a KDE (Kernel Density Estimation), extremely useful to plot the graphic projection, on which the user can choose to manually select points or to evaluate the sets with two different automatic clustering techniques, K-means and Gaussian Mixture. The proposed method aims to improve the evaluation of discontinuities on a rock outcrop in a new and original way.

The Iterative Pole Density Estimation, a new approach to assessing the stability of rock masses from 3D point clouds

An increasing number of heavy precipitation events causing flash floods, debris flows and other types of landslides, as well as severe morphological effects on changes have affected Italy and Europe over the last years (Tarolli et al., 2012).  Italian territory is particularly prone to these types of phenomena, due to a combination of distinctive topographic and meteorological characteristics (Rinaldi et al., 2016). Extreme events induce physical impacts on rivers and valley bottoms, consisting in channel widening (due to bank erosion and overbank deposition), changes in bed level, avulsions, huge amount of sediment transport, as well as recruitment of large wood. On overall, channel widening is the dominant geomorphic effect observed in many rivers. If on one hand channel widening represents an essential process to sustain channel morphology and fluvial ecosystems, on the other hand, in highly populated fluvial corridors, it can result in the loss of agricultural land and damages to buildings and infrastructures; thus, it should be considered a natural hazard and a major management problem. Interests in geomorphic effects of large floods have been intensively increasing over the recent decades. At Italian level, several case study papers were published, and new integrated approaches were proposed (Rinaldi et al., 2016). Even, the Italian Istituto Superiore per la Protezione e la Ricerca Ambientale (ISPRA) have proposed a method (the Event Dynamics Classification - EDC, Rinaldi et al., 2015) which provides tools to predict the geomorphic flood hazards, and supports the definition of morphological river corridors, meant to be complementary to inundation maps determined by “classical” hydraulic modelling. In light of this, an overview of recent studies on flood events at Italian level is presented, with the aims to highlight similar trends in channels changes induced by large floods and to assess the relative role of the different hydrological and morphological factors controlling the flood geomorphic effectiveness.

Geomorphic effects of large floods: some examples from Italian rivers

Sediment transfer in mountain streams occurs via processes classified as debris flows, debris floods, and water flows. The analysis of the sediment-water flows occurring during high-magnitude floods is currently a scarcely explored issue. This knowledge gap is particularly striking for the debris floods, a water-driven flood flow with extremely high bedload transport that has been rarely investigated. This study investigates how the transport mechanisms activated in a mountain stream during a high-magnitude flood differ from those triggered during ordinary floods, focusing on the controlling factors and conditions required for debris flood occurrence. The study area is the Tegnas catchment (drainage area 51 km2), a mountain basin of the Dolomites (northeastern Italy) affected in October 2018 by a severe flood (Vaia Storm), whose recurrence interval has been estimated to approximately 200 years. We developed a post-flood survey protocol for distinguishing various flow types based on the features of the flood deposits. The transport processes typifying the stream network during ordinary floods and those occurred during the Vaia Storm were determined through the field survey of the deposits. We observed water flow as a response to ordinary events occurring along the entire Tegnas main stem. During the Vaia Storm, water flow still dominated, although debris floods were documented at several sub-reaches. The unit stream power induced by the Vaia Storm was calculated based on the peak discharge computed at the sub-reach scale using a rainfall-runoff model, and channel widening was determined measuring the pre- and post-Vaia channel width. The comparison between the high-magnitude and the ordinary flows allowed us to infer the existence of relationships between the transport mechanisms, the hydraulic forcing, and channel dynamics. The upheaval of the ordinary flow types did not occur along the entire stream network: water flows transitioned into debris floods only under unit stream powers exceeding the threshold of 5500 Wm–2 or downstream of sediment-injection sites. Debris floods occurrence appears to be facilitated by tributaries prone to debris flow and connected to the receiving stream, the injection of fine material into the flows (which can occur as consequence of channel-bank erosion or overbank floodwater re-entering the channel), and channels characterized by high slope and relative narrow section. The occurrence of debris floods caused higher channel widening than that induced by water flows. The complex relationships found between flow types and a range of controlling factors reveal that a detailed characterization that includes field observations is necessary to understand the transport mechanisms that can affect a specific channel site during high-magnitude hydrological events for an accurate and reliable definition of flood hazard at the local (e.g., sub-reach) scale.

Debris floods in mountain streams: Insights from the Vaia Storm (October 2018) in the Tegnas catchment (Dolomites, Italy)

Several heavy precipitation events causing flash floods, debris flows, landslides, and morphological channel changes have occurred in Europe over the last years. In mountain environments, mass movements along the hillslopes are important sources of sediment supply to the rivers, and may enhance the geomorphic effects of floods. The Stolla creek (catchment area: 40 km2) is a confined/partly confined channel of the Dolomites (Easter Italian Alps), that was affected by an extreme flood in August 2017, and by a moderate flood in August 2020. The geomorphic effects of the two floods were investigated in the main channel and along the hillslopes with the aims: to compare the channel changes induced by the two events; to assess the impacts of the lateral sediment connectivity to the channel response. A multi-methodical approach was applied, including radar rainfall estimation, rainfall-runoff modeling, field surveys, remote sensing, geomorphological and statistical analysis. Hillslope and channel processes were mapped by comparing multitemporal orthophotos and Digital Terrain Models. Debris-flow connectivity to the main channel was derived by combining field evidence and geomorphometric analysis. The 2017 flood was caused by rainfall with a short duration (6 hrs) and a rain rate exceeding 45 mm in one hour. More than 600 debris flows were triggered along the hillslopes, among which 23 were connected to the Stolla. Important discontinuities for the sediment flux were represented by the floodplains. The Stolla channel experienced channel widening occurred through bank erosion, and overbank depositions. With ratio (ratio between the channel width after and before the flood) was between 1.3 and 4.9. Widening was accompanied by channel bed aggradation up to 1.2 m or incision up to -2.2 m. Widening through bank erosion was more common in narrower reaches, affected by higher flood power, and presenting higher connectivity with debris flows. Although 294,000 m3 of sediments were eroded in the connected debris flows and 12,380 m3 were transferred to channel from toe erosion processes, limited volumes of sediments (< 1000 m3) were exported to the catchment outlet. The 2020 flood event was characterized by a lower rain rate (max 17 mm h-1) and a long duration (48 hrs) and did not trigger debris flows. The moderate magnitude of the flood peak did not lead to channel widening, but only bed incision (up to -1.4 m) in the reaches where the 2017 event had caused channel-bed aggradation occurred. 

Catchment response to different severity storm floods: channel variations and hillslope sediment coupling dynamics

The Apuan Alps are a mountain range in northern Tuscany exploited for the famous Carrara marble since the Roman age. The Apuan quarrying district currently comprises about 150 quarries and most of them are located at high elevations. Marble blocks are cut and re-squared by means of line drilling and various sawing techniques, diamond wire and chain saw being the most used. Such quarrying activities produce a fine marble powder that frequently mixes up with meteoric water, producing a slurry that can easily infiltrate into the karst aquifers through solution-enlarged fractures. Depending on the aquifer hydrodynamics, the marble slurry can eventually reach the karst springs, thus contaminating high quality waters generally used for the human consumption. Several samples of marble powder, karst spring deposits, and stream sediments were collected and analyzed for their mineralogical, morphological and sedimentological characterization, to evaluate the degree of pollution of the Apuan karst aquifers. Quarry powder samples are mainly made up of calcite crystals, whereas spring and stream sediment samples have variable proportions of calcite, silicates, and dolomite grains. The clasts from marble powder produced by diamond wire and chain sawing have constant morphological features, whereas the sediments collected in filtering tanks and disposal bags exhibit more heterogeneous characteristics. The quarry powders are generally finer than the sediments, although some overlap occurs probably because of marble powder contamination in the sediments themselves. The most polluted spring samples are characterized by a predominant calcite component that is finer than the silicate one. The same occurs also for the stream samples. Spring samples also show homogeneous morphometric features that are probably related to both marble powder contamination and the transport mechanisms through the karst aquifers. Marble powder pollution appears to be widespread in most of the Apuan karst springs, thus affecting the aquifer hydrodynamics and water quality.

Physical pollution of karst aquifers caused by marble quarrying: the case of the Apuan Alps, Italy

River waters may respond gradually or suddenly to natural or anthropic disturbances by varying their chemical composition. Understanding the nature of these complex interactions plays a crucial role in our fast-changing planet threatened by climatic and human-induced changes. In this work, water chemistry is analyzed as a whole by focusing on its interconnections with hydro-litho-morphologic and anthropic pressures at a basin-wide scale. This implies the introduction of the concept of regime shift, which has been widely applied to study the resilience of ecological systems to environmental perturbations. We propose to transpose this idea to geochemistry by considering Geochemical Regime Shifts (GRSs) as abrupt and permanent changes in the system state (composition) of a given environmental media, triggered by external or inner perturbations (Gozzi et al., 2021). From this perspective, river water composition represents a response variable resulting from the synergic action of environmental drivers and catchment properties. The aim of this study is to detect potential spatial GRSs in the water chemistry of the Tiber River, the third-longest Italian river. To reach this aim potential forcing variables (e.g. land use, terrain slope, human impact and lithology) were considered and estimated for all nested watersheds. Compositional Data Analysis, Robust Principal Component Analysis and score-distance graphs were used to explore data variability and the nature of driver-system state relationships. In the lower reaches, a potential regime shift was identified for major species suddenly changing the water composition from a relative prevalence of N-bearing species to that of Na+ and Cl-. The regime shift scenarios described by Andersen et al. (2008) suggest that the observed shift might represent a threshold-like state response triggered by lithological forcing. Conversely, no abrupt changes were detected for trace elements which instead seem to respond gradually to environmental pressures. The research offers new perspectives for future studies and for a deeper understanding of the circumstances controlling river system’s self-restoring capability.

Mercury in the water column of the Gulf of Trieste is still an environmental issue: the legacy of the Idrija mine twentyfive years after its closure

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Civil protection interventions - OCDPC n. 558 of 15.11.2018 - Functional recovery of the Provincial Road No. 20 - Municipality of Castiadas (Sardinia)

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Mercury in the water column of the Gulf of Trieste is still an environmental issue: the legacy of the Idrija mine twentyfive years after its closure

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