Relationships between multibeam backscatter,sediment grain size and Posidonia oceanica seagrass distribution

The use of data, including bathymetry, backscatter intensity and the angular response of backscatter intensity, collected using multibeam sonar (MBS) systems to recognise seabed types was evaluated in the inner shelf of central western Sardinia (western Mediterranean sea), a site characterised by a complex seabed including sandy and gravelly sediments, Posidonia oceanica seagrass beds growing on hardgrounds (i.e. biogenic carbonates) and sedimentary substrates.     

New light on a dark subject: comment

In their article, “New light on a dark subject: On the use of fluorescence data to deduce redox states of natural organic matter,” Macalady and Walton-Day (2009) subjected natural organic matter (NOM) samples to oxidation, reduction, and photochemical transformation. Fluorescence spectra were obtained on samples, which were diluted “to bring maximum uvvisible absorbance values below 1.0.” The spectra were fit to the Cory and McKnight (2005) parallel factor analysis (PARAFAC) model, and consistent variation in the redox state of quinone-like moieties was not detected. Based on these results they concluded that fitting fluorescence spectra to the Cory and McKnight (2005) PARAFAC model to obtain information about the redox state of quinone-like moieties in NOM is problematic. Recognizing that collection and correction of fluorescence spectra requires consideration of many factors, we investigated the potential for inner-filter effects to obscure the ability of fluorescence spectroscopy to quantify the redox state of quinone-like moieties. We collected fluorescence spectra on Pony Lake and Suwannee River fulvic acid standards that were diluted to cover a range of absorbance wavelengths, and fit these spectra to the Cory and McKnight (2005) PARAFAC model. Our results suggest that, in order for the commonly used inner-filter correction to effectively remove inner-filter effects, samples should be diluted such that the absorbance at 254 nm is less than 0.3 prior to the collection of fluorescence spectra. This finding indicates that inner-filter effects may have obscured changes in the redox signature of fluorescence spectra of the highly absorbing samples studied by Macalady and Walton-Day (2009).     

Dynamical and chemical evolution of gas-rich dwarf galaxies

We study the effect of a single, instantaneous starburst on the dynamical and chemical evolution of a gas-rich dwarf galaxy, the potential well of which is dominated by a dark matter halo. We follow the dynamical and chemical evolution of the interstellar medium (ISM) by means of an improved two-dimensional hydrodynamical code coupled with detailed chemical yields originating from type II SNe, type Ia SNe and single low- and intermediate-mass stars (IMS). In particular we follow the evolution of the abundances of H, He, C, N, O, Mg, Si and Fe. We find that for a galaxy resembling IZw18, a galactic wind develops as a consequence of the starburst and it carries out of the galaxy mostly the metal-enriched gas. In addition, we find that different metals are lost differentially in the sense that the elements produced by type Ia SNe are lost more efficiently than others. As a consequence of that, we predict larger [ α /Fe] ratios for the gas inside the galaxy than for the gas leaving the galaxy. A comparison of our predicted abundances of C, N, O and Si in the case of a burst occurring in a primordial gas shows a very good agreement with the observed abundances in IZw18 as long as the burst has an age of ∼31 Myr and IMS produce some primary nitrogen. However, we cannot exclude that a previous burst of star formation had occurred in IZw18, especially if the pre-enrichment produced by the older burst was lower than Z =0.01 Z_⊙. Finally, at variance with previous studies, we find that most of the metals reside in the cold gas phase already after a few Myr. This result is mainly caused by the assumed low SN II heating efficiency, and justifies the generally adopted homogeneous and instantaneous mixing of gas in chemical evolution models.     

Synthesis and Preliminary Characterisation of New Silicate, Phosphate and Titanite Reference Glasses

Eleven synthetic silicate and phosphate glasses were prepared to serve as reference materials for in situ microanalysis of clinopyroxenes, apatite and titanite, and other phosphate and titanite phases. Analytical results using different micro-analytical techniques showed that the glass fragments were homogeneous in major and trace elements down to the micrometre scale. Trace element determinations using inductively coupled plasma-mass spectrometry (ICP-MS), multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS), laser-ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) and secondary ionisation mass spectrometry (SIMS) showed good agreement for most elements (Li, Be, B, Cs, Rb, Ba, Sr, Ga, Pb, U, Th, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Er, Tm, Yb, Lu, Zr, Hf, Ta, Nb) studied and provide provisional recommended values.     

Adaptive Strategies to Displacement and Environmental Change Among the Kaiabi Indigenous People of the Brazilian Amazon

Environmental change, geographical displacement, and disputes over land and resources have increased around the world. This article focuses on strategies developed by the Kaiabi indigenous people to cope and adapt to environmental change after development-forced displacement and resettlement in the Brazilian Amazon. A mixed methods approach was adopted, combining ethnographic and quantitative methods. Semistructured interviews were performed among 214 individuals in a study on the dynamics of indigenous knowledge (IK) and natural resource management across three Kaiabi lands. We identified seven main coping and adaptive strategies developed by the displaced group: leadership and reciprocity networks, mobility, maintenance and innovation of native language, knowledge articulation, substitution of strategic resources, transmission across genders, and revitalizing diversity. These strategies have helped to enhance social–ecological resilience at different scales. Policies for resettlement and adaptation to environmental change must be developed with indigenous communities based on local knowledge and institutions.     

Landslide triggers along volcanic rock slopes in eastern Sicily (Italy)

A new dataset of landslides, occurred in a tectonically active region, has been analysed in order to understand the causes of the slope instability. The landslides we have dealt with took place along the volcanic rock cliff of S. Caterina and S. Maria La Scala villages (eastern Sicily, Italy), a densely inhabited area located on the eastern margin of Mt. Etna, where some seismogenic faults, locally named Timpe system, slip during moderate local earthquakes and also move with aseismic creep mechanisms. The results show that landslides are triggered by heavy rainfalls, earthquakes and creep fault episodes. Indeed, they occur along discrete fault segments, exhibiting a combination of both brittle failure, indicated by the earthquake occurrence, and aseismic creep events. The analysis of seismicity occurred on the Timpe fault system has shown that the active Acireale fault, in its southernmost segment, is subject to an aseismic sliding, which increases after the stick–slip motion in the nearby faults. Therefore, aseismic creep seems to concur in the predisposition of a rock to fail, since strains can increase the jointing of rock masses leading to a modification in the slope stability. Understanding the factors concurring to the slope instability is a useful tool for future assessments of the landslide hazard in densely settled areas, located on a volcanic edifice, such as Etna that is slowly sliding seawards, and where active faults, seismicity and heavy rains affect the deeply fractured slopes.     

Terrestrial laser scanner and geomechanical surveys for the rapid evaluation of rock fall susceptibility scenarios

The primary objective of this paper is to present a semiautomatic procedure that, integrated with traditional methods, can be useful for a rapid definition of rock fall susceptibility scenarios with the purpose of civil protection. Due to its morphology (steep slopes and narrow valleys), regional seismicity, and rock mass characteristics, the Nera Valley (Valnerina, Umbria Region, Italy) is characterized by high rock fall risk. With the aim of covering a wide range of features and investigating the main advantages and drawbacks of the proposed approach, data collection (terrestrial laser scanning (TLS) and geomechanical surveys) was carried out at three different slopes. Detailed three-dimensional (3D) models were created to reconstruct the shape and volume of the most unstable blocks, to define the position of the main rock fall source areas, and to precisely distinguish the outcropping materials and the position of the elements at risk for reliable runout analyses. The proposed approach can be useful in supporting proper maintenance and land management programs both in ordinary and in emergency circumstances.     

Comparison of pumping at constant head and at a constant rate for determining the sustainable yield of a well

Determining the yield of a production well remains one of the main problems in hydrogeological studies. Starting from the results of a 3-year-long monitoring of a continuously exploited well functioning at constant head (i.e., at a variable discharge rate), a new pumping style has been examined using numerical models. The objective is to control the impact of pumping on the aquifer in accordance with the principle of sustainability. Different models were developed in a transient state and were calibrated using discharge data of the well during the recession periods. Successively, the trends of the residual outflow from the aquifer system with the well operating at variable discharge and at constant discharge were simulated. The results indicate that the ratio of the volume of water pumped from the well to the volume of residual outflow is a significant indicator of the sustainability of groundwater withdrawals. Modeling confirms that a constant discharge rate can be derived from the information gained through a preliminary production phase of a well at constant head. This approach appears to be particularly useful when the problem is determining the sustainable yield of a single well from aquifers with low hydraulic diffusivity.     

Channelization of a large Alpine river: what is left of its original morphodynamics?

The Adige River drains 12 200 km² of the Eastern Alps and flows for 213 km within this mountain range. Similar to other large rivers in Central Europe, the Adige River was subject to massive channelization works during the 19th century. Thanks to the availability of several historical maps, this river represents a very valuable case study to document the extent to which the morphology of the river changed due to channelization and to understand how much is left of its original morphodynamics. The study was based on the analysis of seven sets of historical maps dating from 1803–1805 to 1915–1927, on geomorphological analysis, on the application of mathematical morphodynamic theories and on the application of bar and channel pattern prediction models. The study concerns 115 km of the main stem and 29 km of its tributaries. In the pre‐channelization conditions, the Adige River presented a prevalence of single‐thread channel planforms. Multi‐thread patterns developed only immediately downstream of the main confluences. During the 19th century, the Adige underwent considerable channel adjustment, consisting of channel narrowing, straightening, and reduction of bars and islands. Multi‐thread and single‐thread reaches evolved through different evolutionary trajectories, considering both the channel width and the bar/vegetation interaction. Bar and channel pattern predictors showed good correspondence with the observed patterns, including the development of multi‐thread morphologies downstream of the confluences. Application of the free‐bar predictor helped to interpret the strong reduction – almost complete loss – of exposed sediment bars after the channelization works, quantifying the riverbed inclination to form alternate bars. This morphological evolution can be observed in other Alpine rivers of similar size and similar massive channelization, therefore, a simplified conceptual model for large rivers subjected to channelization is proposed, showing that a relatively small difference in the engineered channel width may have a strong impact on the river dynamics, specifically on bar formation. Copyright © 2017 John Wiley & Sons, Ltd.     

Analysis of the primary and secondary microseisms in the wavefield of the ambient noise recorded in northern Poland

Seasonal changes of the primary and secondary microseisms were analysed in the wavefield of the ambient noise recorded during the entire 2014 at the “13 BB star” array located in northern Poland, composed of thirteen, symmetrically arranged, broadband seismic stations. To that, spectral analysis, seismic interferometry, surface scalar wind speed distribution, and beamforming were used. Spectral analysis allowed to observe that a splitting of the secondary microseism peak was present in winter and autumn, and that the primary microseism peak was visible in spring, summer and autumn. Using seismic interferometry, the long-term characteristics of the noise wavefield were recognized. The seasonal variations of the secondary microseism source were described by means of the analysis of the surface scalar wind speed for each month. The splitting of the secondary peak was attributed to the interaction of a strong wind blowing from the North Sea with a weak wind blowing from the Baltic Sea. The seasonal variations of the primary microseism peak were characterized through the frequency-domain beamforming. The peak was identified during spring, summer and autumn, when the generated wavefield was coming from the Baltic Sea. The velocity of the wavefield was evaluated within the 2.0–5.0 km/s range. The described mechanism of generation of the microseisms, based on the interaction of the nearby winds, was found to be consistent with the models reported in the literature.