Remote sensed data for automatic detection of land-use changes due to human activity in support to landslide studies

Slope instability studies appear to recognize a number of potential superficial slide-producing agents, which may be directly detected and monitored with Earth Observation (EO) data. The main objective of this work is to use conventional EO data and automatic techniques for providing land-use change maps useful in landslide prevention. The idea is to use the detection of changes in areas already involved in landslide events as a precursory sign of variations in the equilibrium status of the slope, independently from other natural triggering events, such as rain and seismic events. Attention is focused on man-induced surface changes, such as deforestation, urban expansion and construction of artificial structures. A historical set of 20 multi-temporal Landsat TM images, covering the period 1987–2000, was analyzed using a supervised change detection technique on a test site affected by slope instability phenomena located in the Abruzzo region in Southern Italy. A change image is obtained by comparing year-specific thematic map pairs. It contains useful information not only on the place where a transition occurred, but also on the specific classes involved in the transitions between two different years. The full set of change images is used to extract class-conditional transition probabilities, to evaluate variations in specific class distribution and the total number of changed pixels in time. Four classes and their transitions were considered in the analysis: (1) arboreous land, (2) agricultural land, (3) barren land, and (4) artificial structures. The quantitative analysis of the class-joint transition probability values of some specific class-transitions that may worsen slope stability showed that in an area prone to landslides the probability of landslide re-activation or first activation is higher where changes have occurred. Although based on a limited number of known events, such a result encourages extensive experimentation of the proposed technique on better documented landslide test sites.     

Homogenization of Climate Data: Review and New Perspectives Using Geostatistics

The homogenization of climate data is of major importance because non-climatic factors make data unrepresentative of the actual climate variation, and thus the conclusions of climatic and hydrological studies are potentially biased. A great deal of effort has been made in the last two decades to develop procedures to identify and remove non-climatic inhomogeneities. This paper reviews the characteristics of several widely used procedures and discusses the potential advantages of geostatistical techniques. In a case study, the geostatistical simulation approach is applied to precipitation data from 66 monitoring stations located in the southern region of Portugal (1980–2001). The results from this procedure are then compared with those from three well established statistical tests: the Standard normal homogeneity test (SNHT) for a single break, the Buishand range test, and the Pettit test. Promising results from the case study open new research perspectives on the homogenization of climate time series.     

The ecological consequences of privatisation in romanian agriculture

There have been many changes in the vegetation cover as a result of the development of settlements and agriculture. Every change in the farming system will be reflected in some ways in the vegetation; and some of these changes may be ecologically undesirable. For example erosion may accelerate as a result of cropping and overgrazing on steeply-sloping hill land with thin soils. Several changes were apparent when agriculture was collectivised and a further transformation is now under way as a result of the privatisation of agriculture and the transition to a market economy. The recent changes are outlined, against a background review of the earlier transformations. Although the situation will only become clearer as the transition proceeds it is evident that ecological problems will have to be given a higher priority.     

150 years of anthropogenic metal input in a Biosphere Reserve: the case study of the Cananéia–Iguape coastal system, Southeastern Brazil

The Cananéia–Iguape system consists of a complex of estuarine and lagoonal channels located in the coastal region of southeastern Brazil known as Lagamar, a Biosphere Reserve recognized by the United Nations Educational, Scientific and Cultural Organization (UNESCO) in 1991. The area suffered dramatic environmental changes along the last ca. 150 years initiated by the 1852 opening of an artificial channel, the Valo Grande, connecting the Ribeira de Iguape River to the estuarine system. Due to Au, Ag, Zn, and Pb mining activities that took place in the upstream regions of the Ribeira de Iguape River since the seventeenth century, the system has acted as a final destination of contaminated sediments. Analysis of cores located along the estuarine system revealed a history of contamination, with an increase of anthropogenic metal input between the decades of 1930 and 1990. The anthropogenic influence can be traced in locations as far as 20 km from the mouth of the artificial channel.     

BRAMS model performance for significant event involving Brazilian platform ship

Natural Hazards - After a storm displaced the P-70 platform ship located in Guanabara Bay to the coast on January 30, 2020, a numerical investigation was carried out with the BRAMS (Brazilian...     

Tidal currents and wind waves controlling sediment distribution in a subtidal point bar of the Venice Lagoon (Italy)

The present study aims to improve current understanding of the sedimentation of subtidal point bars, analyzing interaction between tidal currents and waves in shaping a submerged meander bend of the microtidal Venice Lagoon (Italy), and it is based on coupling of sedimentological studies, geophysical analyses and numerical modelling. The Venice Lagoon is characterized by an average depth of about 1·5 m over subtidal platforms and a mean tidal range of about 1·0 m. The morphodynamic evolution of the lagoon is strongly affected by intense seasonal windstorms, which promote the formation of wind waves triggering sediment resuspension and bottom erosion. The study channel is 70 to 100 m wide, it has a radius of curvature of about 260 m and cuts through a permanently submerged subtidal platform. Water depth ranges from 1·0 to 5·0 m below mean sea level on the subtidal platform and channel thalweg, respectively. Different from classical architectural models, the study point‐bar beds do not show sigmoidal geometries, but consist of horizontally‐bedded deposits abruptly overlying clinostratified beds. Sedimentation in the study bar is hypothesized to stem from the interaction between the in‐channel secondary helical flow, as for most meander bends, and wave winnowing of the subaqueous overbank areas. Laterally accreting point‐bar deposits point out that the curvature‐induced helical flow redistributed sediment from the channel thalweg to the bar top and contributed to the development of the ‘classical’ fining‐upward grain size trend. The marked truncation surface, separating clinostratified bar deposits from overlying horizontally‐bedded platform sediments is interpreted here as due to bar top wave‐winnowing, which also possibly promoted bank collapses. In the proposed model, sediments remobilized from bar top and subaqueous overbank areas were transported into the channel, forming peculiar ‘apron‐like’ accumulations, where sand accumulated through avalanching processes and mud settled down from suspension.     

Characterization of a karstic aquifer using magnetic resonance sounding and electrical resistivity tomography: a case-study of Esta?a Lakes (northern Spain)

The geophysical characterization of a previously unstudied endorheic karstic system is presented. The studied area, known as the Esta?a Lakes, is located in the Pyrenean Marginal Sierras, northern Spain. The Esta?a Lakes are a set of natural water ponds on a bedrock of Triassic evaporites, lutites and carbonates. This wetland is included in the Natura 2000 European network of nature protection areas as a “Site of Community Importance”. Two geophysical techniques were used, magnetic resonance sounding (MRS) and electrical resistivity tomography (ERT), to map the subsurface geology and characterize the aquifer layers and the hydraulic links between the aquifers and lakes. The geophysical data were integrated with the surface geology and data from six boreholes. Ten electrical profiles were performed to identify the thickness of the units and lithological changes, whereas the MRS was used to determine the top of the saturated zone. As result, the aquifer in the Esta?a Lakes system and surrounding area has been identified as Middle Triassic carbonates, which does not correspond with the regional aquifer in the area (Upper Cretaceous and Eocene). This work shows the power of geophysical methods in poorly understood and tectonically complex areas in addition to the standard aquifer tests to evaluate hydraulic properties.     

Petrogenesis of the Paleoproterozoic basalt–andesite–rhyolite dyke association in the Carajás region, Amazonian craton

Paleoproterozoic basaltic, andesitic and rhyolitic dykes crosscut the Archaean Carajás basement. Basalts are distinguished into a high and a low TiO₂ group (HTi and LTi), each group consisting of geochemically distinct NE- and NW-trending swarms. The HTi dykes are evolved transitional basalts having essentially EMORB-type geochemistry. The LTi basalts are tholeiites (NE-trending swarm) and high-Al basalts (NW-trending swarm) displaying incompatible trace elements patterns with variably negative Nb anomaly, enrichment in Rb, Ba, K (LILE) and La, Ce and Nd (LREE) and positive Sr anomaly. With respect to orogenic analogues, andesites have lower Al₂O₃, CaO and Ni, higher FeO, LILE, LREE, Nb, Zr and Ti and negative Sr anomaly. Rhyolites have geochemical characteristics comparable with those of A-type granites. At 1.8 Ga, ranges from 0.700 to 0.705 in the HTi basalts and from 0.700 to 0.704 in the LTi group. Andesites define an isochron of 1874±110 Ma (Sr_o=0.7038±0.0010). Rhyolites from Southern and Northern Carajás define two isochrons of 1802±130 Ma (Sr_o=0.7062±0.0046) and 1535±82 Ga (Sr_o=0.7625) respectively, the younger date being interpreted as resetting of the Rb–Sr isotopic system. We propose a petrogenetic model relating LTi basalts with melting of lithospheric mantle metasomatized by acid melts derived from incipient melting of eclogites, representing in turn the subsolidus product of basaltic batches trapped in the mantle. The HTi basalts are explained by melting of the lithospheric mantle containing the complementary residual eclogite. Andesite petrogenesis is consistent with crystal fractionation from a high-Mg andesite parent derived from a mantle source more extensively metasomatized by eclogite-derived melts. Rhyolite composition is consistent with low melting degree of the basement rocks. The basalt–andesite–rhyolite dykes may represent the effects of crustal extension and arching in Carajás, which produced the anorogenic acid to intermediate magmatism (Uatumã group) and affecting a large part of the Amazon craton between 1.85 and 1.7 Ga.     

Apatite Reference Materials for SIMS Microanalysis of Isotopes and Trace Elements

Twelve apatite samples have been tested as secondary ion mass spectrometry (SIMS) reference materials. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analysis shows that the SLAP, NUAN and GR40 apatite gems are internally homogeneous, with most trace element mass fractions having 2 standard deviations (2s) ≤ 2.0%. BR2, BR5, OL2, AFG2 and AFB1, which have U > 63 μg g^-1, ²⁰⁶Pb/²⁰⁴Pb > 283, and homogeneous SIMS U-Pb data, have respective isotope dilution thermal ionisation mass spectrometry (ID-TIMS) ages of 2053.83 ± 0.21 Ma, 2040.34 ± 0.09 Ma, 868.87 ± 0.25 Ma, 478.71 ± 0.22 Ma and 473.25 ± 0.09 Ma. Minor U-Pb heterogeneity exists and accurate SIMS results require correction with the 3D Concordia-constrained common Pb composition. Among the studied samples, AFG2 and BR5 are the most homogeneous U-Pb reference materials. The SIMS sulfur isotopic compositions of eight of the apatites shows they are homogeneous, with 2s for both 10³δ³⁴S and 10³δ³³S < 0.55‰. One apatite, BR96, has Δ³³S = -0.36 ± 0.2‰. The apatite samples have ID-TIMS ⁸⁷Sr/⁸⁶Sr between 0.704214 ± 0.000030 and 0.723134 ± 0.000035.