Quantitative Evaluation of Water Deposited By Dew on Monuments

Samples of White and Green Carrara marble, and three types oflimestone and brick exposed in the field vertically and horizontally were used to evaluate condensationon monuments during clear sky nights. Experiments in a simulation chamber under controlledconditions led to a general equation for the actual amount of water deposited on a surface by dew.This is determined by: How much and for how long the surface temperature falls below the dew point,the moisture content in the air and the ventilation. On clear nights, the condensation on buildingstructures facing the sky may reach some 0.2 kg m^-2 (or 0.2 mm), whereas condensation on verticalsurfaces is very small. Computation of the seasonal trend of night-time condensationshowed that the maximum amount of water condensed per night occurs in the autumn, with the moreabundant concentration of moisture in the air. The total amount of water condensed per month isfound to be a maximum in the summer-autumn period. Morning condensationfor the thermal inertia of monuments is also relevant, and has been calculated to reach the same order of magnitude as thenocturnal dew. A detailed analysis of the temperature and mixing ratio profiles near a condensingsurface has shown two different situations. In still air, the two profiles follow an exponentiallaw and the thermal and the concentration layers lie within a few tens of millimetres. Inthe presence of turbulence, the thickness of these two layers is dramatically reduced. In still air, infront of a vertical, chilly surface, the deposition rate of air pollutants by thermophoresis and/orStefan flow is increased by 3 or 4 times in comparison with a horizontal surface. In the presence ofturbulence, the thickness of the thermal and concentration layers was dramatically reduced, makingthese two kinds of deposition much faster.     

Advances and Practices on the Research,Prevention and Control of Land Subsidence in Coastal Cities

Land subsidence severely threatens most of the coastal plains around the world where high productive industrial and agricultural activities and urban centers are concentrated. Coastal subsidence damages infrastructures and exacerbates the effect of the sea-level rise at regional scale. Although it is a well-known process, there is still much more to be improved on the monitoring, mapping and modeling of ground movements, as well as the understanding of controlling mechanisms. The International G...     

Shock effects in plagioclase feldspar from the Mistastin Lake impact structure,Canada

Shock metamorphism, caused by hypervelocity impact, is a poorly understood process in feldspar due to the complexity of the crystal structure, the relative ease of weathering, and chemical variations, making optical studies of shocked feldspars challenging. Understanding shock metamorphism in feldspars, and plagioclase in particular, is vital for understanding the history of Earth's moon, Mars, and many other planetary bodies. We present here a comprehensive study of shock effects in andesine and labradorite from the Mistastin Lake impact structure, Labrador, Canada. Samples from a range of different settings were studied, from in situ central uplift materials to clasts from various breccias and impact melt rocks. Evidence of shock metamorphism includes undulose extinction, offset twins, kinked twins, alternate twin deformation, and partial to complete transformation to diaplectic plagioclase glass. In some cases, isotropization of alternating twin lamellae was observed. Planar deformation features (PDFs) are notably absent in the plagioclase, even when present in neighboring quartz grains. It is notable that various microlites, twin planes, and compositionally different lamellae could easily be mistaken for PDFs and so care must be taken. A pseudomorphous zeolite phase (levyne‐Ca) was identified as a replacement mineral of diaplectic feldspar glass in some samples, which could, in some instances, also be potentially mistaken for PDFs. We suggest that the lack of PDFs in plagioclase could be due to a combination of structural controls relating to the crystal structure of different feldspars and/or the presence of existing planes of weakness in the form of twin and cleavage planes.     

Impacts of maintenance channel dredging in a northern Adriatic coastal lagoon. I: Effects on sediment properties,contamination and toxicity

Conservation and management of coastal lagoons envisage direct human intervention. To prevent siltation and to preserve the hydrodynamics features of the lagoon system, the inner channels undergo regular maintenance dredging.     

The crystal chemistry of lithium and Fe3+ in synthetic orthopyroxene

Lithian ferrian enstatite with Li₂O = 1.39 wt% and Fe₂O₃ 7.54 wt% was synthesised in the (MgO–Li₂O–FeO–SiO₂–H₂O) system at P = 0.3 GPa, T = 1,000°C, fO₂ = +2 Pbca, and a = 18.2113(7), b = 8.8172(3), c = 5.2050(2) Å, V = 835.79(9) Å³. The composition of the orthopyroxene was determined combining EMP, LA-ICP-MS and single-crystal XRD analysis, yielding the unit formula ^M2(Mg_0.59Fe _0.21 ²⁺ Li_0.20) ^M1(Mg_0.74Fe _0.20 ³⁺ Fe _0.06 ²⁺ ) Si₂O₆. Structure refinements done on crystals obtained from synthesis runs with variable Mg-content show that the orthopyroxene is virtually constant in composition and hence in structure, whereas coexisting clinopyroxenes occurring both as individual grains or thin rims around the orthopyroxene crystals have variable amounts of Li, Fe³⁺ and Mg contents. Structure refinement shows that Li is ordered at the M2 site and Fe³⁺ is ordered at the M1 site of the orthopyroxene, whereas Mg (and Fe²⁺) distributes over both octahedral sites. The main geometrical variations observed for Li-rich samples are actually due to the presence of Fe³⁺, which affects significantly the geometry of the M1 site; changes in the geometry of the M2 site due to the lower coordination of Li are likely to affect both the degree and the kinetics of the non-convergent Fe²⁺-Mg ordering process in octahedral sites.     

Hyperspectral mapping of alteration assemblages within a hydrothermal vug at the Haughton impact structure,Canada

Meteorite impacts on Earth and Mars can generate hydrothermal systems that alter the primary mineralogies of rocks and provide suitable environments for microbial colonization. We investigate a calcite–marcasite‐bearing vug at the ~23 km diameter Haughton impact structure, Devon Island, Nunavut, Canada, using imaging spectroscopy of the outcrop in the field (0.65–1.1 μm) and samples in the laboratory (0.4–2.5 μm), point spectroscopy (0.35–2.5 μm), major element chemistry, and X‐ray diffraction analyses. The mineral assemblages mapped at the outcrop include marcasite; marcasite with minor gypsum and jarosite; fibroferrite and copiapite with minor gypsum and melanterite; gypsum, Fe³⁺ oxides, and jarosite; and calcite, gypsum, clay, microcline, and quartz. Hyperspectral mapping of alteration phases shows spatial patterns that illuminate changes in alteration conditions and formation of specific mineral phases. Marcasite formed from the postimpact hydrothermal system under reducing conditions, while subsequent weathering oxidized the marcasite at low temperatures and water/rock ratios. The acidic fluids resulting from the oxidation collected on flat‐lying portions of the outcrop, precipitating fibroferrite + copiapite. That assemblage then likely dissolved, and the changing chemistry and pH resulting from interaction with the calcite‐rich host rock formed gypsum‐bearing red coatings. These results have implications for understanding water–rock interactions and habitabilities at this site and on Mars.     

On the criteria to create a susceptibility map to debris flow at a regional scale using Flow-R

Studies on susceptibility to debris flows at regional scale(100-1000 km~2) are important for the protection and management of mountain areas. To reach this objective, routing models, mainly based on land topography, can be used to predict susceptible areas rapidly while necessitating few input data. In this research, Flow-R model is implemented to create the susceptibility map for the debris flow of the Vizze Valley(BZ, North-Eastern Italy; 134 km~2). The analysis considers the model application at local scale for three sub-catchments and then it explores the model upscaling at the regional scale by verifying two methods to generate the source areas of debris-flow initiation. Using data of an extreme event occurred in the Vizze Valley(4 August 2012) and historical information, the modeling verification highlights that the propagation parameters are relatively simple to set in order to obtain correct runout distances. A double DTM filtering-using a threshold for the upslope contributing area(0.1 km~2) and a threshold for the terrain-slope angle(15°)-provides a satisfactory prediction of source areas and susceptibility map within the geological conditions of the Vizze Valley.