A case study on fuel oil contamination in a mangrove swamp in Hong Kong

Mangroves commonly found along tropical and subtropical coastlines are susceptible to oil pollution. In December 2000, around 500 1 m tall Kandelia candel saplings at the age of 3–5 years old located at the foreshore region of Sheung Pak Nai swamp, Hong Kong SAR, were found to be damaged by oil pollution. More than 80% of the saplings were either dead or washed away and leaving less than 5% healthy saplings with dense green leaves. Elevated concentrations of light n-alkanes (ranging from n-C₁₄ to n-C₂₀), pristane and phytane were recorded in surface sediments collected in December 2000. The ratio between light and total n-alkanes was 0.4. The total petroleum hydrocarbons (60–80 μg g⁻¹ TPH) and unresolved complex mixtures (60–70 μg g⁻¹ UCM) were higher than the background values of other mangrove sediments in Hong Kong, which were 40 and 20 μg g⁻¹, respectively. In certain root zone sediments, TPH concentrations were above 1000 μg g⁻¹. These results suggest that surface sediments in Sheung Pak Nai were contaminated by petroleum oil, most likely by illegal discharge of fuel oil which occurred between 1998 and 2002. One year later, in December 2001, unhealthy saplings had recovered and re-grown. The concentrations of TPH and UCM in sediments declined to around 40 μg g⁻¹, pristane and phytane dropped by 80%, and the ratio of light to total n-alkanes was 0.15, suggesting that residual oil in sediments was weathered leading to a remarkable recovery of the unhealthy saplings.     

New encoder–decoder convolutional LSTM neural network architectures for next-day global ionosphere maps forecast

GPS Solutions - In addition to traditional tide gauges, the ground-based global navigation satellite system reflectometry (GNSS-R) that utilizes signal-to-noise ratio data from a single GNSS...     

Asbestos and other fibrous minerals contained in the serpentinites of the Gimigliano-Mount Reventino Unit (Calabria,S-Italy)

Serpentinites are metamorphic rocks with good technological properties and valuable ornamental characteristics, which have been exploited since ancient times. Actually, their use is limited and monitored in several countries worldwide because they can contain fibrous asbestos minerals that may be carcinogenic. Furthermore, certain types of fibrous minerals can be confused with asbestos, and must therefore be carefully investigated. We have investigated the possible presence of the asbestos and non-asbestos fibrous phases contained in serpentinitic rocks in a meta-ophiolitic sequence from the Gimigliano-Mount Reventino Unit (Southern Italy), which had not been previously assessed. The detection and quantification of asbestos and the correct distinction of the fibrous non-asbestos minerals are very important not only from a scientific point of view, but also from a legislative one. This is especially the case for the administrative agencies that have to take decisions with regards to the implementation of public and occupational health protection measures (e.g., in road yards and quarry excavations). As a consequence of this, serpentinitic rock samples have been characterized in detail through X-ray powder diffraction, scanning and transmission electron microscopy combined with energy-dispersive spectrometry, analytical electron microscopy (SEM–EDS and TEM–AEM), differential scanning calorimetry, thermogravimetry and micro-Raman spectroscopy. Two kinds of asbestos and four kinds of non-asbestos fibrous silicates have been detected in the examined samples. In order of decreasing abundance these are polygonal serpentine, chrysotile, fibrous antigorite, tremolite, gedrite and magnesiohornblende. The size, morphology, crystallinity and chemical composition of the fibres were also discussed, in the light of the possible role these properties could play in the carcinogenic effect on human health.     

Geochemical comparison of waters and stream sediments close to abandoned Sb-Au and As-Au mining areas,northern Portugal

Waters from abandoned Sb-Au mining areas have higher Sb (up to 2138 μg L⁻¹), As (up to 1252 μg L⁻¹) and lower Al, Zn, Li, Ni and Co concentrations than those of waters from the As-Au mining area of Banjas, which only contain up to 64 μg L⁻¹ As. In general, Sb occurs mainly as SbO₃⁻ and As H₂AsO₄⁻. In general, waters from old Sb-Au mining areas are contaminated in Sb, As, Al, Fe, Cd, Mn, Ni and NO₂⁻, whereas those from the abandoned As-Au mining area are contaminated in Al, Fe, Mn, Ni, Cd and rarely in NO₂⁻. Waters from the latter area, immediately downstream of mine dumps are also contaminated in As. In stream sediments from Sb-Au and As-Au mining areas, Sb (up to 5488 mg kg⁻¹) and As (up to 235 mg kg⁻¹) show a similar behaviour and are mainly associated with the residual fraction. In most stream sediments, the As and Sb are not associated with the oxidizable fraction, while Fe is associated with organic matter, indicating that sulphides (mainly arsenopyrite and pyrite) and sulphosalts containing those metalloids and metal are weathered. Arsenic and Sb are mainly associated with clay minerals (chlorite and mica; vermiculite in stream sediments from old Sb-Au mining areas) and probably also with insoluble Sb phases of stream sediments. In the most contaminated stream sediments, metalloids are also associated with Fe phases (hematite and goethite, and also lepidocrocite in stream sediments from Banjas). Moreover, the most contaminated stream sediments correspond to the most contaminated waters, reflecting the limited capacity of stream sediments to retain metals and metalloids.     

Stratigraphic evolution of the Triassic–Jurassic succession in the Western Southern Alps (Italy): the record of the two-stage rifting on the distal passive margin of Adria

The Triassic–Lower Jurassic succession of the Southern Alps is characterized by rapid thickness changes, from an average of about 5000 m east of Lago Maggiore to about 500 m in the Western Southern Alps. The stratigraphy reflects the Triassic evolution of the Tethyan Gulf and the Early Jurassic rifting responsible for the Middle Jurassic break‐up of Adria from Europe. The succession of the Western Southern Alps starts with Lower Permian volcanics directly covered by Anisian sandstones. The top of the overlying Ladinian dolostones (300 m) records subaerial exposure and karstification. Locally (Gozzano), Upper Sinemurian sediments cover the Permian volcanics, documenting pre‐Sinemurian erosion. New biostratigraphic data indicate a latest Pliensbachian–Toarcian age for the Jurassic synrift deposits that unconformably cover Ladinian or Sinemurian sediments. Therefore, in the Western Southern Alps, the major rifting stage that directly evolved into the opening of the Penninic Ocean began in the latest Pliensbachian–Toarcian. New data allowed us to refine the evolution of the two previously recognized Jurassic extensional events in the Southern Alps. The youngest extensional event (Western Southern Alps) occurred as tectonic activity decreased in the Lombardy Basin. During the Sinemurian the Gozzano high represents the western shoulder of a rift basin located to the east (Lombardy). This evolution documents a transition from diffuse early rifting (Late Hettangian–Sinemurian), controlled by older discontinuities, to rifting focused along a rift valley close to the Pliensbachian–Toarcian boundary. This younger rift bridges the gap between the Hettangian–Sinemurian diffuse rifting and the Callovian–Bathonian break‐up. The late Pliensbachian–Toarcian rift, which eventually lead to continental break‐up, is interpreted as the major extensional episode in the evolution of the passive margin of Adria. The transition from diffuse to focused extension in the Southern Alps is comparable to the evolution of the Central Austroalpine during the Early Jurassic and of the Central and Northern Atlantic margins.     

Multi-criteria spatial screening and uncertainty analysis applied to direct-use geothermal projects

ABSTRACT

The focus of this work is general methods for prioritization or screening of project sites based on the favorability of multiple spatial criteria. We present a threshold-based transformation of each underlying spatial favorability factor into a continuous scale with a common favorability interpretation across all criteria. We compare several methods of computing site favorability and propagating uncertainty from the data to the favorability metrics. Including uncertainty allows decision makers to determine if seeming differences among sites are significant. We address uncertainty using Taylor series approximations and analytical distributions, which are compared to computationally intensive Monte Carlo simulations. Our methods are applied to siting direct-use geothermal energy projects in the Appalachian Basin, where our knowledge about any particular site is limited, yet sufficient data exist to estimate favorability. We consider four factors that contribute to site favorability: the thermal resource described by the depth to 80°C rock, natural reservoir productivity described by rock permeability and thickness, potential for induced seismicity, and the estimated cost of surface infrastructure for heat distribution. Those factors are combined in three ways. We develop favorability uncertainty propagation and sensitivity analysis methods. All methods are general and can be applied to other multi-criteria spatial screening problems.     

On the contribution of phytoplankton and benthic biofilms to the sediment record of marker pigments in high mountain lakes

This study compares the marker pigment composition in three different lake compartments: the water column; the surface sediment biofilm (0–0.5 cm), where production and main degradation processes take place; and the deep sediment (15–17 cm), where the signal is finally stored and marker pigments are used as a proxy in paleolimnological studies. The aim was to evaluate which marker pigments better record in the sediment the relative contributions of planktonic and benthic production in high mountain lakes, taking into account the differential preservation existing among pigments. A survey of 82 high mountain lakes distributed along the major environmental gradients was carried out in the Pyrenees. Comparison of pigments between the three compartments revealed that both water column and sediment biofilm signals could be distinguished in old sediment layers, despite the observation that some of the most characteristic carotenoids that appeared frequently and in high concentrations in the water column were already less common or even absent from the sediment biofilm. In the shallowest lakes, pigment composition in the sediment biofilm was typical of photosynthetically active communities and their deep sediment samples were characterised by a substitution of fucoxanthin by diatoxanthin as the dominant diatom marker pigment. However, in the deepest lakes the pigment composition of the sediment biofilm and deep sediment was similar, characterised by marker pigments of mainly planktonic algal groups and pheophytins, which are typical pigments of decaying communities. Results are discussed in terms of how pigment source (planktonic or benthic) and pigment type (lability of molecule) interact to shape pigment composition in the sediment record of high mountain lakes.     

Long-period seismic source inversions using global tomographic models

We investigate the effect of laterally varying earth structure on centroid moment tensor inversions using fundamental mode mantle waves. Theoretical seismograms are calculated using a full formulation of surface wave ray theory. Calculations are made using a variety of global tomographic earth models. Results are compared with those obtained using the so-called great-circle approximation, which assumes that phase corrections are given in terms of mean phase slowness along the great circle, and which neglects amplitude effects of heterogeneity. Synthetic tests suggest that even source parameters which fit the data very well may have large errors due to incomplete knowledge of lateral heterogeneity. The method is applied to 31 shallow, large earthquakes. For a given earthquake, the focal mechanisms calculated using different earth models and different forward modelling techniques can significantly vary. We provide a range of selected solutions based on the fit to the data, rather than one single solution. Difficulties in constraining the dip-slip components of the seismic moment tensor often produce overestimates of seismic moment, leading to near vertical dip-slip mechanisms. This happens more commonly for earth models not fitting the data well, confirming that more accurate modelling of lateral heterogeneity can help to constrain the dip-slip components of the seismic moment tensor.     

The management challenge posed by marine dispersal of terrestrial plants in coastal dune systems

Abstract:    Marine dispersal provides a mechanism for introduced plants to invade coastal systems. Regular surveillance is essential for management of marine dispersed weeds. This paper outlines the biological, physical and management dimensions of this coastal issue in New Zealand.