Changes in benthic communities along a presumed pollution gradient in Vancouver Harbour

Samples of macrobenthic organisms were obtained at seven stations on a presumed pollution gradient from the head of Vancouver Harbour through to outer Howe Sound. Polychaetes (83 apparent species) and molluscs (43 apparent species) were the most abundant faunal groups numerically (44.8 and 47.9%, respectively). Molluscs accounted for most of the biomass (87.9%). The following univariate and multivariate methods were used to investigate structural changes in the benthic communities: ANOVA, Abundance-Biomass Comparisons and related statistics, cluster analysis, multidimensional scaling, and the BIOENV procedure. Most of the analyses divided the seven stations into three groups: Port Moody Arm (Inner Harbour): two stations; Inner and Outer Harbour: four stations, and Gibsons (Howe Sound): one station. Further cause-effect investigations are needed to determine the sensitivity to organic pollution of indicator species identified in the survey. However our data correlating benthic community changes to sediment chemistry suggest the inner harbour was dominated by pollution-tolerant species. Depth and sediment grain size were confounding factors for the interpretations.     

Particulate matter concentrations in a high-quality rubber-tyred metro system: the case study of Turin in Italy

Particulate matter concentrations measured in railway metro systems are consistently higher than at street level (up to an indoor/outdoor ratio equal to 10), with dangerous effects for passenger health. These concentrations are mainly produced both by the mechanical friction and wear processes at the rail-wheel-brake interfaces and by the re-suspension caused by the turbulence generated by the train transit. The literature abounds in case studies dealing with the elevated concentrations and the analysis of the atomic composition of particulate matter as well as the epidemiological studies regarding the effects on human health. By contrast, the problem of reducing particulate matter concentrations was not much discussed. Starting from these considerations, the aim of this research was to investigate the PM concentrations of a “high-quality” metro system equipped with useful devices for reducing these concentrations: rubber-tyred, platform screen doors, an advanced ventilation system and a variable slope of the longitudinal profile. A measurement campaign was performed in the metro of Turin (Italy). Experimental results show that the indoor concentrations are statistically lower than those measured in outdoors; that particulate matter levels are closely correlated to the train frequency; the particulate matter concentrations measured inside trains are lower than the ones measured at station platform. From these results, it is possible to note that particulate matter concentrations measured in a “high-quality” metro system are significantly lower than the ones measured in “traditional” railways. This result is significant and poses the bases for the definition of useful interventions for retrofitting metro systems.     

Late slowdown of the Atlantic Meridional Overturning Circulation during the Last Glacial Inception: New constraints from sedimentary (231Pa/230Th)

Our study gives new constraints on the response of Atlantic Meridional Overturning Circulation (AMOC) export to various forcings during the Last Glacial Inception. The decay corrected excess sedimentary (²³¹Pa/²³⁰Th) activity ratio (hereafter referred to as (Pa/Th)) has been measured over that period in two deep cores from the Western (SU90-11, 44°04′N, 40°01′W, 3645 m) and Eastern (MD01-2446, 39°03′N, 12°37′W, 3547 m) basins of the North Atlantic. Both records display significant changes despite the relatively short half-life of ²³¹Pa (～ 32 kyr) compared to the period we investigate. The (Pa/Th) variability does not correlate to changes in local opal flux normalized to ²³⁰Th. Moreover, the (Pa/Th) profiles display a high degree of coherency with indirect proxies of AMOC activity such as the benthic foraminifera δ¹³C and the mid-latitude summer Sea Surface Temperature in nearby reference cores. These additional pieces of evidence support our interpretation of the (Pa/Th) as reflecting AMOC export. The (Pa/Th) repeatedly underwent rapid changes during the Last Glacial Inception associated with the extension of ice rafted detritus in the North Atlantic, highlighting the control of ice-sheet dynamics through freshwater forcing on AMOC export. AMOC export remains large during periods of ice-sheet growth and its decreases lag the Northern Hemisphere summer insolation forcing. AMOC modulation appears driven by ice-sheet dynamics, itself driven by the seasonal insolation gradient between low and high Northern Hemisphere latitudes and the associated intensity of the meridional oceanic and atmospheric circulation.     

New Insights on Mt. Etna’s Crust and Relationship with the Regional Tectonic Framework from Joint Active and Passive P-Wave Seismic Tomography

In the Central Mediterranean region, the production of chemically diverse volcanic products (e.g., those from Mt. Etna and the Aeolian Islands archipelago) testifies to the complexity of the tectonic and geodynamic setting. Despite the large number of studies that have focused on this area, the relationships among volcanism, tectonics, magma ascent, and geodynamic processes remain poorly understood. We present a tomographic inversion of P-wave velocity using active and passive sources. Seismic signals were recorded using both temporary on-land and ocean bottom seismometers and data from a permanent local seismic network consisting of 267 seismic stations. Active seismic signals were generated using air gun shots mounted on the Spanish Oceanographic Vessel ‘Sarmiento de Gamboa’. Passive seismic sources were obtained from 452 local earthquakes recorded over a 4-month period. In total, 184,797 active P-phase and 11,802 passive P-phase first arrivals were inverted to provide three different velocity models. Our results include the first crustal seismic active tomography for the northern Sicily area, including the Peloritan–southern Calabria region and both the Mt. Etna and Aeolian volcanic environments. The tomographic images provide a detailed and complete regional seismotectonic framework and highlight a spatially heterogeneous tectonic regime, which is consistent with and extends the findings of previous models. One of our most significant results was a tomographic map extending to 14 km depth showing a discontinuity striking roughly NW–SE, extending from the Gulf of Patti to the Ionian Sea, south-east of Capo Taormina, corresponding to the Aeolian–Tindari–Letojanni fault system, a regional deformation belt. Moreover, for the first time, we observed a high-velocity anomaly located in the south-eastern sector of the Mt. Etna region, offshore of the Timpe area, which is compatible with the plumbing system of an ancient shield volcano located offshore of Mt. Etna.     

Line Shapes Emitted from Spiral Structures around Symmetric Orbits of Supermassive Binary Black Holes

Variability of active galactic nuclei is not well understood. One possible explanation is existence of supermassive binary black holes (SMBBH) in their centres. It is expected that major mergers are common in the Universe. It is expected that each supermassive black hole of every galaxy eventually finish as a SMBBH system in the core of newly formed galaxy. Here we model the emission line profiles of active galactic nuclei (AGN) assuming that the flux and emission line shape variations are induced by supermassive binary black hole systems (SMBBH). We assume that the accreting gas inside the circumbinary (CB) disk is photo ionized by mini accretion disk emission around each SMBBH. We calculate variations of emission line flux, shifts and shapes for different parameters of SMBBH orbits. We consider cases with different masses and inclinations for circular orbits and measure the effect to the shape of emission line profiles and flux variability.     

Modelled and measured concentrations of peroxy radicals and nitrate radical in the U.S. Gulf Coast region during TexAQS 2006

Measurements of total peroxy radicals (HO₂?+?RO₂) and nitrate radical (NO₃) were made on the NOAA research vessel R/V?Brown along the U.S. Gulf Coast during the TexAQS 2006 field campaign. The measurements were modelled using a constrained box-model based upon the Master Chemical Mechanism (MCM). The agreement between modelled and measured HO₂?+?RO₂ was typically within ??40% and, in the unpolluted regions, within 30%. The analysis of the model results suggests that the MCM might underestimate the concentrations of some acyl peroxy radicals and other small peroxy radicals. The model underestimated the measurements of NO₃ by 60?C70%, possibly because of rapid heterogeneous uptake of N₂O₅. The MCM model results were used to estimate the composition of the peroxy radical pool and to quantify the role of DMS, isoprene and alkenes in the formation of RO₂ in the different regions. The measurements of HO₂?+?RO₂ and NO₃ were also used to calculate the gas-phase budget of NO₃ and quantify the importance of organic peroxy radicals as NO₃ sinks. RO₂ accounted, on average, for 12?C28% of the total gas-phase NO₃ losses in the unpolluted regions and for 1?C2% of the total gas-phase NO₃ losses in the polluted regions.     

Experimental restoration of a salt marsh with some comments on ecological restoration of coastal vegetated ecosystems in Korea

Since the 1980s, the coastal wetlands in Korea have been rapidly degraded and destroyed mainly due to reclamation and landfills for coastal development. In order to recover damaged coastal environments and to develop wetland restoration technologies, a 4-year study on ecological the restoration of coastal vegetated ecosystems was started in 1998. As one of a series of studies, a small-scale experiment on salt marsh restoration was carried out from April 2000 to August 2001. The experiment was designed to find effective means of ecological restoration through a comparison of the changes in environmental components and species structure between two different experimental plots created using sediment fences, one with and one without small canals. Temporal variation in surface elevation, sedimentary facies, and benthic species were measured seasonally in each plot and in the adjacent natural reference sites. Monthly exposure occurred from 330 cm to mean sea level, which represents the critical tidal level (CTL) at which salt marsh plants colonize. Vegetation, especially Suaeda japonica, colonized the site the following spring and recovered to a similar extent in the natural marshes 16 months later. The sedimentary results indicated that the sediment fences had effects on particle size and sediment accumulation, especially in the plot with small canals. This experiment also showed that tidal height, especially that exceeding the CTL, is an important factor in the recovery of the benthic fauna of salt marshes. From these results, we suggested that designs for the restoration of salt marsh ecosystems must consider the inclusion of a tidal height exceeding CTL, as this may allow reconstruction of the previous natural ecosystem without artificial transplanting.     

Spatial polychaeta habitat potential mapping using probabilistic models

The purpose of this study was to apply probabilistic models to the mapping of the potential polychaeta habitat area in the Hwangdo tidal flat, Korea. Remote sensing techniques were used to construct spatial datasets of ecological environments and field observations were carried out to determine the distribution of macrobenthos. Habitat potential mapping was achieved for two polychaeta species, Prionospio japonica and Prionospio pulchra, and eight control factors relating to the tidal macrobenthos distribution were selected. These included the intertidal digital elevation model (DEM), slope, aspect, tidal exposure duration, distance from tidal channels, tidal channel density, spectral reflectance of the near infrared (NIR) bands and surface sedimentary facies from satellite imagery. The spatial relationships between the polychaeta species and each control factor were calculated using a frequency ratio and weights-of-evidence combined with geographic information system (GIS) data. The species were randomly divided into a training set (70%) to analyze habitat potential using frequency ratio and weights-of-evidence, and a test set (30%) to verify the predicted habitat potential map. The relationships were overlaid to produce a habitat potential map with a polychaeta habitat potential (PHP) index value. These maps were verified by comparing them to surveyed habitat locations such as the verification data set. For the verification results, the frequency ratio model showed prediction accuracies of 77.71% and 74.87% for P. japonica and P. pulchra, respectively, while those for the weights-of-evidence model were 64.05% and 62.95%. Thus, the frequency ratio model provided a more accurate prediction than the weights-of-evidence model. Our data demonstrate that the frequency ratio and weights-of-evidence models based upon GIS analysis are effective for generating habitat potential maps of polychaeta species in a tidal flat. The results of this study can be applied towards conservation and management initiatives for the macrofauna of tidal flats.     

Effect of magnetic field on a shock-induced thermal instability

The effect of a magnetic field on a thermal instability has been studied in a radiatively cooling region behind an interstellar shock of moderate propagation velocity ( 10 km s^–1). It is shown that the presence of a magnetic field of a few microgauss is very effective in preventing the thermal instability from building-up density concentrations. In the absence of the magnetic field, the shock-induced thermal instability will amplify a pre-shock density inhomogeneity by more than an order of magnitude. However, in the field's presence, the amplified density contrast is shown to be only a factor 2. Implications for the trace of a sweeping broom in the Pleiades nebula are discussed.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.     

Weathering processes on the rock surface in natural outcrops: the case of an ancient marble quarry (Belevi, Turkey)

. Weathering and mineralogical processes observed in a marble quarry in Turkey are compared with similar processes occurring on monument surfaces. Patina formations (microstromatolitic, microlaminated, monolayered) as well as destructive processes (mainly biopitting and bioerosion) are associated with microbial colonisation of the rock surfaces and one influenced by microclimatic conditions. Patina stratification is independent of substrate rock, but is affected by the position and orientation of rock surfaces. The different layers formed by mineralisation processes may reflect the seasonality of climatic events and the consequent colonisation. Bio-deteriorative processes take place mainly when the climatic conditions cause the organisms to live below the surface.