Depositional variability of estuarine intertidal sediments and implications for metal distribution: an example from Moreton Bay (Australia)

This study examines the patterns of depositional variability, sediment geochemistry and metal distribution in intertidal areas of Moreton Bay, southeast Queensland, Australia. Recent concern over increasing human impact on the bay has generated the need to obtain evidence on how the disturbance of the depositional setting might affect the natural estuarine environment.Sediment stratigraphy, major, and trace element analyses of sediment cores show that the sedimentation pattern is unique to each intertidal site. Disturbed Pb and Cs activity profiles of some of the cores indicate that sediment reworking occurs across the intertidal flats up to a depth of at least 80cm. With some notable exceptions, an accurate geochronology of the surface sediments could not be established due to low Pb activities and sediment mixing. Thus, an increase in Pb, Zn and Cu towards the surface sediments observed at various sites is attributed to both anthropogenic contribution following the rapid urban development in the last century and to post-depositional diagenetic processes, bioturbation and sediment re-suspension induced by tides, storms or floods. Sediment cores are representative only of the local sedimentation and may not always allow extensive correlation to larger areas. Vertical profiles of heavy metals reflect the different depositional environment controlled by the complex hydrodynamics of the bay. Local hydrologic, physical, and tidal conditions might induce metals redistribution at different scales. This information is of critical importance in view of sediment remobilization caused by future development such as dredging, intertidal areas reclamation or excavation of new navigational channels

Kinematics of slab tear faults during subduction segementation and implications for Italian magmatism

Tectonic activity in convergent plate boundaries commonly involves backward migration (rollback) of narrow subducting slabs and segmentation of subduction zones through slab tearing. Here we investigate this process in the Italian region by integrating seismic tomography data with spatiotemporal analysis of magmatic rocks and kinematic reconstructions. Seismic tomography results show gaps within the subducting lithosphere, which are interpreted as deep (100–500 km) subvertical tear faults. The development of such tear faults is consistent with proposed kinematic reconstructions, in which different rates of subduction rollback affected different parts of the subduction zone. We further suggest a possible link between the development of tear faults and the occurrence of regional magmatic activity with transitional geochemical signatures between arc type and OIB type, associated with slab tearing and slab breakoff. We conclude that lithospheric-scale tear faults play a fundamental role in the destruction of subduction zones. As such, they should be incorporated into reconstructions of ancient convergent margins, where tear faults are possibly represented by continental lineaments linked with magmatism and mineralization

La disclosure volontaria del modello di business nel prospetto informativo di quotazione: un’analisi comparative

How do companies to be listed actually deal with voluntary disclosure of their business model? Is it true that firms with greater knowledge-based resources and technological innovation endowments have a lower propensity to adopt fully open communication behaviors? This paper aims to identify the voluntary disclosure policies adopted by three Italian companies in their Initial Public Offering (IPO) prospectuses in order to investigate whether any differences may depend on the type of innovation underlying each business model. A series of interviews conducted with the top management made it possible to understand more deeply the business model of each company. Further, a content analysis has been developed to compute a measure of disclosure and to point out the strategic concepts and their relevance. We provide evidence that companies with a business model based on technology-push innovation have a lower propensity to the full disclosure of their intangible components, particularly of those mainly based on knowledge as these are also invisible. Our study adds to the literature of business and financial reporting by focusing on a new object of inquiry, that is the business model. The business model plays an important role in allowing external actors to understand a company’s value, thus companies’ strategic communication should be shaped accordingly. The results suggest the need to address the issue of voluntary disclosure of the business model by first distinguishing “visible” intangible resources from those that are “invisible” (both to financial and competitive markets). The study aims to make a contribution to the ongoing debate on business and financial reporting practice

Low arsenic bioaccessibility by fixation in nanostructured iron (Hydr)oxides: quantitative identification of As-bearing phases

A new analytical protocol was developed to provide quantitative, single-particle identification of arsenic in heterogeneous nanoscale mineral phases in soil samples, with a view to establishing its potential risk to human health. Microscopic techniques enabled quantitative, single-particle identification of As-bearing phases in twenty soil samples collected in a gold mining district with arsenic concentrations in range of 8 to 6354 mg kg. Arsenic is primarily observed in association with iron (hydr) oxides in fine intergrowth with phyllosilicates. Only small quantities of arsenopyrite and ferric arsenate (likely scorodite) particles, common in the local gold mineralization, were identified (e.g., 7 and 9 out, respectively, of app. 74,000 particles analyzed). Within the high-arsenic subgroup, the arsenic concentrations in the particle size fraction below 250μm ranges from 211 to 4304 mg kg. The bioaccessible arsenic in the same size fraction is within 0.86–22 mg kg (0.3–5.0%). Arsenic is trapped in oriented aggregates of crystalline iron (hydr)oxides nanoparticles, and this mechanism accounts for the low As bioaccessibility. The calculated As exposure from soil ingestion is less than 10% of the arsenic Benchmark Dose Lower Limit - BMDL. Therefore, the health risk associated with the ingestion of this geogenic material is considered to be low

Geogenic sources and sinks of trace metals in the Larsemann Hills, East Antarctica: Natural processes and human impact

To evaluate the extent of human impact on a pristine Antarctic environment, natural baseline levels of trace metals have been established in the basement rocks of the Larsemann Hills, East Antarctica. From a mineralogical and geochemical point of view the Larsemann Hills basement is relatively homogeneous, and contains high levels of Pb, Th and U. These may become soluble during the relatively mild Antarctic summer and be transported to lake waters by surface and subsurface melt water. Melt waters may also be locally enriched in V, Cr, Co, Ni, Zn and Sri derived from weathering of metabasite pods. With a few notable exceptions, the trace metal concentrations measured in the Larsemann Hills lake waters can be entirely accounted for by natural processes such as sea spray and surface melt water input. Thus, the amount of trace metals released by weathering of basement lithologies and dispersed into the Larsemann Hills environment, and presumably in similar Antarctic environments, is, in general, not negligible, and may locally be substantial. The Larsemann Hills sediments are coarse-grained and contain minute amounts of clay-size particles, although human activities have contributed to the generation of fine-grained material at the most impacted sites. Irrespective of their origin, these small amounts of fine-grained clastic sediments have a relatively small surface area and charge, and are not as effective metal sinks as the abundant, thick cyanobacterial algal mats that cover the lake floors. Thus, the concentration of trace metals in the Larsemann Hills lake waters is regulated by biological activity and thawing-freezing cycles, rather than by the type and amount of clastic sediment supply. (c) 2005 Elsevier Ltd. All rights reserved

Sampling and single particle analysis for the chemical characterisation of fine atmospheric particulates: a review

To better understand the potential environmental and human health impacts of fine airborne particulate matter (APM), detailed physical and chemical characterisation is required. The only means to accurately distinguish between the multiple compositions in APM is by single particle analysis. A variety of methods and instruments are available, which range from filter-based sample collection for off-line laboratory analysis to on-line instruments that detect the airborne particles and generate size distribution and chemical data in real time. There are many reasons for sampling particulates in the ambient atmosphere and as a consequence, different measurement strategies and sampling devices are used depending on the scientific objectives and subsequent analytical techniques. This review is designed as a guide to some of the techniques available for the sampling and subsequent chemical analysis of individual inorganic particles