The Double Solid Reactant Method for modeling the release of trace elements from dissolving solid phases: I. Outline and limitations

A Double Solid Reactant Method was elaborated from a suggestion of Marini (Geological sequestration of carbon dioxide: Thermodynamics, kinetics, and reaction path modeling. Developments in Geochemistry, Elsevier, Amsterdam, 2007) to simulate the release of trace elements during the progressive dissolution of solid phases. The method is based on the definition, for each dissolving solid, of both an entity whose thermodynamic and kinetic properties are known (either a pure mineral or a solid mixture) and a special reactant, that is, a material of known stoichiometry and unknown thermodynamic and kinetic properties. The special reactant is utilised to take into account the concentrations of trace elements in the dissolving solid phase. In this communication, the influence of several trace elements on the ΔG _f ^o, ΔG _r ^o and log K of the minerals considered by Lelli et al. (Environ Geol, 2007) and Accornero and Marini (Geobasi, 2007a; Proceedings of IMWA symposium, Cagliari, 27–31 May 2007b) was evaluated assuming ideal mixing in the solid state. These effects were found to be negligible for albite and the leucite–latitic glass, limited for muscovites and chlorites, and slightly more important for apatites. These influences become progressively higher with increasing concentration of trace elements in these minerals. Based on these deviations in thermodynamic parameters, special reactants should not include oxide components with molar fractions higher than 0.003. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.

High‐resolution evolution of terrigenous sediment yields in the Provence Basin during the last 6 Ma: relation with climate and tectonics

Basin‐wide correlation of Messinian units and Plio‐Quaternary chronostratigraphic markers (5.3 Ma, 2.6 Ma, 0.9 Ma and 0.45 Ma), the mapping of total sediment thickness and the determination of overall sedimentary volumes enabled us to provide a high‐resolution quantitative history of sediment volumes for the last 6 Ma along the Gulf of Lions margin. The results point to (i) a dramatic increase in terrigenous sediment input during the Messinian Salinity Crisis. This increased sedimentation reflects enhanced regional fluvial erosion related to the dramatic fall of Mediterranean base‐level. Stronger weathering due to a regional wetter climate probably also increased erosional fluxes. (ii) A sediment input three times higher during the Plio‐Quaternary compared to the Miocene seems in agreement with published measurements from World's ocean. However, the timing of this increase being uncertain, it implies that the trigger(s) also remain(s) uncertain. (iii) A decrease in detrital volume around 2.6 Ma is attributed to a regional change in the drainage pattern of rivers in the northwestern Alps. (iv) This study also highlights the Mid‐Pleistocene Revolution around 0.9 Ma, which resulted in an almost doubling of sediment input in the Provencal Basin.     

Sustainable urban drainage systems: examining the potential for green infrastructure-based stormwater management for Sub-Saharan cities

Green infrastructure (GI)-based approaches to urban drainage such as sustainable urban drainage systems (SUDS) could provide Sub-Saharan cities with an opportunity to address projected climate change impacts and existing deficits in their drainage infrastructure, even more so due to the synergies between an enhanced green infrastructure stock and sustainable urban development. The objective of this paper was to assess the theoretical value of using green infrastructure for stormwater management as an alternative and supplement to conventional pipe-based stormwater management systems. A SWOT analysis is performed to assess the potential that SUDS hold if adopted and implemented in Sub-Saharan cities. This analysis is based on a review of sustainable stormwater management as well as urban planning and governance literature. Results show that despite seemingly significant barriers to the adoption of SUDS in Sub-Saharan cities such as low prioritization on the urban agenda and lack of data among others, the concept may hold valuable potential for flood risk reduction, even more so due to its multi-functionality and synergies with urban agriculture, amenity and water supply. In the light of the existing threats and weaknesses, it is recommended that GI-based SUDS may be best approached initially as experiments at a local community scale.     

Mt. Etna volcano high-resolution topography: airborne LiDAR modelling validated by GPS data

High-resolution digital topography is essential for land management and planning in any type of territory as well as the reproduction of the Earth surface in a geocoded digital format that allows several Digital Earth applications. In a volcanic environment, Digital Elevation Models are a valid reference for multi-temporal analyses aimed to observe frequent changes of a volcano edifice and for the relative detailed morphological and structural analyses. For the first time, a DTM (Digital Terrain Model) and a DSM (Digital Surface Model) covering the entire Mt. Etna volcano (Italy) derived from the same airborne Light Detection and Ranging (LiDAR) are here presented. More than 250 million 3D LiDAR points have been processed to distinguish ground elements from natural and anthropic features. The end product is the highly accurate representation of Mt. Etna landscape (DSM) and ground topography (DTM) dated 2005. Both models have a high spatial resolution of 2?m and cover an area of 620?km². The DTM has been validated by GPS ground control points. The vertical accuracy has been evaluated, resulting in a root-mean-square-error of ±?0.24?m. The DTM is available as electronic supplement and represents a valid support for various scientific studies.     

On Conditions of Phytoplankton Blooms in the Coastal Waters of the North-Western East/Japan Sea

Seasonal changes of abundance of the main phytoplankton groups of species (diatoms, dinoflagellates, chrysophytes, small flagellates and cryptophytes) and a set of environmental parameters were investigated in coastal and preestuarine waters of Peter the Great Bay (East/Japan Sea) in May-October of 1998 and 1999. Three periods of mass development were revealed: spring, summer and autumn blooms, with successive change of species. The conditions favourable for each group of species were determined. Driving mechanisms of the succession include nutrients transport through seasonal pycnocline by turbulent mixing, terrestrial nutrients supply by monsoon floods, nutrients supply by upwellings, and light control by the thickness of upper mixed layer. Summer succession could be explained by a simple SST-MLD diagram similar to Pingree S-kh diagram with sea surface temperature as indicator of stratification (S) and mixed layer depth as indicator of light availability (kh).     

Characterization of the proteinaceous matter in marine aerosols

Marine aerosols play a dominant role in the transfer of oceanic material to the atmosphere. Most marine aerosol originates when air bubbles burst at the sea surface ejecting material from the sea surface microlayer and bubble surface layers into the air. Concentrations of chemical compounds in these surface layers often differ from their concentrations in bulk water. We examined the enrichment of aerosols with proteinaceous matter and attempted to characterize the physical nature and sources of this matter. We measured concentrations of dissolved free (DFAA), dissolved combined (DCAA), and particulate (PAA) amino acids, transparent stainable particles (TSP), and bacteria and virus-like particles as carriers of protein, in natural and simulated aerosols. We also evaluated D/L ratios certain amino acids in all amino acid fractions.DFAA and DCAA enriched the aerosols we sampled by 1.2–20 times compared to bulk seawater; PAA enrichment was usually higher (up to 50-fold). Aerosols contained particles typical of seawater, e.g., microorganisms, organic debris, inorganic particles with adsorbed organic matter, but also a large number of semitransparent gel-like particles, which all contained amino acids. Some of these particles were probably scavenged from bulk water, but new particles produced as bubbles burst at the surface comprised at least 10% of total proteinaceous matter in the aerosol. D/L ratios of certain amino acid suggested that the particles were most likely made from dissolved polymers secreted by phytoplankton that were concentrated on bubble surfaces and in the microlayer. Examination with Alcian Blue (a dye that targets carbohydrates) and Coomassie Blue (a dye that targets proteins) showed that most TSP in the aerosols contained both proteins and polysaccharides. Microorganisms enriched the aerosols by up to two orders of magnitude, but contributed less than 4% to the total protein pool.     

Lunar fortnightly modulation of tidal mixing near Kashevarov Bank, Sea of Okhotsk, and its impacts on biota and sea ice

Here we examine the consequences of strong tidal mixing on spatial and temporal distributions of biota and sea ice above Kashevarov Bank, Sea of Okhotsk, using data from field surveys (hydrography, pressure gauge and current meter moorings, and bio-acoustic soundings) and remote sensing (NOAA AVHRR). Fortnightly variations in the amplitude of diurnal tidal currents, primarily resulting from the K₁–O₁ interaction, are shown to dominate water motion over the bank. These currents (with maximum velocities 2 m s⁻¹) create a sharp tidally-mixed front that separates well-mixed water above the bank from stratified water along its flanks. Such mixing draws water upward from the cold dichothermal layer (100–150 m) into the surface layer, and thus serves to ventilate the intermediate layers of the Sea of Okhotsk. In summer, fortnightly modulation of the tidal mixing creates temporal variations in water column stratification, a critical factor in the joint supply of nutrients and light required to sustain phytoplankton growth. As such, chlorophyll-a and oxygen values vary in response to the fortnightly cycle, and zooplankton likewise form dense aggregations within the tidally-mixed front in response to the phytoplankton production. It is further noted that the brood cycle of dominant zooplankton species on the bank matches the fortnightly modulation of the tidal currents. In winter, tidal mixing draws relatively warm water upward from mid-depth to maintain a polynya that cyclically opens and closes in response to fortnightly variation in vertical heat flux.     

Intensive sampling of iodine and nutrient speciation in naturally eutrophicated anchialine pond (Rogoznica Lake) during spring and summer seasons

A study of inorganic iodine speciation in the water column of a naturally eutrophicated anchialine pond (Rogoznica Lake, East Adriatic Coast) was conducted in a period between April and July 2004 to obtain information how close the inorganic iodine system is to that of inorganic nutrients during spring, when phytoplankton activity is at maximum, and how the system changes up to summer, when highly reducible redox-conditions prevail in deep water.     

The Chelyabinsk meteorite: Thermal history and variable shock effects recorded by the 40Ar-39Ar system

We studied three lithologies (light and dark chondritic and impact melt rock) differing in shock stage from the LL5 chondrite Chelyabinsk. Using the ⁴⁰Ar-³⁹Ar dating technique, we identified low- and high-temperature reservoirs within all samples, ascribed to K-bearing oligoclase feldspar and shock-induced jadeite–feldspar glass assemblages in melt veins, respectively. Trapped argon components had variable ⁴⁰Ar/³⁶Ar ratios even within low- and high-temperature reservoirs of individual samples. Correcting for trapped argon revealed a lithology-specific response of the K-Ar system to shock metamorphism, thereby defining two distinct impact events affecting the Chelyabinsk parent asteroid (1) an intense impact event ~1.7 ± 0.1 Ga ago formed the light–dark-structured and impact-veined Chelyabinsk breccia. Such a one-stage breccia formation is consistent with petrological observations and was recorded by the strongly shocked lithologies (dark and impact melt) where a significant fraction of oligoclase feldspar was transformed into jadeite and feldspathic glass; and (2) a young reset event ~30 Ma ago particularly affected the light lithology due to its low argon retentivity, while the more retentive shock-induced phases were more resistant against thermal reset. Trapped argon with ⁴⁰Ar/³⁶Ar ratios up to 1900 was likely incorporated during impact-induced events on the parent body, and mixed with terrestrial atmospheric argon contamination. Had it not been identified via isochrons based on high-resolution argon extraction, several geochronologically meaningless ages would have been deduced.