Double-layer structure in the boundary layer over the baltic sea

Double-layered structures found over the Baltic Sea are investigated using radiosoundings and lidar measurements. Situations with double-layer structures are also simulated with the regional model REMO in a realistic manner. The double layer consists of two adjacent well-mixed layers, with a sharp inversion in between.Results from radiosoundings show that the double-layer structure over the Baltic Sea mainly occurs during the autumn with thermally unstable stratification near the surface. The structure is present in about 50 % of the radiosoundings performed during autumn. The presence of the double-layer structure cannot be related to any specific wind direction, wind speed or sea surface temperature.The lidar measurements give a more continuous picture of the time evolution of the double-layer structure, and show that the top of the lower layer is not a rigid lid for vertical transport. Two possible explanations of the double-layer structure are given, (i) the structure is caused by `advection' of land boundary-layer air over the convective marine boundary layer or, (ii) by development of Sc clouds in weak frontal zones connected to low pressure systems. Also the forming of Cu clouds is found to be important for the development of a double-layer structure.     

Transmission electron microscopy applied to fluid inclusion investigations

The transmission electron microscope (TEM) allows a detailed characterization of textural and chemical features of fluid inclusions (shape, inner compositions and inner textures), at a resolution higher than that attainable with an optical microscope (OM). TEM investigation indicates that most fluid inclusions appear as perfectly euhedral negative crystals, with variable shape (from prismatic to equant) and size (typically from <0.02 to 0.15 μm). Inner texture (fluid phase/melt distribution) and composition are variable as well. Different kinds of negative crystals may coexist in the same trail of inclusions, possibly indicating locally variable trapping conditions.

A critical feature, revealed by TEM, is that inclusions are often connected to structural defects (in particular, to dislocation arrays), which are undetected by optical microscopy. The identification of these hidden nanostructures should be taken into account for the correct petrological interpretation of microthermometric results, particularly when controversial data have been obtained. In fact, these nanostructures may represent a possible path for fluid phase leakage, thus modifying the original composition and/or density of the inclusions.     

Magnetostratigraphy and paleomagnetism of early and middle Miocene synorogenic strata: basement partitioning and minor block rotation in Argentine broken foreland

Magnetostratigraphic and paleomagnetic studies on early Andean synorogenic strata (Del Crestón Fm.), in the Famatina Belt (28.7°S, 67.5°W) clarify details of chronology that permit calculation of sedimentation rates within the broken foreland of west Argentina. The Del Crestón Fm represents the first record of broken foreland sedimentation within the southern Central Andean belt and the earliest retroarc volcanic rocks exposed several hundred kilometers from the trench. Twenty-five out of 49 sites collected along the succession presented a primary remanence, as determined through positive fold and reversal tests. Correlation of the local magnetic polarity section with the global polarity time scale indicates that the sedimentation of Del Crestón Fm started at ~16.7 Ma and continued until ~14.5 Ma. The youngest strata are represented by conglomerates bearing abundant Lower Paleozoic granite boulders indicating unroofing of the crystalline basement within the NW Sierras Pampeanas. This result supports the hypothesis of an early broken foreland stage at these latitudes of the Andes, with involvement of the basement in deformation and coeval retroarc volcanism, common attributes of flat-subduction regimes. A mean site paleomagnetic direction of Dec: 6.3°, Inc: ?43.6° (α95: 8.0°, N = 24) confirm our earlier intrepretation that the central part of the Famatina Belt within the Sierras Pampeanas did not undergo large vertical axes rotations since the Middle Miocene.     

Uptake of petroleum hydrocarbons by the Blue Mussel (Mytilus edulis L.) after Experimental Oiling and High Pressure, Hot Water Shore cleaning

High pressure, hot water shore cleaning after an oil spill will release high concentrations of petroleum hydrocarbons to ambient marine ecosystems. The immediate increase of hydrocarbons observed in blue mussels, Mytilus edulis, went from background concentrations of 40 μg/g to 657 μg/g and 533 μg/g at a distance of 3 and 8m respectively from the shore. After two weeks the accumulated oil had decreased by 20–45 %. In comparison natural surf and ice cleaning of shores will only produce a small increase in hydrocarbon concentrations. We recommend that high pressure, hot water cleaning is not used in areas where no special bird or wild life protection is needed.     

Removal of Volatile Organic Compounds in Vertical Flow Filters: Predictions from Reactive Transport Modeling

Vertical flow filters are containers filled with porous medium that are recharged from top and drained at the bottom, and are operated at partly saturated conditions. They have recently been suggested as treatment technology for groundwater containing volatile organic compounds (VOCs). Numerical reactive transport simulations were performed to investigate the relevance of different filter operation modes on biodegradation and/or volatilization of the contaminants and to evaluate the potential limitation of such remediation mean due to volatile emissions. On the basis of the data from a pilot‐scale vertical flow filter intermittently fed with domestic waste water, model predictions on the system’s performance for the treatment of contaminated groundwater were derived. These simulations considered the transport and aerobic degradation of ammonium and two VOCs, benzene and methyl tertiary butyl ether (MTBE). In addition, the advective‐diffusive gas‐phase transport of volatile compounds as well as oxygen was simulated. Model predictions addressed the influence of depth and frequency of the intermittent groundwater injection, degradation rate kinetics, and the composition of the filter material. Simulation results show that for unfavorable operation conditions significant VOC emissions have to be considered and that operation modes limiting VOC emissions may limit aerobic biodegradation. However, a suitable combination of injection depth and composition of the filter material does facilitate high biodegradation rates while only little VOC emissions take place. Using such optimized operation modes would allow using vertical flow filter systems as remediation technology suitable for groundwater contaminated with volatile compounds.     

Modelling inorganic aluminium with WHAM in environmental monitoring

Due to the varying toxicity of different Al species, information about Al concentration and speciation is important when assessing water quality. Modelling Al speciation can support operational monitoring programmes where Al speciation is not measured directly. Modelling also makes it possible to retroactively speciate older samples where laboratory fractionation was not undertaken. Organic-rich waters are a particular challenge for both laboratory analysis and models. This paper presents the modelling of Al speciation in Swedish surface waters using the Windermere Humic Acid Model (WHAM). The model was calibrated with data from operational monitoring, the Swedish national survey of lakes and rivers, and covers a broad spectrum of physical and chemical conditions. Calibration was undertaken by varying the amount of DOC active in binding Al. A sensitivity analysis identified the minimum parameters required as model input variables primarily to be total Al, organic C, pH, F⁻, and secondly Fe, Ca and Mg. The observed and modelled Ali had no significant differences (Spearman rank, p < 0.01), however, lake samples modelled better than rivers. Samples were placed in the correct toxicological category in 89–95% of the cases. The importance of the size of the calibration data set was assessed, and reducing the calibration data set resulted in poorer correlations, but had little impact on the toxicological placement. Overall, the modelling gave satisfactory results from samples covering a broad spectrum of physical and chemical conditions. This indicates the potential value of WHAM as a tool in operational monitoring of surface waters.     

Patterns and Levels of Organochlorines (DDTs, PCBs, non-ortho PCBs and PCDD/Fs) in Male Harbour Porpoises (Phocoena phocoena) from the Baltic Sea, the Kattegat-Skagerrak Seas and the West Coast of Norway

Patterns and levels of chlorinated aromatic contaminants (DDTs, PCBs, non-ortho PCBs and PCDD/Fs) in blubber tissue were compared among six sample groups of male harbour porpoises (Phocoena phocoena) from the Baltic Sea, the Kattegat-Skagerrak Seas and the west coast of Norway. A principal component and classification analysis showed that mature harbour porpoises from the Baltic had significantly different contaminant patterns than animals from the Kattegat-Skagerrak and Norway. ANOVAs showed that mature porpoises from the Baltic had higher levels of ΣPCB and several individual PCBs and PCDD/Fs than the Kattegat-Skagerrak and the Norwegian samples and higher ΣDDT than the Norwegian. A comparison between immature porpoises showed that Baltic animals had higher levels of ΣPCDD/F than the corresponding sample from the Kattegat-Skagerrak. The levels of ΣDDT, ΣPCB and Σnon-ortho PCB were significantly higher in animals collected during 1978–81 compared to animals collected in 1988–90 indicating a temporal decline of these organochlorines in the Kattegat-Skagerrak Seas. The contaminant levels recorded in the Baltic Sea are a serious cause for concern and could have management implications for the already threatened harbour porpoises in this area.     

Mobility of trace elements between the river water,the sediments,and the pore water of Las Catonas Stream,Buenos Aires Province,Argentina

The composition of river water, sediments, and pore waters (down to 30 cm below the bed) of Las Catonas Stream was studied to analyze the distribution of trace elements in a peri-urban site. The Las Catonas Stream is one of the main tributaries of Reconquista River, a highly polluted water course in the Buenos Aires Province, Argentina. The semi-consolidated Quaternary sediments of the Luján Formation are the main source of sediments for Las Catonas Stream. The coarse-grained fraction in the sediments is mainly composed of tosca (calcretes), intraclasts, bone fragments, glass shards, quartz, and aggregates of fine-grained sediments together with considerably amounts of vegetal remains. The clay minerals are illite, illite–smectite, smectite, and kaolinite. For the clay-sized fraction, the external surface area values are mostly between 70 and 110 m²g^?1, although the fraction at 15 cm below the bottom of the river shows a lower surface area of 12 m²g^?1. The N₂ adsorption–desorption isotherms at 77 K for this sample display a behavior indicative of non-porous or macroporous material, whereas the samples above and below present a typical behavior of mesoporous materials with pores between parallel plates (slit-shaped). As, Cr, Cu, and Cd concentrations increase down to 15 cm depth in the sediments, where the highest trace element and total organic carbon (TOC) concentrations were found, and then decrease toward the bottom of the core. Except for As, the levels of the other heavy metals show higher concentration in surficial waters than in pore waters. Distribution coefficients between the sediments, pore water, and surficial water phases indicate that As is released from the sediments to the pore and surficial waters. Cu content strongly correlates with TOC (mainly from vegetal remains), suggesting that this element is mainly bound to the organic phase.     

Seasonal dynamics of zooplankton in Lake Huetzalin, Xochimilco (Mexico City, Mexico)

We quantified the seasonal changes in the zooplankton abundances collected from the Huetzalin Lake (Mexico City, Mexico) for two years (February 2003–January 2004 and then March 2005–February 2006). Selected physicochemical variables (Secchi depth, temperature, pH, conductivity, dissolved oxygen, phosphorus, nitrogen, carbon and chlorophyll a concentration) were also measured at the time of zooplankton collection. The data on zooplankton abundances and the physicochemical variables were subjected to multiple correlation analysis and we also derived Shannon–Wiener species diversity index. Secchi depth ranged from 9 to 65 cm. Generally the lake was alkaline (pH 7–12). The conductivity ranged from 500–1000 mS cm⁻¹, while the mean water temperature was 20.5 °C. Dissolved oxygen levels were generally >3 mg L⁻¹ and were higher in the winter than warmer months. Nitrates (90–95 μg L⁻¹) and phosphates (.2–.5 mg L⁻¹) indicated that the water was eutrophic. Chlorophyll a levels ranged from 143 to 696 μg L⁻¹ during the study period. The zooplankton community was dominated by rotifers (46 species), followed by cladocerans (9 species) and there were only two copepod species. The dominant rotifer species were Brachionus angularis, Brachionus calyciflorus, Brachionus havanaensis, Brachionus quadridentatus, Lecane bulla and Polyarthra vulgaris. Rare rotifer species in Lake Huetzalin were Lecane ohioensis, Dicranophorus forcipatus, Lecane pyriformis, Lindia torulosa, Pleurotrocha petromyzon and Brachionus durgae. Highest densities (occasional peaks of 400 ind L⁻¹) of B. quadridentatus occurred between April and December, while B. havanaensis reached peak densities, during June to October. B. calyciflorus reached densities higher than 1240 ind L⁻¹ during May–September. Cladoceran and copepod densities in Lake Huetzalin were much lower than that of the rotifers. This study confirmed the earlier findings that Xochimilco system of canals is dominated by rotifers and the crustacean zooplankton have much lower abundances possibly due to predation from fish.