Soil Microbial and Enzyme Activities Response to Pollution Near an Aluminium Smelter

The aim of this research was to assess the impact caused by a long‐term pollution by fluoride and heavy metals in two soils (PS1 and PS2) near an aluminium smelter in Slovakia, on soil microbial biomass C (MBC), basal respiration, metabolic quotient (qCO₂) water‐soluble organic C (WSOC) and enzymes activities involved in the C, N and P biogeochemical cycles. An unpolluted soil was used as control (C0). Results obtained for soil fluoride content reflected a gradient of fluoride exposure in topsoils of contaminated sites. Decreases in microbial and enzymatic activities and in MBC to organic C ratio were found in PS2 site, which is closer to the smelter and exhibited the highest fluoride content. PS1‐soil showed an extreme alkaline pH caused by leaching of waste effluents from the smelter dumping site, higher contents of Zn, Cu, Pb and Cd, significantly larger MBC, qCO₂ and catalase and urease activities, and much larger basal respiration and dehydrogenase activity than PS2 and C0‐soil. Phosphatase, β‐glucosidase and BAA‐protease were negatively correlated with WSOC, basal respiration and dehydrogenase activity, and showed some degree of inhibition in polluted sites. These results may indicate different responses of microbial communities to ecosystem disturbances, caused by the drastic changes in soil's physicochemical properties as result of the long‐term emissions of fly ash with high levels of contaminants that are still affecting soil microbial and enzymatic activities.     

Origin of the color in cobalt-doped quartz

Synthetic Co-doped quartz was grown hydrothermally in steel autoclaves at the Technological Center of Minas Gerais (CETEC), Brazil. The quartz samples, originally yellow in the as-grown state acquired blue coloration after prolonged heat treatment times at 500°C near the alpha–beta transition temperature. UV–VIS–NIR absorption spectroscopy shows the characteristic spectra of Co³⁺ before heat treatment. After heat treatment, the optical absorption spectrum is dominated by two split-triplet bands the first in the near infrared region centered at about 6,700 cm⁻¹ (1,490 nm) and the second in the visible spectral range at about 16,900 cm⁻¹ (590 nm). Both split-triplet bands are typical for Co²⁺ ions in tetrahedral coordination environments. From the absence of electron paramagnetic resonance (EPR) spectra, we conclude that the Co²⁺ found in the optical absorption spectra of the blue quartz is not due to an isolated structural site in the quartz lattice. Instead, the blue color is associated with electronic transitions of Co²⁺ in small inclusions in which the Co site has tetrahedral symmetry. The non-observation of polarization-depend optical absorption spectra is also in agreement with this model. The results for Co²⁺ in quartz are different from Co-bearing spinel and staurolite and other silicates like orthopyroxene, olivine, and beryls. The formation process of the color center is discussed.     

Magmatic evolution of the Mantos Blancos copper deposit, Coastal Range of northern Chile: insight from Sr–Nd isotope, geochemical data and silicate melt inclusions

The Mantos Blancos copper deposit (500 Mt at 1.0% Cu) was affected by two superimposed hydrothermal events: (i) phyllic alteration related to a rhyolitic dome emplacement and brecciation at ca 155 Ma; and (ii) potassic, sodic and propylitic alteration at ca 142 Ma, coeval with stocks and sills emplacement of dioritic and granodioritic porphyries, that locally grade upwards into polymictic magmatic hydrothermal breccias. Major hypogene copper sulfide mineralization is related to the second event. A late‐ore mafic dike swarm cross‐cuts all rocks in the deposit. Two types of granodioritic porphyries can be distinguished from petrographic observations and geochemical data: granodiorite porphyry I (GP I) and granodiorite porphyry II (GP II), which resulted from two different trends of magmatic evolution. The concave shape of the rare earth element (REE) distribution pattern together with the weak or absence of negative Eu anomalies in mafic dikes, dioritic and GP I porphyries, suggest hornblende‐dominated fractionation for this magmatic suite. In contrast, distinct negative Eu anomalies and the flat REE patterns suggest plagioclase‐dominated fractionation, at low oxygen fugacity, for the GP II porphyry suite. But shallow mixing and mingling between silicic and dioritic melts are also likely for the formation of the GP II and polymictic breccias, respectively. Sr‐Nd isotopic compositions suggest that the rhyolitic dome rocks were generated from a dominantly crustal source, while the GP I has mantle affinity. The composition of melt inclusions (MI) in quartz crystals from the rhyolitic dome is similar to the bulk composition of their host rock. The MI analyzed in quartz from GP II and in the polymictic magmatic hydrothermal breccia of the deposit are compositionally more evolved than their host rocks. Field, geochemical and petrographic data provided here point to dioritic and siliceous melt interaction as an inducing mechanism for the release of hydrothermal fluids to form the Cu mineralization.     

Factors Affecting <Emphasis Type="Italic">Pisidium amnicum</Emphasis> (Müller, 1774; Bivalvia: Sphaeriidae) Distribution in the River Minho Estuary: Consequences for its Conservation

The bivalve Pisidium amnicum (Müller 1774) is a common species in several European freshwater ecosystems. However, few Iberian watersheds are colonized by this species, and the River Minho estuary is possibly the Iberian aquatic ecosystem with the larger population. In October 2004–2007, investigations on spatial and temporal variations in P. amnicum abundance and biomass were carried out at 16 sites along the River Minho tidal freshwater wetlands. Mean abundance and biomass per site ranged from 0 to 750 ind m⁻² and 0 to 7.42 g AFDW m⁻², respectively. A clear decrease in the spatial distribution, abundance, and biomass was observed during the 4-year assessment. Furthermore, a stepwise multiple regression model showed that organic matter and conductivity explained 50.2% of the variation in P. amnicum abundance (R ² = 0.502, F _{[2, 15]} = 7.569, p = 0.005). Ecological knowledge is essential to the implementation of future conservation plans for P. amnicum, and the results of this study are of paramount importance to identify habitats that should be protected in order to preserve this species and provide scientific reference that may be useful in the development of management and/or restoration plans.     

U�CPb isotopic ages and Hf isotope composition of zircons in Variscan gabbros from central Spain: evidence of variable crustal contamination

Ion microprobe U?CPb analyses of zircons from three gabbroic intrusions from the Spanish Central System (SCS) (Talavera, La Solanilla and Navahermosa) yield Variscan ages (300 to 305?Ma) in agreement with recent studies. Only two zircon crystals from La Solanilla massif gave slightly discordant Paleoproterozoic ages (1,848 and 2,010?Ma). Hf isotope data show a relatively large variation with the juvenile end-members showing ?Hf_i values as high as +3.6 to +6.9 and +1.5 to +2.9 in the Navahermosa and Talavera gabbros, respectively. These positive ?Hf_i values up to +6.9 might represent the composition of the subcontinental mantle which generates these SCS gabbros. This ?Hf_i range is clearly below depleted mantle values suggesting the involvement of enriched mantle components on the origin of these Variscan gabbros, and is consistent with previous whole-rock studies. The presence of zircons with negative ?Hf_i values suggest variable, but significant, crustal contamination of the gabbros, mainly by mixing with coeval granite magmas. Inherited Paleoproterozoic zircons of La Solanilla gabbros have similar trace element composition (e.g. Th/U ratios), but more evolved Hf-isotope signatures than associated Variscan zircons. Similar inherited ages have been recorded in zircons from coeval Variscan granitoids from the Central Iberian Zone. Granitic rocks have Nd model ages (T_DM) predominantly in the range of 1.4 to 1.6?Ga, suggesting a juvenile addition during the Proterozoic. However, Hf crustal model ages of xenocrystic Proterozoic zircons in La Solanilla gabbro indicate the presence of reworked Archean protoliths (T_DM2 model ages of 3.0 to 3.2?Ga) incorporated into the hybridized mafic magma.     

Extension of fast periodic transfer orbits from the Earth–Moon RTBP to the Sun–Earth–Moon Quasi-Bicircular Problem

Starting from 80 families of low-energy fast periodic transfer orbits in the Earth–Moon planar circular Restricted Three Body Problem (RTBP), we obtain by analytical continuation 11 periodic orbits and 25 periodic arcs with similar properties in the Sun–Earth–Moon Quasi-Bicircular Problem (QBCP). A novel and very simple procedure is introduced giving the solar phases at which to attempt continuation. Detailed numerical results for each periodic orbit and arc found are given, including their stability parameters and minimal distances to the Earth and Moon. The periods of these orbits are between 2.5 and 5 synodic months, their energies are among the lowest possible to achieve an Earth–Moon transfer, and they show a diversity of circumlunar trajectories, making them good candidates for missions requiring repeated passages around the Earth and the Moon with close approaches to the last.     

A tidal creek water budget: Estimation of groundwater discharge and overland flow using hydrologic modeling in the Southern Everglades

Taylor Slough is one of the natural freshwater contributors to Florida Bay through a network of microtidal creeks crossing the Everglades Mangrove Ecotone Region (EMER). The EMER ecological function is critical since it mediates freshwater and nutrient inputs and controls the water quality in Eastern Florida Bay. Furthermore, this region is vulnerable to changing hydrodynamics and nutrient loadings as a result of upstream freshwater management practices proposed by the Comprehensive Everglades Restoration Program (CERP), currently the largest wetland restoration project in the USA. Despite the hydrological importance of Taylor Slough in the water budget of Florida Bay, there are no fine scale (∼1 km²) hydrodynamic models of this system that can be utilized as a tool to evaluate potential changes in water flow, salinity, and water quality. Taylor River is one of the major creeks draining Taylor Slough freshwater into Florida Bay. We performed a water budget analysis for the Taylor River area, based on long-term hydrologic data (1999–2007) and supplemented by hydrodynamic modeling using a MIKE FLOOD (DHI, http://dhigroup.com/) model to evaluate groundwater and overland water discharges. The seasonal hydrologic characteristics are very distinctive (average Taylor River wet vs. dry season outflow was 6 to 1 during 1999–2006) with a pronounced interannual variability of flow. The water budget shows a net dominance of through flow in the tidal mixing zone, while local precipitation and evapotranspiration play only a secondary role, at least in the wet season. During the dry season, the tidal flood reaches the upstream boundary of the study area during approximately 80 days per year on average. The groundwater field measurements indicate a mostly upwards-oriented leakage, which possibly equals the evapotranspiration term. The model results suggest a high importance of groundwater contribution to the water salinity in the EMER. The model performance is satisfactory during the dry season where surface flow in the area is confined to the Taylor River channel. The model also provided guidance on the importance of capturing the overland flow component, which enters the area as sheet flow during the rainy season. Overall, the modeling approach is suitable to reach better understanding of the water budget in the mangrove region. However, more detailed field data is needed to ascertain model predictions by further calibrating overland flow parameters.