Phase-equilibrium geobarometers for silicic rocks based on rhyolite-MELTS. Part 4: Plagioclase,orthopyroxene, clinopyroxene,glass geobarometer,and application to Mt. Ruapehu,New Zealand

A new phase equilibria geobarometer determines magmatic storage and crystallization conditions, including pressure, temperature, oxygen fugacity (\({f_{{{\text{o}}_2}}}\)), and the presence of a fluid phase for glass-bearing rocks containing the assemblage plagioclase?+?pyroxene(s). This newly developed geobarometer can better constrain crystallization conditions of shallow (<?500 MPa; <~?20 km), glass-bearing andesites to dacites. The geobarometer utilizes rhyolite-MELTS to determine crystallization conditions in natural pumice and scoria samples. The validity of the geobarometer is tested by comparing it to results from experiments. Uncertainties are assessed using Monte Carlo simulations. We apply the geobarometer to the plag?+?opx?+?cpx-bearing system of Mt. Ruapehu, in the southern Taupo Volcanic Zone, New Zealand. The samples from Mt. Ruapehu are tested from ~?5 to ~?400 MPa and from super-liquidus to 90% crystalline (~ 1200 to ~ 700 °C). Mt. Ruapehu serves as a methodological testing ground for the geobarometer, and results from our geobarometer agree with recent Mt. Ruapehu studies. Results show a distribution of crystallization pressures ranging from 50 to 150 MPa (~?2.0 to 5.9 km) for different eruptions, with modes of 110 MPa (~ 4.3 km) and 130 MPa (~ 5.1 km). These are consistent with field interpretations of different eruptive styles based on juvenile clast textures and previous knowledge of the magma plumbing system. Mt. Ruapehu magmas are fluid saturated, with \({f_{{{\text{o}}_2}}}\) of ΔQFM ~ + 1 (NNO).     

Deposition of nanoparticles on school eyeglasses in urban and rural areas:A methodology for a more real assessment of the possible impacts

Because incomplete confirmation is available concerning the influential role of atmosphere contamination on conjunctivitis,myopia,asthma,and allergic rhinitis in Brazil,the focus of the present work is to explore the possible relations among atmosphere contamination and eye problems.Rather that a case study on eye diseases,by way of questionnaires supplemented by the investigation of nanoparticles(NPs)on eyeglasses,the study examines the mechanisms in which NPs and ultra-fine particles are deposited on the glasses of children up to 10 years of age in urban and rural area.The important connection between atmosphere contaminants and individual protection equipment justifies improving indoor school properties in order could protect children’s eyes,particularly in high-pollution/high-particulate areas.     

Antioxidant and biotransformation responses in Liza aurata under environmental mercury exposure - relationship with mercury accumulation and implications for public health

This study was carried out in the Laranjo basin (Ria de Aveiro, Portugal), an area impacted by mercury discharges. Liza aurata oxidative stress and biotransformation responses were assessed in the liver and related to total mercury (Hg_t) concentrations. A seasonal fish survey revealed a sporadic increase in total glutathione (GSH_t) and elevated muscle Hg_t levels, although Hg levels did not exceed the EU regulatory limit. As a complement study, fish were caged for three days both close to the bottom and on the water surface at three locations, and displayed higher Hg_t levels accompanied by increased GSH_t content and catalase activity as well as EROD activity inhibition. The bottom group displayed higher hepatic Hg_t and GSH_t contents compared with the surface group. Globally, both wild and caged fish revealed that the liver accumulates higher Hg_t concentrations than muscle and, thus, better reflects environmental contamination levels. The absence of peroxidative damage in the liver can be attributed to effective detoxification and antioxidant defense.     

Deciphering the weathering processes using environmental mineralogy and geochemistry: Towards an integrated model of laterite and podzol genesis in the Upper Amazon Basin

This article reports major results from collaborative research between France and Brazil on soil and water systems, carried out in the Upper Amazon Basin. It reveals the weathering processes acting in the partly inundated, low elevation plateaus of the Basin, mostly covered by evergreen forest. Our findings are based on geochemical data and mineral spectroscopy that probe the crystal chemistry of Fe and Al in mineral phases (mainly kaolinite, Al- and Fe-(hydr)oxides) of tropical soils (laterites). These techniques reveal crystal alterations in mineral populations of different ages and changes of metal speciation associated with mineral or organic phases. These results provide an integrated model of soil formation and changes (from laterites to podzols) in distinct hydrological compartments of the Amazon landscapes and under altered water regimes.     

Dealing with double vagueness in DEM morphometric analysis

A method is presented to explicitly incorporate spatial and scale vagueness – double vagueness – into geomorphometric analyses. Known limitations of usual practices include using a single fixed set of crisp thresholds for morphometric classification and the imposition of a single arbitrary number of scales of analysis to the entire digital elevation model (DEM). Among the advantages of the proposed method are: fuzzification of morphometric classification rules, scale-dependent adaptive fuzzy set parametrization and an objective definition of maximum scale of analysis on a cell-by-cell basis. The method was applied to several DEMs ranging from the ocean floor to surface landscapes of both Earth and Mars. The result was evaluated with respect to modal morphometric features and to characteristic scales, suggesting a more robust method for deriving both morphometric classifications and terrain attributes. We argue that the method would be preferable to any single-scale crisp approach, at least in the context of preliminary hands-off morphometric analyses of DEMs.     

Particulate matter geochemistry of a highly industrialized region in the Caribbean:Basis for future toxicological studies

Air pollution has become an important issue,especially in Caribbean urban areas,and,particulate matter(PM)emitted by different natural and anthropogenic sources causes environmental and health issues.In this work,we studied the concentrations of PM₁₀ and PM_2.5 sources in an industrial and port urban area in the Caribbean region of Colombia.PM samples were collected within 48-h periods between April and October 2018 by using a Partisol 2000 i-D sampler.Elemental geochemical characterization was performed by X-ray fluorescence(XRF)analysis.Further,ionic species and black carbon(BC)were quantified by ion chromatography and reflectance spectroscopy,respectively.Using the Positive Matrix Factorization(PMF)receptor model,the contributions of PM sources were quantified.The average concentration of PM₁₀ was 46.6±16.2μg/m³,with high concentrations of Cl and Ca.For PM_2.5,the average concentration was 12.0±3.2μg/m³,and the most abundant components were BC,S,and Cl.The receptor model identified five sources for PM₁₀ and PM_2.5.For both fractions,the contributions of marine sea spray,re-suspended soil,and vehicular traffic were observed.In addition,PM_2.5 included two mixed sources were found to be fuel oil combustion with fertilizer industry emissions,and secondary aerosol sources with building construction emissions.Further,PM₁₀ was found to also include building construction emissions with re-suspended soil,and metallurgical industry emissions.These obtained geochemical atmospheric results are important for the implementation of strategies for the continuous improvement of the air quality of the Caribbean region.     

Geochemical study of submicron particulate matter(PM1)in a metropolitan area

Air pollution has become a major problem in urban areas due to increasing industrialization and urbanization.In this study ambient concentrations of PM1 and metal concentrations as well as source contributions were identified and quantified by using Positive Matrix Factorization(PMF)in receptor modeling in the Metropolitan Area of Porto Alegre,Brazil.The PM1 samples were collected on PTFE filters from December 2012 to December 2014 in two sampling sites.Major ion and trace element concentrations were assessed.The average concentrations were 12.8 and 15.2μg/m³ for Canoas and Sapucaia do Sul sites,respectively.Major ion contributions of PM1 were secondary pollutants such as sulfate and nitrate.Trace elements,especially Cu,Pb,Zn,Cd,and Ni also made important contributions which are directly associated with anthropogenic contributions.Our results show significantly higher levels in winter than in summer.Most of the PM1 and the analyzed PM species and elements originated from anthropogenic sources,especially road traffic,combustion processes and industrial activities,which are grouped in 7 major contributing sources.A back-trajectory analysis showed that the long-range transport of pollutants was not relevant in relation to the contribution to PM1 and metal concentrations.This work highlights the importance of urban planning to reduce human health exposure to traffic and industrial emissions,combined with awareness-raising actions for citizens concerning the impact of indoor sources.     

Experimental constraints on rhyolite-MELTS and the Late Bishop Tuff magma body

Thermodynamic models are vital tools to evaluate magma crystallization and storage conditions. Before their results can be used independently, however, they must be verified with controlled experimental data. Here, we use a set of hydrothermal experiments on the Late-erupted Bishop Tuff (LBT) magma to evaluate the rhyolite-MELTS thermodynamic model, a modified calibration of the original MELTS model optimized for crystallization of silicic magmas. Experimental results that are well captured by rhyolite-MELTS include a relatively narrow temperature range separating the crystallization of the first felsic mineral and the onset of the ternary minimum (quartz plus two feldspars), and extensive crystallization over a narrow temperature range once the ternary minimum is reached. The model overestimates temperatures by ~40 °C, a known limitation of rhyolite-MELTS. At pressures below 110 MPa, model and experiments differ in the first felsic phase, suggesting that caution should be exercised when applying the model to very low pressures. Our results indicate that for quartz, sanidine, plagioclase, magnetite, and ilmenite to crystallize in equilibrium from LBT magma, magma must have been stored at ≤740 °C, even when a substantial amount of CO₂ occurs in the coexisting fluid. Such temperatures are in conflict with the hotter temperatures retrieved from magnetite–ilmenite compositions (~785 °C for the sample used in the experiments). Consistent with other recent studies, we suggest that the Fe–Ti oxide phases in the Late Bishop Tuff magma body are not in equilibrium with the other minerals and thus the retrieved temperature and oxygen fugacity do not reflect pre-eruptive storage conditions.     

Determination of reaeration‐rate coefficient by modified tracer gas technique

The modified tracer gas technique is used to determine the reaeration coefficient in six different water bodies of the Itajaí River basin, three with rural land use and three in urban areas. Propane was used as the tracer gas and Rhodamine WT as the conservative tracer, providing information on dilution, mixing and dispersion. Liquefied petroleum gas was used instead of high purity propane, aimed at reducing the costs associated with the field trials. Reaeration‐rate coefficients observed in the field ranged from 25.8 to 367.7 d^?1. Two data sets could be observed where smaller streams had substantially larger coefficients of between 133.1 and 367.7 d^?1, while the larger streams had values ??ranging from 25.8 to 54.5 d^?1. Five empirical equations were evaluated by comparing the values ??obtained in the field. The equations proposed by Tsivolgou and Wallace and Tsivoglou and Neal showed greater adherence to the values ??determined in the tests. Reaeration‐rate coefficients obtained in the field were correlated with the hydrodynamic characteristics of the watercourses, thus establishing a mathematical function through which to obtain estimates for future evaluations. The R² value obtained using this equation was 0.959, indicating a high correlation between the calculated values ??and those estimated in the field. Copyright © 2012 John Wiley & Sons, Ltd.     

Magnetite scavenging and the buoyancy of bubbles in magmas. Part 2: Energetics of crystal-bubble attachment in magmas

The fate of pre-eruptive bubbles depends largely on their buoyancy, which can be strongly modified by the presence of crystals attached to the bubble–melt interface. We define the attachment energy and attachment force as those resulting from the attachment of a crystal to a bubble. The attachment energy is such that (1) attachment of crystals to bubbles is always favored energetically, and (2) oxide minerals attach to bubbles much more strongly than silicates, because the attachment energy is a strong function of the wetting angle. Attaching crystals to bubbles can cause bubble–crystal pairs to become neutrally buoyant. There is a critical bubble radius below which the attachment force will be strong enough to keep the pair together; we show that crystals as large as 1 mm in diameter can form neutrally buoyant pairs. For early erupted Bishop magma, if all magnetite forms neutrally buoyant pairs with gas bubbles, ca. 0.1–0.2 vol% gas can be stored in the magma; 2–3 vol% of gas can be accounted for if all minerals form neutrally buoyant aggregates. These values are an order of magnitude lower than what is inferred from melt inclusions. Hence, both magnetite-free and magnetite-rich bubbles might have existed, but only a very small fraction of them could have been neutrally buoyant. Importantly, an intrinsic association between magnetite crystals and bubbles is expected. However, most magnetite crystals in the early erupted Bishop are free of bubbles; the puzzling conclusion is that nucleation away from crystals is favored over heterogeneous nucleation on crystal substrates. Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users.