Initial Calibration of the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO)

The Atmospheric Imaging Assembly (AIA) instrument onboard the Solar Dynamics Observatory (SDO) is an array of four normal-incidence reflecting telescopes that image the Sun in ten EUV and UV wavelength channels. We present the initial photometric calibration of AIA, based on preflight measurements of the response of the telescope components. The estimated accuracy is of order 25%, which is consistent with the results of comparisons with full-disk irradiance measurements and spectral models. We also describe the characterization of the instrument performance, including image resolution, alignment, camera-system gain, flat-fielding, and data compression.     

Carbonaceous materials in size-segregated atmospheric aerosols from urban and coastal-rural areas at the Western European Coast

A high-volume cascade impactor, equipped with a PM10 inlet, was used to collect size-segregated aerosol samples during the summer of 2004 at two Portuguese locations: a coastal-rural area (Moitinhos) and an urban area (Oporto). Concentrations of airborne particulate matter (PM), total carbon (TC), organic carbon (OC), elemental carbon (EC), and water-soluble organic carbon (WSOC) were determined for the following particle size ranges: < 0.49, 0.49–0.95, 0.95–3.0, and 3.0–10 µm. The total PM mass concentrations at the urban and coastal-rural sites ranged from 22.8 to 79.6 μg m^− 3 and 19.9 to 28.2 μg m^− 3, respectively, and more than 56% of the total aerosol mass was found in the fractions below 3.0 μm. At both locations the highest concentrations of OC and EC were found in the submicrometer size range. The regional variability for the OC and EC concentrations, with the highest concentrations being found in the urban area, was related to the contribution of local primary sources (mostly traffic emissions). It was also verified an enrichment of the small size particles in WSOC, representing on average 37.3(± 12.4)% and 59.7(± 18.0)% of OC in the very fine aerosol at the coastal-rural and urban areas, respectively. The amount of secondary OC calculated by the minimum OC/EC ratio method indicates that secondary organic aerosol formation was important throughout the study at both sites. The obtained results suggest that long-range transport and favourable summer conditions for photochemical oxidation are key factors determining secondary OC formation in the coastal-rural and urban areas. The ultraviolet absorption properties of the chromophoric constituents of the WSOC fractions were also different among the different particle size ranges and also between the two sampling locations, thus suggesting the strong impact of the diverse emission sources into the composition of the size-segregated organic aerosol.     

Geochemical modeling of arsenic sulfide oxidation kinetics in a mining environment

Arsenic sulfide (AsS (am), As₂S₃ (am), orpiment, and realgar) oxidation rates increase with increasing pH values. The rates of arsenic sulfide oxidation at higher pH values relative to those at pH∼2 are in the range of 26-4478, 3-17, 8-182, and 4-10 times for As₂S₃ (am), orpiment, AsS (am), and realgar, respectively.Numerical simulations of orpiment and realgar oxidation kinetics were conducted using the geochemical reaction path code EQ3/6 to evaluate the effects of variable DO concentrations and mineral reactivity factors on water chemistry evolution during orpiment and realgar oxidation. The results show that total As concentrations increase by ∼1.14 to 13 times and that pH values decrease by ∼0.6 to 4.2 U over a range of mineral reactivity factors from 1% to 50% after 2000 days (5.5 yr). The As release from orpiment and realgar oxidation exceeds the current U.S. National Drinking Water Standard (0.05 ppm) approximately in 200-300 days at the lowest initial dissolved oxygen concentration (3 ppm) and a reactivity factor of 1%. The results of simulations of orpiment oxidation in the presence of albite and calcite show that calcite can act as an effective buffer to the acid water produced from orpiment oxidation within relatively short periods (days/months), but the release of As continues to increase.Pyrite oxidation rates are faster than orpiment and realgar from pH 2.3 to 8; however, pyrite oxidation rates are slower than As₂S₃ (am) and AsS (am) at pH 8. The activation energies of arsenic sulfide oxidation range from 16 to 124 kJ/mol at pH∼8 and temperature 25 to 40°C, and pyrite activation energies are ∼52 to 88 kJ/mol, depending on pH and temperature range. The magnitude of activation energies for both pyrite and arsenic sulfide solids indicates that the oxidation of these minerals is dominated by surface reactions, except for As₂S₃ (am). Low activation energies of As₂S₃ (am) indicate that diffusion may be rate controlling.Limestone is commonly mixed with sulfide minerals in a mining environment to prevent acid water formation. However, the oxidation rates of arsenic sulfides increase as solution pH rises and result in a greater release of As. Furthermore, the lifetimes of carbonate minerals (i.e., calcite, aragonite, and dolomite) are much shorter than those of arsenic sulfide and silicate minerals. Thus, within a geologic frame time, carbonate minerals may not be present to act as a pH buffer for acid mine waters. Additionally, the presence of silicate minerals such as pyroxenes (wollastonite, jadeite, and spodumene) and Ca-feldspars (labradorite, anorthite, and nepheline) may not be important for buffering acid solutions because these minerals dissolve faster than and have shorter lifetimes than sulfide minerals. However, other silicate minerals such as Na and K-feldspars (albite, sanidine, and microcline), quartz, pyroxenes (augite, enstatite, diopsite, and MnSiO₃) that have much longer lifetimes than arsenic sulfide minerals may be present in a system. The results of our modeling of arsenic sulfide mineral oxidation show that these minerals potentially can release significant concentrations of dissolved As to natural waters, and the factors and mechanisms involved in arsenic sulfide oxidation warrant further study.     

Application of Non-Ionic Solid Sorbents (XAD Resins) for the Isolation and Fractionation of Water-Soluble Organic Compounds from Atmospheric Aerosols

A detailed procedure using non-ionic macropourous XAD-8 and XAD-4 resins is presented for the isolation and fractionation of aerosol water-soluble organic compounds (WSOC) from aerosol samples. The procedure entails adsorption of WSOC fraction onto XAD-8 and XAD-4 resins, desalting of the adsorbed organic material with ultra-pure water, elution of the retained organic matter with 40% MeOH solution and freeze-drying. Due to resin’s different properties and to certain hydrophobic/hydrophilic interactions between the resin polymers and the organic matter, two major fractions were obtained; namely the XAD-8 and the XAD-4 eluates. The XAD-8 eluate, which accounts for 55–60% of total aerosol WSOC, is represented by partially acidic compounds with significant hydrophobic moieties. The XAD-4 fraction holds few conjugated systems and a higher content of hydrophilic structures with low molecular size, and accounts for 9% of total WSOC. The isolated WSOC sub-fractions were nearly free from inorganic species, and successful recoveries of organic matter from the resins were accomplished. With this procedure the XAD-8 eluate yields a mixture representative of those WSOC that are highly conjugated compounds in atmospheric aerosols. It also allows a successful characterisation of the organic material by advanced analytical techniques without the interference of inorganic species present in the original sample of atmospheric particles.     

Intense drought and flooding events in the Rio Negro and relation with the tropical Pacific and Atlantic variability modes

The relationship of the hydrological variability of the Rio Negro in Manaus and the dominant large-scale climate variability patterns for the 1902–2007 period is investigated using the quantile method and composite analyses. Variations of the Rio Negro Level (RNL) during its 3-month high (May to July—MJJ) and low (October to December—OND) phases are examined separately. The El Niño (La Niña) related maximum warming (cooling) in the central tropical Pacific during its mature and decaying stages modulates the atmospheric circulation in the tropics and displaces the Walker circulation cell eastward (westward), so that its sinking (rising) branch occurs over western Amazon and causes negative (positive) precipitation anomalies in this region. These anomalous climate conditions occur before the Rio Negro high phase (MJJ) and contribute to reduce (increase) the RNL and lead to a very low (very high) event in the river. On the other hand, the SST variability modes in the tropical Atlantic mainly during the transition from wet to dry season modulate the precipitation variations over western Amazon in OND. The very high events are more frequent after the 1960’s decade and the very low events, before the 1930’s decade. Therefore, the occurrence of these events contains a multidecadal scale variability. The results also indicate that the variations in the rainfall in western Amazon occur up to 9 months in advance and modulate the RNL in Manaus. The results presented here might be useful for monitoring purposes of the RNL.

     

Age and geotectonic setting of Late Neoproterozoic juvenile mafic gneisses and associated paragneisses from the Ribeira belt (SE Brazil) based on geochemistry and Sm–Nd data — Implications on Gondwana assembly

Mafic gneisses and associated paragneisses from the Cabo Frio Tectonic Domain in the southeastern part of the Ribeira Belt, along the coast of Rio de Janeiro State in southeast Brazil, were subjected to a geochemical and Sm–Nd isotope study. Four lithotypes are distinguished: aluminous paragneisses (mainly sillimanite–kyanite–garnet–biotite gneiss), calcsilicate lenses, quartzo–feldspathic metasedimentary gneisses and mafic–ultramafic lenses. The whole-rock major and trace, including rare earth element distributions in the mafic–ultramafic intercalations indicate that derivation from subalkaline basalt/gabbro of tholeiitic affinity with E-MORB signature from a non-subduction environment. These mafic rocks have positive ε_Nd(t) and T_DM of 1.1 Ga. The metasedimentary rocks have negative ε_Nd(t) and T_DM of 1.7 Ga. A Sm–Nd whole rock isochron of mafic rocks yielded an age of 604 ± 38 Ma for the crystallization. This matches with the age of some detrital zircon grains from the paragneisses. The depositional basin, named Buzios–Palmital, was active at least until 620 Ma (age of the youngest detrital zircon) and was subsequently deformed and metamorphosed at ca. 525 Ma (age of metamorphic zircons) during the Buzios Orogeny. It is interpreted as a back arc basin with relation to the 630 Ma magmatic arc of the Oriental Terrane in the Ribeira Belt to the NW. However, after 600 Ma, the Buzios–Palmital basin changed to an active margin setting because the arc collided with the continental margin and the subduction shifted to the back arc environment. By 610 Ma, most of the Brasiliano belts registered collisional events related to multiple convergent blocks. The stress fields and paleocontinent shapes would have allowed the occurrence of extensional areas with not only sedimentary deposition but also ocean floor spreading. Its remnants are preserved in this Brazilian coastal region as an ancient suture, reworked intensively during the Mesozoic rifting events. The reconnaissance of Late Neoproterozoic basins in the Brasiliano–Pan-African belts is of major importance to partially unravel the final amalgamation events of SW Gondwana. Considering that the Buzios–Palmital basin rock units are mostly covered by the marginal Atlantic basins, it is possible that other evidence could be preserved in the coastal regions of SW-Africa and SE-South America.     

Transfer patterns in Phase I of the EU Emissions Trading System: a first reality check based on cluster analysis

In 2005, the world's largest Emissions Trading System (ETS) was introduced in the EU. Economic theory assumes high efficiency of such market-based instruments since companies have the flexibility to trade allowances. However, to date there is a lack of understanding on how companies have participated in the allowance markets. This article uses data on transfers of allowances between 2005 and the end of 2007, published by the EU in the Community Independent Transaction Log (CITL) after a five-year delay. We use cluster analysis to detect patterns in the data and differentiate transfer behaviour. We find that the vast majority of participants (7212 accounts) are rather passive in terms of transfers. Of these, more than half are hardly participating in the market at all, whereas one-third are accounts managed by another account belonging to the parent company. Opposed to that, 143 accounts show more active, but relatively diverse transfer behaviour. We also identify differences in sectoral representations, account types, and primary allocation across the seven clusters. While the passive accounts mostly belong to installations regulated under the EU ETS, the most active accounts are classified as ‘non-regulated account type'.     

The resolved red giant branches of E/S0 galaxies

Formation paradigms for massive galaxies have long centered around two antipodal hypotheses – the monolithic-collapse and the accretion/merger scenarios. Empirical data on the stellar contents of galaxy halos is crucial in order to develop galaxy formation and assembly scenarios which have their root in observations, rather than in numerical simulations. The Hubble Space Telescope (HST) has enabled us to study directly individual stars in the nearby E/S0 galaxies Cen A, NGC 3115, NGC 5102, and NGC 404. We here present and discuss HST single-star photometry in V and I bands. Using color-magnitude diagrams and stellar luminosity functions, we gauge the galaxies' stellar contents. This can be done at more than one position in the halo, but data with deeper limiting magnitudes are desired to quantify the variation of metallicity with galactocentric radius. We here compare the color distributions of red giant stars with stellar isochrones, and we intercompare the galaxies' halo populations, noting that their total absolute V magnitudes cover the range from about –21.5 to –17.5. In the future, we plan to model the stellar metallicity distributions with the aim to constrain chemical enrichment scenarios, a step towards unravelling the evolutionary history of elliptical and lenticular galaxies. This revised version was published online in August 2006 with corrections to the Cover Date.     

Digitization and Scientific Exploitation of the Italian and Vatican Astronomical Plate Archives

There is a widespread interest to digitize the precious information contained in the astronomical plate archives, both for the preservation of their content and for its fast distribution to all interested researchers in order to achieve their better scientific exploitation. This paper presents the first results of our large-scale project to digitize the archive of plates of the Italian Astronomical Observatories and of the Specola Vaticana. Similar systems, composed by commercial flat-bed retro-illuminated scanners plus dedicated personal computers and acquisition and analysis software, have been installed in all participating Institutes. Ad-hoc codes have been developed to acquire the data, to test the suitability of the machines to our scientific needs, and to reduce the digital data in order to extract the astrometric, photometric and spectroscopic content. Two more elements complete the overall project: the provision of high quality BVRI CCD sequences in selected fields with the Campo Imperatore telescopes, and the distribution of the digitized information to all interested researchers via the Web. The methods we have derived in the course of this project have been already applied successfully to plates taken by other Observatories, for instance at Byurakan and at Hamburg.