Search

Abstract Juno has allowed clear, high‐resolution imaging of Io's polar volcanoes using the Jovian Infrared Auroral Mapper (JIRAM) instrument. We have used data from JIRAM's M‐band (4.78 μm) imager from 11 Juno orbits to construct a global map of volcanic flux. This map provides short‐term insight into the spatial distribution of volcanoes and the ways in which high‐ and low‐latitude volcanoes differ. Using spherical harmonic analysis, we quantitatively compare our volcanic flux map to the surface heat flow distribution expected from models of Io's tidal heat deposition (summarized in de Kleer, Park, et al. (2019, https://doi.org/10.26206/d4wc‐6v82). Our observations confirm previously detected systems of bright volcanoes at high latitudes. Our study finds that both poles are comparably active and that the observed flux distribution is inconsistent with an asthenospheric heating model, although the south pole is viewed too infrequently to establish reliable trends.

We investigate the variability of the power emission of Io’s hotspots by using recent Juno/JIRAM infrared observations. The Jovian Infrared Auroral Mapper (JIRAM) is an imaging spectrometer which began observing Jupiter in August 2016. Although observing Jupiter’s moons is not its primary objective, JIRAM can use the frequent opportunities to observe Io (up to once per orbit) to gather infrared images and spectra of its surface. The present study uses the data acquired by JIRAM during the last 2 years, including the location and morphology of Io’s hotspots, and the temporal variability of the total output. A new photometric model for the hotspots and the dayside surface has been developed, which permits us to disentangle the temporal variability from the changes in the observation geometry. While the latitudinal dependence of the power output is not well constrained, low-latitude hotspots show a significantly more intense temporal variability and greater temperature.

Cold molecules provide an excellent platform for quantum information, cold chemistry, and precision measurement. Certain molecules have enhanced sensitivity to beyond standard model physics, such as the electron's electric dipole moment (eEDM). Molecular ions are easily trappable and are therefore particularly attractive for precision measurements where sensitivity scales with interrogation time. Here, we demonstrate a spin precession measurement with second-scale coherence at the quantum projection noise (QPN) limit with hundreds of trapped molecular ions, chosen for their sensitivity to the eEDM rather than their amenability to state control and readout. Orientation-resolved resonant photodissociation allows us to simultaneously measure two quantum states with opposite eEDM sensitivity, reaching the QPN limit and fully exploiting the high count rate and long coherence.

This paper reviews the current understanding of the toxicity of selenium (Se) to terrestrial mammalian and aquatic organisms. Adverse biological effects occur in the case of Se deficiencies, associated with this element having essential biological functions and a narrow window between essentiality and toxicity. Several inorganic species of Se (-2, 0, +4, and +6) and organic species (monomethylated and dimethylated) have been reported in aquatic systems. The toxicity of Se in any given sample depends not only on its speciation and concentration, but also on the concomitant presence of other compounds that may have synergistic or antagonistic effects, affecting the target organism as well, usually spanning 2 or 3 orders of magnitude for inorganic Se species. In aquatic ecosystems, indirect toxic effects, linked to the trophic transfer of excess Se, are usually of much more concern than direct Se toxicity. Studies on the toxicity of selenium nanoparticles indicate the greater toxicity of chemically generated selenium nanoparticles relative to selenium oxyanions for fish and fish embryos while oxyanions of selenium have been found to be more highly toxic to rats as compared to nano-Se. Studies on polymer coated Cd/Se quantum dots suggest significant differences in toxicity of weathered vs. non-weathered QD's as well as a significant role for cadmium with respect to toxicity., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Abiotic processes able to reduce oxidized Se species may have a strong influence on the environmental behavior of selenium since Se toxicity, bioavailability and mobility follow the order Se(-II)0.3), while does not affect significantly the reduction of Se(IV) by H(2)A at low ratios (<0.1). Fe(III) also catalyzes the oxidation of H(2)A but in this case the possible diminution of the reduction rates of Se(IV) by H(2)A are masked by additional processes of adsorption on and coprecipitation by ferric oxyhydroxides, which lower the concentrations of Se(IV)., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

The behavior and toxicity of Cr(III) and Cr(VI) to the green algae Pseudokirchneriella subcapitata and Chlorella kessleri were studied in a standard culture medium (ISO medium) and, for P. subcapitata only, in ultrafiltered natural water enriched with all ISO components (modified ISO medium). In all solutions amended with Cr(III), initial chromium concentrations decreased by 60-90% over 72h (the duration of algal tests) indicating that protocols for testing poorly soluble substances are required to properly evaluate Cr(III) toxicity. After accounting for its behavior in test solutions, chromium(III) was 5-10 times more toxic than Cr(VI) in both media. For P. subcapitata, the average 72h EC50 of Cr(III) in ISO medium was 17.4+/-4.7 microg/L (n=9); lower than corresponding hardness-corrected Continuous Concentration Criteria of the US EPA and well within the range of Cr concentrations found in waters impacted by tannery discharges. These results follow from intrinsic chemical properties of Cr(III) in circumneutral solutions, so that the actual toxicity of Cr(III) to aquatic organisms may be generally underestimated., (Copyright (c) 2010 Elsevier Inc. All rights reserved.)

The analysis of some Italian mineral waters by ICP-MS has revealed errors in the determination of As and Cr in natural effervescent or carbonated waters due to the presence of dissolved inorganic carbon (DIC). This leads to overestimate As and Cr in 1% (v/v) HNO3 acidified samples, analysed within 1-2 h after the acidification. The overestimation of As concentration is caused by matrix interferences producing a signal enhancement due to the presence of dissolved inorganic carbon. This effect is analogous to that observed in the presence of organic carbon and occurs at millimolar DIC levels. The overestimation of Cr concentration is due to the 40Ar12C+ species interfering with 52Cr+ despite the use of the octopole reaction system. The optimization of the He flow in the collision cell can solve the latter problem, but the required increase in the flow rate decreases the sensitivity of the ICP-MS technique. The observed effects in CO2 rich mineral waters and artificial NaHCO3 solutions suggest that 5-10 mM DIC levels may affect the determination of As and Cr concentration in thermal waters, rivers, lakes and groundwaters.

The trophic status classification of coastal waters at the European scale requires the availability of harmonised indicators and procedures. The composite trophic status index (TRIX) provides useful metrics for the assessment of the trophic status of coastal waters. It was originally developed for Italian coastal waters and then applied in many European seas (Adriatic, Tyrrhenian, Baltic, Black and Northern seas). The TRIX index does not fulfil the classification procedure suggested by the WFD for two reasons: (a) it is based on an absolute trophic scale without any normalization to type-specific reference conditions; (b) it makes an ex ante aggregation of biological (Chl-a) and physico-chemical (oxygen, nutrients) quality elements, instead of an ex post integration of separate evaluations of biological and subsequent chemical quality elements. A revisitation of the TRIX index in the light of the European Water Framework Directive (WFD, 2000/60/EC) and new TRIX derived tools are presented in this paper. A number of Italian coastal sites were grouped into different types based on a thorough analysis of their hydro-morphological conditions, and type-specific reference sites were selected. Unscaled TRIX values (UNTRIX) for reference and impacted sites have been calculated and two alternative UNTRIX-based classification procedures are discussed. The proposed procedures, to be validated on a broader scale, provide users with simple tools that give an integrated view of nutrient enrichment and its effects on algal biomass (Chl-a) and on oxygen levels. This trophic evaluation along with phytoplankton indicator species and algal blooms contribute to the comprehensive assessment of phytoplankton, one of the biological quality elements in coastal waters.

The rates of the reduction of Cr(VI) with H2O2 were measured in NaCl solutions as a function of pH (1.5-4.8), temperature (5-40 degrees C), and ionic strength (I = 0.01-2 M) in the presence of an excess of reductant. The rate of Cr(VI) reduction is described by the general expression -d[Cr(VI)]/dt = k2[Cr(VI)](m)[H2O2](n)[H+](z), where m = 1 and n and z are two interdependent variables. The value of n is a function of pH between 2 and 4 (n = (3 x 10(a))/(1 + 10(a)), where a = -0.25 - 0.58pH + 0.26pH2) leveling off at pH < 2 (where n approximately = 1) and pH > 4 (where n approximately = 3). The rates of Cr(VI) reduction are acid-catalyzed, and the kinetic order z varies from about 1.8-0.5 with increasing H2O2 concentration, according to the equation z = 1.85 - 350.1H2O2 (M) which is valid for [H2O2] < 0.004 M. The values of k2 (M(-(n+z)) min(-1)) are given by k2 = k/[H+](z) = k1/[H2O2](n)[H+](z), where k is the overall rate constant (M(-n) min(-1)) and k, is the pseudo-first-order rate constant (min(-1)). The values of k in the pH range 2-4 have been fitted to the equation log k = 2.14pH - 2.81 with sigma = +/- 0.18. The values of k2 are dependent on pH as well. Most of the results with H2O2 < 3 mM are described by log k2 = 2.87pH - 0.55 with sigma = +/- 0.54. Experimental results suggest that the reduction of Cr(VI) to Cr(III) is controlled by the formation of Cr(V) intermediates. Values of k2 and k calculated from the above equations can be used to evaluate the rates of the reaction in acidic solutions under a wide range of experimental conditions, because the rates are independent of ionic strength, temperature, major ions, and micromolar levels of trace metals (Cu2+, Ni2+, Pb2+). The application of this rate law to environmental conditions suggests that this reaction may have a role in acidic solutions (aerosols and fog droplets) in the presence of high micromolar concentrations of H2O2.

Major inputs into the northern Adriatic Sea and critical problems affecting this basin are revised strengthening the need for a thorough knowledge of organic carbon cycling. Results gathered in the context of the PRISMA 2 project by our research group give information on the distribution and composition of organic matter in terms of major biochemical components, molecular weight sizes and biodegradability characteristics. Seasonal accumulation of dissolved organic matter in summer along with an increased role of carbohydrate and colloidal matter (being on average 15-20 and 60-65% of DOC, respectively) and restricted bacterial activity due to P deficiency are all priority subjects to be further investigated.

Fourteen metals (Ca, Mg, Al, Fe, Mn, Ba, As, Cd, Co, Cr, Cu, Ni, Pb and Zn) were monitored over a 2-year period in the waters of the lower Po River. Concentrations in the dissolved and particulate phases were measured, thus constructing a large database on metal variability. The influence of flow and solid transport on dissolved, particulate and total metal concentrations is discussed. In addition to flow rate and solid content, biological processes seem to be one of the main factors affecting concentrations in the dissolved phase, while the inorganic components of solids seem to control metal concentration in suspended matter. Data on partitioning of metals between the dissolved and particulate phases are presented, together with related information on the affinity sequence of metals for the particulate phase, and the influence of solid load on the modes of metal transport.