Models of the millimeter-centimeter spectra of the giant planets

Hitherto Jupiter's spectrum at short millimeter wavelenghts showed a clear discrepancy with model calculations (e.g., G.L. Berge and S. Gulkis, 1976, In Jupiter (T. Gehrels, Ed.), pp. 621–692. Univ. of Arizona Press, Tucson). A similar although less pronounced, discrepancy appears to exist for Uranus and Neptune. One explanation of this discrepancy is that additional absorbers not included in the model calculations are present in the atmosphere. It was suggested that uncertainties in the absorption coefficient of ammonia, especially at millimeter wavelengths, may be responsible for at least part of the discrepancy. A comparison of various model atmosphere calculations with data for all four giant planets is shown. The absorption profile of ammonia at centimeter wavelengths was assumed to be rightly represented by a Ben Reuven line profile, which enabled the derivation of information on the vertical distribution of ammonia in these planets' atmospheres. It appeared that ammonia must be depleted in the upper atmospheres of all four planets by a factor of 4–5 with respect to the solar abundance for Jupiter (and Saturn) and by a factor of 100–200 for Uranus and Neptune. At deeper layers the optical depth is larger, due either to a larger abundance of ammonia or to absorption by the presence of water. Given the vertical ammonia distribution in the atmospheres as derived from the centimeter data, a best fit to the millimeter spectra of all four planets was found by changing the high frequency tail of the ammonium lineshape profile. This, we feel, is legitimate since the profile at millimeter wavelenghts is not or is only poorly known due to the absence of laboratory spectra for ammonia as a trace constituent in an otherwise hydrogen gas. It was found that a line profile which at millimeter wavelenghts more closely resembles a Van Vleck-Weisskopf lineshape than the usually adopted Ben Reuven profile gives a rather satisfactory fit to the data of all four gaseous planets.     

Solar flares through electric current interaction

The fundamental hypothesis by Alfvén and Carlqvist (1967) that solar flares are related to electrical currents in the solar chromosphere and low corona is investigated in the light of modern observations. We confirm the important role of currents in solar flares. There must be tens of such current loops (flux threads) in any flare, and this explains the hierarchy of bursts in flares. We summarize quantitative data on energies, numbers of particles involved and characteristic times. A special case is the high-energy flare: this one may originate in the same way as less energetic ones, but it occurs in regions with higher magnetic field strength. Because of the high particle energies involved their emission seats live only very briefly; hence the area of emission coincides virtually with the seat of the instability. These flares are therefore the best examples for studying the primary instability leading to the flare. Finally, we compare the merits of the original Alfvén-Carlqvist idea (that flares originate by current interruption) with the one that they are due to interaction (reconnection) between two or more fluxthreads. We conclude that a final decision cannot yet be made, although the observed extremely short time constants of flare bursts seem to demand a reconnection-type instability rather than interruption of a circuit.Paper dedicated to Professor Hannes Alfvén on the occasion of his 80th birthday, 30 May 1988.     

Biogeographical drivers of ragweed pollen concentrations in Europe

Theoretical and Applied Climatology - The drivers of spatial variation in ragweed pollen concentrations, contributing to severe allergic rhinitis and asthma, are poorly quantified. We analysed the...     

Impact of ocean acidification on the carbonate sediment budget of a temperate mixed beach

The production of sediments by carbonate-producing ecosystems is an important input for beach sediment budgets in coastal areas where no terrigenous input occurs. Calcifying organisms are a major source of bioclastic carbonate sediment for coastal systems. Increased levels of CO₂ in the atmosphere are leading to an increase in the partial pressure of CO₂ on ocean seawater, causing ocean acidification (OA), with direct consequences for the pH of ocean waters. Most studies of OA focus on its impact on marine ecosystems. The impact of OA on carbonate-producing ecosystems could be to reduce the amount of sediments supplied to temperate coastal systems. The aim of this study was to quantify the effect of the predicted OA on the long-term sediment budget of a temperate Mediterranean mixed carbonate beach and dune system. Based on projections of OA we estimated a fall of about 31% in the present bioclastic carbonate sediment deposition rate, with the biggest decreases seen in the dunes (? 46%). OA is also expected to affect the carbonate sediment reservoirs, increasing the dissolution of CaCO₃and causing net sediment loss from the system (~ 50,000 t century^?1). In the long-term, OA could also play a primary role in the response of these systems to sea-level rise. Indeed, the reduction in the quantity of carbonate sediments provided to the system may affect the speed with which the system is able to adapt to sea-level rise, by increasing wave run-up, and may promote erosion of dunes and subaerial beaches.     

Hypersaline groundwater genesis assessment through a multidisciplinary approach: the case of Pozzo del Sale Spring (southern Italy)

A tool, based on a multidisciplinary field investigation approach for studying the characteristics of a hypersaline spring, was developed and its effectiveness tested on a spring in southern Italy; a preliminary model of the aquifer system at medium and local scale was derived. Hydrologic measurements, vertical electric soundings, and chemical and isotopic (δ¹⁸O, δ²H, ³H) analyses were undertaken, along with microbiological analyses and species identification. These demonstrate the coexistence of hypersaline and fresh water, generating a significant diversification of the groundwater hydrochemical signature. The isotopic signature shows that both types of water have a meteoric origin. Microbial contamination of fecal origin indicates the mixing of hyper- and low- saline water related to local infiltration. The hypersaline groundwater flows in confined horizons within a sequence that is mainly of fractured clays. These horizons are probably concentrated where well-developed fracture network and dissolution openings within evaporitic rocks enhance fluid flow. In a wider context, this study determines that microbiological pollution of saline groundwater may not be detected if using nonhalophilic bacterial indicators such as fecal coliforms. Fecal enterococci are better indicators, due to their higher halotolerance.     

Interaction between a dam site and karst springs: The case of Supramonte (Central-East Sardinia, Italy)

Sardinia is one of the Italian regions with the greatest number of dams per inhabitants, almost 60 for a population of only 1.5 million people. Many of these dam sites are located on non-carbonate rocks along the main rivers of the Island and their waters are used for irrigation, industrial, energy supply, drinking and flood regulation purposes.The Pedra 'e Othoni dam on the Cedrino river (Dorgali, Central-East Sardinia) is located along the threshold of the Palaeozoic basement on the Northern border of the Supramonte karst area, where water is forced to flow out of the system through several resurgences, the most famous of which is the Su Gologone vauclusian spring, used for drinking water supply. The other main outflows of the system, Su Tippari and San Pantaleo springs, are at present almost permanently submerged by the high water level of the Pedra 'e Othoni dam. In the near future water will be supplied also to other communities with a possible increase of water taken from the spring.The dam, originally meant to regulate the flooding of Cedrino river but actually used for all sorts of purposes (electricity supply, drinking water, irrigation of farmlands, industrial uses), has a maximum regulation altitude of 103 m a.s.l., only slightly less than a meter below the Su Gologone spring level (103.7 m), and 4 and 9 m respectively above the submerged Su Tippari and San Pantaleo springs.During floods of the Cedrino river, occurring on average twice a year, also the Su Gologone spring becomes submerged by the muddy waters of the lake for a time ranging between a couple of hours up to several days, making water supply impossible.The analysis of the available meteorological and hydrogeological data relative to the December 2004 flood, one of the severest of the past 100 years, suggests that the reservoir is filled in a few days time. Several flooding scenarios have been reconstructed using digital terrain models, showing that backflooding submerges most of the discharge area of the aquifer, having important repercussions also on the inland underground drainage system. The upstream flood prone areas prevalently comprise agricultural lands with some sparse houses, but also highly frequented tourist facilities. Fortunately flooding occurs outside the tourist season, thus limiting risk to a limited number of local inhabitants. Massive discharge at the dam site, instead, determines a more hazardous situation in the Cedrino coastal plain, where population density in low lying areas is much higher. To avoid flooding hazard upstream the water level in the lake should be regulated, keeping it low in the flood prone seasons, and having it filled from the end of the winter in order to have enough water stocked before the beginning of the summer. Discharge at the dam site, instead, should be done cautiously, preventing severe flooding of the coastal Cedrino plain.     

Mineralogical and geochemical characterisation of open-air tailing and waste-rock dumps from the Libiola Fe-Cu sulphide mine (Eastern Liguria,Italy)

Active acid mine drainage (AMD) processes at the Libiola Fe-Cu sulphides mine are mainly triggered by water–rock interaction occurring within open-air tailing and waste-rock dumps. These processes are mainly controlled by exposure to weathering agents, the grain size of the dumped materials, and by the quantity of sulphides, the sulphide types, and their mode of occurrence. Due to these factors, several paragenetic stages of evolution have been recognised at different depths at different sites and within the same site. The dump samples were investigated with mineralogical (reflected- and transmitted-light optical microscopy, XRPD, and SEM-EDS) and geochemical (ICP-AES, Leco) techniques. The AMD evaluation of the tailing and waste-rock samples was performed by calculating the Maximum Potential Acidity, the Acid Neutralising Capacity, (and the Net Acid Producing Potential. The results allowed us to demonstrate that the open-air tailings had already superseded their AMD apex and are now practically inert material composed mainly of stable goethite ± lepidocrocite ± hematite assemblages. On the contrary, the sulphide-rich waste rocks still have a strong potential to produce long term AMD, causing the acidification of circulating waters and the release of several hazardous elements.     

Multivariate analysis of contamination in the mining district of Linares (Jaén, Spain)

Historically, a significant level of mining activity has taken place in the batholite-related metalogenic enclave of Linares (Jaén province, Spain), associated with Pb–Ag, Cu, Zn and Fe sulphides and Ba sulphate mineralization, though mining here has now been abandoned. Additionally, the area features a significant amount of urban, industrial and agricultural activities. These considerations, taken together, explain the need to assess the levels of concentration of trace elements and to determine their relationship with geogenic and anthropogenic factors. For geochemical characterisation of the soil, the region has been divided into 126 grid squares with an area of 1 km². For each grid square, 32 trace elements have been analysed. Elemental concentrations of Cu, Pb, Zn, As and Mn have been included in statistical analyses. According to the reference levels established by the Regional Government (Junta de Andalucía), soils in a large part of the study area require amendment applications. The comparison of the mean content for each grid square with the reference levels reveals a significant degree of contamination of the soil by Cu (719 mg kg⁻¹), Pb (22,964 mg kg⁻¹) and As (100 mg kg⁻¹) in those grid squares affected by metallurgic activities. By means of factor analysis, four scores have been identified which together account for 80% of the variance observed. The first score is highly correlated with the logarithms of the variables Fe, Th, La, Ti, Al, Na, K, Zr, Y, Nb, Be and Sc. It is a “natural” factor that indicates the type of soil matrix (fundamentally granites and, to a lesser degree, Triassic materials). The second score shows high correlation with the logarithms of the variables Mo, Cu, Pb, Zn, Ag, Co, Mn, As, Cd, Sb, Ba, W and Sn, and is the “metallization” factor related to the mineralization that has been exploited. The third score is mainly determined by the logarithms of the variables Sr, Ca and Mg. This is a “natural” factor that indicates a type of carbonate soil matrix (Miocene). Finally, the fourth factor groups the logarithms of the variables Ni, V and Cr, elements that are associated with the combustion of fossil fuels. Analysis of the patterns of each of the factors identified enabled achieving a global characterisation of the study area. Cluster analysis of the observations showed there to be five clusters relating to the grid squares, differentiated by lithologies and degrees of contamination. These clusters are used to determine the background of granite and to calculate the anomalous load.