Chemical composition of landfill leachate in a karst area with a Mediterranean climate (Marbella, southern Spain)

 Between March 1994 and April 1997, the physical and chemical parameters and chemical composition of the urban solid waste leachate of the Marbella landfill (southern Spain) were determined. The data obtained show an ammonium and sodium chloride and bicarbonate type, a pH>7 and high mineralization, effectively described by the following parameters: Na⁺, K⁺, NH₄ ⁺, Cl^– and alkalinity. The chemical composition depends on the rainfall: in dry years, the mineralization and component concentrations have values as much as double those found in normal rainfall years. After storm events, a major and rapid dilution (within several hours) is seen in the leachate. Received: 28 January 1998 · Accepted: 2 June 1998     

Temperature and precipitation projections for the Antarctic Peninsula over the next two decades: contrasting global and regional climate model simulations

This study presents near future (2020–2044) temperature and precipitation changes over the Antarctic Peninsula under the high-emission scenario (RCP8.5). We make use of historical and projected simulations from 19 global climate models (GCMs) participating in Coupled Model Intercomparison Project phase 5 (CMIP5). We compare and contrast GCMs projections with two groups of regional climate model simulations (RCMs): (1) high resolution (15-km) simulations performed with Polar-WRF model forced with bias-corrected NCAR-CESM1 (NC-CORR) over the Antarctic Peninsula, (2) medium resolution (50-km) simulations of KNMI-RACMO21P forced with EC-EARTH (EC) obtained from the CORDEX-Antarctica. A further comparison of historical simulations (1981–2005) with respect to ERA5 reanalysis is also included for circulation patterns and near-surface temperature climatology. In general, both RCM boundary conditions represent well the main circulation patterns of the historical period. Nonetheless, there are important differences in projections such as a notable deepening and weakening of the Amundsen Sea Low in EC and NC-CORR, respectively. Mean annual near-surface temperatures are projected to increase by about 0.5–1.5 \(^{\circ }\)C across the entire peninsula. Temperature increase is more substantial in autumn and winter (\(\sim \) 2 \(^{\circ }\)C). Following opposite circulation pattern changes, both EC and NC-CORR exhibit different warming rates, indicating a possible continuation of natural decadal variability. Although generally showing similar temperature changes, RCM projections show less warming and a smaller increase in melt days in the Larsen Ice Shelf compared to their respective driving fields. Regarding precipitation, there is a broad agreement among the simulations, indicating an increase in mean annual precipitation (\(\sim \) 5 to 10%). However, RCMs show some notable differences over the Larsen Ice Shelf where total precipitation decreases (for RACMO) and shows a small increase in rain frequency. We conclude that it seems still difficult to get consistent projections from GCMs for the Antarctic Peninsula as depicted in both RCM boundary conditions. In addition, dominant and common changes from the boundary conditions are largely evident in the RCM simulations. We argue that added value of RCM projections is driven by processes shaped by finer local details and different physics schemes that are introduced by RCMs, particularly over the Larsen Ice Shelf.

     

A new approach to the monitoring of deformation on Lanzarote (Canary Islands): an 8-year radar perspective

There was significant eruptive activity on Lanzarote (Canary Islands) in the 18th and 19th centuries, and future activity is a clear likelihood today. The fact that not all of the island is covered by geodetic monitoring prompted the authors to assess the possibility of using SAR interferometry for routine volcanic activity monitoring of the island. This paper presents the results obtained after testing this technique using six radar images acquired by the ERS-1 and ERS-2 satellites during the period 1992-2000. The analysis of these images has confirmed the existence of long-term stability coherence across most of the island: a prerequisite for using SAR interferometry in volcano monitoring. The analysis of 15 (redundant) interferograms allowed us to study both the impact of atmospheric artifacts on Lanzarote and any possible displacements, and to conclude that there has been no displacement greater than 3 cm on the island during the period in question. This result matches those obtained with the geodetic equipment installed on the island. Our results show that the inclusion of SAR interferometry in routine geodetic monitoring, supplementing terrestrial techniques, will clearly improve the chances of detecting any possible deformation, and its broad coverage will enhance the interpretation of any observed anomalies.     

Sensitivity of a Titan ionospheric model to the ion-molecule reaction parameters

Various aspects of ion-molecule reactions for Titan ionospheric chemistry modeling are reviewed in this work: temperature/collision energy effects on reaction rates and, more importantly, on products distributions; differential reactivity of isomers of ions; reactivity of excited states of ions; pathways to the building of complex ions. We evaluate here the extent to which these points affect model predictions. We find that the present limiting factors to model predictivity are the model incompleteness for heavy ion production pathways; the differential reactivity of isomers; and, to a lesser degree, the temperature effects on the branching ratios of ion-molecule reactions. Extensive experimental studies are required to fill these gaps in ion-molecule reactivity knowledge.     

A comparative study of four schemes for groundwater vulnerability mapping in a diffuse flow carbonate aquifer under Mediterranean climatic conditions

This paper shows the results of a comparative study involving application of the vulnerability mapping methods known as AVI, GOD, DRASTIC and EPIK to a pilot carbonate massif in southern Spain, namely the Torremolinos aquifer. The main objectives of the study were to determine which methods are most suitable for diffuse flow carbonate aquifers such as in southern Spain, and to evaluate variations in the degree of vulnerability associated to the rainfall variations that normally occur in a Mediterranean climate. According to three of the above methods, the aquifer is moderately vulnerable, but the AVI method evaluated it as highly vulnerable—this, however, is improbable. The vulnerability maps reflect the great importance of geology-related parameters (mainly those concerned with lithology) and, to a lesser degree, that of the depth of the groundwater table which is related to the rainfall. After this latter parameter, it is possible to distinguish between humid and dry climatic situations; thus, vulnerability increases in a humid year, especially according to the GOD and AVI methods. In conclusion, the GOD method seems the most adequate of the methods applied in this work for vulnerability mapping of diffuse flow carbonate aquifers in the Mediterranean domains.     

Optical constants from 370 nm to 900 nm of Titan tholins produced in a low pressure RF plasma discharge

Determining the optical constants of Titan aerosol analogues, or tholins, has been a major concern for the last three decades because they are essential to constrain the numerical models used to analyze Titan’s observational data (albedo, radiative transfer, haze vertical profile, surface contribution, etc.). Here we present the optical constant characterization of tholins produced with an RF plasma discharge in a (95%N₂–5%CH₄) gas mixture simulating Titan’s main atmospheric composition, and deposited as a thin film on an Al–SiO₂ substrate. The real and imaginary parts, n and k, of the tholin complex refractive index have been determined from 370 nm to 900 nm wavelength using spectroscopic ellipsometry. The values of n decrease from n = 1.64 (at 370 nm) to n = 1.57 (at 900 nm) as well as the values of k which feature two behaviors: an exponential decay from 370 nm to 500 nm, with k = 12.4 × e^?0.018λ (where λ is expressed in nm), followed by a plateau, with k = (1.8 ± 0.2) × 10^?3. The trends observed for the PAMPRE tholins optical constants are compared to those determined for other Titan tholins, as well as to the optical constants of Titan’s aerosols retrieved from observational data.     

Sediment transport measurements with tracers in very low‐energy beaches

This study investigates sediment transport at a very low‐energy backbarrier beach in southern Portugal, from a spring‐to‐neap tide period, during fair‐weather conditions. Rates and directions of transport were determined based on the application of fluorescent tracer techniques. Wind and currents were collected locally, whereas the dominant small and short‐period wind waves were characterized using a morphodynamic modelling system coupling a circulation model, a spectral wave model, and a bottom evolution model, well validated over the study area. For the recorded conditions sediment transport was small and ebb oriented, with daily transport rates below 0.02 m³ day^‐1. Tidal currents (mainly ebb velocities) were found to be the main causative forcing controlling sediment displacements. Transport rates were higher during spring tides, tending towards very small values at neap tides. Results herein reported points towards the distinction between tracer advection and tracer dispersion in this type of environment. Transport by advection was low as a consequence of the prevailing hydrodynamic conditions (H_s < 0.1 m, and max. current velocity of 0.5 m s^‐1) and the tracer adjustment to the transport layer, whereas dispersion was relatively high (few metres per day). Tracer techniques allowed distinguishing the broad picture of transport, but revealed the need for refinement in this type of environments (bi‐directional forcing by ebb and flood cycles). Copyright © 2012 John Wiley & Sons, Ltd.     

Spatio-temporal trends of precipitation,its aggressiveness and concentration,along the Pacific coast of South America (36–49°S)

ABSTRACT

Precipitation is the most critical climatic element that directly affects the availability of water resources. The objective of this study was to describe and discuss spatio-temporal patterns of annual precipitation, its aggressiveness, and its concentration along the southwest coast of South America (36°–49°S) from 1930 to 2006. An annual and multi-decadal analysis was applied to 107 sampling stations distributed throughout this region, using the Mann-Kendall test (MK), and the Sampling Uncertainty Analysis (SUA) coupled with Gumbel probability density function (SUA-Gumbel). The analysis revealed positive but not significant trends in annual precipitation and aggressiveness for the region between 36° and 44°S, at least during the last 50 years of the analysed period. However, a significant decrease in annual precipitation and aggressiveness was observed between 44° and 49°S during the same period. The annual concentration of precipitation became slightly more seasonal in the last 50 years within the entire study area.     

Tide circulation patterns in a coastal lagoon under sea-level rise

This study evaluates the patterns and effects of relative sea-level rise on the tidal circulation of the basin of the Ria Formosa coastal lagoon using a process-based model that is solved on an unstructured mesh. To predict the changes in the lagoon tidal circulation in the year 2100, the model is forced by tides and a static sea level. The bathymetry and the basin geometry are updated in response to sea-level rise for three morphological response scenarios: no bed updating, barrier island rollover, and basin infilling. Model results indicate that sea-level rise (SLR) will change the baseline current velocity patterns inside the lagoon over the ~100-year study period, due to a strong reduction in the area of the intertidal basin. The basin infilling scenario is associated with the most important adjustments of the tidal circulation (i.e., increases in the flood velocities and delays in the ebb tide), together with an increase in the cumulative discharges of the tidal inlets. Under sea-level rise and in the basin infilling scenario, the salt marshes and tidal flats experience increases in the tidal range and current asymmetry. Basin infilling changes the sediment flushing capacity of the lagoon, leading to the attenuation of the flood dominance in the main inlet and the strengthening of the flood dominance in the two secondary inlets. The predictions resulting from these scenarios provide very useful information on the long-term evolution of similar coastal lagoons that experience varying degrees of SLR. This study highlights the need for research focusing on the quantification of the physical and socio-economic impacts of SLR on lagoon systems, thus enabling the development of effective adaptation strategies.