On the initial cluster mass distribution inferred from synthesis models

In this contribution we examine the problem of inferring ages and initial cluster masses from synthesis models at the limit of low-mass clusters (M≤ a few ×10⁴ M_⊙). We show that it is not possible to apply directly synthesis models using standard methods to such clusters, since the basic hypothesis implicit in the models (a fixed proportionality between the number of stars in different evolutionary phases) is not fulfilled due to an insufficient number of stars for a reliable sampling of the stellar initial mass function. The consequence of this incomplete sampling is a non-Gaussian distribution of the mass–luminosity relation for clusters that share the same evolutionary conditions (age, metallicity and stellar initial mass distribution function). We review some tests, that can be performed before the start of the analysis, to estimate if the observed cluster can be analyzed with synthesis models following traditional procedures (like χ ² minimization) or if it is necessary make use of synthesis models in a probabilistic framework. Finally, we show the implications of these results for estimating the low-mass tail in the initial cluster mass distribution function.     

Analysis of groundwater mining in two carbonate aquifers in Sierra de Estepa (SE Spain) based on hydrodynamic and hydrochemical data

The carbonate aquifers of Lora and Mingo form part of the hydrogeological unit of Sierra de Estepa (SE Spain). By means of time series analysis and a 1D numerical groundwater model, groundwater exploitation was quantified and the mean annual recharge in both systems was estimated (2001–2004). During this period, the Lora and Mingo aquifers received an average groundwater recharge of 0.29 × 10⁶ m³/year and 0.14 × 10⁶ m³/year, respectively, whereas an average of 0.34 × 10⁶ m³/year and 0.21 × 10⁶ m³/year, respectively, was extracted. These conditions led to a conspicuous lowering of the water table in both systems. In addition, the analysis of the evolution of the main hydrogeochemical parameters of the groundwater showed that the increased pumping rates produced an increase in total dissolved solids, and chloride and sodium ions in both aquifers. In the case of the Lora aquifer, the only ion that presented decreased levels was nitrate. The results show that groundwater pumping in both aquifers should not exceed the mean annual recharge of 0.29 × 10⁶ m³/year and 0.14 × 10⁶ m³/year in the Lora and Mingo aquifers, respectively. Nevertheless, it would be advisable to reduce pumping rates to below these values in order to restore piezometric levels and improve groundwater quality for different uses in the future.     

Long-term resilience, bush encroachment patterns and local knowledge in a Northeast African savanna

Bush encroachment is a significant phenomenon in savanna environments as it affects wildlife and local livelihoods by preventing new pasture generation. In this article we present a 2000-year record of vegetation change in the Dara range of the Mago National Park, southwestern Ethiopia, an area inhabited by Mursi agro-pastoralists. We use an interdisciplinary approach to understand whether bush encroachment in this area is a recent event or a transitional state of the savanna and describe the local understanding of encroachment as a species-specific process. The vegetation record was obtained from a fossil hyrax midden, a type of sediment already used in Southern Africa but never before in East Africa. Six encroaching phases, led by Capparaceae and Grewia, were found over the last two millennia. The system proved to be resilient, with alternating open and encroached phases, and showed a non-linear response to environmental change, thereby fitting the control theory hypothesis for hysteresis loops. Determining the thresholds conditioning the system's resilience could help to improve savanna management for both local people and National Park authorities.     

Quantification of sediment source contributions in two paired catchments of the Brazilian Pampa using conventional and alternative fingerprinting approaches

The knowledge of the contribution of sediment sources to river networks is a prerequisite to understand the impact of land use change on sediment yield. We calculated the relative contributions of sediment sources in two paired catchments, one with commercial eucalyptus plantations (0.83 km²) and the other with grassland used for livestock farming (1.10 km²), located in the Brazilian Pampa biome, using different combinations of conventional [geochemical (G), radionuclide (R) and stable isotopes and organic matter properties (S)] and alternative tracer properties [spectrocolorimetric visible-based-colour parameters (V)]. Potential sediment sources evaluated were stream channel, natural grassland and oat pasture fields in the grassland catchment, and stream channel, unpaved roads and eucalyptus plantation in the eucalyptus catchment. The results show that the best combination of tracers to discriminate the potential sources was using GSRV tracers in the grassland catchment, and using GSRV, GSV and GS tracers in the eucalyptus catchment. In all these cases, samples were 100% correctly classified in their respective groups. Considering the best tracers results (GSRV) in both catchments, the sediment source contributions estimated in the catchment with eucalyptus plantations was 63, 30 and 7% for stream channel, eucalyptus stands and unpaved roads, respectively. In the grassland catchment, the source contributions to sediment were 84, 14 and 2% for natural grassland, stream channel and oats pasture fields, respectively. The combination of these source apportionment results with the annual sediment loads monitored during a 3-year period demonstrates that commercial eucalyptus plantations supplied approximately 10 times less sediment (0.1 ton ha⁻¹ year⁻¹) than the traditional land uses in this region, that is, 1.0 ton ha⁻¹ year⁻¹ from grassland and 0.3 ton ha⁻¹ year⁻¹ from oats pasture fields. These results demonstrate the potential of combining conventional and alternative approaches to trace sediment sources originating from different land uses in this region. Furthermore, they show that well-managed forest plantations may be less sensitive to erosion than grassland used for intensive livestock farming, which should be taken into account to promote the sustainable use of land in this region of South America.     

Analysis and modeling of slope stability in the Three-Gorges Dam reservoir (China) �� The case of Huangtupo landslide

The water level in the Three Gorges Dam reservoir is expected to change between the elevations of 145 m and 175 m, as a function of the flood control implementation and the intensity of the annual flood. As a matter of fact, the hydraulical and mechanical loadings, related to the water level modifications, will result in alterations in the slope stability conditions. The town of Badong (Hubei), of 20 000 inhabitants, is one of the towns which was submerged by the impoundment of the reservoir. As a consequence, the new town of Badong was constructed on a nearby site which appeared to be partly an unstable site. A part of this site corresponds to an old landslide, the Huangtupo landslide, the base of which had to be submerged by the water of the reservoir. The analysis of the Huangtupo landslide, taking into account various events scenarios, drainage and reinforcement measures and monitoring devices, allows to illustrate the general process implemented all along the reservoir in order to mitigate the landslide hazard.     

Understanding carbon trading: Effects of delegating CO2 responsibility on organizations’ trading behaviour

The establishment of a carbon market assumes that there is an effective means of transforming price information into technical carbon reduction measures. However, empirical evidence reveals that the links between price information and carbon management strategies are far from obvious. To understand how delegating CO₂ responsibility affects CO₂ trading behaviour, this article proposes a neo-institutionalist approach to answering the question of why companies became sellers, buyers or a combination of both during phase I of the European Emissions Trading Scheme (EU ETS). Original data from a survey on companies that participated in this scheme were collected and analysed. It was assumed that the trading scheme offered two ways to delegate decisions regarding emissions trading: decoupling from technical knowledge and financialization (i.e. delegating to financial departments) or coupling using technicalization (i.e. delegating to manufacturing departments). The results support the hypothesis that a company that adopts a decoupling strategy is more likely to buy certificates to fulfil their emissions targets. Adopting a coupling strategy indicates that a company is more likely to become a seller, all else equal. Professional identity is the theoretical basis for this relationship. Delegating carbon management to different departments represents either a stronger coupling or a stronger decoupling from core technological processes.

Policy relevance

The transaction data from phase I of the EU ETS open new questions and possibilities regarding the reasons that drive selling and buying in companies. It is important to look not only at the traditional sources of transaction costs, but rather also at the reasons for these tensions. One important source is the professional education of the people in charge of the EU ETS. Tailored information that directly addresses the different professional backgrounds of managers working in both financial departments and more technical departments might help to lower these types of transaction costs. In today's context, important emitter countries, such as China and Korea, have launched their own emissions markets, copying many aspects of the EU ETS. For the positive development of these markets and as a way of establishing a global emissions market, these new schemes should learn from the EU ETS experience.     

Spartina densiflora demonstrates high tolerance to phenanthrene in soil and reduces it concentration

The present study was conducted to investigate the tolerance of Spartina densiflora to phenanthrene, and to test its ability in phenanthrene dissipation. A glasshouse experiment was designed to investigate the effect of phenanthrene from 0 to 1000 mg kg⁻¹ on growth and photosynthetic apparatus of S. densiflora by measuring chlorophyll fluorescence parameters, gas exchange and photosynthetic pigments. We also performed chemical analysis of plant samples, and determined the concentration of phenanthrene remaining in soil. S. densiflora survived to concentrations as high as 1000 mg kg⁻¹ phenanthrene in soil; in fact, there was no significant difference in RGR among the treatments after 30 days. Otherwise, phenanthrene affected photosynthetic apparatus at 100 and 1000 mg kg⁻¹; thus, the lower Φ_PSII could be explained by the declined photosynthetic pigment concentrations. Soil extraction indicated a more marked rate of phenanthrene disappearance in the soil in the presence of S. densiflora.     

Chronological reconstruction of metal contamination in the Port of Maó (Minorca, Spain)

In this work we discuss the historical record of metals as derived from a sediment core from the Port of Maó (Minorca, Spain), the second natural largest harbour in Europe. The sedimentation rate derived from radionuclide profiles increased by a factor of five since the 1960s due to the urbanisation of the town waterfront. Metal concentrations showed two different trends: (i) Pb and Sn inputs started during the second half of the 19th century and remained relatively high until mid-20th century; and (ii) Ag, Cd, Ni, Zn, Cu and Cr accumulation began in the 1940s, peaking in the late 1970s. The commissioning of a submarine outfall in 1978 reduced metal concentrations in subsequently deposited sediments since, thereafter, urban and industrial wastes have been dumped out of the estuary. This study also shows that evaluating the quality of sediments on the basis of surface concentrations may be misleading.