A novel gas purification system for biologically produced gases

A novel gas purification system employing membrane contactors with dense membranes in the absorption as well as the desorption unit has been tested concerning the separation efficiency of CO₂. The separation efficiency of potassium carbonate (K₂CO₃) promoted by piperazine (PZ) as absorption medium has been tested in the absorption unit. Since the absorbent will be regenerated in the desorption unit, the influence of temperature, sweep flow rate and absorbent type (0.5 M K₂CO₃ and 0.5 M K₂CO₃/0.5 M PZ) on the separation efficiency of CO₂ in the desorption unit has been investigated. Desorption by vacuum has been considered as well.In addition experimental results of the coupling of a bioreactor producing hydrogen by anoxygenic photosynthesis (low and fluctuating product gas flow rates and fluctuating compositions) with a membrane contactor for gas purification are reported. This was done in order to show the applicability of this system to processes producing biogases.     

Sustainability and education for sustainability: An analysis of publications from the last decade

This study analyzes the characteristics of publications on sustainability topics and education for sustainability in the Web of Science (WOS) database during the period ranging from 2005 to 2014. We identified the topics that are being studied within those subjects and other relevant topics. We also analyzed a special edition of the Journal of Cleaner Production on “Higher Education for Sustainable Development: Emerging areas,” published in January, 2014. Our approach was both qualitative and quantitative and aimed at qualifying and quantifying certain variables related to the scientific literature on the broad subject of sustainability. The number of published pieces in the WOS focusing on sustainability issues during the period from 2005 to 2014 was 5,924. In our analysis of the special edition of the Journal of Cleaner Production, we found and analyzed 17 abstracts and full papers. The main results of our survey highlight the education, educational research, environmental sciences, ecology, and engineering areas as including the greatest number of publications. Articles, as opposed to conference proceedings or reviews, accounted for 63% of the published documents, and the year 2013 showed the largest number of publications. Huisingh, Suciu, Katane, and Barth are the most published authors on these topics. Furthermore, management, environmental studies, ecology, and environmental sciences are the “hot topics” with the best search results, meaning articles of impact and high quality. Finally, it should be emphasized that publications on the subject of sustainability appear most often in the sciences.     

Quantifying the effect of wind on internal wave resonance in Lake Villarrica,Chile

Lake Villarrica, located in south central Chile, has a maximum depth of 167 m and a maximum fetch of about 20 km. The lake is monomictic, with a seasonal thermocline located at a depth of approximately 20 m. Field data show the presence of basin-scale internal waves that are forced by daily winds and affected by Coriolis acceleration. A modal linear and non-linear analysis of internal waves has been used, assuming a two-layer system. The numerical simulations show good agreement with the internal wave field observations. The obtained modes were used to study the energy dissipation within the system, which is necessary to control the amplitude growth. Field data and numerical simulations identify (1) the occurrence of a horizontal mode 1 Kelvin wave, with a period of about a day that coincides with the frequency of daily winds, suggesting that this mode of the Kelvin waves is in a resonant state (subject to damping and controlled by frictional effects in the field) and (2) the presence of higher-frequency internal waves, which are excited by non-linear interactions between basin-scale internal waves. The non-linear simulation indicates that only 10 % of the dissipation rate of the Kelvin wave is because of bottom friction, while the rest 90 % represents the energy that is radiated from the Kelvin wave to other modes. Also, this study shows that modes with periods between 5 and 8 h are excited by non-linear interactions between the fundamental Kelvin wave and horizontal Poincaré-type waves. A laboratory study of the resonant interaction between a periodic forcing and the internal wave field response has also been performed, confirming the resonance for the horizontal mode 1 Kelvin wave.     

Organotin pollution in Malta coastal zone

The speciation of organotins in seawater, surface microlayer and sediments in the marine environment of Malta is described. Concentrations of tributyltin (TBT) in bulk seawater inside the harbours were as high as 0.3 μg Sn L^‐1 but were below detection limits (5 ng Sn L^‐1) in open sea, 1.6 km offshore. In sediments, TBT levels were highest for the yacht marinas and ranged between 0.03 and 1.5 ug Sn g^‐1. Dibutyltin is more common in the surface microlayer than TBT. Diphenyl and monophenyltin were found infrequently in bulk seawater and in sediments. Tetrasubstituted organotins, namely, Me_nBu₍₄__n)Sn, where n = 1, 2, and 3, were found frequently in TBT‐contaminated sediments (0.1–9μg Sng^‐1), in seawater and in the microlayer where concentrations as high as 140 μg Sn L^‐1 (Me₃BuSn) were measured. Direct environmental methylation of TBT and that of its debutylated analogues may play a significant role in the geochemical cycling of tin under certain environmental conditions.     

Sovereign financial disaster risk management: The case of Mexico

In 2006, Mexico became the first transition country to transfer part of its public-sector natural catastrophe risk to the international reinsurance and capital markets. The Mexican case is of considerable interest to highly exposed transition and developing countries, many of which are considering similar transactions. Risk financing instruments can assure governments of sufficient post-disaster capital to provide emergency response, disaster relief to the affected population and repair public infrastructure. The costs of financial instruments, however, can greatly exceed expected losses, and for this reason it is important to closely examine their benefits and alternatives. This paper analyzes the Mexican case from the perspective of the risk cedent (the Ministry of Finance and Public Credit), which was informed by analyses provided by the International Institute for Applied Systems Analysis (IIASA). The rationale for a government to insure its contingent liabilities is presented along with the fiscal, legal and institutional context of the Mexican transaction. Using publicly available data, the paper scrutinizes the choice the authorities faced between two different risk-transfer instruments: reinsurance and a catastrophe bond. Making use of IIASA's catastrophe simulation model (CATSIM), this financial risk management decision is analyzed within the context of a public investment decision.     

Mobilization of arsenic and other trace elements of health concern in groundwater from the Salí River Basin, Tucumán Province, Argentina

The Salí River Basin in north-west Argentina (7,000 km²) is composed of a sequence of Tertiary and Quaternary loess deposits, which have been substantially reworked by fluvial and aeolian processes. As with other areas of the Chaco-Pampean Plain, groundwater in the basin suffers a range of chemical quality problems, including arsenic (concentrations in the range of 12.2–1,660 μg L⁻¹), fluoride (50–8,740 μg L⁻¹), boron (34.0–9,550 μg L⁻¹), vanadium (30.7–300 μg L⁻¹) and uranium (0.03–125 μg L⁻¹). Shallow groundwater (depths up to 15 m) has particularly high concentrations of these elements. Exceedances above WHO (2011) guideline values are 100% for As, 35% for B, 21% for U and 17% for F. Concentrations in deep (>200 m) and artesian groundwater in the basin are also often high, though less extreme than at shallow depths. The waters are oxidizing, with often high bicarbonate concentrations (50.0–1,260 mg L⁻¹) and pH (6.28–9.24). The ultimate sources of these trace elements are the volcanic components of the loess deposits, although sorption reactions involving secondary Al and Fe oxides also regulate the distribution and mobility of trace elements in the aquifers. In addition, concentrations of chromium lie in range of 79.4–232 μg L⁻¹ in shallow groundwater, 129–250 μg L⁻¹ in deep groundwater and 110–218 μg L⁻¹ in artesian groundwater. All exceed the WHO guideline value of 50 μg L⁻¹. Their origin is likely to be predominantly geogenic, present as chromate in the ambient oxic and alkaline aquifer conditions.