Recycling extruded polystyrene by dissolution with suitable solvents

The amount of extruded polystyrene (XPS) waste has increased in recent years due to the increase of its use in the thermal insulation of buildings, transport vehicles, and refrigerators, among others. Dissolution with suitable solvents to achieve a volume reduction of more than 100 times without degradation of polymer chains is one of the cheapest and most efficient methods of recycling XPS. Several environmentally friendly solvents have been tested as dissolution agents for XPS volume reduction; the action of these solvents does not produce any degradation of polymer chains. The solubility of the polymer in such solvents at different temperatures was investigated. The solvent can be easily recycled by distillation, obtaining a high-quality recycled polymer. Chemical Feedstock Recycling & Other Innovative Recycling Techniques 6     

Predictors of concentrations of hexachlorobenzene in human adipose tissue: a multivariate analysis by gender in Southern Spain

Hexachlorobenzene (HCB) was measured in adipose tissue intraoperatively collected from 387 subjects over 16 years old undergoing surgery in two hospitals in Granada (Southern Spain). HCB was quantified in 90.7% of subjects. The concentrations and frequencies of HCB were similar to those reported in adipose tissue samples in other recent European studies. Exposure patterns differed between females and males: higher HCB concentrations were found in females than in males (geometric mean 18.3 vs. 6.8 ng/g, p<0.001). The relationship between HCB concentrations and exposure risk factors was assessed by multivariate analysis stratifying by gender. In men, HCB concentrations were predicted (r(2)=0.45) by age, body mass index (BMI), place of residence, smoking, consumption of fish, chicken and cheese, occupation related to agriculture, and family involvement in construction activities. In women, HCB concentrations were predicted (r(2)=0.50) by age, BMI, consumption of milk and cheese, and occupation related to industry. The finding that women had three-fold higher levels of HCB than the men deserves further investigation.     

Assessment of aliphatic-aromatic copolyester biodegradable mulch films. Part I: field study

The objective of this work was to study the use of new biodegradable films in agriculture under open field conditions. Three biodegradable mulch films made from modified biodegradable polyester of different thicknesses and colors (black and white) and a conventional low density polyethylene (LDPE) mulch film were used to cover the beds of tomato plants. Changes in physical appearance of the films were recorded as well as changes in their mechanical, optical, and physical properties. Once tomato harvest was completed, the conventional LDPE mulch film was removed and all the tomato plants were cut using a mower. The biodegradable mulch films were plowed into the soil. The change in the appearance of the film was recorded and samples of each film after plowing were characterized according to the properties mentioned above. After the biodegradable films photodegraded, cross-link formation occurred within the films which promoted brittleness. Titanium dioxide, an additive used to produce white color in the films, catalyzed the photodegradation, while carbon black used for black color stabilized the photodegradation. The white films started to degrade after two weeks while it took about eight weeks for the black films to significantly degrade. The black biodegradable film seems to be a more promising alternative as a mulch film because of the comparable yields and weed suppression ability to conventional mulch film.     

Thermally assisted mechanical dewatering (TAMD) of suspensions of fine particles: analysis of the influence of the operating conditions using the response surface methodology

Thermally assisted mechanical dewatering (TAMD) is a new process for energy-efficient liquid/solids separation which enhances conventional-device efficiency. The main idea of this process is to supply a flow of heat in mechanical dewatering processes to favour the reduction of the liquid content. This is not a new idea but the proposed combination, especially the chosen operating conditions (temperature <100 degrees C and pressure <3000 kPa) constitutes an original approach and a significant energy saving since the liquid is kept in liquid state. Response surface methodology was used to evaluate the effects of the processing parameters of TAMD on the final dry solids content, which is a fundamental dewatering parameter and an excellent indicator of the extent of TAMD. In this study, a two-factor central composite rotatable design was used to establish the optimum conditions for the TAMD of suspensions of fine particles. Significant regression models, describing changes on final dry solids content with respect to independent variables, were established with regression coefficients (usually called determination coefficients), R(2), greater than 80%. Experiments were carried out on a laboratory filtration/compression cell, firstly on different compressible materials: synthetic mineral suspensions such as talc and synthetic organic suspensions such as cellulose, and then on industrial materials, such as bentonite sludge provided by Soletanche Bachy Company. Experiment showed that the extent of TAMD for a given material is particularly dependent on their physical and chemical properties but also on processing parameters.     

Mining and corruption

This study examines the links between mineral dependency and corruption. Specifically, it develops a cross-section econometric model that estimates the effects of per capita income, fuel exports, non-fuel exports, and average per unit value of mineral exports on corruption.     

Trade''s Dynamic Solutions to Transboundary Pollution

This study develops a differential game to examine the effects of trade liberalization on transboundary water pollution. Water pollution is due to wastewater emissions from countries in a shared waterway along the U.S.–Mexico border with available data of pollution abatement costs, public health damages, and trade benefits. Noncooperative and cooperative games are examined with changes in trade policy and public health damages. Results show trade liberalization leads Mexico to curtail pollution in both games. Cooperation and trade liberalization limit emissions from both countries and curtail strategic behavior of the United States from Mexico's pollution control efforts in the noncooperative game.     

Uptake and elimination of radiocaesium in fish and the "size effect."

A number of hypotheses have previously been developed concerning the rates of uptake and elimination of radiocaesium (137Cs) in fish. These include the influence of potassium and other water chemical parameters on both uptake and elimination, and the effect of fish size on accumulation. In order to test these hypotheses, we have assembled a data set comprising more than 1,000 measurements of radiocaesium (137Cs) in predatory fish (perch, pike and brown trout) in nine European lakes during the years after Chernobyl. These data have been analysed using simple models for uptake and excretion of 137Cs in fish, showing that: 1. Fish-water concentration factors (CF) were inversely proportional to potassium [K+] concentration of the different lakes, in agreement with previous studies. 2. The uptake rate of 137Cs in fish was negatively correlated with lake [K+], but excretion rate was independent of [K+]. 3. Lower than expected CF values were found in one lake, Iso Valkj?rvi, Finland. This is attributed to inhibition of the K+ (and therefore 137Cs) high affinity transport system in aquatic plants and fish by low pH and/or low Ca2+. 4. The inclusion of fish weight as a parameter in our dynamic model significantly improves the ability of the model to fit the observed measurements of 137Cs. 5. The model developed from the above hypotheses was able to fit the data from nine different lakes to within approximately a factor of 3 of the observed values.     

A binational, supply-side evaluation for managing water quality and invasive fouling species on California's coastal boats

Integrated solutions are needed for sustainable management of risks posed by recreational boats to coastal water quality and ecosystems. Fouling organisms roughen vessel hull surfaces, creating friction that slows sailboats and increases fuel consumption by powerboats. Hull fouling control strategies for recreational boats that are stored in the water may include antifouling hull paints, newer alternative hull coatings, periodic in-water hull cleaning, and excluding propagules by surrounding the boat with a slip liner or raising it above water on a lift. Copper discharged to harbor waters from antifouling paints via passive leaching and in-water hull cleaning may elevate dissolved copper levels above government standards. Invasive species carried among boat-hull fouling organisms may be introduced as boats move among coastal areas. Some of these species tolerate copper in antifouling paints and copper-polluted harbor waters. Policy development must consider supply-side capacity, as well as economic and environmental sustainability, in managing these issues. This paper presents a supply-side evaluation useful in developing policies to co-manage water quality and invasive species risks for recreational boats navigating along the coasts of California, the Baja California peninsula and California's Sacramento-San Joaquin Delta. Supply-side perspectives on services, materials, costs, and boat owner behaviors, such as residence and travel patterns, awareness of hull-coating choices and selection of hull coatings, are determined. Analyses include evaluation of risks, risk management capacity and costs, and role of education in risk management. The issues raised are broadly applicable, as they are appearing on research and policy agendas in diverse coastal areas.     

Dignity and the right of internally displaced adolescents in Colombia to sexual and reproductive health

In Colombia, national policies and laws on the protection of vulnerable populations pay specific attention to the sexual and reproductive health needs and rights of internally displaced adolescents. This paper describes how a United Nations Population Fund (UNFPA)-supported programme (September 2000-August 2004) on the sexual and reproductive health of internally displaced adolescents contributed to restoring their dignity as a precursor to promoting their sexual and reproductive health rights. Different forms of the arts were used as basic techniques to discover their body and to provide sexual and reproductive health information and education. The arts were found to play a key role in restoring their dignity. Although dignity appeared to be a determinant of greater awareness of rights, it did not lead to increased empowerment with regard to rights. The availability of and access to sexual and reproductive health services remains a problem and displaced populations continue to have little or no power to hold their authorities accountable.     

Ultraviolet Irradiance over Mexico City

Abstract

This article compiles and analyzes information on the interaction of both ground-level ultraviolet radiation and anthropogenic ozone in the extremely polluted atmosphere of Mexico City. Simultaneous anthropogenic ozone and global flux (sun and sky) measurements were recorded in near ultraviolet radiation (295-385 nm) for a 30-month period (March 1990 to August 1992). Results reveal that under clear sky conditions, high concentrations of ozone (and presumably of other pollutants) impede UV-fluxes from reaching their maximum values. Furthermore, heavy cloud cover causes ozone concentrations to reach their minimum values together with UV-minimum fluxes. Seasonal variation in UV-irradiance is also discussed. Findings indicate that maximum UV-fluxes occur in spring and summer and that minimum values occur in autumn and winter. Significant daily local reductions in UV-fluxes (up to 50%) during afternoon hours in Mexico City can be attributed to air pollution. Finally, the growing incidence of rickets in children residing in the Mexico City metropolitan area may be related both to dietary deficiencies and to the UV-flux depletion on the ground.