Parental investment without kin recognition: Simple conditional rules for parent-offspring behavior

Species differ widely with regard to parental investment strategies and mechanisms underlying those strategies. The passing of benefits to likely offspring can be instantiated with a number of different computational and behavioral systems. We report results from an agent-based model in which offspring maintain proximity with parents and parents transmit benefits to offspring without the capacity of either parent or offspring to 'recognize' one another. Instead, parents follow a simple rule to emit benefits after reproducing and offspring follow a simple rule of moving in the direction of positive benefit gradients. This model differs from previous models of spatial kin-based altruism in that individuals are modeled as having different behavioral rules at different life stages and benefits are transmitted unidirectionally from parents to offspring. High rates of correctly directed parental investment occur when mobility and sociality are low and parental investment occurs over a short period of time. We suggest that strategies based on recognition and bonding/attachment might serve to increase rates of correctly directed parental investment under parameters that are shown here to otherwise lead to high rates of misdirected and wasted parental investment.     

Determination of gaseous polycyclic aromatic hydrocarbons by a simple direct method using thermal desorption–gas chromatography–mass spectrometry

In the last decade, the development of novel analytical methodologies enabled the identification of several environmental pollutants responsible for health problems associated with indoor exposure. Polycyclic aromatic hydrocarbons (PAHs) are among the potential hazardous chemicals present in ambient air. Due to their bioaccumulation potential and carcinogenic/mutagenic effects, 16 PAHs are currently listed as priority air pollutants. The main goal of this work was to implement a new and simple method for sampling and determination of PAHs in air by using a thermal desorption (TD) technique followed by gas chromatography coupled with mass spectrometry analysis. A detailed study was carried out to optimise the experimental method in each of its phases, including (active) sampling, TD and chromatographic analysis. The results demonstrate that this approach allowed the detection and quantification of the six more volatile PAHs, namely, naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, and anthracene. Acceptable precision and good linearity over the explored range were obtained. No carry-over was observed during experimental tests and the method provided a reproducible answer. The applicability of the novel methodology was tested in real environment, namely, on the roof of a building in an urban area, in a domestic kitchen and in a collective car garage. The method enabled the identification of two PAHs in the field samples, specifically, naphthalene (two rings) and phenanthrene (three rings). With regard to PAHs sample composition, the most abundant PAH found, in the three different locations, was naphthalene, accounting for about 84–100 % of the total PAH mass detected.     

Biosorption of zinc ions from aqueous solution by the microalga Scenedesmus obliquus

Aquatic environments are often exposed to toxic heavy metals, which gain access to the food chain via microalgae and may cause severe problems at higher trophic levels. However, such a metabolic specificity can be taken advantage of in bioremediation strategies. The potential of a novel wild strain of Scenedesmus obliquus, previously isolated from a heavy metal-contaminated site in northern Portugal, to remove Zn from aqueous solutions was thus studied, using several initial concentrations. The removal extent reached its maximum by 1 day: 836.5 mg Zn/g biomass, at the initial concentration of 75 mg/L, mainly by adsorption onto the cell surface. Comparative studies encompassing a commercially available strain of the same microalgal species led to a maximum removal extent of only 429.6 mg Zn/g biomass, under identical conditions. Heat-inactivated cells permitted a maximum removal of 209.6 mg Zn/g biomass, at an initial concentration of 50 mg Zn/L. The maximum adsorption capacity of Zn, estimated via Langmuir’s isotherm, was 330 mg Zn/g biomass. Finally, Zn removal was highest at pH 6.0–7.0. It was proven, for the first time, that such a wild microalga can uptake and adsorb Zn very efficiently, which unfolds a particularly good potential for bioremediation. Its performance is far better than similar (reference) species, especially near neutrality, and even following heat-treatment.     

Transport of rimsulfuron and its metabolites in soil columns

This paper presents a study on degradation, sorption and transport of the sulfonylurea herbicide rimsulfuron and its major metabolites in alluvial soil columns. The formulation of rimsulfuron was found to strongly affect its degradability. Hydrolysis of pure rimsulfuron takes place rapidly in distilled water (t(1/2)=2.2 days) or indeed instantaneously in alkaline solution. The formulated rimsulfuron (Titus, 25% rimsulfuron, Du Pont De Nemours) is more persistent in alluvial soil suspensions (t(1/2)=7.5 days). The study of sorption of Titus and its two major metabolites (1 and 2) revealed that these three chemicals are potentially highly mobile in the studied soil: in suspension distribution coefficients of 0.0028, 0.125 and 0.149 cm3 g(-1) were obtained respectively. Given the instability of rimsulfuron in alkaline solutions, the pH effect was evaluated with metabolite 2 in water saturated Fontainebleau sand columns at pH 6, 8 and 10. Transport was found to be strongly dependent on pH; a linear relationship was obtained between pH and the retardation factor or the dispersion coefficient. In alluvial soil columns, rimsulfuron from Titus was found to be very mobile (R=1.2) and rapidly degraded into metabolites 1 and 2, which were transported at a similar velocity. Nevertheless, the risks of groundwater contamination by rimsulfuron seem very low, as it is rapidly degraded under dynamic conditions (t(1,2)=1.4 days). On the other hand the relatively stable metabolite 2 seems likely to persist in the soil and to be transported to the groundwater. Special attention should thus be given to this compound at least as long as its harmlessness is not demonstrated.     

Characterization and recycling of polymeric components present in cell phones

The cell phone market is developing at a rapid speed. Today there are more than 1.6 billion consumers in the world, and the lifetime of a cell phone is less than 2 years. As a consequence, there is an increase in the waste associated to this product, and many alternatives to the disposal of the cell phones are being studied, such as recycling which shows to be the most important. It is crucial to know what materials constitute the cell phone in order to carry out recycling and determine environmental and economical issues. This work presents an evaluation of the cell phone components, characterizing the raw materials and some properties of the recycled materials.     

São Paulo Aerosol Characterization Study

Abstract

The São Paulo Metropolitan area (SPMA) is characterized as having one of the worst air pollution problems in Brazil,with frequent violations of air quality standards for particulate matter. This paper presents the results of a eceptor model source apportionment study carried out to develop a quantitative database on which a control strategy could be developed. The study was conducted in four sites with distinct land uses. Fine, coarse (CP), and total suspended particles (TSP) samples were collected on Teflon and glass filters and analyzed by x-ray fluorescence XRF), ion chromatography, and thermal evolution. The sources were characterized by similar methodology. Chemical mass balance (CMB) receptor modeling indicated that carbonaceous material plays an important role in the aerosol composition; that the three major source categories contributing to the fine particles are vehicles, secondary carbon, and sulfates; and that the main contributors to CP and TSP are road dust and vehicles. All sampling sites presented the same general pattern in terms of source contribution, although this contribution varied from site to site.     

Effect of light supply on CO2 capture from atmosphere by Chlorella vulgaris and Pseudokirchneriella subcapitata

Carbon dioxide (CO₂) is one of the primary greenhouse gases that contribute to climate change. Consequently, emission reduction technologies will be needed to reduce CO₂ atmospheric concentration. Microalgae may have an important role in this context. They are photosynthetic microorganisms that are able to fix atmospheric CO₂ using solar energy with efficiency ten times higher than terrestrial plants. The objectives of this study were: (i) to analyse the effect of light supply on the growth of Chlorella vulgaris and Pseudokirchneriella subcapitata; (ii) to assess the atmospheric CO₂ capture by these microalgae; and (iii) to determine the parameters of the Monod model that describe the influence of irradiance on the growth of the selected microalgae. Both microalgae presented higher growth rates with high irradiance values and discontinuous light supply. The continuous supply of light at the highest irradiance value was not beneficial for C. vulgaris due to photooxidation. Additionally, C. vulgaris achieved the highest CO₂ fixation rate with the value of 0.305 g-CO₂ L^?1 d^?1. The parameters of the Monod model demonstrated that C. vulgaris can achieve higher specific growth rates (and higher CO₂ fixation rates) if cultivated under higher irradiances than the studied values. The presented results showed that microalgal culture is a promising strategy for CO₂ capture from atmosphere.     

Climate-driven changes in air quality over Europe by the end of the 21st century,with special reference to Portugal

Climate change alone may deeply impact air quality levels in the atmosphere because the changes in the meteorological conditions will induce changes on the transport, dispersion and transformation of air pollutants. The aim of this work was to evaluate the impact of climate change on the air quality over Europe and Portugal, using a reference year (year 1990) and a IPCC SRES A2 year (year 2100). The Hadley Centre global atmospheric circulation model (HadAM3P) was used to provide results for these two climatic scenarios, which were then used as synoptic forcing for the MM5-CHIMERE air quality modelling system. In order to assess the contribution of future climate change on O₃ and PM concentrations, no changes in regional emissions were assumed and only climate change forcing was considered. The modelling results suggest that the O₃ monthly mean levels in the atmosphere may increase almost 50 μg m^?3 across Europe in July under the IPCC SRES A2 scenario. In Portugal, this increase may reach 20 μg m^?3. The changes of PM10 monthly average values over Europe will depend on the region. The increase in PM10 concentrations during specific months could be explained by the average reduction of the boundary layer height and wind speed.