Carbon and hydrogen isotope effects during sorption of organic contaminants on carbonaceous materials

Stable carbon and hydrogen isotopes can be an efficient means to validate biodegradation of organic contaminants in groundwater since it results in an isotopic fractionation. A prerequisite in applying this method in the field is the proof that other processes decreasing the contaminant concentration are conservative with respect to isotope effects. In this paper we show for carbon isotopes of halogenated hydrocarbon compounds [trichloroethene (TCE), cis-dichloroethene (c-DCE), vinylchloride (VC)] and carbon and hydrogen isotopes of BTEX compounds (benzene, toluene, p-xylene) that no significant fractionation occurs during equilibrium sorption onto activated carbon, lignite coke and lignite. In general, effects were in the range of the reproducibility limit of the analytical instrument (0.5 per thousand for delta13C, and 8 per thousand for delta2H). This observation was made for fractions sorbed of less than 5% to more than 95%. Also for rate-limited sorption of TCE onto activated carbon, no significant fractionation in carbon isotopes could be observed. These findings support the assumption that for these classes of compounds, sorption processes in aquifer systems are conservative with respect to isotope effects.     

Phenotypic plasticity in Scenedesmus incrassatulus (Chlorophyceae) in response to heavy metals stress

The microalgae genus Scenedesmus is commonly found in freshwater bodies, wastewater facilities and water polluted with heavy metals. Phenotypic plasticity in Scenedesmus has been documented in response to a wide variety of conditions; however, heavy metals have not been comprehensively documented as phenotypic plasticity inducers. In this study, we report the phenotypic plasticity of Scenedesmus incrassatulus (a non-spiny, four-cell coenobium forming species) in response to EC₅₀ value of copper, cadmium and hexavalent chromium. S. incrassatulus was grown in batch cultures in the presence of each metal. Chlorophyll-a content, cell size, parameters derived from the schematic energy-flux model for photosystem II, and morphotype expressions were recorded. Divalent cation metals induced unicellular forms, and hexavalent chromium produced out-of-shape coenobia corresponding to various stages of autospore formation. The changes induced by divalent metals were interpreted as phenotypic plasticity, because they were always associated to population doublings and were reversible when toxicant pressure was removed (only for Cu). Copper was the best inductor of unicellular forms and also affected significantly all the photosynthetic parameters measured. The developed morphotypes could confer ecological advantages to S. incrassatulus in metal stressed environments.     

Behaviour of simazine in soil amended with the final residue of the olive-oil extraction process

Addition of organic wastes to agricultural soils is becoming a common practice as a disposal strategy and to improve the physical and chemical soil properties. However, in order to optimise the use of organic wastes as soil amendments, their effect on the behaviour of other compounds that are also used in agriculture, such as pesticides, needs to be assessed. In this work, we have investigated the effects of the addition of the final solid residue of the new technology of olive-oil extraction (extracted alperujo or solid olive-mill waste, SOMW2) on the sorption, degradation and leaching of the herbicide simazine in a sandy loam soil. The results are compared with those of a previous study, where the intermediary by-product of the olive-oil processing technology (unextracted alperujo or SOMW1) was applied to the same soil. The soil was amended in the laboratory with SOMW2 at two different rates (5% and 10% w/w). Simazine sorption isotherms showed a great increase in herbicide sorption after SOMW2 addition to soil. SOMW2 addition also increased sorption irreversibility. Incubation studies revealed reduced biodegradation of simazine in the soil amended with SOMW2 compared to the unamended soil. Breakthrough curves of simazine in handpacked soil columns showed that SOMW2 addition retarded the vertical movement of the herbicide through the soil and greatly reduced the amount of herbicide available for leaching. Interestingly, the results were quantitatively different from those obtained for the intermediary by-product SOMW1, illustrating the importance of the specific characteristics of the organic amendment in determining its effect on pesticide behaviour.     

Analysis of PM10, PM2.5, and PM2 5-10 concentrations in Santiago, Chile, from 1989 to 2001

Daily particle samples were collected in Santiago, Chile, at four urban locations from January 1, 1989, through December 31, 2001. Both fine PM with da < 2.5 microm (PM2.5) and coarse PM with 2.5 < da < 10 microm (PM2.5-10) were collected using dichotomous samplers. The inhalable particle fraction, PM10, was determined as the sum of fine and coarse concentrations. Wind speed, temperature and relative humidity (RH) were also measured continuously. Average concentrations of PM2.5 for the 1989-2001 period ranged from 38.5 microg/m3 to 53 microg/m3. For PM2.5-10 levels ranged from 35.8-48.2 microg/m3 and for PM10 results were 74.4-101.2 microg/m3 across the four sites. Both annual and daily PM2.5 and PM10 concentration levels exceeded the U.S. National Ambient Air Quality Standards and the European Union concentration limits. Mean PM2.5 levels during the cold season (April through September) were more than twice as high as those observed in the warm season (October through March); whereas coarse particle levels were similar in both seasons. PM concentration trends were investigated using regression models, controlling for site, weekday, month, wind speed, temperature, and RH. Results showed that PM2.5 concentrations decreased substantially, 52% over the 12-year period (1989-2000), whereas PM2.5-10 concentrations increased by approximately 50% in the first 5 years and then decreased by a similar percentage over the following 7 years. These decreases were evident even after controlling for significant climatic effects. These results suggest that the pollution reduction programs developed and implemented by the Comisión Nacional del Medio Ambiente (CONAMA) have been effective in reducing particle levels in the Santiago Metropolitan region. However, particle levels remain high and it is thus imperative that efforts to improve air quality continue.     

Occurrence of polybrominated diphenylethers, polychlorinated dibenzo-p-dioxins, dibenzofurans and biphenyls in coastal sediments from Spain

Fifteen sediment samples were analysed in order to determine their content of polybrominated diphenylethers (PBDEs), polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and biphenyls (PCBs). Samples were collected from several hot spots on the Spanish coast, such as the harbours of Almeria and Tarragona, and the mouths of the Besos and Llobregat rivers in Barcelona. A generic analytical procedure based on Soxhlet extraction followed by an automated cleanup system and gas chromatography-ion trap-mass spectrometry was employed for determining the toxic congeners of PCDDs and PCDFs, as well as dioxin-like PCBs. As regards PBDE determinations, a rapid method based on the use of selective pressurized liquid extraction followed by gas chromatography-negative ion chemical ionization-mass spectrometry was applied. Total toxicity equivalent (WHO-TEQ) values were calculated using the toxicity equivalent factors proposed by WHO for dioxin-like PCBs, PCDDs and PCDFs. WHO-TEQ values ranged from 0.3 to 75 pg/g dry weight (dw), with PCB contribution on the toxicity of the samples between 1 and 84%. Total PBDE levels ranged from 2.7 to 134 ng/g dw, with BDE-209 contribution on the total PBDE contamination between 50 and 99%.     

An educational intervention in road safety among children and teenagers in Mexico

Objective: The purpose of this article is to describe a public school–based educational intervention (EI) designed to increase knowledge, improve attitudes, and change practices related to road safety.

Methods: We used a mixed-methods evaluation of a road traffic safety baseline diagnosis conducted in 4 public schools, 2 primary and 2 secondary. Research was organized into 4 phases: (1) diagnosis, (2) EI design, (3) implementation, and (4) evaluation. We used convenience sampling (n = 219 students) across schools and applied a pre-/posttest design based on quantitative and qualitative data. The former related to surveys on road safety experiences, knowledge, attitudes, and practice and the latter to observation checklists, community mapping, ethnography, and focus groups. To compare pre–post scores, we used multilevel mixed-effect ordinal logistic regressions. We developed data matrices, field notes, and systematized community mapping. We also transcribed focus group discussions, generated categories, and carried out thematic analysis.

Results: Ethnography indicated poor sidewalk conditions, no helmet or seat belt use, overcrowded public transportation, and no traffic lights or proper signals. Pedestrians did not use sidewalks and crossed streets unsafely. Subsequent to the intervention, however, the study population showed significant changes in their knowledge, practices, and attitudes. They identified road traffic incidents (RTIs) as the first cause of death among children and youth, and most understood that the solution to the problem was incumbent upon each and every individual. They also displayed increased perceptions of danger in practices such as traveling on overcrowded public transportation, failing to wear seat belts in cars and helmets on motorcycles, crossing the street while using mobile phones or playing with friends, and riding with drunk drivers. Changes varied according to gender, and students reported being able to carry out safe practices only when they were in control of the situation; for instance, as pedestrians.

Conclusions: Because safe practices depend not only on children and youth but on the adults and social environment surrounding them, it is essential to engage parents, teachers, and decision makers in efforts to reduce RTIs. This will improve the establishment of commitments to impact social reality through consistent changes and mobilize greater resources for creating more secure communities in matters of road safety.     

Polymorphism in soft coral larvae revealed by amplified fragment-length polymorphism (AFLP) markers

The dioecious Red Sea soft coral Parerythropodium fulvum fulvum breeds its nonsymbiotic planula larvae on the surface of female colonies for less than a week. After completing their development, larvae crawl and settle near maternal colonies. Here we study the genetic polymorphism of developing larvae by the use of amplified fragment-length polymorphism markers. Four reproductive colonies from shallow water populations (two from a dense population and two from a less densely populated area 100 m away) were chosen, and ten larvae were randomly collected from each colony. DNA was analyzed by using three different primer combinations producing 61, 63, 63 polymorphic markers, respectively. All larvae exhibited different banding patterns from one another, illustrating the prominent role of sexual reproduction for the production of larvae. Nei's mean genetic distances for all 12 possible pair-wise combinations for larval origins revealed, in most cases, that sister larvae are genetically closer than larvae from different colonies and that larvae may be grouped into three statistical clusters in accordance with colony origin and population studied. The usefulness of molecular methodologies in coral population genetics is discussed. Received: 26 March 1999 / Accepted: 19 October 1999     

Bed load transport of sediments and morphodynamics in the Topolobampo coastal lagoon system,Mexico

The Topolobampo coastal lagoon system, located on the eastern side of the Gulf of California, is a marine zone of considerable economic importance with vessel traffic, dredging operations and aquaculture development. Despite its relevance as a conservation site, this ecosystem has been poorly studied. Since life in marine substrates is abundant, we investigated the capability of tidal hydrodynamics in the lagoon to erode and to accumulate sediment. We calculated the morphodynamics caused by bed load sediment transport applying a two dimensional non-linear hydrodynamic finite difference model. Bed erosion and accretion patterns of sediment (for specific grain size: 170 μm) were determined from the divergence of sediment transport. After a year of numerical simulation of sediment transport the areas of noticeable changes on the bottom of the lagoon have been revealed. Most of sediment accretion took place in the narrow steeped channel connecting the Topolobampo and Ohuira sections. This area appears characterized by the presence of high tidal velocity gradients. Another finding was that accretion areas were coupled with erosion zones in an alternating form. This outcome suggests that sediment do not travel long distances but is deposited nearby the erosion sites. The results are strong evidence of the influence of tidal hydrodynamics on the sediments distribution in the Topolobampo coastal lagoon system and on the generation of substrates where marine life may find protection.     

Identification of Enteric Viruses in Foods from Mexico City

Foodborne viruses are a common and, probably, the most under-recognized cause of outbreaks of gastroenteritis. Among the main foods involved in the transmission of human enteric viruses are mollusks, and fruits and vegetables irrigated with wastewater and/or washed with non-potable water or contaminated by contact with surfaces or hands of the infected personnel during its preparation. In this study, 134 food samples were analyzed for the detection of Norovirus, Rotavirus, and Hepatitis A virus (HAV) by amplification of conserved regions of these viruses. From the 134 analyzed samples, 14 were positive for HAV, 6 for Norovirus, and 11 for Rotavirus. This is the first report in Mexico where emphasis is given to the presence of HAV and Norovirus on perishable foods and food from fisheries, as well as Rotavirus on frozen vegetables, confirming the role of vegetables and bivalve mollusks as transmitting vehicles of enteric viruses.