Exposure to chemical mixtures in Mexican children: high-risk scenarios

In developing countries, the management of environmental toxicants is inadequate, thus, humans may be exposed to levels higher than normal levels (background levels). Therefore, the aim of this study was to evaluate the exposure level of Mexican children to dichlorodiphenyltrichloroethane (DDT), dichlorodiphenyldichloroethylene (DDE), lead, and polycyclic aromatic hydrocarbons [using 1-hydroxypyrene (1-OHP) as exposure biomarker] and to assess the percentage of children exposed to these four compounds at concentrations higher than normal in each community studied. We performed random sampling in eight communities in Mexico (five communities in Chiapas State and three communities in San Luis Potosi State). DDT and DDE were analyzed by gas chromatography/mass spectrometry, the quantification of lead in blood was performed using atomic absorption spectrophotometry, and 1-OHP analyses were performed using HPLC with a fluorescence detector. Elevated DDT, DDE, and 1-OHP levels were found in children living in the indigenous communities of Chiapas State, while higher blood lead levels were found in two communities in San Luis Potosí. Approximately 30 % of children living in Chiapas were exposed to all four compounds at concentrations above the guidelines for each compound, whereas 48 % of children studied were exposed to all four contaminants at concentrations higher than normal in a community in San Luis Potosí State. As expected, our results showed that in hot spots, children are exposed to levels higher than normal. Therefore, child environmental health programs are urgently needed.     

Inocula from activated sludge for ready biodegradability testing: homogenization by preconditioning

The use of activated sludge as inoculum source in ready biodegradability tests (RBT) suffers from several drawbacks related to the heterogeneity of these communities. In this work, the ability of a 7-day aeration period in a mineral medium to homogenize the characteristics of various activated sludges, as suggested by some RBT, was studied. The biodegradation potential of three activated sludge supernatants obtained from different wastewater treatment plants was assessed in terms of cultivable cell density, dehydrogenasic activity and a profile of hydrolytic enzymes. After the preconditioning, the homogenization of these characteristics in the supernatants was observed, as well as a decrease. When preconditioned inocula were used in acetate RBT, the biodegradation kinetics were homogenized. However, some preconditioned supernatants lost their ability to degrade an easily-assimilable xenobiotic compound (aniline) during the observation period, showing the effect of inoculum preconditioning on the behavior of complex bacterial communities, specialist populations (e.g. aniline degraders) being more sensitive than generalist populations (e.g. acetate degraders). These results show that preconditioning cannot be an optional inoculum pretreatment in RBT, and emphasize the importance of further studies focusing on inoculum homogenization.     

Selective detection of metal ions,sulfites and glutathione with fluorescent pyrazolines: a review

Environmental Chemistry Letters - Pollution by toxic metals is a worldwide health issue, yet analytical methods to monitor selectively metal ions in complex media are limited. Fluorescence sensing...     

Between uncertainty and hope: Young leaders as agents of change in sustainable small-scale fisheries

The path to sustainable small-scale fisheries (SSF) is based on multiple learning processes that must transcend generational changes. To understand young leaders from communities with sustainable SSF management practices in Mexico, we used in-depth interviews to identify their shared motivations and perceptions for accepting their fishing heritage. These possible future decision-makers act as agents of change due to their organizational and technological abilities. However, young people are currently at a crossroads. Many inherited a passion for the sea and want to improve and diversify the fishing sector, yet young leaders do not want to accept a legacy of complicated socioenvironmental conditions that can limit their futures. These future leaders are especially concerned by the uncertainty caused by climate change. If fishing and generational change are not valued in planning processes, the continuity of fisheries, the success of conservation actions, and the lifestyles of young fishers will remain uncertain.Graphical abstract Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-021-01639-2.     

An experimental design for the optimization of the extraction methods of metallic mobile fractions from environmental solid samples

The evaluation of the cadmium and lead mobile forms from environmental solid samples provides information about their mobility and bioavailability. In the present study, the Cd and Pb mobile fractions were obtained by two modified extraction methods applied to industrial and acidic pH soils or to polluted sediments. In order to highlight that the extraction procedure does not significantly influence the quantitative atomic absorption spectrometric determination of cadmium and lead, the robustness of the extraction methods was evaluated and proven applying a Youden and Steiner factorial design. Within this experimental design, the shaking rate, the shaking time, and the solid/liquid extraction ratio were modified. The measurement uncertainty of the whole analytical procedure was assessed, the contribution of the factors involved in the extraction process being insignificant compared to the other uncertainty sources. The importance of the study is related to the fact that it proves the applicability in the routine laboratory practice of the modified extraction methods by increasing the extraction ratio following thorough optimization and robustness studies.     

Effect of pH,ionic strength,and background electrolytes on Cr(VI) and total chromium removal by acorn shell of Quercus crassipes Humb. & Bonpl.

The ability of Quercus crassipes acorn shells (QCS) to remove Cr(VI) and total chromium from aqueous solutions was investigated as a function of the solution pH, ionic strength, and background electrolytes. It was found that Cr(VI) and total chromium removal by QCS depended strongly on the pH of the solution. Cr(VI) removal rate increased as the solution pH decreased. The optimum pH for total chromium removal varied depending on contact time. NaCl ionic strengths lower than 200 mM did not affect chromium removal. The presence of 20 mM monovalent cations and anions, and of divalent cations, slightly decreased the removal of Cr(VI) and total chromium by QCS; in contrast, divalent anions (SO₄ ^2?, PO₄ ^2?, CO₃ ^2?) significantly affected the removal of Cr(VI) and total chromium. The biosorption kinetics of chromium ions followed the pseudo-second-order model at all solution pH levels, NaCl ionic strengths and background electrolytes tested. Results suggest that QCS may be a potential low-cost biosorbent for the removal of Cr(VI) and total chromium from aqueous solutions containing various impurities.     

Determination of copper in biological samples by flame atomic absorption spectrometry after precipitation with Me-BTAP

A simple and sensitive method was developed for determination of trace copper by direct precipitation preconcentration and detection with Flame Atomic Absorption Spectrometry (FAAS). The reagent 2-[2'-(6-methyl-benzothiazolylazo)]-4-aminophenol (Me-BTAP) was used as precipitating agent. The experimental conditions for the quantitative precipitation of copper, such as pH, amount of reagents, temperature and the effect of diverse ions on the precipitation have been investigated. It was found that copper is quantitatively extracted (> or =95%) and the method provides a sensitivity enhancement of 40-fold for a 10 ml sample volume with a detection limit of 0.5 microg l(-1). The proposed method was successfully applied for the determination of trace copper in water, urine and biological samples.     

Assessing the micro-phytoplankton response to nitrate in Comau Fjord (42°S) in Patagonia (Chile), using a microcosms approach

Anthropogenic (aquaculture) changes in environment nutrient concentrations may affect phytoplankton (biomass and taxa composition) in marine coastal waters off the Chilean Patagonia. The effects of adding nitrate (NO₃ ^?) to natural phytoplankton assemblages were evaluated considering biomass, cell abundance, and taxonomic composition. Microcosm experiments were performed in the spring, summer, and winter in the Comau Fjord located in Subantarctic Patagonia. At the end of the experiments, NO₃ ^? decreased rapidly and was undetectable in treatments, indicating a strong NO₃ ^? deficiency associated with an exponential increase in Chl-a concentrations, particulate organic nitrogen, and carbon in these treatments. Moreover, given the depleted nitrate concentrations of the spring and summer experiments, the micro-phytoplankton taxa structure shifted from mixed diatom and dinoflagellate assemblages (Ceratium spp., Dinophysis spp., Coscinodiscus sp., Rhizosolenia pungens) to assemblages dominated by blooms of the classic chain-forming diatoms found in temperate and cold waters such as Chaetoceros spp., Skeletonema spp., and Thalassiosira spp. Thus, nitrogen sources (i.e., nitrate, ammonia) may influence phytoplankton abundance and biomass accumulation dynamics in the northern section of Patagonia. It also emphasizes the importance of diatom taxa in regards to the short-term response of phytoplankton to changing environmental nutrient conditions due to natural (decreasing freshwater stream flow) and anthropogenic (aquaculture) events. This situation may be one of the future scenarios in the Patagonian fjords, thus stressing the needs for active environmental monitoring and impact assessment.     

Progressive Optimal Technology-based Border Carbon Adjustment (POT BCA) - A New Approach to an Old Carbon Problem

The idea of Border Carbon Adjustment (BCA), which makes it possible to transform the standard tax on carbon emissions from production (origin principle) to a tax system imposed at the point of consumption (destination principle), has received a considerable amount of attention from academia and policymakers. In this paper, we go back to the source of environmental destination-based taxation and generalize the results of Markusen (Journal of International Economics, 5, 15–29, 1975) for optimal tax and tariff by extending domestic environmental policy on both goods featuring positive carbon intensities. Following Jakob et al. (Environmental and Resource Economics, 56(1), 47–72, 2013) we remove the strategic term from the optimal tariff and deal with the so-called optimal carbon tariff, targeting primarily environmental externality. Further, we develop a handy approximation for optimal tax and optimal carbon tariff structure in a multiple good setting. Such trade taxation is, however, likely to face further legal obstacles, which may hinder its implementation. This motivates us to adjust the results accordingly and to include refunds for low-carbon investments in a ‘dirty’ country granted proportionally to the difference in carbon intensities between trade partners. This new scheme, known as Progressive Optimal Technology-based Border Carbon Adjustment (POT BCA), mitigates several legal problems and increases political acceptance compared to the ‘standard’ BCA. It can also be seen as advantageous from the economic point of view: it mimics the performance of the optimal carbon tariff while aiming to decrease foreign carbon intensity over the long term.     

Comparing the Use of Indigenous Knowledge with Classification and Ordination Techniques for Assessing the Species Composition and Structure of Vegetation in a Tropical Forest

dentification of groups that are similar in their floristic composition and structure (habitat types) is essential for conservation and forest managers to allocate high priority areas and to designate areas for reserves, refuges, and other protected areas. In this study, the use of indigenous knowledge for the identification of habitat types in the field was compared against an ecological characterization of habitat types, including their species composition obtained by using classification and ordination techniques for a tropical landscape mosaic in a rural Mayan area of Quintana Roo, Mexico. Plant diversity data calculated from 141 sampled sites chosen randomly on a vegetation class’s thematic map obtained by multispectral satellite image classification were used for this propose. Results indicated high similarity in the categorization of vegetation types between the Mayan classification and those obtained by cluster and detrended correspondence analysis. This suggests that indigenous knowledge has a practical use and can be comparable to that obtained by using science-based methods. Finally, identification and mapping of vegetation classes (habitat types) using satellite image classification allowed us to discriminate significantly different species compositions, in such a way that they can provide a useful mechanism for interpolating diversity values over the entire landscape.