Platinum concentration in PM2.5 in the Mexico City Metropolitan Area: relationship to meteorological conditions

Abstract

Platinum (Pt) concentrations in PM_2.5 were evaluated by means of inductively coupled plasma mass spectrometry (ICP-MS) to evaluate the spatial and temporal behavior and to assess trends. Samples were taken from five representative sites in the Mexico City Metropolitan Area (MCMA): Tlalnepantla-northwest (NW), San Agustin-northeast (NE), La Merced -center (C), Coyoacan-southwest (SW), and Universidad Autonoma Metropolitana Iztapalapa-southeast (SE). Under three weather conditions: dry warm (DW-April), rainy (R-August), and dry cold (DC-November) in 2013. We found that the PM_2.5 median mass concentration was 24?μg m^?3?±?15?μg m^?3 while Pt concentration was 55?pg m^?3?±?15?pg m^?3 (median, interquartile range). Seasonal trend was identified: the concentrations decreased significantly in the following order DC?>?R>DW. No spatial distribution was observed. Interestingly, among other meteorically parameters, wind intensity resulted to be the major factor for the dispersion of Pt in PM2.5 in MCMA. Furthermore, we found that Pt concentrations increased significantly by 19.6% between 2011 and 2013. Regardless of the increase in Pt, carbon monoxide (CO) levels decreased opposite to a rise in vehicular fleet. These results urge for environment public policies that address the upward tendency of Pt levels especially in urban areas.     

Evolution of small inversions in chloroplast genome: a case study from a recurrent inversion in angiosperms

Small inversions (SIs) in the chloroplast genome of angiosperms are ubiquitous. These inversions are always flanked by inverted repeats (palindromes or quasipalindromes) between approximately 8 and 50 bp long that form a hairpin structure when the DNA is single-stranded. We evaluated different methodological and empirical issues about SI evolution. As a case study, we analysed an SI recently discovered in the psb C– trn S intergenic region of Prosopis (Fabaceae). First, we analysed how inversions can be optimized in cases where the inverted segment also shows indels and substitutions, proposing a method based on Fixed States Optimization. Second, we evaluated the occurrence of this inversion on a phylogeny that includes the major lineages of angiosperms. Finally, we assessed whether the occurrence of this inversion was related to the thermodynamic stability of the hairpin structure (measured by its corresponding free energy) and/or the length of the palindromes by using a modified version of Maddison's Concentrated Changes Test. Hairpin structure was conserved in most of the 154 sequences analysed, with the inversion taking place at least 10 times in different lineages (monocots, magnoliids, rosids). As was previously proposed for other SIs, our analysis strongly suggests that the occurrence of this inversion is correlated with higher hairpin stability. In contrast, we found no evidence of a correlation with longer palindromes. Our results are in agreement with the hypothesis that hairpin formation is a requisite for SI occurrence. However, alternative explanations cannot be discarded.
© The Willi Hennig Society 2008.     

Genetic and morphometric characterization of clones of Prosopis alba,Algarobia, selected for salt tolerance

Prosopis alba is an important Argentinean species with a great potential for the production of timber and nontimber products. Many studies showed high salt tolerance of this species, which allows it to be used in afforestation and reforestation of saline soils. In this study, we applied the morphometric technique to characterize 21 salt-tolerant clones (ST). Twenty of these clones were studied by inter-simple sequence repeat (ISSR) and simple sequence repeat (SSR), and their molecular patterns were compared with those of 22 individuals selected for salt sensitivity (SS). Most morphological traits revealed highly significant differences among ST clones, and four out of 11 characters showed high heritability. ISSR analysis allowed detecting 89 loci, 91 % of them variable. ST versus SS groups differ significantly from each other by the frequencies of 22 of these loci, from which 12 were significant at the matrix level. Analysis of six SSR loci for the same groups indicated that all of them were polymorphic at the 1 % criterion. Allelic frequencies of SSR also showed highly significant differences between SS and ST groups. Analysis of coancestry between individuals within SS and ST groups and between groups indicated that the molecular differentiation between them cannot be explained solely on relationship grounds. Molecular groupings based on ISSR and SSR showed consistency to each other, as supported by the highly significant coinertia in the distribution of individuals in principal component analysis scatterplots. This work is the first contribution which tends to associate molecular patterns with life history traits and morphological differences in Prosopis clones.     

Alkaloids from the flowers of Erythrina americana

The two alkaloids, α- and β-erythroidine have been identified in 0.034 and 0.11 % yield in flowers of Erythrina americana and could be responsible for the hypnotic activity of flower extracts.     

Geographic isolation and long-distance gene flow influence the genetic structure of the blue fan palm Brahea armata (Arecaceae)

Journal of Plant Research - The formation of the Baja California Peninsula (BCP) has impacted the microevolutionary dynamics of different species in ways that depend on biological traits such as...