Mercury enrichment in anthrosols and adjacent coastal sediments at a Classic Maya site, Marco Gonzalez, Belize

Elevated concentrations of total mercury (THg) are found in the surface soils and flanking wetland sediments at the Classic Maya coastal site of Marco Gonzalez, Belize. Significant concentrations (up to 1.3 µg·g−1 dry mass) of THg occur in leaf litter-rich soils, as well as in the artefact-rich anthrosol spread over the vegetated mound site of structures and occupation debris. The abundance and spatial pattern of major and trace elements measured in the surface soils indicate both site-scale controlling factors of topography, structures and vegetation on soil geochemistry as well as local highs in concentration compared with background, due to human activity. Geochemical stratigraphy of wetland sediment cores shows that a shift from carbonate-reef sediments to mangrove peat in the 13th century AD was attended by an input of allogenic (mineral) elements, including mercury. A THg concentration peak (0.8 μg·g−1) in brackish pool sediment is 210Pb-dated to 1960–1970 AD, but the incorporation of mercury in multiple cores adjacent to the site shows increasing mercury inputs to have occurred before, during Classic-period Maya occupation and following the sites abandonment. Analysis of element values from site-scale soil sampling, combined with results from off-site cores, provides a numerical framework upon which outlier values of THg and other element spatial patterns can be assessed, especially the spatial co-association of elements related to differences in soil–sediment matrices. Geochemical results from active soils developing from occupation deposits (anthrosols) and sediment cores open up questions concerning contemporary and past mercury accumulation at coastal Mayan sites, and the wider interaction of human and natural biogeochemical processes that occur in human-modified soils and coastal wetland sediments

Aneurismes dissecants d'aorta ascendent. Tractament quirúrgic

Els aneurismes dissecants d'aorta constitueixen una malaltia molt greu, de mal pronòstic i que acostuma a plantejar problemes diagnòstics i terapèutics importants, especialment en els casos aguts. Al nostre país la publicació dels casos operats és escassa. El pronòstic d'aquesta malaltia, el tractament mèdico-quirúrgic i la tècnica a seguir depenen en gran part de la localització de l'aneurisma i de la intervenció que es faci. En aquesta comunicació revisarem la nostra experiència en aquells casos en què la cirurgia es va circumscriure a l'aorta ascendent, amb intervenció sobre la vàlvula aòrtica o sense, i valorarem els problemes diagnòstics que hem trobat i la nostra conducta actual

Photodegradation of Phenol over a Hybrid Organo-Inorganic Material: Iron(II) Hydroxyphosphonoacetate

Water treatment is a hot topic, and it will become much more important in the decades ahead. Advanced oxidation processes are being increasingly used for organic contaminant removal, for example using photo-Fenton reactions. Here we report the use of an organo-inorganic hybrid, Fe[HO3PCH(OH)COO]·2H2O, as Fenton photocatalyst for phenol oxidation with H2O2 under UVA radiation. Preactivation, catalyst content, and particle size parameters have been studied/optimized for increasing phenol mineralization. Upon reaction, iron species are leached from the catalyst making a homogeneous catalysis contribution to the overall phenol photo-oxidation. Under optimized conditions, the mineralization degree was slightly larger than 90% after 80 min of irradiation. Analysis by X-ray photoelectron spectroscopy revealed important chemical modifications occurring on the surface of the catalyst after activation and phenol photodegradation. The sustained slow delivery of iron species upon phenol photoreaction is advantageous as the mixed heterogeneous−homogeneous catalytic processes result in very high phenol mineralization.Proyecto nacional MAT2010-1517

A review of combined advanced oxidation technologies for the removal of organic pollutants from water

Water pollution through natural and anthropogenic activities has become a global problem causing short-and long-term impact on human and ecosystems. Substantial quantity of individual or mixtures of organic pollutants enter the surface water via point and nonpoint sources and thus affect the quality of freshwater. These pollutants are known to be toxic and difficult to remove by mere biological treatment. To date, most researches on the removal of organic pollutants from wastewater were based on the exploitation of individual treatment process. This single-treatment technology has inherent challenges and shortcomings with respect to efficiency and economics. Thus, application of two advanced treatment technologies characterized with high efficiency with respect to removal of primary and disinfection by-products in wastewater is desirable. This review article focuses on the application of integrated technologies such as electrohydraulic discharge with heterogeneous photocatalysts or sonophotocatalysis to remove target pollutants. The information gathered from more than 100 published articles, mostly laboratories studies, shows that process integration effectively remove and degrade recalcitrant toxic contaminants in wastewater better than single-technology processing. This review recommends an improvement on this technology (integrated electrohydraulic discharge with heterogeneous photocatalysts) viz-a-vis cost reduction in order to make it accessible and available in the rural and semi-urban settlement. Further recommendation includes development of an economic model to establish the cost implications of the combined technology. Proper monitoring, enforcement of the existing environmental regulations, and upgrading of current wastewater treatment plants with additional treatment steps such as photocatalysis and ozonation will greatly assist in the removal of environmental toxicants

Leyva (Antonio de) [Material gráfico] : uno de los mas insignes capitanes de Carlos V

Plancha de aceroResumen: Descripción: retrato de Antonio Leiva de tres cuartos de figura y de perfil. Vestido con con gorro y piele