An overview of patterns and dynamics of suspended sediment transport in an agroforest headwater system in humid climate: Results from a long-term monitoring.

Small headwater catchments deliver large quantities of suspended sediment (SS) to the ocean. However, there are relatively few studies focused on the study of patterns and dynamics of suspended sediment in headwater catchments over the long-term (10 year or more). In this study, the dynamics of suspended sediment transport were examined at different time scales in a small headwater catchment in NW Spain, based on a 12-year dataset from high-resolution monitoring. The results revealed that, similar to other humid catchments, the hydrological response was highly dependent on initial conditions, especially in autumn and summer. However, in winter and spring the hydrology was more influenced by rainfall amount. The annual suspended sediment was 117 Mg, which equates to a suspended sediment yield of 10 Mg km-2 y-1. The SS yield in the Corbeira catchment is related to runoff generation and flooding, which play a key role in sediment yield from the catchment. About 80% of the annual SS was transported over 12% of the study period. Rainfall and discharge at the beginning of the events were the most important factors in explaining the hydrological response at event scale. Suspended sediment transport in this catchment is determined by event magnitude, while the SS is mainly influenced by variables related to runoff erosivity.

Aluminum fractionation in acidic soils and river sediments in the Upper Mero basin (Galicia, NW Spain).

This study aims to determine aluminum fractions in the fine earth of acidic soils under different land uses (forest, pasture and cultivation) and in the river bed sediments of the headwater of the Mero River in order to identify and quantify Al-bearing phases to assess Al mobility and potential bioavailability (environmental availability) in the monitoring area. Sequential extraction is used to evaluate the Al partitioning into six fractions operationally defined: soluble/exchangeable/specifically adsorbed, bound to manganese oxides, associated with amorphous compounds, aluminum bound to oxidizable organic matter, associated with crystalline iron oxides, and residual fraction (aluminum within the crystal lattices of minerals). The mean concentration of total aluminum (24.01 g kg-1) was similar for the three considered uses. The mean percentage of the aluminum fractions, both in soils and sediments, showed the following order: residual fraction â‰« amorphous compounds ≈ crystalline iron oxides > water-soluble/exchangeable/specifically adsorbed > bound to oxidizable organic matter ≈ Mn oxides. However, in the soils, the amorphous compounds and water-soluble/exchangeable/specifically adsorbed fraction showed considerable differences between some types of uses, the percentage of aluminum linked to amorphous compounds being higher in forest soils (16% of total Al) compared to other uses (mean about 8% of total Al). The highest values of water-soluble/exchangeable/specifically adsorbed Al were also found in forest soils (mean 8.6% of the total Al versus about 4% of pasture and cultivation), which is consistent with the lower pH and higher organic matter content in forest soils. Nevertheless, the potentially bioavailable fraction (sum of the first three fractions) is low, suggesting very low geoavailability of this element in both soils and sediments; hence, the possibility to affect the crops and water quality is minimal.

Short-term nitrogen losses by overland flow in a recently burnt forest area in north-central Portugal: A study at micro-plot scale.

Over the past decades, wildfires have affected extensive areas of the Mediterranean region with negative impacts on the environment. Most of the studies on fire-affected areas have focused on sediment losses by overland flow, whereas few have addressed post-fire nutrient export. The present study aimed to address this research gap by assessing nitrogen (nitrate and total nitrogen) losses by overland flow in a recently burnt area in north-central Portugal. To this end, three burnt slopes were selected for their contrasting forest types (eucalypt vs. pine) and parent materials (granite vs. schist). The selected study sites were a eucalypt site on granite (BEG), a eucalypt site on schist (BES) and a maritime pine site on schist (BPS). Overland flow samples were collected during the first six months after the wildfire on a 1- to 2-weekly basis, after which this study had to be cancelled due to bench terracing of some of the sites. A peak in total nitrogen concentrations was observed in burnt areas immediately after the first post-fire rainfall event as a response to the erosion of the N-enriched ash layer. After this initial peak, smaller peaks were observed throughout the study period, mainly as a response to overland flow and/or erosion events. Nitrogen export differed strikingly between the two types of forests on schist, being higher at the eucalypt than at the pine site, due to the lack of a protective soil layer. Parent material did not play an important role on nitrogen export by overland flow since no significant differences were found between the eucalypt sites on granite and schist. The present study provides some insight into the differences in post-fire soil fertility losses between forest types and parent materials in the Mediterranean region, which is crucial information for defining post-fire land management measures to reduce soil degradation.

Cation export by overland flow in a recently burnt forest area in north-central Portugal.

The current fire regime in the Mediterranean Basin constitutes a serious threat to natural ecosystems because it drastically enhances surface runoff and soil erosion in the affected areas. Besides soil particles themselves, soil cations can be lost by fire-enhanced overland flow, increasing the risk of fertility loss of the typically shallow and nutrient poor Mediterranean soils. Although the importance of cations for land-use sustainability is widely recognized, cation losses by post-fire runoff have received little research attention. The present study aimed to address this research gap by assessing total exports of Na(+), K(+), Ca(2+) and Mg(2+) in a recently burnt forest area in north-central Portugal. These exports were compared for two types of planted forest (eucalypt vs. maritime pine plantations), two types of parent materials (schist vs. granite) and for two spatial scales (micro-plot vs. hill slope). The study sites were a eucalypt plantation on granite (BEG), a eucalypt plantation on schist (BES) and a maritime pine plantation on schist (BPS). Overland flow samples were collected during the first six months after the wildfire. Cation losses differed strikingly between the two forest types on schist, being higher at the eucalypt than pine site. This difference was evident at both spatial scales, and probably due to the extensive cover of a needle cast from the scorched pine crowns. The role of parent material in cation export was less straightforward as it varied with spatial scale. Cation losses were higher for the eucalypt plantation on schist than for that on granite at the micro-plot scale, whereas the reverse was observed at the hill slope scale. Finally, cation yields were higher at the micro-plot than slope scale, in agreement with the general notion of scaling-effect in runoff generation.

Phosphorus loss from a mixed land use catchment in northwest Spain.

This work examined P loss from a mixed land use catchment in northwest Spain and how it was related to hydrological factors. A stream draining a mixed land use catchment of 16 km in northwest Spain was monitored for 5 yr. Water samples were taken more frequently with increased stream flows. A total of 132 runoff events of different magnitudes were analyzed in this study. Mean annual P loss from the catchment was 11.5 kg km, about 68% being transported during runoff events, which only contributed to 29% of the flow. The contribution of runoff events to particulate P and dissolved P losses was 76 and 46% of total losses during the study period, respectively. A high interannual variability in P loss was observed, the differences being related to rainfall amount and distribution. At a seasonal scale, the highest P loads and concentrations were observed during rainy seasons; the lowest P loads occurred in summer because they occurred with stream flow. Particulate P accounted for the greatest proportion (74%) of transported P. There was a high variability in P transported between runoff events, with maximum discharge and discharge increase being the most important variables explaining total P concentration in these events through their effect on suspended sediment concentration.

Insuficiencia respiratoria aguda debida a mixedema / Acute respiratory failure due to myxedema

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Contrapulsación aórtica. ¿Es posible en los cuidados intensivos de hospitales sin cirugía cardíaca? / Aortic counterpulsation: can it be performed in intensive care units in hospitals without cardiac surgery?

Introducción. El uso de balón de contrapulsación aórtico está habitualmente presente en el ámbito de los servicios de hospitales con cirugía cardíaca. En los enfermos cardíacos complicados con indicación de procedimiento invasivo percutáneo o quirúrgico, se ha demostrado que el uso temprano y preoperatorio de este tipo de soporte mejora los resultados tras la resolución de la situación creada con la cirugía cardíaca pertinente en cada caso. Pacientes y métodos. Se analiza de forma retrospectiva y global a los 9 pacientes que recibieron este tipo de terapia en los primeros 6 meses del año, y se analizan las causas del proceso, las complicaciones presentadas, las técnicas complementarias que recibieron y el resultado final. Resultados. De los 9 pacientes que recibieron esta técnica, dos fallecieron en shock cardiogénico intratable y los otros siete mejoraron de forma inmediata; de estos, dos no necesitaron cirugía cardíaca y los otros cinco fueron intervenidos, con resultados satisfactorios en cuatro de ellos. El traslado de estos pacientes fue posible sin incidencias y con buen resultado. Conclusiones. Si la selección, los cuidados y el seguimiento de los pacientes son adecuados, la contrapulsación aórtica puede proporcionar la estabilidad hemodinámica y la mejoría transitoria a muchos pacientes que precisan un tratamiento quirúrgico o invasor, que puede estar distante temporal y geográficamente (AU)

Shock hemorrágico secundario a úlcera solitaria del recto / Hemorrhagic shock secondary to solitary ulcer of the rectum

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