Utilizing Colored Dissolved Organic Matter to Derive Dissolved Black Carbon Export by Arctic Rivers

Wildfires have produced black carbon (BC) since land plants emerged. Condensed aromatic compounds, a form of BC, have accumulated to become a major component of the soil carbon pool. Condensed aromatics leach from soils into rivers, where they are termed dissolved black carbon (DBC). The transport of DBC by rivers to the sea is a major term in the global carbon and BC cycles. To estimate Arctic river DBC export, 25 samples collected from the six largest Arctic rivers (Kolyma, Lena, Mackenzie, Ob’, Yenisey and Yukon) were analyzed for dissolved organic carbon (DOC), colored dissolved organic matter (CDOM), and DBC. A simple, linear regression between DOC and DBC indicated that DBC accounted for 8.9 ± 0.3% DOC exported by Arctic rivers. To improve upon this estimate, an optical proxy for DBC was developed based upon the linear correlation between DBC concentrations and CDOM light absorption coefficients at 254 nm (a254). Relatively easy to measure a254 values were determined for 410 Arctic river samples between 2004 and 2010. Each of these a254 values was converted to a DBC concentration based upon the linear correlation, providing an extended record of DBC concentration. The extended DBC record was coupled with daily discharge data from the six rivers to estimate riverine DBC loads using the LOADEST modeling program. The six rivers studied cover 53% of the pan-Arctic watershed and exported 1.5 ± 0.1 million tons of DBC per year. Scaling up to the full area of the pan-Arctic watershed, we estimate that Arctic rivers carry 2.8 ± 0.3 million tons of DBC from land to the Arctic Ocean each year. This equates to ~8% of Arctic river DOC export, slightly less than indicated by the simpler DBC vs DOC correlation-based estimate. Riverine discharge is predicted to increase in a warmer Arctic. DBC export was positively correlated with river runoff, suggesting that the export of soil BC to the Arctic Ocean is likely to increase as the Arctic warms

Finitud y duración

Este artículo presenta una articulación de las ideas de duración, cosmicidad, proximidad y finitud a modo de puntos definidores de un ethos cercano al de la sostenibilidad y contrapuesto al Gestell heideggeriano de la técnica moderna, al nihilismo indistante del consumismo y a la retórica de la innovación tecnológica

Hannah Arendt y el totalitarismo: Implicaciones para una teoría política

El centro del pensamiento político de Hannah Arendt lo ocupa el concepto de acción, que se identifica con la capacidad humana de comenzar, de empezar algo nuevo. Junto a este concepto e interrelacionándose con él podemos encontrar los de novedad, nacimiento, pluralidad, espacio publico, pensamiento, mal ... La finalidad de este artículo consiste en mostrar cómo la mayoría de estos conceptos se forjan ya en los análisis de Arendt sobre el totalitarismo. La «lógica» totalitaria conduce, precisamente, a la anulación de la pluralidad y de la diversidad humanas, de la acción y del pensmiento, de la [(polis~y del .mundo

Philosophy as attentive gaze

There is something unusual, even paradoxical, about the way that we look at the world around us: the utter ease of looking contrasts with the difficulty of performing the same act well. If there is light, we just open our eyes and the things around us appear. In contrast, we must pay attention to become aware of certain aspects of reality and, in particular, to perceive things in a different way. Simply seeing, mere visual perception, involves virtually no effort (hence, for example, the success of television and screens in general), but looking with care is harder: directing our gaze and concentrating on something involves an effort and can therefore be tiring. The attentive gaze is more uncommon than we might expect. What is it that attention adds to the gaze to transform it in such a significant way? Why does the effort of directing our attention imply much more than a simple zoom effect? Philosophical gaze and attentive gaze is the same thing

Finitud y duración

Este artículo presenta una articulación de las ideas de duración, cosmicidad, proximidad y finitud a modo de puntos definidores de un ethos cercano al de la sostenibilidad y contrapuesto al Gestell heideggeriano de la técnica moderna, al nihilismo indistante del consumismo y a la retórica de la innovación tecnológica.This paper presents an articulation of the ideas of duration, cosmicity, proximity and finitude as the defining features of an ethos close to that of sustainability, and contrary to the heideggerian Gestell of modern technique, to the nihilism undistant from consumerism and the rhetoric of technological innovation

Comparison of Engineering Wake Models with CFD Simulations

The engineering wake models by Jensen [1] and Frandsen et al. [2] are assessed for different scenarios simulated using Large Eddy Simulation and the Actuator Line method implemented in the Navier-Stokes equations. The scenarios include the far wake behind a single wind turbine, a long row of turbines in an atmospheric boundary layer, idealised cases of an infinitely long row of wind turbines and infinite wind farms with three different spacings. Both models include a wake expansion factor, which is calibrated to fit the simulated wake velocities. The analysis highlights physical deficiencies in the ability of the models to universally predict the wake velocities, as the expansion factor can be fitted for a given case, but with not apparent transition between the cases. 1