Worldwide distribution of continental rock lithology: Implications for the atmospheric/soil CO2 uptake by continental weathering and alkalinity river transport to the oceans

The silicate rock weathering followed by the formation of carbonate rocks in the ocean, transfers CO2 from the atmosphere to the lithosphere. This CO2 uptake plays a major role in the regulation of atmospheric CO2 concentrations at the geologic timescale and is mainly controlled by the chemical properties of rocks. This leads us to develop the first world lithological map with a grid resolution of 1 1. This paper analyzes the spatial distribution of the six main rock types by latitude, continents, and ocean drainage basins and for 49 large river basins. Coupling our digital map with the GEM-CO2 model, we have also calculated the amount of atmospheric/soil CO2 consumed by rock weathering and alkalinity river transport to the ocean. Among all silicate rocks, shales and basalts appear to have a significant influence on the amount of CO2 uptake by chemical weatherin

Long range mediated interactions in a mixed dimensional system

We present a mixed-dimensional atomic gas system to unambiguously detect and systematically probe mediated interactions. In our scheme, fermionic atoms are confined in two parallel planes and interact via exchange of elementary excitations in a three-dimensional background gas. This interaction gives rise to a frequency shift of the out-of-phase dipole oscillations of the two clouds, which we calculate using a strong coupling theory taking the two-body mixed-dimensional scattering into account exactly. The shift is shown to be easily measurable for strong interactions and can be used as a probe for mediated interactions.Comment: 7 pages, 5 figure

Flux de CO2 consommé par altération chimique continentale : influences du drainage et de la lithologie = CO2 flux consumed by chemical weathering of continents : influences of drainage and lithology

The flux of atmospheric/soil CO2 consumed by chemical weathering of the continents (FCO2) can be estimated from bicarbonate concentrations in surface water. Using data from the bibliography for 232 small monolithologic watersheds, relationships between FCO2 and the runoff (Q) have been determined For the major rock types outcropping on the continents. The models fitted to these relationships are then applied to the Garonne and Congo river basins, in order to calculate the mean CO2 flux consumed in these basins. The results obtained are close to previous estimates bosed on field measurement

Atmospheric CO2 consumption by continental erosion : present-day controls and implications for the last glacial maximum

The export of carbon from land to sea by rivers represents a major link in the global carbon cycle. For all principal carbon forms, the main factors that control the present-day fluxes at the global scale have been determined in order to establish global budgets and to predict regional fluxes. Dissolved organic carbon fluxes are mainly related to drainage intensity, basin slope, and the amount of carbon stored in soils. Particulate organic carbon fluxes are calculated as a function of sediment yields and of drainage intensity. The consumption of atmospheric/soil CO2 by chemical rock weathering depends mainly on the rock type and on the drainage intensity. Our empirical models yield a total of 0.721 Gt of carbon (Gt C) that is exported from the continents to the oceans each year. From this figure, 0.096 Gt C come from carbonate mineral dissolution and the remaining 0.625 Gt C stem from the atmosphere (FCO2). Of this atmospheric carbon, 33% is discharged as dissolved organic carbon, 30% as particulate organic carbon, and 37% as bicarbonate ions. Predicted inorganic carbon fluxes were further compared with observed fluxes for a set of 35 major world rivers, and possible additional climatic effects on the consumption of atmospheric CO2 by rock weathering were investigated in these river basins. Finally, we discuss the implications of our results for the river carbon fluxes and the role of continental erosion in the global carbon cycle during the last glacial maximum

Territorial thinking and the legal framework in cross-border cooperation : the recent situation and fieldwork results in the western alps.

In this article we discuss the following questions: what is the key to cross-border cooperation, particularly in the case of European mountain regions? Does the legal framework represent a starting point for the development of cross-border relations or is it just a simple tool in the service of territorial thinking? If we consider that there is a strong link between cross-border relations and the European project, the above questions also raise the issue of the relative roles of the bottom-up and top-down processes in the dynamics of European integration. Results suggest that the legal framework represents an indispensable tool in the service of territorial thinking but it cannot be a starting point for the development of cross-border relations. The solutions do not only concern the law but also territory; the essential question is how to define the social, political and spatial boundaries of cross-border cooperation

Impact of nitrogen fertilizers on the natural weathering-erosion processes and fluvial transport in the Garonne basin

Knowledge of the impact of N-fertilizers on the weathering-erosion processes of soils in intensively cultivated regions is of prime importance. Nitrification of NH4− fertilizers produces HNO3 in the basin of the Garonne river, enhancing soil degradation. Their influence on the weathering rates was determined by calculating the consumption rate of atmospheric/soil CO2 by soil weathering and erosion, and its contribution to the total dissolved riverine HCO3−. This contribution was found to be less than 50% which corresponds normally to a complete carbonate dissolution by carbonic acid, suggesting that part of the alkalinity in the river waters is due to carbonate dissolution by an acid other than carbonic acid, probably HNO3

Enhanced chemical weathering of rocks during the last glacial maximum: a sink for atmospheric CO2?

It has been proposed that increased rates of chemical weathering and the related drawdown of atmospheric CO2 on the continents may have at least partly contributed to the low CO2 concentrations during the last glacial maximum LGM.. Variations in continental erosion could thus be one of the driving forces for the glacialrinterglacial climate cycles during Quaternary times. To test such an hypothesis, a global carbon erosion model has been applied to a LGM scenario in order to determine the amount of CO2 consumed by chemical rock weathering during that time. In this model, both the part of atmospheric CO2 coming from silicate weathering and the part coming from carbonate weathering are distinguished. The climatic conditions during LGM were reconstructed on the basis of the output files from a computer simulation with a general circulation model. Only the predicted changes in precipitation and temperature have been used, whereas the changes in continental runoff were determined with an empirical method. It is found that during the LGM, the overall atmospheric CO2 consumption may have been greater than today by about 20%., mainly because of greater carbonate outcrop area related to the lower sea level on the shelves. This does not, however, affect the atmospheric CO2 consumption by silicate weathering, which alone has the potential to alter atmospheric CO2 on the long-term. Silicate weathering and the concomitant atmospheric CO2 consumption decreased together with a global decrease of continental runoff compared to present-day both by about 10%.. Nevertheless, some uncertainty remains because the individual lithologies of the continental shelves as well as their behavior with respect to chemical weathering are probably not well enough known. The values we present refer to the ice-free continental area only, but we tested also whether chemical weathering under the huge ice sheets could have been important for the global budget. Although glacial runoff was considerably increased during LGM, weathering under the ice sheets seems to be of minor importance

d13C pattern of dissolved inorganic carbon in a small granitic catchment: the Strengbach case study (Vosges mountains, France)

The transfers and origins of dissolved inorganic carbon DIC. were studied for a year in a soil–spring–stream system in the Strengbach catchment, Vosges mountains, France. This 80 ha experimental research basin is located on the eastern side of the mountains, at an altitude ranging from 883 to 1146 m.a.s.l. and is mainly covered by spruce 80%.. Brown acid and podzolic soils developed on a granitic basement, and, as a result, the DIC originates solely from CO2 generated by oxidation of soil organic matter. The d13CDIC. in catchment waters is highly variable, from about y22‰ in the springs and piezometers to about y12‰ in the stream at the outlet of the catchment. In the springs, pronounced seasonal variations of d13C exist, with the DIC in isotopic equilibrium with the soil CO that has estimated d13DIC 2 C of about y24‰ in winter and y20‰ in summer. These seasonal variations reflect an isotopic fractionation that seems only induced by molecular diffusion of soil CO2 in summer. In stream water, seasonal variations are small and the relatively heavy DIC y12‰ on average. is a result of isotopic equilibration of the aqueous CO2 with atmospheric CO2

An electronic ratchet is required in nanostructured intermediate band solar cells

We investigate in this letter the intrinsic properties that have limited the efficiency of nanostructured intermediate band solar cells. Those devices take advantage of intra-band transitions, which occur on narrow energy width, and present low radiative recombination efficiency. We derive the minimum requirements in terms of those two characteristics to achieve efficiencies in excess of the Shockley-Queisser limit, and show that compatible nanostructures are challenging to obtain. Especially, we evidence that currently experimentally considered materials cannot overcome the best single junction cells. In order to solve those issues, we consider devices including an electronic ratchet mechanism. Firstly, such devices are shown to be much less sensitive on the limitations of the nanostructures characteristics, so that requirements for high efficiencies can be met. Secondly, we show that quantum well devices present advantages over their quantum dots counterparts, although they have attracted much less interest so far