In this paper we present high resolution atomic force microscopy (AFM) images of dolomite (104) cleavage surfaces immersed in pure water. These images show a rectangular lattice with surface unit cell dimensions in general agreement with those derived from the dolomite bulk structure. Furthermore, the two dimensional fast Fourier transform (20-FFT) plots of the high resolution images exhibit a pattern of periodicities consistent with both the alternate orientation of the carbonate groups and the positions for calcium and magnesium atoms on the dolomite (104) surface. However, the Mt+ and Ca2+ sublattices could not be resolved. Finally, the images in both the real and the Fourier space do not reveal any clear evidence of reconstruction of the dolomite (104) surfaces.
During July 2016, the first integrated heat flow, CO2, and 3He emission survey was conducted across 0.5 km2 of the summit cone and crater of Teide volcano, Tenerife, Canary Islands, Spain. The thermal energy released from Teide summit cone by diffuse degassing was 2.2 MW, and the heat flux calculated through Dawson’s method was 8.1 MW, difference due to the comparison of purely convective areas as the crater with diffusive areas as the flanks of the volcano. Diffuse CO2 output was 211±20 t d-1, and 3He emission was estimated to be within a range between 0.35 and 0.89 mol y-1. The obtained values of diffuse degassing and heat fluxes are close to others obtained for similar volcanic areas. The calculation of 3He/heat ratio for the first time in this volcanic system supports the presence of an important mantle source for the degassing of Teide volcano.
<p>Methane (CH<sub>4</sub>) is an important greenhouse gas, and is increasing in the atmosphere by 0.6% (10 ppb) each year. Important sources of this gas are landfills; in fact more than 10% of the total anthropogenic emissions of CH<sub>4</sub> are originated in them by anaerobic degradation of organic matter. Even after years of being closed, a significant amount of landfill gas can be released to the atmosphere through its surface as diffuse or fugitive degassing.</p><p>Many landfills currently report their CH<sub>4</sub> emissions to the atmosphere using model-based methods, which are based on the rate of production of CH<sub>4</sub>, the oxidation rate of CH<sub>4</sub> and the amount of CH<sub>4</sub> recovered (Bingemer and Crutzen, 1987). This approach often involves large uncertainties due to inaccuracies of input data and many assumptions in the estimation. In fact, the estimated CH<sub>4</sub> emissions from landfills in the Canary Islands published by the Spanish National Emission and Pollutant Sources Registration (PRTR-Spain) seem to be overestimated due to the use of protocols and analytical methodologies based on mathematical models. For this reason, direct measurements to estimate CH<sub>4</sub> emissions in landfills are essential to reduce this uncertainty.</p><p>In order to estimate the CH<sub>4</sub> emissions to the atmosphere from landfills in the Canary Islands, 34 surveys have been performed since 1999 to the present. Each survey implies hundreds of CO<sub>2 </sub>and CH<sub>4</sub> efflux measurements covering the landfill surface area. Surface landfill CO<sub>2</sub> efflux measurements were carried out at each sampling site by means of a portable non-dispersive infrared spectrophotometer (NDIR) model LICOR Li800 following the accumulation chamber method. Samples of landfill gases were taken in the gas accumulated in the chamber and CO<sub>2</sub> and CH<sub>4</sub> were analyzed using a double channel VARIAN 4900 micro-GC. The CH<sub>4</sub> efflux measurement was computed combining CO<sub>2</sub> efflux and CH<sub>4</sub>/CO<sub>2</sub> ratio. To quantify the diffuse or fugitive CO<sub>2</sub> and CH<sub>4</sub> emission, gas efflux contour maps were constructed using sequential Gaussian simulation (sGs) as interpolation method. Considering that (a) there are 6 controlled landfills in the Canary Islands, (b) the average area of the 34 studied cells is 0.15 km<sup>2</sup> and (c) the mean value of the CH<sub>4</sub> emission estimated for the studied cells range between 6.2 and 7.2 kt km<sup>-2</sup> y<sup>-1</sup>, the estimated CH<sub>4</sub> emission to the atmosphere from landfills in the Canary Islands showed a range of 5.7-6.7 kt y<sup>-1</sup> (mean value of 6.2 kt y<sup>-1</sup>). On the contrary, and for the same period of time, the PRTR-Spain estimates the CH<sub>4</sub> emission in the order of 6.4-16.4 kt y<sup>-1</sup> (mean value of 9.2 kt y<sup>-1</sup>), nearly 46% more than our estimated value. This result demonstrates the need to perform direct measurements to estimate the surface fugitive emission of CH<sub>4</sub> from landfills.</p><p><em>Bingemer, H. G., and P. J. Crutzen (1987), J. Geophys. Res. 92, 2182-2187.</em></p>
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