In this paper, research on the possibilities of sodium sulphate (Na2SO4) separation from other substances in the filter ash sample is presented. The research material contains six components that differ in chemical composition and density. The possibilities of Na2SO4 separation using dry and wet methods were studied. The dry method was based on separation with a centrifugal air classifier at four cut size limits. The wet method was based on the dissolution of water-soluble components, filtration of insoluble components, and drying the products. The sulphur content of the individual products was determined using both methods. The aim of the research was to determine which method is more suitable for separation of the material in a way that most of the material would contain as little sulphur as possible and the rest of the material would contain concentrated sulphur. The wet method proved to be more successful. The product with mass fraction 33.1% of the total mass, obtained from the aqueous solution, contained 8.39% sulphur after filtration and drying. The water-insoluble component, with mass fraction 66.9% of the total mass, contained 0.56% sulphur. The dry method with the centrifugal air classifier proved to be less successful in comparison with the wet method. The particles containing Na2SO4 are very similar in size and density to the other components of the material, so the separation to the desired extent was not achieved.
In this study, we estimate vertical land motion for 35 stations primarily located along the coastline of Portugal and Spain, using GPS time series with at least eight years of observations. Based on this set of GPS stations, our results show that vertical land motion along the Iberian coastline is characterized, in general, by a low to moderate subsidence, ranging from −2.2 mm yr−1 to 0.4 mm yr−1, partially explained by the glacial isostatic adjustment geophysical signal. The estimates of vertical land motion are subsequently applied in the analysis of tide gauge records and compared with geocentric estimates of sea level change. Geocentric sea level for the Iberian Atlantic coast determined from satellite altimetry for the last three decades has a mean of 2.5 ± 0.6 mm yr−1, with a significant range, as seen for a subset of grid points located in the vicinity of tide gauge stations, which present trends varying from 1.5 mm yr−1 to 3.2 mm yr−1. Relative sea level determined from tide gauges for this region shows a high degree of spatial variability, that can be partially explained not only by the difference in length and quality of the time series, but also for possible undocumented datum shifts, turning some trends unreliable. In general, tide gauges corrected for vertical land motion produce smaller trends than satellite altimetry. Tide gauge trends for the last three decades not corrected for vertical land motion range from 0.3 mm yr−1 to 5.0 mm yr−1 with a mean of 2.6 ± 1.4 mm yr−1, similar to that obtained from satellite altimetry. When corrected for vertical land motion, we observe a reduction of the mean to ∼1.9 ± 1.4 mm yr−1. Actions to improve our knowledge of vertical land motion using space geodesy, such as establishing stations in co-location with tide gauges, will contribute to better evaluate sea level change and its impacts on coastal regions.