The long-term impermeability of clay barriers in waste disposal facilities and hydraulic structures is of critical importance to environmental, agricultural, and industrial concerns. Changes in the oxidation state of Fe in the constituent clays of compacted clay barriers may degrade the hydraulic conductivity of these structures because other properties related to hydraulic conductivity, such as swelling, gel microstructure, and particle size, are greatly altered by the oxidation state. Two Na-saturated smectites (SWa-1 and API 25) were reduced by sodium dithionite (Na2S2O4), both in suspension and in situ after consolidation, to examine the effects of structural Fe reduction on hydraulic conductivity. Results indicated that the hydraulic conductivity depended on both the oxidation state and the consolidation history of the clay. The hydraulic conductivity of clay reduced in suspension before consolidation was lower than that of oxidized clay. Initially reduced smectite, thus, may be compactable to a less-permeable material with higher bulk density. But reduction of smectite in situ after consolidation increased the hydraulic conductivity and its variability. The oxidized state of clay liners should, therefore, be preserved.

We present a detailed characterisation of physical properties of low-ionization nuclear emission-line regions (LINERs) and retired galaxies (RGs) in the local universe for redshift range 0 < z < 0.4 and two subranges z < 0.4 and 0.1 < z < 0.4. Furthermore, we test the effectiveness of WHAN diagnostic diagram in separating the two populations. We used photometric data, public spectroscopic data and morphological classification from SDSS-DR8, MPA-JHU SDSS-DR8 catalogue and Galaxy Zoo survey, respectively. We studied the distribution of LINERs, RGs and AGN-LINERs in relation to luminosity, stellar mass, star formation rate (SFR), colour, and their location on the SFR-stellar mass and colour-stellar mass diagrams. We then studied the morphologies of both populations. Results have shown that for higher redshift range, AGN-LINERs have higher apparent g magnitude, SFRs and dominate on/above the main sequence (MS) of star formation compared to RGs. However, both populations have similar stellar mass and luminosity distributions at all redshift ranges hence suggesting a significant difference in terms of star formation of RGs and AGN-LINERs with redshift. However, larger and more complete samples of LINERs are needed from the future surveys (e.g., LSST) and missions (e.g., JWST) to study in more details the properties of RGs and AGN-LINERs and find alternative methods of separating the two populations, since using simply WHAN diagram from our study we do not find it to be effective for separating the two populations.

We study the multiwavelength properties of an optically selected sample of Low Ionization Nuclear Emission-line Regions (LINERs), in an attempt to determine the accretion mechanism powering their central engine. We show how their X-ray spectral characteristics, and their spectral energy distribution compare to luminous AGN, and briefly discuss their connection to their less massive counter-parts galactic black-hole X-ray binaries.

Active galactic nuclei (AGN) are powered by energetic phenomena which cannot be attributed to stars. LINERs appears to be the low power end of the AGN sequence with the lowest Eddington ratios but hosting the most massive black holes (typically 109 M⊙). Whereas variability is common for high Eddington ratio emitting sources, in the low Eddington regime data are not so clear. Recent investigations at UV (Maoz et al. 2005) and X-ray frequencies (Younes et al. 2011, González-Martín et al. 2011) point out to the long term variable nature for some particular LINERs.

In this work we add more evidence about the X-ray variability in LINERs and investigate its nature. The data set comprises X-ray archival spectroscopy from observations taken from Chandra and XMM-Newton, selecting LINERs with several observations at different epochs. Up to now we analysed two LINER 1.9 objects, NGC 1052 and NGC 4278, and checked that variability is due to different mechanisms based on the results of spectral fittings.

Stellar archeology of nearby LINER galaxies may reveal if there is a stellar young population that may be responsible for the LINER phenomenon. We show results for the classical LINER galaxies NGC 4579 and NGC 4736 and find no evidence of such populations.