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Abstract. The hydrogeological characteristics of rototranslational slides in flysch are complex, due to the inherent anisotropy and heterogeneity of rock masses and related deposits. The paper deals with the hydrogeological characterization of a reactivated roto-translational slide affecting Cretaceous flysch rocks, located in the northern Apennines of Italy. Continuous monitoring of groundwater levels, in-situ permeability and pumping tests, hydrochemical and physical analyses and Uranine tracers were the adopted prospecting methods.In this research hydrological monitoring and investigation are summarized in order to define a hydrogeological conceptual model of the landslide source area. Results showed that two overlaying hydrogeological units exist at the slope scale: the first is unconfined, but highly compartmentalized, and hosted in the fractured and dismembered rock slide body. The second is confined and lays in the undisturbed flysch below the sliding surface. The groundwater level in the confined hydrogeological unit is twenty meters higher than the groundwater level in the uppermost one. Moreover, the groundwater chemistry characterization revealed a rising of deep fluids in the landslide area.

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A method is described for the determination of mercury at nanogram levels in geological materials by flameless atomic absorption spectroscopy after metal vapor generation. Mercury is converted to a soluble form by H2SO4‐HNO3 attack in a teflon bomb at 180°C for 90 minutes. Metal Hg vapor is obtained by reaction with combined NaBH4‐NaOH using the Perkin‐Elmer MHS ‐ 10 hydride system and determined at room temperature. Mercury can be easily determined in most silicate materials. The sensitivity of the method depends essentially on the purity of the reagents and contaminations during handling rather than on instrumental capabilities. A detection limit of about 10 ng/g Hg for 0.5 g samples has been achieved with the use of normal “suprapure” reagents. Mercury contents on some USGS, CRPG and ANRT reference samples are reported.

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Rn-222 and total helium contained in saline waters and associated gaseous fluids from a series of mud volcanoes occurring along the northeastern border of the Apennine chain (northern Italy) have been determined as possible precursors of local earthquakes. Investigations spanned over about one year (May 1986-May 1987 during which a series of low to medium-magnitude (M = 3-4.5) local earth quakes occurred with distinct focus. Spike-like Rn anomalies were almost systematically observed a short time (hours to few days) before and after the main shocks. These anomalies were frequently accom panied by slight but significant short-term changes in water chemistry. A unique very strong He anomaly was recorded in coincidence with a shock in an area very close to the focus. The significance of the ob served short-term anomalies of Rn and hydrochemical parameters (chlorinity, alkaline earths content) is explained in terms of an upsetting of the equilibrium between two chemically distinct (pellicular and nor mal) connate waters in confined reservoirs. Pellicular water trapping radiogenic Rn would be abruptly liberated into normal connate water by a tectonic stress change. In most cases, helium seems to be insen sitive to seismic events, this probably being due to the shallowness of the foci. The data confirm that mud volcanoes represent very sensitive natural systems for predicting local earthquakes.

Precious metals (Ag, Au, Pt, Pd, Rh) were determined by flameless absorption atomic spectrornetry. Aqua regia sample decomposition followed by Te coprecipitation was employed to preconcentrate the precious metals in geological materials. With 5 g sample take‐up, the limits of determination were 1‐2 ppb for Au, Pd and Rh, 5 ppb for Ag and 10‐20 ppb for Pt. These elements were determined in some geochemical standards.