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Knowledge of spring waters’ chemical composition is paramount for both their use and their conservation. Vast surveys at the basin scale are required to define the nature and the location of the springs and to identify the hydrochemical facies of their aquifers. The present study aims to evaluate the hydrochemical facies and the vulnerability to nitrates of 59 springs falling in the Sila Massif in Calabria (southern Italy) and to identify their vulnerability through the analysis of physicochemical parameters and the use of the Langelier–Ludwig diagram. A spatial analysis was performed by the spline method. The results identified a mean value of 4.39 mg NO3−/L and a maximum value of 24 mg NO3−/L for nitrate pollution in the study area. Statistical analysis results showed that the increase in electrical conductivity follows the increase in alkalinity values, a correlation especially evident in the bicarbonate Ca-Mg waters and linked to the possibility of higher nitrate concentrations in springs. These analyses also showed that nitrate vulnerability is dependent on the geological setting of springs. Indeed, the Sila igneous–metamorphic batholith, often strongly affected by weathering processes, contributes to not buffering the nitrate impacts on aquifers. Conversely, anthropogenic activities, particularly fertilization practices, are key factors in groundwater vulnerability.

The analysis of the rheological properties of the sludge produced in biological purification plants is paramount for the design of equipment (pumping, mixing, conditioning, aeration, filtration, etc.) and the management of these plants. In particular, solid content in the sludge plays a significant role in the rheological quantities. In this study, an investigation of the sludge rheology produced in different sectors of an activated sludge plant (aerated sludge, recirculation sludge, and thickened sludge) has been performed. Specifically, for each sludge sample, various physical-chemical parameters have been analyzed, and rheological tests have been performed at different temperatures (10°C, 20°C, 30°C, and 40°C ± 0.1). The sludge was considered as a non-Newtonian Bingham fluid. Viscosity and critical stress were determined, and their dependence at different temperatures, on some physical parameters, such as solid content and settling solids, has been studied. Results evidenced that viscosity and critical stress increase with increasing solid concentration. Moreover, at the same concentration, as the temperature increases, the viscosity decreases, whereas the critical stress decreases until temperature values of about 30°C and then increases again. PRACTITIONER POINTS: An investigation of the sludge rheology produced in different sectors of an activated sludge plant has been performed. For each sludge sample, various physical-chemical parameters have been analyzed, and rheological tests have been performed at different temperatures. Viscosity and critical stress were determined, and their dependence at different temperatures, on some physical parameters, has been studied. Results evidenced that viscosity and critical stress increase with increasing solid concentration.

In this work, we present an experimental study on the re-aeration of a biological effluent coming from a wastewater treatment plant located at sea level. The oxygen transfer efficiency has been calculated for a hydraulic structure characterized by three different weirs jumps (Bazin type). The experimental results have been compared with those obtained by two (and well known) empirical equations (Avery-Novak equation (Avery and Novak, 1978) and Thene equation (Thene, 1988)). These equations did not allow a well fitting of the experimental data. We proposed a modification of the Thene equation by inserting of the Weber number of the jet. By this new correlation, we obtained a good fitting of re-aeration data obtained for the studied hydraulic structure.

This work aims to improve the knowledge of nutrient exchanges between soil and atmosphere through a comparative analysis of the contribution coming from atmospheric depositions and their release in water runoff. The study has been realized on a mountain catchment, crossed by Bonis stream, tributary of Cino river and located in Sila Greca plateau (Calabria, Southern Italy). This experimental basin, laying on a basement formed by inclusive and plutonic rocks, extends for an area of 139 hectares, spreading from 975 m a.s.l. to 1301 m a.s.l. The catchment is forested for about 95% of its surface area with the main presence of Pinus laricio Poiret populations differentiated for age, density, tree canopy cover and stand characteristics within an area without human settlements and pollution sources. The basin has been instrumented, since 1986, to measure the main abiotic features in inflow and outflow discharges. These chemical and physical parameters, as N-NH4, N-NO2, N-NO3, P-PO4, S-SO4, Cl, pH and conductivity, have been analyzed on a fortnightly basis. From collected data, it has been estimated, for each nutrient, its annual and monthly mean weighed concentrations to value the basin resilience after external inputs and its rolling action after some events, as acid depositions. In conclusion, the monitoring of mountain catchments could supply useful data about the global changes of atmospheric chemistry and, as a consequence, on the variability in quality control of surface waters, considering that mountain catchments supply most of water resources of a good quality level for mankind.

We present the results of high-resolution electron energy loss experiments on (CO/O)/Ni(1 0 0) and (CO/H)/Ni(1 0 0) systems. Oxygen and hydrogen interact differently with Ni(1 0 0) surface, nevertheless, both species do not affect to a great extent the vibrational properties of CO. A phase of CO molecules weakly bonded to the surface and unaffected by coadsorbed oxygen and hydrogen, is found. Coverage of 0.5 ML of predosed oxygen chemically passivates the Ni(1 0 0) surface and inhibits any CO adsorption at room temperature. CO sites are unambiguously determined for each predosed Ni(1 0 0) surface.