Environmental policy and decision-making are characterized by complex interactions between different actors and sectors. As a rule, a stakeholder analysis is performed to understand those involved, but it has been criticized for lacking quality and consistency. This lack is remedied here by a formal social network analysis that investigates collaborative and multi-level governance settings in a rigorous way. We examine the added value of combining both elements. Our case study examines infrastructure planning in the Swiss water sector. Water supply and wastewater infrastructures are planned far into the future, usually on the basis of projections of past boundary conditions. They affect many actors, including the population, and are expensive. In view of increasing future dynamics and climate change, a more participatory and long-term planning approach is required. Our specific aims are to investigate fragmentation in water infrastructure planning, to understand how actors from different decision levels and sectors are represented, and which interests they follow. We conducted 27 semi-structured interviews with local stakeholders, but also cantonal and national actors. The network analysis confirmed our hypothesis of strong fragmentation: we found little collaboration between the water supply and wastewater sector (confirming horizontal fragmentation), and few ties between local, cantonal, and national actors (confirming vertical fragmentation). Infrastructure planning is clearly dominated by engineers and local authorities. Little importance is placed on longer-term strategic objectives and integrated catchment planning, but this was perceived as more important in a second analysis going beyond typical questions of stakeholder analysis. We conclude that linking a stakeholder analysis, comprising rarely asked questions, with a rigorous social network analysis is very fruitful and generates complementary results. This combination gave us deeper insight into the socio-political-engineering world of water infrastructure planning that is of vital importance to our well-being.

Several 2:1 layer silicates comprising di- and trioctahedral smectites of different layer charge between 0.2 and 0.4 per formula unit and a trioctahedral vermiculite were studied by an method that allowed Fourier transform infrared spectroscopy (FTIR) spectra and water vapor sorption isotherms to be obtained simultaneously. The particle size and shape of the selected materials were determined using X-ray diffraction and gas adsorption analyses, which provided an estimate of the particle size with resulting edge site proportion. The aim of this study was to elucidate the hydration mechanism in 2:1 layer silicates during desorption and adsorption of water vapor. Domains in the desorption and adsorption of water vapor of the smectite samples with a slightly increasing slope were explained by a heterogeneous layer charge distribution, which enables the coexistence of different hydration states even under controlled conditions. Whereas hysteresis was observed over the entire isothermal range of the smectites, the isotherm of the vermiculite sample only showed hysteresis in the transition from the monohydrated state (1W) to the bihydrated state (2W). We also revealed that hysteresis is a function of the layer charge distribution, the achieved water content, and the particle size with resulting edge site contribution. Increasing the edge site proportions led to an increased hysteresis. The findings from the experimental FTIR/gravimetric analysis showed that the transition from 2W to 1W and backward is visible using infrared spectroscopy. The shifting of (H-O-H) was influenced by the layer charge and octahedral substitutions. As a final point, we use water as a sensor molecule to describe the OH groups of the octahedral sheet and show that the observed shifts result from a change in the tilting angle. Our experimental results were supported by thermodynamic simulations that revealed the different shifting behavior of (H-O-H) and(M -OH-N) related to the differences in surface charge density and octahedral compositions.

The coupled processes of (de-)hydration and structural changes of a well characterized Na + -exchanged dioctahedral smectite with a low layer charge (0.26 mol(+) / formula unit) was studied by in situ transmission Fourier Transform Infrared Spectroscopy. Therefore, a sample preparation technique based on the Tethering by aggregation and growth method is extended to clay minerals to obtain a thin film of montmorillonite on a silicon wafer. After equilibration of the sample at 53% relative humidity infrared measurements were done with a custommade, heatable sample holder in an oxygen free atmosphere under N 2 purging which allowed subsequent FTIR measurements. Using a very thin film, deviation of the Si-O phonon modes could be simultaneously studied with the vibrational modes of water. The structural changes in the 2:1 layer of the montmorillonite during dehydration can be recognized from the shift of longitudinal optical Si-O phonon mode. The accompanied decrease and shift of the bending vibration of water δ(H-O-H) to lower wavenumbers is correlated to an increase of watersurface attraction. Finally, our experimental results were supported by ab initio thermodynamic simulations that revealed a decrease of the b 0 from 9.18 Å to 8.98 Å.

Properties of swellable clay minerals in technical and geotechnical applications as well as in geological systems are determined by their water content. Thereby, the water content depends on the structure and morphology of the smectites and available water while smectites are the most heterogeneous clay minerals. Here, first-principles calculations are combined with ab initio thermodynamics to systematically study the hydration states of Na-saturated dioctahedral smectites. Total energy calculations based on density functional theory are carried out for a series of montmorillonites and beidellites with varying layer charge (0.125 ≤ ξ ≤ 0.5) and increasing number of water molecules per unit cell. The thermodynamic ground state was then defined with the help of the grand canonical potential as a function of chemical potential of water, which is directly related to the experimental conditions of pressure and temperature. For the first time, p,T-phase diagrams of stable hydration states together with relative humidity curves are shown. In the discussion, deviation of measured water contents is explained by the contribution of layer charge distribution, hydration of cations at the layer edges, and osmosis in mesopores at the edges of layer stacks. In addition, we showed that dioctahedral 2:1 layer silicates with a layer charge of 0.125 are swellable, which reduces the definition gap between uncharged and charged 2:1 layer silicates.

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