Pore Size-Dependent Structure of Confined Water in Mesoporous Silica Films from Water Adsorption/Desorption Using ATR-FTIR Spectroscopy.

The local structure of water on chemically and structurally different surfaces is a subject of ongoing research. In particular, confined spaces as found in mesoporous silica have a pronounced effect on the interplay between the adsorbate-adsorbate and adsorbate-surface interactions. Mid-infrared spectroscopy is ideally suited to quantitatively and qualitatively study such systems as the probed molecular vibrations are highly sensitive to intermolecular interactions. Here, the quantity and structure of water adsorbed from the gas phase into silica mesopores at different water vapor pressures was monitored using mid-infrared attenuated total reflection (ATR) spectroscopy. Germanium ATR crystals were coated with different mesoporous silica films prepared by evaporation-induced self-assembly. Quantitative analysis of the water bending vibration at 1640 cm-1 at varying vapor pressure allows for retrieving porosity and pore size distribution of the mesoporous films. The results were in excellent agreement with those obtained from ellipsometric porosimetry. In addition, different degrees of hydrogen bonding of water as reflected in the band position and shape of the stretching vibrations (3000-3800 cm-1) were analyzed and attributed to high-density, unordered bulk, low-density, and surface-induced ordered water. Thereby, the progression of surface-induced ordered water and bulk water as a function of water vapor pressure was studied for different pore sizes. Small pores of 5 nm diameter showed a number of two-ordered monolayers, whereas for pores >12 nm diameter, the number of ordered monolayers is significantly larger and agrees with the number observed on planar SiO2 surfaces.

Assessing the impact of inland navigation on the faecal pollution status of large rivers: A novel integrated field approach.

The contribution of ships to the microbial faecal pollution status of water bodies is largely unknown but frequently of human health concern. No methodology for a comprehensive and target-orientated system analysis was available so far. We developed a novel approach for integrated and multistage impact evaluation. The approach includes, i) theoretical faecal pollution source profiling (PSP, i.e., size and pollution capacity estimation from municipal vs. ship sewage disposal) for impact scenario estimation and hypothesis generation, ii) high-resolution field assessment of faecal pollution levels and chemo-physical water quality at the selected river reaches, using standardized faecal indicators (cultivation-based) and genetic microbial source tracking markers (qPCR-based), and iii) integrated statistical analyses of the observed faecal pollution and the number of ships assessed by satellite-based automated ship tracking (i.e., automated identification system, AIS) at local and regional scales. The new approach was realised at a 230 km long Danube River reach in Austria, enabling detailed understanding of the complex pollution characteristics (i.e., longitudinal/cross-sectional river and upstream/downstream docking area analysis). Faecal impact of navigation was demonstrated to be remarkably low at regional and local scale (despite a high local contamination capacity), indicating predominantly correct disposal practices during the investigated period. Nonetheless, faecal emissions were sensitively traceable, attributable to the ship category (discriminated types: cruise, passenger and freight ships) and individual vessels (docking time analysis) at one docking area by the link with AIS data. The new innovative and sensitive approach is transferrable to any water body worldwide with available ship-tracking data, supporting target-orientated monitoring and evidence-based management practices.

First report on the occurrence of Vibrio cholerae nonO1/nonO139 in natural and artificial lakes and ponds in Serbia: Evidence for a long-distance transfer of strains and the presence of Vibrio paracholerae.

Vibrio cholerae are natural inhabitants of specific aquatic environments. Strains not belonging to serogroups O1 and O139 are usually unable to produce cholera toxin and cause cholera. However, non-toxigenic V. cholerae (NTVC) are able to cause a variety of mild-to-severe human infections (via seafood consumption or recreational activities). The number of unreported cases is considered substantial, as NTVC infections are not notifiable and physicians are mostly unaware of this pathogen. In the northern hemisphere, NTVC infections have been reported to increase due to global warming. In Eastern Europe, climatic and geological conditions favour the existence of inland water-bodies harbouring NTVC. We thus investigated the occurrence of NTVC in nine Serbian natural and artificial lakes and ponds, many of them used for fishing and bathing. With the exception of one highly saline lake, all investigated water-bodies harboured NTVC, ranging from 5.4 × 101 to 1.86 × 104  CFU and 4.5 × 102 to 5.6 × 106 genomic units per 100 ml. The maximum values observed were in the range of bathing waters in other countries, where infections have been reported. Interestingly, 7 out of 39 fully sequenced presumptive V. cholerae isolates were assigned as V. paracholerae, a recently described sister species of V. cholerae. Some clones and sublineages of both V. cholerae and V. paracholerae were shared by different environments indicating an exchange of strains over long distances. Important pathogenicity factors such as hlyA, toxR, and ompU were present in both species. Seasonal monitoring of ponds/lakes used for recreation in Serbia is thus recommended to be prepared for potential occurrence of infections promoted by climate change-induced rise in water temperatures.