The local structure of water on chemically and structurally different surfaces is subject of ongoing research. In particular, confined spaces as found in mesoporous silica have a pronounced effect on the interplay between 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 allowed 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 (3000-3750 cm-1) were analyzed and attributed to high-density, unordered bulk and low-density, 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 with 5 nm diameter showed a number of two ordered monolayers, while for pores > 12 nm the number of ordered monolayers is significantly larger and agrees with the number observed on planar SiO2 surfaces.
Recent developments in water resource monitoring have increased the demand for the reliable identification of faecal pollution sources, also defined as microbial (faecal) source tracking (MST). Standardized faecal indicator bacteria (SFIB) enumeration does not directly support MST, as SFIB occur in animal and human sources. The aim of this study was to rigorously evaluate the applicability of host-associated faecal genetic MST markers detected by quantitative PCR (qPCR) at representative Austrian water resources (ground-, surface-, raw and treated wastewater, n = 196 samples) with high importance for the water management sector. Groundwater covered a gradient of non- (i.e., deep wells) to surface influenced resources (i.e., karst and shallow wells). In addition, single faecal excreta from humans as well as representative livestock and wildlife species were collected to evaluate the faecal source-specificity and -sensitivity of the MST assays. Genetic MST marker resistance against UV irradiation was evaluated in on-site ground and wastewater treatment installations. Bacteroides-based human- (HF183II, BacHum), ruminant- (BacR), and pig-associated (Pig2Bac) MST marker qPCR quantification was performed in concert with cultivation of E. coli, intestinal enterococci, and Clostridium perfringens (SFIB diagnostics). The selected MST makers revealed high faecal source identification capacity for the Austrian water compartments and quantitatively reflected the selected faecal pollution gradient. The study also demonstrated that SFIB data can efficiently be combined with MST data to solve previously unanswered questions in water safety monitoring and management (e.g., support pollution source-targeted catchment protection, hazard assessment, and health risk management). Further research and development needs are discussed to exploit the full power of MST technology. In conclusion, this study illustrates the capacity of molecular faecal pollution diagnostics to revolutionize water quality testing in the decades to come.
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.
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