Legionella spp. is an environmental bacterium that can survive in a wide range of physicochemical conditions and may colonize distribution systems of drinking water and storage tanks. Legionella pneumophila is the major waterborne pathogen that can cause 90% of Legionnaires’ disease cases. The aim of this study was to detect the presence of Legionella spp. in household drinking water tanks in the city of Resistencia, Chaco. The detection of Legionella in water samples was performed by culture methods as set out in ISO 11731:1998. Thirty two water samples were analyzed and Legionella spp. was recovered in 12 (37.5%) of them. The monitoring of this microorganism in drinking water is the first step towards addressing the control of its spread to susceptible hosts.

In the Gran Sasso fissured carbonate aquifer (central Italy), a long-term (2001–2007) spatio-temporal hydrochemical and²²²Rn tracing survey was performed with the goal to investigate groundwater flow and water–rock interaction. Analyses of the physico-chemical parameters, and comparisons of multichemical and characteristic ratios in space and time, and subsequent statistical analyses, permitted a characterisation of the hydrogeology. At the regional scale, groundwater flows from recharge areas to the springs located at the aquifer boundaries, with a gradual increase of mineralisation and temperature along its flowpaths. However, the parameters of each group of springs may significantly deviate from the regional trend owing to fast flows and to the geological setting of the discharge spring areas, as corroborated by statistical data. Along regional flowpaths, the effects of seasonal recharge and lowering of the water table clearly cause changes in ion concentrations over time. This conceptual model was validated by an analysis of the²²²Rn content in groundwater.²²²Rn content, for which temporal variability depends on seasonal fluctuations of the water table, local lithology and the fracture network at the spring discharge areas, was considered as a tracer of the final stages of groundwater flowpaths.

Two contrasting sites along Huehueyapan River (Veracruz, Mexico), one relatively conserved and the other one impacted by domestic and coffee mill discharges, were compared based on water quality data, and the structure of the Odonata larval assemblages. Riparian vegetation of both sites was differentially modified or replaced. Physical and chemical parameters and Odonata larvae were gathered from January to November 2001. A Hotelling-T test was used to compare the physico-chemical parameters while rank/abundance graphs and Renyi diversity profiles were constructed using Odonata larvae data. A total of 2,212 larvae of 13 species in 7 genera were collected. The sites were very similar in number of species and Odonata larval assemblage structure, however, some of the most abundant species at both sites showed significant differences in abundance. The observed differences between the 2 sites are mainly explained by differences in the structure of riparian vegetation and the availability of substrates for odonates and, secondarily, by physical and chemical changes in the water. An abundance ratio was established based on the most abundant species for monitoring future impairment or recovery changes.

Major ion geochemistry reveals that the hydrochemical evolutionary process of karst groundwater in the northeastern Huaibei Plain, China, consists of three sub-processes: the dissolution of dolomite, gypsum dissolution with dedolomitization, and mixing with overlying pore water. Understanding hydrochemical evolution has been an important topic in understanding the history, status, and dynamics of the groundwater flow system. The presented study found a hydrochemical boundary roughly corresponding to the thickness of overlying strata equating to 50 m depth, indicating two flow compartments participating in different hydrological cycles—a local shallow rapidly replenished compartment showing lower and more stable main ion concentrations, and a regional deep-flow compartment showing higher and sporadic concentrations of Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻ and SO₄²⁻, as well as high total dissolved solids (TDS), total hardness, and sodium adsorption ratio (SAR). In areas with aquifers with low water transmitting ability, groundwater samples show a high chloride ratio and elevated TDS values, indicating salinization of groundwater due to stagnant water flows. Analyses of the data on the saturation indexes and mineral solutions, in tandem with trilinear diagram analysis and petrological observations, indicate that dedolomitization is the dominant process controlling the chemical characteristics of karst groundwater in the study area. Groundwater and pore-water mixing was also observed at the later evolutionary stage of groundwater flow, demonstrating frequent groundwater/pore-water interactions where groundwater is recharged by pore water due to lower groundwater level in the study area.

Isotopic and hydrogeochemical analysis, combined with temperature investigation, was conducted to characterize the flow system in the carbonate aquifer at Taiyuan, northern China. The previous division of karst subsystems in Taiyuan, i.e. the Xishan (XMK), Dongshan (DMK) and Beishan (BMK) mountain systems, were also examined. The measured δD, δ ¹⁸O and ³He/⁴He in water indicate that both thermal and cold groundwaters have a meteoric origin rather than deep crustal origin. Age dating using ³H and ¹⁴C shows that groundwater samples from discharge zones along faults located at the margin of mountains in the XMK and DMK are a mixture of paleometeoric thermal waters and younger cold waters from local flow systems. ¹⁴C data suggest that the average age was about 10,000 years and 4,000 years for thermal and cold groundwater in discharge zones, respectively. Based on the data of temperature, water solute chemical properties, ¹⁴C, δ ³⁴SSO₄, ⁸⁷Sr/⁸⁶Sr and δ ¹⁸O, different flow paths in the XMK and DMK were distinguished. Shallow groundwater passes through the upper Ordovician formations, producing younger waters at the discharge zone (low temperature and ionic concentration and enriched D and ¹⁸O). Deep groundwater flows through the lower Ordovician and Cambrian formations, producing older waters at the discharge zone (high ionic concentration and temperature and depleted D and ¹⁸O). At the margin of mountains, groundwater in deep systems flows vertically up along faults and mixes with groundwater from shallow flow systems. By contrast, only a single flow system through the entire Cambrian to Ordovician formations occurs in the BMK.