Exploratory study on the presence of bisphenol A and bis(2-ethylhexyl) phthalate in the Santa Catarina River in Monterrey, N.L., Mexico.

The current problem related to the supply of drinking water for the metropolitan area of Monterrey, which comprises of five million inhabitants, and the important role played by the El Cuchillo Dam, found downstream of the Santa Catarina River basin as a surface source of drinking water for the city, renders this river an interesting site for assessment. This work evaluates the degree to which the surface water and the subsoil of the river are affected by emerging organic pollutants due to their existence, even at low concentrations, representing a toxic risk enhanced by the absence of stricter standards for regulating these substances. Based on fieldwork, three discharge points that could affect the quality of the surface water were selected: two points on the river stream, and three groundwater wells. Gas chromatography results showed the presence of BisPhenol A (BPA) and bis(2-EthylHexyl) Phthalate (DEHP) in both the surface water and subsoil at different seasons of the year. The highest concentration levels in the samples taken from both types of water were 0.9 and 60 µg L-1 for BPA and DEHP, respectively. Results of this research did not reveal the level at which the aquifer is affected by these substances.

Chitosan hydrogel synthesis to remove arsenic and fluoride ions from groundwater.

Groundwater samples from eight deep drinking water wells that cover three aquifers in Chihuahua City, northern Mexico, were fully characterized. Water is naturally contaminated with arsenic, fluoride, and uranium, according to the Environmental Protection Agency (EPA) and local standards. The results from the Geochemist's Workbench (GWB) program revealed that the minerals in equilibrium with the groundwater were calcite and dolomite, while others, such as fluoride, schoepite, rutherfordite and K(UO2)(AsO4), were also dissolved. The hydrogeochemical characterization of water samples indicates that they were sodium bicarbonate-type water samples at neutral to slightly alkaline pH (7.6-8.3). A batch equilibrium sorption procedure was implemented using natural groundwater, a synthesized chitosan network (net-CS) and a chitosan binary network grafted with N-vinylcaprolactam/N-N-dimethylacrylamide (net-CS)-g-NVCL/DMAAm hydrogels. Isotherms and kinetics sorption tests were evaluated. The adsorption capacity of net-CS hydrogels for As ions was 0.0022 mg/g and F ions 0.15 mg/g after 50 h. Scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM-EDS) was used to investigate the hydrogel surface before and after the sorption process, and TGA was used to evaluate the stability of the adsorbents. Freundlich adsorption isotherm constants for As and F ions indicate heterogeneous sorption and the mechanism of retention by physisorption.