No abstract

Two advanced removal methods (adsorption and photocatalysis) were compared for the elimination of an ethoxylated alkylphenol (nonylphenol polyethylene glycol, NPEG). For the adsorption process, zeolites were used in their natural state, and the process was characterized by DRX (X-ray diffraction) and SEM-EDS (Scanning electron microscopy). The analysis of the results of the adsorption kinetics was carried out using different isotherms to interpret the removal capacity of zeolites. The Temkin kinetic model better predicted the experimental data and was satisfactorily adjusted to models of pseudo-second order (PSO). On the other hand, for photocatalysis, nano-particles of Ag (silver) were deposited on titanium oxide (TiO 2 ) Degussa-P25 by photo-deposition, and the catalyst was characterized by diffuse reflectance and SEM-EDS. The data obtained using the two removal techniques were analyzed by UV-Vis (ultraviolet-visible spectrophotometry) and total organic carbon (TOC). The kinetic data were compared. The photocatalytic process showed the highest efficiency in the removal of NPEG, corresponding to >80%, while the efficiency of the adsorption process was <60%. This was attributed to the recalcitrant and surfactant nature of NPEG.

Wet deposition was collected in Mexico City (MC), Metropolitan Area of Monterrey (MAM) and El Chico National Park (ECNP), during 2009 and 2010. pH, conductivity, Cl − , 2 4 SO − 3 NO − , 4 NH + , Na + , K + , Ca 2+ and Mg 2+ were determined. In MC, sulphate levels were greater than nitrate levels, and NH4 had mixed sources (vehicular emissions and agriculture activities). MAM had markedly alkaline atmospheric deposition, Na + and Cl − levels were unexpectedly high, especially during hurricane "Alex". Low pH values were found in ECNP and nitrate concentrations were high, suggesting the influence of a local source (forest fires). Deposition fluxes (Kg•ha −1 •yr −1) for N-NO 3 , N-NH 4 and S-SO 4 were 1.36, 2.74 and 4.84 for MAM; 7.27, 0.57 and 4.32 for ECNP; and 5.97, 4.96 and 6.78 for MC, respectively. Nitrogen deposition fluxes in ECNP were high considering that this site is a natural reserve.

Background: Metal pollution is a problem in many parts of the world. These metals can be harmful when they exceed the recommended limits. By analyzing metal concentrations in living organisms, it is possible to deduce the bioavailability and the level of environmental contamination for specific metals in an ecosystem. The aim of this study was to determine the heavy metals copper, cadmium, lead, nickel and mercury in edible tissues of fish, to establish the risk analysis for human health. There are currently no studies in this area indicating these factors. Methods: The edible tissue samples were treated under the techniques of the official mexican standards (NOM-117-SSA1) and analyzed using atomic absorption spectroscopy (flame and graphite). The heavy metal concentrations were used to calculate the estimated daily intakes, target hazard quotients, hazard indices, and target cancer risks for children and adults. Results: The highest concentrations of copper (138.82 μg/g), cadmium (1.28 μg/g) and lead (3.20 μg/g) in the edible tissue samples exceeded the permissible limits considered in this study while nickel and mercury levels did not. The target hazard quotient indices for copper, cadmium and nickel in specific sites were higher than the United States Environmental Protection Agency (US-EPA) criteria (>1), while the values ​​for mercury and lead were below one. The hazard indices were higher than the US-EPA criteria (>1) in more than 50% of the sites analyzed. Conclusion: This study is an alert, indicating that inhabitants who consume the fish, particularly children, are at risk of cadmium, lead and nickel toxicity.