Zirconia (ZrO 2)-modified graphitic carbon nitride (g-C 3 N 4) nanocomposite was used for effective photodegradation of 4-nitrophenol (4-NP) in water. The ZrO 2 nanoparticles, g-C 3 N 4 nanosheets, and ZrO 2 /g-C 3 N 4 nanocomposite were well characterized by including N 2 adsorption, X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, UV-Vis diffuse reflectance spectroscopy, photoelectrochemical measurements, and photoluminescence spectroscopy methods. ZrO 2 /g-C 3 N 4 nanocomposites were formed at room temperature using sonication and used for effective for photodegradation of 4-NP under irradiation with visible light. The nanocomposite samples resulted in a significant increase in photocatalytic activity compared with single-component samples of g-C 3 N 4. In particular, the ZrO 2 /g-C 3 N 4 nanocomposite exhibited the significant increase in the photocatalytic activity. The ZrO 2 /g-C 3 N 4 nanocomposite showed an excellent catalytic activity toward the reduction of 4-NP in aqueous medium. Further, ZrO 2 /g-C 3 N 4 nanocomposite can be reused several times for photocatalytic degradation as well as for 4-NP adsorption.

In this paper, we show the reaction of a hydroxyl, phenyl and phenoxy radicals with DNA base pairs by the density functional theory (DFT) calculations. The influence of solvation on the mechanism is also presented by the same DFT calculations under the continuum solvation model. The results showed that hydroxyl, phenyl and phenoxy radicals increase the length of the nearest hydrogen bond of adjacent DNA base pair which is accompanied by decrease in the length of furthest hydrogen bond of DNA base pair. Also, hydroxyl, phenyl and phenoxy radicals influenced the dihedral angle between DNA base pairs. According to the results, hydrogen bond lengths between AT and GC base pairs in water solvent are longer than vacuum. All of presented radicals influenced the structure and geometry of AT and GC base pairs, but phenoxy radical showed more influence on geometry and electronic properties of DNA base pairs compared with the phenyl and hydroxyl radicals.

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DRASTIC is a model that is commonly used to assess vulnerability to groundwater contamination at the landscape scale. When sparse data are available to populate the layers of the model, it can be difficult to ascertain the true usefulness of the model produced map. In this research an alluvial aquifer, the Sahneh aquifer in Kermanshah province of western Iran, was mapped using the generic DRASTIC model. The data available for populating the model layers were generally sparse. The model was validated using a nitrate concentration map constructed from well water measurements within the DRASTIC map area. A Receiver Operating Curve (ROC) analysis was conducted by placing 500 random points in the DRASTIC generated map compared to the nitrate concentration map. The area under the curve was compared and yielded a value of 0.72 or 72% concordance, which means it has good validity. This investigation demonstrates that a generic DRASTIC model can yield acceptable results without modification or increasing its complexity. If the ROC analysis had yielded a value <50%, then the DRASTIC would have been considered to not be useful. A common mistake in the use of DRASTIC is to modify the method to greatly increase its complexity, which may actually decrease, not increase the resultant model usefulness.

The Dehgolan aquifer, which lies in semiarid western Iran, was evaluated using a multi-influencing factor (MIF) analysis to determine groundwater sustainability. Eight indicators, including climatic variability, groundwater exploitation (pumping), groundwater quality, groundwater vulnerability, public participation, legal framework, water productivity, and occupation related to groundwater, were quantified and placed into a series of thematic maps within a GIS framework. Each factor was weighted based on the analyses obtained from the MIF model and the stacked maps were summed to yield a final map showing the degree of sustainability within the groundwater basin. The final groundwater sustainability map showed that 4% of the basin was in a critically unsustainable zone, 30% in an unsustainable zone, 40% in a semisustainable zone, 25% in a sustainable zone, and 1% in an ideally sustainable zone. The final map was validated using a receiver operating characteristic (ROC) method, cross-tabulation, and chi-square tests using groundwater-level decline as a test proxy. The analysis assessed the correlation between water levels that exhibited declines versus the degree of unsustainability of water levels and sustainable water use. The area under the curve was calculated to be 88%, cross-tabulation 64.4%, and the chi-square value was 260.5 with 4 degrees of freedom and values <0.05 (3.627E −55 ), which suggest that the final map has statistical significance. The sustainability analysis developed is useful as a baseline for development of governance laws to implement management methods in groundwater basins and it can be applied to a wide range of aquifer types in variable climates worldwide.