A DFT study of the vibrational spectra of 1-, and 2-nitrotriphenylene

Structural characterization and evaluation of municipal wastewater sludge (biosolids) from two rural wastewater treatment plants in East Texas, USA

Wastewater sludge (or) biosolids collected from two rural wastewater treatment plants (NWWTP, LWWTP) in East Texas, USA were characterized and evaluated via inductively coupled plasma optical emission spectrometry, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), thermogravimetric analysis, X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), and ion chromatography. The proximate organic and inorganic compositions and spectroscopic characteristics of sewage sludge were determined. The results show that the concentrations of toxic metals Cd, Cr, Cu, Mo, Ni, Pb, Hg, and Zn meet USEPA guideline recommendations for land applications. Notably, metals concentrations in biosolids from NWWTP (Mn (700 ± 83) > Zn (422.5 ± 35.4 ppm) > Ba (319.5 ± 87 ppm) > Cu (240 ± 27 ppm) > B (107 ± 14 ppm) > V (24 ± 3.3 ppm) > Cr (20 ± 3.3 ppm) > Ni (16.7 ± 2.0 ppm) > Pb (16.8 ± 1.1 ppm) > As (11.99 ± 1.27 ppm) > Co (7.6 ± 0.7 ppm) > Mo (6.4 ± 1.4 ppm) > Hg (0.55 ± 0.24 ppm) > Cd (0.130 ± 0.109 ppm)) and LWWTP follow similar trends. Macro-elements concentrations in LWWTP follow the trend P (19,648 ± 169) > Fe (22,688 ± 2110) > Ca (9372 ± 163) > S (9010 ± 1009) > Al (12,538 ± 2116) > K (3514 ± 550) > Mg (33,370 ± 502) > Na (1511 ± 472). The Br^-, NO₃^-, NO₂^-, F^-, Cl^-, and SO₄^2- concentrations meet USEPA guidelines. Whereas biosolid particle sizes were in the range ~20 μm to 500 μm mineralogical results show quartz and vermiculite to be major constituents with abundancies 12.94%, and 10.87% w/wt, respectively.

Vibrational and electronic spectra of 2-nitrobenzanthrone: An experimental and computational study

The environmental pollutant 2-nitrobenzanthrone (2-NBA) poses human health hazards, and is formed by atmospheric reactions of NOX gases with atmospheric particulates. Though its mutagenic effects have been studied in biological systems, its comprehensive spectroscopic experimental data are scarce. Thus, vibrational and optical spectroscopic analysis (UV-Vis, and fluorescence) of 2-NBA was studied using both experimental and density functional theory employing B3LYP method with 6-311+G(d,p) basis set. The scaled theoretical vibrational frequencies show good agreement to experiment to within ~5 cm(-1) and <20 cm(-1) for frequencies <1800 cm(-1) and 2700-3200 cm(-1), respectively. In addition, predictions of the DFT frequencies below 1800 cm(-1) yield an overall root mean square (RMS) of ±20.1 and ±20.6 cm(-1) for benzanthrone and 2-NBA, respectively. On the basis of normal coordinate analysis complete assignments of harmonic experimental infrared and Raman bands are made. The influence of the nitro group substitution upon the benzanthrone structure and symmetric CH vibrations, and electronic spectra is noted. This study is useful for the development of spectroscopy-mutagenicity relationships in nitrated polycyclic aromatic hydrocarbons.

FTIR analysis and evaluation of carcinogenic and mutagenic risks of nitro-polycyclic aromatic hydrocarbons in PM1.0

Nitro-polycyclic aromatic hydrocarbons (NPAHs) represent a group of organic compounds of significant interest due to their presence in airborne particulates of urban centers, wide distribution in the environment, and mutagenic and carcinogenic properties. These compounds, associated with atmospheric particles of size < 1 μm, have been reported as a major risk to human health. This study aims at identifying the spectral features of NPAHs (1-nitropyrene, 2-nitrofluorene, and 6-nitrochrysene) in emissivity and transmittance spectra of samples of particulate matter < 1 μm (PM1.0) using infrared spectrometry. Carcinogenic and mutagenic risks of the studied NPAHs associated with PM1.0 samples were also determined for two sampling sites: Canoas and Sapucaia do Sul. The results showed that NPAH standard spectra can effectively identify NPAHs in PM1.0 samples. The transmittance and emissivity sample spectra showed broader bands and lower relative intensity than the standard NPAH spectra. The carcinogenic risk and the total mutagenic risk were calculated using the toxic equivalent factors and mutagenic potency factors, respectively. Canoas showed the highest total carcinogenic risk, while Sapucaia do Sul had the highest mutagenic risk. The seasonal analysis suggested that in the study area the ambient air is more toxic during the cold periods. These findings might of significant importance for the decision and policy making authorities.

Formation of nitroanthracene and anthraquinone from the heterogeneous reaction between NO2 and anthracene adsorbed on NaCl particles

Oxidative derivatives of polycyclic aromatic hydrocarbons (PAHs), that is, nitro-PAHs and quinones, are classed as hazardous semivolatile organic compounds but their formation mechanism from the heterogeneous reactions of PAHs adsorbed on atmospheric particles is not well understood. The heterogeneous reaction of NO2 with anthracene adsorbed on NaCl particles under different relative humidity (RH 0-60%) was investigated under dark conditions at 298 K. The formation of the major products, 9,10-anthraquinone (9,10-AQ) and 9-nitroanthracene (9-NANT), were determined to be second-order reactions with respect to NO2 concentration. The rate of formation of 9,10-AQ under low RH (0-20%) increased as the RH increased but decreased when the RH was further increased in high RH (40-60%). In contrast, the rate of formation of 9-NANT across the whole RH range (0-60%) decreased significantly with increasing RH. Two different reaction pathways are discussed for the formation of 9,10-AQ and 9-NANT, respectively, and both are considered to be coupled to the predominant reaction of NO2 with the NaCl substrate. These results suggest that relative humidity, which controls the amount of surface adsorbed water on NaCl particles, plays an important role in the heterogeneous reaction of NO2 with adsorbed PAHs.

Prediction of mutagenic activity of nitrophenanthrene and nitroanthracene isomers by simulated IR and Raman spectra

This paper expands upon our original work on nitroanthracenes in (Alparone, A., Librando, V., 2012. Spectrochim. Acta A 89, 129-136) on the series of nitrophenanthrene isomers. Geometries, electric properties, IR and Raman spectra of 1-, 2-, 3-, 4- and 9-nitrophenanthrene (1-NP, 2-NP, 3-NP, 4-NP and 9-NP) were obtained and analyzed using Density Functional Theory calculations. The balance between steric and π-conjugative interactions determines the order of stability 4-NP<1-NP~9-NP<2-NP∼3-NP. IR and Raman spectral zones between 1000 and 1600 cm(-1) show intense bands noticeably affected by the position of the substituent, being potentially useful to discriminate and monitor the investigated isomers. Dipole moments, summations of IR intensity (ΣI(IR)) and Raman activity (ΣA(Raman)) over the 3N-6 vibrational modes are sensitive to the structure, increasing steadily from the non-planar to the planar isomers. Good linear relationships between the ΣI(IR) (r=0.90) and ΣA(Raman) (r=0.99) against the Salmonella typhimurium strain TA98 mutagenic activity of nitrophenanthrenes and isomeric nitroanthracenes are found. On the basis of the structural and vibrational properties, 4-NP seems to have not mutagenic activity, while the unknown TA98 mutagenic potency of 1-nitroanthracene is predicted to be between that of 9-NP and 3-NP. Calculated ΣI(IR) and ΣA(Raman) values could be used as molecular descriptors for QSARs applications of series of isomers.

IR and Raman spectra of nitroanthracene isomers: substitional effects based on density functional theory study

Structure, IR and Raman spectra of 1-, 2- and 9-nitroanthracene isomers (1-NA, 2-NA and 9-NA) were calculated and analyzed through density functional theory computations using the B3LYP functional with the 6-311+G** basis set. Steric and π-conjugative effects determine the characteristic ONCC dihedral angles, which vary from 0° (2-NA) to 28-29° (1-NA) and 59° (9-NA), influencing the relative order of stability along the series 9-NA<1-NA<2-NA. The spectral regions at wavenumber values>3000 cm(-1) and <1000 cm(-1) little depend on the substituent position. The Raman and IR intensity values of the characteristic symmetric nitro group stretching transition, appearing between 1310 and 1345 cm(-1), are rather sensitive to the position of the substituent, decreasing regularly on passing from the planar to the NO2-rotated isomers (9-NA<1-NA<2-NA). In the medium-energy spectral region (1000-1700 cm(-1)), the number and the relative position of the strongest Raman bands are of potential utility to discriminate the NA isomers. Structural and spectroscopic results suggest that the unknown mutagenic activity of 1-NA is expected to be between that of 9-NA and 2-NA.

Vibrational and electronic spectra of 9,10-dihydrobenzo(a)pyren-7(8H)-one and 7,8,9,10-tetrahydrobenzo(a)pyrene: an experimental and computational study

The molecular geometries, vibrational and UV-vis spectra of 9,10-dihydrobenzo(a)pyrene-7(8H)-one (9,10-H(2)BaP) and 7,8,9,10-tetrahydrobenzo(a)pyrene (7,8,9,10-H(4)BaP) were investigated using density functional theory (DFT-B3LYP), with the triple-ζ 6-311+G(d,p) and Dunning's cc-pVTZ basis sets. From the comparison of infrared experimental and calculated infrared, and Raman data comprehensive assignments are made. The calculated infrared frequencies below 1800 cm(-1) are in good agreement with experimental data, with an average deviation of <4 cm(-1). Using the B3LYP/6-311+G(d,p)//TD-B3LYP/6-311G(d,p) level of theory, transition energies, and oscillator strengths of the 30 lowest electronic absorption bands are assigned to π-π* transitions, with good qualitative agreement between experimental and simulated absorption data. In addition, the HOMO-LUMO gaps and their chemical hardness were analyzed.