Theoretical study on degradation of polymethyl substituted benzenes by OH radicals in the atmosphere.

As volatile organic compounds (VOCs), pentamethylbenzene (5-PeMB) and hexamethylbenzene (6-HeMB) are found widely in petroleum and coal tar. Through combustion and industrial generation entering into the atmosphere, they can produce photochemical smog and secondary organic aerosols (SOA) to endanger human health and ecoenvironment eventually. In order to reveal their environmental chemistry, the OH-initiated degradation mechanisms of 5-PeMB and 6-HeMB were studied based on density functional theory (DFT). Result showed that addition pathways were the most favorable with energy barriers of 20.7 and 25.3 kJ/mol, respectively, in the two reactions. The degradation rate constants at 298 K were calculated to be 2.69 × 10-10 and 1.28 × 10-10 cm3 molecule-1 ·s-1, coinciding with the available experimental values. In the presence of OH radicals, the atmospheric lifetimes were estimated to be 2.17 and 2.78 h, respectively, for 5-PeMB and 6-HeMB. According to the quantitative structure-activity relationship (QSAR) model, the toxicity during the degradation process is decreased to fish, daphnia, and green algae.

The Outlook of Green Building Development in China during the "Fourteenth Five-Year Plan" Period.

To achieve the "Double Carbon" target, China is paying increasing attention to green building development. Thus, this study selected 26 regional green building development planning documents that have been put into practice since the implementation of the 14th Five-Year Plan and analyzed different development goals and common development barriers and paths presented in regional documents by conducting qualitative research. After the analysis of common goals and goals with regional characteristics, this study verified that spatial imbalances did exist in the development targets of green building in each region during the "14th Five-Year Plan", and the development priorities also varied from region to region. Due to the relation between development goals and the current situation, this study can also illustrate the spatial imbalances of the development situation between different regions. The results of this study can assist regional governments in gaining a clear self-positioning to judge whether they keep pace with the national development level of green buildings and encourage them to take measures to guarantee the stable development of green buildings.

Degradation of mevinphos and monocrotophos by OH radicals in the environment: A computational investigation on mechanism, kinetic, and ecotoxicity.

Known organophosphorus pesticides are used widely in agriculture to improve the production of crops. Based on the literature, the degradation of some organophosphorus pesticides was studied theoretically. However, the mechanisms and variation of toxicity during the degradation of mevinphos and monocrotophos are still unclear in the environment, especially in wastewater. In this study, the reaction mechanisms for the degradation of the two representative organophosphorus pesticides (i.e., mevinphos and monocrotophos) in presence of OH radicals in the atmosphere and water are proposed using quantum chemical methods wB97-XD/6-311 + +G(3df,2pd)//wB97-XD/6-311 + +G(d,p). Result shows that the dominant channel is OH-addition to the C atom in CC bond with energy barriers being 15.6 and 14.7 kJ/mol, in the atmosphere and water, respectively, for mevinphos. As for monocrotophos, H-abstraction from NH group via barriers of 8.2 and 10.6 kJ/mol is more feasible in both the atmosphere and water. Moreover, the subsequent reactions of the major products in the atmosphere with NO and O2 were also studied to evaluate the atmospheric chemistry of mevinphos and monocrotophos. Kinetically, the total rate constant is 2.68 × 10-9 and 3.86 × 10-8 cm3 molecule-1·s-1 for mevinphos and monocrotophos in the atmosphere and 4.91 × 1010 and 7.77 × 1011 M-1 s-1 in the water at 298 K, thus the lifetime is estimated to be 36.46-364.60 s (2.53-25.31 s) in the atmosphere, and 1.41 × 10-2 - 1.41 × 10-1 s (8.92 ×10-4 - 8.92 ×10-3 s) in the advanced oxidation processes (AOPs) system. Furthermore, ecotoxic predictions for rats and three aqueous organisms imply their toxicity are reduced during degradation by using ECOSAR and T.E.S.T program based quantitative structure and activity relationship (QSAR) method.

OH-initiated degradation of 1,2,3-trimethylbenzene in the atmosphere and wastewater: Mechanisms, kinetics, and ecotoxicity.

1,2,3-Trimethylbenzene (1,2,3-TMB) is an important volatile organic compound (VOC) present in petroleum wastewater and the atmosphere. This compound can be degraded by OH radicals via abstraction, addition and substitution mechanisms. Results show that the addition mechanism is dominant and H-abstraction is subdominant, while methyl abstraction and substitution mechanisms are negligible in the gas and aqueous phases. Moreover, H-abstraction products undergo further reactions with O2, NO, NO2, H2O, and OH radicals in the atmosphere. Time-dependent density functional theory (TDDFT) calculations show that the degraded products, including 2,3,4-trimethylphenyl-nitroperoxoite, 1,2,3-trimethyl-4-nitrobenzene, 1,2,3-trimethyl-5-nitrobenzene, 2,6-dimethylbenzyl nitroperoxoite, 2,3-dimethylphenyl nitroperoxoite, 2,6-dimethylbenzaldehyde, and 2,3-dimethylbenzaldehyde, can photolyze under the sunlight. Kinetically, the calculated total rate constant is 5.57 × 10-11 cm3 molecule-1·s-1 at 1 atm and 298 K, which is consistent with available experimental values measured in the atmosphere. In addition, the calculated total reaction rate constant in water is close to that in the gas phase. In terms of ecotoxicity, all degradation products are less toxic than the initial reactant to fish, green algae and daphnia. For mammals represented by rats, 1,2,3-TMB and its products are moderately toxic, except for 2,3-dimethylphenol and 2,6-dimethylphenol, which are slightly toxic.

A new theoretical investigation on ·OH initiated oxidation of acephate in the environment: mechanism, kinetics, and toxicity.

Acephate (O,S-dimethyl acetylphosphoramidothioate) is a typical organophosphorus pesticide used widely in agriculture. It can be released into the atmosphere and water during production and application. In this work, mechanisms in the ·OH initiated degradation of acephate were investigated using quantum chemical methods. Results show that addition, substitution and H-abstraction mechanisms can take place, with the latter being dominant. Moreover, the subsequent reactions of dominant products with O2 and NO in the atmosphere were considered, as well. The rate constant in the atmosphere and aqueous phase was calculated by transition state theory (TST) with the Wigner tunneling contribution. The total rate constant in the atmosphere and aqueous phase is 7.86 × 10-10 and 1.83 × 10-12 cm3 per molecule per s, respectively, the latter being in accordance with the available experimental value of 1.50 × 10-12 cm3 per molecule per s. Moreover, the ecotoxicity of acephate and degradation products was assessed in fish, daphnia, green algae and rats.

Investigations on mechanisms, kinetics, and ecotoxicity in OH-initiated degradation of 1,2,4,5-tetramethylbenzene in the environment.

As one of the volatile organic compounds (VOCs) in the environment, 1,2,4,5-tetramethylbenzene (1,2,4,5-TeMB) present in oily wastewater, and it can occur substitution, abstraction, and addition reactions with OH radicals in the atmosphere and wastewater. Electrostatic potential (ESP) and average local ionization energy (ALIE) prediction indicate that H atoms from CH3 group and the benzene ring are the most active sites in 1,2,4,5-TeMB. The result shows that potential energy surfaces (PESs) in the gas and aqueous phase are similar, and the relevant barriers in the latter one are higher. The dominant channel is H abstraction from the benzene ring, and the subdominant one is OH radical addition to the benzene ring. Furthermore, subsequent reactions of dominant products with O2, NO2, NO, and OH radicals in the atmosphere are studied, as well. The total reaction rate constant is calculated to be 2.36×10-10 cm3 molecule-1 s-1 at 1 atm and 298 K in the atmosphere, which agrees well with the experimental data. While the total rate constant in the aqueous phase is much lower than that in the gas phase. Ecologic toxicity analysis shows that 1,2,4,5-TeMB is very toxic to fish, daphnia, and green algae; and OH-initiated degradation in the environment will reduce its toxicity.