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Theoretical study on the mechanisms, kinetics and ecotoxicity assessment of OH-initiated reactions of guaiacol in atmosphere and wastewater
- An, Zexiu, Sun, Jianfei, Han, Dandan, Mei, Qiong, Wei, Bo, Wang, Xueyu, He, Maoxia
- The Science of the total environment 2019 v.685 pp. 729-740
- aerosols, aqueous solutions, ecotoxicology, energy, formates, gases, guaiacol, half life, nitrogen dioxide, quinones, solvents, toxicity, wastewater
- The OH-initiated transformation mechanisms, kinetics and ecotoxicity assessment of guaiacol (2-methoxyphenol) in the presence of O2/NOx were investigated both in atmosphere and wastewater. The solvent effect lowers the energy barriers of initial OH-addition reactions more than H-abstraction reactions, leading to much higher addition branching ratio (Γadd) of 0.92 in aqueous solution than that of 0.42 in gas-phase. At 298 K, the overall rate constants of the title reactions in atmosphere and wastewater are 5.56 × 10−12 and 1.41 × 10−11 cm3 molecule−1 s−1 with corresponding half-lives of 34.6 h and 0.82 s, respectively. In atmosphere, all the proposed favorable products including nitroguaiacols, methoxybenzoquinone, 2-hydroxyphenyl formate, 2-methoxybenzene-1, 3-diol and dialdehyde could contribute to secondary organic aerosols (SOAs). In wastewater, NO2 addition reactions lead to higher toxicity of products (nitroguaiacols and 2-methoxybenzene-1, 4-diol) than that of parental guaiacol. However, O2/NO addition pathways may generate less harmful products except for methoxybenzoquinone (P3) which is with higher toxicity than guaiacol. Therefore, more attention should be focused on the products formed from OH-initiated reactions of guaiacol both in atmosphere and wastewater.