西安冬季PM2.5中多环芳烃、含氧多环芳烃和硝基芳香类化合物的昼夜污染特征及毒性效应

Diurnal pollution characteristics and toxic effects of PAHs and their derivatives in winter PM2.5 in Xi’an

关键词:  毒性  多环芳烃  硝基酚  PM_2.5  含氧多环芳烃

Key words:  toxicity  polycyclic aromatic hydrocarbons  nitrophenols  PM_2.5  oxygenated polycyclic aromatic hydrocarbons

摘要:

基于2022年1—2月采集的西安市昼夜PM_2.5样品，利用气相色谱-静电场轨道阱质谱联用仪 （GCOrbitrap MS）定量分析了多环芳烃（PAHs）、含氧多环芳烃（OPAHs）和硝基芳香族化合物（NACs）这3种组分的共31种有机物，结合人体吸入暴露模型和ADMETlab 3.0毒性预测模型，计算了3类化合物与人体健康相关的19种毒性终点的毒性当量。结果表明，3类有机物的总浓度呈现夜高昼低的趋势，夜间浓度 （169.6 ng/m³ ）约为白天（90.8 ng/m³ ）的1.9倍，其中OPAHs和NACs的昼夜浓度差异小于PAHs。基于吸入暴露的毒性评估表明，夜间3类有机物的小时毒性当量（TEQ，4.9—59.5 ng/h）显著高于白天（1.7—2.0倍）， 其中，PAHs主导了hERG钾通道阻滞剂（hERG Blockers）、药物诱导的神经毒性（Neurotoxicity-DI）、耳毒性 （Ototoxicity） 等毒性终点 （＞50%）；NACs则在皮肤致敏性 （Skin Sensitization）、眼腐蚀性 （Eye Corrosion） 及基因毒性 （Genotoxicity） 中表现突出；OPAHs的药物诱导的肾脏毒性 （Nephrotoxicity-DI） 和血液毒性 （Hematotoxicity）较高。研究结果表明，仅关注单一的致癌风险会低估由NACs和OPAHs等其他组分引发的特异性非致癌健康危害，应加强多组分协同效应的健康风险研究。

Abstract:

Background, aim, and scope In recent years, despite declining atmospheric particulate matter (PM_2.5) mass concentrations, health risks have not decreased proportionally because highly toxic organic components persist, with respiratory exposure and toxic effects exhibiting pronounced diurnal differences. This study investigates the diurnal variations of PM_2.5, polycyclic aromatic hydrocarbons (PAHs), oxygenated PAHs (OPAHs), and nitro-aromatic compounds (NACs) in Xi’an from January to February 2022, together with their inhalation exposure levels and toxicity equivalents. The aim is to systematically evaluate the pollution characteristics and associated health risks of organic compounds in wintertime PM_2.5. Materials and methods Diurnal PM_2.5 samples were collected in Xi’an from January to February in 2022. 31 Organic components including PAHs, OPAHs and NACs were quantified using gas chromatography coupled with Orbitrap mass spectrometry (GC-Orbitrap MS). By integrating a human inhalation exposure model with the ADMETlab 3.0 toxicity prediction model, the diurnal variations of 19 toxicity endpoints and the relative contributions of the three compound classes were assessed. Results PM_2.5 concentrations in winter were generally higher during the daytime than at nighttime, or comparable between day and night. Conversely, the total concentration of organic components displayed a distinct “higher-at-night” trend, with nighttime concentrations (169.6 ng/m³ ) approximately 1.9 times higher than daytime levels (90.8 ng/m3 ). Correspondingly, the hourly toxic equivalent quantities (TEQs) for 19 health-related endpoints were significantly elevated at night. PAHs were the dominant contributors to cardiotoxicity and neurotoxicity, while NACs and OPAHs primarily contributed to skin sensitization and nephrotoxicity, respectively. Discussion The high daytime PM_2.5 mass concentrations suggest that the intense photochemical formation of secondary aerosols during the daytime may offset atmospheric dispersion processes, thereby maintaining high pollution levels. In contrast, the accumulation of organic components was likely driven by a lower boundary layer height and enhanced primary combustion emissions. Stronger solar radiation during the daytime facilitates the formation of secondary inorganic ions, resulting in a higher inorganic mass fractions that partially compensate for diurnal differences in total PM_2.5 mass. Regarding organic composition, high-molecular-weight PAHs were predominant, likely originating from petroleum combustion and vehicular emissions, while being less susceptible to photodegradation under sunlight. Distinct diurnal patterns were also observed in toxicity contributions. NACs exhibited strong toxicological specificity, potentially associated with electrophilic nitro functional groups that may trigger immune responses or interfere with endocrine receptors. The relative contribution of OPAHs to TEQs was higher during the daytime, which may be attributed to photochemical oxidation processes that promote the secondary formation of OPAHs. In contrast, PAHs contributed more significantly at night, consistent with primary emissions. Conclusions During winter, the daily average PM_2.5 concentration in Xi’an exceeded the national Grade Ⅱ air quality standard, with no significant diurnal variation in total mass; the average concentration at daytime was slightly higher than night. In contrast, PAHs and their derivatives exhibited clear nighttime elevation, with the nighttime concentration approximately 1.9 times higher than daytime. The day–night differences for OPAHs and NACs were less pronounced. The equivalent concentrations for the 19 toxicity endpoints were significantly higher at nighttime than daytime, indicating that different component classes contribute differently to health risks. Recommendations and perspective Winter nights in Xi’an represent a critical period of highconcentration exposure to organic pollutants and associated health risks. Effective mitigation strategies should therefore strengthen controls on nocturnal coal and biomass burning while also addressing daytime photochemical secondary pollution. In addition, health risk assessment of PAHs and their derivatives should extend beyond carcinogenicity to include multiple toxicity endpoints in a comprehensive risk management framework.