西安市PM2.5中环境持久性自由基污染特征

环境持久性自由基（EPFRs）是相对传统短寿命自由基提出的一种半衰期较长的新型环境风险物质，可将O₂分子转化为活性氧物质，从而危害人体健康.为研究2018年西安市大气PM_2.5中EPFRs的种类、浓度及其来源，本文利用电子顺磁共振波谱方法对2018全年的大气PM_2.5样品进行EPFRs分析.结果表明：2018年西安市PM_2.5中EPFRs年平均大气浓度为2.16×10¹⁴spins/m³，范围为6.27×10¹²~1.07×10¹⁵spins/m³，呈现冬季>秋季>夏季>春季的季节变化特征.按照EPFRs年平均浓度计算出西安市民每人每天吸入体内EPFRs的量相当于7支香烟，而在冬季雾霾天气高达35支香烟.西安市PM_2.5中EPFRs的年平均g因子为（2.0034±0.0002），说明其可能主要是以碳为中心的自由基.相关性结果发现EPFRs与SO₂和NO₂显著相关，说明煤炭燃烧源和交通源可能是西安市PM_2.5中EPFRs的重要来源.

Study on pollution characteristics of environmentally persistent free radicals of PM2.5 in Xi'an

Environmentally persistent free radicals (EPFRs) are a new environmental risk substances with long half-life compared to traditional short-lived free radicals, which could convert O₂ molecules into reactive oxygen species and endanger human health. In order to the species, concentrations and sources of EPFRs in PM_2.5 in Xi'an in 2018, the electron paramagnetic resonance spectroscopy method was used to analyze EPFRs of the collected PM_2.5 samples. Results showed that the annual average atmospheric concentration of EPFRs in PM_2.5 in Xi'an was 2.16×10¹⁴ spins/m³ in 2018, with the range of 6.27×10¹²~1.07×10¹⁵ spins/m³. The seasonal variationsof EPFRs was highest in winter, following was autumn, summer and spring. According to the average annual concentration of EPFRs, the amount of EPFRs inhaled by people in Xi'an was equivalent to 7cigarettesper people per day, and as high as 35 cigarettes during haze days in winter. The annual average g factor of EPFRs in PM_2.5 of Xi'an was 2.0034±0.0002, indicating that it may be mainly carbon-center free radicals. Correlation results showed that EPFRs are significantly correlated with SO₂ and NO₂, indicating that coal combustion sources and transportation may be important of EPFRs in PM_2.5 in Xi'an.