西安市冬季霾污染过程PM2.5上蛋白质的浓度变化与来源分析

利用2019年12月至2020年1月在西安市3次灰霾污染过程中采集的PM_2.5样品,采用BCA试剂法、离子色谱和气相色谱-质谱检测法分别对样品中的蛋白质含量及无机有机化学成分进行了分析测定,结合相关性分析和气团后向轨迹模型分析探讨了PM_2.5上蛋白质对灰霾污染的响应及其在污染过程中可能的作用.结果表明,冬季灰霾污染期间,西安市PM_2.5中蛋白质组分的平均浓度为(5.587±2.421)μg/m³,处于较高水平;蛋白质浓度变化呈现出显著的短期连续变化特征,夜晚略高于白天.蛋白质的浓度与Cl^-和K⁺呈显著的正相关,说明气溶胶中蛋白质的来源与燃煤和生物质燃烧有关;与NO₃^-与SO₄^2-的浓度呈现显著的正相关,表明蛋白质可能参与NO₃^-与SO₄^2-的氧化转化;蛋白质具有良好的吸湿性,在湿度较大时,以其为核心吸附空气中的水蒸气及易溶于水的气态污染物(O₃、SO₂、NO_X以及挥发性有机物等)形成的气溶胶易于发生吸湿增长及非均相反应,可能利于二次气溶胶的生成.

Variations and sources of protein concentrations in PM2.5 during winter haze pollution process in Xi'an

In this study, PM_2.5 samples were collected during three haze episodes in Xi’an, China occurring from December, 2019 to January, 2020. Total proteins in PM_2.5 were determined via bicinchoninic acid assay (BCA). Other chemical compositions such as water-soluble ions and dicarboxylic acids were analyzed using ion chromatography (IC) and gas chromatography-mass spectrometry (GC/MS). The correlation analysis combined with backward trajectory model of air mass were then used to examine the response of aerosol proteins to haze pollution process and their potential role in the formation and development of haze pollution. The results showed that the average protein concentration in PM_2.5 was pretty high in Xi’an (about (5.587±2.421)μg/m³) during the winter haze pollution episodes. A time-resolved variation in total proteins was characterized by slightly higher concentration at night than that in daytime. There was a significantly positive correlation between the concentrations of total protein and those of Cl^-and K⁺in PM_2.5, indicating that the sources of aerosol proteins were associated with coal and biomass combustion. The concentrations of NO₃^- and SO₄^2- showed a significant and positive correlation with total proteins, suggesting that the proteins may be involved in the oxidation of NO_x and SO₂. In highly humid conditions, protein aerosols are prone to hygroscopicity growth, and they are also easy to adsorb gaseous pollutants to promote heterogeneous reactions, which may be conducive to the generation of secondary aerosols during haze pollution.