南昌市PM_(2.5)中游离氨基酸的浓度、来源与分布特征

Concentration,source and distribution of free amino acids in PM_(2.5) in Nanchang City

于2021年3—4月在南昌市森林地区和城市地区采集大气PM_(2.5)样品,测定其游离氨基酸(Free Amino Acids,FAAs)浓度.结果表明,南昌市森林地区大气气溶胶中总FAAs浓度为0.093~0.885 nmol·m^(-3),平均浓度为(0.451±0.197)nmol·m^(-3);城市地区大气气溶胶中总FAAs浓度为0.393~1.316 nmol·m^(-3),平均浓度为(0.586±0.227)nmol·m^(-3);森林地区FAAs浓度明显低于城市地区.对氨基酸组成占比分析发现,森林与城市地区氨基酸组成相似,最丰富的氨基酸均为Pro,Gly次之,Ala、Val、Leu、Ile为主要氨基酸.城市地区疏水性氨基酸(46.25%)高于森林地区(41.57%),这说明疏水性FAAs可能更适合在城市空气中聚集.通过相关性分析发现,温度对城市地区多个FAA浓度均有显著影响(p<0.05).随着温度的升高,FAAs浓度也升高.O_(3)对城市FAAs有显著影响(r=0.6,p<0.01),表明城市气溶胶中的FAAs可能参与了与O_(3)相关的大气氧化过程.通过后向轨迹分析表明,森林地区FAAs来自2000 m以上的占比高于来自2000 m以下,且有显著性差异(p<0.05),而城市地区FAAs来自2000 m以上和2000 m以下的占比相当.

PM_(2.5)samples were collected in forest and urban areas in Nanchang City in March April 2021 in thisstudy.The concentrations of FAAs(free amino acids)in PM_(2.5)were determined.The results showed that the concentrations of FAAs ranged from 0.093 nmol·m^(-3)to 0.885 nmol·m^(-3)and 0.393~1.316 nmol·m^(-3)in the forest and urban area,respectively.The average concentration of FAAs in PM_(2.5)collected from the forest area((0.451±0.197)nmol·m^(-3))was significantly lower than that in the urban areas((0.586±0.227)nmol·m^(-3))were.The composition of amino acid in the forest and urban was similar.Pro was the most abundant amino acid,followed by Gly,Ala,Val,Leu and Ile.The percentage of hydrophobic amino acids in urban areas(46.25%)were much higher than that in forested areas(41.57%),suggesting that hydrophobic aminoacids prefer to accumulated in urban aerosols.The positive correlation between temperature and FAAs in PM_(2.5)was found in the urban area(p<0.05),indicating temperature had significant influence on FAA concentrations.Moreover,O_(3) positively correlated with FAAs in the urban(r=0.6,p<0.01),indicating that FAAs might participate photochemical reaction process in the urban aerosols.According to the backward trajectory analysis,the concentrations of FAA in forest areas above 2000 m was significantly higher than that of below 2000 m(p<0.05).In urban areas,FAA from above 2000 m and below 2000 m accounted for the same proportion of concentrations.