长沙市不同污染程度区域桂花和香樟叶表面PM2.5吸附量及其影响因素

为阐释不同污染程度下城市绿化植物吸滞PM_2.5机理、解析污染物来源,应用气溶胶再发生器定量测定长沙市常见的2种园林绿化树种(桂花和香樟)植物叶片PM_2.5吸附量,同时应用原子力显微镜(AFM)观察了不同污染区(交通区、文教区、清洁区)植被的叶表面微形态特征,使用离子色谱仪测定样品中水溶性离子含量.结果表明: 污染程度与植物叶表面PM_2.5吸附量呈正相关,不同植物单位叶面积PM_2.5吸附量全年均值表现为交通区(0.56±0.04 μg·cm^-2)＞文教区(0.48±0.06 μg·cm^-2)＞清洁区(0.33±0.02 μg·cm^-2),植物单位叶面积PM_2.5吸附量季节变化为冬季(0.70±0.10 μg·cm^-2)＞春季(0.43±0.14 μg·cm^-2)＞秋季(0.39±0.12 μg·cm^-2)＞夏季(0.31±0.09 μg·cm^-2),桂花的单位叶面积PM_2.5吸附量大于香樟;污染程度轻的区域的植物叶片比较光滑,污染程度重的区域的叶片较粗糙,植物粗糙度排序为交通区(195.45±16.09 nm)＞文教区(176.99±8.45 nm)＞清洁区(131.88±12.98 nm);不同污染程度地区PM_2.5离子含量均表现为冬季最大,其次是春季和秋季,夏季最低;3个污染区PM_2.5离子成分均以Na⁺、NH₄⁺、Cl^-和Br^-这4种离子为主,不同程度污染区PM_2.5污染均以移动源污染为主.

PM2.5 adsorption capacity of Osmanthus fragrans and Cinnamomum camphora leaf surface and influencing factors under different pollution levels in Changsha,China.

To understand the PM_2.5 adsorption mechanisms of plants under different pollution levels and analyze pollutant sources, the PM_2.5 adsorption amount of the leaves of two garden plant species (Cinnamomum camphora and Osmanthus fragrans) in different polluted level area (traffic area, culture and education area, cleaning area) of Changsha was measured using an aerosol generator. AFM scanning was used to obtain leaf surface micromorphological characteristics. Ion chromatography was used to measure the water-soluble ion content. Results showed that amount of PM_2.5 adsorbed by leaves was positively correlated with pollution levels. The annual mean value of PM_2.5adsorbed per leaf area of different plants was traffic area (0.56±0.04 μg·cm^-2) > culture and education are (0.48±0.06 μg·cm^-2) > clearing area (0.33±0.02 μg·cm^-2). The season with amount of PM_2.5adsorbed in leaves from the highest to lowest was winter (0.70±0.10 μg·cm^-2) > spring (0.43±0.14 μg·cm^-2) > autumn (0.39±0.12 μg·cm^-2) > summer (0.31±0.09 μg·cm^-2). Osmanthus fragrans had higher capacity to absorb PM_2.5 than Cinnamomum camphora. Leaves of plants grown in low pollution areas were relatively smooth, whereas those in high pollution areas were rough. The order of leaf roughness in both species from high to low was traffic area (195.45±16.09 nm) > culture and education area (176.99±8.45 nm) > cleaning area (131.88±12.98 nm). The PM_2.5 ionic content was the highest in winter, intermediated in spring and autumn, and the lowest in summer. The PM_2.5 ions mainly included Na⁺, NH₄⁺, Cl^- and Br^- in three pollution areas. PM_2.5 pollution was due to removable source pollution at different pollution levels.