Impact of biogenic emissions of organic matter from a cool-temperate forest on aerosol optical properties
Impact of biogenic emissions of organic matter from a cool-temperate forest on aerosol optical properties
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DOI：
10.1016/j.atmosenv.2020.117413
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发表时间：
2020-05
影响因子：
5
通讯作者：
Astrid Müller;Kazuma Aoki;E. Tachibana;T. Hiura;Y. Miyazaki
中科院分区：
文献类型：
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作者：
Astrid Müller;Kazuma Aoki;E. Tachibana;T. Hiura;Y. Miyazaki
有机物的陆地生物排放可影响大气气溶胶的光学特性，从而影响辐射收支。为了研究这一点，收集过滤器上的亚微米水溶性气溶胶（WSA）的化学参数进行了比较，在日本北方的冷温带森林网站的天空辐射计测量的光学特性。2015年6月至12月，在林冠层内采集WSA样本，反演林冠层上方气溶胶光学厚度（AOD）、单次散射散射厚度（SSA）、吸收-散射指数（AAE）和散射-散射指数（SAE）。只有当气溶胶粒子从森林冠层到上面的空气的垂直传输是显着的光学特性进行了比较，过滤器为基础的化学参数。结果表明，气溶胶光学厚度与水沙质量浓度具有相似而明显的季节变化规律，其峰值出现在夏季和秋季。夏季，硫酸盐占WSA质量的60%，这与高SSA（>0.95）、低AAE（1.15 ± 0.84）和低SAE（1.25 ± 0.22）有关。秋季水溶性有机质（WSOM）占WSA质量的70%。这一大部分WSOM与SSA（0.90-0.95）降低以及AAE（2.45 ± 0.91）和SAE（1.46 ± 0.15）增加相关。结果表明，在夏季，气溶胶粒子具有较大的尺寸范围对应的气溶胶化学成分占主导地位的硫酸盐。相比之下，在较短波长下具有较强光吸收的较小颗粒在秋季可能很重要，并且与WSOM占主导地位的组合物相关。秋季WSOM的大部分以前与森林地面α-蒎烯的排放和随后形成的生物源次生有机气溶胶（BSOA）有关。这项研究表明，α-蒎烯衍生的SOA，主要来自森林地面，与夏季到秋季的SSA减少。这一过程可以在区域尺度上调节辐射效应。
Terrestrial biogenic emissions of organic matter can affect the optical properties of atmospheric aerosols and thus impact the radiation budget. To investigate this, the chemical parameters of submicrometer water-soluble aerosols (WSA) collected on filters were compared to optical properties measured by a sky radiometer at a cool-temperate forest site in northern Japan. From June to December 2015, the WSA samples were collected within the forest canopy, while aerosol optical depth (AOD), single scattering albedo (SSA), absorption Ångström exponent (AAE), and scattering Ångström exponent (SAE) were retrieved above the canopy. The optical properties were compared with the filter-based chemical parameters only when the vertical transport of aerosol particles from the forest canopy to the air above it was significant. The result showed that the AOD and the mass concentrations of WSA exhibited similar and distinct seasonal variations with peaks in summer and autumn. In summer, sulfate accounted for 60% of the mass of WSA, which was linked to a high SSA (>0.95), low AAE (1.15 ± 0.84), and low SAE (1.25 ± 0.22). In contrast, water-soluble organic matter (WSOM) accounted for 70% of the mass of WSA in autumn. This large fraction of WSOM was associated with a decrease in SSA (0.90–0.95) and an increase in AAE (2.45 ± 0.91) and SAE (1.46 ± 0.15). The results suggest that in summer, aerosol particles with a greater size range corresponded to aerosol chemical compositions dominated by sulfate. In contrast, smaller particles with a strong light absorption at shorter wavelengths, were likely important in autumn and associated with a composition dominated by WSOM. The majority of WSOM in autumn has previously been associated with emissions of α-pinene from the forest floor and the subsequent formation of biogenic secondary organic aerosols (BSOA). This study indicates that α-pinene-derived SOAs, mostly originating from the forest floor, were associated with a summer to autumn decrease in SSA. This process can modulate the radiative effect on a regional scale.