Differences in aerosol absorption Angstrom exponents between correction algorithms for a particle soot absorption photometer measured on the South African Highveld
Differences in aerosol absorption Angstrom exponents between correction algorithms for a particle soot absorption photometer measured on the South African Highveld
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DOI：
10.5194/amt-7-4285-2014
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发表时间：
2014-01-01
影响因子：
3.8
通讯作者：
Laakso, L.
中科院分区：
文献类型：
--
作者：
Backman, J.;Virkkula, A.;Laakso, L.
根据基于过滤器的吸收测量计算出的吸收埃指数 (AAE) 通常用于提供有关环境气溶胶来源的信息，例如，区分城市污染和生物质燃烧气溶胶。基于过滤器的吸收测量被广泛使用，并且在全球气溶胶监测站中很常见。使用多种校正算法来解决与基于滤波器的吸收技术相关的伪影。在确定气溶胶吸收的绝对量时，这些算法非常重要。然而，这项研究表明，根据这些修正计算出的 AAE 之间存在显着差异。根据所使用的校正，AAE 可能会发生高达 46% 的变化。该研究还强调，当使用相同的数据集时，使用不同校正计算出的 AAE 之间的差异可能会导致关于气溶胶类型的相互矛盾的结论。 AAE 的范围在未校正数据的 1.17 和给出最大值的校正数据的 1.96 之间。此外，该研究表明，某个地点报告的 AAE 取决于改变滤光片的滤光片透射率。在这项工作中，AAE 是根据在南非 Highveld 的 Elandsfontein 使用三波长颗粒烟灰吸收光度计 (PSAP) 测量 23 个月的数据计算得出的。 PSAP 的样气被稀释以延长过滤器更换间隔，延长了 15 倍。稀释校正的 PSAP 与未稀释的多角度吸收光度计 (MAAP) 之间的相关系数为 0.9。因此，研究还表明，PSAP 的适用性可以扩展到不常访问或遭受高污染的偏远地点。
Absorption Angstrom exponents (AAEs) calculated from filter-based absorption measurements are often used to give information on the origin of the ambient aerosol, for example, to distinguish between urban pollution and biomass burning aerosol. Filter-based absorption measurements are widely used and are common at aerosol monitoring stations globally. Several correction algorithms are used to account for artefacts associated with filter-based absorption techniques. These algorithms are of profound importance when determining the absolute amount of absorption by the aerosol. However, this study shows that there are substantial differences between the AAEs calculated from these corrections. Depending on the used correction, AAEs can change by as much as 46 %. The study also highlights that the difference between AAEs calculated using different corrections can lead to conflicting conclusions on the type of aerosol when using the same data set. The AAE ranged between 1.17 for non-corrected data to 1.96 for the correction that gave the greatest values. Furthermore, the study implies that the AAEs reported for a site depend on at which filter transmittance the filter is changed. In this work, the AAEs were calculated from data measured with a three-wavelength particle soot absorption photometer (PSAP) at Elandsfontein on the South African Highveld for 23 months. The sample air of the PSAP was diluted to prolong filter change intervals, by a factor of 15. The correlation coefficient between the dilution-corrected PSAP and a non-diluted Multi-Angle Absorption Photometer (MAAP) was 0.9. Thus, the study also shows that the applicability of the PSAP can be extended to remote sites that are not often visited or suffer from high levels of pollution.