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Smoke shade as a historic proxy for elemental carbon
Air Quality, Atmosphere & Health ( IF 5.1 ) Pub Date : 2020-11-26 , DOI: 10.1007/s11869-020-00967-8
Harry ten Brink , Regina Hitzenberger

The blackness of aerosol filter samples, meant as a proxy for particulate mass concentration, is the earliest parameter for which monitoring data exist. The smoke shade method (developed in the late 1910s) was the standardised approach to collect samples. The blackness was visually appraised by a comparison with a set of reference sheets covered with an increasing number of layers (shades) of a suspension of carbon black (ink). Samples were assigned a shade number (SN) according to the number of shades of ink on the reference sheet with a corresponding blackness. Automated hourly sampling started in 1921. After World War II, the blackness was measured with a reflectometer and light absorption was translated to the parameter British Smoke (BrS). One unit of SN was equivalent to a specific loading of BrS of 8 μg cm−2. BrS in turn is a proxy for elemental carbon (EC) as we showed in an earlier publication, where we found that a value of BrS of 8 μg cm−2 corresponded to an EC load of 1.4 μg cm−2. SNs can thereby be translated to historic EC loadings/concentrations. In an evaluation of SN-data, we noticed that average pre-war values were mostly at the lower detection limit (one SN) and overestimated because reference sheets faded over time. Data for smog periods with their elevated SNs, however, are quite reliable and can be used for exposure estimates. After World War II, daily sampling resulted in higher filter loadings and reliable average values. Wintertime concentrations corresponding to up to 100 μg m−3 EC were reached. On the other hand, the increased loadings due to the long sampling times resulted in a decrease of the upper limit of detection to an extent that it was exceeded at most of the measuring stations during the “Great Smog” of London in 1952. In this study, we analysed SN data from this episode in depth. At one measuring site, precautions were taken to minimise the loading by using a large filter, but even then the maximum SN was at the upper limit of detection. From a one-to-one relation of BrS and gravimetric mass, established during later smog periods, we deduced that the maximum 2-day mass concentration of EC must have been around 1000 μg m−3. This value is twenty times the new EU-limit for workplace EC exposure (EU 2019) and the 24-h ambient PM10 mass concentration.

中文翻译:

烟罩作为元素碳的历史代表

气溶胶过滤器样品的黑度,作为颗粒质量浓度的代表,是最早存在监测数据的参数。烟幕法(在 1910 年代后期开发)是收集样本的标准化方法。黑度通过与一组覆盖有越来越多的炭黑(油墨)悬浮液的层(色调)的参考片材进行比较来视觉评价。根据具有相应黑度的参考纸上油墨的色调数为样品分配色调数(SN)。自动每小时采样始于 1921 年。二战后,黑度是用反射计测量的,光吸收被转换为参数英国烟雾 (BrS)。一个单位的 SN 相当于特定负载的 8 μg cm-2 BrS。BrS 反过来是元素碳 (EC) 的代表,正如我们在早期出版物中所展示的,我们发现 8 μg cm-2 的 BrS 值对应于 1.4 μg cm-2 的 EC 负载。因此,SN 可以转换为历史 EC 负载/浓度。在对 SN 数据的评估中,我们注意到平均战前值大多处于检测下限(一个 SN)并且由于参考表随着时间的推移而褪色而被高估。然而,具有高 SN 的烟雾时期的数据非常可靠,可用于估计暴露。二战后,每日采样导致更高的过滤器负载和可靠的平均值。达到对应于高达 100 μg m-3 EC 的冬季浓度。另一方面,由于采样时间长而增加的载荷导致检测上限降低到 1952 年伦敦“大雾霾”期间大多数测量站超过的程度。在这项研究中,我们分析了 SN深入了解这一集的数据。在一个测量地点,采取了预防措施,通过使用大过滤器来最小化负载,但即使如此,最大 SN 仍处于检测上限。根据在烟雾后期建立的 BrS 和重量质量的一对一关系,我们推断出 EC 的最大 2 天质量浓度必须在 1000 μg m-3 左右。该值是欧盟新的工作场所 EC 暴露限值(EU 2019)和 24 小时环境 PM10 质量浓度的 20 倍。在这项研究中,我们深入分析了这一集的 SN 数据。在一个测量地点,采取了预防措施,通过使用大过滤器来最小化负载,但即使如此,最大 SN 仍处于检测上限。根据在烟雾后期建立的 BrS 和重量质量的一对一关系,我们推断出 EC 的最大 2 天质量浓度必须在 1000 μg m-3 左右。该值是欧盟新的工作场所 EC 暴露限值(EU 2019)和 24 小时环境 PM10 质量浓度的 20 倍。在这项研究中,我们深入分析了这一集的 SN 数据。在一个测量地点,采取了预防措施,通过使用大过滤器来最小化负载,但即使如此,最大 SN 仍处于检测上限。根据在烟雾后期建立的 BrS 和重量质量的一对一关系,我们推断出 EC 的最大 2 天质量浓度必须在 1000 μg m-3 左右。该值是欧盟新的工作场所 EC 暴露限值(EU 2019)和 24 小时环境 PM10 质量浓度的 20 倍。我们推断出 EC 的最大 2 天质量浓度必须在 1000 μg m-3 左右。该值是欧盟新的工作场所 EC 暴露限值(EU 2019)和 24 小时环境 PM10 质量浓度的 20 倍。我们推断出 EC 的最大 2 天质量浓度必须在 1000 μg m-3 左右。该值是欧盟新的工作场所 EC 暴露限值(EU 2019)和 24 小时环境 PM10 质量浓度的 20 倍。
更新日期:2020-11-26
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