Evaluation of measurements of light transmission for the determination of black carbon on filters from different station types. (1st February 2019)

• Record Type: Journal Article
• Authors: Greilinger, Marion; Drinovec, Luka; Močnik, Griša; Kasper-Giebl, Anne
• Is Part Of: Atmospheric environment. Volume 198(2019)
• Page Start: 1
• Page End: 11
• Publication Date: 2019-02-01
• Subjects: Black carbon -- Transmissometry -- Mass absorption cross section -- Filter loading effect -- Attenuation -- Quartz fiber filter; Air -- Pollution -- Periodicals; Air -- Pollution -- Meteorological aspects -- Periodicals; 551.51
• DOI: 10.1016/j.atmosenv.2018.10.017
• Languages: English
• ISSNs: 1352-2310

Abstract

Abstract: We compared two approaches (denoted as Virkkula" and "Drinovec" equations) for the determination of black carbon via attenuation measurements with a transmissometer OT-21 (Magee Scientific) on quartz fiber filters from different station types (urban-traffic, rural-background and remote) within the Austrian air monitoring network. First, we evaluated the entire data set to compare the performance of the models in the determination of the loading parameter k and the mass attenuation cross section σ. Then we investigate k and σ for different station types. The data set comprises 299 filters, all representative for 24 h samples collected with High-Volume-Samplers. Mass concentrations ranged from approximately 5-100 μg m −3 and covered all seasons. Both approaches give statistically indistinguishable results of k with values of 1.00*10 −3 ( ±2*10 −4 ) and 0.97*10 −3 ( ±1*10 −4 ), respectively, if the entire data set is evaluated. The "Drinovec" approach gives slightly lower values for σ than "Virkkula" with values of 32.1 m 2 g −1 ( ±1.1 m 2 g −1 ) and 35.3 m 2 g −1 ( ±1.9 m 2 g −1 ). If the data set is restricted to ATN<300 only, no statistically relevant changes are obtained for k and σ using the "Virkkula" equation. Applying the "Drinovec" equation both parameters, k and σ increase when the data set is restricted. The investigation of the different station types yields values of k statistically not different from zero, whereas σ values are different for the respective station types. Highest values of σ = 33.7 m 2 g −1 ( ±1.4 m 2 g −1 ) were observed for the remote, followed by σ = 31.8 m 2 g −1 ( ±0.5 m 2 g −1 ) for the rural-background station and lowest values of σ = 24.4 m 2 g −1 ( ±0.5 m 2 g −1 ) for the urban-traffic stations, possibly reflecting the respective aerosol type. Based on the results for k and σ using either overall values or station type specific values we performed an extensive validation, discussing the application of the transmissometer measurements for a quick, easy and non-destructive quantification of eBC on either fresh sampled or archived filters of different station types. Applying the method for stations not classified as urban, rural or remote a deviation of eBC and EC values up to 23% can be expected. If the station type is known and the respective k and σ values are used this deviation goes down to 10% or lower. This would allow users to obtain long-term time-series going back to times when no on-line instruments were existing, and to obtain these data sets for sites where no on-line instruments are installed even now. Highlights: eBC and EC concentrations deviate less than 10% if station types are considered. Different filter loading effect models were found to be statistically equal. The filter loading parameter k is statistically not different from zero for single station types. σ values decrease from remote to rural-background to urban-traffic aerosols.