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  4. Sampling strategies and post-processing methods for increasing the time resolution of organic aerosol measurements requiring long sample-collection times
 
research article

Sampling strategies and post-processing methods for increasing the time resolution of organic aerosol measurements requiring long sample-collection times

Modini, Rob L.  
•
Takahama, Satoshi  
July 28, 2016
Atmospheric Measurement Techniques

The composition and properties of atmospheric organic aerosols (OAs) change on timescales of minutes to hours. However, some important OA characterization techniques typically require greater than a few hours of sample-collection time (e.g., Fourier transform infrared (FTIR) spectroscopy). In this study we have performed numerical modeling to investigate and compare sample-collection strategies and post-processing methods for increasing the time resolution of OA measurements requiring long sample-collection times. Specifically, we modeled the measurement of hydrocarbon-like OA (HOA) and oxygenated OA (OOA) concentrations at a polluted urban site in Mexico City, and investigated how to construct hourly resolved time series from samples collected for 4, 6, and 8 h. We modeled two sampling strategies - sequential and staggered sampling - and a range of post-processing methods including interpolation and deconvolution. The results indicated that relative to the more sophisticated and costly staggered sampling methods, linear interpolation between sequential measurements is a surprisingly effective method for increasing time resolution. Additional error can be added to a time series constructed in this manner if a suboptimal sequential sampling schedule is chosen. Staggering measurements is one way to avoid this effect. There is little to be gained from deconvolving staggered measurements, except at very low values of random measurement error (< 5 %). Assuming 20% random measurement error, one can expect average recovery errors of 1.33-2.81 mu g m(-3) when using 4-8 h-long sequential and staggered samples to measure time series of concentration values ranging from 0.13-29.16 mu g m(-3). For 4 h samples, 19-47% of this total error can be attributed to the process of increasing time resolution alone, depending on the method used, meaning that measurement precision would only be improved by 0.30-0.75 mu g m(-3) if samples could be collected over 1 h instead of 4 h. Devising a suitable sampling strategy and post-processing method is a good approach for increasing the time resolution of measurements requiring long sample-collection times.

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Type
research article
DOI
10.5194/amt-9-3337-2016
Web of Science ID

WOS:000381094100024

Author(s)
Modini, Rob L.  
Takahama, Satoshi  
Date Issued

2016-07-28

Publisher

Copernicus GmbH

Published in
Atmospheric Measurement Techniques
Volume

9

Issue

7

Start page

3337

End page

3354

Note

This article is licensed under a Creative Commons Attribution 4.0 International License

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
APRL  
Available on Infoscience
October 18, 2016
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/130075
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