16 Dec 2020

16 Dec 2020

Review status: a revised version of this preprint was accepted for the journal ACP and is expected to appear here in due course.

Increase of secondary organic aerosol over four years in an urban environment

Marta Via1,2, María Cruz Minguillón1, Cristina Reche1, Xavier Querol1, and Andrés Alastuey1 Marta Via et al.
  • 1Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Barcelona, 08034, Spain
  • 2Department of Applied Physics, University of Barcelona, Barcelona, 08028, Spain

Abstract. The evolution of fine aerosol (PM1) species as well as the contribution of potential sources to the total organic aerosol (OA) at an urban background site (Palau Reial, PR, 80 m a.s.l) in the western Mediterranean basin (WMB) was investigated. For this purpose, an aerosol chemical speciation monitor (ACSM) was deployed to acquire real-time measurements for two one-year periods: May 2014–May 2015 (period A) and Sep 2017–Oct 2018 (period B). Total PM1 concentrations showed a slight decrease (from 10.1 to 9.6 µg · m−3 from A to B), although the relative contribution of both inorganic and organic compounds varied significantly.

Regarding inorganic compounds, SO42−, black carbon and NH4+ showed a significant decrease from period A to B, whilst NO3 concentration was found higher in B. Source apportionment revealed OA was 46 % and 70 % of secondary origin (SOA) in periods A and B, respectively. Two oxygenated secondary sources (OOA) were differentiated by their oxidation status (i.e. aging): less-oxidized (LO-OOA) and more-oxidized (MO-OOA). Disregarding winter periods, where LO-OOA production is not favoured, LO-OOA transformation into MO-OOA was found more effective in period B. The highest MO-OOA-to-LO-OOA ratio (1.5) was found in September–October 2018, implying an accumulation effect after the high temperature and solar radiation conditions in the summer season. In addition, SOA was found sensitive to a NOx-polluted ambient and to other pollutants, especially to ozone, which could be enhancing its production specially during afternoon hours. The anthropogenic primary OA sources identified, cooking-like OA (COA), hydrocarbon-like OA (HOA), and biomass burning OA (BBOA), decreased from period A to B in both absolute concentrations and relative contribution (as a whole, 44 % and 40 %, respectively). However, their concentrations and proportion to OA grow rapidly during highly-polluted episodes.

The influence of certain atmospheric episodes on OA sources was also assessed. Both SOA factors seem linked with long and medium-range circulations, especially those coming from inland Europe and the Mediterranean (triggering mainly MO-OOA) and summer breeze-driven regional circulation (triggering mainly LO-OOA). In contrast, POA pollution is enhanced either during air-cleaning episodes or stagnation anticyclonic events.

Marta Via et al.

Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Marta Via et al.

Data sets

BCN_OA_Source_Apportionment_20142015_20172018 Marta Via, María Cruz Minguillón, Cristina Reche, Xavier Querol, and Andrés Alastuey

Marta Via et al.


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Short summary
Atmospheric pollutants have been measured in an urban environment by means of state-of-the-art tecniques allowing to identify the origin and the sources of pollution. Last years are shown to be increasingly dominated by non-directly emitted particulate matter. Gathered knowledge about the sources of atmospheric pollutants is mandatory to design effective mitigation policies.