06 Aug 2021

06 Aug 2021

Review status: this preprint is currently under review for the journal ACP.

Measurement report: Three years of size-resolved eddy-covariance particle number flux measurements in an urban environment

Agnes Straaten and Stephan Weber Agnes Straaten and Stephan Weber
  • Institute of Geoecology, Technische Universität Braunschweig, Braunschweig, 38106, Germany

Abstract. Size-resolved particle number fluxes in the size range 10 nm <  particle diameter (Dp) < 200 nm were measured over a 3-year period (April 2017–March 2020) using the eddy covariance technique at an urban site in Berlin, Germany. The observations indicated the site as a net source of particles with a median total particle number flux of FTNC = 0.86 × 108 m−2 s−1. The turbulent surface-atmosphere exchange of particles was clearly dominated by ultrafine particles (Dp < 100 nm) with a share of 96 % of total particle number flux (FUFP = 0.83 × 108 m−2 s−1).

Annual estimates of median FTNC and FUFP slightly decreased by −9.6 % (−8.9 % for FUFP) from the first to the second observation year and a further −5.9 % (−6.1 % for FUFP) from the second to the third year. The annual variation might be due to different reasons such as variation of flux footprints in the individual years, a slight reduction of traffic intensity in the third year or a progressive transition of the vehicle fleet towards a higher share of low-emission standards or electric drive. Size-resolved measurements illustrated events of bidirectional fluxes, i.e. simultaneous emission and deposition fluxes within the size spectrum, which occurred more often in spring, late summer and autumn than in winter. Multi-year observations of size-resolved particle fluxes proved to be important for deeper understanding of particle exchange processes with the urban surface and the pronounced influence of traffic at this urban site.

Agnes Straaten and Stephan Weber

Status: open (until 03 Oct 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-625', Anonymous Referee #1, 11 Sep 2021 reply

Agnes Straaten and Stephan Weber

Agnes Straaten and Stephan Weber


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Short summary
Cities show high concentrations of ultrafine particles due to multiple emissions sources such as traffic and industry. To analyse turbulent urban surface-atmosphere exchange of particles, we quantified multi-annual size-resolved particle number fluxes in Berlin, Germany. The site was a net source of particles with dominant contribution of traffic-related emission, especially very small particles < 30 nm. Particle fluxes clearly varied as a function of anthropogenic activity and urban land-use.