AEROCLO-sA PEGASUS aerosol particle elemental composition in the TSP fraction

The AEROCLO-sA field campaign took place from 21 August to 13 September 2017 at the Sam Nujoma Marine and Coastal Resources Research Centre (SANUMARC) of the University of Namibia at Henties Bay (Formenti et al., 2019). This sampling site, operated on the long-term as described by Formenti et al. (2018) and Klopper et al. (2020).
During the campaign, aerosol samples in the total suspended particulate (TSP). were collected both during day (approximately 07:00-17:00 UTC) and night time (approximately 17:30-06:30 UTC). The sampling duration was marginally adapted in real-time to the nature and the aerosol load of air masses using the readings of the local wind speed and direction and of the aerosol mass concentration, also measured online. Air sampling was performed from the PortablE Gas and Aerosol Sampling UnitS (PEGASUS; https://pegasus.aeris-data.fr/) facility with two high-volume aerosol inlets delivering approximately 450 L min-1 each. At wind speeds between 5 to 10 m s 1, typical for coastal Namibia, sampling is almost isokinetic for particles up to 40 µm in aerodynamic diameter (Rajot et al., 2008). The total sampled flow rate is distributed to various instruments, including a custom-made filter holder loaded with a polycarbonate membrane (Nuclepore®, 0.4-µm pore size diameter, 37-mm filter diameter) operated at an average sampling flow rate of the order of 20 L min-1.
In total, 36 TSP filter samples (including blanks) were collected between 21 August and 12 September 2017.
The analysis of the elemental concentrations was performed at LISA according to the protocols previously detailed in Klopper et al. (2020) and Desboeufs et al. (2024). The elemental concentrations of 24 elements (Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Sr, Pb, Nd, Cd, Ba) were measured by wavelength-dispersive X-ray fluorescence (WD-XRF) using a PW-2404 spectrometer (Panalytical, Almelo, Netherlands). The instrument was calibrated with mono- and bi-elemental certified elemental standards (Micromatter Inc., Surrey, Canada). The concentrations of light-weight elements (Na to Ca) in the TSP fraction were corrected for X-ray self-attenuation as described in Formenti et al. (2010), assuming a mean diameter of 4.5 µm to represent the average coarse particle size. The measured atmospheric concentrations are expressed in ng m−3, and the relative analytical uncertainty was evaluated as 10 % (see Klopper et al. (2020) for the full description).