Abstract
Abstract. This paper presents a new sampling head design and the method used to evaluate it. The elemental composition of aerosols collected by two different sampling devices in a semi-arid region of Tunisia is compared by means of compositional perturbation vectors and biplots. This set of underused mathematical tools belongs to a family of statistics created specifically to deal with compositional data. The two sampling devices operate at a flow rate in the range of 1 m3 h−1, with a cut-off diameter of 10 µm. The first device is a low-cost laboratory-made system, where the largest particles are removed by gravitational settling in a vertical tube. This new system will be compared to the second device, a brand-new standard commercial PM10 sampling head, where size segregation is achieved by particle impaction on a metal surface. A total of 44 elements (including rare earth elements, REEs, together with Al, As, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Rb, S, Sc, Se, Sr, Ti, Tl, U, V, Zn, and Zr) were analysed in 16 paired samples, collected during a 2-week field campaign in Tunisian dry lands, close to source areas, with high levels of large particles. The contrasting meteorological conditions encountered during the field campaign allowed a broad range of aerosol compositions to be collected, with very different aerosol mass concentrations. The compositional data analysis (CoDA) tools show that no compositional differences were observed between samples collected simultaneously by the two devices. The mass concentration of the particles collected was estimated through chemical analysis. Results for the two sampling devices were very similar to those obtained from an online aerosol weighing system, TEOM (tapered element oscillating microbalance), installed next to them. These results suggest that the commercial PM10 impactor head can therefore be replaced by the decanter, without any measurable bias, for the determination of chemical composition and for further assessment of PM10 concentrations in source regions.
Highlights
At a global scale, mineral dust or mineral aerosols could represent about 40 % of the total amount of particles injected into the atmosphere each year (Boucher et al, 2013; Huneeus et al, 2011)
Atmospheric aerosol loading presented a large range of values, from 21 to 679 μg m−3 (Table 1, The coherence between direct measurement of masses (TEOM) values), with great variations between marine vs. crustal proportions in any given sample pair
The main advantage of this new PM10 inlet is its simple design associated with its low cost and the broad availability of the components, making this new inlet easy to build locally by everyone
Summary
Mineral dust or mineral aerosols could represent about 40 % of the total amount of particles injected into the atmosphere each year (Boucher et al, 2013; Huneeus et al, 2011). Mineral dust is an important source of nutrients neces-. Okin et al, 2011) and for terrestrial plant development Okin et al, 2004). Most of the mineral dust present in the atmosphere comes from West Africa (Prospero and Nees, 1986; N’Tchayi Mbourou et al, 1997), with the Sahara as the main source Accurate measurement of the chemical composition of aerosols is necessary for source tracing in aeolian studies Accurate measurement of the chemical composition of aerosols is necessary for source tracing in aeolian studies (e.g. Scheuvens et al, 2013), which require aerosol data to assess global land degradation and climate change (e.g. Chappell et al, 2018)
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