Particle concentration and flux dynamics in the atmospheric boundary layer as the indicator of formation mechanism

Abstract

We carried out column model simulations to study particle fluxes and deposition and to evaluate different particle formation mechanisms at a boreal forest site in Finland. We show that kinetic nucleation of sulphuric acid cannot be responsible for new particle formation alone as the vertical profile of particle number distribution does not correspond to observations. Instead organic induced nucleation leads to good agreement confirming the relevance of the aerosol formation mechanism including organic compounds emitted by biosphere. <br><br> Simulation of aerosol concentration inside the atmospheric boundary layer during nucleation days shows highly dynamical picture, where particle formation is coupled with chemistry and turbulent transport. We have demonstrated suitability of our turbulent mixing scheme in reproducing most important characteristics of particle dynamics inside the atmospheric boundary layer. Deposition and particle flux simulations show that deposition affects noticeably only the smallest particles at the lowest part of the atmospheric boundary layer

Summertime surface PM<sub>1</sub> aerosol composition and size by source region at the Lampedusa island in the central Mediterranean Sea

“…Although the detected mass of CH3SO2 + is likely due to the condensation of MSA on accumulation mode particles, and considering that the cTof-AMS collection efficiency below ~100 nm is poor, the increasing concentration of CH3SO2 + did coincide with the nucleation events during this period, suggesting a possible nucleation and condensation of marine biogenic vapours. Different studies indicate that NPF events may be triggered by atmospheric mixing processes (Kulmala et al, 2004;Hellmuth, 2006;Lauros et al, 2007;Lauros et al, 2011) due to different phenomena like the enhancement of turbulence in elevated layers (Wehner et al, 2010), the break-up of the nocturnal inversion (Stratmann et al, 2003), or the turbulence associated with the nocturnal low-level jet (Siebert et al, 2007). Furthermore, the intrusion of descending mid-tropospheric air masses in the boundary layer (Pace et al, 2015) has been linked to the occurrence of NPF events and would be consistent with the absence of high concentrations of BC, SO2, vanadium and nickel which could be expected from ship emissions in the boundary layer over the Mediterranean.…”

Modelling new particle formation events in the South African savannah

“…14 In this study we used a further developed version, in which the one-dimensional version of the model SCADIS is used to improve the meteorology scheme. 15 This modification was made to improve the estimates of vertical turbulent fluxes of heat, moisture and scalars.…”

“…From the meteorological model point of view, changes in the gas phase and in particle concentrations appeared instantly after each minute. 15…”

“…37,38 The second nucleation mechanism used in this work assumes the formation of stable critical clusters by collision of sulphuric acid or a molecule containing sulphuric acid and a low volatile organic compound. The nucleation rate J org is calculated in the same way as by Lauros et al 15 :…”

“…The sudden downward peak during the late hours on 7 October was caused by numerical instability in the model 41 . Lauros et al 15 compared the vertical profiles of the model to measurements made by radiosonde soundings, and stated that the model suggested a too high level of stability and too weak mixing. As the sub-continental conditions in Botsalano are very stable, we cannot make the same conclusion without comparison with measurements.…”