Abstract
Abstract. The exact mechanisms for new particle formation (NPF) under different boundary layer conditions are not known yet. One important question is whether amines and sulfuric acid lead to efficient NPF in the atmosphere. Furthermore, it is not clear to what extent highly oxidized organic molecules (HOMs) are involved in NPF. We conducted field measurements at a rural site in central Germany in the proximity of three larger dairy farms to investigate whether there is a connection between NPF and the presence of amines and/or ammonia due to the local emissions from the farms. Comprehensive measurements using a nitrate chemical ionization–atmospheric pressure interface time-of-flight (CI-APi-TOF) mass spectrometer, a proton-transfer-reaction mass spectrometer (PTR-MS), particle counters and differential mobility analyzers (DMAs), as well as measurements of trace gases and meteorological parameters, were performed. We demonstrate here that the nitrate CI-APi-TOF is suitable for sensitive measurements of sulfuric acid, amines, a nitrosamine, ammonia, iodic acid and HOMs. NPF was found to correlate with sulfuric acid, while an anti-correlation with RH, amines and ammonia is observed. The anti-correlation between NPF and amines could be due to the efficient uptake of these compounds by nucleating clusters and small particles. Much higher HOM dimer (C19/C20 compounds) concentrations during the night than during the day indicate that these HOMs do not efficiently self-nucleate as no nighttime NPF is observed. Observed iodic acid probably originates from an iodine-containing reservoir substance, but the iodine signals are very likely too low to have a significant effect on NPF.
Highlights
The formation of new particles from gaseous compounds produces a large fraction of atmospheric aerosol particles (Zhang et al, 2012)
The site was chosen for several reasons: (i) three larger dairy farms are close by, which should possibly enable us to study the effect of amines on new particle formation (NPF); (ii) it can be regarded as typical for a rural or agricultural area in central Europe; (iii) the site is not too far away from the University of Frankfurt, which allowed for the station to be visited for instrument maintenance on a daily basis; and (iv) since we could measure right next to a meteorological station, infrastructure and meteorological data from the DWD could be used
The condensation sink calculated for the loss of sulfuric acid on aerosol particles is shown taking into account the full size distribution
Summary
The formation of new particles from gaseous compounds (nucleation) produces a large fraction of atmospheric aerosol particles (Zhang et al, 2012). While the newly formed particles have diameters between 1 and 2 nm, they can grow and reach larger sizes, which enables them to act as cloud condensation nuclei (CCN, ∼ 50 nm in diameter or larger). The climatic effect of nucleation depends strongly on the survival probability of the newly formed particles, i.e., if they reach CCN size or not. 50 % of the CCN population globally (Merikanto et al, 2009) In addition to their climatic effect, secondary particles can influence human health (Nel, 2005) or reduce visibility, e.g., in megacities (Chang et al, 2009)
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