Showing papers by "Tuukka Petäjä published in 2004"
TL;DR: In this paper, the formation rate of 3-nm particles is often in the range 0.01-10 cm −3 s −1 in the boundary layer in urban areas and in coastal areas and industrial plumes.
2,028 citations
TL;DR: In this paper, the growth properties of nucleation mode aerosols were investigated and the variation of source rates of condensable vapors in different locations and environmental conditions was analyzed, taking advantage of only the measured spectral evolution of aerosol particles as a function of time.
Abstract: . The growth properties of nucleation mode particles were investigated. The variation of source rates of condensable vapors in different locations and environmental conditions was analyzed. The measurements were performed in background stations in Antarctica, in Finnish Lapland and Boreal Forest stations (SMEAR I and SMEAR II) as well as in polluted urban sites in Athens, Marseille and New Delhi. Taking advantage of only the measured spectral evolution of aerosol particles as a function of time the formation and growth properties of nucleation mode aerosols were evaluated. The diameter growth-rate and condensation sink were obtained from the measured size distribution dynamics. Using this growth rate and condensation sink, the concentration of condensable vapors and their source rate were estimated. The growth rates and condensation sinks ranged between 0.3-20nmh-1 and 10-4-0.07s-1, respectively. The corresponding source rate of condensable vapors varied more than 4 orders of magnitude from 103 to over 107cm-1s-1. The highest condensation sink and source rate values were observed in New Delhi and the smallest values in Antarctica.
196 citations
TL;DR: In this paper, the average ion production rate calculated from aerosol particle size distribution and air ion mobility distribution measurements was 2.6 ion pairs cm-3s-1, and based on external radiation and radon measurements, 4.5 ion pairscm-3 s-1.
Abstract: . In this study the ion production rates in a boreal forest were studied based on two different methods: 1) cluster ion and particle concentration measurements, 2) external radiation and radon concentration measurements. Both methods produced reasonable estimates for ion production rates. The average ion production rate calculated from aerosol particle size distribution and air ion mobility distribution measurements was 2.6 ion pairs cm-3s-1, and based on external radiation and radon measurements, 4.5 ion pairs cm-3s-1. The first method based on ion and particle measurements gave lower values for the ion production rates especially during the day. A possible reason for this is that particle measurements started only from 3nm, so the sink of small ions during the nucleation events was underestimated. It may also be possible that the hygroscopic growth factors of aerosol particles were underestimated. Another reason for the discrepancy is the nucleation mechanism itself. If the ions are somehow present in the nucleation process, there could have been an additional ion sink during the nucleation days.
140 citations
TL;DR: In this paper, differences in the hygroscopic and ethanol uptake properties of ultrafine aerosol particles in the Arctic air masses with a different exposure to anthropogenic sulfur pollution were examined.
Abstract: . Hygroscopicity (i.e. water vapour affinity) of atmospheric aerosol particles is one of the key factors in defining their impacts on climate. Condensation of sulphuric acid onto less hygroscopic particles is expected to increase their hygrocopicity and hence their cloud condensation nuclei formation potential. In this study, differences in the hygroscopic and ethanol uptake properties of ultrafine aerosol particles in the Arctic air masses with a different exposure to anthropogenic sulfur pollution were examined. The main discovery was that Aitken mode particles having been exposed to polluted air were more hygroscopic and less soluble to ethanol than after transport in clean air. This aging process was attributed to sulphur dioxide oxidation and subsequent condensation during the transport of these particle to our measurement site. The hygroscopicity of nucleation mode aerosol particles, on the other hand, was approximately the same in all the cases, being indicative of a relatively similar chemical composition despite the differences in air mass transport routes. These particles had also been produced closer to the observation site typically 3–8 h prior to sampling. Apparently, these particles did not have an opportunity to accumulate sulphuric acid on their way to the site, but instead their chemical composition (hygroscopicity and ethanol solubility) resembled that of particles produced in the local or semi-regional ambient conditions.
35 citations
TL;DR: In this article, a novel method for the determination of particle formation rates and condensable vapor concentrations for atmospheric nucleation events is presented that is based on combining least squares optimization with aerosol dynamics.
Abstract: [1] A novel method for the determination of particle formation rates and condensable vapor concentrations for atmospheric nucleation events is presented that is based on combining least squares optimization with aerosol dynamics. Tests of the method with simulated events show that the method is able to capture the temporal behavior of formation and growth with reasonable accuracy. Example analyses have been performed for observed particle formation bursts in Hyytiala, Finland. The results agree with previous analyses that are, in principle, based on analyzing size distribution contour plots by eye. However, the presented method also reveals detailed temporal behavior of the important processes, which is an important improvement compared to the previous methods.
19 citations