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Veli-Matti Kerminen Risto E. Hillamo Anthony S. Wexler 《Journal of Atmospheric Chemistry》1998,30(3):345-370
A box model was constructed to investigate connections between the particulate MSA to non-sea-salt sulfate ratio, R, and DMS chemistry in a clean marine boundary layer. The simulations demonstrated that R varies widely with particle size, which must be taken into account when interpreting field measurements or comparing them with each other. In addition to DMS gas-phase chemistry, R in the submicron size range was shown to be sensitive to the factors dictating sulfate production via cloud processing, to the removal of SO2 from the boundary layer by dry deposition and sea-salt oxidation, to the entrainment of SO2 from the free troposphere, to the relative concentration of sub- and supermicron particles, and to meteorology. Three potential explanations for the increase of R toward high-latitudes during the summer were found: larger MSA yields from DMS oxidation at high latitudes, larger DMSO yields from DMS oxidation followed by the conversion of DMSO to MSA at high latitudes, or lower ambient H2O2 concentrations at high latitudes leading to less efficient sulfate production in clouds. Possible reasons for the large seasonal amplitude of R at mid and high latitudes include seasonal changes in the partitioning of DMS oxidation to the OH and NO3 initiated pathways, seasonal changes in the concentration of species participating the DMS-OH reaction pathway, or the existence of a SO2 source other than DMS oxidation in the marine boundary layer. Even small anthropogenic perturbations were shown to have a potential to alter the MSA to non-sea-salt sulfate ratio. 相似文献
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On the formation and growth of atmospheric nanoparticles 总被引：2，自引：0，他引：2
In this paper we summarize recent experimental, theoretical and observational results on the formation and growth of atmospheric nanoparticles. During the last years significant progress has occurred to explain atmospheric nucleation and initial steps of the growth. Due to climatic and health effects of fine and ultrafine particles the formation and growth of new aerosol particles is of growing interest. The question “How and under which conditions does the formation of new atmospheric aerosol particles take place?” has exercised the minds of scientists since the time of John Aitken, who in the late 1880s built the first apparatus to measure the number of dust and fog particles. However, only during the last 15–20 years has the measurement technology developed to such a level that size distributions of nanometer-size particles and concentrations of gases participating in particle formation can be measured in the atmosphere. Also from a theoretical point of view atmospheric nucleation mechanisms have not been resolved: several mechanisms such as ion-induced (or ion mediated) nucleation, ternary and kinetic (barrier-less) nucleation have been suggested. In the most recent theory, the activation of existing neutral and/or ion clusters has been suggested. 相似文献
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Distribution of nitrate over sea-salt and soil derived particles — Implications from a field study 总被引：1，自引：0，他引：1
Tuomo A. Pakkanen Veli-Matti Kerminen Risto E. Hillamo Minna Màkinen Timo Màkelà Aki Virkkula 《Journal of Atmospheric Chemistry》1996,24(2):189-205
A method for determining the distribution of supermicrometer nitrate between size-segregated sea-salt and soil derived particles is presented. The analysis is based on field data from six measurements at a coastal site in southern Finland, and on a theoretical treatment taking into account the transfer of gaseous species onto particle surfaces and their subsequent reaction. Significant amounts of nitrate were found in both the particle types, with the fraction of nitrate associated with soil particles varying from 20–50% in the 1–2 m size to near 90% in particles larger than 10 m. Overall, the nitrate accumulation followed closely the relative abundances of these two particle types. Two overlapping modes in supermicron nitrate mass size distributions could be identified. The lower mode, associated with sea-salt, was located between the surface-area and volume distribution of sodium peaking at about 2–3 m of EAD. The upper mode peaked at 3–5 m and followed more closely the surface-area distribution of calcium in all samples. At our site, the accumulation of nitrate into both particle types was shown to be limited by an effective surface reaction rate rather than by gas-phase diffusion. This rate was estimated to be considerably larger for sea-salt particles. Strong evidence in support of the saturation of nitrate in sea-salt particles were obtained. 相似文献
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Petri?NummiEmail author Veli-Matti?V??n?nen Martti?Rask Kari?Nyberg Keijo?Taskinen 《Aquatic Sciences - Research Across Boundaries》2012,74(2):343-350
We determined the associations between Eurasian perch Perca fluviatilis, invertebrates, and common goldeneye Bucephala clangula in boreal lakes. Our aim was to test the hypothesis that perch play a controlling role in small, oligotrophic, acidic, and
poorly vegetated boreal lakes, affecting both invertebrate numbers and community structure. In addition, we predicted that
perch impact lake usage by goldeneye. In the observational part of our study, we first explored the association between perch,
invertebrates and goldeneye (pairs and broods per shore km) in 18 boreal, poorly vegetated lakes. Perch densities were associated
negatively with invertebrate abundance and lake usage by goldeneye broods. In the experimental part in three fish-free lakes,
we found that upon successful perch introductions, the number and biomass of invertebrates, the proportion of large dytiscids,
and lake usage by goldeneye broods significantly decreased. We conclude that perch apparently plays a key role as a predator
of invertebrates in boreal lakes with few aquatic macrophytes. It is evident that perch can strongly affect their prey populations
and communities, and this predation may have an indirect effect on species, e.g. goldeneye, that consume the same prey. 相似文献
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