Browsing by Subject "AMBIENT"

Sort by: Order: Results:

Now showing items 1-5 of 5
  • Baranizadeh, Elham; Nieminen, Tuomo; Yli-Juuti, Taina; Kulmala, Markku; Petäjä, Tuukka; Leskinen, Ari; Komppula, Mika; Laaksonen, Ari; Lehtinen, Kari E. J. (2017)
    The formation rates of 3 nm particles were estimated at SMEAR IV, Puijo (Finland), where the continuous measurements extend only down to 7 nm in diameter. We extrapolated the formation rates at 7 nm (J(7)) down to 3 nm (J(3)) based on an approximate solution to the aerosol general dynamic equation, assuming a constant condensational growth rate, a power-law size-dependent scavenging rate, and negligible self-coagulation rate for the nucleation mode particles. To evaluate our method, we first applied it to new particle formation (NPF) events in Hyytiala (Finland), which extend down to 3 nm, and, therefore, J(3) and J(7) can be determined directly from the measured size distribution evolution. The Hyytiala results show that the estimated daily mean J(3) values slightly overestimate the observed mean J(3), but a promising 91% of the estimated J(3) values are within a factor of 2 from the measured ones. However, when considering detailed daily time evolution, the agreement is not as good due to fluctuations in data as well as uncertainties in estimated growth rates, which are required in order to calculate the time lag between formation of 3 and 7 nm particles. At Puijo, the mean J(7) for clear NPF days during April 2007-December 2015 was 0.44 cm(-3) s(-1), while the extrapolated mean J(3) was 0.61 cm(-3) s(-1).
  • Pathak, Harshad; Spah, Alexander; Kim, Kyung Hwan; Tsironi, Ifigeneia; Mariedahl, Daniel; Blanco, Maria; Huotari, Simo; Honkimäki, Veijo; Nilsson, Anders (2019)
    Wide angle x-ray scattering of supercooled water down to 234.8 K was studied using high energy x rays at the European Synchrotron Radiation Facility. The oxygen-oxygen pair distribution function (PDF) was calculated from the scattering pattern out to the 5th peak at an intermolecular distance, r approximate to 11 angstrom. We observe that the 4th peak and the 5th peak in the PDF increase in height upon supercooling. We also observe that the 4th peak position (r(4)) shifts to shorter distances upon supercooling consistent with previous studies, but we see a more rapid change at the lowest temperature. The running oxygen-oxygen coordination number is calculated for 5 different temperatures, and an isosbestic point at r(iso) = 3.31 +/- 0.05 angstrom was found corresponding to a coordination number of 4.39 +/- 0.15. The comparison of the PDF of the coldest water with that of amorphous ice shows distinct differences. We propose that there are 5-member pentamer rings in low density liquid-like structures giving rise to the sharp correlations at r approximate to 9 angstrom and r approximate to 11 angstrom.
  • Lehmkuehler, Felix; Forov, Yury; Buening, Thomas; Sahle, Christoph J.; Steinke, Ingo; Julius, Karin; Buslaps, Thomas; Tolan, Metin; Hakala, Mikko; Sternemann, Christian (2016)
    We studied the structure and energetics of supercooled water by means of X-ray Raman and Compton scattering. Under supercooled conditions down to 255 K, the oxygen K-edge measured by X-ray Raman scattering suggests an increase of tetrahedral order similar to the conventional temperature effect observed in non-supercooled water. Compton profile differences indicate contributions beyond the theoretically predicted temperature effect and provide a deeper insight into local structural changes. These contributions suggest a decrease of the electron mean kinetic energy by 3.3 +/- 0.7 kJ (mol K)(-1) that cannot be modeled within established water models. Our surprising results emphasize the need for water models that capture in detail the intramolecular structural changes and quantum effects to explain this complex liquid.
  • Siponen, Taina; Yli-Tuomi, Tarja; Aurela, Minna; Dufva, Hilkka; Hillamo, Risto; Hirvonen, Maija-Riitta; Huttunen, Kati; Pekkanen, Juha; Pennanen, Arto; Salonen, Iiris; Tiittanen, Pekka; Salonen, Raimo O.; Lanki, Timo (2015)
    Objective To compare short-term effects of fine particles (PM2.5; aerodynamic diameter Methods We followed a panel of 52 ischaemic heart disease patients from 15 November 2005 to 21 April 2006 with clinic visits in every second week in the city of Kotka, Finland, and determined nine inflammatory markers from blood samples. In addition, we monitored outdoor air pollution at a fixed site during the study period and conducted a source apportionment of PM2.5 using the Environmental Protection Agency's model EPA PMF 3.0. We then analysed associations between levels of source-specific PM2.5 and markers of systemic inflammation using linear mixed models. Results We identified five source categories: regional and long-range transport (LRT), traffic, biomass combustion, sea salt, and pulp industry. We found most evidence for the relation of air pollution and inflammation in LRT, traffic and biomass combustion; the most relevant inflammation markers were C-reactive protein, interleukin-12 and myeloperoxidase. Sea salt was not positively associated with any of the inflammatory markers. Conclusions Results suggest that PM2.5 from several sources, such as biomass combustion and traffic, are promoters of systemic inflammation, a risk factor for cardiovascular diseases.
  • Qiu, Hongrui; Hillers, Gregor; Ben-Zion, Yehuda (2020)
    We study temporal changes of seismic velocities associated with the 10 June 2016 M-w 5.2 Borrego Springs earthquake in the San Jacinto fault zone, using nine component Green's function estimates reconstructed from daily cross correlations of ambient noise. The analysed data are recorded by stations in two dense linear arrays, at Dry Wash (DW) and Jackass Flat (JF), crossing the fault surface trace similar to 3 km northwest and southeast of the event epicentre. The two arrays have 9 and 12 stations each with instrument spacing of 25-100 m. Relative velocity changes (delta v/v) are estimated from arrival time changes in the daily correlation coda waveforms compared to a reference stack. The obtained array-average delta v/v time-series exhibit changes associated with the Borrego Springs event, superposed with seasonal variations. The earthquake-related changes are characterized by a rapid coseismic velocity drop followed by a gradual recovery. This is consistently observed at both arrays using time- and frequency-domain delta v/v analyses with data from different components in various frequency bands. Larger changes at lower frequencies imply that the variations are not limited to the near surface material. A decreasing coseismic velocity reduction with coda wave lapse time indicates larger coseismic structural perturbations in the fault zone and near-fault environment compared to the surrounding rock. Observed larger changes at the DW array compared to the JF array possibly reflect the northwestward rupture directivity of the Borrego Springs earthquake.