A simple method for correcting for the loading effects of aethalometer data is presented. The formula BC CORRECTED ϭ (1 ϩ k ⅐ ATN) ⅐ BC NONCORRECTED , where ATN is the attenuation and BC is black carbon, was used for correcting aethalometer data obtained from measurements at three different sites: a subway station in Helsinki, an urban background measurement station in Helsinki, and a rural station in Hyytiälä in central Finland. The BC data were compared with simultaneously measured aerosol volume concentrations (V). After the correction algorithm, the BC-to-V ratio remained relatively stable between consequent filter spots, which can be regarded as indirect evidence that the correction algorithm works. The k value calculated from the outdoor sites had a clear seasonal cycle that could be explained by darker aerosol in winter than in summer. When the contribution of BC to the total aerosol volume was high, the k factor was high and vice versa. In winter, the k values at all wavelengths were very close to that obtained from the subway station data. In summer, the k value was wavelength dependent and often negative. When the k value is negative, the noncorrected BC concentrations overestimated the true concentrations.

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 0.3-20 nm h −1 and 10 −4 -0.07 s −1 , respectively. The corresponding source rate of condensable vapors varied more than 4 orders of magnitude from 10 3 to over 10 7 cm −1 s −1 . The highest condensation sink and source rate values were observed in New Delhi and the smallest values in Antarctica.

BackgroundLittle is known of how the toxicity of nanoparticles is affected by the incorporation in complex matrices. We compared the toxic effects of the titanium dioxide nanoparticle UV-Titan L181 (NanoTiO2), pure or embedded in a paint matrix. We also compared the effects of the same paint with and without NanoTiO2.MethodsMice received a single intratracheal instillation of 18, 54 and 162 μg of NanoTiO2 or 54, 162 and 486 μg of the sanding dust from paint with and without NanoTiO2. DNA damage in broncheoalveolar lavage cells and liver, lung inflammation and liver histology were evaluated 1, 3 and 28 days after intratracheal instillation. Printex 90 was included as positive control.ResultsThere was no additive effect of adding NanoTiO2 to paints: Therefore the toxicity of NanoTiO2 was reduced by inclusion into a paint matrix. NanoTiO2 induced inflammation in mice with severity similar to Printex 90. The inflammatory response of NanoTiO2 and Printex 90 correlated with the instilled surface area. None of the materials, except of Printex 90, induced DNA damage in lung lining fluid cells. The highest dose of NanoTiO2 caused DNA damage in hepatic tissue 1 day after intratracheal instillation. Exposure of mice to the dust from paints with and without TiO2 was not associated with hepatic histopathological changes. Exposure to NanoTiO2 or to Printex 90 caused slight histopathological changes in the liver in some of the mice at different time points.ConclusionsPulmonary inflammation and DNA damage and hepatic histopathology were not changed in mice instilled with sanding dust from NanoTiO2 paint compared to paint without NanoTiO2. However, pure NanoTiO2 caused greater inflammation than NanoTiO2 embedded in the paint matrix.

Particle concentrations and size distributions have been measured from different heights inside and above a boreal forest during three BIOFOR campaigns