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Kauhaniemi M.,Finnish Meteorological Institute | Kukkonen J.,Finnish Meteorological Institute | Harkonen J.,Finnish Meteorological Institute | Nikmo J.,Finnish Meteorological Institute | And 6 more authors.
Atmospheric Environment | Year: 2011

We have slightly refined, evaluated and tested a mathematical model for predicting the vehicular suspension emissions of PM10. The model describes particulate matter generated by the wear of road pavement, traction sand, and the processes that control the suspension of road dust particles into the air. However, the model does not address the emissions from the wear of vehicle components. The performance of this suspension emission model has been evaluated in combination with the street canyon dispersion model OSPM. We used data from a measurement campaign that was conducted in the street canyon Runeberg Street in Helsinki from 8 January to 2 May, 2004. The model reproduced fairly well the seasonal variation of the PM10 concentrations, also during the time periods, when studded tyres and anti-skid treatments were commonly in use. For instance, the index of agreement (IA) was 0.83 for the time series of the hourly predicted and observed concentrations of PM10. The predictions of the model were found to be sensitive to precipitation and street traction sanding. The main uncertainties in the predictions are probably caused by (i) the cleaning processes of the streets, which are currently not included in the model, (ii) the uncertainties in the estimation of the sanding days, and (iii) the uncertainties in the evaluation of precipitation. This study provides more confidence that this model could potentially be a valuable tool of assessment to evaluate and forecast the suspension PM10 emissions worldwide. However, a further evaluation of the model is needed against other datasets in various vehicle fleet, speed and climatic conditions. © 2011 Elsevier Ltd.

Talvitie J.,Aalto University | Heinonen M.,Helsinki Region Environmental Services Authority HSY | Paakkonen J.-P.,City of Helsinki Environment Center | Vahtera E.,City of Helsinki Environment Center | And 3 more authors.
Water Science and Technology | Year: 2015

This study on the removal of microplastics during different wastewater treatment unit processes was carried out at Viikinmäki wastewater treatment plant (WWTP). The amount of microplastics in the influent was high, but it decreased significantly during the treatment process. The major part of the fibres were removed already in primary sedimentation whereas synthetic particles settled mostly in secondary sedimentation. Biological filtration further improved the removal. A proportion of the microplastic load also passed the treatment and was found in the effluent, entering the receiving water body. After the treatment process, an average of 4.9 (±1.4) fibres and 8.6 (±2.5) particles were found per litre of wastewater. The total textile fibre concentration in the samples collected from the surface waters in the Helsinki archipelago varied between 0.01 and 0.65 fibres per litre, while the synthetic particle concentration varied between 0.5 and 9.4 particles per litre. The average fibre concentration was 25 times higher and the particle concentration was three times higher in the effluent compared to the receiving body of water. This indicates that WWTPs may operate as a route for microplastics entering the sea. © IWA Publishing 2015.

Kerminen V.-M.,Finnish Meteorological Institute | Kerminen V.-M.,University of Helsinki | Niemi J.V.,Helsinki Region Environmental Services Authority HSY | Niemi J.V.,University of Helsinki | And 12 more authors.
Atmospheric Chemistry and Physics | Year: 2011

The volcanic eruption of Grimsvötn in Iceland in May 2011 affected surface-layer air quality at several locations in Northern Europe. In Helsinki, Finland, the main pollution episode lasted for more than 8 h around the noon of 25 May. We characterized this episode by relying on detailed physical, chemical and optical aerosol measurements. The analysis was aided by air mass trajectory calculations, satellite measurements, and dispersion model simulations. During the episode, volcanic ash particles were present at sizes from less than 0.5 μm up to sizes >10 μm. The mass mean diameter of ash particles was a few μm in the Helsinki area, and the ash enhanced PM10 mass concentrations up to several tens of μg m -3. Individual particle analysis showed that some ash particles appeared almost non-reacted during the atmospheric transportation, while most of them were mixed with sea salt or other type of particulate matter. Also sulfate of volcanic origin appeared to have been transported to our measurement site, but its contribution to the aerosol mass was minor due the separation of ash-particle and sulfur dioxide plumes shortly after the eruption. The volcanic material had very little effect on PM 1 mass concentrations or sub-micron particle number size distributions in the Helsinki area. The aerosol scattering coefficient was increased and visibility was slightly decreased during the episode, but in general changes in aerosol optical properties due to volcanic aerosols seem to be difficult to be distinguished from those induced by other pollutants present in a continental boundary layer. The case investigated here demonstrates clearly the power of combining surface aerosol measurements, dispersion model simulations and satellite measurements in analyzing surface air pollution episodes caused by volcanic eruptions. None of these three approaches alone would be sufficient to forecast, or even to unambiguously identify, such episodes. © 2011 Author(s).

Dos Santos-Juusela V.,University of Helsinki | Petaja T.,University of Helsinki | Kousa A.,Helsinki Region Environmental Services Authority HSY | Hameri K.,University of Helsinki | Hameri K.,Finnish Institute of Occupational Health
Atmospheric Environment | Year: 2013

To estimate spatial-temporal variations of ultrafine particles (UFP) in Helsinki, we measured particle total number concentrations (PNC) continuously in a busy street and an urban background site for six months, using condensation particle counters (CPC). We also evaluated the effects of temperature, wind speed and wind direction on PNC, as well as the correlation between PNC and PM2.5, PM10 and black carbon (BC) at the street. We found that on weekdays, hourly median PNC were highly correlated with BC (r=0.88), moderately correlated with PM2.5 (r=0.59) and weakly correlated with PM10 (r=0.22). Number concentrations at the street were inversely proportional to temperature and wind speed, and highly dependent on wind direction. The highest PNC occurred during northeastern winds while the lowest occurred during southwestern winds. As these wind directions are nearly perpendicular to the street axis, the formation of wind vortices may have influenced the dispersion of UFP in the site. Although the temporal correlation for PNC was moderately high between the sites (r=0.71), the median concentration at the street was 3 times higher than the urban background levels. The results indicate that people living or passing by the busy street are exposed to UFP concentrations well above the urban background levels. Thus, the study suggests that urban microenvironments should be considered in epidemiological studies. In addition the results emphasize that regulations based solely on PM2.5 and PM10 concentrations may be insufficient for preventing the adverse health effects of airborne particles. © 2013 Elsevier Ltd.

Saarnio K.,Finnish Meteorological Institute | Frey A.,Finnish Meteorological Institute | Niemi J.V.,Helsinki Region Environmental Services Authority HSY | Niemi J.V.,University of Helsinki | And 10 more authors.
Journal of Aerosol Science | Year: 2014

Globally more than a quarter of the total primary energy supply is based on coal combustion. The emissions of coal-fired power plants (CFPPs) are regulated in many industrialized countries and therefore power plants use cleaning techniques to minimize emissions such as sulfur dioxide (SO2) and particles. In this study, the particulate emissions from coal combustion were investigated at a CFPP (506MW) used for combined heat and power production in Helsinki, Finland. Fine particle samples (PM1) were collected after electrostatic precipitator before the desulfurization plant (DSP), including flue gas desulfurization unit (FGD) and baghouse filters, and simultaneously in the smokestack to study the influence of DSP to particulate mass and chemistry. The DSP removed over 97% of particle mass in flue gas. Trace metals were removed efficiently but contribution of some ionic compounds increased in the FGD process. The particle properties were studied in more detail in the smokestack including particle size distribution measurements and size-segregating sampling to study chemical composition and morphology of particles. The particulate emissions from the CFPP were relatively small, consisting mainly of products and reagents of the FGD process (e.g., CaSO4, NaCl) and partly of the primary emissions from the coal combustion (e.g., mineral ash and reaction products of gas phase components). The maximum in particle volume was detected at 0.68μm. PM1 contributed on average 62 ± 5% to PM10 mass. Besides particulate matter, also the gas-phase emission of mercury was studied because coal combustion is one of the major sources of mercury found in the environment. The mercury emissions were within the proposed limits in the EU. © 2014 Elsevier Ltd.

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